AU2004200303B2 - Microneedle devices and methods of manufacture and use thereof - Google Patents

Description

30/01 '04 14:29 FAX 61 2 9810 8200 F.B. RICE PATENTS oo005 1

AUSTRALIA

Patents Act 1990 GEORGIA TECH RESEARCH CORPORATION COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Microneedle devices and methods of manufacture and use thereof The following statement is a full description of this invention including the best method of performing it known to us:- COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:29 FAX 61 2 9810 8200 F.B. RICE PATENTS Q006 MICRONEEDLE DEVICES AND METHODS OF MANUFACTURE AND USE THEREOF Background of the Invention This invention is generally in the field of devices for the transport of therapeutic or biological molecules across tissue barriers, such as for drug delivery.

Numerous drugs and therapeutic agents have been developed in the battle against disease and illness, However, a frequent limitation of these drugs is their delivery: how to transport drugs across biological barriers in the body the skin, the oral mucosa, the blood-btain barrier), which normally do not transport drugs at inats that are therapeutically useful or optimal.

Drugs are commonly dministered orally as pills or capsules. However, many drugs cannot be effectively delivered in this manner, due to degradation in the gastrointestinal tract and/or elimination by the liver. Moreover, some drugs cannot effectively diffuse across the intestial mucosa. Patient compliance may also be a problem, for example, in therapies requiring that pills be taken at particular intervals over a prolonged time.

Another common technique for delivering drugs across a biological barrier is the use of a needle, such as those used with standard syringes or catheters, to transport drugs across (through) the skin. While ffective for this purpose, needles generally cause pain; local damage to the skin at the site of insertion; bleeding, which increases the risk of disease tranmission; and a wound sufficiently large to be a site of infection. The withdrawal of bodily fluids, such as for diagnostic purposes, using a conventional needle has these same disadvantages. Needle techniques also generally require administration by one trained in its use. The needle technique also is undesirable for long term, controlled continuous drug delivery.

Similarly, current methods of sampling biological fluids are invasive and suffer fiom the same disadvantages. For example, needles are not prefrred for frequent routine use, such as sampling of a diabetic's blood glucose or delivery of insulin, due to the vascular damage caused by repeated punctures. No alternative methodologies are currently in use. Proposed alternatives to the needle require the use of lasers or heat to COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:29 FAX 61 2 9810 8200 F.B. RICE PATENTS 1007 create a hole in the sdn, which is inconvenict, apcnsive, or undesirable for repeated use.

An alternative delivery technique is the lransdenmal patch, which usually relies on diffusion of the drug across the skin. However, this method is not useful for many drugs, due to the poor permeability effective barrier properties) of t skin. The rate of diffusion depends in part on the size and hydrophllicity of the drug molecules and the concentration gradient across the s~atum corneum. Few drug have the necessary physiochemical properties to be effectively delivered through the skin by passive diffusion. Iontophoresis, electroporation, ultrasoud, and beat (so-called active systems) have been used in an.attempt to improve the rate of delivery. While providing varying degrees of enhancement, these techniques are not suitable for all types of drugs, failing to provide the desired level of delivery. In some cases, they are also painful and inconvenient or impractical for continuous controlled drug delivery over a period ofhours or days. Attempts have been made to design alternative devices for active transfer of drugs, or analyte to be measred, through the skin.

For example, U.S. Patent No. 5,879,326 to Godshall t al. and PCT WO 96/37256 by Silicon Mitedevices, Inc. disclose a tansdermal drug delivery apparatus that includes a cutter portion having a plurality of microprotrusions, which have straight sidewalls, extending from a substrate that is in communication with a drug reservoir. In operation, the microprotrusions penetrate the skin until limited by a stop region of the substrate and then ar moved parallel to the skin to create incisions. Because the microprotrusions are drugged across the skin, the device creates a wound sufficiently large to be a site of infection. Channels in the substrate adjacent to the nicrrootrusions allow drug from the reservoir to flow to the skin near the area disrupted by the miroprotrusions. Merely creating a wound, rather than using a needle which conveys drug through an enclosed channel into the site ofadministration, also creates more variability in dosage.

U.S. Patent No. 5,250,023 to Lee et at -discloses a tandermal drug delivery device, which includes a plurality of skin needles having a diameter in the range of 50 to 400 pm. The skin needles are supported in a water-swellable polymer substrate through which a drug solution permeates to contact the surface of the skin. An electric current is 2 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 I applied to the device to open the pathways created by the skin needles, following their withdrawal from the skin upon swelling of the polymer substrate.

PCT WO 93/17754 by Gross et al., discloses another transdermal drug delivery device that includes a housing having a liquid drug into the skin. The tubular elements may be in the form of hollow needles having inner diameters of less than 1 mm and an outer diameter of 1.0 mm.

Whilst each of these devices has potential use, there remains a need for better drug delivery devices, which make smaller incisions, deliver drug with greater efficiency (greater drug delivery per quantity applied) and less variability of drug administration, and/or are easier to use.

It is therefore an aim of the present invention to provide a microneedle device for relatively painless, controlled, safe, convenient transdermal delivery of a variety of drugs.

It is another aim of the present invention to provide a microneedle device for controlled sampling of biological fluids in a minimally-invasive, painless, and convenient manner.

It is still another aim of the present invention to provide a hollow microneedle array for use in delivery or sensing of drugs or biological fluids or molecules.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

Summary of the Invention Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Microneedle devices for transport of molecules, including drugs and biological molecules, across tissue, and methods for manufacturing the devices, are provided.

The microneedle devices permit drug delivery or removal of body fluids at clinically relevant rates across skin or other tissue barriers, with minimal or no damage, pain, or irritation to the tissue. Microneedles can be formed of a variety of materials, including biodegradable or non-biodegradable polymeric materials or metals. In one preferred embodiment, the device includes a means for temporarily securing the microneedle device to the biological barrier to facilitate transport. The device preferably further includes a means for controlling the flow of material through the microneedles.

Representative examples of these means include the use of permeable membranes, fracturable impermeable membranes, valves, and pumps, and electrical means.

In one aspect, the present invention provides a device for transport of molecules or energy across biological barriers comprising: a plurality of hollow or porous microneedles having a length between 100 lm and 1 mm, wherein at least a portion of the shaft of the microneedles has a width between about 1 Am and 200 jm, and a substrate to which the microneedles are attached or integrally formed, wherein the microneedles extend at an angle from a surface of the substrate.

30/01 '04 14:30 FAX 81 2 9810 8200 F.B. RICE CO PATENTS 11009 Methods are provided far making solid, porous, or, prefemrably, hollow microncedles. A preferred method for maldking a micraneedle includes forming a micromold having sidewalls which define the outer surface of the microneedle. The micromold can be formed, for example, by photolithographically defining one or more holas in a substrate or by las r based cutting (either slally orby using ithographic projection), or by using a mold-insert. In a preferred embodiment the method includes electroplating the sidewulls to form the hollow microneedle, and then removing the micromold from the microneedle.

The microneedle device is useful for delivery of fluid material into or across a biological barrier such as skin, wherein the fluid material is delivered from one or more chambers in fluid connection with at least one of the microneedles.

Brief Description Of The Drawings Figure 1 is a side elevational view of a preferred embodiment of the microneedle device inserted into human skin.

Figures 2a-e are side cross-sctional views of a method for making microneedles.

Figures 3a-g are side cross-sectional views of a method for making a hollow microneedle, Figures 4a-d are side cross-sectional views illustrating a preferred method for making hollow microneedles.

Figures Za-d are side cross-sectional views illustating a peferred method for making hollow silicon microtubes.

Figures 6a-e are side cross-sectiocal views illustrating a preferred method for making hollow metal microtabes.

Figures 7a-d are side cross-sectional views illustrating a preferred method for making tapered metal microneedles.

Figures Ba-4 are side cross-sectional views illustrating a method for making tapred mieroeedles using laser-formed molds.

Figures 9a-f are side cross-sectional views illustrating a second method for makidng tapered mieroneedles using laser-formed molds.

Detailed Decription Of Th Invention 1. Biological Barriers 4 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:30 FAX 61 2 9810 8200 F.B. RICE CO. PATENTS 1010 The devices disclosed herein are useftl n tranprt of matrial into or across biological b aiers including the skin (or parts thereof); the blood-brain barrier; mucosal tissue oral, nasal, ocular, vaginal, urthral, gastrointestinal, respiratory); blood vessels; lymphatic vessels; or cell membranes for the introduction of material into the interior of a cell o cells). The biological barriera can be in human or other types of animals, as well as in plants, insects, or other organisms, including bacteria, yeast, fungi, and embryos.

The microneedle devices can be applied to tissue internally with the aid of a catheter or laparoscope. For certain applications, such as for drug delivery to an internal tissue, the devices can be surgically implanted.

The microneedle device disclosed herein is typically applied to skin. The stratum comeum is the outer layer, generally between 10 and 50 cells, or between 10 and 20 pn thick- Unlike other tissue in the body, the stratum cor come ntains "cells" (called keratinocytes) filled with bundles ofcross-linked keratia and keratohyalin surrounded by an extracellular matrix of lipids. It is this structur that is believed to give skin its barrier properties, which prevents therapeutic transdermal administration of many drugs. Below the stratum comeum is the viable epidermis, which is between 50 and 100 pm thick. The viable epidermis contains no blood vessels, and it exchanges metabolites by diffusion to and from the dermis. Beneath the viable epidermis is the dcrmis, which is between 1 and 3 mm thick and contains blood vessels, lymphatics, and nerves.

2. The Micreneedle Device The microneedle devices disclosed herein include a substrate; one or more microneedles; and, optionally, a reservoir for delivery of drugs or collection of analyte, as well as pump(s), sensor(s), and/or microprocessor(s) to control the ineraction of the foregoing.

a Substrate The substrate of the device can be constructed from a variety of materials, including metals, ceramics, semioondu3ors, organics, polymers, and composites. The substrate includes the base to which the micronedles are attached or integrally formed.

A reservoir may also be attached to the substrate.

COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:31 FAX 61 2 9810 8200 F.B. RICE CO. PATENTS ol011 b. hrernacdle The microneedles of the device can be constructed from a variety of materials, including metals, ceramics, semiconductors, orgauics, polymers, and composites.

Preerred materials of construction include pharmaceutical grade stainless steel, gold, titanium, nickel, iron, gold tin, hromium, copper, alloys of these or other metals, silicon, silicon dioxide, and polymers. Representative biodegradable polymers include polymers of hydroxy acids such as lactic acid and glycolic acid polylawtide, polyglyoolide, polylactide-co-glycolide, and copolymers with PEG, polyanhydrides, poly(ortho)estrs, polyurethanes, poly(butyric acid), poly(valeric acid), and poly(lacide-co-caprolactone).

Representative non-biodegradable polymers include polycarbonate, polymethaeryllc acid, ethylenevinyl acetate, polytetrafluoroethylene (TEFLON), and polyesters.

Generally, the microneedles should have the mechanical strength to remain intact for delivery of drugs, or serve as a conduit for the collection of biological fluid, while being inserted into the skin, while remaining in place for up to a number of days, and while being removed. In embodiments where the microneedles are formed of biodegradable polymers, however, this mechanical requirement is less stringent, since the microneedles or tips thereof can break of4, for example in the skin, and will biodegradc.

Nonetheless, even a biodegradable microneedle still needs to remain intact at least long enough for the microneedle to serve its intended purpose its conduit function).

Therefore, biodegradable microneedles can provide an increased level of safety, as compared to nonbiodegradable ones. The microcedles should be sterilizable using standard methods.

The microneedles can be formed of a porous solid, with or without a sealed coating or exterior portion, or hollow. As used herein, the term "porous" means having pores or voids throughout at lest a portion ofth rticroneedle strctre, sufficiently large and sufficiently Intercomnnted to permit passage of fluid and/or solid materials through the microncedle. As used herein, the term "hollow" means having one or more substantially annular bores or channels through the interior of the microneedle structure, having a diameter sufficiently large to permit passage of fluid end/or solid materials through the microneedle. The annular bores may extend throughout all or a portion of the needle lnthe direction of the tip to the base, extending parallel to the direction of the 6 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:31 FAX 61 2 9810 8200 RICE CO. PATENTS [1012 needle or branching or eiting at a side of the needle, as appropriate. A solid or porous microneedle can be hollow. One of skill in the art can select the appropriate porosity and/or bore features required for specfico applications. For example, one can adjust the pore size or bore diameter to permit passage of the particular material to be transported through the micrneedle device.

The microneedles can have straight or tapered shafts. A hollow microneedle that has a substantially unifrnm diameter, which needle does not taper to a point, is referred to herein as a "microtube." As used herein, the term "microneedle" includes both microtubes and tapered needles unless otherwise indicated. In a preferred embodiment, the diameter of the microneedle is greatest at the base end of the microncedle and tapers to a point at the end distal the base. The microneedle can also be fabricated to have a shaft that includes both a straight (untapered) portion and a tapered portion.

The nicroneedles can be formed with shafts that have a circular cross-section in the perpendicular, or the cross-section can be non-circular. For example, the crosssection of the microneedle can be polygonal star-shaped, square, triangular), oblong, or another shape. The shaft can have one or more bores. The cross-sectional dimemsios typically are between about 10 nm and 1 nwm, preferably between 1 micron and 200 microns, and more preferably between 10 and 100 pm. The outer diameter is typically between about 10 pm and about 100 pm, and the inner diameter is typically between about 3 pm and about 80 pm.

The length of the microneedles typically is between about I pn and 1 mm, preferably between 10 microns and 500 microns, and more preferably between 30 and 200 rm. The length is selected for the particular application, accounting for both an inserted and uninserted portion, An aray ofmicmrneedls can include a mixture of microneedles having, for example, various lengths, outer diameters, inner diameters, cross-sectional shapes, and spacings between the microneedles.

The mieroneedles can be oriented perpendicular or at an angle to the substrate.

Preferably, the microneedles are oriented perpendicular to the substrate so that a larger density of rioroneedles per unit area of substrate is provided. An array of micronedles can inolude a mixture of microneedle orientations, heights, or other parameters.

7 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:31 FAX 61 2 9810 8200 F.B. RICE CO. PATENTS 0013 In a preferred embodiment of the device, the substrate and/or microneedles, as well as other components are formed from flexible materials to allow the device to fit the contours of the biological barrier, such as the skin, vessel walls, or the eye, to which the device is applied. A flexible device facilitates more consistent penetration during use, since pentration can be limited by deviations in the attachment surface. For example, the surface of human skin is not fiat due to dennatoglyphic tiny wrinkles) and hair, c. Reservoir The microneedle device may include a reservoir in communication with the microneedles. The reservoir can be ttached to the substrate by any suitable means In a preferred embodiment, the reservoir is attached to the back of the substrate (opposite the microneedles) arouad the periphery, using an adhesive agent glue). A gasket may also be used to facilitate fonation of a fluid-tight seal.

In a preferred embodiment, the reservoir contains drug, for delivery through the microneedles. The reservoir may be a hollow vessel, a porous matrix, or a solid form including drug which is transported theefrom The reservoir can be formed from a variety of materials that are compatible with the drug or biological fluid contained therein. Preferred materials include natural and synthetic polymers, metals, cerenics, semiconductors, organics, and composites.

The microncedle device can include one or a plurality of chambers for storing materials to be delivered. In the embodiment having multiple chambers, each can be in fluid connection with all or a portion of the microneedles of the device array. In one embodiment, at least two chambers are used to separately contain drug a lyophilized drug, such as a vaccine) and an administration vehicle saline) in order to prevent or minimize degradation during storage. Immediately before use, the contents of the chambers are mixed. Mixing can be triggered by any means, including, for example, mechanical disruption puncturing or braking), changing the porosity, or electrochemical degradation of the walls or membranes separating the chambers. In another embodiment, a single device is used to deliver different drugs, which are stored separately in different chambers. In this embodiment, the rate of delivery of each drug can be independently controlled.

8 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:32 FAX 61 2 9810 8200 FB. RICE9 CO. PATENTS I1014 In a preferrd embodiment, the reservoir should be in direct contact with the i oroneedles and have holes through which drug could exit the reservoir and flow into the interior of hollow or porous microneedles. In another preferred embodiment, the reservoir has holes which permit the drug to transport out of the reservoir and onto the kin surface. From there, drug is transported into the skin, either through hollow or porous microneedles, along the sides of solid microneedles, or through pathways created by microneedles in the skin.

d. Tranmort Control Components The microneedle device also must be capable oftransporting material across the barrier at a usefl rate. For example, the microneedle device must be capable of delivering drug across the skin at a rate sufficient to be therapeutically useful. The device may include a housing with microelectronics and other micrmachined structures to control the rate of delivery either according to a preprogrammed schedule or through active interface with the patient, a healtheare professional, or a biosensor. The rate can be controlled by manipulating a vriety of factor, including the characteristics of the drug fonmalation to be deliverd its viscosity, electric chrge, and chemical composition); the dimensions of each microneedle its outer diameter and the rea of porous or hollow openings); the number of micronedles in the device; the application of a driving force a concentration gradient, a voltage gradient, a pressure gradient); and the use of a valve.

The rate also can be controlled by interposing between the drug in the reservoir and the opening(s) at the base end of the microneedle polymeric or other materials selected for their diffusion characteristics. For example, the material composition and layer thickness can be manipulated using methods known in the art to vary the rate of diffusion of the drug of interest through the material, thereby controlling the rate at which the drug flows from the reservoir through the microneedle and into the tissue.

Transportation of molecules through the microneedles can be controlled or monitored using, for example, various combinations of valves, pumps, sensors, actuators, and microprocessors. These component can be produced using standard manufcturing or microfabrication techniques. Actuators that may be useful with the microneedle devices disclosed herein include micropumps, microvalves, and positioners. In a 9 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:32 FAX 61 2 9810 8200 F.B. RICE PATENTS 1@015 prefertd embodiment, a microprocessor is programmed to conrol a pump or valve, thereby controlling the rat of delivery.

Flow ofmolecules through the miaroneedles can occur based on diffusion, capillary action, or can be induced using conventional mechanical pumps or nonmechanical driving fores, such as electroosmosis or electrophoresis, or convection.

For example, n electroosmosis, electrodes are positioned on the biological barrier surface, one or more microneedles, and/or the substrate adjacent the needles, to create a convective flow which carries oppositely charged ionic species and/or neutral molecules toward or into the biological barrier. In a preferred embodiment, the microneedle device is used in combination with another mechanism that enhances the permeability of th biological barier, for example by increasing cell uptake or membrane disnrption, using electric fields, ultrasound, chemical enhancers, vacuum viruse, pH, heat and/or light.

Passage of the microneedles, or drug to be transported via the microneedles, can be manipulated by shaping the microneedle surface, or by selection of the material forming the mioroneedle surface (whioh could be a coating ather than the miaoneedle per se). For example, one or more grooves on the outside surface of the micrneedles can be used to direct the passage of drug, paricularly in a liquid state. Alternatively, the physical surface properties of the microncedle can be manipulated to either promote or inhibit transport of material along the microneedle surface, such as by controlling hydrophilicity or hydrophobicity.

The flow of molecules can be regulated using a wide range of valves or gates.

These valves can be the type that are selectively and repeatedly opened and closed, or they can be single-use types. For example, in a disposable, single-use drug delivery device, a facturable barrier or one-way gate may be installed in the device betwee the reservoir and the opening of the microneedles. When ready to use, the barrier can be broken or gate opened to permit flow through the microneedles. Other valves or gates used in the microneedle devices can be activated thermally, electrochemically, mechanically, or magnetically to selectively initiate, modulate, or stop the flow of molecules through the nedles. In a prefered embodiment, flow is controlled by using a rate-limiting membrane as a "valve." COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:32 FAX 61 2 9810 8200 F.B. RICE CO. PATENTS o1016 The microneedle devices can further include a lowmeter or other means to monitor flow through the microneedles and to coordinate use of the pumps and valves.

e. Sensors Useful sensors may include seso of pressure, temperature, chemicals, and/or electromagnetic fields. Biosensors can be located on the microneedle surface, inside a hollow or porous microneedle, or inside a device in communication with the body tissue via the microneedle (solid, hollow, or porous). These microneedle bosensors can include four classes of principal transducers: potentiometric, amperometric, optical, and physiochemical. An amporametric sensor monitors currents generated when electrons arc exchanged between a biological system and an electrode. Blood glucose sensors frequently are of this type.

The mieroneedle may function as a conduit for fluids, solutes, electric charge, light, or other materials. In one embodiment, hollow microneedles can be filled with a substance, such as a gel, that has a sensing fiotionality associated with it. In an application for sensing based on binding to a substatc or reaction mediated by an enzyme, the substrate or enzyme can be immobilized in the needle interior, which would be especially usful in a porous needle to create an integral needle/sensor.

Wave guides can be incorporated into the microneedle device to direct light to a specific location, or for detection, for example, using means such as a pH dye for color evaluation. Similarly, heat, electricity, light or other energy forms may be precisely transmitted to directly stimulate, damage, or heal a specific tissue or intermidiary tatoo remove for dark skinned persons), or diagnostic purposes, such as measurement of blood glucose based on IR spectra or by chromatographic means, measuring a color change in the presence of immobilized glucose oxidase in combination with an appropriate substrate.

f. Atlachment Featr A collar or flange also can be provided with the device, for example, around the periphery of the substate or the base. It preferably is attached to the device, but alternatively can be formed as an integral part of the substrate, for example by forming microneedles only near the center of an "oveized" substrate. The collar can also emanate from other parts of the device. The collar can provide an interface to attach the 11 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:33 FAX 61 2 9810 8200 F.B. RICE CO. PATENTS I017 miconeedle array to the rest of the device, and can failitate handling of the smaller devices.

In a prefred erabodiment, the micrneedle device includes an adhesive to temporaily secure the device to tih sarface of the biological banier. The adhesive can be essentially anywhere on the device to facilitate contact with the biological barrier. For example, the adhesive can be on the sufce of the collar (same side as microneedles), on the surface of the substrate between the microneedles (near the base of the microneedles), or a combinaton thereof.

g. Trangderma] Microneedle Device Figure 1 is a side elevational view of a schematic of a preferred embodiment of the microneedle device inserted into skin. The device 10 includes an upper portion or substrate 11 flom which a pluality of micneedles 12 protrude. The height of the upper portion 11 is between about 1 pm and 1 cm and the width ofthe upper portion is between about 1 nm and 10 cm. The upper portion 11 of the device can be solid or hollow, and may include multiple compartments. In a preferred embodiment for drug delivery, the upper portion 11 contains one or more drugs to be delivered. It is also preferred that the upper portion include one or more sensors and/or an apparatus pump or electrode) to drive (provide/direct the force) transport of the drug or other molecules.

The height (or length) of the microneedles 12 generally is between about I pm and 1 mm. The diameter and length both affect pain as well as functional properties of the needles. In transdrmal applications, the "insertion depth" of the microneedles 12 is preferably less than about 100 mm, more preferably about 30 um, so that insertion of the micruneedles 12 into the skin through the stratum corneum 14 does not penetrate past the epidermis 16 into the dermis 18 (as described below), thereby avoiding contacting nerves and reducing the potential for causing pain. In such applications, the actual length of the microneedles may be longer, since the portion of the microneedles distal the tip may not be inserted into the skin; the uninserted length depends on the particular device design and configuation. The actual (overall) height or length of microneedles 12 should be equal to the insertion depth plus the uninserted length.

The diameter of each microneedle 12 generally is betwee about 10 nm and 1 mm, and preferably leaves a residual hole (following microneedle insertion and 12 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:33 FAX 61 2 9810 8200 F.B. RICE,& CO.. PATENTS 10018 withdrawal) of less than about 1 pm, to avoid making a hole which would allow bacteria to eater the penetration wound The actual micronedle diameter should be larger than 1 pm since the hole likely will contract fllowing withdrawal of the ioriocedle. The diameter of microneedic 12 more prferably is between about 1 pm and 100 pm. Larger diameter and longer microneedles are acceptable,-so long as the mironeedle can pcuaate the biological barrier to the desired depth and the hole remaining in the skin or other tissue following withdrawal ofthe microncedle is sufficiently small, preferably small enough to exclude bacterial entry. The microneedles 12 can be solid or porons, and can include one or more bores connected to upper portion 11, 3. Methods of Maldmg Microneedle Devices 1The microncedle devices are made by microfabrication processes, by oreating small mechanical strnuctures in silicon, metal, polymer, and other materials. These microfhbrication processes are based on well-established methods used to make integrated circuits, electronic packages and other microelectronic devices, augmented by additional methods used in the field ofmicroncabining. The microneedle devices can have dimensions as small as a few nanomettrs and can be mass-produced at low per-unit costs.

a. Mirofabrication Pracsses Mlroflbrication processes that may be used in making the microncedies disclosed herein include lithography; etching techniques, such as wet chemical, dry, and photoresist removal; thermal oxidation of silicon; electroplating and electroless plating: diffusion processes. such as boron, phosphorus, arsenic, and antimony diffusion; ion implantation, film deposition, such as evaporation (filament electron beam, flash, and shadowing and step coverage) sputtering, chemical vapor deposition (CVDI)), epitaxy (vapor phase, liquid phase, and molecular beam), clectroplating, sreen printing, lamination, stereolithography, laser machining, and laser ablation (including projection ablation). See generally Jaeger, Introduation to Micoeleatronl Fahrication (Addison- Wealey Publishing Co., Reading MA 1988); Runyan, at al., Semiconductor Integrated Circuit Processing Technology (Addison-Wesley Publishing Co., Reading MA 1990); Proceedings of the IEEE Micro Electr Mechanical Systems Conference 1987-1998; Rai- 13 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:33 FAX 61 2 9810 82Q.00t RICE CO. PATENTS 2019 Choudhury, ed., Handbook ofMi hiitaa hY.MiamnmachiTnan Microfabricaltif (SPIE Optical Engineering Press, Bellingham, WA 1997).

The following methods ar preferred for making microneedes.

i. electrochemical etching of sitcon In this method, clectrochomical etching of solid silicon to porous silicon is used to create extremely fine (on the order of 0.01 pm) silicon networks which can be used as piercing structures. This method uses electrolytic anodization of silicon in aqueous hydrofluoric acid, potentially in combination with light, to etch channels into the silicon.

By varying the doping onoektration of the silicon wafer to be etched, the electrolytic .potential during etching, the incident light intensity, and the electrolyte conentration, control over the ultimate pore struture can be achieved. The material not etched the silicon remaining) forms the microneedles. This method has been used to produce irregular needle-type structures measuring tens of nanometers in width.

i. plasma etching This process uses deep plasma etching of silicon to create microneedles with diamnter onthe order of 0.1 Im or larger. Needles are patterned directly using photolithography, rather than indirectly by controlling the voltage (as in electrochemical etching), thus providing greater control over the final microneedle geometry.

In this process, an appropriate masking material metal) is deposited onto a silicon wafer sbstrate and patterned into dots having the diameter of the desired microneedles. The wafer is then subjected to a carefully controlled plasma based on fluorine/oxygen chemistries to etch very deep, high aspect ratio trenches into the silicon.

See, eg., Jansen, et "The Black Silicon Method IV: The Fabrication of Three- Dimensional Structures in Silicon with High Aspect Ratios for Scanning Probe Microscopy and Other Applications," IEEE Proceedings ofMicro Electro Mechanical Systems Conference, pp. 88-93 (1995). Those regions protected by the metal mask remain and form the needles. This method is further described in Example I below.

iii. eletroplating In this process, a metal layer is first evaporated onto a planar substrate. A layer of photoresist is then deposited onto the metal to form a patterned mold which leaves an exposed-metal region in the shape of needles. By electroplating onto the exposed regions 14 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:34 FAX 61 2 9810 8200 RICE CO. PATENTS of the metal seed layer, the mold bounded by photoreaist can be filled with electroplated material. Finally, the substrate and photoresist mold ar removed, leaving the finished micrneedle array. The microneedles produced by this process generally have diameters on the order of 1 pm or larger. Seae, Fmzier, et ol., "Two dimensional metallic microelectrode arays for extracellulr stimulation and recording of neurons", IEEE Proceedings of the Micro Electro Mechanical Systems Conference, pp. 195-200 (1993), iv. ther process Another method for forming micrmnedles made of silicon or other materials is to use microfabricatlon techniques such as photolithography, plasma etching, or laser .ablation to make a mold form transferring that mold form to other materials using standard mold transfer techniques, such as embossing or iqjection molding and reproducing the shape of the original mold form using the newly-created mold to yield the final microneedles Alternatively, the creation ofthe mold form could be skipped and the mold could be microfabricated directy, which could then be used to create the final microneedles Another iethod of forming solid silicon microneedles is by using epitaxial growth on silicon substrates, as is utilized by Containerless Research, Inc. (Evanston, Illinois, USA) for its products.

b. Hollow or Porous Microneedes In a preferred embodiment, microneedles are made with pores or other pathways through which material may be transported. The following descriptions outline rpresentative methods for fabricating either porous or hollow microneedles.

L porous microneedes Rather than having a single, well-defined hole down the length of the needle, porous needles are filled with a network of channels or pores which allow conduction of fluid or eergy through the needle shaft. It has been shown that by appropriate electrochemical oxidation of silicon, pore arrays with high aspect ratios and a range of different pore siz regimes can be formed; these pore regimes are defined as (1) microporous regime with average pore dimensions less than 2 an, mesoporous regime with average pore sizes of between 2 nm and 50 nm, and macroporou regime with pores greater than 50 m. The mesoporous and maroporous regimes are expected to be COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:34 'AI LLI2 980 8200 F,B. RICE CO. 4 PATENTS a0121 most usef for drg delivery. Two approaches to pornus needles are generally available, either the silicon wafer Is first made porous and then etched as described above to form needles or solid micncedles ae etched and then rendered porous, for example, by means of eleetrochemical oxidaltion. such as by anodization of a silicon substrate in a hydrofluoric acid electrolyte. The size distribution of the etched porous structure is highly dependent on several variables, including doping kldnd and illumination conditions, as detailed In Lehmann, "Prous Silicoan-A New Material for MEMS", IEEE Proceedings of the Mcro Eleciro Mechanical Systems Cofrence, pp. 1-6 (1996).

Porous polymer or metallic microneedles can be formed, for example, by micromolding a polymer containing a volatilizable or leachable material such as a volatile salt, dispersed in the polymer or metal, and then volatilizing or leaching the dispersed material, leaving a porous polymer matrix in the shape of the microneedle.

ii. hollow need/es Three-dimensional arrays of hollow microneedles can be flbricated, for example, using combinations of dry etching processes (Learmer, at al, "Bosch Deep Silicon Etching: Improving Uniformity and Etch Rate for Advanced MEMS Applications," Micro Electro Mechanical Systems, Orlando, FL USA, (Jan. 17-21, 1999); Despont at al., "High-Aspect-Ratio, Ultrathick, Negative-Tone Near-UV Photoresist for MEMS", Proc oflEEE IO Annual International Workshop on MEAS, Nagoya, Japan, pp. 51 8-522 (Jan.

26-30, 1997)); micromold creation in lithograpbieally-defined andlor laser ablated polymers and selective sidewall electroplating; or direct micromolding techniques using epoxy mold ramufoir.

One or more distinct and continuous pathways are created through the interior of anicronedles. In a preferred embodiment, the micronsdle has a single annular pathway along the center axis of the microncedle. This pathway can be achieved by initially chemically or physically etching the holes in the material and then etching away microneedles around the hole. Alternatively, the microncedles and their holes can be made simnultneously or holes can be etched into existing microeedles. As another option, a microncedle form or mold can be made, then coated, and thn etched away, leaving only the outer coating to form a hollow micronedle. Coatings can be fonned either by deposition of a film or by oxidation ofthe silicon microneedles to a specific 16 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:34 FAX 61 2 9810 8200 F.B. RICE CO.

4, PATENTS IM022 thickmess, followed by removal of te interior silicon. Also, holes fom the backside of the wafer to the underside of the hollow needles can be created using a front-to-backside infiard alignment followed by etching fro the backside of the wafer.

a. silicon micronedles One method for hollow needle fabrication is to replace the solid mask used in the formation of solid needles by a mask that includes a solid shape with one or more interior regions of the solid shape removed. One example is a "donut-shaped" mask. Using this type of mask interior regions of the needle are etched simultaneously with their side walls, Due to lateral etching of the inner side walls of the needle, this may not produce .sufficiently sharp walls. In that case, two plasma etches may be used, one to form the outer walls of the microneedle the 'standard' etch), and one to form the inner hollow coe (which is an extremely anisotropic etch, such as in inductivoly-coupled-plasma "ICP" etch). For example, the ICP etch can be used to form the interior region of the needle followed by a second photolithography step and a standard etch to form the outer walls of the microneedle. Figure 2a represents a silicon wafer 82 with a patterned photaresist layer 84 on top of the wafer 82. The wafer 82 is anisotropically etched (Figure 2b) to form a cavity 86 through its entire thickness (Figure 2c). The wafer 82 is then coated with a chromium layer 88 followed by a second photoresist layer 90 patterned so as to cover the cavity 86 and form a circular mask for subsequent etching (Figure 2d).

The wafer 82 is then etched by a standard etch to form the outer tapered walls 92 of the microneedle (Figure 2e).

Alternatively, this structura can be achieved by substituting the chromium mask used for the solid microncedles described in Example 1 by a silicon nitride layer 94 on the silicon substrate 95 covered with chromium 96, deposited as shown in Figure 3a and patterned as shown in Figure 3b- Solid microneedles are then etched as described in Example 1 as shown Figure 3c, the chromium 96 is stipped (Figue 3d), and the silicon is oxidized to form a thin layer of silicon dioxide 97 on all exposed silicon surfaces (Figure 3e). The silicon nitride layer 94 prevents oxidation at the needle tip. The silicon nitride 94 is then s ipped (Figure 3f), leaving exposed silicon at the tip of the needle and oxido-covered silicon 97 eveiywhere else. The needle is then exposed to an ICP plasma 17 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 3j/Q1 1.4:35 FAX 61 2 9810 8200 F.B. RICE CO, PATENTS lG1023 which selectively etches the inner sidewalls of the silicon 95 in a highly anistropic manner to form the inteior hole of the needle (Figure 3g), Another method uses the solid silicon needles described previously as fTons' around which the actual needle structures are deposited. After deposition, the forms are etched away, yielding the hollow structures. Silica needles or metal needles can be formed using different methods. Silica needles can be formed by creating needle structures similar to the ICP needles described above prior to the oxidation described above. The wafers are then oxidized to a controlled thicknss, forming a layer on the shaft ofthe needle form which will eventually become the hollow microncedle. The silicoo nitride is then stripped and the silicon core selectively etched away in a wet alkaline solution) to form a hollow silica microncedle.

In a preferred embodiment, an array of hollow silicon micrtubes is made using deep reactive ion etching combined with a modified black silicon process in a conventional reactive ion etcher, as desmribed in Example 3 below. Firut, anays of circular holes are patterned through photoremist into SiOz, such as on a silicon wafer.

Then the silicon can be etched using deep reactive ion etching (DRIE) in an inductively coupled plasma (ICP) reactor to etch deep vertical holes. The photoresist was then removed. Next, a second photolithography step patterns the remaining SiO layer into circles concentric to the holes, leaving ring shaped oxide masks surrounding the holes.

The photoresist Is then removed and the silicon wafer again deep silicon etched, such that the holes are etched completely through the wafer (inside the SiO2 ring) and simultaneously the silicon is etched around the SiO 2 ring leaving a cylinder.

This latter process can be varied to produce hollow, tapred micronecdles. After an array of hole is fabricated as described above the photoresist and SiO 2 layers are replaced with confonal DC sputtered chromium rings. The second ICP etch is replaced with a SFdO 2 plasma etch in a reactive ion etcher which results in positively sloping outer sidewalls. Henry, et al., "Micomachined Needles for the Trandaderal Delivery of Drugs," Micro Elearo Mechanical Systems, Heidelber, Germany, pp. 494- 498 (Jan. 26-29,1998).

18 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:35 FAX 61 2 9810 8200 F.B. RICE CO. 4 PATENTS 024 b. metal micronjcwdls Metal needles can be formed by physical vapor deposition of appropriate metal layers on solid needle fmans, which can be made of silicon using the techniques described above, or which can be formed using other standard mold techniques such as embossing or injection molding. The metls are selectively removed from the tips of the needles using electropolishing techniques, in which an applied anodic potential in an electrolytic solution will cause dissoltion of metals more rapidly at sharp points, due to concentration of electic field lines at the sharp points_ Once the underlying silicon needle forms have been exposed at the tips, the silicon is selectively etched away to form hollow metallic needle structures. This process could also be used to make hollow needles made from other materials by depositing a material other than metal on the needle forms and following the procedure described above.

A preferred method of fabricating hollow metal microneedles utilizes micromold plating techniques, which are described as follows and in Examples 4 and 5. In a method for making metal microtubes, which does not require dry silicon etching, a photo-defined mold firstis first produced, for example, by spin casting athick layer, typically 150 pm, of an epoxy SU-8) onto a substrate that has been coated with a thin sacrificial layer, typically about 10 to 50 imn Arrays of cylindrical holes are then pbotolithographically defined through the epoxy layer, which typically is about 150 pm thick. (Despot, et al., "Hig-Aspect-Ratio, Ultrathick, Negative-Tone Near-UV Photoresist for MEMS," Proc.

ofIEEE l& Annual International Workshop on MEMS, Nagoya, Japan, pp. 518-522 (Jan.

26-30, 1997)). The diameter of these cylindrical holes defies the outer diameter of the tubes. The upper surface of the substrate, the sacrificial layer, is then partially removed at the bottom of the cylindrical holes in the photoresist The exact method chosen depends on the choice of substrate. For example, the process has been successfully performed on silicon and glass substrates (in which the upper surface is etced using isotropic wet or dry etching techniques) and copper-clad printed wiring board substrates. In the latter case, the copper laminate is selectively removed using wet etching. Then a seed layer, such as Ti/Cuf 30 nm/200 nm/30 im), is conformally DC sputter-deposited omo the upper surface of the epoxy mold and onto the sidewalls of the cylindrical holes. The seed layer should be electrically isolated from the substrat. Subsequently, one or more 19 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 0/01 '04 14:35 FAX 61 2 9810 8200 F.B. RICE CO. 4 PATENTS I025 elecrplatable metals or alloys, such as Ni, e Au, Cu, or Ti, are electroplated onto the seed layer. The surounding epoxy is then removed, leaving microtubes whlch each have an interior annular hole that extends through the base metal supporting the tubes, The rate and duration of electroplating is controlled in order to define the wall thickness and inner diameter of the microtubes. In aon embodiment, this method was used to produce microtubes having a height of between about 150 and 250 pm, an outer diameter of between about 40 and 120 pm, and an inner diameter of between about 30 and 110 m having a wall thickness of 10 pm). In a typical array, the microtubes have a tube center-to-center spacing of about 150 pm, but can vary depending on the desired needle density.

A variation of this method is preferred for forming tapered microneedles. As described above, photolithography yields holes in the epoxy which have vertical sidewalls, such that the resulting shafts of the microeedles are straight, not tapered. This vertical sidewall limitation can be overcome by molding a preexisting 3D structure, a mold-insert. The subsequunt removal of the mold-insert leaves a mold which can be surface plated similarly to the holes produced by photolithography described above.

Alternatively, non-vertical sidewalls can be produced directly in the polymeric mold into which electroplating will take place. For example, conventional photoresists known in the art can be exposed and developed in such as way as to have the surface immediately adjacent to the mask be wider than the other surface. Specialized greyscale photoresists in combination with greyscale masks can accomplish the same effect, Laserablated molds can also be made with tapered sidewalls, by optical adjustment of the beam (in the case of serial hole fabrication) or of the reticle or mold during ablation (in the ase of projection ablation), To form hollow tapered microneedles, the mold-insert is an array of solid silicon microneedles, formed as described in Heary, et al., "Micromachned Needles for the Transdermal Delivery of Dargs;" Micro lectro Mechanical Systems, Heidelberg, Germany, Jan 26-29, pp. 494-498 (1998). First, a layer of a material, such as an epoxy SU-8 Or a polydimethylsiloxane is spin cast onto the aray of silicon microneedles to completely blanket the entire aray. The poxy settles during pre-bake to COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:36 FAX 61 2 9810 8200 F.B. RICE A CO.

PATENTS 40026 create aplanar surce above the silicon aedle tips; the material is then fully prt-baked, photolitographlcally cross-linked, and post-baked.

The upper surface of the epoxy is then etched away, for example with an 0 2

/CHF

3 plasma, until the nidl tips are exposed, preferably leaving between about 1 and 5 pm of tip protruding from the epoxy. The silicon is then selectively removed, for example by using a SP, plasma or aHNO 3 A/HF solution. The remaiing epoxy micromold is the negative of the micrneedles and has a small diameter hole where the tip of the micronocdle formerly protruded.

After the removal ofthe sillcon, a seed layer, such as Ti-Cu-Ti. is conformally 10 .sputer-depoited onto the epoy micromold. Following the same process sequence described fbr hollow metal microtubes, one or more dectroplatable metals or alloys, such as NI, NiFe, Au, or Cu, are electroplated onto the seed layer. Finally, the epoxy is removed, for example by using an 02CHF plasnma, leaving an army of hollow metal micronedles. An advantage of using PDMS in this application is that the micromold can be physically removed from the silicon mold insert by mechanical means, such as peeling, without damaging the silicon mold insert, thus allowing the silicon mold insert to be reused. Furthermorea, the electraplated microneedles can be muoved from the PDMS mold by mechanical means, for example by peeling, thereby allowing the PDMS to also be reused. In a peferred embodiment this method is used to produce microncedles bavin a height of between about 150 and 250 pm, an onter diameter of between about and 120 pm, and an inner diameter of between about 50 and 100 pm. In a typical array, the mlcrbtubes have a tIbe center-to-center spacing of about 150 pm, but a vary depending on the desired needle density. The microneedles are 150 1m in height with a base diameter of 80 pm, a Tip diameter of 10 pm. and a needle-to-needle spacing of 150 pm.

silicon dioxide mitynedes Hollow microneedles formed of silicon dioxide can be made by oxidizing the surface of the silicon microneedle forms (as described above), rather than depositing a metal and then etching away the solid needle forms to leave the hollow silicon dioxide structures. This method is ustrated in igures 4a-4d. Figure 4a shows an array 24 of needle forms 26 with masks 28 n their tips. In Figure 4b, the needle forms 26 have been 21 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:36 FAX 61 2 9810 8200 F.B RICE CO. PATENTS I1027 coated with a layer 30 of metal, silicon dioxide or other material. Figure 4c shows the coated needle forms 26 with the mask 28 removed. Finally, in Figure 4d, the needle forms 26 have been etched away, leaving hollow needles 30 made of metal, silicon dioxide, or other materials.

In one embodiment, hollow, porous, or solid microncedles are provided with longitudinal groovet or other modification to the exterior surface of the microncedlea Groovs, for example, should be useful in directing the flow ofmolecules along the outside of microneedles.

d Ddlymer microned es In a preferred method, polymeric microneedles are made using microfabricated molds. For example, the epoxy molds can be made as described above and injection molding techniques can be applied to form the microneedles in the molds (Weber, et aL, "Micrwmolding a powerful tool for the large scale production of precise microstructures", Proc. SPIE International Soc. Optical Engineer. 2879, 156-167 (1996); Schift, et al., "Fabrication of replicated high precision insert elements for micro-optical bench arrangements" Proc. SPIE International Soc. Optical Engineer. 3513, 122-134 (1998). These micromolding techniques are preferred over other techniques described herein, since they can provide relatively less expensive replication, i.e. lower cost of mass production. In a preferred embodiment, the polymer is biodegradable.

4. Micronedle Device Applications The device may be used for single or multiple uses for rapid transport across a biological barrier or may be left in place for longer times hours or days) for longterm transport of molecules. Depending on the dimensions of the device, the application site, and the route in which the device is introduced into (or onto) the biological barrier, the device may be used to introduce or remove molecules at specific locations.

As discussed above, Figure 1 abows a side elevational view of a schematic of a preferred embodimeg of the microucedlc device 10 in a transdermal application. The device 10 is applied to the skin such that the microncedles 12 penerte through the stratm coreum and enter the viable epidermis so that the tip of the microneedle at least penetrates into the viable epidermis. In a preferred embodiment, drug mlecules in a reservoir within the upper portion 11 flowthrough or around the microneedles and into 22 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:36 FAX 61 2 9810 8200 F.B. RICE CO. PATENTS 1a028 the viable epidermis, where the drug molecules then diffuse into the dermis for local treatment or for transport through the body.

To control the transport of material out of or into the device through the microaeedles, a variety of forces or mechanisms can be employed. These include pressure gradients, concentration gradients, electricity, ultrasound, receptor binding, heat, hemicals, and chemical reactions. Mechanical or other gates in conjunction with the forces and mechanisms described above can be used to selectively control transport of the material.

In particular embodiments, the device should be "user-ftiendly." For example, in some trandermal applications, affixing the device to the skin should be relatively simple, and not require special skills. This embodiment of a microneedle may include an array of ticroneedles attached to a housing containing drug in an internal reservoir, whetein the housing has a bioadhesive coating around the microneedles. The patient can remove a peel-away backing to expose an adhesive coating, and then pres the device onto a clean part of the skin, leaving it to administer drug over the course of, for example, several days.

a- D" Delivery Essentially any drug or other bioaetive agents can be delivered using these devices. Drugs can be proteins, enzymes, polysaccharides, polynucleotide molecules, and synthetic organic and inorganic compounds. Representative agents include antiinfectivs, hormones, such as insulin, growth regulators, drugs regulating cardiac action or blood flow, and drugs for pain control. The drug can be for local treatment or for regional or systemic therapy. The following are representative examples, and disorders they are used to treat: Calcitonin, osteoporosis; Enoxaprin, anicoagulant; Etanercept, rheumatoid arthritis; Erythropoleth, anema; Fentanyl, postoperative and chronic pnin; Filgrastin low white blood cells from hemotherapy; Heparin, mticoagulant; Insulin, human, diabetes; Interferon Beta la, multiple sclerosis; Lidocainc, local anesthesia; Somatropin, growth hormone; and Sumatriptan, migraine headaches.

In this way, many drugs can be delivered at a variety of therapetic rates. The rate can be controlled by varying a number of design factors, including the outer diameter of 23 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/0l 'D.Q 14:37 FAX 81 2 9810 8200 F,B. RICE CO. PATENTS I1029 the mironeedle, the number and size of pores or channels in each microneedle, the mrmber of microneedles in an array, the magnitude and frequency of application of th force driving the drug through the microncedle and/or the holes created by the microneedles. For example, devices designed to deliver drug at different rates might have more microneedles for more rapid delivery and fewer microneedles for less rapid delivery. As another example, a device designed to deliver drug at a variable rate could vary the driving force pressure gradient controlled by a pump) for transport according to a schedule which was pre-programmed or controlled by, for example, the user or his doctor. The devices can be affixed to the skin or other tissue to deliver drgs continuously or intermittently, for durations ranging from a few seconds to several hours or days.

One of skill in the art can measore the rate of drug delivery for particular mlroneedle devices using in vitro and in vivo methods known in the art. For example, to measur the rate oftransdermal drug delivery, human cadaver skin mounted on standard difusion chambers can be used to predict actual rates. See Hadgraft Guy, eds., Transdermal Drnt aeivery: Develomental Issues and Research Initiatives (Marcel Dekker, New York 1989); Bronaugh Maibach. P outaMus Absorption. Mechanism- -Methodology-Dru Delivry (Marcel Dekker, New York 1989). After filling the compartment on the denis side of the diffusion chamber with saline, a microneedle array is inserted into the stratum corneum; a drug solution is placed in the reservoir of the mieroneedle device; and samples ofthe saline solution re taken over time and assayed to determine the rates of drug tranport.

In an alternate embodiment, biodegradable or non-biodegradable microneedles can be used as the entire drug delivery device, where biodegradable microneedles are a prcfcrrd embodiment. For example, the microneedles may be formed of a biodegradable polymer containing a dispersion of an active agent for local or systemic delivery. The agent could be released over time, according to a profile determined by the composition and geometry of the micronedles, the concentration of the drug and other factors. In this way, the drug reservoir is within the matrix of one or more of the mcroneedles.

In another alternate mbodiment, these microneedlcs may be purposeftlly sheared off from the substrate after penetrating the biological barrier. In this way, a portion of the 24 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:37 FAX 61 2 9810 8200 F.B. RICE CO.

4 PATENTS 01030 microneedles would remain within or on the other side of the biological barrier and a portion of the mioroneedles and their substrate would be removed from the biological barrier. In the case of skin, this could involve insrting an arry into the skin, manually or otherwise breaking offthe microneedles tips and then remove the base of the S microneedles. The portion of the microneedles which remains in the skin or in or across another biological barrir could then release drug over time according to a profile determined by the composition and geometry of the microneedles, the concentration of the drug and other factors. In a preferred embodiment, the microneedles are made of a biodegradable polymer. The release of drug from the biodegradable microneedle tips can be controlled by the rate of polymer degradation. Microneedle tips can release drugs for local or systemic effect, or other agents, such as perfume, insect repellent and sun block.

Microneedle shape and content can be designed to control the breakage of microneedles. For example, a notch can be introduced into microneedles either at the time of fabrication or as a subsequent step. In this way, microneedles would preferentially break at the site of the notch. Moreover, the size and shape of the portion of microneedles which break off can be controlled not only for specific drug release patterns, but also for specific interactions with cells in the body. For exanple. objects of a few microns in size a known to be taken up by macrophages. The portions of microncedles that break off can be controlled to be bigger or smaller than that to prevent uptake by macrophages or can be that size to promote uptake by macrophages, which can be desirable for delivery of vaccines.

b. Diagnostic Sensing of Body Fluids (Biosensn) One embodiment of the devices described herein may be used to remove material from the body across a biological barrier, i.e. for minimally invasive diagnostic sensing.

For example, fluids can be transported from intersitial fluid in a tissue into a reservoir in the upper portion of the device. The fluid can then be assayed while in the reservoir or the fluid can be removed from the reservoir to be assayed, for diagnostic or other purposes. For example, interstitial fluids can be removed from the epidermis across the stratum coreunm to assay for glucose concentration, which should be useful in aiding diabetics in determining their required insulin dose. Other substances or properties that would be desirable to deteot include lactate (important for athletes), oxygen, pH, alcohol, COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:37 FAX 61 2 _910 8200 F.B. RICE CO. PATENTS 14031 tobacco metabolites, and illegal drugs (important for both medical diagnosis and law enforcement).

The sensing device can be in or attached to one or more miconcedles, or in a housing adapted to the substrate, Sesing information or signals can be transfrred S optically refractive index) or elctrically measuring changes in electrical impedance, resistance, urrent, voltage, or combination thereof). For example, it may be useful to measure a change as a fimncton of change In resistance of tissue to an electrical current or voltage, or a change in response to channel binding or other criteria (such as an optical change) wherein different resistances are calibrated to signal that more or less flow of drug is needed, or tat delivery has been completed.

In one embodiment, one or more micronceddl devices can be used for (1) withdrawal of interstitial fluid, assay of the fluid, and/or delivery of the appropriate amount of a therapeutic agent based on the results of he assay, either automatically or with humfa intervention. For example, a sensor delivery system may be combined to fom, for example, a system which withdraws bodily fluid, measures its glucose content, and delivers an appropriate amount of inulin. The sensing or delivery step also can be performed using conventional techniques, which would be integrated into use of the microneedle device. For example, the microncedle device could be used to withdraw and assay glucose, and a onventional syringe and needle used to administer the insulin, or vice versa.

In an alternate embodiment, microneedles may be purposefully shered off from the substrate after penetrating the biological barrier, as described above. The portion of the microneedles which remain within or on the other side of the biological barrier could contain one or more biosensoea. For example, the sensor could change color as its output For microneedles sheared off in the skin, this color change could be observed through the skin by visual inspection or with the aid of an optical apparatus.

Other than transport of drugs and biological molecules, the microneedles may be used to transmit or transfer other materials and energy forms, such as light, electricity, heat, or presure. The microneedles, for example, could be used to direct light to specific locations within the body, in order that the light can directly act on a tissue or on an intermediary, such as light-sensiive molecules in photodynamic therapy. The 26 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 .30/01 4 a..48 AX 61 2 9810 8200 F.B, RICE CO. PATENTS E032 microneedles can also be used for aerosolization or delivery for example directly to a mucosal surface in the nasal or buccal regions or to the pulmonary system.

The microncedle devices disclosed herefn also should be useful for controlling transport across tisnes other than akin. For example, micrncedles can be inserted into the eye across, for example, conjunctiva, solera, and/or cornea, to facilitate delivery of drugs into the eye. Similarly, microneedles inserted into the eye can facilitate transport of fluid out of the eye, which may be of benefit for treatment of glaucoma. Microneedles may also be inserted into the buccal (oral), nasal, vaginal, or other accessible mucosa to facilitate transport Into, out of or across those tissues. For example, a drug may be delivered across the buccal mucosa for local tratment in the mouth or for systemic uptake and delivery. As another example, microneedle devices may be used internally within the body on, for example, the lining of the gastrointestinal tract to facilitate uptake of orally-ingested drugs or the lining of blood vessels to facilitate penetration of drugs into the vessel wall. For example, cardiovascular applications include using microneedle devices to facilitate vessel distension or immobilization, similarly to a stent, wherein the microneedles/substate can function as a "staple-like" device to penetrate into different tissue segments and bold their relative positions for a period of time to permit tissue regeneration. This application could be particularly useful with biodegradable deviceo.

These uses may involve invasive procedures to introduce the microncedle devices into the body or could involve swallowing, inhaling, injecting or otherwise introducing the devices in a non-invasive or minimally-invasive manner.

The present invention will be further understood with reference to the following non-limiting examples.

Example It Fabrication of Solid Silicon Microneedles A chromium masking material was deposited onto silicon wafers and patterned into dots having a diameter approximately equal to the base of the desired microneedles.

The wafers were then loaded into a reactive ion etcher and subjected to a carefully controlled plasma based on fluorine/oxygen chemistries to etch very deep, high aspect ratio valleys into the silicon. Those regions protected by the metal mask remain and form the microneedles.

27 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01'04 14:38 FAX1. 2 9810 8200 F.B. RICE CO. PATENTS a1033 <1 00odiented, prime grade, 450-550 pm thick, 10-15 -cm silicon wafers (Nova Electoni Materials Inc., Richardson, TX) were used as the starting material, The wafers were cleaned in a solution of 5 parts by volume deionized water, 1 put hydrogen peroxide, and I part 30% ammonium hydroxide Baker, Phlllpsburg, NJ) at approximately 80*C for 15 minutes, and then dried in an oven (Blue M Electric, Watertown, WI) at 150 C for 10 minutes. Appridmately 1000 A of chromium (Mat-Vac Technology, Flagler Beach, FL) was deposited onto the wafers using a DC-sputterer (601 Sputtering System, CVC Products, Rochester, NY). The chromium layer was patterned into 20 by 20 arrays of 80 pn diameter dots with 150 pm centerto-center spacing using the lithographic process described below.

A layer of photosensitive material (1827 photoresist, Shipley, Marlborough, MA) was deposited onto the chromium layer covering the silicon wafers. A standard lithographic mask (Telic, Santa Monica, CA) bearing the appropriate dot array pattern was positioned on top of the photoresist layer. The wafer and photoresist were then exposed to ultraviolet (UV) light through the mask by means of an optical mask aligner (Hybralign Series 500, Optical Associates, Inc., Milpitas, CA). The exposed photoresist was removed by soaking the wafers in a liquid developer (354 developer, Shipley, Marlborough, MA) leaving the desired dot array of photoresist on the chromium layer.

Subsequently, the wafers were dipped into a chromium etchant (CR-75; Cyanteck Fremont, CA), which etched the chromium that had been exposed during the photolithography step, leaving dot arnys of chromium (covered with photoresist) on the surface of the silicon wafer. The photoresist still present on the chromium dots formed the masks needed for fabrication of the microncedles, described below.

The mioroneedles were fabricated using a reactive ion etching techniques based on the Black Silicon Method developed at the University of Tweote. The pattened wafers were etched in a reactive ion etcher (700 series wafer/batch Plasma Processing System, Plasma Then, St Petersburg, FL) with means for ensuring good thermal contact between the wafers and the underlying platen (Apiezon N, K.J. Lasker, Clairton, PA).

The wafers were etched using the following gases and conditions: SFe (20 standard cubic centimeste per minute) and Oa (15 standard cubic centimeters per minute) at a pressure of 150 mTor and a power of 150 W for a run time of approximately 250 minuts. These 28 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:38 FAX 61 2 9810 8200 F.B. RICE CO, PATENTS R034 conditions caused both deep vertical etching and slight lateral undmeotching. By controlling the ratio offlow rates ofthe SF 6 and O gases used to form the plasma, the aspect ratio of the microneedles could be adjusted. The regions protected by the hrgomium miaskc remained and formed the microneedles. Etching was allowed to proceed until the masks fell off due to underetching, tesulting in an array of sharp silicon spikes.

Example 2: Tranadrmal Transport Using Solid Microneedlea To deterinise if microfabricated microncedles could be used to enhance tranademnnal drug delivery, arrays of microneedles were made using a deep plasma etching teclhnIque. Their ability to penetrate human skin without breaking was tested and the resulting changes in transdarmal transpmrt were measured.

Arrays ofmioroneedles were fabricated having extremely sharp tips (radius of curvature leas than 1 pm), and are approximately 150 pm long. Because the skin surface is not flat due to dermatoglyphics and hair, the full length of thse microeedles will not penetrate the skin. All experiments were performed at room temperature (23±20C).

The ability of the mlcroneedles to pierce skin without breaking was then tested.

Insertion of the arrays into skin required only gentle pushing. Inspection by light and electron microscopy showed that more than 95% of microneedles within an array pierced across the stratum earneum of the epidermis samples. Moreover, essentially all of the microgeedles that penetrated the epidermis remained intact. On those very few which broke, only the top 5-10 jun was damaged. Mironeedle arrays could also be removed without difficulty or additional damage, as well as re-insearted into skin multiple times.

To quantitatively assess the ability of mioroneedles to increase transdrmal transport, caloein permeability of human epidermnnia with and without inserted microneedle arrays was measured. Calcein crosses skin very poorly under normal circumstances and therefore represents an especially difficult compound to deliver. As expected, passive permeability of calcein across unaltered sldn was very low, indicating that the pidemnnis samples were intact.

Insertion of microaneedles into skin was capable of dramatally increasing permeability to calcein. When microneedles were inserted and left embedded in the skin, calcein permeability was increased by mom than 1000-fold, Insertion of microneedles for 29 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:39 FAX 61 2 9810 8200 F.B. RICE CO. PATENTS il035 s, fllowed by their removal, yielded an almost 10,000-fold increase. Finally, insertion of a microneedle array for I h, fbllowed by its removal, increased skin permeability by about 25,000-fold. Permeabilities for skin with micronedles inserted and then removed are higher than for skin with miconeedles remaining embedded probably because the microneedles thmselves or the silicon plate supporting the array may block access to the microscopic holes created in the skin. Light microscopy showed that the holes which remained in the skin after microneedles were removed were approximately 1 pm in size.

To confirm in vitro experiments which showed that skin permeability can be 0 significantly increased by miaoneedls, studies wre conducted with human volunteers.

They indicated that microneedles could be easily inserted into the skin of the forearm or hand. Moreover, insertion of mironeedle arrays was never repbrted to be painful, but sometimes elicited a mild "wearing" sensation described as a weak pressure or the feeling ofa piece of tape afxed to the skin. Although transport experiments were not performed in vi, skin electrical rsistance was measured before and after raicronccedle insertion.

Microneedles caused a 50-fold drop in skin resistance, a drop similar to that caused by the insertion of a 30-gauge "macroncedIk," Inspection of the site immediately after miaroneedle insertion showed no holes visible by light microscopy. No erythema, edema, or other reaction to microneedles was observed over the hours and days which followed.

This indicates that microneedle arrays can permeabilize skin in human subjects in a nonpainful and safe manner.

Example 3: Fabrication of Silicon Microtabes Three-dimensional arrays of microtubes were fabricated from silicon, using deep reactive ion etching combined with a modified black silicon process in a conventional reactive ion etcher. The fabrication proces s illustrated in Figures 5ad. First, arrays of pm diameter circular holes 32 were patterned through photoresist 34 into a 1 pm thick SiO layer 36 on a two inch silicon wafer 38 (Figure 5a). The wafer 38 was then etched using deep reactive ion etching (DRIB) (Laerm, et al., "Bosch Deep Silicon Etching: Improving Uniformity and Etch Rate for Advanced MEMS Applications," Micro Electro Msohanital Systems, Orlando, Florida, USA (Jan. 17-21, 1999)). in an inductively coupled plasma (ICP) reactor to etch deep vertical holes 40. The deep silicon etch was COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:39 FALX 1 2 9810 8200 F.B. RICE &t CO.

4 PATENTS 036 stopped afterthe holes 40 are approximaely 200 pm deep into the silicon substrate 38 (Figure Sb) and the photoresist 34 was removed. A second photolithography step patterned the remaining SiOa layer 36 into circles concentric to the holes, thus leaving ring shaped oxide masks 34 surrounding the holes (Figure Sc). The photoresist 34 was then removed and the wafer 38 was again deep silicon etched, while simultaneously the holes 40 were etched completely through the wafer 38 (inside the Si S ring) and the silicon was etched around the SiO 2 ring 38 leaving a cylinder 42 (Figure 5d). The resulting tubes were 150 Ctm in height, with an outer diameter of 80 pm. an inner diameter of 40 m, and a tube center-to-center spacing of 300 pm.

Example 4: Mecremald Fabrication of Metal Microtubes Hollow metal microtubes were prepared without dry silicon etching, using a thick, photo-defined mold of epoxy. The sequences are illustrated in Figures 6a-e. First, a thick layer of SU-8 epoxy 44 was spin cast onto a silicon or glass substrate 46 that had been coated with 30 nm of titanium 48, the sacrificial layer. Arrays of cylindrical holes 49 were then photolithographically defined through an epoxy layer 44, typically 150 tm thick (Figue 6a). The sacrificial layer then was partially removed using a wet etching aolution containing hydrofluoric acid and water at the bottom of the cylindrical holes in the SU-8 photoresist 46 (Figure 6b). A seed layer of T/Cu/Ti (30 nm/200 nm/30 nm) 39 was then conformally DC sputter-deposited onto the upper surface of the epoxy mold and onto the sidewalls of the cylindrical holes 49 (Figure 6c). As shown in Figure 6c, the seed layer 39 was electrically isolated from the substrate. Subsequently, NIFe was electroplated onto the seed layer 39 (Figure 6d), the epoxy 44 was removed from the substrate, and the surrounding epoxy 44 was removed (Figure 6e). The resulting microtubes are 200 pm in height with an outer diameter of 80 pm, an inner diameter of pm, and a tube center-to-center spacing of 150 pm. The holes in the interior of the microtubes protrude through the base metal supporting the tubes.

Example 5: Micromold Fabrication ofTapered Mieroeedles A micromold having tapered walls was fibricated by molding a preexisting 3-D array ofmicroncedles, Le. the mold-insert, and subsequently removing the mold insert.

The micromold was then surface plated In a manner similar to that for he microtubes described in Example 4. The fabrication sequence is illustrated in Figures 7a-7d.

31 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/0,:.'04 14:39 FAX 61 2 98108200 F.B. RICE CO.

4 PATENTS 0037 First, an array of solid silicon microoedles 50 were prepared as described in Henry, et al, "Micromachined Noeedles for the Trmnsdennal Delivery of Drugs," Micro Eectro Mechanict &slms, Heidelbrg, Germany, Jan. 26-29, pp. 494-498 (1998).

Then, a layer of epoxy 52 (SU-8) was spin cast onto the microneedle awray to completely blanket the army (Figur 7a). The epoxy 52 settled during pro-bake to create a planar surface above the tips of the microneedles 50. The epoxy 52 was then fully pro-baked, photolithopaphically cross-linked, and post-baked.

Then, the upper surface of the epoxy 52 was etched away using an /CIF 3 plasma until approximately 1 to 2 pm of the nooeedle tips 54 were exposed, protruding from the epoxy 52 (Figure 7b). The silicon was then selectively removed by using a SF6 plasma (Figure 7c). The remaining epoxy mold 52 provided a negative of the microneedles with a small diameter hole where the tip of the silicon needle protruded.

After the removal of the silicon, a seed layer of Tli-Cu-TI 54 was conformally sputterdeposited onto the top and sidewalls of the epoxy micromold 52. Following the same proceu. sequence as described in Example 4, NiFe was then cloctroplated onto the seed layer 54 (Figure 7c). Finally, the epoxy was removed using an 2OCHF,) plasma, leaving a 20 x 20 array of NiFe hollow metal microneedles 54 (Figure 7d). The microneedles 54 were 150 pm in height with a base diameter of 80 pm, atip diameter of 10 pm, and a needle-to-needle spacing of 150 pm.

Mioromold-based microneedles also have been succesasftully manufactured using a process in which the epoxy mold material was replaced with PDMS. In this case, it was possible to remove the mold from the mold insert, as well as the miceoneedles frm the mold, using only physical techniques such as peeling. This approach advantageously requres no dry etching and allows one to reuse both the mold and the mold insert Example 6: Mlcromld Fabrication of Tapred Microneedles Usig Laser-Formed Molds A micromold having tapered walls was fabricated by use of laser ablation techniques, as shown in Figures Ba-d. A laser-ablatable polymer sheet 60 such as ICAPTON polyimide apprximately 150 microns in thickness was optionally laminated to a thin (10-30 micron) metal sheet 62 such as titanium (Figure Ba). A tapered hole 64 was formed in the metal/polymer laminate 60/62 using a laser technique such as excimer 32 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:40 FAX 61 2 9810 8200 F.B. RICE CO. PATENTS 038 laser ablation,(Figure 8b). The entry hole of the laser spot was on the metal side 62, and a through hole was made through both the metal sheet and the polymer film. The through hole 64 was tapered in combination with either defcusing or appropriate subtrate motion to create a taper such that the wide end of the hole 64 (typically 40-50 microns) was on the metal side 62 and the narrow end ofthe hole 64 (typically 10-20 microns) was on the polymer 60 side. A thin layer of metal 66, e.g. titanium, of thickness 0.1 micron was then deposited, using a sputter-deposition technique, in such a way that the metal 66 deposited on the metal film side and coated the polymer sidewalls, but did not coat the polymer 60 side of the laminate (Figure 8c), Blectrodeposition of metal 68, e.g., gld, to athickness of I to 5 microns was then performed on the titanum-coated metal surface 66, and polymer sidewalls curved section of 60 next to 64. Finally, the polymer was removed, using e.g. an oxygen plasma, to form the completed microneedles (Figure 8d).

Alternate polymer removal methods, such as thermal, solvent, aqueous, or photodegradation followed by solvent or aqueous removal, are also possible if the polymer material is chosen appropriately a photoresist resin).

Example 7: Formation of Mlcroneedles by Embosliag Formation of a microneedle by embossing is shown in Figures 9a-9f. A polymeric layer 70 (Figure 9a) is embossed by a solid microneedle or microneedle array 72 (Figure 9b). The array 72 is removed (Figure 9c), and the layer 70 is etched from the nonembossed side 74 until the embossed cavity 76 is exposed (Figure 9d). A metallic layer 78 is then deposited on the embossed side and the sidewalls, but not on the non-embossed side 74 (Figre 9e). This layer 78 is optionally thickened by electrodepouition of an additional metal layer 80 on top of it (Figure 9e). The polymer layer 70 is then removed to form the micronedles 78/80 (Figure Example 8: Tranadermal Application ofHollow Mieroneedles The bore of hollow microneedles must provide fluid flow with minimal clogging in order to be suitable to transport material, such as in transdermal drug delivery.

Therefore, micronecdles and microtubes were evaluated to determine their suitability for these functions.

33 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:40 FAX 61 2 9810 8200 F.B. RICE CO. PATENTS E1039 Hollow metal and silicon microneedles, produced as described in Examples were inserted through human skin epidermis with no apparent clogging of the needle bores. Scanning electon microscopy of a hollow metal (NiFe) microneedle penetrating up through the underside of human epidermis showed the microneedle remains intact, with the tip free of debris. Similarly, silicon microneedles, metal mieroneedles, and metal microtobes were sucessfully inserted tlhough huan skidn. Also, the hollow microneedles were shown to permit the flow of water through their bores.

Example 9: Drug Transport Through Microneed]es luerted Into Skin Studies were performed with solid aid hollow microneedles to demonstrate transport of molecules and fluids. As shown in Table 1, transport of a number of different compounds across skin is possible using microneedles. These studies were performed using either solid silicon microneedles or using hollow silicon microneedles made by methods described in this patent Transport was measured across hmnan cadaver epidermis i vitro using Franz diffusion chambers at 37 °C using methods described in S.

Henry, D. McAllister, M.G. Allen, and M. Prausnitz, "Mirofabricated microneedles: A novel method to increase transdermal drug delivery" J Pharm. Sci. 922-25 (1998).

The transdermal delivery of calcein, insulin, bovine serum albumin and nanoparticles was measured. Delivery refers to the ability to transport these compounds from the stratum comeum side of the epidermis to the viable epidermis side. This is the dinction of transport associated with delivering drugs into the body. Removal of calcein was also measured. Removal refers to the ability to transport calcein from the viable epidermis side of the epidermis to the stratum comemn side. This is the direction of transport associated with removing from the body compounds found in the body, such as glucose.

In all cases shown in Table 1, transport of these compounds acoss skin occurred at levels below our detection limit when no needles were inserted into the skin. Intact skin provides an excellent barierto transport of these compounds. In all cases examined, when solid microneedles were inserted into the skin and left in place, large skin permeabilities were measured, ndicating that the microneedles had created pathways for transport across the skin. urthermore, in all cases, when solid milroneedles were inserted into the skin and then removed, even greater skin permeabilities resulted.

34 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30 30/01 '04 14:40 FAX 61 2 O.Z9 82 0R CT F.B. RICE CO, -P PATENTS Q040 Finally, when hollow micraneedles were inserted into the sia and left in place, still greater skin penneabilities resulted for those compounds tested. These studies show that microncedles can dramatically increase skin prneability and can thereby increase transport of a number of different compounds across the skin. It also shows that when S solid microneedles are used, a preferred embodiment involves inserting and then removing microneedles, rather than leaving them in place. It also shows that using hollow microneedles are a preferred embodiment over the use of solid microunedlc.

In Table 2, the flow rate of water through hollow silicon microneedles is shown as a fumction of applied pressure. These data demonstrate that significant flow rates of water through microncedles can be achieved at modest pressures.

TABLE 1: Transport of Drugs Through Microeedles Inserted Into Skin Compound No Solid needles Solid needles Hollow needles inserted inserted and needles removed inserted Calcein 4x 10l 1 x delivery Calcein 2x 0li n.a.

removal Insulin 10 1 x n.a delivery Bovine serum 9 x 108 9 X albumin delivery U.4. 3 x Nanoparticle na 3 x 10 .e.

deliveimi means tht the t n port wabeow the dtsEtion ll at ILa. mfeaM that the da are not avauable.

Nanopartlles were made of latex with a diamter of approximately 100 nm.

TABLE 2! Flow Rate of Water Through Hollow Silicon Microncedles as a Funtion of Applid Pressure Pressure si) Flow rate(miin) 16 24 31 38 COMS ID No: SMBI-00593518 Received by IP Australia: Time 14:42 Date 2004-01-30

Claims (44)

1. A device for transport of molecules or energy across biological barriers comprising: a plurality of hollow or porous microneedles having a length between 100 pm and 1 mm, wherein at least a portion of the shaft of the microneedles has a width between about 1 pm and 200 pm, and a substrate to which the microneedles are attached or integrally formed, wherein the microneedles extend at an angle from a surface of the substrate.

2. The device of claim 1 wherein the angle is about

3. The device of claim 1 or claim 2 which is formed using a microfabricated mold.

4. The device of any one of claims 1-3 wherein the microneedles are hollow.

The device of any one of claims 1-4 wherein the microneedles are formed by a method comprising the steps: forming a micromold having sidewalls which define a surface of the microneedles; depositing material on sidewalls to form the hollow microneedles; and removing the micromold from the microneedles.

6. The device of claim 5 further comprising forming the mold using a laser to selectively remove material.

7. The device of claim 1 wherein the microneedles are fabricated using a micromachining technique selected from the group consisting of lithography, plasma etching, wet chemical etching, dry etching, thermal oxidation of silicon, electroplating, electroless plating, boron diffusion, phosphorus diffusion, arsenic diffusion, antimony diffusion, ion implantation, film deposition, sputtering, chemical vapor deposition, epitaxy, chemical anodization, electrochemical anodization, micromolding, laser ablation, and combinations thereof.

8. The device of any one of claims 1-7 wherein the length of the microneedles is between about 100 pm and 500 pm.

9. The device of any one of claims 1-8, wherein the microneedles have an outer diameter between about 10 pm and about 100 pm.

The device of claim 1 or 4 wherein the hollow microneedles have an inner diameter between about 3 pm and about 80 pm.

11. The device of claim 1 wherein the microneedles are hollow and each comprise a base end which tapers to a sharp tip end, and wherein the length of the microneedles is between about 100 p.m and 500 p.m.

12. The device of any one of claims 1-11 wherein the microneedles are formed of a material selected from the group consisting of silicon, silicon dioxide, metals, ceramics, polymers, and combinations thereof.

13. The device of claim 12 wherein the microneedles are formed of a metal.

14. The device of claim 12 wherein he metal is selected from the group consisting of nickel, iron, gold, titanium, tin, copper, stainless steel, plantinum, palladium, and alloys thereof.

The device of claim 12 wherein the material is a biodegradable polymer selected from the group consisting of poly(hydroxyl acid)s, polyanhydrides, poly(ortho)esters, polyurethanes, poly(butyric acid)s, poly(valeric acid)s, and poly(lactide-co- caprolactone)s.

16. The device of claim wherein the microneedles are microtubes.

17. The device of claim 1 wherein the microneedles each comprise a shaft having a circular or non-circular cross-sectional area perpendicular to the axis of the microneedle.

18. The device of claim 1 wherein the microneedles each have a configured or grooved outer surface.

19. The device of any one of claims 1-18 wherein the molecules or energy is delivered from one or more chambers or reservoirs in connection with at least one of the microneedles.

The device of claim 19 further comprising a means for controlling the flow of molecules or energy through the microneedles.

21. The device of claim 20 wherein the means is selected from the group consisting of permeable membranes, fracturable impermeable membranes, gates, valves, and pumps.

22. The device of any one of claims 1-21 further comprising a means for temporarily securing the microneedle device to the biological barrier.

23. The device of claim 22 wherein the securing means is selected from the group consisting of collars, tabs, adhesive agents, and combinations thereof.

24. The device of claim 1 wherein the device is electrochemically, thermally, mechanically or magnetically active.

The device of claim 1 wherein the surface of the microneedles is shaped or comprises a material to facilitate passage of the microneedles across the biological barrier or (ii) passage of the molecules across the biological barrier by means of the microneedles.

26. The device of claim 1 wherein the microneedles form a mechanical support when inserted into a tissue.

27. The device of claim 26 wherein the mechanical support forms a vascular or urethral stent.

28. The device of claim 1 further comprising a flexible backing.

29. The device of any one of claims 1-28 further comprising molecules to be released or delivered.

The device of claim 29 wherein the molecules are incorporated into and released from the microneedles after the microneedles are administered.

31. The device of claim 30 wherein the microneedles are formed of a biodegradable material and sheared off at a site of administration.

32. A method for transporting molecules or energy into or across a biological barrier comprising: inserting into the biological barrier the microneedles of the device of any one of claims 1-31; and applying a driving force to transport the molecules or energy through the microneedles.

33. A method for transporting molecules or energy into or across a biological barrier comprising: inserting into the biological barrier the microneedles of the device of any one of claims 1-28; removing the microneedles from the barrier to create a hole in the barrier; and applying the molecules or energy into the holes.

34. The method of claim 32 wherein the molecules or energy is driven from one or more chambers which are in communication with at least one of the microneedles.

The method of any one of claims 32-34 wherein the biological barrier is skin.

36. The method of any one of claims 32-35 further comprising vibrating the microneedles.

37. The method of claim 32 wherein the microneedles of step are attached to a reservoir containing drug molecules, wherein the drug molecules pass from the reservoir, through the microneedles, and into or across the barrier.

38. The method of claim 32 wherein the driving force is obtained from a source selected from the group consisting of pressure gradients, concentration gradients, convection iontophoresis, electroporation, waveguiding, and cavitation. 38

39. The method of claim 32 wherein the microneedles of step is attached to a reservoir, and a driving force is applied to force the material or energy to pass from or across the barrier, through the microneedles, and into the reservoir.

The method of claim 39 wherein the driving force is selected from the group consisting of diffusion, capillary action, electroosmosis, electrophoresis, mechanical pumps, convection, vacuum and combinations thereof.

41. The method of claim 34 wherein the device has at least two chambers having one or more materials to be transported.

42. The method of claim 41 wherein at least one chamber contains a drug and at least one other chamber contains an administration vehicle, wherein the drug and vehicle are mixed together to form the molecules transported through at least one microneedle.

43. A method of making the microneedle device of any one or claims 1-31, the method comprising: forming a microneedle using a micromachining technique selected from the group consisting of lithography, plasma etching, wet chemical etching, dry etching, thermal oxidation of silicon, electroplating, electroless plating, boron diffusion, phosphorus diffusion, arsenic diffusion, antimony diffusion, ion implantation, film deposition, sputtering, chemical vapour deposition, epitaxy, chemical anodization, electrochemical anodization, micromolding, laser ablation and combinations thereof.

44. A method for making a device having a plurality of hollow microneedles, and a substrate to which the microneedles are attached or integrally formed, wherein the microneedles extend at an angle from a surface of the substrate, the method comprising: forming the microneedles using a micromold having sidewalls which define a surface of the microneedle. The method of claim 44 wherein one or more holes are photolithographically defined in a second substrate, thereby forming the micromold.