WO2008130590A2 - Biodegradable matrix materials - Google Patents

Abstract

The invention provides biodegradable degradable matrix materials. The matrix materials of the invention are useful in a variety of applications such as to make implantable medical devices (e.g., implants, coatings, in-situ formed matrices, stents, tubes, aneurysm coils, and the like), in-situ delivery (e.g., cell delivery or bioactive agent delivery), and as tissue sealants. In many embodiments, the matrix materials of the invention are formed by reacting: (a) a first component comprising an aminated natural degradable polysaccharide with (b) a second component comprising an amine-reactive compound.

Description

BIODEGRADABLE MATRIX MATERIALS CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application Serial Number 60/925,275, filed April 19, 2007, and entitled "BIODEGRADABLE MATRIX MATERIALS," the disclosure of which is incorporated herein by reference.

BACKGROUND

Polymeric hydrogel matrices have been described as biomaterials useful for the treatment of a variety of medical conditions. (See, for example, U.S. Patent Nos. 5,529,914, 5,854,382, 6,007,833, 6,051,248, 6,153,21 1, 6,316,522, 6,818,018, and 7,070,809.) Depending on the polymeric material used, these matrices may be biostable, or biodegradable following a period of implantation. The polymeric material used to form these matrices is desirably biocompatible, meaning that it does not have an adverse biological effect on the organism in which the hydrogels are placed or formed. Accordingly, it is generally desirable to avoid the use of biodegradable materials that degrade into products that cause unwanted side effects in the body by virtue of their presence or concentration in vivo. These unwanted side effects can include immune reactions, toxic buildup of the degradation products in the liver, or the initiation or provocation of other adverse effects on cells or tissue in the body.

The ability of the hydrogel matrices provide a positive effect for the treatment of a subject may occur by the structural and chemical properties of the hydrogel matrices mimicking the natural tissue and facilitating tissue healing. Hydrogel matrices may also exert a protective affect to tissues, thereby preventing tissue or cellular damage (for example in the case of an inflammatory response).

In some cases, hydrogel matrices may be associated with a drug that is designed to provide a therapeutic effect to tissue at the site the hydrogel is localized or formed. For example, it has been proposed to use to use a drug that is released from the matrix by diffusion, or released by the degradation of the hydrogel matrix, for treatment of a target tissue. Hydrogel matrices have been proposed for medical use in a variety of forms. In some cases, hydrogel matrices can be formed as a tissue-healing articles on a wound site, designed to promote tissue regeneration and healing of the wound. When applied this way, these hydrogel matrices are amorphous and typically conform the tissue on which the hydrogel matrix-forming composition is applied. These matrices can be formed in situ, such as by the application of the matrix- forming composition on the treatment site and the treatment of the composition to cause crosslinking of the hydrogel forming material.

In other cases, hydrogel matrices can be formed in association with an implantable medical device. In these cases, the matrices may have a more distinct form, such as a coating on the surface of a device, or a fill that conforms to a void in the device.

Many challenges remain for the formation and use of hydrogel matrices as in situ formed articles, or in association with implantable medical devices. In the case of biodegradable matrices, one challenge relates to the preparation of matrices having suitable degradation properties in vivo. For example, some natural polymers, such as hyaluronic acid and alginic acid, are biodegradable in polymeric form, but can be crosslinked to form non-biodegradable hydrogel matrices. On the other hand, hydrogel matrices formed from polymeric materials with a significant amount of ester linkages will typically degrade by bulk erosion. The bulk erosion may cause the matrices to degrade too rapidly and/or without control. This may cause matrix fragmentation resulting in the undesirable loss of embolic matrix fragments into the circulatory system.

In addition, many hydrogel matrices lack desirable physical properties, such as sufficient durability for implantable procedures, or controlled swelling. For example, matrices that are highly hydrophilic can rapidly absorb water and cause plasticization of the polymer, resulting in a soft gel-like matrix. This characteristic is undesirable as the matrix can tear upon expansion and ruin its physical integrity.

Some hydrogels of the prior art rely on chemical agents to cure the polymeric materials. Many of these chemical agents are small compounds that can cause tissue damage, and are therefore undesirably used in the body.

In addition, hydrogel matrices that are designed for drug release are generally not well developed. Hydrogel matrices intended to release a therapeutic agent have been problematic because release is typically inadequately controlled. For example, in many cases, the majority of the agent is released from the matrix in a short burst, resulting in depletion of the agent from the hydrogel matrices. This burst is particularly undesirable when a therapeutic effect is required over an extended period of time. The short term burst is thought to be caused by the hydrophilicity of the polymeric materials driving water into the matrix, causing an increase in the osmotic pressure in the coating. As a result, the permeability of the matrix for the drug is significantly increased, resulting in the elution of the drug at a therapeutically ineffective rate.

In addition, certain polymeric materials, reagents, and/or methods of preparing hydrogels may be incompatible with or unsuitable for certain therapeutic agents. For example, in technologies using polymeric macromers, hydrogel formation is typically carried out using a free radical-generating system. Unfortunately, free radicals can be damaging to many macromolecules, such as nucleic acids, and even cells. Also, the use of polymers with an abundance of charged groups as hydrogel forming materials may attract oppositely charged therapeutic agents and alter their release from the gel. Alternatively, matrices formed from highly charged polymers and including cellular material may cause undesirable cellular responses in the cells.

Embodiments of the present invention address one or more of these problems associated with hydrogel technologies of the prior art.

SUMMARY The present invention provides biodegradable matrix materials prepared from natural degradable polysaccharides. The matrix materials of the invention are useful in a variety of applications such as to make implantable medical devices (e.g., implants, coatings, in-situ formed matrices, stents, tubes, aneurysm coils, and the like), in-situ delivery (e.g., cell delivery or bioactive agent delivery), and as tissue sealants. In many embodiments, the matrix materials of the invention are formed by reacting: (a) a first component comprising an aminated natural degradable polysaccharide with (b) a second component comprising an amine-reactive compound.

In many embodiments, the aminated natural biodegradable polysaccharide of the first component is prepared by a process comprising the steps of: (a) providing a natural biodegradable polysaccharide;

(b) reacting at least a portion of hydroxyl groups that are present on the natural biodegradable polysaccharide with a coupling agent (e.g., 1,1 '- carbonyldiimidazole ("CDI")) to form a natural biodegradable polysaccharide comprising pendant imidazole groups; and (c) reacting at least a portion of the pendant imidazole groups with an amine-containing compound to form the aminated natural biodegradable polysaccharide.

In many embodiments, the amine-containing compound used in step (c) comprises two or more primary amine groups that are separated by a linking group. A representative formula for the amine-containing compound is H₂N-R-NH₂, where R is a straight or branched chain alkyl linking group. Examples of useful amine- containing compounds include 1 ,6-diaminohexane, 1,4-diaminobutane, 1,3- diaminopropane, and mixtures thereof.

Although any amount of amine substitution may be useful, in many embodiments, the aminated natural biodegradable polysaccharide has a degree of amine substitution ranging from about 0.1 to about 1.0, more typically ranging from about 0.2 to about 0.3.

In many embodiments, the natural biodegradable polysaccharide comprises a poly-α(l— >4)glucopyraπose such as amylose, maltodextrin, cyclodextrin, or a mixture thereof. In some embodiments, the natural biodegradable polysaccharide comprises a non-reducing polysaccharide such as polyalditol. Typically, the natural biodegradable polysaccharide has a molecular weight of about 30,000 Da or less.

Suitable amine-reactive compounds include amine-reactive functional groups such as aldehydes, isothiocyanates, bromoacetyls, chloroacetyls, iodoacetyls, anhydrides, imidazole carbamates, isocyanates, maleimides, and combinations thereof. In a preferred embodiment, the amine-reactive compound is an imidazole carbamate formed by reacting a hydroxy functional compound with CDI. In many embodiments, the amine-reactive compound is prepared from a hydroxy-functional compound. Typically, the hydroxy-functional compound has at least 2 hydroxyl groups (e.g., about 2 to 4 hydroxyl groups) per molecule and has a molecular weight of about 10,000 Da or less. Preferably the hydroxy-functional compound has 2-4 hydroxyl groups, meaning that the synthesis can be carried out to provide a second component that has two to four amine-reactive groups. In preferred embodiments the second component that has two amine-reactive groups.

Representative examples of hydroxy-functional compounds include poly(ethylene glycol), tetraethylene glycol, triethylene glycol, trimethylolpropane ethoxylate, and pentaerythritol ethoxylate. In a preferred embodiment, the hydroxy- functional compound comprises poly(ethylene glycol) having the structure

HO-(CH₂-CH₂-O)_n-H where n ranges from about 3 to about 150.

In many embodiments, the poly(ethylene glycol) has a number average molecular weight (M_n) ranging from about 100 to about 5000 Da.

Although any stoichiometric ratio may be useful, the biodegradable matrix material is typically formed by reacting the aminated natural biodegradable polysaccharide and the amine-reactive compound at a ratio amine groups to amine- reactive groups ranging from about 1 : 1 to about 5: 1. BRIEF DESCRIPTION QF THE DRAWINGS

For a fuller understanding of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawing figures wherein like reference character denote corresponding parts throughout the several views and wherein: FIG. 1 is a molecular drawing of the compound CDI.

FIG. 2 is an exemplary reaction scheme showing the preparation of an amine- functional polysaccharide.

FIG. 3 is an exemplary reaction scheme showing the preparation of an amine- reactive compound. FIG. 4 is an exemplary reaction scheme showing the preparation of an amine- reactive compound. FIG. 5 is an exemplary reaction scheme showing the formation of a matrix material of the invention by the reaction of an amine-functional polysaccharide with an amine-reactive compound.

DETAILED DESCRIPTION The embodiments of the present invention described herein are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art can appreciate and understand the principles and practices of the present invention. All publications and patents mentioned herein are hereby incorporated by reference. The publications and patents disclosed herein are provided solely for their disclosure. Nothing herein is to be construed as an admission that the inventors are not entitled to antedate any publication and/or patent, including any publication and/or patent cited herein. The invention relates to biodegradable matrix materials that are formed as the reaction product of two reactive components (i.e., an A-B reactive pair), or more than two reactive components. In many embodiments, the first component comprises a natural biodegradable polysaccharide that has been chemically modified to have pendant amine groups, and the second component comprises an amine- reactive compound. To form the degradable matrix material, the first and the second components are mixed with one another at a predetermined ratio to initiate crosslinking of the first (amine-functional) component and the second (amine- reactive) component.

Biodegradable matrix materials of the invention are useful in a variety of applications such as to make implantable medical devices (e.g., stents, tubes, aneurysm coils), in-situ delivery (e.g., cell delivery or bioactive agent delivery), and may also be used as tissue sealants.

In embodiments of the invention, a multifunctional linking group is used to covalently bond a natural biodegradable polysaccharide (e.g., maltodextrin) to an amine-reactive compound in order to form the matrix material. Useful multifunctional linking groups are characterized by having at least two reactive groups that are capable of reacting with active-hydrogen containing functional groups, such as hydroxyl groups and amine groups. In some embodiments, the linking groups are further characterized in having two or more reactive groups where the reactive groups display different reactivity rates to active hydrogen-containing compounds. Aminated Polysaccharide: To prepare the first reactive component, a natural biodegradable polysaccharide is chemically modified in order to introduce amine groups that are pendant from the polysaccharide. Although other reaction schemes may be useful, in exemplary embodiments, the pendant amine groups are introduced by first reacting at least a portion of the hydroxyl groups that are present on the natural biodegradable polysaccharide with CDI as shown in FIG. 1.

CDI is useful linking group because it reacts with a hydroxyl group that is present on the natural biodegradable polysaccharide to form a carbamate ester. Once CDI reacts with a first hydroxyl group on the natural biodegradable polysaccharide to form a carbamate ester, the reactivity of the pendant imidazole group to a second hydroxyl groups is significantly reduced. This is advantageous because the pendant imidazole group can remain as an unreacted pendant group from the polysaccharide, and can be used to form a covalent bond to another molecule, typically a more reactive active-hydrogen compound such as an amine. In many embodiments of the invention, the pendant imidazole group is reacted with an amine-containing compound (e.g., a diamine) in order to form an amine-functional polysaccharide.

In preferred embodiments, the imidazole-functional polysaccharide is reacted with an excess of the amine-containing compound in order to maximize the amount of pendant amine functionality that is imparted to the natural biodegradable polysaccharide. For example, in many embodiments, the imidazole-functional polysaccharide is slowly added to a solution containing the amine-containing compound in order to provide reaction conditions where the amine-containing compound is in substantial excess relative to the imidizole-functional polysaccharide. Useful amine-containing compounds typically contain two or more primary amine groups that are separated by a linking group, such as an alkyl group. In some embodiments the amine-containing compound fits the general formula H₂N-R-NH₂, where R is a straight or branched chain alkyl group. Representative examples of multifunctional amine compounds include 1,6-diaminohexane, 1,4-diaminobutane, 1,3-diaminopropane, and the like.

The reaction scheme described above may be varied in order to produce aminated polysaccharides having varying degrees of substitution (DS). As used herein the term "degree of substitution" refers to the number of derivatized hydroxyls per anhydroglucose monomer unit of the polysaccharide. In some embodiments, the degree of substitution (DS) of the polysaccharide ranges from about 0.1 to about 1.0. In more preferred embodiments, the degree of substitution ranges from about 0.2 to about 0.3, although other degrees of substitution may be desirable. In an exemplary embodiment, polyalditol is reacted with CDI followed by 1 ,6-diaminohexane in order to produce an aminated polyalditol having a degree of substitution ranging from about 0.2 to about 0.3.

The reaction of polyalditol with CDI, followed by reaction with the amine- containing compound 1,6-diaminohexane is shown in FIG. 2.

After reacting with an excess of amine-containing compound, the resulting aminated polysaccharide is typically purified in order to remove any unreacted amine. Purification techniques include, for example, recrystallization (e.g., using THF), other precipitation methods and/or dialysis. Matrix materials of the invention make use of natural biodegradable polysaccharides to provide an enzymatically degradable segment to the matrix material. As used herein, the term "natural biodegradable polysaccharide" refers to a non-synthetic polysaccharide that is capable of being enzymatically degraded but that is generally non-enzymatically hydrolytically stable. Natural biodegradable polysaccharides include polysaccharide and/or polysaccharide derivatives that are obtained from natural sources, such as plants or animals. Natural biodegradable polysaccharides include any polysaccharide that has been processed or modified from a natural biodegradable polysaccharide (for example, maltodextrin is a natural biodegradable polysaccharide that is processed from starch). In many embodiments, the natural biodegradable polysaccharide has no naturally-occurring amine groups pendent from its backbone. For example, the natural biodegradable polysaccharide may be a homoglycan (repeating monomeric units are the same) having pendent hydroxyl groups. In some embodiments, the natural degradable polysaccharide is a poly-α(l—>4)glucopyranose, more specifically derived from a linear poly-α(l→4)glucopyranose.

Exemplary natural biodegradable polysaccharides include polyalditol, amylose, maltodextrin, and cyclodextrin.

The natural biodegradable polysaccharide typically has a molecular weight of about 500,000 Da or less, or 50,000 Da or less. Typically, the natural biodegradable polysaccharides has an average molecular weight of 500 Da or greater. A particularly preferred size range for the natural biodegradable polysaccharides is in the range of up to about 30,000 Da.

In exemplary embodiments, the natural biodegradable polysaccharide is a non-reducing polysaccharide. Non-reducing polysaccharides are preferred for many applications because they do not contain pendant aldehyde groups. Pendant aldehyde groups are undesirable because they may react with the pendant amine groups on the amine-functional polysaccharide, which may cause a reduction in the reactivity and/or shelf-life of the amine-functional polysaccharide. In addition, a non-reducing polysaccharide can provide an inert matrix thereby improving the stability of sensitive bioactive agents, such as proteins and enzymes. An exemplary non-reducing polysaccharide comprises polyalditol, which is available from GPC (Muscatine, Iowa).

Amine-Reactive Compound:

Biodegradable matrix compositions of the invention comprise the reaction product of (A) a first component comprising an aminated natural biodegradable polysaccharide; (B) a second component comprising an amine-reactive compound. To prepare the amine-reactive compound, a hydroxy-functional compound is chemically modified in order to introduce amine-reactive functional groups. Useful hydroxy-functional compounds are characterized by having at least two pendant hydroxy groups (typically 2 to 4), having biocompatibility, having appreciable water-solubility, and having a molecular weight of about 10,000 Da or less. In many embodiments, the hydroxyl groups are present as pendant groups from a hydrophilic organic backbone that comprises atoms of carbon, hydrogen, and oxygen. In some embodiments, the organic backbone is an alkoxyalkane backbone. Representative examples of useful hydroxy functional compounds include poly(ethylene glycol), tetraethylene glycol, triethylene glycol, trimethylolpropane ethoxylate, and pentaerythritol ethoxylate. In many embodiments, a preferred hydroxy functional compound is poly(ethylene glycol) having the structure HO-(CH₂-CH₂-O)_n-H. Typically, the value of n ranges from about 3 to about 150 and the number average molecular weight (M_n) of the poly( ethylene glycol) ranges from about 100 Da to about 5000 Da, more typically ranging from about 200 Da to about 3500 Da.

In some embodiments, the amine-reactive compound is formed by reacting the hydroxy functional compound with CDI. CDI reacts with the hydroxyl groups on the hydroxy functional compound resulting in the formation of pendant imidazole carbamate groups. The reaction of poly(ethylene glycol) with CDI to produce an amine-reactive compound is shown in FIG. 3. The pendant imidazole carbamate groups are reactive with amine groups, such as the amine groups that are present on the aminated polysaccharide described hereinabove. In another embodiment, an amine-reactive compound is prepared by first reacting succinic anhydride with a polyol (e.g., a diol, triol, or tetrol) to form a multi-functional carboxylic acid compound. The succinic anhydride reacts with the alcohol groups in the polyol to form an ester linkage and a terminal carboxylic acid group. The multifunctional carboxylic acid compound is then reacted with N- hydroxysuccimide (NHS) which reacts with the terminal carboxylic acid groups to form an amine-reactive NOS groups. In an exemplary embodiment, polyethylene glycol is reacted with succinic anhydride to form a dicarboxylic acid compound (see, FIG. 4, Product 1). The dicarboxylic acid compound is then reacted with N- hydroxysuccimide (NHS) in order to form an amine-reactive compound having two terminal NOS groups (see, FIG. 4, Product 2).

The amine-reactive compound could be provided with amine-reactive functional groups other than imidazole carbamate groups or NOS groups. Representative examples of amine-reactive groups include aldehyde, isothiocyanate, bromoacetyl, chloroacetyl, iodoacetyl, anhydride, imidazole carbamate, isocyanate, maleimide, and combinations thereof.

In view of the reactive nature of the first component and the second component, these components are typically held in separate containers from one another until prior to the time that formation of the matrix material is desired. When the formation of the matrix is desired, the first component and the second component are mixed with one another in the desired ratio to initiate formation of the matrix material by reaction of amine-containing polysaccharide with the amine- reactive compound. Reaction of the first and second components with one another results in the formation of the enzymatically degradable matrix material. For example, the reaction of the product of FIG. 1 with the product of FIG. 2 is shown in FIG. 5.

Typically, it is desirable to react the first component and the second component with one another in approximately a stoichiometric ratio in order to form the matrix materials of the invention. By stoichiometric ratio it is meant that the number of moles of amine groups in the amine-functional polysaccharide is equal to the number of moles of amine-reactive groups in the amine-functional compound. Although approximately a stoichiometric ratio is typically preferred, the ratio of amine groups to amine-reactive groups (amine groups: amine-reactive groups) may vary in certain embodiments, for example, ranging from about 1 : 1 to about 5: 1. After initiating the formation of the matrix material by reacting the first component with the second component, the components typically cure to form the matrix material in a time period that ranges from several minutes to several hours. More typically, the components cure to form the matrix material in a time period that ranges from about 1 to about 60 minutes.

The cure time of a given formulation of the matrix material may be adjusted to suit a desired end use for the matrix material. One method of adjusting the rate of reaction is to control the pH of the first and second components. Generally speaking, a higher pH will favor a faster reaction rate, whereas a lower pH will favor a slower reaction rate between the first and second components. In most embodiments, the pH is controlled between a lower pH limit of about 7.5 and an upper pH limit of about 9.5, although other pH values may be suitable for certain applications. The pH of the matrix material may be controlled by buffering the first and/or second components using conventional buffering materials such as phosphate, borate, and bicarbonate buffers. Another method of adjusting the reaction rate is to control the molecular weight of the amine-reactive component. This can be accomplished, for example, by controlling the molecular weight of the hydroxy-functional material that is used to form in the amine-reactive component. Typically, low molecular weight and high functionality of the hydroxy-functional material favors high reactivity (i.e., shorter cure times) for amine-reactive component.

In addition to affecting cure time, the molecular weight and functionality of the amine-reactive component may also affect the physical properties of the matrix material that is formed upon cure. For example, it has been observed that as the molecular weight of the poly(ethylene glycol) in the amine-reactive component is reduced, the matrix material becomes denser, harder, and more brittle. By contrast, as the molecular weight of the poly(ethylene glycol) in the amine-reactive component increases, the matrix material becomes softer and more flexible. A similar observation can be made with respect to functionality. As the functionality of the amine-reactive component increases, the matrix material tends to become denser, harder, and more brittle. The physical properties may be modified in order to achieve desired properties for a given end-use.

In many embodiments, the aminated polysaccharide (first component) is provided in the form of a water-based solution having a percent solids (% solids) of aminated polysaccharide ranging from about 10% weight to about 70% weight, for example, from about 30% weight to about 70% weight, or from about 40% weight to about 70% weight, or from about 50% weight to about 70% weight. This typically provides a solution viscosity that ranges from about 1 cps to about 500 cps. In many embodiments, the amine-reactive component (second component) is provided in the form of a water-based solution having a percent solids (% solids) of amine-reactive component ranging from about 10% weight to about 70% weight. This typically provides a solution viscosity that ranges from about 1 cps to about 500 cps. In some embodiments, the amine-reactive component is based on a low molecular weight poly(ethylene glycol) which is a liquid at room temperature. In these embodiments, the amine-reactive component may be provided in the form of a neat (i.e., 100% solids) liquid. This is advantageous for some applications (e.g., as a tissue sealant) because the amine-reactive component can be stored neat for long periods and can be used neat (i.e., without reconstituting with water). When provided in the form of a neat liquid, the amine-reactive component typically has a viscosity that ranges from about 20 cps to about 50 cps.

In an exemplary embodiment, the first and second components are held in separate chambers of dual syringe mixing device. When cure of the matrix is desired, simultaneous application of hand pressure to both syringe plungers in the device causes both the first and second component to flow from their respective syringes into a stationary mixing device (e.g., a "split flow" type mixer) where the first and second components are mixed with one another at a predetermined ratio. After being mixed, the polymerizing composition exits the device though a single outlet orifice which can be positioned at the desired application site. Useful dual syringe mixing devices are commercially available under the trade designation "MIXPAC" from Mixpac Systems AG (Rotkreuz, CH).

In order to promote efficient mixing, it is generally desirable for the first component and the second component to be formulated to have approximately the same viscosity. In many embodiments, the first and the second component are water-based solutions that have similar viscosities ranging from about 1 cps to about 500 cps. The viscosity may be controlled, for example, by adjusting the percent solids (% solids) of the components by appropriate dilution with water. Matrix materials of the invention are biodegradable. As used herein the term

"biodegradable" refers to matrix materials that are (1) hydrolytically degradable, (2) enzymatically degradable, or both hydrolytically and enzymatically degradable. As used herein the term "hydrolytically degradable" refers to matrix materials that are degradable by hydrolysis reactions. As used herein the term "enzymatically degradable" refers to matrix materials that are degradable in the presence of an enzyme that can enzymatically degrade the particular polymeric material that is used to prepare the matrix. An enzymatically degradable matrix can be generally non- enzymatically hydrolytically stable, meaning that in the absence of an enzyme capable of degrading the matrix, the matrix will not degrade by simple hydrolysis. In some embodiments, the matrix materials of the invention are degradable in-situ. Degradation of a matrix formed of a biodegradable polysaccharide may commence when placed in contact with a body fluid or tissue, which may include an enzyme capable of degrading the matrix at its surface. The enzyme can be a natural biodegradable polysaccharide-degrading enzyme, such as a carbohydrase.

Examples of carbohydrases that can specifically degrade natural biodegradable polysaccharide coatings include α-amylases, such as salivary and pancreatic α-amylases; disaccharidases, such as maltase, lactase and sucrase; trisaccharidases; and glucoamylase (amyloglucosidase).

Serum concentrations for amylase are estimated to be in the range of about 50 -100 U per liter, and vitreal concentrations also fall within this range (Varela, R.A., and Bossart, G.D. (2005) JAm Vet Med Assoc 226:88-92). The matrix materials of the invention may be used in a variety of applications including both externally formed implanted medical devices, and in-situ formed matrices. In some embodiments, the matrix materials of the invention are provided in the form of coatings on the surface of a portion of a medical device.

In one type of application, the matrix materials of the invention are used to form medical articles for later implantation in the body at a target site. For example, the matrix may be formed as a three dimensional article, in the shape of the device having structural features useful for treating a condition in the body. Medical articles of this type will typically be manufactured in a controlled forming process, such as an extrusion or a molding process. For example, reactive solutions may be combined and injected into a mold and cured to form a device with a desired shape.

Representative uses for formed medical implants include as occlusion devices including, for example, vasculature occlusion devices (e.g., to treat neural or abdominal aneurisms) and urogenital occlusion devices (e.g., in the fallopian tube of a female patient). Vascular occlusion devices may be in the form of wires, coils, braids, strings, and the like; some vascular occlusion devices have a helically wound configuration. Exemplary coils are generally 2.2 mm or less in diameter, more particularly in the range of 0.2 mm to 2.2 mm and can be composed of wires 1.25 mm or less in diameter, for example in the range of 0.125 mm to 1.25 mm. Lengths of vascular occlusion devices typically range from 0.5 to 100 centimeters. Pre-formed medical implants may also be used in certain prosthesis applications, for example, vascular prosthesis applications and urogenital prosthesis applications. Representative devices include vascular stents and urogenital stents. Matrix materials of the invention may also be used to form orthopedic devices. Representative examples include intravertebral discs, bone plates, and bone fasteners, such as screws, staples, pins, and the like.

Matrix materials of the invention may also be used to form ophthalmic articles. The ophthalmic article can be configured for placement at an external or internal site of the eye. In some aspects, the articles can be utilized to deliver a bioactive agent to an anterior segment of the eye (in front of the lens), and/or a posterior segment of the eye (behind the lens). Suitable ophthalmic devices can also be utilized to provide bioactive agent(s) to tissues in proximity to the eye, when desired. Articles configured for placement at an internal site of the eye can reside within any desired area of the eye. In some aspects, the ophthalmic article can be configured for placement at an intraocular site, such as the vitreous. Illustrative intraocular devices include, but are not limited to, those described in U.S. Patent Nos. 6,719,750 B2 ("Devices for Intraocular Drug Delivery," Varner et al.) and 5,466,233 ("Tack for Intraocular Drug Delivery and Method for Inserting and Removing Same," Weiner et al.).

In some aspects, the implantable medical article provides mechanical properties at the implantation site and maintains these mechanical properties until they are no longer needed. After this period of time has elapsed, the medical implant is degraded to an extent that the properties are no longer provided by the medical implant, and the biodegradable components can be absorbed and/or excreted by the body. In some embodiments, the medical implant slowly degrades and transfers stress at the appropriate rate to surrounding tissues as these tissues heal and can accommodate the stress once borne by the medical device. Advantageously, the properties of matrix materials of the invention may be tailored to fit the desired end-use of the implantable medical articles. For example, matrix materials that are strong and rigid may be useful for orthopedic applications, whereas matrix materials that are soft and flexible may be useful for occlusion devices. As discussed herein, by selection of the materials making up the matrix materials, certain properties such as tensile strength, elongation, flexibility, and the like may be controlled. For example, certain properties of the matrix materials may be controlled though selection of the molecular weight and functionality of the amine-reactive component.

In another aspect, the matrix materials of the invention are used in in-situ applications. Examples of in-situ applications include in-situ formation of an occlusion device and in-situ formation of a tissue sealant.

In one in-situ application, a biodegradable occlusion can be formed from the matrix material of the invention by a method that includes step of: (a) providing a first composition comprising an amine-functional natural biodegradable polysaccharide; (b) providing a second composition having an amine-reactive group; and (c) reacting the first and second compositions at the target site to form a matrix material of the invention in the form of a biodegradable occlusion.

In another in-situ application, the matrix materials of the invention are useful as biodegradable tissue sealants. Tissue sealants may be used to decrease or prevent the migration of fluid from or into a tissue. When used as tissue sealants, the matrix materials of the present invention are typically provided in two component formulations, which are mixed with one another prior to or during application of the tissue sealant to the tissue. The first component comprises a water solution of an amine-functional polysaccharide. The second component comprises the amine- reactive component, which may be in the form of a water-based solution or may be a 100% solids (i.e., neat) composition. A 100% solids formulation can be provided, for example, by using a low molecular weight poly(ethylene glycol) in the amine- reactive component. The low molecular weight poly(ethylene glycols) which are liquids at room temperature allow the formation of amine-reactive components that are liquids at room temperature. The first and second component may be mixed with one another prior to or at the same time as the tissue sealant is applied to the tissue. Application methods include spraying, brushing, dipping, atomizing, and the like. In an exemplary embodiment, the first and second components are held in separate chambers of dual syringe mixing device. When cure of the matrix is desired, simultaneous application of hand pressure to both syringe plungers in the device causes both the first and second component to flow from their respective syringes into a stationary mixing device (e.g., a "split flow" type mixer) where the first and second components are mixed with one another at a predetermined ratio. After being mixed, the polymerizing composition exits the device though a single outlet orifice which can be positioned at the desired application site of the tissue sealant. Useful dual syringe mixing devices are commercially available under the trade designation "MIXPAC" from Mixpac Systems AG (Rotkreuz, CH).

In some embodiments, the tissue sealant further includes a hemostatic agent. Examples of hemostatic agents include collagen and thrombin. Other hemostatic agents are reported, for example, in U.S. Patent No. 6,162,241. Typically, the hemostatic agent is formulated with the first, amine-functional, component. Whether in a preformed medical article or in an in-situ type application, the matrix materials of the invention may be useful for the delivery of one or more bioactive agents to a target site, and in this manner can function as bioactive agent- releasing implants or depots. Representative classes of bioactive agents include, but are not limited to, ACE inhibitors, actin inhibitors, analgesics, anesthetics, anti- hypertensives, anti polymerases, antisecretory agents, anti-AIDS substances, antibiotics, anti-cancer substances, anti-cholinergics, anti-coagulants, anticonvulsants, anti-depressants, anti-emetics, antifungals, anti-glaucoma solutes, antihistamines, antihypertensive agents, anti-inflammatory agents (such as NSAIDs), anti metabolites, antimitotics, antioxidizing agents, anti-parasite and/or anti-Parkinson substances, antiproliferatives (including antiangiogenesis agents), anti-protozoal solutes, anti-psychotic substances, anti-pyretics, antiseptics, antispasmodics, antiviral agents, calcium channel blockers, cell response modifiers, chelators, chemotherapeutic agents, dopamine agonists, extracellular matrix components, fibrinolytic agents, free radical scavengers, growth hormone antagonists, hypnotics, immunosuppressive agents, immunotoxins, inhibitors of surface glycoprotein receptors, microtubule inhibitors, miotics, muscle contractants, muscle relaxants, neurotoxins, neurotransmitters, polynucleotides and derivatives thereof, opioids, photodynamic therapy agents, prostaglandins, remodeling inhibitors, statins, steroids, thrombolytic agents, tranquilizers, vasodilators, and vasospasm inhibitors.

In a related aspect, the matrix materials of the invention may be useful for cell delivery applications. In a representative cell delivery application one or more cell types that are to be delivered to a target site in the body are prepared and the cells are collected using known techniques. Once the cells have been collected, they are then suspended in a water-based solution comprising the amine-functional polysaccharide. After suspending the cells, the first component and the second component are then mixed together in order to initiate cure of the matrix material. The reaction typically proceeds spontaneously at room temperature, but the solution may also be heated. Once the matrix material has cured, the cured matrix material incorporating the cells can be delivered to the desired implantation site using known techniques for implantation. Alternatively, the components can be mixed directly at the site of intended implantation and cured in situ. Representative implantation sites include cardiac tissue, cartilage defects and cutaneous ulcers. Advantageously, as compared to other matrix materials for cell encapsulation, the matrix materials of the present invention do not cure by a free radical process which may in some instances be harmful to certain cell types. Examples of useful cell types include platelets, stem cells, T lymphocytes, B lymphocytes, acidophils, adipocytes, astrocytes, basophils, hepatocytes, neurons, cardiac muscle cells, chondrocytes, epithelial cells, dendrites, endrocrine cells, endothelial cells, eosinophils, erythrocytes, fibroblasts, follicular cells, ganglion cells, hepatocytes, endothelial cells, Leydig cells, parenchymal cells, lymphocytes, lysozyme-secreting cells, macrophages, mast cells, megakaryocytes, melanocytes, monocytes, myoid cells, neck nerve cells, neutrophils, oligodendrocytes, oocytes, osteoblasts, osteochondroclasts, osteoclasts, osteocytes, plasma cells, spermatocytes, reticulocytes, Schwann cells, Sertoli cells, skeletal muscle cells, and smooth muscle cells. Also included are genetically modified, recombinant, hybrid, mutated cells, and cells with other alterations.

The invention will be further described with reference to the following non- limiting Examples. It will be apparent to those skilled in the art that many changes can be made in the embodiments described without departing from the scope of the present invention. Thus the scope of the present invention should not be limited to the embodiments described in this application, but only by embodiments described by the language of the claims and the equivalents of those embodiments. Unless otherwise indicated, all percentages are by weight. The invention will be further illustrated with reference to the following examples which are intended to aid in the understanding of the present invention, but which are not to be construed as a limitation thereof.

EXAMPLES EXAMPLE 1 - Synthesis of Aminated Polvalditol

Vacuum oven-dried Polyalditol PD60 (10.00 g) was dissolved in anhydrous dimethyl sulfoxide, DMSO, (50 mL) in a 120 mL amber vial. In a separate 30 mL amber vial, CDI, (3.00 g) was dissolved in dry DMSO (25 mL). The CDI solution was poured into the maltodextrin solution and purged with nitrogen gas before being capped. The reaction solution was placed on a rotary shaker for 20 minutes. Into a separate 120 mL amber vial, 1,6-diaminohexane (10.80 g) was warmed to 45°C and dissolved in dry DMSO (10 mL) and a Teflon stir bar was inserted and placed on a stir plate. The maltodextrin/CDI solution was slowly poured into the stirred diamine solution over a 20 minute period. Once the addition was complete the reaction vial was transferred into a 55⁰C oven and allowed to stir overnight. The next day, the reaction solution was precipitated into 1 liter tetrahydrofuran, THF, and a white precipitate formed. The mixture was stirred for one hour and the solvent was decanted. Fresh THF (1 L) was poured into the 2-L Erlenmeyer flask and the white precipitate was stirred for one hour. This step was repeated twice. The final mixture was filtered using a water-aspirator, Bϋchner funnel, and Whatman-brand paper filter and a white precipitate was collected (13.14 g). The precipitate was then dried overnight at 40°C under vacuum. A small sample of the material (50 mg) was dissolved with 5 mL deionized water in a 7-mL vial. To this sample was added 1 mL of ninhydrin solution (3.6 mg/mL in IPA). The sample was capped and heated to 7O⁰C in a water bath. The solution turned a dark purple color indicating the presence of primary amines.

EXAMPLE 2 - Poly (ethylene glvcoO^sn-diimidazolyl carbamate (DiIQ

Vacuum oven-dried poly(ethylene glycol), MW-3350, (6.70 g) was dissolved in anhydrous tetrahydrofuran, THF, (20 mL) in a 60 mL amber vial with slight heating (4O⁰C). In another 60 mL amber vial CDI (0.81 1 g) was dissolved in 10 mL dry THF. A Teflon stir bar was inserted into the CDI solution and placed on a stir plate. The PEG solution was pipetted into the CDI solution while stirring at room temperature. The reaction vial was purged with nitrogen gas once the addition was complete. The reaction was allowed to stir at room temperature for two hours. After two hours, the reaction solution was precipitated into 1 liter of chilled, anhydrous diethyl ether while stirring. The ether solution was decanted, and the precipitate was rinsed three more times (3 x 1 L) with fresh, anhydrous ether while stirring. The precipitate was collected by vacuum filtration using a water-aspirator, Bϋchner funnel, and a Whatman-type paper filter. The collected white precipitate (6.84 g) was dried overnight in a vacuum oven (3O⁰C).

EXAMPLE 3 - Polv(ethylene glycolWio'diimidazolyl carbamate

Vacuum oven-dried poly(ethylene glycol), MW 2000, (20.00 g) was dissolved in anhydrous tetrahydrofuran, THF, (200 mL) in a 500 mL amber vial with slight heating (40°C). In another 500 mL amber vial CDI (4.10 g) was dissolved in 50 mL dry THF. A Teflon stir bar was inserted into the CDI solution and placed on a stir plate. The PEG solution was pipetted into the CDI solution while stirring at room temperature. The reaction vial was purged with nitrogen gas once the addition was complete. The reaction was allowed to stir at room temperature for two hours. After two hours, the reaction solution was precipitated into 2 liters of chilled, anhydrous diethyl ether while stirring. The ether solution was decanted and the precipitate rinsed three more times (3 x 1 L) with fresh, anhydrous ether while stirring. The precipitate was collected by vacuum filtration using a water-aspirator, Bϋchner funnel, and a Whatman-type paper filter. The collected white precipitate (19.41 g) was dried overnight in a vacuum oven (30°C).

EXAMPLE 4 - Poly(ethylene glycoOrsnn-diimidazoyl carbamate

Vacuum oven-dried poly(ethylene glycol), MW 1500, (15.00 g) was dissolved in anhydrous tetrahydrofuran, THF, (150 mL) in a 500 mL amber vial with slight heating (40°C). In another 500 mL amber vial CDI (4.10 g) was dissolved with 50 mL dry THF. A Teflon stir bar was inserted into the CDI solution and placed on a stir plate. The PEG solution was pipetted into the CDI solution while stirring at room temperature. The reaction vial was purged with nitrogen gas once the addition was complete and the reaction was allowed to stir at room temperature for two hours. After two hours, the reaction solution was precipitated into 2 liters of chilled, anhydrous diethyl ether while stirring. The ether solution was decanted and the precipitate rinsed three more times (3 x 1 L) with fresh, anhydrous ether while stirring. The precipitate was collected by vacuum filtration using a water-aspirator, Bϋchner funnel, and a Whatman-type paper filter. The collected white precipitate (14.68g) was dried overnight in a vacuum oven (30°C).

EXAMPLE 5 - PolvCethylene glycoD_jono-diimidazolyl carbamate Poly(ethylene glycol), MW 1000, (20.59 g) was dissolved in anhydrous tetrahydrofuran, THF, (200 mL) in a 500 mL amber vial. In a 500 mL amber vial CDI (8.40 g) was dissolved in 50 mL dry THF. A Teflon stir bar was inserted into the CDI solution and placed on a stir plate. The PEG solution was pipetted into the CDI solution while stirring at room temperature. The reaction vial was purged with nitrogen gas once the addition was complete. The reaction was allowed to stir at room temperature for two hours. After two hours, the reaction solution was precipitated into 2 liters of chilled, anhydrous diethyl ether while stirring. The ether solution was decanted and the precipitate was rinsed three more times (3 x 1 L) with fresh, anhydrous ether while stirring. The precipitate was collected by vacuum filtration using a water-aspirator, Bϋchner funnel, and a Whatman-type paper filter. The waxy precipitate (17.59 g) was dried overnight in a vacuum oven (22°C).

EXAMPLE 6 - Polyfethylene glvcolWrdiimidazolyl carbamate

Poly(ethylene glycol), MW 600, (30.15 g) was transferred to a 150 mL round bottom flask and dissolved in 50 mL dichloromethane (DCM). The solvent was stripped off using a rotary evaporator and high temperature water bath. This step was repeated twice more. In a 500 mL round bottom flask CDI (22.90 g) was dissolved in 250 mL DCM. A Teflon stir bar was inserted into the CDI solution and placed on a stir plate under nitrogen. The PEG₆₀₀ was dissolved with 50 mL DCM and slowly added to the stirring CDI solution and stirred at room temperature for two hours under nitrogen. The reaction solution was transferred into a 1 L separatory funnel and washed twice with 1 mM HCl followed by two brine solution washes. The organic solution was collected and dried with magnesium sulfate. The dried solution was filtered through a Whatman paper filter into a clean 500 mL round bottom flask and the DCM was rotary evaporated with mild heat (3O⁰C). A clear, slightly yellowish-tinted oil was collected (37.02 g).

EXAMPLE 7- Tetraethylene glvcol-diimidazolyl carbamate

Tetraethylene glycol, TEG, MW 194.23, (21.80 g) was transferred to a 500 mL round bottom flask and dissolved in dichloromethane, DCM, (100 mL). The solvent was stripped off using a rotary evaporator and high temperature water bath. The stripping step was repeated twice. In a 1000 mL round bottom flask CDI (40.05 g) was dissolved in 380 mL DCM. A Teflon stir bar was inserted into the CDI solution and placed on a stir plate under nitrogen. The TEG was dissolved with 200 mL DCM and was slowly added to the stirred CDI solution, and the mixture was stirred at room temperature for two hours under nitrogen. The reaction solution was transferred into a 1 L separatory funnel and washed twice with 1 mM HCl followed by two brine solution washes. The organic solution was collected and dried with magnesium sulfate. The dried solution was filtered through a Whatman paper filter into a clean 500 mL round bottom flask and the DCM was rotary evaporated with mild heat (30° C). A clear oil was collected (39.46 g).

EXAMPLE 8 -Triethylene glycol-diimidazolyl carbamate

Triethylene glycol, TrEG, MW 150.17, (3.01 g) was transferred to a 50 mL round bottom flask and dissolved in dichloromethane, DCM, (30 mL). The solvent was stripped off using a rotary evaporator and high temperature water bath. The stripping step was repeated twice. In a 250 mL round bottom flask CDI (7.14 g) was dissolved in 100 mL DCM. A Teflon stir bar was inserted into the CDI solution and placed on a stir plate under nitrogen. The TrEG was dissolved in 50 mL DCM and slowly added to the stirred CDI solution, and the mixture was then stirred at room temperature for two hours under nitrogen. The reaction solution was transferred into a 250 mL separatory funnel and washed twice with 1 mM HCl followed by two brine solution washes. The organic solution was collected and dried with magnesium sulfate. The dried solution was filtered through a Whatman paper filter into a clean 250 mL round bottom flask and the DCM was rotary evaporated with mild heat (3O⁰C). A clear oil was collected (5.93 g).

EXAMPLE 9 -Trimethylolpropane ethoxylate (20 EOVtriimidazolyl carbamate Trimethylolpropane ethoxylate (20/3 EO/OH), MW 1014, (10.14 g) was transferred to a 150 mL round bottom flask and dissolved in dichloromethane, DCM, (50 mL). The solvent was stripped off using a rotary evaporator and high temperature water bath. The stripping step was repeated twice. In a 1000 mL round bottom flask CDI (6.49 g) was dissolved in 250 mL DCM. A Teflon stir bar was inserted into the CDI solution and placed on a stir plate under nitrogen. The trimethylolpropane ethoxylate was dissolved with 100 mL DCM and slowly added to the stirred CDI solution, and the mixture was stirred at room temperature for two hours under nitrogen. The reaction solution was transferred into a 500 mL separatory funnel and washed twice with 1 mM HCl followed by two brine solution washes. The organic solution was collected and dried with magnesium sulfate. The dried solution was filtered through a Whatman paper filter into a clean 500 mL round bottom flask and the DCM was roto evaporated with mild heat (30° C). A clear oil was collected (12.07 g).

EXAMPLE 10 - Pentaervthritol ethoxylate (15 EOVtetraimidazolyl carbamate

Pentaerythritol ethoxylate (15/4 EO/OH), MW 797, (1 1.96 g) was transferred to a 500 mL round bottom flask and dissolved in dichloromethane, DCM, (100 mL). The solvent was stripped off using a rotary evaporator and high temperature water bath. The stripping step was repeated twice. In a 1000 mL round bottom flask CDI (16.22 g) was dissolved in 200 mL DCM. A Teflon stir bar was inserted into the CDI solution and placed on a stir plate under nitrogen. The pentaerythritol ethoxylate was dissolved with 100 mL DCM and slowly added to the stirred CDI solution, and the mixture was stirred at room temperature for two hours under nitrogen. The reaction solution was transferred into a 500 mL separatory funnel and washed twice with 1 mM HCl followed by two brine solution washes. The organic solution was collected and dried with magnesium sulfate. The dried solution was filtered through a Whatman paper filter into a clean 500 mL round bottom flask and the DCM was roto evaporated with mild heat (30° C). A clear oil was collected (15.89 g).

EXAMPLE 1 1 - Matrix Formation An 8-ml clear glass vial was used to add 721 mg of PEGi_OOo-dilC and 300 μl of deionized water. The vial was vortexed for 5-minutes to dissolve the solid material. To this solution was then added approximately 1220 μl of a viscous PD60- NH₂ solution of approximately 40% solids at pH 7.0, and the resulting mixture was vortexed for 90 seconds followed by sonication for 25 seconds to remove air bubbles. This resulting solution was then injected into molds within about 10 minutes of mixing. The molds were used to form articles.

Filaments were prepared by using two types of silicone tubing as molds for the filaments. The silicone tubing had an inner diameter of 0.64 mm and 1.58 mm. The sections of tubing were filled with the solution described above and were placed horizontally in a sealed vial to prevent the solution from drying out.

Buttons were prepared by using the snap caps of 1.5 ml conical tubes (VWR, North American Cat.No: 89000-044) as the molds. The caps were filled with solution and the conical tubes was put back on the filled caps acting as a cover for the filled caps. The solution filled molds described above were allowed to cure for about 16 hours before checking. The filaments were removed from the silicone tubing by forcefully injecting water into one end causing the cured filament to be pushed out of the other end of the tube.

The resulting filament was flexible and slightly elastic. Upon further hydration (i.e., soaking in deionized water for 24 hours), the matrix swelled at least about 20% and the mechanical strength of the matrix was reduced. Upon drying, the filaments shrank and became tougher and stiffer, but were also more elastic and stretchy.

The cured buttons were left in the mold (i.e., caps) and were tested for compression strength using a Texture Analyzer (TA) system. The cured buttons remained hydrated since they were enclosed with the conical tube acting as a cap to prevent dehydration. Two cured button samples were tested for compression strength both in "as is" condition and again after a 2 hour partial rehydration procedure. The cured buttons were partially rehydrated by filling the conical tube with deionized water, and allowing the cured buttons to soak in the deinoized water. The cap was positioned below the conical tube during the rehydration so that the deionized water was on top of the cured button during the rehydration procedure. The average compression strength for the cured buttons in "as is" condition was 693 grams of force. The average compression strength for the cured buttons after rehydration was 935 grams of force.

EXAMPLE 12: Preparation of ό-IYtert-butoxycarbonyQamino^'lhexanoic acid (EAC- BOC)

The EACA (6-aminohexanoic acid, 6.1O g, 46.50 mmole) and Na₂CO₃ (9.72 g, 91.71 mmole) were dissolved in water (90 ml). To the EACA solution, which was cooled in an ice bath, was added dropwise a solution of di-ført-butyl dicarbonate (10.00 g, 45.82 mmole) in THF (tetrahydrofuran, 44 ml). The mixture was stirred overnight and allowed to warm to room temperature. The reaction was diluted with water (1200 ml) and extracted with hexane (2 x 100 ml). The organic layer was extracted with a saturated water solution OfNa₂CO₃ (100 ml) followed by water (100 ml). The combined aqueous layers were cooled in an ice bath. The pH was adjusted to 2 using 1 N HCl. The reaction mixture was extracted with EtOAc (ethyl acetate, 5 x 200 ml). The EtOAc solution was washed with water (100 ml), dried over Na₂SO₄ (sodium sulfate, 100 g), filtered and evaporated to give the EAC-BOC (10.3 g, 97% yield), which slowly crystallized. NMR analysis at 400 MHz was consistent with the desired product: ¹H NMR (CDCl₃) acid proton 9.23 (b, 0.64), amide proton 4.61 (b, 0.67H), methylene adjacent to carbamate 3.13 (m, 2H), methylene adjacent to carboxyl 2.36 (m, 2H), other methylenes 1.65, 1.52, 1.38 (m, 6H), and t- butyl protons 1.45 (m, 8.5)

EXAMPLE 13: Preparation of a Maltodextrin (MD) 6-Utert- butoxycarbonvDaminolhexanoate (MD-EAC-BOC)

MD (5.00 g, -30.5 mmole), EAC-BOC (Example 12, 7.05 g, 30.5 mmole), NHS (N- hydroxysuccinimide, 0.69 g, 6 mmole), and DMAP (N^V-dimethylpyridin-4-amine, .242 g, 4 mmole) was dissolved in DMSO (dimethylsulfoxide, 50 ml). DIC (N,N- diisopropylcarbodiimide, 4.80 g [5.88 ml], 38.0 mmole) was added to the stirred room temperature DMSO solution in 0.5 ml portions with >5 minute periods between additions. The reaction was placed on a rotator overnight. The product was isolated by slowly adding to 750 ml of water in a blender. The solid was isolated on a Buchner funnel. The solid was resuspended in fresh water (750 ml) with stirring for 20 minutes. Finally the product was isolated on a Buchner funnel and dried in a vacuum (< 1 mm Hg) oven (~ 40⁰C) to give a white solid (9.90 g, 86% yield)

EXAMPLE 14: Preparation of an amine functional Maltodextrin (MD-EAC-NH₇) MD-EAC-BOC (Example 13, 2.0 g, 5.31 mmole) and TFA (trifluoroacetic acid, 10 ml) was stirred for 2 hours. A gas evolution was observed indicative of BOC removal. The reaction solution was evaporated on a rotary evaporator to give a viscous residue (3.86 g; theoretical weight for the MD-EAC-NH₂ TFA salt is 2.08 g). Solubility testing indicated the water insoluble MD-EAC-BOC had been converted to the water soluble MD-EAC-NH₂ or the MD-EAC-NH₂ TFA salt.

EXAMPLE 15: Preparation of 2-isothiocvanato-l.l-dimethoxyethane (DME-NCS) DCC (ΛyV-dicyclohexylcarbodiimide, 9.68 g, 496.92 mmole), CS₂ (carbon disulfide, 23.9 g { 19 ml}, 313.9 mmole), and Et₂O (diethyl ether, 50 ml) were placed in a flask and cooled to -10° C. To the cold solution was added dropwise a solution of 2,2-dimethoxyethanamine (aminoacetaldehyde dimethylacetal, 5.00 g {5.2 ml}, 47.56 mmole) in Et₂O (40 ml), which was followed by a Et₂O (10 ml) rinse. The mixture was stirred overnight and allowed to warm to room temperature. The reaction mixture was filtered and the solid washed twice with Et₂O (50 ml). The Et₂O was evaporated using a rotary evaporator (~40°C @ 100 mm Hg). The residue was a liquid with solid present. The mixture was pipet filtered, rinsed with Et₂O (5 ml), and evaporated to give 6.8 g liquid. The liquid was distilled using a short path apparatus (144-1460 C @ 110 mm Hg) to give a main fraction of 5.83 g. NMR analysis at 400 MHz was consistent with the desired product: ¹H NMR (CDCl₃) methyne proton 4.58 (t, 1.00H), methylene protons 2.59 (d, 1.89H), and methoxy protons 3.44 (s, 5.69H)

EXAMPLE 16: Preparation of an aldehyde functional maltodextrin (MD-NCS- CHO)

MD-EAC-NH₂ (Example 14, 1 g, 3.61 mmole) is dissolved in water (5 ml). The pH is lowered to 3, if needed, to dissolve the polymer. The pH is then adjusted to 8. A solution of DME-NCS (Example 15, 1.47 g, 10 mmole) in THF (4 ml) is added to the aqueous MD-EAC-NH₂ solution in 4 equal portions, 5 minutes between additions with vigorous agitation. The pH of the reaction is adjusted to 7 and is placed in dialysis tubing (MWCO 1000), which is dialyzed against water for 24 hours. The purified solution is lyophilized to give the aldehyde functional maltodextrin.

Other embodiments of this invention will be apparent to those skilled in the art upon consideration of this specification or from practice of the invention disclosed herein. Various omissions, modifications, and changes to the principles and embodiments described herein may be made by one skilled in the art without departing from the true scope and spirit of the invention which is indicated by the following claims.

Claims

WHAT IS CLAIMED IS:

1. A biodegradable matrix material comprising the reaction product of: (a) an aminated natural biodegradable polysaccharide; and (b) an amine-reactive compound.

2. The biodegradable matrix material of claim 1, wherein the aminated natural biodegradable polysaccharide is prepared by a process comprising the steps of:

(a) providing a natural biodegradable polysaccharide;

(b) reacting at least a portion of hydroxyl groups that are present on the natural biodegradable polysaccharide with CDI to form a natural biodegradable polysaccharide comprising pendant imidazole groups; and

(c) reacting at least a portion of the pendant imidazole groups with an amine- containing compound to form the aminated natural biodegradable polysaccharide.

3. The biodegradable matrix material of claim 2, wherein the amine-containing compound comprises two or more primary amine groups.

4. The biodegradable matrix material of claim 3, wherein the two or more primary amine groups are separated by a linking group.

5. The biodegradable matrix material of claim 4, wherein the amine-containing compound comprises H₂N-R-NH₂, where R is a straight or branched chain alkyl linking group. 6. The biodegradable matrix material of claim 3, wherein the amine-containing compound comprises 1,

6-diaminohexane, 1,4-diaminobutane, 1,3-diaminopropane, and mixtures thereof.

7. The biodegradable matrix material of claim 1, wherein the aminated natural biodegradable polysaccharide has a degree of amine substitution ranging from about 0.1 to about 1.0.

8. The biodegradable matrix material of claim 1, wherein the aminated natural biodegradable polysaccharide has a degree of amine substitution ranging from about 0.2 to about 0.3.

9. The biodegradable matrix material of claim 1, wherein the natural biodegradable polysaccharide comprises polyalditol, amylose, maltodextrin, cyclodextrin, or a mixture thereof.

10. The biodegradable matrix material of claim 1 , wherein the natural biodegradable polysaccharide has a molecular weight of about 500,000 Da or less.

1 1. The biodegradable matrix material of claim 1 , wherein the natural biodegradable polysaccharide has a molecular weight of about 50,000 Da or less.

12. The biodegradable matrix material of claim 1, wherein the natural biodegradable polysaccharide has a molecular weight in the range of about 30,000 Da or less.

13. The biodegradable matrix material of claim 1 , wherein the natural biodegradable polysaccharide comprises a non-reducing polysaccharide.

14. The biodegradable matrix material of claim 13, wherein the non-reducing polysaccharide is polyalditol.

15. The biodegradable matrix material of claim 1, wherein the amine-reactive compound is prepared from a hydroxy-functional compound.

16. The biodegradable matrix material of claim 15, wherein the hydroxy- functional compound has at least two hydroxyl groups.

17. The biodegradable matrix material of claim 15, wherein the hydroxy- functional compound has from 2 to 4 hydroxyl groups.

18. The biodegradable matrix material of claim 15, wherein the hydroxy- functional compound has a molecular weight of about 10,000 Da or less.

19. The biodegradable matrix material of claim 15, wherein the hydroxy- functional compound is selected from the group consisting of poly(ethylene glycol), tetraethylene glycol, triethylene glycol, trimethylolpropane ethoxylate, and pentaerythritol ethoxylate.

20. The biodegradable matrix material of claim 19, wherein the hydroxy- functional compound is poly(ethylene glycol) having the structure HO-(CH₂-CH₂- O)_n-H, where n ranges from about 3 to about 150.

21. The biodegradable matrix material of claim 20, wherein the poly(ethylene glycol) has a number average molecular weight ranging from about 100 to about 5000 Da.

22. The biodegradable matrix material of claim 1, wherein the amine-reactive compound comprises functional groups selected from aldehyde, isothiocyanate, bromoacetyl, chloroacetyl, iodoacetyl, anhydride, imidazole carbamate, isocyanate, maleimide, and combinations thereof.

23. The biodegradable matrix material of claim 1, wherein the amine-reactive compound is an imidazole carbamate formed by reacting a hydroxy functional compound with CDI.

24. The biodegradable matrix material of claim 1 , wherein the matrix is formed by reacting the aminated natural biodegradable polysaccharide and the amine- reactive compound at a ratio amine groups to amine-reactive groups ranging from about 1 : 1 to about 5: 1.

25. The biodegradable matrix material of claim 1, wherein the pH of the matrix material ranges from about 7.5 to about 9.5.

26. The biodegradable matrix material of claim 1, wherein the matrix material is enzymatically degradable.

27. The biodegradable matrix material of claim 1, wherein the matrix material is degradable in vivo.

28. An implantable medical device comprising the biodegradable matrix material of claim 1.

29. The implantable medical device of claim 28, wherein the device is an implant, coating, in-situ formed matrix, stent, tube, or aneurysm coil.

30. The implantable medical device of claim 29, wherein the device comprises one or more bioactive agents or cells.

31. A tissue sealant comprising the biodegradable matrix material of claim 1.