CN110448308B

CN110448308B - Implantable sensor and preparation method thereof

Info

Publication number: CN110448308B
Application number: CN201910657121.6A
Authority: CN
Inventors: 陈玮; 杨清刚; 张文伶; 胡一川
Original assignee: Hangzhou Weice Biotechnology Co ltd
Current assignee: Hangzhou Weice Biotechnology Co ltd
Priority date: 2019-07-19
Filing date: 2019-07-19
Publication date: 2023-03-10
Anticipated expiration: 2039-07-19
Also published as: CN110448308A

Abstract

The invention provides an implanted sensor which has the advantages of small volume, high sensitivity, long service life, safety, no toxicity and convenience for large-scale production. The implantable sensor comprises a shell, a detection circuit and a detection electrode, wherein the detection circuit is sealed in the shell, the detection electrode is arranged on the outer surface of the shell and is attached to the outer surface of the shell, and the detection electrode is electrically connected with the detection circuit. The detection electrode is spirally wound on the outer surface of the shell; alternatively, the detection electrodes are arranged in parallel on the outer surface of the housing.

Description

Implantable sensor and preparation method thereof

Technical Field

The invention relates to the field of electrochemical detection, in particular to an implantable sensor and a preparation method thereof.

Background

Implantable sensors are capable of continuously measuring certain time-varying important physiological or pathological parameters in the body, such as the concentration of oxygen, glucose, lactate, etc., to achieve a more direct and accurate diagnostic or therapeutic effect. In order to reduce the risk of infection and rejection at the site of implantation, implantable sensors are typically small in size, thereby reducing the area of direct contact of the sensor with the tissue. However, the small size limits the effective sensing area of the sensor, resulting in low sensitivity, poor signal-to-noise ratio, and poor stability; moreover, the smaller size tends to result in insufficient enzyme immobilization on the electrode surface, further affecting the sensitivity and stability of the sensor.

To improve the sensitivity of the sensor, two general approaches are used, one is to use a more sensitive enzyme. For example, in the field of blood glucose testing, blood glucose testing may be performed using fluorescent polymers that are sensitive to blood glucose concentration, which may enable high sensitivity in small-volume implantable sensors. However, fluorescent polymers are toxic, product structure must be tightly controlled, and the stability of the fluorescent signal is susceptible to photobleaching, pH, background autofluorescence, and degradation of bioactive oxygen species. And the other method is to design the structure of the implantable sensor to increase the effective sensing area of the detection electrode and the enzyme immobilization amount. For example, chinese patent 201510682823.1 discloses a long-life implantable glucose sensor for continuous blood glucose monitoring, which adopts a spiral platinum-iridium alloy electrode to carry glucose oxidase, so as to increase the carrying amount of the glucose oxidase. The disadvantages of this patent are: 1. the sensor is actually a semi-implanted sensor, can not be completely embedded in biological tissues, and an opening needs to be reserved on the surface of the tissues for connecting an electrode of the sensor with an external detection circuit; during use, the opening in the tissue surface is subject to pulling and difficult healing, and both the implant site and the prepared opening in the tissue surface are subject to a greater risk of infection. Moreover, the service life of the common semi-implantable sensor is generally not longer than 14 days, and the sensor is frequently replaced, so that the sensor has great influence on the tissues around the sensor and the sensitivity of the sensor, and the long-term implantation and use of the sensor are not facilitated. 2. The platinum iridium wire needs to be manually wound on the syringe needle to form a spiral pore channel structure of the platinum iridium wire, the preparation process is uncontrollable, the product consistency is poor, and the large-scale production is not facilitated; during the winding process, the platinum iridium wire generates larger internal stress and deformation, and the sensitivity of the sensor is influenced. 3. The platinum iridium wire is expensive, and the prepared sensor is also high in price.

Disclosure of Invention

Aiming at the problems, the invention provides an implantable sensor which has the advantages of small volume, high sensitivity, long service life, safety, no toxicity and convenience for large-scale production.

The implantable sensor is characterized by comprising a shell, a detection circuit and a detection electrode, wherein the detection circuit is sealed in the shell, the detection electrode is arranged on the outer surface of the shell and is attached to the outer surface of the shell, and the detection electrode is electrically connected with the detection circuit. Preferably, the detection electrode is spirally wound on the outer surface of the shell; alternatively, the detection electrodes are arranged in parallel on the outer surface of the housing. Preferably, when the detection electrodes are arranged in parallel on the outer surface of the shell, the axes of the detection electrodes are parallel to the axis of the shell. Preferably, the detection electrode is fixedly connected with the outer surface of the shell.

Shell body

Further, the outer surface of the case has a recess for accommodating the detection electrode. Preferably, the grooves are helical or strip-shaped. Preferably, the depth of the groove is greater than or equal to the thickness of the detection electrode. Preferably, the depth of the groove is 150 to 200 μm.

Further, the shell is integrally formed; alternatively, the housing may be formed from two or more pieces. Preferably, when two or more components are joined, the two or more components are sealingly connected to each other. Preferably, the housing is made of metal or a polymer material. Preferably, the metal is titanium, a titanium alloy, a cobalt-based alloy or stainless steel. Preferably, the polymer material is selected from one or more of polymethyl methacrylate, polycarbonate, polyethylene, polypropylene and polytetrafluoroethylene.

Detection electrode

Further, the detection electrode is a flexible electrode. Preferably, the detection electrode has a thickness of 75 to 125 μm.

Furthermore, the detection electrode comprises a working electrode and a reference electrode, the working electrode and the reference electrode are respectively provided with a corresponding groove, and the working electrode and the reference electrode are respectively positioned in the corresponding grooves; alternatively, the working electrode and the reference electrode are located in the same recess. Preferably, the working electrode is arranged parallel to the reference electrode.

Connecting piece

The invention also provides a connecting piece for connecting the detection circuit and the detection electrode, which has simple structure and convenient use, can realize reliable connection between the detection circuit and the detection electrode, and is convenient for the disassembly and assembly of the detection circuit and the detection electrode.

A connecting piece comprises a body and a conductive element, wherein the body is provided with a slot and a through hole, the slot is communicated with the through hole, the conductive element is arranged in the through hole, two ends of the conductive element are exposed out of the through hole, one end of the conductive element is positioned in the slot, and the other end of the conductive element is positioned outside the body. Preferably, the conductive element is secured within the through hole. Preferably, the through holes are two or more, and the two or more through holes are positioned on the same side of the slot. Preferably, the body is an integrally formed silicone piece. Preferably, the length of the body is 5 to 10mm.

Furthermore, the body is provided with a through screw hole which is arranged to avoid the through hole. And the detection circuit board is provided with a mounting hole aligned with the screw hole, and the bolt passes through the screw hole and is inserted into the mounting hole of the detection circuit board to realize the fixed connection of the connecting piece and the detection circuit board. Preferably, there are two or more screw holes.

Further, the body includes base and clamp plate, and the clearance between clamp plate and the base forms the slot, and on the base was located to the through-hole, the one end of clamp plate was the link with base fixed connection, the other end of clamp plate was the free end, and the free end and the base of clamp plate can be dismantled and be connected. Preferably, the distance between the pressure plate and the base is smaller than or equal to the thickness of the detection electrode. Preferably, the base and the platen are parallel.

Furthermore, the screw hole comprises a first screw hole arranged at the free end of the pressing plate and a second screw hole arranged on the base, and the first screw hole is aligned to the second screw hole. Preferably, the screw hole further comprises a third screw hole arranged at the connecting end of the pressure plate.

Further, the conductive element is conductive rubber, a spring probe or a metal buckle.

Biocompatible outer membrane and hydrophilic membrane

Furthermore, the outer surface of the shell is coated with a biocompatible outer membrane, and the detection electrode is positioned between the outer surface of the shell and the biocompatible outer membrane. The outer membrane with biocompatibility is coated on the outer surface of the whole shell, so that the biocompatibility of the sensor is improved. Preferably, the biocompatible outer membrane is coated with a hydrophilic membrane. Preferably, the biocompatible outer membrane is selected from one or more of polyurethane, silicone rubber polymer and polyethylene glycol. Preferably, the hydrophilic membrane is a zwitterionic polymer derivative.

The invention also provides a method for preparing the implantable sensor.

A method of making an implantable sensor, comprising the steps of:

s1, preparing a detection electrode by adopting an MEMS (Micro-Electro-Mechanical System) process;

s2, connecting a detection electrode and a detection circuit;

s3, preparing a shell, and packaging the detection circuit in the shell;

and S4, fixing the detection electrode on the outer surface of the shell, and enabling the detection electrode to be attached to the outer surface of the shell.

Further, the specific process of S3 is: placing the detection circuit into a shell mold, and performing injection molding on the shell; or, each part of the shell is respectively molded, each part is assembled, the detection circuit is packaged in the shell, and then the splicing part of each part is sealed. Preferably, the joints between the components are sealed by ultrasonic welding or by sealing and bonding with a sealant.

Further, the preparation method further comprises coating an outer film: preparing an outer membrane liquid, completely immersing the shell, the detection circuit sealed in the shell and the detection electrode arranged on the outer surface of the shell into the outer membrane liquid, and then lifting and airing. Preferably, the coating of the outer film is repeated 2 to 3 times.

Further, the preparation method further comprises coating a hydrophilic film: preparing hydrophilic membrane liquid, completely immersing the shell, the detection circuit sealed in the shell and the detection electrode arranged on the outer surface of the shell into the hydrophilic membrane liquid, lifting and airing. Preferably, the coating of the hydrophilic membrane is repeated 2 to 3 times.

The invention has the beneficial effects that:

1. the detection electrode is arranged on the outer surface of the shell, has larger installation space, and can properly increase the size of the detection electrode according to the requirement, thereby being beneficial to increasing the effective sensing area on one hand and increasing the enzyme fixing amount on the other hand, and further improving the sensitivity of the sensor; in addition, because the installation space of the detection electrode is large, the flexible electrode which can be industrially produced in a large scale can be suitable for the implanted sensor, and the consistency of products is facilitated.

2. Detection electrode installs at the casing surface, detection circuitry encapsulates within the casing, also namely through the design of casing, and detection electrode can install outside detection circuitry, realizes detection electrode and detection circuitry's range upon range of, during the use, the implanted sensor is embedded in the tissue completely and whole volume reduces to reduce and implant wound area, reduce wound infection risk, improve sensor life.

3. The connecting piece is used for connecting the detection circuit and the detection electrode, has a simple structure, is convenient to use, and is convenient for assembling and disassembling the detection circuit and the detection electrode.

Drawings

Fig. 1 is a schematic external view of an implantable sensor according to an embodiment of the invention.

Fig. 2 isbase:Sub>A sectional view taken along linebase:Sub>A-base:Sub>A of fig. 1.

Fig. 3 is an enlarged view of fig. 2 at B.

FIG. 4 is a circuit diagram of the components of the detection circuit according to one embodiment of the present invention.

Fig. 5 is a schematic view of a housing recess in one embodiment of the invention.

FIG. 6 is a schematic view of the connection of the sensing electrode to the recess of the housing in one embodiment of the present invention.

Fig. 7 is a schematic view of the connection of the detection electrode to the recess of the housing in another embodiment of the present invention.

Figure 8 is a schematic view of a connector according to an embodiment of the present invention.

Figure 9 is a schematic illustration of another angle of the connector in accordance with an embodiment of the present invention.

Fig. 10 is a schematic view of a connector body according to one embodiment of the present invention.

FIG. 11 is a schematic diagram of the connection of the detection circuit, the connection member, and the detection electrode according to an embodiment of the present invention.

FIG. 12 is a schematic representation of the outer membrane and hydrophilic membrane in one embodiment of the present invention.

Fig. 13 is a schematic illustration of the first and second parts of the housing in an embodiment of the invention.

Fig. 14 is a perspective view of the first member of fig. 13.

Fig. 15 is a perspective view of the first member of fig. 13 from another angle.

Figure 16 is a cross-sectional view of the first member of figure 13.

Fig. 17 is a perspective view of the second member of fig. 13.

FIG. 18 is a graph of current versus time for an implantable sensor for chronoamperometry to detect blood glucose, in accordance with an embodiment of the present invention.

FIG. 19 is a linear plot of glucose concentration versus current obtained by an implantable sensor detecting blood glucose in one embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to specific examples.

The small-volume fully-implanted sensor has low sensitivity due to small effective sensing area and insufficient enzyme immobilization amount; in order to increase the sensitivity of the sensor and increase the length and width of the electrode, the volume of the sensor is increased, a larger wound is caused when the sensor is implanted into tissues, the infection risk at the implanted part is increased, the discomfort of a patient is caused, and the service life of the sensor is influenced. In view of the above problems, the present invention designs the structure of an implantable sensor.

An implantable sensor, as shown in fig. 1 and fig. 2, includes a housing 1, a detection circuit 2 and a detection electrode 3, wherein the detection circuit 2 is sealed in the housing 1, the detection electrode 3 is mounted on the outer surface of the housing 1 and attached to the outer surface of the housing 1, and the detection electrode 3 is electrically connected to the detection circuit 2. The detection electrode comprises a working electrode and a reference electrode, and the detection electrode acquires an electric signal generated by electrochemical reaction. The detection circuit applies voltage to the detection electrode and transmits an electric signal acquired by the detection electrode to an external receiver, and the external receiver converts the electric signal into detection data; alternatively, the detection circuit converts the electrical signal into detection data and transmits the detection data to a receiver outside the body. The test data may be, for example, blood glucose data. The receiver outside the body receives the electric signal or detection data transmitted by the detection circuit, so as to observe and analyze the detection result. The external receiver being, for example, a web sitehttp:// www.glysens.com/product/Provided is an extracorporeal receiver. Because the detection circuit is sealed in the shell, the detection circuit can not be in direct contact with biological tissues, and the interference of the biological tissues to the detection circuit is avoided. The detection electrode is mounted on the outer surface of the casing, for example, spirally wound on the outer surface of the casing or arranged in parallel with the outer surface of the casing. When the detection electrodes are arranged in parallel on the outer surface of the housing, the axes of the detection electrodes are parallel to the axis of the housing, as shown in fig. 5, for example. The entire outer surface of the housing is used forThe detection electrode is installed, and the size of the detection electrode is increased without causing obvious increase of the volume of the sensor; and the size, such as length and width, of the detection electrode is increased, so that the effective sensing area and the enzyme immobilization amount of the sensor can be directly and effectively increased, and the sensitivity and the detection stability of the sensor are improved. In some embodiments, the working electrode can be up to 10mm in length and 0.5 to 1mm in width.

Shell body

The shell is used for sealing the detection circuit and simultaneously used for installing the detection electrode.

In some embodiments, as shown in fig. 3, the outer surface of the housing 1 has a recess 101 for accommodating the detection electrode 3. Therefore, the detection electrode is arranged in the groove, and the influence of the arrangement of the detection electrode on the whole volume of the sensor is further reduced; even in some embodiments, the mounting of the detection electrode does not add to the overall volume of the sensor at all, since the depth of the recess is greater than or equal to the thickness of the detection electrode. For example, the thickness of the detection electrode is 75 to 125 μm, and the depth of the groove is 150 to 200 μm. In some embodiments, the grooves are helical, and the detection electrodes are helically wound around the outer surface of the housing, such as shown in fig. 1; alternatively, the grooves are strip-shaped, for example, as shown in fig. 5, the detection electrodes are arranged on the outer surface of the housing, and the arrangement manner of the detection electrodes on the outer surface of the housing is the same as the shape of the grooves.

In some embodiments, the housing is integrally formed; alternatively, the housing may be formed by joining two or more members, for example, as shown in fig. 13 to 17, and the housing may be assembled by assembling the first member 10 and the second member 11. When the casing integrated into one piece, can be earlier with detection circuitry and detection electrode connection, then detection circuitry puts into the casing mould, carries out injection moulding to the casing at last. After the injection molding liquid is solidified, the detection circuit is encapsulated in the shell, and the detection electrode is positioned outside the shell. When the shell is formed by splicing two or more parts, the two or more parts are connected hermetically, and the detection circuit is sealed in the shell. The sealing connection mode can be that the spliced positions of a plurality of parts are subjected to ultrasonic welding, or the spliced positions are sealed by using sealing glue.

In some embodiments, the housing is made of a metal or polymeric material. The metal may be titanium, a titanium alloy, a cobalt-based alloy or stainless steel. In some embodiments, the polymer material is selected from one or more of polymethyl methacrylate, polycarbonate, polyethylene, polypropylene and polytetrafluoroethylene.

Detection circuit

Fig. 4 is a circuit connection diagram of each component in the detection circuit, which is the circuit connection diagram disclosed in fig. 3 of the use of Electrochemical Impedance Spectroscopy (EIS) in continuous glucose monitoring in chinese patent 201480075588.5. The detection circuit may be a circuit integrated on a Printed Circuit Board (PCB) 201, the detection circuit comprising a micro battery 202, a wireless transmission device 203 and an IC chip 204, for example as shown in fig. 2. The IC chip integrates the functions of analog signal processing, a power management module, a blood sugar test module and a communication module. The detection circuit and the detection electrode are electrically connected by a connection member 4.

The wireless transmitting device 203 of the detection circuit is in communication connection with the external receiver, and the detection circuit transmits the electric signals or the detection data to the external receiver through the wireless transmitting device, so that the real-time detection of the internal data is realized. The wireless transmission means may be an antenna, such as shown in fig. 2.

In some embodiments, the micro battery is rechargeable. The outside is provided with a wireless energy supply device capable of charging the micro battery. Wireless functional devices, e.g. websiteshttps://www.cambridgeconsultants.com/maglenseThe provided wireless function device, or chinese patent 2011100799364, is used for a wireless charging method of an implanted medical device and a wireless energy supply device provided by a wireless charging device.

The detection circuit enables the implanted sensor to independently complete detection without being connected with an external device, and the detection circuit is in communication connection with an external receiver through the wireless transmitting device, so that the implanted sensor can be completely embedded in tissues without reserving an opening on the surfaces of the tissues, and the risk of wound infection is further reduced.

Detection electrode

The detection electrode collects an electric signal generated by the electrochemical reaction. For example, when detecting the blood glucose concentration, glucose oxidase is fixed on the working electrode, when the glucose in the blood is converted into gluconic acid under the catalytic action of the glucose oxidase, hydrogen peroxide which is an electroactive reaction product is generated at the same time, the hydrogen peroxide is diffused inwards to reach the surface of the working electrode to form electrode current, the current detected by the working electrode is in direct proportion to the glucose concentration, and the glucose concentration can be detected by detecting the current.

In some embodiments, the detection electrode is fixedly connected to the outer surface of the housing. For example, the detection electrode may be bonded to an outer surface of the case.

In some preferred forms, the detection electrode is a flexible electrode. The detection electrode can be shaped with the groove, for example, spirally wound on the outer surface of the shell along with the groove.

The detection electrode 3 includes at least a working electrode 301 and a reference electrode 302. The working electrode 301 includes a substrate 3011, a lead layer 3012, an electrode layer 3013 and an enzyme layer 3014, when the working electrode is adhered on the outer surface of the housing, the substrate 3011 is in contact with and adhered to the outer surface of the housing 1, and the lead layer 3012, the electrode layer 3013 and the enzyme layer 3014 are far from the outer surface of the housing 1 relative to the substrate 3011, as shown in fig. 6 or fig. 7, for example. Reference electrode 302 includes substrate 3021, lead layer 3022, and electrode layer 3023, where when reference electrode 302 is bonded to the outer surface of case 1, substrate 3021 contacts and adheres to the outer surface of case 1, and lead layer 3022 and electrode layer 3023 are located away from the outer surface of the case relative to the substrate, as shown in fig. 6 or 7, for example.

The working electrode 301 and the reference electrode 302 are independent of each other, as shown in fig. 7, for example; alternatively, the working electrode 301 and the reference electrode 302 are integrated on the same substrate, such as shown in fig. 6. When the working electrode 301 and the reference electrode 302 are independent from each other, the working electrode 301 and the reference electrode 302 may have respective corresponding recesses, for example, as shown in fig. 7, the recess 101 includes a first recess 1011 for accommodating the working electrode and a second recess 1012 for accommodating the reference electrode, the working electrode 301 is located in the first recess 1011, and the reference electrode 302 is located in the second recess 1012; alternatively, the working electrode 301 and the reference electrode 302 may be located in the same recess. When the working electrode and the reference electrode are integrated on the same substrate, the working electrode 301 and the reference electrode 302 are located in the same recess, for example, as shown in fig. 3 or fig. 7. In some preferred forms, the working electrode is arranged parallel to the reference electrode, for example as shown in figures 3, 6 and 7.

In some embodiments, the detection electrode further comprises a counter electrode 303. The counter electrode includes a base 3031, a wire layer 3032, and an electrode layer 3033. The counter electrode may be independent of the working and reference electrodes, such as shown in fig. 7; alternatively, the counter, working and reference electrodes are integrated on the same substrate, such as shown in fig. 6. Likewise, when the counter electrode is separate from the working and reference electrodes, the counter electrode can have corresponding recesses, that is, recess 101 further includes a third recess 1013 for receiving the counter electrode, the counter electrode 303 being located within the third recess 1013, such as shown in fig. 7; alternatively, the counter electrode may be located in the same recess as the working and/or reference electrodes. When the counter electrode, working electrode, and reference electrode are integrated on the same substrate, the counter electrode, working electrode, and reference electrode are located in the same recess, as shown in fig. 6, for example. In some preferred forms, the counter electrode, working electrode and reference electrode are arranged in parallel, for example as shown in fig. 6 or fig. 7.

In some embodiments, the detection electrode comprises a blank electrode 304. The blank electrode has a substrate 3041, a lead layer 3042, and an electrode layer 3043. The blank electrode may be independent of the working and reference electrodes, such as shown in fig. 7; alternatively, the blank electrode, the working electrode, and the reference electrode are integrated on the same substrate, such as shown in fig. 6. Likewise, when the blank electrode is separate from the working electrode and the reference electrode, the blank electrode can have corresponding recesses, that is, the recess 101 further includes a fourth recess 1014 for receiving the blank electrode, the blank electrode 304 being located within the fourth recess 1014, such as shown in fig. 7; alternatively, the blank electrode may be located in the same recess as the working electrode and/or the reference electrode. When the blank electrode, the working electrode and the reference electrode are integrated on the same substrate, the blank electrode, the working electrode and the reference electrode are located in the same groove, as shown in fig. 6, for example. The blank electrode, the working electrode, and the reference electrode may be arranged in parallel, for example, as shown in fig. 6 and 7.

In some embodiments, the detection electrode can include both a working electrode, a reference electrode, a counter electrode, and a blank electrode. The working electrode, the reference electrode, the counter electrode and the blank electrode can be mutually independent and can also be integrated on the same substrate; can be positioned in the corresponding grooves or positioned in the same groove. The working electrode, the reference electrode, the counter electrode and the blank electrode are arranged in parallel.

Connecting piece

When the detection circuit is a circuit printed on an integrated circuit board, the detection electrode is connected with the detection circuit in a crimping mode.

A connecting piece 4 for connecting a detection circuit and a detection electrode is disclosed, for example, as shown in FIGS. 8-10, which comprises a body 401 and a conductive element 402, wherein the body 401 is provided with a slot 4011 and a through hole 4012, the slot 4011 is communicated with the through hole 4012, the conductive element 402 is arranged in the through hole 4012, two ends of the conductive element 402 are exposed out of the through hole, one end of the conductive element 402 is positioned in the slot 4011, and the other end of the conductive element 402 is positioned outside the body 401. The slot is used for inserting the detection electrode. The detection electrode has a lead layer. When the connector is used, the detection electrode is first inserted into the slot, and the lead layer of the detection electrode is electrically contacted with one end of the conductive element located in the slot, as shown in fig. 11; then, the connecting member is fixed to a circuit board (hereinafter referred to as "detection circuit board") integrated with a detection circuit, and one end of the conductive member located on the body is electrically contacted with the detection circuit, that is, both ends of the conductive member are respectively contacted with the detection electrode and the detection circuit, thereby achieving the electrical connection of the detection electrode and the detection circuit. Because the detection electrode receives certain extrusion force when inserting the slot, in order to reduce the damage of connecting piece to the detection electrode, in some embodiments, the body of connecting piece is the silica gel spare. In addition, the implantable sensor completely embedded in the tissue provided by the invention is small in volume, so that the volume of the connector body is relatively small. In some embodiments, the length of the body is 5 to 10mm.

The detection electrode 3 at least comprises a working electrode and a reference electrode, a detection circuit is integrated on the circuit board 5, and the detection circuit comprises a terminal 501 for connecting the detection electrode. The working and reference electrodes each have a respective terminal and conductive element through which they are electrically connected, such as shown in fig. 11. Accordingly, there are at least two through holes provided with conductive elements. Because the detection circuit is integrated on the circuit board, and the circuit board is positioned on the same side of the connecting piece when the connecting piece is fixed on the circuit board, the at least two through holes are positioned on the same side of the slot. In some embodiments, the detection electrode further comprises a blank electrode and/or a counter electrode, the blank electrode and the counter electrode also have respective corresponding terminals and conductive elements, and the blank electrode and the counter electrode are electrically connected with the respective terminals through the respective conductive elements, for example, as shown in fig. 11, when the through holes should be provided in plurality. When multiple or multiple detection electrodes are integrated on the same substrate, the spacing between the multiple detection electrodes can be designed to be equal to the spacing between the conductive elements, so that when the detection electrodes are inserted into the slots, the alignment between the detection electrodes and the conductive elements is facilitated, as shown in fig. 11. When the plurality of detection electrodes are independent, the detection electrodes are inserted into the slots and aligned with the conductive elements and the detection circuits.

The connecting piece can be fixed on the detection circuit board in an adhesive mode. In the present invention, in order to detachably connect the connector and the detection circuit board, a screw hole is formed through the body 401. Through means that the screw hole penetrates through the body. The detection circuit board is provided with a mounting hole aligned with the screw hole, and the connecting piece and the detection circuit board are fixed when the bolt passes through the screw hole and is screwed into the mounting hole; when the bolt is disassembled, the connecting piece is separated from the detection circuit board. The screw hole avoids the through hole to set up, avoids the bolt to cause the interference to the through hole, influences detection electrode and detection circuitry's being connected. In some embodiments, there are two or more screw holes.

In order to ensure that the detection electrode is not easy to be separated after being inserted into the slot, a pressing structure for pressing the detection electrode can be arranged on the body. In some embodiments, for example as shown in fig. 8 or fig. 9, the body includes a base 6 and a pressing plate 7 connected to each other, the pressing plate 7 is located on the base 6, a gap between the pressing plate 7 and the base 6 forms a slot, a through hole is formed in the base 6, one end of the pressing plate 7 is a connection end fixedly connected to the base 6, the other end of the pressing plate 7 is a free end, and the free end of the pressing plate 7 is detachably connected to the base 6. Therefore, a U-shaped slot is formed between the pressing plate and the base, and the U-shaped slot is convenient for the insertion of the detection electrode. And after the detection electrode is inserted into the slot between the base and the pressing plate, the free end of the pressing plate is connected with the base, and the detection electrode is pressed tightly. In some embodiments, the spacing between the platen 7 and the base 6 is less than or equal to the thickness of the detection electrode. In some embodiments, the base 6 and platen 7 are parallel, such as shown in fig. 8. So, detecting electrode can laminate with base and clamp plate better, and base and clamp plate can have better effect that compresses tightly to detecting electrode.

In order to facilitate the disassembly and assembly of the connecting piece and the detection electrode, the free end of the pressing plate is detachably connected with the base. The detachable connection between the free end of the pressing plate and the base can be realized by arranging a first screw hole 4013-1 at the free end of the pressing plate and arranging a second screw hole 4013-2 aligned with the first screw hole 4013-1 at the base, for example, as shown in fig. 8. After the detection electrode is inserted into the slot, the bolt sequentially penetrates through the first screw hole and the second screw hole and is screwed down, so that the free end of the pressing plate is connected with the base, and the detection electrode is tightly pressed in the slot. In addition, a first mounting hole aligned with the first screw hole and the second screw hole may be provided on the detection circuit board. The bolt passes first screw and second screw in proper order, inserts first mounting hole, can also realize connecting piece and detection circuitry board fixed connection and can dismantle the connection.

To increase the security of the connection of the connector to the test circuit board, in some embodiments, the press plate connection end is further provided with third screw holes 4013-3, such as shown in FIG. 8. The third screw hole is also a screw hole penetrating through the connector body. The detection circuit board can be provided with a second mounting hole aligned with the third screw hole, and the bolt sequentially penetrates through the third screw hole, is inserted into the second mounting hole and is connected with the connecting piece and the detection circuit board.

The detection circuit and the detection electrode are electrically connected by a conductive element, which in some embodiments may be a conductive rubber, a spring probe, or a metal snap. The conductive element may be secured within the through hole by an adhesive or interference fit. For example, the conductive rubber can be in a football shape with a large middle part and small two ends, and when the conductive rubber is plugged into the through hole, the middle part of the conductive rubber is deformed and is in interference fit with the through hole, so that the conductive rubber is fixed in the through hole. Or coating an adhesive on the inner wall of the through hole, wherein when the conductive element is inserted into the through hole, the adhesive fixes the conductive element in the through hole.

Biocompatible outer and hydrophilic membranes

When the sensor is implanted in tissue, if the housing and the detection electrode are in direct contact with the tissue, allergic reactions and rejection reactions in the tissue are easily caused. To increase the biocompatibility of the implantable sensor, in some embodiments, the outer surface of the housing is coated with a biocompatible outer membrane, and the detection electrodes are positioned between the outer surface of the housing and the biocompatible outer membrane. That is to say, the biocompatible outer membrane is coated outside the shell and the detection electrode, when the implantable sensor is implanted into tissues, the shell and the detection electrode are not in direct contact with the tissues, so that the rejection reaction is reduced, the possibility of cell proliferation outside the implantable sensor is reduced, and the in-vivo performance of the implantable sensor is improved. In some embodiments, the biocompatible outer membrane is selected from one or more of polyurethane, silicone rubber polymer, polyethylene glycol.

In some embodiments, the biocompatible outer membrane is coated with a hydrophilic membrane. The hydrophilic membrane is a zwitterionic polymer derivative. The hydrophilic membrane is one or more of zwitterionic polymer derivatives, such as methacryloyloxyethyl phosphorylcholine polymer, zwitterionic polymer containing sulfobetaine, and zwitterionic polymer containing carboxyl betaine.

Preparation method of implantable sensor

The preparation method of the implantable sensor comprises the following steps:

s1, preparing a detection electrode by adopting a micro-electro-mechanical system (MEMS) process. The detection electrode comprises a working electrode and a reference electrode, and in some modes, the detection electrode also comprises a blank electrode and/or a counter electrode. The working electrode, the reference electrode, the blank electrode and the counter electrode respectively comprise a flexible substrate, a lead layer and an electrode layer which are sequentially overlapped. The working electrode is also laminated with an enzyme layer on the electrode layer. The flexible substrate may be polyimide. The wire layer may be copper, gold or platinum. The electrode layers of the working electrode and the blank electrode are platinum; the electrode layer of the reference electrode was silver/silver chloride.

The MEMS preparation process of the detection electrode specifically includes preparation of a lead layer, preparation of an electrode layer, and preparation of an enzyme layer, which are described in detail below.

Preparing a wire layer: generating a metal layer on the substrate modified by the plasma by adopting an electron beam evaporation method or a sputtering deposition method; then spin-coating photoresist on the metal layer and drying; placing a mask plate with the shape and the size consistent with those of the required conductor layer, carrying out exposure treatment, and then developing the exposed photoresist; etching the exposed area by a dry etching or wet etching process; and removing the residual photoresist to obtain the required conductor layer. The thickness of the conducting layer can be adjusted according to the flexibility requirement of the device. And finally, adhering a polyimide insulating film, wherein the polyimide insulating film is provided with a window for exposing the electrode, thereby completing the preparation of the electrode. The window exposes the effective detection part, and other conducting wire parts need to be insulated, otherwise, the short circuit is easy to occur when the window is implanted into a body.

Preparing an electrode layer: when a platinum layer is required to be deposited on the working electrode as an electrode layer, constant current electroplating is carried out through a three-electrode system of the electrochemical workstation, the flexible electrode, ag/AgCl as a reference electrode and a platinum net as a counter electrode are immersed into a platinum plating solution, the working electrode to be electroplated is connected to the working electrode of the electrochemical workstation, ag/AgCl is connected to the reference electrode of the electrochemical workstation, and the platinum net is connected to the counter electrode of the electrochemical workstation. And a certain current is continuously applied, so that a platinum layer can be deposited on the conducting layer of the working electrode.

When a silver/silver chloride layer is required to be deposited on the reference electrode as an electrode layer, constant current electroplating is carried out through a three-electrode system of the electrochemical workstation, the flexible electrode, ag/AgCl as a reference electrode and a platinum net as a counter electrode are immersed into silver plating solution, the reference electrode to be electroplated is connected to the working electrode of the electrochemical workstation, the Ag/AgCl is connected to the reference electrode of the electrochemical workstation, and the platinum net is connected to the counter electrode of the electrochemical workstation. And continuously applying a certain current to deposit a silver layer on the conductive layer of the reference electrode. And (3) after the reference electrode is cleaned, the silver plating solution is changed into a potassium chloride solution, and a certain current is continuously applied to obtain the Ag/AgCl reference electrode.

There are two methods for preparing the enzyme layer. The first method is to prepare an enzyme layer on the electrode layer after the electrode layer of the working electrode is prepared. The specific process can be as follows: transferring enzyme solution of glucose oxidase and bovine serum albumin BSA onto an electrode layer of a working electrode in a spraying and coating mode, naturally airing for 5-15 min, then crosslinking and fixing the glucose oxidase transferred to the working electrode by using glutaraldehyde solution with the concentration of 5-20% at the temperature of 25-37 ℃, adopting liquid-phase dipping crosslinking or gas-phase crosslinking for 30-45 min, and repeating the crosslinking step for 3 times. Finally, an enzyme layer covering the electrode layer is obtained. The second method is to prepare the enzyme layer at the same time as the electrode layer, and the specific process can be as follows: and immersing the flexible electrode, ag/AgCl serving as a reference electrode and a platinum net serving as a counter electrode into the working solution, connecting the working electrode to be electroplated to the working electrode of the electrochemical workstation, connecting the Ag/AgCl to the reference electrode of the electrochemical workstation, and connecting the platinum net to the counter electrode of the electrochemical workstation. The working solution is 0.1MPB buffer solution containing chloroplatinic acid, dopamine and glucose oxidase. Continuously applying a certain potential (-0.6 to-0.4V) for 30min to obtain the working electrode covered with the enzyme layer.

The flexible detection electrode is prepared by the MEMS process, the process is controllable, the electrode with the required length and width can be prepared, and large-scale production can be carried out. In the preparation process, when the mask for preparing the lead layer is designed to be coplanar, the preparation of a plurality of detection electrodes can be directly completed by single photoetching, the efficiency is high, and the problems caused by the integration and alignment of a subsequent working electrode, a reference electrode, a blank electrode and a counter electrode are avoided.

And S2, connecting the detection electrode with a detection circuit. The detection electrode comprises a working electrode, a reference electrode, a blank electrode and a counter electrode. The working electrode, the reference electrode, the blank electrode and the counter electrode can be independent of each other or can be integrated on the same substrate.

When the working electrode, the reference electrode, the blank electrode and the counter electrode are independent from each other, the working electrode, the reference electrode, the blank electrode and the counter electrode are respectively connected with a circuit by connecting pieces, as shown in fig. 7; or the working electrode, the reference electrode, the blank electrode and the counter electrode are connected with a circuit by a connecting piece, as shown in fig. 8.

When the working electrode, the reference electrode, the blank electrode and the counter electrode are integrated on the same substrate, the working electrode, the reference electrode, the blank electrode and the counter electrode form an integrated electrode, the integrated electrode is connected with a circuit through a connecting piece, and the working electrode, the reference electrode, the blank electrode and the counter electrode are respectively connected with the circuit through the connecting piece, as shown in fig. 9.

And S3, preparing a shell, and packaging the detection circuit in the shell. The specific process of step S2 is: placing the detection circuit into a shell mold, filling feed liquid, performing injection molding on the shell, solidifying the feed liquid to form a hollow or solid shell, and encapsulating the detection circuit; or, each part of the shell is respectively molded, each part is assembled, the detection circuit is packaged in the shell, and the splicing positions of each part are sealed. The sealing mode of the splicing part among all the parts can be ultrasonic welding or sealing and bonding by using sealant. The sensing electrode is located outside the housing during the process of enclosing the sensing circuit within the housing.

And S4, bonding the detection electrode in the shell groove and enabling the detection electrode to be attached to the shell groove. The working electrode, the reference electrode, the blank electrode and the counter electrode all have a substrate. In the bonding, the substrate is bonded in the recess of the housing, and the wire layer, the electrode layer and the enzyme layer are located outside the recess with respect to the substrate, as shown in fig. 10, for example.

In some embodiments, the method of making further comprises coating an outer film: preparing an outer membrane liquid, completely immersing the shell, the detection circuit sealed in the shell and the detection electrode arranged on the outer surface of the shell into the outer membrane liquid, lifting and airing for 5-10 min. The process of immersing in the membrane liquid and lifting and drying is repeated for 2-3 times. Drying the prepared sensor for 24 hours at normal temperature, and then storing at 2-8 ℃. For example, the outer membrane liquid is formed by mixing one or more solutions of polyurethane, silicone rubber polymer and polyethylene glycol; the outer membrane solution was mixed in a ratio of 6wt% PEG/THF solution and 4wt% PU/THF solution.

In some embodiments, the method of making further comprises coating a hydrophilic membrane: preparing hydrophilic membrane liquid, completely immersing the shell, the detection circuit sealed in the shell and the detection electrode arranged on the outer surface of the shell into the hydrophilic membrane liquid, lifting and airing for 5-10 min. The process of immersing in hydrophilic membrane liquid and lifting and drying is repeated for 2-3 times. For example, the specific process of applying the hydrophilic membrane solution is: the housing, together with the detection circuit sealed in the housing and the detection electrode mounted on the outer surface of the housing, was completely immersed in Tris buffer (pH = 8.5) for 24 hours at 3mg/ml dopamine, then immersed in Tris buffer (pH = 8.5) for 24 hours at 5mg/ml methacryloyloxyethyl phosphorylcholine polymer, and finally rinsed with pure water and stored at normal temperature. The hydrophilic membrane is one or more of zwitterionic polymer derivatives, such as methacryloyloxyethyl phosphorylcholine polymer, zwitterionic polymer containing sulfobetaine, and zwitterionic polymer containing carboxyl betaine.

Three-electrode system using CHI660E electrochemical workstation: and a working electrode, a reference electrode and a counter electrode of the self-made flexible detection electrode are respectively connected with the electrodes of the electrochemical workstation. And (3) completely immersing the implanted sensor into a glucose solution for in-vitro detection, wherein a chronoamperometry method is adopted, the detection potential is 0.5-0.7V, and the investigation range of the glucose concentration is 0-30 mmol/L. As can be seen in fig. 18, the sensor hydration speed was fast, the response to glucose was fast, and the current was smooth. As can be seen from FIG. 19, the linearity of the sensor for detecting the concentration of glucose exceeds 99.80%, and the linear detection range is 0-30 mmol/L.

The embodiments described in this specification are merely illustrative of implementation forms of the inventive concept, and the scope of the present invention should not be considered limited to the specific forms set forth in the embodiments, but also equivalent technical means that can be conceived by one skilled in the art based on the inventive concept.

Claims

1. An implantable sensor is characterized by comprising a shell, a detection circuit and a detection electrode, wherein the detection circuit is sealed in the shell, the detection electrode is arranged on the outer surface of the shell and is attached to the outer surface of the shell, and the detection electrode is electrically connected with the detection circuit; the sensor also comprises a connecting piece detachably connected with the shell, the connecting piece comprises a body and a conductive element, the body is provided with a slot and a through hole for inserting the detection electrode, the slot is communicated with the through hole, the conductive element is arranged in the through hole, two ends of the conductive element are exposed out of the through hole, one end of the conductive element is positioned in the slot, and the other end of the conductive element is positioned in the body; the body comprises a base and a pressing plate, a gap between the pressing plate and the base forms the slot, the through hole is formed in the base, one end of the pressing plate is a connecting end fixedly connected with the base, the other end of the pressing plate is a free end, and the free end of the pressing plate is detachably connected with the base.

2. The implantable sensor of claim 1, wherein the sensing electrode is helically wound around the outer surface of the housing; alternatively, the detection electrodes are arranged in parallel on the outer surface of the housing.

3. The implantable sensor of claim 1 wherein the housing outer surface has a recess for receiving the sensing electrode.

4. The implantable sensor of claim 3, wherein the depth of the recess is greater than or equal to the thickness of the sensing electrode.

5. The implantable sensor of claim 1, wherein the housing is integrally formed; alternatively, the housing may be formed from two or more pieces.

6. The implantable sensor of claim 2, wherein the sensing electrode comprises a working electrode and a reference electrode, the working electrode and the reference electrode each having a respective recess, the working electrode and the reference electrode each being positioned within the respective recess; alternatively, the working electrode and the reference electrode are located in the same recess.

7. The implantable sensor of claim 1, wherein the outer surface of the housing is coated with a biocompatible outer membrane, and the detection electrode is positioned between the outer surface of the housing and the biocompatible outer membrane.

8. The implantable sensor of claim 1, wherein two or more of the through-holes are located on the same side of the socket.

9. The implantable sensor of claim 1, wherein the body is an integrally formed piece of silicone.

10. The implantable sensor of claim 1, wherein the length of the body is between 5 and 10mm.