AU2019204869B2 - Improved apparatus and method for treatment of tissue - Google Patents

Abstract

IMPROVED APPARATUS AND METHOD FOR TREATMENT OF TISSUE 5 The present invention relates to an apparatus and method for facilitating treatment of tissue, particularly nerve tissue. An elongate conductor is placed in contact with the nerve tissue. It is stimulated by electromagnetic 10 radiation external to the implant (external to the patient). Radiation may be applied by a transcranial magnetic stimulator. Currents flow in the elongate conductor and produce an electrical field which stimulates a response in the 15 nerve tissue. This may be sufficient to create an action potential in the nerve tissue. Where the nerve tissue is damaged, the signal may stimulate regrowth. The elongate conductor may be a loop or a part-loop. It may be mounted to a bio adhesive substrate. 20 Figure 1(a) 11505951_1 sciatic nerve (b) loop antenna 2 (C) Nerve cross-section oop . antennas Voltage atnerveinterface3 E(E dl= V

Description

sciatic nerve

loop antenna (b) 2

(C) Nerve cross-section

oop . antennas

Voltage atnerveinterface3

E(E dl= V

IMPROVED APPARATUS AND METHOD FOR TREATMENT OF TISSUE

Field of the Invention

The present invention relates to an apparatus and method for facilitating treatment of tissue and, particularly, but not exclusively, to an apparatus and method for treatment of nerve tissue.

Background of the Invention

Nervous injury, from trauma, disease or otherwise, is a major medical problem. Mature neurons do not undergo cell division and therefore it is very difficult to achieve successful rehabilitation after nerve injuries. It is known, however, that where the injury causes gaps in axons, it is possible for the axons to regenerate over the gaps, such that a proximal and distal axon stump can reconnect. This occurs slowly, however, and with difficulty. Where the gap is too large, or the injury too extensive in another manner, regeneration to bridge the gap may not occur at all.

It is known to surgically suture nerve endings. Suturing success is limited, however, and depends much on the nature and extent of the injury and the skill of the surgeon. Where the gap between the proximal and distal ends of the nerve is too great, suturing will not be an option.

It is known to use grafting techniques to insert a segment of nerve to bridge a gap. Autograft and allograft techniques are used and both have their problems. Autografts are associated with limited availability of nervous tissue for grafting, and permanent de-nervation of

20220251_1 the donor site. Allografts require immunosuppressant drugs and have been reported to have a poor clinical success rate.

It is also known to use grafts of tissue to provide conduits across a gap between the distal and the proximal nerve stumps, to allow the nerve to regenerate along the conduit. The conduit, which may be of biocompatible materials, such as collagen, or non-biocompatible materials such as silicon, is grafted to the proximal and distal ends of the nerve stumps. Grafting can be via laser welding, soldering or use of chitosan or other bioadhesives.

The grafts can be non-resorbable or biodegradable. Non-resorbable grafts (such as silicon) include complications such as cytotoxicity and nerve constriction, particularly over the long term. Biodegradable grafts do not suffer from such problems as they are re-absorbed in the short term.

Grafts forming conduits can also provide support for substances which can facilitate nerve regrowth. These include nerve growth factors, Schwann cells, stem cells and other substances. These can be injected into the conduit or otherwise housed by the conduit e.g. adsorbed by the conduit walls.

International Patent Application No. PCT/AU2013/000028 discloses an apparatus and method for facilitating treatment of nerve tissue. An antenna arrangement implanted in the patient is arranged to receive RF signals and induces stimulating current in a bio-compatible conduit placed about a nerve lesion. This causes electrical stimulation of the nerve endings. Electrical stimulation is known to promote growth of the nerve endings. In an embodiment, the antenna is formed of two cylinders placed about the nerve tissue, together

20220251_1 forming electrodes of an antenna dipole. Other antennas disclosed include patch antennas and other arrangements. Another embodiment comprises an antenna implanted underneath the skin of the patient feeding energy to electrodes at the sight of the tissue treatment.

Some of these antenna arrangements and associated circuitry can be quite complex, and obtrusive when implanted into a patient.

Summary of the Invention

In accordance with a first aspect, the present invention provides an apparatus for facilitating treatment of tissue, comprising an elongate conductor arranged to be positioned in contact with the tissue to be treated, to form a tissue/conductor interface, the elongate conductor being arranged to receive a stimulation signal, and in response to the stimulation signal being arranged to generate a stimulating response at the tissue/conductor interface.

By "elongate conductor", it is intended that the conductor be longer than its width or thickness.

In an embodiment, the elongate conductor is a loop or part-loop, the circumferential length of the loop being longer than the loops width or thickness. In an embodiment, the loop is arranged to extend around or part way around the tissue being treated. In an embodiment, the tissue may be nerve tissue, and the loop or part-loop may extend around or part-way around the circumference of the nerve, in contact with the nerve tissue.

In an embodiment, the elongate conductor is mounted on a substrate. In an embodiment, the substrate may be bio-compatible material, such as chitosan. In an

20220251_1 embodiment, the substrate may comprise a bio-adhesive material. In an embodiment, the substrate may be arranged to be formed into a graft for mounting to the tissue with the conductor in contact with the tissue. Where the tissue is a nerve, the substrate may be arranged to be formed into a cylinder around a nerve. In an embodiment, the substrate may be arranged to be formed into a cylinder around a nerve lesion or other nerve injury, to facilitate treatment of the injured site.

In an embodiment, the elongate conductor is in the form of a strip plated on the substrate, so that when the substrate is in contact with the tissue, the strip is in contact with the tissue.

In an embodiment, the stimulating response generated is a potential difference (voltage) at the tissue/conductor interface. In an embodiment, the stimulation signal is received by the conductor and generates electrical currents running in the elongate direction of the conductor, which in turn generate electric fields at the tissue interface, generating the stimulating voltage. This is a novel stimulation paradigm. Where the tissue is nerve tissue, and the nerve is whole, the stimulating voltage advantageously is such as to generate an action potential within the nerve. Where the nerve is not whole, where there is a discontinuity, for example, the stimulation may activate a nerve regeneration mechanism, and regrowth.

Where the elongate conductor is a loop or a part loop, the currents are generated in the circumferential direction of the loop.

In an embodiment, the stimulation applied is magnetic stimulation, such as that applied by a Transcranial Magnetic Stimulator (TMS).

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In an embodiment, the apparatus further comprises a stimulator, in an embodiment being an electromagnetic stimulator comprising one or more loops.

In an embodiment, in operation, the elongate conductor is implanted in a patient in contact with the tissue, and the electromagnetic stimulator provides stimulation from outside of the body of the patient.

In an embodiment, the apparatus is implanted within a patient, contacting the tissue.

In an embodiment, an advantage of the apparatus is that it comprises a simple, elongate conductor. No complex circuitry or multiple electrode components of an antenna are required. It is enough to have an elongate conductor, such as a ring, in contact with the tissue to be treated. Stimulation can be applied from outside the body.

In accordance with a second aspect, the present invention provides an implant, implanted in a patient and comprising an apparatus in accordance with the first aspect of the invention.

In accordance with a third aspect, the present invention provides a method of treatment of tissue, comprising the steps of stimulating an implanted apparatus in accordance with the first aspect of the invention, with a stimulating signal.

In accordance with a fourth aspect, the present invention provides an apparatus for facilitating treatment of tissue, comprising a conductor arranged to be positioned in contact with tissue to be treated, to form a tissue/conductor interface, the conductor being arranged to receive a stimulation signal and in response to the stimulation signal being arranged to generate a potential difference at the tissue/conductor interface, the

20220251_1 potential difference generating a response within the tissue.

In an embodiment, where the tissue is nerve tissue, and the nerve is whole, the tissue response generated is an action potential in the nerve, where the nerve is broken, the tissue response generated may activate nerve regrowth.

In an embodiment, the stimulation signal is a magnetic stimulation signal.

In accordance with a fifth aspect, the present invention provides a method of treatment of tissue, comprising the steps of stimulating the tissue to create a potential difference at a tissue interface, the potential difference creating a response within the tissue.

In an embodiment, the tissue interface is an interface between the tissue and a conductor placed in contact with the tissue.

In accordance with a further aspect, the present invention provides an apparatus for facilitating treatment of tissue, comprising a conductive material arranged to be positioned in contact with the tissue to be treated, to form a tissue/conductor interface, the conductor being arranged to, when under influence from an electromagnetic field, wirelessly receive a stimulation signal, and in response to receiving the stimulation signal being arranged to generate a stimulating response at the tissue/conductor interface, the conductive material thereby acting as an electrode in which the stimulating response for stimulating the tissue is induced, when wirelessly receiving the stimulation signal

In an embodiment, the conductive material comprises a loop or part-loop.

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In an embodiment, the circumferential length of the loop is longer than the loops width or thickness.

In an embodiment, the loop is arranged to extend, in operation, around or part-way around tissue being treated.

In an embodiment, the tissue is nerve tissue, and the loop or part-loop is arranged to extend around or part-way around the circumference of the nerve, in contact with the nerve tissue.

In an embodiment, the conductive is mounted to a substrate.

In an embodiment, the substrate comprises a bio adhesive material.

In an embodiment, the substrate is arranged to be formed into a graft for mounting to the tissue, with the elongate conductor in contact with the tissue.

In an embodiment, the tissue is nerve tissue and the substrate is arranged to be formed into a cylinder which can be mounted around a nerve.

In an embodiment, the conductive material is in the form of a strip deposited onto the substrate.

In an embodiment, the apparatus is rranged to, in operation, in response to the stimulation signal, to generate a potential difference at the tissue/conductor interface.

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In an embodiment, the tissue is nerve tissue, and the potential difference is such as to generate an action potential within the nerve.

In an embodiment, the action potential is a compound action potential.

In an embodiment, the stimulation signal applied is a magnetic stimulation signal, such as that applied in Transcranial Magnetic Stimulator.

In an embodiment, the apparatus further comprises an electromagnetic stimulator comprising one or more coils.

In an embodiment, the apparatus is implanted within a patient, contacting tissue to be treated.

In another aspect, the present invention provides a method of treatment of tissue, comprising stimulating an apparatus in accordance the aspect mentioned above, positioned in contact with tissue to be treated, with a stimulation signal.

In an embodiment, the stimulation signal is in the form of Transcranial Magnetic Stimulator (TMS).

In another aspect, the present invention provides a method of treatment of tissue, comprising the steps of applying an electromagnetic field in range of a conductive material placed in contact with the tissue, to thereby induce a potential difference at an interface between the tissue and the conductive material, the potential difference creating a response within the tissue, the

20220251_1 conductive material thereby acting as an electrode in which the stimulating response for stimulating the tissue is induced, when wirelessly receiving the stimulation signal.

In an embodiment, an electromagnetic signal providing a stimulation signal to the conductive material is in the form of Transcranial Magnetic Stimulator (TMS).

Brief Description of the Figures

Features and advantages of the present invention will become apparent from the following description of embodiments thereof, by way of example only, with reference to the accompanying drawings, in which;

Figures 1(a), (b), and (c) are schematic diagrams of an apparatus in accordance with an embodiment of the invention shown diagrammatically in position about nerve tissue, and illustrating a mechanism of operation;

Figures 2(a), (b), and (c) illustrate diagrammatically further embodiments of apparatus in accordance with the present invention;

Figure 3 illustrates an apparatus in accordance with a further embodiment of the invention, being positioned around nerve tissue;

Figure 4 is a further view of the apparatus of Figure 3, in position around nerve tissue;

Figure 5 is a schematic diagram of an apparatus in accordance with an embodiment of the present invention;

Figure 6 is an experimental set-up of an apparatus for illustrating operation of an embodiment of the present invention;

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Figure 7 illustrates various voltage plots for the system of Figures 5 and 6;

Figure 8 shows a number of plots illustrating operation of an apparatus in accordance with an embodiment of the present invention placed around a sciatic nerve and stimulated;

Figure 9 is an in vivo image of an apparatus in accordance with an embodiment of the present invention in position on an intact sciatic nerve of a rat;

Figure 10(a) is a plot of CMAP amplitude triggered by operation of an apparatus in accordance with an embodiment in healthy sciatic nerves;

Figure 10(b) shows histologic slides from proximal and distal sites of nerves to which apparatus in accordance with an embodiment was laser bonded;

Figures 11(a) and (b) are diagrams illustrating positioning of an apparatus in accordance with an embodiment around nerve tissue for experimental purposes;

Figures 11(c) and (d) show in vivo images of the sciatic nerve after installation of the apparatus illustrated in the diagrams of Figures 11(a) and (b);

Figure 12 is a plot illustrating typical CMAPs of nerves 8 weeks post-operatively;

Figure 12(b) shows histologic slides from proximal and distal sites of the grafted nerves, and

Figure13 is a plot showing compound muscle action potentials (CMAPs) triggered in healthy sciatic nerves (controls) by a DC stimulator at different current levels.

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Detailed Description of Embodiments

Referring to Figure 1, an apparatus, generally designated by reference numeral 1, in accordance with an embodiment of the invention is illustrated. The apparatus 1 comprises an elongate conductor 2, in this example in the form of conductive loop 2, positioned around nerve tissue 3, in this example being a representation of a sciatic nerve. The loop 2 may be of any conductive material, and in this example is gold.

A magnetic stimulation signal 4 is shown applied by a TMS stimulator 5, with electromagnetic coils 6, 7 positioned orthogonally with respect to the conductive loop 2.

The stimulation signal 4 affects the loop 2 and loop 2 generates a stimulating response at the interface between the conductor and the nerve 3. The loop 2 is in contact with the nerve 3 tissue.

In more detail, when stimulated by the TMS apparatus 5, currents I flow in the loop antenna as illustrated in Figure 1(b).

The voltage generated in the loop antenna by the TMS sets up currents. These currents create propagating electromagnetic fields both at the surface of and outside the loop (see Figure 1(c)), to which the electric field is purely tangential. When the loop antenna surrounds the sciatic nerve, there is contact at the interface between the loop antenna and the nerve; the tangential electrical field is (in first approximation) identical at the interface due to Maxwell's boundary conditions. This tangential field around the nerve perimeter produces a voltage responsible for triggering the action potentials in the nerve 3 (where the nerve is whole, where the nerve is broken, the stimulation signal may stimulate regrowth

20220251_1 of the nerve).

Experimental data (see later) show that most of the currents stay in the ring 2 and does not leak into tissue. This is in contrast with current available stimulators that have 2 (or more) separate electrodes that inject current into tissue creating a closed circuit where current passes from the one electrode to the other through the tissue. The loop system pushes the charges present in the tissue, forming closed current loops, without injecting significant quantity of currents from the loop 2.

The apparatus is capable of stimulating nerves without the circuitry components and separate electrodes as it relies on a new stimulation paradigm; the TMS sets up currents inside the conductive loop (for example, gold), which in turn generates an electrical field at the tissue interface around the nerve, establishing an effective voltage capable of triggering action potentials see Figure 1(c).

The geometry of the antenna 2 does not require to be necessarily a ring but can be a monopole (straight strip of conducting material) or a spiral or other geometries such as closed loops (elliptical for example or other round shape) open loops, multiple straight lines or a combination of the previously described shapes. It is important that the conductor or the conductive antenna of any shape as indicated before, is in contact to tissue to trigger stimulation.

Figures 2(a), (b) and (c) show some different types of elongate conductors in accordance with embodiments. Figure 2(a) shows a loop conductor 10 which is flat and mounted on a substrate 11. Substrate 11 can be adhered to the tissue with the conductor 10 in contact with the tissue.

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Figure 2(b) shows a strip conductor 12 mounted on a substrate 13.

Figure 2(c) illustrates a helical coil conductor 14, which may be wound around tissues, such as nerve tissue.

As discussed above, the elongate conductor may take many other forms.

Figures 3 and 4 illustrate another embodiment of an apparatus of the present invention. In this embodiment, a conductive strip 20 (in this example the conductive material is gold) is deposited onto an adhesive substrate 21 to form a "graft-antenna" 22. In this example, the adhesive substrate is a chitosan-based film with photo adhesive capability. In Figure 3, the graft antenna 22 is illustrated being wrapped around the sciatic nerve 3. When wrapped around and adhered to the sciatic nerve by way of laser activation (Figure 4), the graft-antenna 22 forms a cylinder around the sciatic nerve 3, with the loop conductor 20 in conductive contact with the sciatic nerve. The graft antenna 22 forms a cylinder within which the nerve tissue can be treated. For example, the graft antenna 22 could be formed around a nerve lesion, or any nerve area where damage has occurred. The antenna 20 can then be pulsed with TMS in order to treat the nerve.

The chitosan (or other material) substrate is anchored to tissue by laser stimulation, without sutures exploiting the photo-adhesive properties of the chitosan adhesive.

Characterization of the TMS-antenna system

Figure 6 illustrates an experimental set up for characterising operation of a loop antenna in accordance with an embodiment of the present invention. In this

20220251_1 experiment, a loop antenna in the form of a copper ring was utilised.

Figure 6 shows an experimental set-up of the voltage measurements in a copper loop antenna using the oscilloscope and TMS. Figure 5 illustrates TMS 5 and loop antenna 50 positions in Cartesian coordinates; their relative position varied along the three axes during the antenna characterization experiments. The optimal TMS position for nerve stimulation in rats was found to be above the animal at (0,0,6 cm) when the antenna was placed around the nerve in the XY plane (at the axes origin).

The loop antenna successfully coupled to the transcranial magnetic stimulator (Figure 6) that induced voltages of the order of 102 - 10-3volts in the antenna. In particular, the voltage induced in the loop antenna 50 decreased as the TMS coil 5 was moved away along the Z-axis (Figures 7a, 7b); when stimulation occurred at ~0.72 T (60% Bmax), the voltage varied from 18 to 2 mV as the distance increased from 10 to 150 mm respectively. The voltage induced in the antenna was symmetric around the origin, indicating that the B-field received by the antenna was symmetric with respect to the axes origin, as described by the TMS manufacturer. In this instance, the voltage values decreased as the antenna moved away from the centre of the TMS coil along the X-axis and Y-axis (Figures 7c, 7d).

Figure 7(a) is a plot of the voltage vs time that is induced in the copper loop antenna by the TMS. The duration of the voltage pulse is ~ 350 ps. 7(b) shows the voltage induced in the loop antenna vs distance when the TMS is positioned on the z-axis and the antenna is fixed at the axes origin; Figure 7(c) shows the voltage vs distance when the antenna moves along the x-axis (x,0,0) and the TMS height is fixed at (0,0,6 cm). Figure 7(a) shows the voltage vs distance when the antenna moves along the y-axis (0,y,0) and the TMS height is fixed at (0,0,6

20220251_1 cm). The symmetry of the voltage with respect to the x and y-axes is due to the symmetric magnetic field generated by the TMS coil. Three independent experiments were performed for each plot and each point value is the average of ten measures. The standard deviation ( 0.06 mV) is not shown in the plots for image clarity.

Loop-antenna stimulation of nerves

After the characterization of the TMS-antenna system, we tested if this system could stimulate tissue. The TMS triggered compound action potentials either in muscles (0.67 ± 0.09 mV, n = 3, Table 1) or nerves (0.33 0.05 mV, n = 3) when the loop antenna was placed around the sciatic nerve of rats; no action potential was elicited during TMS stimulation without the loop antenna (Figure 8). It is of note that eliciting an action potential without the antenna was impossible, even when the TMS coil was positioned just above the nerve (z = 3 cm, y = 0, x = 0) at maximum magnetic field amplitude (Bmax ~1.2 T). The action potentials were triggered only in the presence of the loop antenna when the B-field was 0.6 T (50% Bmax), while no muscle or nerve response was recorded at lower magnetic magnitudes. If the B-field was 0.84 T (70% Bmax), the movement of the rodent's body, triggered at each pulse, affected the electrode stability and reliability of measurements; it was also observed that when the magnetic field was 0.94 T (80% Bmax), the action potential was obscured by an artefact due to the intensity of the TMS pulse. A distinctive twitch of the leg was nonetheless observed in all these cases (Table 2). The compound action potentials in muscles and nerves did not change significantly when the antenna around the nerve was earthed to the oscilloscope. No action potential was elicited at any B-field magnitude, including Bmax, when the antenna wrapped by a plastic coating (n = 3); the latter

20220251_1 experimental outcome suggests that contact between the copper loop and nerve was necessary for stimulating nerves. It was also noted that during TMS irradiation, action potentials were occasionally not triggered; this "misfiring" was due to a small displacement (~10 pm) of the loop antenna around the nerve, caused by the leg twitch. The least misfire occurred at 0.72-0.84 T (60-70% Bmax) where no action potential was elicited at 8% of the time, while at 80% Bmax, artefacts obscured any possibility of an action potential recording. These results indicate that the TMS coil should be positioned ~6 cm from the rat nerve, and function at 60% Bmax in order to ensure stable and reliable measurements of action potentials (Figure 5). At these settings, the current induced by the TMS in the loop antenna positioned around the nerve had a peak value of 3.2 ± 0.3 pA; a value of 3.6 i 0.1 pA was measured in the antenna without the nerve (p = 0.0714, unpaired t test, n = 3).

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Table 1. CMAP and Copper Loop Antenna Voltage

Amplitude (mV) Loop Voltage (mV)

CMAP + Oscilloscope 0.67 0.09 10.49 0.07

CMAP 0.70 0.07

CNAP + Oscilloscope 0.33 0.06 10.49 0.06

CNAP 0.33 0.05

Table 1 shows CMAP + Oscilloscope, Compound Muscle Action Potential amplitude measured when the loop antenna around the nerve is powered by the TMS. The loop antenna is connected to the oscilloscope. CMAP, CMAP amplitude measured when the loop antenna around the nerve is powered by the TMS without oscilloscope connection. CNAP + oscilloscope, amplitude of Compound Nerve Action Potential with antenna connected to oscilloscope. CNAP, amplitude of Compound Nerve Action Potential without oscilloscope connection. Loop Voltage, voltage induced in the copper loop antenna by the TMS. Three independent experiments were performed in each group (n = 3); 120 measures were averaged for the amplitude and voltage values in each experiment.

Figure 8(a) shows a typical CMAP that is triggered by the copper loop antenna placed around the sciatic nerve (n = 3). (b) shows a typical CMAP triggered by the gold loop embedded in the graft-antenna when it is laser-bonded around the sciatic nerve (n = 3). The TMS was located 6 cm above the loop antenna and nerve (x = 0, y = 0, z = 6 cm), and irradiated by an electromagnetic field with intensity B ~0.72 T (60% Bmax). The voltage pulse induced in the loop antenna by the TMS is shown in the figure insets. Figure 8(c) shows the voltage amplitude of the copper loop is proportional to the magnetic field magnitude, showing the inductive nature of this antenna.

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Table 2. Compound Muscle Action Potential vs Magnetic Field Amplitude

% BMax CMAP Loop Voltage Misfire Muscle twitch (Magnitude) (mV) (mV) (%)

10% - 1.63 0.04 - No 20% - 2.52 0.03 - No 30% - 4.32 0.02 - No 40% - 5.87 0.03 - No 50% 0.23 0.06 8.01 0.05 12% Yes 60% 0.72 0.07 10.43 0.07 8% Yes 70% 0.86 0.04 11.03 0.05 8% Yes 80% - 11.31 0.09 - Yes 90% - 14.64 ± 0.03 - Yes 100% (1.2 T) - 16.94 ± 0.05 - Yes

Table 2 shows: % BMax, amplitude % of maximum TMS magnetic field; CMAP, compound muscle action potential triggered by the copper loop antenna that was irradiated by the TMS; Loop Voltage, voltage induced in the copper loop antenna by the TMS; Misfire, failure percentage in triggering CMAPs following TMS irradiation. It was noted that when contact was (partially) lost between the loop antenna and the nerve, no action potential was elicited. Muscle Twitch, visual recognition of muscle twitches during TMS stimulation. Three independent experiments were performed and for each experiment the CMAP or voltage values were an average of 30 measures.

Compound Muscle Action Potential: AC versus DC currents

This test gauged the amount of DC current required to trigger a CMAP similar to that elicited by TMS-antenna stimulation. It was found that when a DC current of ~18p4A was injected in the nerve by a standard stimulator, a CMAP with an amplitude of 0.88 ± 0.10 mV of was triggered, while the TMS elicited a CMAP of 0.85 ± 0.10 mV in the same nerve, generating an AC peak current of 3.7 ± 0.1 pA inside the loop antenna. The CMAP amplitudes originated by the two methods were not statistically different (p = 0.5142, paired t-test, n = 4). Notably, the CMAP decreased sharply to 0.53 ± 0.04 mV when a DC current of ~15 pA was injected in the nerve, showing a clear trend between

20220251_1 current and amplitude Figure 13. In the previous experiments, copper loops were implanted in live rats for ~15 minutes and were used as a proof of concept considering the moderate cytocompatibility of copper 30. Note that loop antennas made of biocompatible materials such as titanium or gold are indicated for long term implantation and stimulation of nerves without any toxic side effects.

Figure 13 shows compound muscle action potentials (CMAPs) triggered in healthy sciatic nerves (controls) by a DC stimulator at different current levels. The signal amplitude decreases sharply from ~0.9 to ~0.5mV when the current drops from 18 pA to 15 pA, respectively (n=3).

In vivo implantation of graft-antennas: stimulation of uncut nerves As discussed above, applicants have developed a graft-antenna that comprises at least two parts, namely a chitosan-based film 21 with photo-adhesive capability and a thin loop of gold plated on the adhesive (Figures 3 and 4). The graft-antenna 22 was photochemically bonded by a laser to the sciatic nerve 3 and the TMS elicited CMAPs for a 12-week period (Figure 10a); the device did not migrate during this time. The graft-antenna triggered steady action potentials during the implantation time and remarkably, the CMAPs (~1.3 mV) recorded before euthanizing animals were not statistically different from the values measured immediately after implantation (p > 0.05, one-way ANOVA, Tukey's multiple comparison test, n =

5). This result demonstrates that the graft-antenna is stable once implanted and is a reliable stimulator that does not cause detrimental effects on nerve conduction at the selected stimulation regime. The action potentials recorded when the leg wound was closed (weeks 2 -11) varied between 0.8 and 1.1 mV and were lower than the ones

20220251_1 recorded on the exposed nerves (immediately after implantation and before euthanasia - week 1 and week 12); this can be ascribed to the skin and muscles covering the nerves and attenuating the electromagnetic field over the gold loop of the graft-antenna (p < 0.05, one-way ANOVA). Histology results showed that there was no statistical difference in axon number, fiber diameter, axon diameter, and myelin thickness between the contralateral (control), proximal and distal sites of the nerve stimulated with the graft-antenna (Figure 10b, Table 3). This outcome agrees with the electrophysiology data and confirms the graft antenna is as a safe stimulator. Of note is the fact that the graft-antenna elicits significantly higher CMAPs than copper loops when stimulated with the same magnetic magnitude (1.43 ± 0.11 mV and 0.69 0.09 mV respectively; p = 6.72123E-05, unpaired t-test, n = 5). The currents measured in graft-antennas were also significantly higher than those in copper loops (13.5 ± 0.2 pA vs 3.2 ± 0.3 pA; p = 8.98729E-08, unpaired t-test, n = 3). This may be due to the gold strip altering the geometry and enlarging the diameter of the loop when the adhesive is wrapped around the nerve and a section of it is superimposed (~25%). Remarkably, no misfire occurred during the nerve stimulation with the graft-antenna, indicating that this device was more stable around the nerve than the copper loop.

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Table 3. Histomorphometric Results (Uncut Nerves)

Histomorphometric results of the nerves 12 weeks after graft-antenna implantation. The TMS stimulated the nerves via the graft-antenna once a week for 1 hour (1 pulse/sec) at 60% Bmax (~0.72 T). The analysis was performed on -55% of the total cross-sectional area of nerves (n = 5).

Proximal Distal Control

Myelinated Axon 1858 75 1846 81 1849 71 Count Nerve Fiber 5.9 1.6 5.8 1.7 5.6 1.5 Diameter (pm) Axon Diameter 3.6 1.5 3.6 1.6 3.5 1.5 (pm)

Myelin Thickness 2.1 0.8 2.1 0.7 2.1 0.6 (pm)

Nerve Area (mm2 ) 54.3 6.6 55.2 9.2 54.7 6.7

Figure 9 is an in vivo image of the graft-antenna after being laser-bonded to the intact sciatic nerve (diameter -1 mm) of a rat. The graft-antenna is made of a chitosan-based film containing the dye rose bengal and a strip of gold (thickness -70 nm) embedded in the adhesive (inset). When the film is placed around the nerve, the gold strip becomes a loop antenna. The green laser (X=

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532 nm) irradiates and activates the rose bengal inside the adhesive film that bonds to tissue. Note that the blood vessels do not appear coagulated or otherwise damaged under or in the proximity of the graft-antenna. The gold loop antenna contacts and surrounds the nerve underneath the graft that conforms to the nerve without constriction.

Figure 10(a) is a plot of the CMAP amplitude that is triggered in healthy (uncut) sciatic nerves by the graft antenna during TMS stimulation, over a 12-week period. The graft-antenna was firstly bonded to the nerve by a green laser, followed by TMS irradiation of the graft-antenna once a week for 1 hour during a 12-week period. The CMAPs at week 0 and week 12 were not statistically different indicating that the graft-antenna is a reliable and stable stimulator (p > 0.05, one-way ANOVA, Tukey's multiple comparison test). The CMAP between weeks 1 and 11 was fairly constant, although lower than the CMAP at week 0 and 12 (p < 0.05, one-way ANOVA, Tukey's multiple comparison test). This was due to the electromagnetic shielding of tissue over the nerve: the CMAP was recorded with the nerve exposed to the TMS only at week 0 and 12. The standard deviation ( 0.2 mV) is not shown in the plot for visual clarity. Each point represents the average of 10 pulses. Figure 10(b) shows histologic slides from proximal and distal sites of the nerves to which the graft-antenna was laser bonded. These nerves were briefly stimulated for 1 hour by the TMS via the graft-antenna over a 12-week period (n = 5). The TMS stimulation and laser bonding procedure did not alter or affect axon number, diameter and myelin thickness when compared to untreated contralateral nerves (p > 0.05, one-way ANOVA). (Scale bar = 10 pm).

In vivo nerve grafting of transected nerves

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The aim of this experiment was to test the graft-antenna in vivo and assess its ability of stimulating axon regrowth without adverse effects after nerve transection and grafting. All grafted nerves were patent and in continuity at 8 weeks post-operatively; no sign of uncharacteristic inflammation or tissue growth was macroscopically evident at the operation site (Figure 11). The nerves that were repaired and TMS-stimulated with the graft-antenna produced a muscle twitch at weeks 6, 7 and 8, signalling regeneration of axons through the graft. Before euthanasia at week 8, the CMAP of animals implanted with the graft-antenna was measured with a value of ~48% of the un-operated contralateral nerves (0.33 ± 0.09 vs 0.68 ± 0.09 mV, n = 5, Figure 7); while animals grafted with the adhesive alone elicited CMAPs that were 0.26 ± 0.09 mV or ~38% of the contralateral nerves (Table 2). A similar trend was observed for the compound nerve action potentials (CNAPs) of the graft-antenna and adhesive-only groups that were 71% and 41%, respectively, of the contralateral nerves (0.32 ± 0.01 mV). The nerve conduction velocity (NCV) of nerves repaired with the graft-antenna and adhesive were 71% and 61%, respectively, of the contralateral nerves (58.7 ± 3.1 m/s). When compared to the adhesive-only repairs, the graft-antenna group had higher CMAPs (p < 0.001), CNAPs (p < 0.001) and NCVs (p < 0.01) (one-way ANOVA, Tukey post-test). The histology analysis (Figure 12) showed that all distal nerve sections were populated with axons; axon count of distal sites (1396 ± 68) operated with the graft-antenna was significantly higher than distal sites operated with the adhesive only (1202 ± 66) (p = 0.0363, one-way ANOVA, Tukey post-test). However, myelin thickness, fiber and axon diameter were not significantly different in the two groups (Table 4). Contralateral nerves had the highest number of myelinated axons as expected (1861 ± 79, p < 0.0001, one-way ANOVA).

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Table 4. Histomorphometric Results (Grafted Nerves)

Experimental Graft Antenna Chitosan Adhesive Group Proximal Distal Proximal Distal Control

Myelinated 1872+100 1396 +68* 1862+75 1202+66 1861+79 Axon Count Nerve Fiber 5.8+ 1.8 5.4+1.4 6.0+1.7 5.1+0.8 5.9+ 1.8 Diameter (pm)

Axon Diameter 3.5+ 1.6 3.2+0.8 3.6+ 1.5 3.1+0.8 3.6+ 1.7 (pm)

Myelin 2.2+0.9 2.1+0.8 2.3+0.8 2.0+0.7 2.2+0.7 Thickness (pm)

Nerve Area 54.3+8.9 54.2+9.2 54.5+6.0 55.6+10.0 55.1+7.9 (mm2)

Histomorphometric results of the nerves 8 weeks post-operatively; all nerves were briefly stimulated once a week for 1 hour (1 pulse/sec) and for 8 weeks by the TMS (-0.72 T). Nerves repaired with the graft antenna (n = 5) had more myelinated axons regrowing into the distal site than nerves operated with the adhesive only (one-way ANOVA, Tukey post-test, p = 0.0363). However, myelin thickness, fiber and axon diameter were not significantly different in the two groups.

Figures 11(c) and (d) show in vivo image of the sciatic nerve after laser-grafting. The nerve graft is reconnected to the distal stump by the adhesive and to the proximal stump by the graft-antenna; the green laser photo-crosslinked the adhesive to tissue (Figures 11(a) and (b)). The gaps between the nerve graft and the stumps are noticeable in the magnified image (Figure 11(d)). Nerves and surrounding tissue do not appear damaged by the laser procedure.

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Table 5. Electrophysiological Parameters of Grafted Nerves

CMAP (mV) CMAP (mV) CNAP (mV) NCV (m/s) TMS DC DC Stimulation Stimulation Stimulation Graft - 0.98 0.09 0.33 0.09 0.21 0.08 41.74 4.13 Antenna Chitosan - 0.26 0.09 0.14 0.07 36.65 6.33 Adhesive Control 1.43 0.11 0.69 0.09 0.32 0.08 59.28 6.51

The electrophysiological parameters for sciatic nerves 8 weeks post-operatively. Nerves repaired with the graft antenna (n = 5) had higher values of compound muscle action potential (CMAP), compound nerve action potential (CNAP) and nerve conduction velocity (NCV) than nerves repaired with the chitosan adhesive only (one-way ANOVA, Tukey post-test, p < 0.01). Legend: DC Stimulation, nerves stimulated with a DC stimulator; TMS Stimulation, nerve stimulated with the TMS.

Figure 12(a) shows typical CMAPs of nerves 8 weeks post-operatively; these nerves were repaired either with the graft-antenna or adhesive only and underwent TMS stimulation once a week for 1 hour. The amplitude of the CMAP was larger in nerves repaired with the graft-antenna (p < 0.01, one-way ANOVA, Tukey's multiple comparison test, n = 5). All action potentials were elicited by a DC stimulator, except for the one represented by a dot line that was triggered by the TMS. Figure 12(b) shows histologic slides from proximal and distal sites of the grafted nerves that were repaired with the graft-antenna (first row) and adhesive only (second row). The unoperated contralateral nerves served as control in both groups. Subsequent to the operation, the nerves were briefly stimulated for 1 hour by the TMS over a period of 8 weeks (n = 5). After 8 weeks, a larger number of myelinated axons regrew through the distal site of the nerve graft repaired with the graft-antenna than the site repaired with the adhesive only (1396 ± 68 vs 1202 ± 66, p =

0.0363, one-way ANOVA, Tukey's multiple comparison test).

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Axon diameter and myelin thickness were not statistically different among the two operated groups (p > 0.05, one-way ANOVA). The histomorphometric parameters were significantly higher in the control group (myelinated axons = 1861 ± 79, p < 0.0001, one-way ANOVA). (Scale bar = 10 Pm).

The above described examples illustrate that applicants have succeeded in fabricating and testing in vivo a biocompatible graft-antenna that repairs peripheral nerves without sutures and stimulates them wirelessly without inserting electrodes in the body. The graft antenna was implanted around the uncut sciatic nerves of rats for 12 weeks and showed remarkable consistency in triggering CMAPs for the entire duration of the experiment. The histology results also indicated that the stimulation regime adopted in this study (1 hour per week, pulse duration ~350 ps, repetition rate = 1 s, Bmax ~0.72 T) did not alter the number and morphometric parameters of axons when compared to untreated contralateral nerves. The brief TMS stimulation of transected nerves that were repaired with the graft-antenna facilitated axon regeneration and histological analysis revealed that the axon count of the distal site was 76% that of unoperated contralateral nerves. Nerves grafted with the adhesive only were also stimulated by the TMS once a week but their axon count and electrophysiology performance were inferior.

The principles underlying the TMS-antenna stimulation of tissue can be inferred. The voltage generated in the loop antenna by the TMS sets up currents, namely -3.6 pA in the copper loop and -13 pA in the gold loop of the graft-antenna. These currents create propagating electromagnetic fields both at the surface of and outside the loop, to which the electric field is purely tangential 31. When the loop antenna surrounds the

20220251_1 sciatic nerve, there is contact at the interface between the loop antenna and the nerve; the tangential electrical field is (in first approximation) identical at the interface due to Maxwell's boundary conditions. This tangential field around the nerve perimeter produces the voltage responsible for triggering the action potentials (Figure 1). In fact, our experiments demonstrated that no action potential is elicited if the loop antenna is shielded with a plastic insulator during TMS irradiation. Therefore, the contact between the loop antenna and nerve tissue is necessary to elicit action potentials. It can be ruled out that action potentials are provoked by electromagnetic fields traveling inside the nerve that have been generated by the loop currents. These secondary fields can indeed travel into nerves through the plastic shield but they have no stimulatory effect. Note that naked copper loop antennas (no plastic shield) also failed in triggering action potentials whenever the contact with the nerve was lost, even if the loop remained very close to nervous tissue (~10 pm) as recorded during the loop antenna misfires. This confirms the hypothesis that the secondary electromagnetic fields inside the nerve do not trigger action potentials. It appears unlikely that action potentials are elicited by currents flowing into the nerve from the loop antenna. Our results show that CMAPs with an amplitude of ~0.85 mV are triggered when currents in the copper loop antenna are 3.2 ± 0.3 pA; if the nerve is removed from the loop, the antenna current increases to 3.6 ± 0.1 pA. If we assume that a 0.4 pA current flows into the nerve from the antenna, no action potential can be elicited because a DC current of 18 pA is necessary to initiate a 0.85 mV action potential. Furthermore, the amplitude of action potentials drops from ~0.85 to ~0.53 mV when the DC injector delivers a 15 pA current into the nerve, which is still much larger than 0.4 pA (Figure 13). Although details of axon depolarization are still unclear, our results indicate that the voltage around the loop

20220251_1 nerve interface elicits action potentials without the intervention of secondary electromagnetic fields or leaked currents from the metallic loop into the nerve. A similar result is obtained using the graft-antenna as the currents measured when the nerve is or isn't inserted in the graft are -13.5 and -15.2 pA, respectively. The CMAPs elicited by the graft-antenna were larger than the ones triggered by the copper loop antenna in the uncut sciatic nerves (~1.4 vs ~0.7 mV); this can be ascribed to the higher voltage produced at the nerve interface by the graft antenna. This hypothesis is in agreement with the observation that currents in the graft-antenna were higher than the ones induced in the copper loop. Variable currents indeed contribute in generating tangential electric fields at the nerve interface; Li et al reported that the tangential near fields of a small loop antenna are proportional to the loop current.

Embodiments of the present invention have a number of advantages. Prior art stimulators are implanted with conventional means; electrodes, for example, are routinely sutured to tissue. Sutures are notoriously invasive and the incidence of complications is high (30-40%). The commonest hardware-related complications are electrode migration, electrode failure and fracture, while other frequent side-effects include infection and pain over the implant 37. The graft-antenna of an embodiment of this invention is a biocompatible device that is fixed to tissue without sutures and with non-invasive means, namely by a low power laser that keeps the tissue temperature below 37 0C during irradiation 38,39. Our study has shown that the graft-antenna is stable over the nerve and does not shift position or diminish in its stimulation capacity over a 3-months period (Figure 10). The graft-antenna is also powered by a TMS at levels of radiation that are safe to patients 40. Furthermore, the components of the device; namely chitosan and a small strip of gold, are non-toxic

20220251_1 and biologically compatible, with the chitosan film also biodegradable 41. An innovative antenna-TMS system has been developed and characterized for nerve stimulation. The antenna can be a biocompatible metal loop such as gold or titanium positioned around the nerve, or a graft antenna based on chitosan and comprising a gold loop. The graft-antenna is at the same time a wireless stimulator powered by a TMS, and an adhesive scaffold that is fixed to tissue by light and without sutures. The graft-antenna is stable in the body after implantation and can facilitate axon regeneration with no significant adverse effects.

A simple conductive loop can be used to stimulate the tissue. For example, a gold loop can be mounted around a nerve. In an embodiment, the loop does not need to be a complete loop. It could be a part-loop e.g. half a loop or even less. In an embodiment, it may be mounted on an adhesive scaffold of any material, but this is not essential. Other biomaterials that could be used for the scaffold include collagen, or any other biomaterial.

Embodiments of the invention may be used to treat any nerve tissue by stimulation. For example, it may be used to treat the spinal cord by electrical stimulation, where the cord is damaged, for example. Embodiments may be used to treat any other tissue types.

An embodiment of a draft-antenna was prepared as follows. First adhesive film was prepared;

Medium molecular weight chitosan (598 cps viscosity, 81% deacetylation; Sigma-Aldrich, Sydney, NSW, Australia) was dissolved at a concentration of 1.7% (w/v) in deionized water that contained 2% (v/v) acetic acid and 0.01% (w/v) rose bengal. The viscous solution was stirred for 14 days at room temperature (~25 0C) in the dark to avoid photo-bleaching of rose bengal. Insoluble matter was

20220251_1 removed by centrifuging the rose bengal-chitosan solution at 3270xg for an hour. The collected supernatant was spread uniformly (~1.2 ml over ~12 cm2) on a dry and sterile Perspex plate at room temperature. The solution was allowed to dry over 3 weeks which caused ~90% water content loss, forming a thin film which did not dissolve in water 29. The rose bengal-chitosan film was carefully detached from the plate avoiding damage and small rectangular sections (~5x5 mm) were cut with scissors. An Emitech K550X gold coater (Quorum Emitech, East Sussex, England) sputtered a strip of gold onto the adhesive using a filter paper template. The chitosan adhesive was placed underneath the template and a gold strip was deposited with a width of 0.8 ± 0.1 mm and thickness of 50-80 nm. When this adhesive is placed around the nerve, the gold strip becomes a loop antenna that can receive electromagnetic radiation. The adhesive graft-antennas were stored in a sterile plastic box and kept in the dark at room temperature to avoid dye photobleaching.

In the above embodiments, the conductor must generally be in contact with the tissue. Where this is nerve tissue, this would generally mean the outer part of the nerve (perineurium or epineurium). Where connective tissue grows in between the conductor and the tissue, however, stimulation still occurs, so this would be considered as the conductor still contacting the tissue.

In the above embodiments, a transcranial magnetic stimulator is used to stimulate the conductor with the radio waves. Any other source of other radio waves may be used for stimulation, and the invention is not limited to a TMS. In embodiments, wave length of stimulation may depend on the dimensions of the conductor. For example, it is possible that nanostructured antennas could stimulate tissue using visible light (terahertz). In embodiments, the wave length of the radiation used may be

20220251_1 of similar size to antenna/conductor. In above embodiments, nerve stimulation via TMS lasted sixty minutes generally and consisted of single pulses (duration in the order of 350 micro seconds, frequency in the order of 2860Hz, repetition rate one pulse per second, at a field magnitude of 0.72 Tesla (60% of Bmax).

The conductor may generally be of any dimensions. In embodiments, it may be a centimetre or a few centimetres to a few millimetres and even down to micrometres or nanometres in the length (elongate) direction.

In the above embodiments, the TMS cores are positioned in the order of six centimetres from the stimulator. These distances can be varied from 1 to 12 centimetres, 2 to 11 centimetres, 3 to 9 centimetres 4 to 7 centimetres. Distances can in fact be varied in embodiments from a centimetre to a few decimetres.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

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References 1. Sunderland, S. Nerves And Nerve Injuries. (Churchill Livingstone, Edinburgh, 1978). 2. Kline, D. G. & Hudson, A. R. Nerve Injuries: Operative Results For MajorNerve Injuries, EntrapmentsAnd Tumors. (W.B. Saunders, Philadelphia, 1995). 3. Webber, C. A. et al. Schwann cells direct peripheral nerve regeneration through the Netrin-1 receptors, DCC and Unc5H2. Glia 59, 1503-1517 (2011). 4. Fu, S. Y. & Gordon, T. The cellular and molecular basis of peripheral nerve regeneration. Mol. Neurobiol. 14, 67-116 (1997). 5. Battiston, B., Geuna, S., Ferrero, M. & Tos, P. Nerve repair by means of tubulization: literature review and personal clinical experience comparing biological and synthetic conduits for sensory nerve repair. Microsurgery25, 258-267 (2005). 6. Barton, M. J. et al. Long term recovery of median nerve repair using laser-activated chitosan adhesive films: sutureless median nerve repair. J. Biophotonics 8, 196-207 (2015). 7. Atkins, S. et al. Scarring impedes regeneration at sites of peripheral nerve repair. Neuroreport 17, 1245-1249 (2006). 8. Sharma, N., Marzo, S. J., Jones, K. J. & Foecking, E. M. Electrical stimulation and testosterone differentially enhance expression of regeneration-associated genes. Exp. Neurol. 223,183-191(2010). 9. Foecking, E. M. et al. Single session of brief electrical stimulation immediately following crush injury enhances functional recovery of rat facial nerve. J. Rehabil. Res. Dev. 49, 451-458 (2012). 10. Willand, M. P., Nguyen, M.-A., Borschel, G. H. & Gordon, T. Electrical stimulation to promote peripheral nerve regeneration. Neurorehabil. NeuralRepair 30, 490-496 (2016). 11. Al-Majed, A. A., Neumann, C. M., Brushart, T. M. & Gordon, T. Brief electrical stimulation promotes the speed and accuracy of motor axonal regeneration. J. Neurosci. 20, 2602-2608(2000). 12. Udina, E. et al. Electrical stimulation of intact peripheral sensory axons in rats promotes outgrowth of their central projections. Exp. Neurol. 210, 238-247 (2008). 13. Aglah, C., Gordon, T. & Posse de Chaves, E.I. cAMP promotes neurite outgrowth and extension through protein kinase A but independently of Erk activation in cultured rat motoneurons. Neuropharmacology55, 8-17 (2008). 14. Gordon, T., Udina, E., Verge, V. M. K. & Posse De Chaves, E. I. Brief electrical stimulation accelerates axon regeneration in the peripheral nervous system and promotes sensory axon regeneration in the central nervous system. Motor Control 13, 412-441 (2009). 15. Huang, J., Ye, Z., Hu, X., Lu, L. & Luo, Z. Electrical stimulation induces calcium dependent release of NGF from cultured Schwann cells. Glia 58, 622-631 (2010). 16. Koppes, A. N. et al. Neurite outgrowth on electrospun PLLA fibers is enhanced by exogenous electrical stimulation. J. Neural Eng. 11, (2014). 17. Wan, L., Zhang, S., Xia, R. & Ding, W. Short-term low-frequency electrical stimulation enhanced remyelination of injured peripheral nerves by inducing the promyelination effect of brain-derived neurotrophic factor on Schwann cell polarization. J. Neurosci. Res. 88, 2578 2587 (2010).

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18. Weiner, R. L., Yeung, A., Montes Garcia, C., Tyler Perryman, L. & Speck, B. Treatment of FBSS low back pain with a novel percutaneous DRG wireless stimulator: pilot and feasibility study. PainMed. 17, 1911-1916 (2016). 19. Weiner, R. L., Garcia, C. M. & Vanquathem, N. A novel miniature, wireless neurostimulator in the management of chronic craniofacial pain: preliminary results from a prospective pilot study. Scand. J. Pain 17, 350-354 (2017). 20. Harkema, S. et al. Effect of epidural stimulation of the lumbosacral spinal cord on voluntary movement, standing, and assisted stepping after motor complete paraplegia: a case study. Lancet377, 1938-1947(2011). 21. Hentall, I. D. A long-lasting wireless stimulator for small mammals. Front. Neuroeng. 6, 8 (2013). 22. MacEwan, M. R., Gamble, P., Stephen, M. & Ray, W. Z. Therapeutic electrical stimulation of injured peripheral nerve tissue using implantable thin-film wireless nerve stimulators. J. Neurosurg. 1-10 (2018). 23. Shon, A., Chu, J.-U., Jung, J., Kim, H. & Youn,I. An implantable wireless neural interface system for simultaneous recording and stimulation of peripheral nerve with a single cuff electrode. Sensors (Basel). 18, (2017). 24. Sanghoon, L. et al. Toward bioelectronic medicine-neuromodulation of small peripheral nerves using flexible neural clip. Adv. Sci. 4, 1700149 (2017). 25. Frost, S. J. et al. Gecko-inspired chitosan adhesive for tissue repair. NPG Asia Mater. 8, e280 (2016). 26. Mawad, D. et al. A conducting polymer with enhanced electronic stability applied in cardiac models. Sci. Adv. 2, (2016). 27. Lauto, A. et al. Fabrication and application of rose bengal-chitosan films in laser tissue repair. J. Vis. Exp. 1-5 (2012). doi:10.3791/4158 28. Barton, M. et al. Laser-activated adhesive films for sutureless median nerve anastomosis. J. Biophotonics 6, 938-949 (2013). 29. Barton, M. J. et al. Tissue repair strength using chitosan adhesives with different physical chemical characteristics. J. Biophotonics 7, 948-955 (2014). 30. Bergemann, C. et al. Copper as an alternative antimicrobial coating for implants - an in vitro study. WorldJ. Transplant. 7, 193-202 (2017). 31. Li, L.-W., Leong, M.-S., Kooi, P.-S. & Yeo, T.-S. Exact solutions of electromagnetic fields in both near and far zones radiated by thin circular-loop antennas: a general representation. IEEE Trans. Antennas Propag. 45, 1741-1748 (1997). 32. Elzinga, K. et al. Brief electrical stimulation improves nerve regeneration after delayed repair in Sprague Dawley rats. Exp. Neurol. 269, 142-153 (2015). 33. Bonmassar, G. et al. Microscopic magnetic stimulation of neural tissue. Nat. Commun. 3, 921 (2012). 34. Brushart, T. M., Jari, R., Verge, V., Rohde, C. & Gordon, T. Electrical stimulation restores the specificity of sensory axon regeneration. Exp. Neurol. 194, 221-229 (2005). 35. Alam, M. et al. Electrical neuromodulation of the cervical spinal cord facilitates forelimb skilled function recovery in spinal cord injured rats. Exp. Neurol. 291, 141-150 (2017).

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36. Gordon, T., Amirjani, N., Edwards, D. C. & Chan, K. M. Brief post-surgical electrical stimulation accelerates axon regeneration and muscle reinnervation without affecting the functional measures in carpal tunnel syndrome patients. Exp. Neurol. 223, 192-202 (2010). 37. Eldabe, S., Buchser, E. & Duarte, R. V. Complications of spinal cord stimulation and peripheral nerve stimulation techniques: a review of the literature. PainMed. 17, 325-336 (2016). 38. Lauto, A. et al. Photochemical tissue bonding with chitosan adhesive films. Biomed. Eng. Online 9, 47 (2010). 39. Tsao, S. et al. Light-activated tissue bonding for excisional wound closure: a split-lesion clinical trial. Br. J. Dermatol. 166, 555-563 (2012). 40. Perera, T. et al. The clinical TMS society consensus review and treatment recommendations for TMS therapy for major depressive disorder. Brain Stimul. 9, 336-346 (2016). 41. Mawad, D. et al. Lysozyme depolymerization of photo-activated chitosan adhesive films. Carbohydr. Polym. 121, 56-63 (2015).

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Claims (20)

Claims

1.An apparatus for facilitating treatment of tissue, comprising a conductive material arranged to be positioned in contact with the tissue to be treated, to form a tissue/conductor interface, the conductor being arranged to, when under influence from an electromagnetic field, wirelessly receive a stimulation signal, and in response to receiving the stimulation signal being arranged to generate a stimulating response at the tissue/conductor interface, thereby acting as an electrode in which a stimulating response for stimulating the tissue is induced, when wirelessly receiving the stimulation signal.

2. An apparatus in accordance with Claim 1, wherein the conductive material comprises a loop or part-loop.

3. An apparatus in accordance with Claim 2, wherein the circumferential length of the loop is longer than the loops width or thickness.

4. An apparatus in accordance with Claim 2 or Claim 3 wherein the loop is arranged to extend, in operation, around or part-way around tissue being treated.

5. An apparatus in accordance with Claim 4, wherein the tissue is nerve tissue, and the loop or part-loop is arranged to extend around or part-way around the circumference of the nerve, in contact with the nerve tissue.

6. An apparatus in accordance with any one of the

20220251_1 preceding claims, wherein the conductive is mounted to a substrate.

7. An apparatus in accordance with Claim 6, wherein the substrate comprises a bio-adhesive material.

8.An apparatus in accordance with Claim 6 or Claim 7, wherein the substrate is arranged to be formed into a graft for mounting to the tissue, with the elongate conductor in contact with the tissue.

9. An apparatus in accordance with Claim 8 wherein the tissue is nerve tissue and the substrate is arranged to be formed into a cylinder which can be mounted around a nerve.

10.An apparatus in accordance with any one of Claims 6 to 9 wherein the conductive material is in the form of a strip deposited onto the substrate.

11.An apparatus in accordance with any one of the preceding claims, arranged to, in operation, in response to the stimulation signal, to generate a potential difference at the tissue/conductor interface.

12.An apparatus in accordance with Claim 11, wherein the tissue is nerve tissue, and the potential difference is such as to generate an action potential within the nerve.

13.An apparatus in accordance with Claim 12, wherein the action potential is a compound action potential.

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14.An apparatus in accordance with any one of the preceding claims, wherein the stimulation signal applied is a magnetic stimulation signal, such as that applied in Transcranial Magnetic Stimulator.

15.An apparatus in accordance with Claim 13, further comprising an electromagnetic stimulator comprising one or more coils.

16.An apparatus in accordance with any one of Claims 1 to 13, implanted within a patient, contacting tissue to be treated.

17.A method of treatment of tissue, comprising the steps of stimulating an apparatus in accordance with any one of Claims 1 to 15, positioned in contact with tissue to be treated, with a stimulation signal.

18.A method in accordance with Claim 16, wherein the stimulation signal is in the form of Transcranial, Transdermal Magnetic Stimulator (TMS).

19.A method of treatment of tissue, comprising the steps of applying an electromagnetic field in range of a conductive material placed in contact with the tissue, to thereby induce a potential difference at an interface between the tissue and the conductive material, the potential difference creating a response within the tissue, the conductive material thereby acting as an electrode in which the stimulating response for stimulating the tissue is induced, when wirelessly receiving the stimulation signal.

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20.A method in accordance with Claim 19, wherein an electromagnetic signal providing a stimulation signal to the conductive material is in the form of Transcranial, Transdermal Magnetic Stimulator (TMS).

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