Self-powered ionic thermoelectric dressing for smart wound monitoring and accelerated healing

Abstract

Disclosed herein is a thermogalvanic cell material suitable for use in a wound dressing, comprising: a biocompatible hydrophobic polymeric material; and a biocompatible ionically- crosslinked hydrogel material, wherein: the biocompatible polymeric material is provided in the form of a non-woven three-dimensional network formed from nanofibers having a first surface, a second surface and a middle portion therebetween; the biocompatible ionically- crosslinked hydrogel material is located in the middle portion of the three-dimensional network, such that the ionically-crosslinked hydrogel material encapsulates at least part of the nanofibers in the middle portion of the non-woven three-dimensional network; and the ionically-crosslinked hydrogel material is crosslinked by at least two multivalent metal ions that form a redox couple. Also disclosed herein are a device suitable for use as a wound dressing, a wound dressing, and a method of making the thermogalvanic cell material.

Description

[0001] SELF-POWERED IONIC THERMOELECTRIC DRESSING FOR SMART WOUND MONITORING AND ACCELERATED HEALING

[0002] Field of Invention

[0003] The present invention generally relates to wound dressings, and more particularly relates to thermogalvanic cell materials suitable for use in wound dressings.

[0004] Background

[0005] The listing or discussion of a prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge.

[0006] Diabetes mellitus is a major clinical and public health problem affecting 10.5% of adults (20- 79 years). In particular, the diabetic wound is a non-healing chronic wound (8-12 weeks to heal) characterized by excessive exudate, bacterial infection, and a hypoxic environment due to vascular abnormalities and immune deficiency. Therefore, the healing process of chronic wounds, represented by diabetic wounds (Fig. 1a), can stall at any of the three overlapping phases of wound regeneration, including inflammation, proliferation, and remodeling, leading to recurrent infections and even deep ulcers. In the clinical management of acute or chronic wounds, dressings play a fundamental role by acting as a temporary barrier, protecting the wound tissue from bacterial invasion, and facilitating a moist environment through effective exudate management. However, clinically available dressings are unable to provide real-time information on wound status and actively adjust the treatment plan.

[0007] To enable active wound management, flexible electronics with integrating multiple sensors and intervention modules have been engaged to monitor changes in the wound microenvironment and respond with active intervention. The detected physiological conditions include pH, temperature, impedance, motion, biomarkers, bacterial load, etc. The intervention means include UV or NIR light, drug delivery, and electrical stimulation. Among them, electrical stimulation (ES) has emerged as an indispensable tool because it can be coupled with the endogenous electrical field to regulate wound re-epithelialization. The intensive studies of the smart dressing also confirmed the mechanisms of ES for wound healing in terms of fibroblast differentiation, keratin formation, vascularization, and macrophage polarization. Indeed, electronics have helped to make wound care more intelligent, but also with less clinical applicability. That is, it does not meet the requirements of being flexible, breathable, biocompatible and cuttable because the layout of the electronic components is based on a flex printed circuit board (FPCB). As an improvement, a hydrogel layer has been introduced to bridge the wound bed and dressing, and the hydrogel can reversibly adhere to the tissue. Even though the impermeability of FPCB and the rigidity of electronic components remain unchanged. Another limitation is that, as an electronic component, an external power source is required inevitably. Despite the recent progress on either wireless power supply or triboelectric nanogenerator, achieving a genuinely zero-power platform without compromising the treatment experience is still challenging.

[0008] Therefore, there exists a need for new self-powered systems for wound healing and management.

[0009] Summary of Invention

[0010] Aspects and embodiments of the invention are provided in the following numbered clauses.

[0011] 1. A thermogalvanic cell material suitable for use in a wound dressing, comprising: a biocompatible hydrophobic polymeric material; and a biocompatible ionically-crosslinked hydrogel material, wherein: the biocompatible polymeric material is provided in the form of a non-woven three-dimensional network formed from nanofibers having a first surface, a second surface and a middle portion therebetween; the biocompatible ionically-crosslinked hydrogel material is located in the middle portion of the three-dimensional network, such that the ionically-crosslinked hydrogel material encapsulates at least part of the nanofibers in the middle portion of the non-woven three-dimensional network; and the ionically-crosslinked hydrogel material is crosslinked by at least two multivalent metal ions that form a redox couple.

[0012] 2. The thermogalvanic cell material according to Clause 1 , wherein the biocompatible hydrophobic polymeric material is selected from one or more of the group consisting of a polycaprolactone, a polylactic acid, a polyglycolic acid, a poly(p-dioxocyclohexanone), a polytetrafluoroethylene, a polyvinylidene fluoride, a polyester, a polypropylene, and a thermoplastic polyurethane.

[0013] 3. The thermogalvanic cell material according to Clause 2, wherein the biocompatible hydrophobic polymeric material is a thermoplastic polyurethane. 4. The thermogalvanic cell material according to any one of the preceding clauses, wherein the biocompatible ionically-crosslinked hydrogel material is selected from one or more of the group consisting of alginate, a polyvinvyl glycol, a polyacrylic acid, a polyacrylamide, and a polyethylene glycol.

[0014] 5. The thermogalvanic cell material according to Clause 4, wherein the biocompatible ionically-crosslinked hydrogel material is alginate.

[0015] 6. The thermogalvanic cell material according to any one of the preceding clauses, wherein the multivalent metal ions that form a redox couple are selected from Fe2+ / Fe3+, Cu2+ / Cu3+, and Mn2+ / Mn3+.

[0016] 7. The thermogalvanic cell material according to Clause 6, wherein the multivalent metal ions that form a redox couple is Fe2+ / Fe3+.

[0017] 8. The thermogalvanic cell material according to any one of the preceding clauses, wherein the thermogalvanic cell material displays one or more of the following properties:

[0018] (ai) a Young’s modulus of greater than 1 kPa, such as from 10.0 to 10.4 kPa, such as from 10.1 to 10.2 kPa;

[0019] (aii) an elongation to break of greater than 100%, such as greater than 1 ,000%; and (aiii) an ionic conductivity of up to 3 S nrr1, such as up to 2 S nr1, such as about 1.84 S nrr1.

[0020] 9. The thermogalvanic cell material according to any one of the preceding clauses, wherein the thermogalvanic cell material displays a water vapour transmission rate of from 3 to 10 kg / m2-24 h, such as from 6 to 9 kg / m2*24 h, such as from 6.74 to 8.70 kg / m2*24 h.

[0021] 10. The thermogalvanic cell material according to any one of the preceding clauses, wherein a weight to weight ratio of the at least two multivalent metal ions that form a redox couple is from 20:1 to 1 :20 for a first multivalent metal ion to a second multivalent metal ion, such as from 10:1 to 1 :10, such as from 5:1 to 1 :5, such as from 2:1 to 1:2, such as about 1 :1.

[0022] 11. The thermogalvanic cell material according to any one of the preceding clauses, wherein the biocompatible ionically-crosslinked hydrogel material further comprises a biocompatible monovalent metal ion. 12. The thermogalvanic cell material according to Clause 12, wherein the biocompatible monovalent metal ion is selected from one or more of the group consisting of Li+, and more particularly, Na+, and K+, optionally wherein a weight to weight ratio of the monovalent metal ion to the total weight of the at least two multivalent metal ions is from 1 :3 to 1 :20, such as from 1 :4 to 1 :12, such as about 1 :6.

[0023] 13. The thermogalvanic cell material according to any one of the preceding clauses, wherein the thermogalvanic cell material generates an exogenous electric field when placed on a substrate and where the substrate has a temperature that is different to the ambient environment.

[0024] 14. The thermogalvanic cell material according to Clause 13, wherein when the temperature difference is about 5 K, then the voltage of the electric field generated by the thermogalvanic cell material is from 10 to 60 mV, such as from 20 to 55 mV, such as from 40 to 50 mV.

[0025] 15. The thermogalvanic cell material according to any one of the preceding clauses, wherein when: the thermogalvanic cell material is placed on substrate, such that the second surface of the biocompatible polymeric material is in contact with the substrate; and an external power source is connected by the attachment of a first electrode to the first surface of the biocompatible polymeric material and a second electrode to the second surface of the biocompatible polymeric material, then a cooling temperature difference of from 1 to 5 K, such as from 2 to 4 K, is achieved between the temperature of the first surface and the second surface of the biocompatible polymeric material when a current of about 1 A is applied by the external power source.

[0026] 16. The thermogalvanic cell material according to any one of the preceding clauses, wherein a weight to weight ratio of the biocompatible hydrophobic polymeric material to the biocompatible ionically-crosslinked hydrogel material is from 1 :1.5 to 1 :4, such as from 1 :2 to 1:3, such as about 1.5:2.

[0027] 17. A device suitable for use as a wound dressing, the device comprising: a thermogalvanic cell material according to any one of Clauses 1 to 16; and a flexible printed circuit board, comprising one or more components, electrically connected to the thermogalvanic cell material. 18. The device according to Clause 17, wherein the one or more components include one or more of: a controlling unit, e g. a central processing unit or a microcontroller unit; a Bluetooth low energy module; an analogue to digital converter; a signal amplifier; and a power management module.

[0028] 19. A wound dressing comprising a thermogalvanic cell material according to any one of Clauses 1 to 16.

[0029] 20. The wound dressing according to Clause 19, further comprising a flexible printed circuit board, comprising one or more components, electrically connected to the thermogalvanic cell material.

[0030] 21. The wound dressing according to Clause 20, wherein the one or more components include one or more of: a controlling unit, e.g. a central processing unit or a microcontroller unit; a Bluetooth low energy module; an analogue to digital converter; a signal amplifier; and a power management module.

[0031] 22. A thermogalvanic cell material according to any one of Clauses 1 to 16, a device according to Clause 17 or Clause 18, or a wound dressing according to any one of Clauses 19 to 21, for use in treating a wound.

[0032] 23. Use of a thermogalvanic cell material according to any one of Clauses 1 to 16, a device according to Clause 17 or Clause 18, or a wound dressing according to any one of Clauses 19 to 21, in the manufacture of a medicament for treating a wound.

[0033] 24. A method of treating a wound on a subject comprising the steps of applying one of: a thermogalvanic cell material according to any one of Clauses 1 to 16; a device according to Clause 17 or Clause 18; or a wound dressing according to any one of Clauses 19 to 21, to the wound. 25. A thermogalvanic cell material according to any one of Clauses 1 to 16, a device according to Clause 17 or Clause 18, or a wound dressing according to any one of Clauses 19 to 21, for use in medicine.

[0034] 26. A method of making a thermogalvanic cell material according to any one of Clauses 1 to 16, the method comprising the steps of:

[0035] (a) providing a thermogalvanic cell precursor material, comprising: a biocompatible hydrophobic polymeric material; and a biocompatible ionically-crosslinked hydrogel material, wherein: the biocompatible polymeric material is provided in the form of a non-woven three-dimensional network formed from nanofibers having a first surface, a second surface and a middle portion therebetween; the biocompatible ionically-crosslinked hydrogel material is located in the middle portion of the three-dimensional network, such that the ionically-crosslinked hydrogel material encapsulates at least part of the nanofibers in the middle portion of the non-woven three-dimensional network; and the ionically-crosslinked hydrogel material is crosslinked by a bivalent metal ion; and

[0036] (b) immersing the thermogalvanic cell precursor material in a redox couple solution comprising at least two multivalent metal salts, where the at least two multivalent metal ions form a redox couple.

[0037] 27. The method according to Clause 26, wherein the at least two multivalent metal ions are a first multivalent metal ion and a second multivalent metal ion and a weight to weight ratio of the first multivalent metal ion to the second multivalent metal ion is from 20:1 to 1:20, such as from 10:1 to 1 :10, such as from 5:1 to 1 :5, such as from 2:1 to 1 :2, such as about 1 :1.

[0038] 28. The method according to Clause 26 or Clause 27, wherein the biocompatible ionically- crosslinked hydrogel material further comprises a biocompatible monovalent metal ion.

[0039] 29. The method according to Clause 28, wherein the biocompatible monovalent metal ion is selected from one or more of the group consisting of Li+, and more particularly Na+, and K+, optionally wherein a weight to weight ratio of the monovalent metal ion to the total weight of the at least two multivalent metal ions is from 1 :3 to 1:20, such as from 1 :4 to 1:12, such as about 1 :6. 30. The method according to any one of Clauses 26 to 29, wherein the thermogalvanic cell precursor material is provided by:

[0040] (ai) providing a pre-hydrogel composite material, comprising: a biocompatible hydrophobic polymeric material; and a biocompatible pre-hydrogel material, wherein: the biocompatible polymeric material is provided in the form of a non-woven three-dimensional network formed from nanofibers having a first surface, a second surface and a middle portion therebetween; the biocompatible pre-hydrogel material is located in the middle portion of the three-dimensional network, such that the pre-hydrogel material coats a surface of at least part of the nanofibers in the middle portion of the non-woven three-dimensional network; and

[0041] (b) the pre-hydrogel composite material is immersed in a coagulation bath to generate the thermogalvanic cell precursor material.

[0042] 31. The method according to Clause 30, wherein the pre-hydrogel composite material is prepared by:

[0043] (bi) providing a solution comprising an organic solvent and the biocompatible polymeric material and subjecting it to an electrospinning for a first period of time onto a collector plate to generate the first surface formed of nanofibers of the biocompatible polymeric material;

[0044] (bii) subsequently combining the electrospinning with a simultaneous spraying of the biocompatible pre-hydrogel material onto the collector for a second period of time, so as to provide nanofibers of the biocompatible polymeric material coated with the pre-hydrogel material; and

[0045] (biii) subsequently continuing the electrospinning for a third period of time onto a collector plate to generate the second surface formed of nanofibers of the biocompatible polymeric material.

[0046] Drawings

[0047] Fig. 1 depicts the schematics of the self-powered and wireless TGC dressing for accelerated wound healing and monitoring, a, TGC dressing facilitates wound healing in three phases: inflammation, proliferation, and remodeling, b, TGC dressing generates exogenous electric fields that facilitate wound healing by guiding and expediting the migration of epithelial cells, c, Diagram of a TGC dressing on an infected diabetic foot wound, d, The mechanism of redox couple on antibacterial activity, e, A wirelessly graphic interface of wound monitoring (GIWM) to monitor wound potential and temperature characteristics for wound management, f, TGC dressing is designed for wound healing while monitoring respiratory rate at rest for early warning.

[0048] Fig. 2 depicts the fabrication and structural properties of TGC dressing, a, Photographs showing the rapid gelation of Fe2+((i)-(iii)) and (Fe2+)n / (Fe3+)m((iv)-(vi)) with NaAIg sols, b, Strain-dependent rheology of hydrosol, and hydrogels from 0.01 to 100% at 293K. c, Frequency-dependent rheology of hydrosol and hydrogels, d, Optical image of the resulting large-scale TGC dressing using Fe2+ / Fe3+redox couples, e, The top layer of TGC dressing, f, The observed fiber spiral knotting caused by gel cross-linking, g, TGC hydrogel was composited with nanofiber frameworks, h, The AFM characterizations of surface roughness for TGC hydrogel and TPU (thermoplastic polyurethane) film, i, X-ray photoelectron spectroscopy (XPS) spectra analysis of Fe 2p and S 2p orbitals, j, The diagram depicts the chemical process in which divalent Fe2+entirely displaces Na+in NaAIg sols.

[0049] Fig. 3 depicts the rheological behavior of TGC hydrogel. a,d, Storage and loss modulus of strain. b,e, Storage and loss modulus concerning angular frequency. c,f, Shear viscosity at varied shear rates.

[0050] Fig. 4 depicts the preparation process for the TGC dressing, a, The film resulted from the continuous electrostatic spinning, b, The film resulted from the cross-linked reaction using Fe2+. c, The film resulted from the cross-linked reaction using the Fe2+ / Fe3+redox couples.

[0051] Fig. 5 depicts microstructure characterization of TGC dressing, a, Optical image of a three- dimensional fiber network synthesized by electrostatic spinning combined with NaAIg powder coating, b-c, Scanning electron microscopy (SEM) images of the interlaced fiber network structure in hydrogel dressing. d,e, SEM image of TGC dressing after cross-linking and freeze- drying. f, Surface morphology of TGC dressing, g-l, A typical morphology and corresponding elemental mapping spectra indicate the densified morphological structure of the dressing surface after cross-linking and freeze-drying, which facilitates the enhancement of mechanical properties.

[0052] Fig. 6 depicts the Fe content in TGC dressing, a, The content of FeSO4 for the TGC dressing with the concentration of 4-15 wt .%. b, The swelling ratio of the hydrogel was 63.5%. Thus, the calculated amount of Fe absorbed from the redox couple solution (FeSC : Fe2(SO4)3: NaCI = 3 wt.%: 3 wt .%: 1 wt .%) was 1.94 wt.%. c, The actual adsorption amounts of Fe in TGC dressing after a second cross-linking with the redox couple solution and rinsed with deionized water. Values represent the mean ± SD. Differences between the two groups were determined by one-way analysis of variance (AN OVA) and followed by least significant difference (LSD) multiple comparisons.

[0053] Fig. 7 depicts the XPS and Fourier transform infrared spectroscopy (FTIR) analysis of the TGC dressing, a, Global XPS patterns of TGC dressing with varied concentrations of (Fe2+)n / (Fe3+)3(n = 7, 9, 11, 13). Enlarged XPS patterns of b, TPU / NaAIg; c, (Fe2+)7 / (Fe3+)3; d, (Fe2+)g / (Fe3+)3and e, (Fe2+)n / (Fe3+)3. f, FTIR spectra for dried TGC dressing cross-linked by different concentrations of (Fe2+)n / (Fe3+)3(n = 7, 9, 11 , 13, and 18). g, The corresponding FTIR for TPU and TPU / NaAIg, and inset is the molecular structure of TPU.

[0054] Fig. 8 depicts mechanical property, exudate management and ion leakage of TGC dressing, a, Loading-unloading measurement of the (Fe2+)i3 / (Fe3+)3dressing under continuously variable strains, b, Fatigue tensile test with 50% strain on the dressing, c, Hysteresis curves of the dressings during fatigue cycles, d, Schematic process of customization and trimability of TGC dressing, e, The water-vapor transmission rate of dressings was tested using the Paddington cup method, f, Mechanism of the self-pumping dressing with unidirectional actuation of water transport, g, The amount of Fe ions leaked from the TGC dressing to phosphate buffered saline (PBS) over different periods, h, Net Fe ions leakage, i, The cytotoxicity properties of FeSC and Fe2(SC>4)3were determined using the CCK-8 method. Values represent the mean ± SD (n= 4 in i). Differences between the two groups were determined by one-way ANOVA and followed by LSD multiple comparisons.

[0055] Fig. 9 depicts wettability of TPU and TGC dressing. The unidirectional water transport of dressing with a hydrophobic-hydrophilic gradient structure is distinct from the pure TPU membrane.

[0056] Fig. 10 depicts comparison of thermopower for Fe-based redox couples. The thermopower of Fe-AIg gel electrolyte compared to other liquid electrolytes.

[0057] Fig. 11 depicts thermogalvanic properties of TGC dressing, a, Schematic of the platform for thermopower measurements, b, Thermopower (Se) of the (Fe2+)7 / (Fe3+)3dressing (2.2 mV K'1). c, (Fe2+)9 / (Fe3+)3dressing (1.7 mV K1). d, (Fe2+)11 / (Fe3+)3dressing (3.6 mV K-1). e, (Fe2+)i3 / (Fe3+)3dressing (1.8 mV K1). f, Effective ionic conductivity for the TGC dressing at different temperatures.

[0058] Fig. 12 depicts thermogalvanic effects of TGC dressing and enhancement of wound electric field (EF). a, Thermopower of the TGC dressing with different redox couple systems (Han, C.- G. et al., Science 2020, 368, 1091-1098; Taheri, A. et al., ChemSusChem 2018, 11, 2788- 2796; Yang, P. et al., Angew. Chem. Int. Ed. 2016, 55, 12050-12053; Liu, Y. et al., Adv. Energy Mater. 2020, 10, 2002539; Jin, L. et al., ACS Energy Lett. 2016, 1, 654-658; and Wu, J., Black, J. J. & Aldous, L., Electrochimica Acta 2017, 225, 482—492). b, Comparison of electrical conductivities between TGC dressings and other thermoelectric hydrogel systems (Han, C.-G. etal., Science 2020, 368, 1091-1098; Yang, P. etal., Angew. Chem. Int. Ed. 2016, 55, 12050-12053; Liu, Y. et al., Adv. Energy Mater. 2020, 10, 2002539; and Jin, L. etal., ACS Energy Lett. 2016, 1, 654-658). c, The power density of dressing under positive AT. d, Power density of dressing under negative AT. e, Sensitive response characteristics of voltage vs temperature difference, f, TGC / wound / tissue model (i), numerical simulation of the temperature (ii), potential (iii), and electric field distribution (iv) between the wound and TGC dressing, g, Schematic diagram of in situ potential difference measurements between the wound bed and edge, h, The initial potential difference between the wound bed and the edge, i, The potential difference tested with TGC dressing.

[0059] Fig. 13 depicts current density and power density vs. voltage of the TGC dressing, a, (Fe2+)7 / (Fe3+)3. b, (Fe2+)9 / (Fe3+)3. c, (Fe2+)i3 / (Fe3+)3, where the cold terminal is 298 K. d, Comparison of the TGC dressing in this work with previously reported quasi-solid thermocells in terms of normalized output power density.

[0060] Fig. 14 depicts the platform for simulating the voltage output of the TGC dressing on skin wounds in vitro, a, Linear response of the rate of change of power density with temperature difference, b, Schematic (i), photograph (ii), and the corresponding thermal image (iii) of TGC dressing on simulated skin wounds in vitro.

[0061] Fig. 15 depicts three-dimensional finite element analysis (3D-FEA) of the electric field transmission with a TGC dressing on a skin wound, a, The TGC / Wound / Tissue model, b, Infrared thermal images of the skin and TGC dressing, c, Potential distribution, d, The top view of current density distribution.

[0062] Fig. 16 depicts the potential cooling properties of TGC dressing, a, Measured temperature difference of the TGC dressing under an external current (1-1.5A). b,c, Visualization of temperature distribution of the TGC dressing with a conductivity of 2 Snr1.

[0063] Fig. 17 depicts in situ measurements of the potential difference between the wound center and the epidermis at the wound edge of a rat. a, The initial potential difference between the wound center and edge, b, The potential difference changes after placement of the TGC dressing.

[0064] Fig. 18 depicts schematic diagram of the standardized antimicrobial experiment process. The process includes bacterial suspension, detached by ultrasonic and agar plate count.

[0065] Fig. 19 depicts in vitro and in vivo biocompatibility and healing properties of TGC dressing. a,b, Antibacterial rate of the NaAIg and TGC dressing to S. aureus (a) and P. aeruginosa (b) acquired from agar plate count. Values represent the mean ± s.d. (n = 5). c, Agar plate images of (a, b). d, Fluorescence images of F-actin and Col-I staining of L929 cells cultured with the NaAIg or TGC dressing extract on day 3, Dulbecco's Modified Eagle Medium (DMEM) medium was set as the control, e, Schematic illustration of the therapeutic efficacies study of TGC dressing on diabetic mouse wounds, f, Masson’s staining of SD rat wounds on day 14. The black triangles marked wound margins. HPE: hyperproliferative epidermis, ES: eschar, and G: granulation tissue, g, Representative immunofluorescence images for CD31 and a-SMA, blue fluorescence: cell nuclei (DAPI); red fluorescence: blood vessels (CD31); green fluorescence: fibroblast (a-SMA); dashed line: epidermis border. h,i, Volcano plots of gene expression profiles when comparing TGC dressing against cotton gauze (h) and NaAIg dressing (i). j, Schematic illustration of the therapeutic efficacies study of TGC dressing on porcine bacterial infection wounds, k, Masson’s staining of porcine wounds on day 14. I, Representative macroscopic views of the wound under different treatments at each time point, m, Quantification of the open wound closure rate, n, Bacterial CFU count of the wound surface. Differences between the two groups were determined by one-way ANOVA and followed by LSD multiple comparisons.

[0066] Fig. 20 depicts antibacterial effect of TGC dressing. Live / Dead fluorescence staining of S. aureus and P. aeruginosa after contact with NaAIg or TGC dressing for 30 minutes.

[0067] Fig. 21 depicts cytotoxicity of dressing extract, a, Live / Dead fluorescence staining, b, CCK-8 analysis of L929 cells cultured in dressing extracts on days 1 and 3, DMEM medium was set as control.

[0068] Fig. 22 depicts cytocompatibility of TGC dressing extract. a,b, Fluorescence images of F-actin and Col-I staining of L929 cells cultured with the NaAIg or TGC dressing extract on day 1 and day 5, and the DMEM medium was set as the control. Fig. 23 depicts the voltage output for the TGC dressing. The voltage output of the TGC dressing was kept at 37 °C by the heating stage (stimulation of the skin temperature) on the hot side, a, The voltage output measured on the cold side, b, The voltage output when no temperature difference was applied, c, The voltage output measured on the hot side.

[0069] Fig. 24 depicts electric stimulation in cell scratch assay using TGC dressing, a, Illustration of the electric stimulation device. b,c, The temperature gradient (room temperature and a 37 °C heating stage) was applied to the top and bottom sides of the dressing.

[0070] Fig. 25 depicts cell scratch assay. a,b, Cell scratch closure rate for L929 cells. c,d, Cell scratch closure rate for HUVECS cells. All were tested after electric stimulation.

[0071] Fig. 26 depicts Streptozotocin (STZ)-induced diabetic excisional wound model. Three fullthickness wounds (d = 10 mm) were created on the back of the SD rat and covered with cotton gauze (control), NaAIg dressing, and TGC dressing.

[0072] Fig. 27 depicts general observation of wound healing process. Images of the wound under different treatments were taken on day 0, day 3, day 7, and day 14.

[0073] Fig. 28 depicts infrared thermal images of the wound. Images of the wound under different treatments were taken on day 0, day 3, day 7, and day 14. The adhered dressing was removed before imaging and measurement.

[0074] Fig. 29 depicts histology analysis of STZ-induced wound model, a, Masson staining of wounds on day 3 and day 7. The triangles denote wound margins. HPE: hyperproliferative epidermis, ES: eschar, G: granulation tissue. Quantification of the open wound expressed as % of open wound compared to day 0, the HPE length, and the re-epithelialization on b-d, day 3; e-g, day 7; and h-j, day 14. Values in b-j represent the mean ± s.d. (n = 7 in b,e,h, n = 5 in c, d, f, g, i, and j).

[0075] Fig. 30 depicts analysis and quantification of wounds. Quantification of CD31+ vessels, a- SMA+ cells per unit area of diabetic wounds on day 3 (a,b) and day 7 (c,d). Values represent the mean ± s.d. (n = 5).

[0076] Fig. 31 depicts porcine full-thickness defect model, a-c, 9 full-thickness wounds (d = 40 mm) were created on the back of the white porcine, d, Three kinds of dressings were applied at randomized locations, e, The wounds were covered with surgical 3M breathable film and secured with an elastic band, f, The distribution of wounds in the white porcine model.

[0077] Fig. 32 depicts pathological features of three typical wounds. Different healing stages of wounds include a, acute wound; b, chronic wound, and c, recurrent infection, d-f, Temperature characteristic signals for acute, chronic, and recurrent infected wounds.

[0078] Fig. 33 depicts TGC dressing-based portable system for wound monitoring and analysis, a, Photo of the portable module carried on the person, b, Photograph of the integrated wireless wearable module, c, Schematic block diagram of the system, d, The voltage output collected by the designed wireless module when human skin touches the TGC dressing has a sensitive response characteristic with temperature and touch time (i)-(iii). e, The design idea of TGC dressing for wound detection is to take real-time electrical signal (U and I) and time (s) information through signal acquisition, feature extraction, and neural network decision-making to provide the analysis of the inflammatory state of wounds, f, Training results of the neural network, g, The overall performance comparison of TGC dressing, other thermoelectric hydrogels (Han, C.-G. et al., Science 2020, 368, 1091-1098; and Zhu, Y. et al., ACS Appl. Mater. Interfaces 2024, 16, 32466-32480), and cotton gauze. The value of the untested property is set as zero, and measured data are presented as mean ± SD. h, Schematic of the electrical and monitoring tests of the TGC dressing in a bacterial-infected white porcine skin defect model, i, Photos of the infected wound, j, The in situ measured temperature difference (i) between the two sides of the dressing and the obtained voltage output (ii) from the TGC dressing, k, Collected current output of the TGC dressing in porcine.

[0079] Fig. 34 depicts detection and analysis of wound exudate occurrence. a,b, The voltage output of TGC dressing with the addition of PBS at negative and positive temperature differences.

[0080] Fig. 35 depicts developed graphical interface of wound monitoring. A graphical interface of wound monitoring (GIWM) displays the corresponding pathological features of a, the acute wound model, and b, the exudate of the ulcer model.

[0081] Fig. 36 depicts physical diagram of a bacterially infected white porcine skin defect model. This physical device diagram shows a sizeable defective wound, dressing, sensing module, thermometer, and data acquisition terminal for monitoring the in-situ electrical output and temperature properties. Fig. 37 depicts electrical properties of Ca2+crosslinked dressing under a temperature difference between skin and room temperature, a, Testing method, b, The voltage output of the Ca2+crosslinked NaAIg dressing when exposed to a temperature difference between skin and room temperature.

[0082] Description

[0083] It has been surprisingly found that the present disclosure facilitates the spontaneous acceleration of wound healing and enabling monitoring of wound status. In addition, the present disclosure has biomedical compatibility, ability to manage wound exudate with moisture permeability, and allow monitoring of wound temperature, early warning of wound permeate, and display of corresponding pathological characteristics.

[0084] Thus, in a first aspect of the invention, there is provided a thermogalvanic cell material suitable for use in a wound dressing, comprising: a biocompatible hydrophobic polymeric material; and a biocompatible ionically-crosslinked hydrogel material, wherein: the biocompatible polymeric material is provided in the form of a non-woven three-dimensional network formed from nanofibers having a first surface, a second surface and a middle portion therebetween; the biocompatible ionically-crosslinked hydrogel material is located in the middle portion of the three-dimensional network, such that the ionically-crosslinked hydrogel material encapsulates at least part of the nanofibers in the middle portion of the non-woven three-dimensional network; and the ionically-crosslinked hydrogel material is crosslinked by at least two multivalent metal ions that form a redox couple.

[0085] In embodiments herein, the word “comprising” may be interpreted as requiring the features mentioned, but not limiting the presence of other features. Alternatively, the word “comprising” may also relate to the situation where only the components / features listed are intended to be present (e.g. the word “comprising” may be replaced by the phrases “consists of” or “consists essentially of”). It is explicitly contemplated that both the broader and narrower interpretations can be applied to all aspects and embodiments of the present invention. In other words, the word “comprising” and synonyms thereof may be replaced by the phrase “consisting of’ or the phrase “consists essentially of’ or synonyms thereof and vice versa. The phrase, “consists essentially of’ and its pseudonyms may be interpreted herein to refer to a material where minor impurities may be present. For example, the material may be greater than or equal to 90% pure, such as greater than 95% pure, such as greater than 97% pure, such as greater than 99% pure, such as greater than 99.9% pure, such as greater than 99.99% pure, such as greater than 99.999% pure, such as 100% pure.

[0086] As used herein, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a composition” includes mixtures of two or more such compositions, reference to “an oxygen carrier” includes mixtures of two or more such oxygen carriers, reference to “the catalyst” includes mixtures of two or more such catalysts, and the like.

[0087] When used herein, the term “thermogalvanic cell material” refers to a galvanic cell material wherein heat is utilised to provide electrical power directly.

[0088] When used herein, the term “wound dressing” refers to a dressing used to protect a wound, to prevent infection, and to promote healing.

[0089] When used herein, the terms “hydrophobic” refers to a material that has one or more surfaces that are hydrophobic, making these surfaces difficult to wet.

[0090] When used herein, the term “polymeric material” is defined as a substance with repeated molecular units.

[0091] The biocompatible polymeric material is provided in the form of a non-woven three- dimensional network formed from nanofibers having a first surface, a second surface and a middle portion therebetween.

[0092] When used herein, the term “nanofibers” refers to fibers with diameters in the nanometer range.

[0093] When used herein, the term “ionically-crosslinked hydrogel material” refers to a hydrogel material crosslinked by at least two multivalent metal ions that form a redox couple.

[0094] The biocompatible ionically-crosslinked hydrogel material is located in the middle portion of the three-dimensional network, such that the ionically-crosslinked hydrogel material encapsulates at least part of the nanofibers in the middle portion of the non-woven three- dimensional network. Fig. 8f depicts an embodiment of the first aspect of the invention. As shown in Fig. 8f, there is a thermogalvanic cell material 800 that includes a biocompatible hydrophobic polymeric material 810 and a biocompatible ionically-crosslinked hydrogel material 820. The biocompatible polymeric material 810 has a first surface 811 , a second surface 812 and a middle portion therebetween 813. The biocompatible ionically-crosslinked hydrogel material 820 is located in the middle portion 813 of the three-dimensional network.

[0095] Any suitable biocompatible hydrophobic polymeric material may be used. In particular embodiments that may be mentioned herein, the biocompatible hydrophobic polymeric material may be selected from one or more of the group consisting of a polycaprolactone, a polylactic acid, a polyglycolic acid, a poly(p-dioxocyclohexanone), a polytetrafluoroethylene, a polyvinylidene fluoride, a polyester, a polypropylene, and a thermoplastic polyurethane. In further embodiments that may be mentioned herein, the biocompatible hydrophobic polymeric material may be a thermoplastic polyurethane.

[0096] Any suitable biocompatible ionically-crosslinked hydrogel material may be used. In particular embodiments that may be mentioned herein, the biocompatible ionically-crosslinked hydrogel material may be selected from one or more of the group consisting of alginate, a polyvinvyl glycol, a polyacrylic acid, a polyacrylamide, and a polyethylene glycol. In further embodiments that may be mentioned herein, the biocompatible ionically-crosslinked hydrogel material may be alginate.

[0097] Any suitable multivalent metal ions that form a redox couple may be used. In particular embodiments that may be mentioned herein, the multivalent metal ions that form a redox couple may be selected from Fe2+ / Fe3+, Cu2+ / Cu3+, and Mn2+ / Mn3+. In further embodiments that may be mentioned herein, the multivalent metal ions that form a redox couple may be Fe2+ / Fe3+.

[0098] In particular embodiments that may be mentioned herein, the thermogalvanic cell material may display a Young’s modulus of greater than 1 kPa, such as from 10.0 to 10.4 kPa, such as from 10.1 to 10.2 kPa. Details of the Young’s modulus measurement technique are provided in the examples section below.

[0099] In particular embodiments that may be mentioned herein, the thermogalvanic cell material may display an elongation to break of greater than 100%, such as greater than 1,000%. In particular embodiments that may be mentioned herein, the thermogalvanic cell material may display an ionic conductivity of up to 3 S nr1, such as up to 2 S rrr1, such as about 1 .84 S rrr1. Details of the ionic conductivity measurement technique are provided in the examples section below.

[0100] In particular embodiments that may be mentioned herein, the thermogalvanic cell material may display a water vapour transmission rate of from 3 to 10 kg / m2«24 h, such as from 6 to 9 kg / m2*24 h, such as from 6.74 to 8.70 kg / m2-24 h. Details of the water vapour transmission rate measurement technique are provided in the examples section below.

[0101] For the avoidance of doubt, when numerical values are presented in the current application, any suitable combination of the end-points is explicitly contemplated herein. For example, the following water vapour transmission rates are contemplated: from 3 to 9 kg / m2-24 h, from 3 to 8.70 kg / m2-24 h, from 3 to 6.74 kg / m2*24 h, from 3 to 6 kg / m2«24 h; from 6 to 10 kg / m2«24 h, from 6 to 8.70 kg / m2«24 h, from 6 to 6.74 kg / m2«24 h; from 6.74 to 10 kg / m2*24 h, from 6.74 to 9 kg / m2-24 h; from 8.70 to 10 kg / m2*24 h, from 8.70 to 9 kg / m2«24 h; and from 9 to 10 kg / m2*24 h.

[0102] In particular embodiments that may be mentioned herein, a weight to weight ratio of the at least two multivalent metal ions that form a redox couple may be from 20:1 to 1 :20 for a first multivalent metal ion to a second multivalent metal ion, such as from 10:1 to 1 :10, such as from 5:1 to 1 :5, such as from 2:1 to 1 :2, such as about 1 :1.

[0103] In particular embodiments that may be mentioned herein, the thermogalvanic cell material may further comprise a biocompatible monovalent metal ion.

[0104] Any suitable monovalent metal ion may be used. In particular embodiments that may be mentioned herein, the biocompatible monovalent metal ion may be selected from one or more of the group consisting of Li+, Na+, and K+. In further embodiments that may be mentioned herein, the biocompatible monovalent metal ion may be Na+, or K+.

[0105] In particular embodiments that may be mentioned herein, a weight to weight ratio of the monovalent metal ion to the total weight of the at least two multivalent metal ions may be from 1:3 to 1 :20, such as from 1 :4 to 1:12, such as about 1:6. In particular embodiments that may be mentioned herein, the thermogalvanic cell material may generate an exogenous electric field when placed on a substrate and where the substrate has a temperature that is different to the ambient environment.

[0106] In particular embodiments that may be mentioned herein, when the temperature difference is about 5 K, then the voltage of the electric field generated by the thermogalvanic cell material may be from 10 to 60 mV, such as from 20 to 55 mV, such as from 40 to 50 mV. Details of the technique used for the measurement of thermopower are provided in the examples section below. The size of the thermogalvanic cell material used herein for measuring thermopower may be 6 cm long x 2 cm wide x 2 mm thick.

[0107] In particular embodiments that may be mentioned herein, when: the thermogalvanic cell material is placed on a substrate, such that the second surface of the biocompatible polymeric material is in contact with the substrate; and an external power source is connected by the attachment of a first electrode to the first surface of the biocompatible polymeric material and a second electrode to the second surface of the biocompatible polymeric material, then a cooling temperature difference of from 1 to 5 K, such as from 2 to 4 K, may be achieved between the temperature of the first surface and the second surface of the biocompatible polymeric material when a current of about 1 A is applied by the external power source.

[0108] In particular embodiments that may be mentioned herein, a weight to weight ratio of the biocompatible hydrophobic polymeric material to the biocompatible ionically-crosslinked hydrogel material may be from 1 :1.5 to 1 :4, such as from 1 :2 to 1:3, such as about 1.5:2.

[0109] In a second aspect of the invention, there is provided a device suitable for use as a wound dressing, the device comprising: a thermogalvanic cell material according to the first aspect of the invention; and a flexible printed circuit board, comprising one or more components, electrically connected to the thermogalvanic cell material.

[0110] In particular embodiments of the second aspect of the invention that may be mentioned herein, the one or more components may include one or more of: a controlling unit, e g. a central processing unit or a microcontroller unit; a Bluetooth low energy module; an analogue to digital converter; a signal amplifier; and a power management module. Any suitable controlling unit may be used. Any suitable Bluetooth low energy module may be used. Any suitable analogue to digital converter may be used. Any suitable signal amplifier may be used. Any suitable power management module may be used. Examples of such components may be found in the examples section below, but it will be appreciated that any suitable equivalents may be used in place of said exemplified components.

[0111] In a third aspect of the invention, there is provided a wound dressing comprising a thermogalvanic cell material according to the first aspect of the invention.

[0112] In particular embodiments of the third aspect of the invention that may be mentioned herein, the wound dressing may further comprise a flexible printed circuit board, comprising one or more components, electrically connected to the thermogalvanic cell material.

[0113] In particular embodiments of the third aspect of the invention that may be mentioned herein, the one or more components may include one or more of: a controlling unit, e g. a central processing unit or a microcontroller unit; a Bluetooth low energy module; an analogue to digital converter; a signal amplifier; and a power management module.

[0114] Without wishing to be bound by theory, the wound dressing according to the third aspect of the invention is based on the thermoelectric effect to generate an exogenous electric field, thereby facilitating the spontaneous acceleration of wound healing and enabling monitoring of wound status.

[0115] In a fourth aspect of the invention, there is provided a thermogalvanic cell material according to the first aspect of the invention, a device according to the second aspect of the invention, or a wound dressing according to the third aspect of the invention, for use in treating a wound.

[0116] In a fifth aspect of the invention, there is provided use of a thermogalvanic cell material according to the first aspect of the invention, a device according to the second aspect of the invention, or a wound dressing according to the third aspect of the invention, in the manufacture of a medicament for treating a wound. In a sixth aspect of the invention, there is provided a method of treating a wound on a subject comprising the steps of applying one of: a thermogalvanic cell material according to the first aspect of the invention; a device according to the second aspect of the invention; or a wound dressing according to the third aspect of the invention, to the wound.

[0117] In a seventh aspect of the invention, there is provided a thermogalvanic cell material according to the first aspect of the invention, a device according to the second aspect of the invention, or a wound dressing according to the third aspect of the invention, for use in medicine.

[0118] In an eighth aspect of the invention, there is provided a method of making a thermogalvanic cell material according to the first aspect of the invention, the method comprising the steps of:

[0119] (a) providing a thermogalvanic cell precursor material, comprising: a biocompatible hydrophobic polymeric material; and a biocompatible ionically-crosslinked hydrogel material, wherein: the biocompatible polymeric material is provided in the form of a non-woven three-dimensional network formed from nanofibers having a first surface, a second surface and a middle portion therebetween; the biocompatible ionically-crosslinked hydrogel material is located in the middle portion of the three-dimensional network, such that the ionically-crosslinked hydrogel material encapsulates at least part of the nanofibers in the middle portion of the non-woven three-dimensional network; and the ionically-crosslinked hydrogel material is crosslinked by a bivalent metal ion; and

[0120] (b) immersing the thermogalvanic cell precursor material in a redox couple solution comprising at least two multivalent metal salts, where the at least two multivalent metal ions form a redox couple.

[0121] In particular embodiments of the eighth aspect of the invention that may be mentioned herein, the at least two multivalent metal ions may be a first multivalent metal ion and a second multivalent metal ion and a weight to weight ratio of the first multivalent metal ion to the second multivalent metal ion may be from 20:1 to 1 :20, such as from 10:1 to 1 :10, such as from 5:1 to 1:5, such as from 2:1 to 1 :2, such as about 1 :1. In particular embodiments of the eighth aspect of the invention that may be mentioned herein, the biocompatible ionically-crosslinked hydrogel material may further comprise a biocompatible monovalent metal ion.

[0122] In particular embodiments of the eighth aspect of the invention that may be mentioned herein, the biocompatible monovalent metal ion may be selected from one or more of the group consisting of Li+, Na+, and K+. In further embodiments of the eighth aspect of the invention that may be mentioned herein, the biocompatible monovalent metal ion may be Na+, or K+.

[0123] In particular embodiments of the eighth aspect of the invention that may be mentioned herein, a weight to weight ratio of the monovalent metal ion to the total weight of the at least two multivalent metal ions is from 1 :3 to 1 :20, such as from 1 :4 to 1:12, such as about 1 :6.

[0124] In particular embodiments of the eighth aspect of the invention that may be mentioned herein, the thermogalvanic cell precursor material may be provided by:

[0125] (ai) providing a pre-hydrogel composite material, comprising: a biocompatible hydrophobic polymeric material; and a biocompatible pre-hydrogel material, wherein: the biocompatible polymeric material is provided in the form of a non-woven three-dimensional network formed from nanofibers having a first surface, a second surface and a middle portion therebetween; the biocompatible pre-hydrogel material is located in the middle portion of the three-dimensional network, such that the pre-hydrogel material coats a surface of at least part of the nanofibers in the middle portion of the non-woven three-dimensional network; and

[0126] (b) the pre-hydrogel composite material is immersed in a coagulation bath to generate the thermogalvanic cell precursor material.

[0127] In particular embodiments of the eighth aspect of the invention that may be mentioned herein, the pre-hydrogel composite material may be prepared by:

[0128] (bi) providing a solution comprising an organic solvent and the biocompatible polymeric material and subjecting it to an electrospinning for a first period of time onto a collector plate to generate the first surface formed of nanofibers of the biocompatible polymeric material;

[0129] (bii) subsequently combining the electrospinning with a simultaneous spraying of the biocompatible pre-hydrogel material onto the collector for a second period of time, so as to provide nanofibers of the biocompatible polymeric material coated with the pre-hydrogel material; and (biii) subsequently continuing the electrospinning for a third period of time onto a collector plate to generate the second surface formed of nanofibers of the biocompatible polymeric material.

[0130] Any suitable organic solvent may be used. Examples of suitable organic solvents include, but are not limited to ketones (e.g. methyl ethyl ketone, acetone, and cyclohexanone), lower alkyl esters (e.g. ethyl acetate, and butyl acetate), chlorinated hydrocarbons (e.g. trichloroethylene, and dichloromethane), aromatic hydrocarbons (e.g. toluene, and xylene), dimethylformamide, tetrahydrofuran, and mineral turpentine or combinations thereof. For example, the organic solvent may be a mixture of dimethylformamide and dichloromethane. As will be appreciated, a mixture of organic solvents may be used to improve solubility and regulate volatility.

[0131] For example, the solubility parameter of polyurethane (PU) is about 10, so ketones may be selected as the organic solvent.

[0132] Any suitable first period of time may be used. For example, the first period of time may be from 5 minutes to 1 hour, such as about 12 minutes.

[0133] Any suitable second period of time may be used. For example, the second period of time may be from 10 minutes to 2 hours, such as about 20 minutes.

[0134] Any suitable third period of time may be used. For example, the third period of time may be from 2 minutes to 1 hour, such as from 5 minutes to 15 minutes, such as about 8 minutes.

[0135] As will be appreciated, the present disclosure provides the following advantages:

[0136] • working mechanism: it is demonstrated herein that the TGC dressing converts the temperature gradient between the wound and the environment into an external electric field (EF), which couples with the wound’s endogenous EF to enable wound monitoring and electrical stimulation. Unlike most reported working mechanisms of electrical stimulation for wound healing, the TGC dressing in the present disclosure provides zero-powered and comfortable medical care;

[0137] • biomedical compatibility: existing ionic thermoelectric systems rely on the movement of metal ions to generate electric potentials, but the toxicity of these ions to cells and tissues cannot be avoided, severely restricting their biomedical applications. This critical issue has been effectively addressed in the present disclosure. The polyanionic heteroionic structure of alginate chelates with metal cations, limiting the movement of ions within the hydrogel’s molecular network and preventing ion leakage into the wound environment. Moreover, ferrous sulfate and iron sulfate, commonly used in clinical practice, ensure the dressing’s outstanding cytocompatibility and histocompatibility;

[0138] • advances in clinical use: returning to fundamental clinical requirements for wound care materials, one significant advantage of the TGC dressing developed in the present disclosure is its ability to manage wound exudate with moisture permeability comparable to cotton gauze. In contrast, many existing smart dressings are based on impermeable substrates unsuitable for continuous long-term use. Additionally, the 3D nanofibrous network of the TGC dressing withstands 100 cycles of fatigue stretching at 50% strain and can be easily tailored to fit regular or irregular shaped wounds. Importantly, the TGC dressing achieves a bactericidal rate of > 99.999% to P.earuginosa and >99.9% to S.aureus after 30 minutes of static contact; and

[0139] • intelligent healthcare: a fully integrated wound monitoring interface has been developed to correlate between wirelessly monitored wound voltage signals and temperature characteristics of different types of wound development stages, allowing monitoring of wound temperature, early warning of wound permeate, and display of corresponding pathological characteristics.

[0140] Further aspects and embodiments of the invention will now be discussed by reference to the following non-limiting examples.

[0141] Examples

[0142] Materials

[0143] FeSO4 was purchased from Sinopharm Chemical Reagent Co. , Ltd. Fe2(SO4)3, sodium alginate (A2033) and NaCI were purchased from Sigma. TPU was purchased from BASF. All the other chemicals, reagents and solvents were purchased from commercial sources.

[0144] Scanning electron microscope (SEM) analysis was carried out on a JEOL JSM-7600F instrument, and the corresponding energy dispersive X-ray spectroscopy (EDX) was carried out on the supplied elemental mapping. Atomic force microscopy (AFM) images were obtained using an AFM XE-100 instrument. X-ray photoelectron spectroscopy (XPS) was conducted on a Shimadzu Kratos Axis Supra instrument. Fourier transform infrared (FTIR) spectroscopy patterns were acquired at room temperature with a diamond ATR accessory on a PerkinElmer Fourier infrared spectrometer. Optical surface morphology images were captured using a microscope (Olympus BX51). Thermal images were taken with a thermal imaging camera (FLIR T540).

[0145] Trace element analysis

[0146] The amount of elemental iron in samples was determined by ICP-MS (PerkinElmer SCI EX ELAN DRC-e ICP-MS). 1 g of each sample was dissolved in 1 mL of hydrochloric acid (37%) and diluted 1000 times via deionized water for the test. The releasement of Fe ions for TGC dressing was measured in PBS (0.1 M; pH = 7.0). 1 cm2of samples was placed in centrifuge tubes with 10 mL PBS on a mechanical shaker (60 rpm) at 37 °C. 1 mL of the solution was periodically collected and tested by ICP-MS, and 1 mL of fresh PBS was refilled at each time point.

[0147] Statistical analysis

[0148] Values in the graphs are presented as mean ± standard deviation, and all data were checked for normality (n = 3 unless otherwise noted). Differences between the two groups were determined by one-way ANOVA and followed by LSD multiple comparisons using the software SPSS. 20. Statistical significance levels were indicated in the graphs by P value or by (***) for P < 0.001, (**) for P < 0.01, and (*) for P < 0.05.

[0149] Example 1. Preparation and characterization of TGC wound dressing

[0150] A thermogalvanic cell (TGC) dressing based on the thermogalvanic effect to convert the temperature gradient between the wound and dressing into an electric stimulus to generate an exogenous electric field, thereby accelerating wound healing (Figs. 1a-b), was designed and demonstrated. The TGC dressing comprises a Fe2+ / Fe3+cross-linked alginate hydrogel and interpenetrated nanofibers, which provide compatible mechanical and moisture permeability properties. Taking an infected, chronic, non-healing diabetic wound, for example (Fig. 1c), the TGC dressing can be easily cut into different shapes and directly contacted with irregular-shaped wounds and has good antimicrobial properties (Fig. 1d). This highly integrated design allowed the bio-resourced dressing itself to act as an independent biomedical engineering system without external power sources. It advanced the smart dressing towards clinical use. During the wound healing process, a fully integrated graphic interface of wound monitoring (GIWM) has been developed to correlate between wirelessly monitored wound voltage and temperature characteristics of different types of wound development stages (Fig. 1e). The integrated sensing system, utilizing TGC dressings, allows for monitoring respiration rate during a state of rest and enabling early warning (Fig. 1f). Coming to the era of new energy materials, wireless sensing, and booming intelligent interconnection technologies, these results would leave a footprint on the development of wound healing and monitoring, towards intelligent healthcare.

[0151] The TGC dressing was prepared using a modified electrospinning and ionic cross-linking reaction. Firstly, 1.5 g TPU was added into a mixture of 8.5 g DMF and dichloromethane (v / v = 7:3), stirring for 12 h at room temperature to obtain TPU solution (15 wt.%). The electrospinning (Beijing Yongkang Leye ET-X1) was applied at a flow rate of 0.5 mL / h, where the collection distance and selected voltage are 20 cm and 20 kV, respectively. The inner diameter of the spinning needle was 0.7 mm (19 G). After 12 minutes of spinning, 2 g sodium alginate powder was continually sprayed onto the collector for the next 20 minutes. Another 8 minutes of spinning was chosen to make a dense cover. The composite was vacuum-dried to remove residual solvents. Secondly, the composite was submerged in deionized water and well wetted, transferred into different concentrations of FeSC or CaCh solution to crosslink at room temperature for 1 hour, and rinsed with deionised water before a 24 h freeze-drying. The Fe2+cross-linked TGC hydrogel composite and Ca2+cross-linked alginate hydrogels were prepared. Before being applied or tested as TGC dressing, the dried TGC hydrogel composite was further immersed in a redox couple solution (FeSO4:Fe2(SO4)3:NaCI = 3 wt.%:3 wt.%:1 wt.%) for 1 hour, taken out and dipped in deionized water for 1 minute, and blotted out an excess solution with filter paper.

[0152] Example 2. Morphology and chemical structure of TGC wound dressing

[0153] The wound environment is sensitive to heavy metals or reactive materials, which precludes the use of most traditional ionic hydrogel systems. In contrast, Fe is the most abundant trace element in the human body. To achieve wet wound care, alginate hydrogels were chosen. Meanwhile, as a polyanionic heteropolymer, alginate can undergo instantaneous crosslinking and form ionotropic alginate hydrogels in the presence of certain divalent or trivalent cations. In Example 1 , a TGC hydrogel based on an ionotropic alginate network was developed.

[0154] Basics of rheology and viscous behavior

[0155] Rheology describes the deformation of matter (including solids, liquids, or gases) under the influence of stress. This resistance is manifested when one layer of a fluid moves relative to another. The force required to move a fluid against resistance is called shear. The force per unit area needed to produce shear is called shear stress. The resistance of a fluid to any irreversible change in its volume is defined as viscosity. The following equations can express these fundamental laws: where r, y, 77 and v are shear stress, shear rate, shear viscosity and kinematic viscosity, respectively, and F, A, v, h and p are shear force, shear area, velocity, shear gap and density, respectively.

[0156] As for the material which shows the viscoelastic behavior in shear: where y, G, G* and tan 8 are shear deformation, shear modulus, complex shear modulus and loss factor, respectively, and s, rA, yA, G" and G' are deflection path, shear-stress amplitude, strain amplitude, loss modulus and storage modulus, respectively.

[0157] The part of the G* value that runs along the x-axis is the elastic portion of the viscoelastic behaviour presented as G' . In contrast, the part of the G* vector that is projected onto the y- axis is the dense portion G" . The storage modulus G' represents the elastic part of the viscoelastic behavior and approximates the solid-state behavior of the sample. The loss modulus G" represents the dense part of the viscoelastic behavior and can be considered as the liquid state behavior of the sample. For the analysis of the loss factor tan 8, especially when there is a phase transition in the sample. This is also known as the sol / gel transition point or simply the gel point. This means that the nature of the sample has changed during the measurement from a liquid or sol-gel state to a solid or gel state and vice versa. Typically, a liquid is said to be ideally viscous when tan 6 > 100:1 = 100, and a solid is said to be ideally elastic when tan 8 < 1 :100 = 0.01.

[0158] Rheological measurements Rheology properties were measured with the Anton Paar MCR 501 instrument. Amplitude sweeps were performed at an adjustable strain of 10 s1angular frequency. Frequency sweeps were conducted at a variable angular frequency co of 0.5% strain. All measurements were taken at a constant temperature of 20 °C.

[0159] Swelling tests

[0160] The swelling ratio was determined by comparing the weights (W) of the hydrogel before (Wdry) and after (Wwet) soaking in water. A sample of the hydrogel was first freeze-dried for 24 h and immersed in water for 10 minutes at room temperature. The swelling ratio was derived as follows:

[0161] Results and discussion

[0162] As shown in Fig. 2a, NaAIg showed rapid gelation in Fe2+(i)-(iii) and Fe2+ / Fe3+(iv)-(vi) solutions. The effects of Fe2+ / Fe3+concentrations on the rheological behavior of the NaAIg sol and TGC hydrogel were then investigated. Oscillatory measurements indicated (Figs. 2b-c and 3) that samples crosslinked with Fe2+ / Fe3+behaved in a gel-like viscoelastic manner ( > G") within the linear viscoelastic region (plateau region) compared to pure NaAIg sol. This suggests the formation of stable hydrogels, and the gel-sol transition can be easily tuned by varying the Fe2+ / Fe3+concentration. In addition, frequency sweep measurements (Figs. 2c, 3b and 3e) showed that the thermoelectric dressings maintained a constant G' value, about 5 times higher than G", throughout the angular frequency range from 1 to 100 rad / s. This indicates that the Fe2+ / Fe3+crosslinked hydrogels and dressings have a stronger and more ordered network compared to the uncrosslinked NaAIg sol. The TGC dressing also demonstrated shearthinning properties, where viscosity decreases with increasing shear rate.

[0163] For further application as a wound care material, the hydrogel commonly faces two main concerns: the insufficient mechanical property and the biocompatibility risk of direct contact with the wound bed. Inspired by the collagen fiber framework in the human dermis that provides isotropic tensile properties, a nanofiber network was introduced into the TGC hydrogel to improve the elasticity and fatigue behavior. The composite of nanofiber and NaAIg powder transformed into TGC dressing under the crosslinking of FeSO4 (Fig. 4) or FeSO4 / Fe2(SO4)3 and covered a large area (30 cm x 16 cm) (Fig. 2d). For a typical TGC dressing, the production cost is 1.047 m2 / 100 USD (Table 1). SEM showed that the bottom and top layers of the TGC dressing are dense fibrous membranes, among which the TGC hydrogel was composited with a nanofiber framework (Figs. 2e-h and 5). AFM analysis showed that the roughness of TGC hydrogel and TPU layer were 32 nm and 112 nm, respectively (Fig. 2i).

[0164] Table 1. The detailed costs of raw materials used to prepare TGC dressing.

[0165] Usage Production

[0166] Systems Materials Unit price

[0167] / 10 cm2 / 100 USD

[0168] 41.4 USD / 100g

[0169] Polyurethane (PU) 0.005 g

[0170] Dimethylformamide134USD / L

[0171] 0.02 ml

[0172] (DMF)(anhydrous, >99.8%)

[0173] Dichloromethane88 8 USD / L

[0174] 0.00833 ml

[0175] (CH2Cl2)(anhydrous, >99.8%)

[0176] NaAlg-Fe273+ 174 USD / 50°g

[0177] NaAIg 0.03333 g 1.047 m2dressin9 (powder)

[0178] 52.3 USD / 500g

[0179] NaCI 0.01667 g

[0180] (ACS reagent, >99.0%)

[0181] 290 USD / 500g

[0182] FeSO4-7H2O 0.11667 g (99.99% trace metals basis)

[0183] 89.7 USD / 500g

[0184] Fe2(SO4)3 0.05 g

[0185] (ACS reagent, >99.0%)

[0186] Next, we investigated the Fe content of TGC dressings after cross-linking with gradient concentrations of ferrous ions. Since sodium alginate is a polyanionic heteropolymer that can adsorb metal cations against osmotic pressure under electrostatic forces, it is often used as an adsorbent for metal ions. Here, it was also found that after cross-linking in 4-15 wt.% ferrous sulfate solution, the concentration of iron ions within the sodium alginate was even higher than the original FeSC>4 concentration. The saturation concentration reached 12.80 wt.% (Fig. 6a) and no longer increased even after a secondary lyophilization and cross-linked process (Figs. 6b-c). The hydrogel was then rinsed, lyophilized, and further crosslinked with the mixed solution of ferric and ferrous ions (3:3 wt.%). The swelling ratio of the hydrogel was 63.5% (Fig. 6b), so the amount of absorbed Fe was about 3.81 wt.%. However, after crosslinking and rinsing, the actual adsorption amounts in all groups were less than 2.2 wt.% (Fig. 6c). This provides further evidence that there is an upper limit for the reliable retention of iron ions by alginate hydrogels (Figs. 2i and 7a).

[0187] XPS and FTIR analysis of the TGC dressing confirmed the uniform distribution of the secondary cross-linking ions throughout the hydrogel, obtained by hydrogen bonding and supramolecular assembly (Figs. 2j-k and 7). Also, the insert further demonstrates the successful incorporation of Fe2+ / Fe3+redox couple into the hydrogel dressing. The TGC is obtained by hydrogen bonding and supramolecular assembly, as confirmed by the FTIR analysis (Fig. 7f). The FTIR spectrum of the TGC dressing shows an absorption peak corresponding to a carboxyl group at 1708 cm1, indicating the deprotonation of carboxyl groups on alginate chains and their interaction with Fe2+ / Fe3+, which facilitates the hydrogel formation. Compared to the peaks observed in TPU and TPU / NaAIg (Fig. 7g), the TGC dressing also shows widening of the H-0 stretching vibration peaks at 2600-3700 cm-1and 1600-1700 crrr1, respectively. This is mainly due to an increase in the number of hydrogen bonds between water molecules and polymer chains, making the H-0 bonds more easily stretched and bent. The enhanced interactions within the polymer network contribute to a significant mechanical reinforcement of the TGC dressing.

[0188] Example 3. Enhanced mechanical, exudate management, and ion leakage properties

[0189] Wound care materials should be designed with reliable mechanical properties to adapt to body movement and contact in daily life. Commercially available sodium alginate hydrogels including Purilon Gel (Coloplast Ltd.), Flaminal Hydro Alginate Gel (Flen Health UK Ltd.), and Nu-Gel Hydrogel (Systa-genix Wound Management Ltd.), are semi-solid and viscous. When applied to wounds clinically, they are extruded and then used together with other dressings or films. The TGC dressing can be used independently owing to the reinforcement of the nanofiber framework.

[0190] Mechanisms of capillary forces in water transport For biofluidic transport in monolayers, droplets can spontaneously penetrate the membrane under the action of capillary forces. The capillary force originates from the Laplace pressure PL, which can be calculated according to the Young-Laplace equation:

[0191] 4y x cos 6 Pl =D where 9, y and D are the static contact angle on the nanofiber membrane, the surface tension of water in air, and the diameter of the capillary, respectively. Different porous structures can produce synergistic capillary pressure difference (AP) as follows:

[0192] 4y x cos 0?4y x cos 0, P = p - p = - 1

[0193] D2DLwhere Di and D2 are the diameters of the pores of the inner and outer layers, respectively, and 61 and 2 are the corresponding surface water contact angles of the inner and outer membranes, respectively. AP is essential in the driving force that extracts moisture directly from the inner layer to the outer layer. This mechanism follows Murray's law, which optimizes mass transfer by minimizing transport resistance in pores with a given volume.

[0194] In addition, the hydrophilic nanofibers and the hydrophobic nanofibers form a plurality of hydrophobic-hydrophilic contact points. When water droplets contact the hydrophobic nanofibers at the plurality of contact points, the wetting force of the hydrophilic nanofibers wets the pumped water to the hydrophilic nanofibers. In this process, the wetting force PW can be calculated according to the following equation:

[0195] Pw= YPXcos 6 where p denotes the perimeter of the contact line.

[0196] For the pure hydrophobic polyurethane nanofiber membrane, PLiof the hydrophobic nanofibers can prevent water from penetrating the hydrophobic nanofiber membrane. For the designed self-pumping nanofiber membrane, water droplets can contact the hydrophilic nanofibers through multiple contact points, and the P,vof the hydrophilic nanofibers can significantly reduce the hydrostatic pressure compared with the corresponding pure hydrophobic nanofiber membrane. In conclusion, the self-pumping phenomenon and the hydrophobic-hydrophilic gradient structure contribute to the exudate absorption of wound dressing.

[0197] Mechanical tests

[0198] Mechanical tests were carried out on a universal flexible electronic tester (FT2000, Shanghai Prtronic Electronic Technology Co., Ltd.) equipped with commercial accessories (Eidelberg, NK-20) with a resolution of 0.001 N. The samples were cut into 2 cm x 6 cm. The thickness of the sample was 2 mm, which was measured and corrected with vernier calipers before testing. The clamping interval, grip length, and elongation rate were 20 mm, 20 mm, and 60 mm / min, respectively.

[0199] Water vapor transmission rate (WVTR) measurements

[0200] The WVTR was tested based on the YY / T 0148-2006 with some modifications. Dressings were clamped to the cylinders of Paddington cups and filled with distilled water, leaving a 5 ± 1 mm gap between the water and the dressing. The opening area of the samples was calculated as S. Each Paddington cup was weighed before (W) and after (w) soaking, then incubated for 24 h at 37 ± 1 °C. WVT was finally calculated as follows:

[0201] The unit was mL / cm2-24h.

[0202] In vitro cytotoxicity

[0203] The in vitro cytotoxicity was evaluated using L929 cells (the cell bank of the Chinese Academy of Science, China) according to ISO 10993-5-2009. The FeSO4 and Fe2(SO4)3 chemicals were diluted with PBS to a specific concentration. For TGC dressing, 2 cm x 2 cm samples were immersed in 10 mL of complete medium containing 20% serum (79% DMEM, 20% Fetal Bovine Serum (FBS), 1% penicillin-streptomycin solution) for 24 h. The immersed medium was filtered and processed using a sterile filter to prepare an infusion solution for subsequent cell culture studies. DMEM mixed with 5% dimethyl sulfoxide was used as a positive control, and pure DMEM solution was used as a negative control. L929 cells were inoculated in a 96- well plate at 3000 cells / mL density and cultured for 24 h. Then, 100 L of the different group solutions were added to each well. The medium was changed every 24 hours. On days 1 and 3, the viability of L929 was determined by the CCK-8 assay (CCK-8, 100T, Beyotime, Shanghai), Live / dead assay (L3224, Invitrogen) stain according to the manufacturer's instruction manual. Primary antibodies used for immunofluorescence staining were rabbit polyclonal anti-Col I antibody (1 :100, Sigma, HPA008405) and mouse monoclonal anti-F-actin antibody (1 :100, Abeam, ab205). Secondary antibodies were goat-anti-rabbit IgG H&L (1 :250, Abeam, ab150077) and goat-anti-mouse IgG H&L (1 :250, Abeam, ab150115).

[0204] Cell migration

[0205] The cell migration under an electric field was tested using fibroblast L929 and HUVECS (the cell bank of the Chinese Academy of Science, China). The activated cells were seeded in 24- well plates with 4 x 104cells per well and incubated with complete medium (79% DMEM, 20% fetal FBS, 1 % penicillin-streptomycin solution) for 12 h to form a semi-fused layer of cells. Cell scratches with a width of 150-200 m were made. After removing the complete medium, the bottom of the well plate was gently blown with sterile PBS to obliterate the cells shed at the scratch; the PBS-washed cell wells were treated with low-serum (1%) medium culture and photographed using a microscope. The temperature gradient (room temperature and a 37 °C heating stage) was applied to the top and bottom sides of the TGC dressing (4 cm x 4 cm). Then, the cells were stimulated by electric field generated with the TGC dressing for 30 min at each time point and observed. The distance between the two electrodes was 1 cm.

[0206] Results and discussion

[0207] Mechanical properties

[0208] In the cycled tensile test, the dressing was stretched up to 450% of its length without breaking (Fig. 8a), as well as consistent multiple cycles of 100 times at 50% tensile deformation (Figs. 8b-c). Three mechanical tests were used to evaluate the dressing’s performance under extreme tension, fatigue deformation, and suture cutting. The dressing (6 cm long x 2 cm wide x 2 mm thick) was stretched up to 10 times of its own length without breaking, during which the energy dissipation caused different levels of delay (Fig. 8a), with the energy loss increasing from 4.42 MJ / m3at 30% strain to 1133 MJ / m3at 1000% strain. The energy loss coefficient decreased from 54.7% at 30% strain to 35.9% at 200% strain and then climbed up. In a typical elongation process of a fiber / hydrogel composite, three effects contribute to the resistance during elongation, including the straightening and orientation of the nanofibers, the elastic elongation of the fibers and hydrogels, and the slipping and breaking of the macromolecules inside the material. These three factors dominated the early, middle, and late stages of deformation, respectively, and resulted in changes in strain.

[0209] In practice, the dressing is designed to be used in a small-strain environment. Therefore, consistent multiple cycles of 100 times were tested at 50% tensile deformation (Fig. 8b). The dressing exhibited instant resilience and tensile stress of 59.2-64.7 kPa at 50% strain, with the almost coincided retention curves (Fig. 8c). Fig. 8d shows that TGC dressing can be trimmed into various shapes and even be cut into continuous thin fibers for weaving, offering customized coverage for irregular wounds. The concentration of Fe showed no significant effect, indicating that the TPU nanofiber network spared the main mechanical stress.

[0210] Exudate management

[0211] Moreover, effective exudate management is a critical factor in chronic wound healing. Excessive exudate volume poses a risk of peri-wound maceration and excoriation of the surrounding skin, leading to wound deterioration. We evaluated the WVTR rate of TGC dressing using the Paddington cup method (Fig. 8e). With a WVTR rate range of 0.674-0.870 mL / cm2-24h, TGC dressing showed a comparable moisture-penetrability to the single layer cotton gauze, being able to manage typical ulcer wounds (exudate > 0.4 ml_ / cm2-24h) (lizaka, S. et al., J. Wound Care 2011, 20, 453-463). The hydrophobic nanofiber membrane and hydrophilic hydrogel can form a self-pumping dressing with unidirectional actuation of water transport, as explained in Fig. 8f. With this sandwich structure, the TGC dressing could absorb wound exudate and discharge the moisture under air convection (Fig. 9). Notably, the phase transition, as demonstrated by DSC and previously rheology, does not occur gradually before the critical temperature. This prevents unwanted delamination or failure of the i-TE dressing when engaging applications.

[0212] Ion leakage

[0213] Unlike general extracorporeal application, wound dressing is continuously exposed to blood and wound exudate. Hence, the risk of ion leakage of thermoelectric ionic dressings in a liquid environment requires special attention. The dressing was carried to a 7-day sustained release experiment, where PBS (0.1 M, pH = 7.0) simulated wound exudate. The maximum release of Fe was less than 20 pg / cm2(Fig. 8g). The releasement of Fe ions was mainly observed in the first hour. After contact with PBS for 3 h, the dressings continued to swell and exposed new binding sites, showing reabsorption of Fe ions (Fig. 8h). The results proved that the alginate hydrogel also acted as a scavenger for Fe ions, reducing excessive Fe ions release into the wound exudate environment. Considering that the exudate amount of typical ulcer wounds is over 0.4 mL / cm224h, we can calculate that in a typical ulcer wound, the raised concentration of Fe ions in wound exudate was less than 7.14 pg / mL. In contrast, the total iron amount of wound exudate is 3.48-12.65 pg / mL (Yeoh-Ellerton, S. & Stacey, M. C., J. Invest. Dermatol. 2003, 121, 918-925), and the LD50 of FeSO4 and Fe2(SO4)s against fibroblast were over 400 pg / mL (Fig. 8i). More importantly, the hydrogel nature enables customization to address different needs. Fig. 8d shows that after curing, TGC dressing can uniformly conform to various shapes and even be cut into continuous thin fibers for weaving, offering customized coverage for both regular and irregular wounds.

[0214] Example 4. Temperature difference-generated exogenous electric field

[0215] The endogenous electric field (EF) induced by wounds is generated immediately after injury due to the collapse of the transepidermal potential. EF widely engages in tissue regeneration and accelerates wound healing from multiple aspects such as epithelialization, nerve repair, and angiogenesis. Here, we evaluated the ability of TGC dressing to convert the temperature difference between a wound and its ambient environment into an applied electric field. Study on finite element modeling (Blackiow, S. 0. et al., Sci. Adv. 2019, 5, eaaw3963; and Theocharidis, G. et al., Nat. Biomed. Eng. 2022, 6, 1118-1133)

[0216] To quantitatively analyze the therapeutic impact of the exogenous electric field generated by the TGC dressing on skin wounds, we conducted a three-dimensional finite element analysis of the thermoelectric power generation and cooling performance using the commercial- available software COMSOL Multiphysics (Freedman, B. R. et al., Nat. Biomed. Eng. 2022, 6, 1167-1179; and Yang, Y. et al., Nat. Common. 2022, 13, 6908). By modeling various physical modules such as solid heat transfer, electric current, and thermoelectric effects, we established three-dimensional geometric models of the skin and the TGC dressing module within the software interface. This allowed us to obtain the temperature, thermoelectric potential, and electric field distribution at the wound site caused by the TGC dressing. Parameters such as the Seebeck coefficient and electrical conductivity of the TGC dressing were entered based on experimental measurements, with the electrode wire material set to copper. The initial values used in FEA for thermoelectric simulation were listed in the Table 2. The thermoelectric (TE) outputs associated with the geometry were modelled using the Heat Transfer in Solids, Electric Currents and Electrical Circuit modules of the COMSOL Multiphysics software. Specifically, the Heat Transfer in the Solids module was employed to simulate heat conduction, convection, and radiation within the solid domain. The control equation for heat transfer from an external heat source (Qe) can be derived in its differential form based on Fourier's law: where the Cp, p, D, K and T are specific heat capacity, density, thermal diffusivity, thermal conductivity, and absolute temperature, respectively.

[0217] The Electric Current module, as the second component, solves the current conservation equation using Ohm's law: = Qj J = aE +JeE = -V7 where the J, Qj, a, E, Jeand V are induced current, current sources, electrical conductivity, electric field, external current sources, and electric potential, respectively.

[0218] The last module used is the Electrical Circuit module, which simulates the load resistance to record voltage and current outputs under electrically matched conditions. The thermodynamic relationships between the Seebeck effect, Peltier effect and Thomson effect are considered, resulting in the governing equations for TE modelling: q = PJ

[0219] P = ST Je= —aS * VT where the P and S are the Peltier coefficient and the Seebeck coefficient.

[0220] Consequently, the goal of coordinated design for TE device topologies is simplified to solve the geometry-dependent current density and heat flux in devices with variable TE leg dimensions under static heat transfer conditions using finite element modeling. For material selection, the simulated TE characteristics of the TGC dressing are combined with other parameters from the COMSOL materials library.

[0221] Table 2. The initial values used in finite elements analysis (FEA) for thermoelectric stimulation.

[0222] Materials / Modules Parameters Values

[0223] Electrical conductivity (S / m) 5.998E7

[0224] Thermal conductivity (W / rrHK1) 400

[0225] Cu electrodes

[0226] Heat capacity (J / (kg-1K1) 385

[0227] (selected from Material

[0228] Thermal expansion coefficient (1 / K) 17E-6

[0229] Library in COMSOL 6.0)

[0230] Young’s modulus (Pa) / Poisson’s ratio 110E9 / 0.35

[0231] Temperature coefficient of resistivity (1 / K) 0.0039

[0232] Seebeck coefficient (V / K) |220E-5| (Measured)

[0233] Electrical conductivity (S / m) 0.90 (Measured)

[0234] TGCs dressing Thermal conductivity (W / m'1K'1) 25E-2 (Measured)

[0235] Width (m) 3E-2 (Measured)

[0236] Height (m) 5E-3 (Measured)

[0237] Electrical conductivity (S / m) 0.585

[0238] Muscle / Wound tissue

[0239] Thermal conductivity (W / m'1K'1) 0.49 (selected from Material Heat capacity (J / (kg-1K'1) 3421

[0240] Library in COMSOL 6.0) _

[0241] Density (kg / m3) 1090

[0242] Relative permittivity 1

[0243] Temperature of muscle tissue (K) 310

[0244] Thot of wound tissue for power generation

[0245] Variable 310 to 320

[0246] (K)

[0247] Initial value of temperature Temperature of wound tissue for

[0248] 315 thermoelectric cooling (K)

[0249] Applied Input for thermoelectric cooling (A) Variable 0 to 4

[0250] Tambient (K) 298

[0251] The convection exchange coefficient

[0252] 5 h (W m-2K-1)

[0253] Thermopower tests

[0254] The thermopower (Seebeck coefficient, Se) of the TGC dressing was measured using a custom-built and programmable temperature gradient platform (Fig. 10). Two thermocouples were integrated into the surface of the platform to monitor the real-time temperature at the hot and cold sides. A customized graphical user interface was designed to regulate the temperature between the hot and cold stages, and an external deionized water circulating cooling system was connected to meet the measurement requirements under long-term temperature differentials. Open circuit voltage was collected using the electrochemical workstation (CHI 660E, CH Instruments). A platinum wire of 0.3 mm in diameter was used as the electrode. The thermopower is defined based on the equation (Lei, Z., Gao, W. & Wu, P.,

[0255] Joule 2021 , 5, 2211-2222):

[0256] „ Vh~ Vc „ d2e Th- Tcd1Conductivity tests

[0257] The ionic conductivity oeff of TGC dressing was derived from the slope of the voltage-current curve with varying temperature differences (Chen, J. et a!., Nano Energy 2021 , 88, 106272; and Zhu, Y. et a!., ACSAppl. Mater. Interfaces 2024, 16, 32466-32480). Results and discussion

[0258] A thermopower of 1.7-3.6 mV / K (Figs. 11b-e) was achieved with different concentrations of redox couples (Fe2+ / Fe3+-NaAlg) in TGC dressing, which is several times higher than the liquid electrolytes of Fe2+ / Fe3+system (Kim, K., Hwang, S. & Lee, H., Electrochi mica Acta 2020, 335, 135651) (Fig. 12a). The enhanced thermopower is owing to the effective regulation of the interactions between the redox ions and solvents in organic electrolytes. Furthermore, the introduction of extra electrolytes (e.g., Na+, K+) enhanced the transportation of redox ions within the hydrogel backbone network, resulting in an effective ionic conductivity of the TGC dressing reaching 1.84 S r1at room temperature (Figs. 11f and 12b), which is significantly higher than most Fe2+ / Fe3+and [Fe(CN)647Fe(CN)e3'] redox couples. The TGC dressing exhibited a linear relationship of voltage-current density and an expected parabolic curve of voltage-power density, respectively. As shown in Fig. 13, the open circuit voltage and maximum power density is of 18.8 mV and 3.82 mW rm2with the AT of 10 K. As shown in Fig. 13, the normalized Pmax / (AT)2of the TGC dressing is competitive with most of the current thermogalvanic cells. The power output density of the TGC dressing was tested at different temperatures, as shown in Figs. 12d-e. The potential generation mechanism of TGC dressings is similar to that of aqueous solutions, where charge transfer occurs by the migration of ions in the electrolyte in response to temperature difference, rather than solely through the transport of electrons or holes in the inorganic thermoelectric. This process can be represented as a reversible reaction of Fe2+-en>Fe3+. The TGC dressing exhibits sensitive temperature differential response characteristics over the entire temperature range (Fig. 14a).

[0259] Next, programmable, controllable ceramic heating pads were used to simulate the red-hot stage of inflammation (< 41 °C) in wound healing (Figs. 12f and 14b). We then tested the potential of the TGC dressing under various small temperature differences, which was approximately 6-36 mV (Fig. 12f) . The electric field distribution on the surface of skin wounds through the TGC dressing may be revealed using three-dimensional finite element analysis. Fig. 12g shows the temperature (i), potential (ii), and electric field distribution (iii) of the TGC / skin wound model (Fig. 15). When the AT around the wound was 5 K, the potential of the TGC dressing was approximately 48 mV. We also observed that the TGC dressing could produce a cooling temperature difference of roughly 2-4 K when externally powered at ~1 A (Fig. 16). The efficiency of active cooling is limited by the low conductivity of the redox couple (electron) transport, which makes current TGC dressing with an external power output more suitable for dry wounds. In addition, the formation of temperature difference around the wound directly generates a spontaneous exogenous electric field directed toward the wound, which facilitates the formation of electric stimulation and accelerates wound healing.

[0260] Then, we demonstrated that TGC dressing generated exogenous electric fields at the location of the wounds. We established a rat wound defect and measured the potential difference between the wound center and the epidermis at the wound edge (Figs. 12h and 17). The original potential difference between the wound center and the epidermis was -73 mV (Fig. 12i), which increased to -126 mV after being covered with the dressing (Fig. 12j) , suggesting that the dressing increased the potential difference by -53 mV. In the test, the top end of the test electrode was insulated to isolate the TGC dressing. The above experimental results proved that TGC dressing generates an exogenous electric field in the wound in situ and couples with an endogenous electric field, thereby enhancing the wound potential difference (Fig. 1 b).

[0261] Example 5. Antibacterial properties and cytocompatibility

[0262] The management of exudate by TGC dressing is also reflected in the fact that it can inactivate the bacteria in wound exudate in time. Cytotoxicity and cell migration studies were carried out by following the protocols in Example 3.

[0263] Antibacterial experiment

[0264] S. aureus (ATCC 29213) and P. Aeruginosa (ATCC 27853) were used to evaluate antibacterial efficiency. The alginate dressing was set as the control group. Before testing, bacteria were incubated in Luria-Bertani (LB, Sangon Biotech, Shanghai, China) medium for 12 h at 37 °C and diluted to 2-3 x 10® CFU count / mL with 0.1 M PBS (pH = 7.0). All samples were cut into 1 x 1 cm2, wetted sufficiently with PBS, and added with 500 pl of diluted bacteria suspension. After 30 minutes of incubation at 37 °C, the samples were taken into 1 mL of PBS. 15 minutes of sonication (130 W / 50 Hz) was applied to detach the bacteria. Agar plated count, and Live / Dead assay (LIVE / DEAD™ BacLight™ L7012, Thermo Fisher) was used to determine detached bacteria's concentration and viability.

[0265] STZ-induced full-thickness defect model

[0266] This part of the animal experiments was conducted under the animal welfare requirements of ISO 10993-2:2006 and approved by the Laboratory Animal Welfare and Ethics Committee of Shanghai Laboratory Animal Research Centre (Approval number: 210713056). Eight-week- old male SD rats (250 ± 30 g) were fasted for 12 h and injected intraperitoneally with streptozotocin (STZ, 65 mg / kg). One week after the injection, random blood glucose >11.1 mmol / L indicated successful diabetic melding. 24 STZ-induced SD rats were anesthetized, shaved backs, wiped clean, and disinfected with iodophor. Under anesthesia, three excisional wounds were inflicted on the dorsum of each rat with a 10 mm biopsy puncture needle. The wounds were rotationally covered with cotton gauze, alginate, or TGC dressing. A single layer of cotton gauze bandage was applied to fix the dressing.

[0267] Histology and immunofluorescence

[0268] 8 animals were randomly selected for anesthesia on day 3, day 7, and day 14. Wounds were photographed and harvested. For histologic analysis, the tissue was fixed in 4% paraformaldehyde, dehydrated, and embedded by paraffin. 4 pm sections were stained with Masson’s trichrome (Invitrogen, A16520-14). Primary antibodies used for immunofluorescence staining were rabbit monoclonal anti-CD31 antibody (1:100, Abeam ab28364) and mouse monoclonal anti-a-SMA antibody (1 :100, Abeam ab7817). Secondary antibodies were goat anti-rabbit IgG H&L (1:250, Abeam, ab150083) and goat-anti-mouse IgG H&L (1 :250, Abeam, ab150113); Nuclear counterstain was 4',6-diamidino-2-phenylindole (DAPI) (Abeam, ab285390).

[0269] RNA extraction, library construction, and sequencing

[0270] This part of the animal experiments was conducted under the animal welfare requirements of ISO 10993-2:2006 and approved by the Laboratory Animal Welfare and Ethics Committee of Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine (Approval number: SH9H-2020-A227-1). 3 SD rats (8 weeks, 250±30 g) were anesthetized, and three excisional wounds were inflicted on the dorsum of each rat with an 8 mm biopsy puncture needle. The wounds were rotationally covered with cotton gauze, alginate, or TGC dressing. A single layer of cotton gauze bandage was applied to fix the dressings. On day 3, animals were sacrificed with overdosed anesthesia, and the wounds were harvested using an 8 mm biopsy puncture needle. Total RNA was extracted using the Trizol kit (Invitrogen, Carlsbad, CA, USA) according to the protocol provided by the manufacturer. RNA quality was assessed on an Agilent 2100 Bioanalyzer (Agilent Technologies, Palo Alto, CA, USA) and detected using RNase-free agarose gel electrophoresis. After total RNA extraction, eukaryotic mRNA was enriched with Oligo(dT) beads. The enriched mRNA was then fragmented into short fragments using fragmentation buffer and reverse transcribed into cDNA using NEBNext Ultra RNA Library Prep Kit for Illumina (NEB #7530, New England Biolabs, Ipswich, MA, USA). Ligation reactions were purified with AMPure XP Beads (1.0X) and amplified by polymerase chain reaction (PCR). Gene Denovo Biotechnology Co. (Guangzhou, China) sequenced the resulting cDNA libraries using Illumina Novaseq6000. Bacterial infected full-thickness defect model

[0271] This part of the animal experiments was conducted under the animal welfare requirements of ISO 10993-2:2006 and approved by the Laboratory Animal Welfare and Ethics Committee of Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine (Approval number: SH9H-2020-A227-1). A female Large-White (Yorkshire) pig (25 kg) was anesthetized, and the back hair was shaved using hair removal cream. Nine full-thickness defected wounds (d = 40 mm) were prepared using a surgical blade at 5 cm on either side of the midline of the back with a 4 cm spacing between wounds. 200 pL of S. aureus bacterial solution (108CFU / ml, PBS dispersion) was loaded on the surface of each wound. Three kinds of dressings were applied at randomized locations, covered with surgical 3M breathable film, and secured with an elastic band. The wounds were observed and measured at 1 , 3, 7, 14, and 21 days postoperatively. On days 1 , 3, and 7, the dressings were changed. Meanwhile, the wounds were gently cleaned with cotton swaps, emersed in PBS solution, and sonicated for agar plate count. On day 21 , the animal was sacrificed with an overdose of anesthesia, and the wound tissue was harvested for histological evaluation.

[0272] Results and discussion

[0273] After a 30 minutes static contact with bacterial suspension at 37 °C (Fig. 18), TGC dressing showed a bactericidal effect of >99.999% to P.earuginosa and >99.9% to S.aureus (Figs. 19a- c and 20), both are common pathogens in diabetic wound infections. Fe2+can accelerate *OH mainly via the Fenton reaction. The accumulated free radicals damage bacteria structure by the lipid peroxidation of the cell membrane and DNA modifications, leading to cell death. The high concentration of Fe ions in TGC dressing rapidly inactivated bacteria through the above mechanism. Meanwhile, since Fe ions were hard to dissociate from the dressing into the wound environment, the TGC dressing exhibited cytocompatibility. According to the CCK-8 test and live / dead staining (Fig. 21), the viability of fibroblast L929 cultured in the extract of TGC dressing was comparable to the control groups. We further investigated the cytoskeleton (by F-actin staining) and the expression of Col-I. From day 1 to day 5, cells maintained shuttle shape and Col-I expression (Figs. 19d and 22), suggesting the potential to form a dermis. Also, we verified the positive effects of the electric field generated by TGC dressing on the migration of fibroblasts (L929) and endothelial cells (HUVECS) by scratch experiments. The temperature gradient (room temperature and a 37 °C heating stage) was applied to the top and bottom sides of the dressing. TGC dressing achieved a stable direct current of around 50 mV (Fig. 23). At each time point, the electric field was applied to each side of the scratched gap of the cells for 30 minutes (Fig. 24). The scratch closure rate of fibroblasts increased from 28.18% to 40.69% within 24 hours, whereas the scratch closure rate of HUVECS cells increased from 25.70% to 42.24% within 6 hours (Fig. 25). After applying the above electric field for 30 minutes, the wound closure rate of fibroblasts within 24 h increased from 32.42% to 62.85% and 67.94%, and from 63.69% to 70.71% and 77.50% for HUVECS cells.

[0274] STZ-induced wound model

[0275] To validate the wound healing effect of TGC dressing in biological systems, we used a streptozotocin (STZ)-induced diabetic full-thickness wound model, which is commonly used to resemble type I diabetes wound. Three full-thickness wounds (d = 10 mm) were created on the back of the SD rat and covered with cotton gauze (control), NaAIg dressing, or TGC dressing (Figs. 19e and 26). At specific time intervals, the images and infrared thermal images of the wound are shown in Figs. 27 and 28. According to the apparent area of the wound, NaAIg and TGC dressing significantly improved the wound closure rate compared with the control group (P < 0.05). On day 14, the healing rates of wounds in the three groups were 66.0 ± 9.9%, 87.4 ± 2.3%, and 93.4 ± 0.8%, respectively (Fig. 29h). During wound recovery, the infrared photographs demonstrate that the wound bed was colder than the surrounding normal tissue (Fig. 27). At different stages of wound recovery, the infrared photographs demonstrate that the wound bed was continuously colder than the surrounding normal tissue. The temperature gap often suggests impaired subcutaneous vascular tissue and insufficient blood supply to the wound area. Clinically, ischemia caused by impaired circulation in the extremity is also the leading cause of wound ulceration in the diabetic foot, which manifests as hypothermia. On day 14, the temperature difference between TGC dressing cared wounds disappeared, suggesting a more rapid recovery of blood supply than the control group.

[0276] Histological analysis of STZ-induced wound model

[0277] The proliferative phase is the crucial step in wound repair, which can be observed as neovascularization, granulation tissue formation, and re-epithelialization. On day 3, the aggregation of inflammatory cells and hemorrhage demonstrated the inflammation stage of wounds. In contrast, on day 7, wounds entered the proliferative phase, evidenced by the new epithelial tissue at the wound edges. The TGC dressing group developed complete granulation tissue with uniform collagen deposition (Figs. 29a-g). On day 14, the wounds in the NaAIg and TGC groups entered the mature stage. Hyperproliferative epidermis (HPE) covered the entire wound surface, and part of the HPE further differentiated into stratum corneum cells and epithelial cells, leading to the decrease of measured HPE length and 100% proportion of re- epithelialization (Figs. 19f and 29h-j). Moreover, the results of immunofluorescence staining of CD31 and a-SMA were consistent with the trend of Masson’s staining, and the TGC group had a higher density of neovascular in the early stage of wound recovery on day 3 and day 7 (Figs. 19g, 30a and 30d). The oxygen and nutrients brought by the blood facilitated the development of granulation tissue. Afterward, the new blood vessels mature further to form a complete vessel wall marked by a-SMA (Figs. 30b and 30e). On days 3 and 7 , the TGC dressing group upgraded the expression of Egf due to increased HPE length and epithelialization, as observed in Masson's staining. At the same time, the expressions of Tgfbl and Vegfa were higher in the two dressing groups than in the control group, indicating inhibition of inflammation and promotion of vascularization.

[0278] Transcriptomic analysis of SD rat wounds

[0279] To further study the effect of electrical stimulation on early wound healing, we established a rat dorsal wound (8 mm). On day 3, the tissue around the wound was taken for RNA-seq analysis. There is a significant difference between the principal components of the three sample groups. The NaAIg group showed no significantly up-regulated genes compared to the control group. In contrast, the TGC group showed 198 up-regulated genes compared to the control group and 10 up-regulated genes compared to the NaAIg group. Further analysis of the information of these genes revealed that the top 20 up-regulated pathways were dominated by inflammation and epithelialization (i.e. EGF, EGFR and PLCG1) in TGC dressing compared to the control group (Fig. 19h), and the top 20 up-regulated signaling pathways were dominated by cytoskeletal alteration, collagen fiber and muscle tissue formation compared to NaAIg group (Fig. 19i), suggesting that TGC dressing accelerated the wound to the remodeling phase based on the promotion of epithelialization.

[0280] TGC dressing for large infected wound healing

[0281] Based on the positive results of the SD rat model, we further validated the clinical applicability of TGC dressing on large bacterial-infected wounds. A porcine full-thickness skin-defected model (d = 40 mm) was made, and each wound was loaded with 1-2 107CFU of S.aureus (Figs. 19j and 31). The TGC dressing showed a significant pro-healing effect compared to NaAIg dressing and gauze (control group). The difference in open wound area increased progressively during the treatment until the healing rate slowed down in the TGC group after day 14. On day 14, the unclosed wound area rate in the TGC group was 18.9 ± 1.3%, which was 39.5 ± 8.4% in the control group. The wound healing rate was improved by about 20.6%. Then the wound healing rate on day 21 reached 96.0 ± 2.0% (Figs. 191-m), and the epithelial layer of the wound in the TGC dressing group was completely closed, with dense collagen deposition and new blood vessels. In contrast, scabs and bleeding remained on the wound surface in both control groups (Fig. 19k). TGC dressing also showed a rapid and effective bactericidal effect owing to Fe ions, and the bacterial count on the wound surface was 2-3 orders of magnitude lower than that of the NaAIg group and control group during the critical period of wound inflammatory phase (day 1-day 3). Until day 7, when the wounds were scarred, the TGC dressing was discontinued, and the bacterial counts were comparable for all three groups (Fig. 19n).

[0282] Example 6. TGC dressing-based wearable system for wound monitoring and analysis

[0283] In clinical wound care, the inflammatory status of wounds is mainly judged by professional medical staff based on wound temperature and exudate amount. The inflammation response often triggers a temperature increase of 3.5 °C compared to normal skin tissue with increased exudate (Figs. 32a-c) (Armstrong, D. G. et al., Am. J. Med. 2007, 120, 1042-1046). Also, chronic wounds often involve ischemia (low temperature) and neurogenic healing disorders (no temperature change). In the present disclosure, the TGC dressing was equipped with a wearable system (Fig. 33a) to provide long-term monitoring of wound information for diagnosis of acute, chronic, and recurrent infected wounds (Figs. 32d-f).

[0284] Neural network decision-making

[0285] Three fully connected architectures with a rectified linear units (ReLU) activation function and a Softmax layer were chosen for the machine learning applied in this work. In the pre-process, a 5th-order Butterworth low-pass filter was used to remove high-frequency components from the V-t signals, which were considered irrelevant. The signal was transformed into vectors of equal length, i.e., 1000*1. The target values were 0 (acute wound), 1 (chronic wound), 2 (recurrent infection), and 3 (exudate), and the MSELoss function was used to achieve this.

[0286] Results and discussion

[0287] The wearable system consisted of a carefully designed PCB integrated with the Bluetooth Low Energy (BLE) module, analogy-to-digital converter (ADC), signal amplifier, and power management (Figs. 33b-c, internal resistance of voltage and current mode is 20 kQ and 10 kQ, respectively). We collected voltage data in real-time on the response of TGC dressing at contact time and temperature using the portable monitoring module, and the results show a sensitive response characteristic with temperature and touch time for the dressing (Figs. 33d(i)-(iii)). In addition, we tested the changes in voltage output of TGC dressing after dropping 300 pL of 0.1 M PBS to simulate wound exudate. The device output voltage decreases sharply after adding PBS, mainly because the absorption of a small amount of PBS instantly increases the impedance of the TGC dressing, which impedes ion conduction (Fig. 34).

[0288] To further analyze the temperature and wound exudate changes, we selectively monitored the real-time electrical signals (U and I) and time information of the TGC dressing. The wound analysis system was designed with signal acquisition, feature extraction, and neural network decision-making (Fig. 33e) to reveal different wound stages (acute, chronic, recurrent infection, and ulcer). We can achieve good performance by training with a simple network (Fig. 33f), and the external generalization could be further improved in the future with more collected clinical data. We further developed and designed a wound monitoring interface graphic interface of wound monitoring (Fig. 35).

[0289] Based on the results of thermoelectric performance, mechanical properties and biocompatibility (Fig. 33g), we carried the TGC dressing to the wireless monitor in a bacterial- infected white porcine wound model (Figs. 33h and 36). The physical photos of the infected wound (Fig. 33i) revealed fluctuating temperature differences during wound healing. We analyzed the voltage output data and wound temperature obtained on days 0, 1 , 3, and 7 (Fig. 33i). We found that the output voltages were consistently above 25 mV when the temperature differences ranged from 0-2K on day 0, which then showed a maximum value of near 10 K on day 1 , the peak inflammatory phase (Fig. 33j). Accordingly, the TGC dressing achieved a voltage output of 60-80 mV. As a comparison, the Ca2+crosslinked hydrogel dressing demonstrated no voltage output (Fig. 37). Besides, we observed that the current output of the TGC dressing could reflect the porcine’s calm, easy, moderate, and rapid breathing (Fig. 33k). The characteristic waveforms of the TGC dressing varied periodically, which can be used to calibrate the respiratory rate in different physiological states.

[0290] Conclusion

[0291] A thermogalvanic cell hydrogel dressing (TGC dressing) based on the thermoelectric effect to generate an exogenous electric field, thereby facilitating the spontaneous acceleration of wound healing and enabling monitoring of wound status, has been designed and demonstrated in the present disclosure. The thermoelectric effect was utilized to empower biomaterials in the treatment of chronic wounds and validated the potential functions of monitoring (temperature and exudate), electrical stimulation, and thermoelectric cooling. To achieve this, an alginate-based TGC hydrogel composited with nanofibers was designed. The TGC dressing disclosed herein was based on seaweed-derived alginate with interpenetrated polyurethane nanofibers to achieve biocompatibility and exudate management.

[0292] The TGC dressing achieved improved mechanical properties, exudate management based on water vapor transmission, and antimicrobial effects. Furthermore, the TGC dressing acted as a self-sustaining biomedical engineering system with a sensitive response to temperature differences, allowing the generation of an exogenous electric field using the temperature differential at the wound site. Using the temperature differential, it generated an exogenous electric field at the wound site. This electric field facilitated cell migration and promoted the healing of chronic, acute, and infected large wounds. In addition, an integrated wearable wireless monitoring system for temperature monitoring of wounds, smart analytics, and tracking of respiratory rate was designed and developed. Correlations between wirelessly monitored wound voltage signals and temperature were established and the present invention may find applicability in remote healthcare and bioelectronic medicine.

Claims

Claims1. A thermogalvanic cell material suitable for use in a wound dressing, comprising: a biocompatible hydrophobic polymeric material; and a biocompatible ionically-crosslinked hydrogel material, wherein: the biocompatible polymeric material is provided in the form of a non-woven three-dimensional network formed from nanofibers having a first surface, a second surface and a middle portion therebetween; the biocompatible ionically-crosslinked hydrogel material is located in the middle portion of the three-dimensional network, such that the ionically-crosslinked hydrogel material encapsulates at least part of the nanofibers in the middle portion of the non-woven three-dimensional network; and the ionically-crosslinked hydrogel material is crosslinked by at least two multivalent metal ions that form a redox couple.

2. The thermogalvanic cell material according to Claim 1 , wherein the biocompatible hydrophobic polymeric material is selected from one or more of the group consisting of a polycaprolactone, a polylactic acid, a polyglycolic acid, a poly(p-dioxocyclohexanone), a polytetrafluoroethylene, a polyvinylidene fluoride, a polyester, a polypropylene, and a thermoplastic polyurethane.

3. The thermogalvanic cell material according to Claim 2, wherein the biocompatible hydrophobic polymeric material is a thermoplastic polyurethane.

4. The thermogalvanic cell material according to any one of the preceding claims, wherein the biocompatible ionically-crosslinked hydrogel material is selected from one or more of the group consisting of alginate, a polyvinvyl glycol, a polyacrylic acid, a polyacrylamide, and a polyethylene glycol.

5. The thermogalvanic cell material according to Claim 4, wherein the biocompatible ionically-crosslinked hydrogel material is alginate.

6. The thermogalvanic cell material according to any one of the preceding claims, wherein the multivalent metal ions that form a redox couple are selected from Fe2+ / Fe3+, Cu2+ / Cu3+, and Mn2+ / Mn3+.

7. The thermogalvanic cell material according to Claim 6, wherein the multivalent metal ions that form a redox couple is Fe2+ / Fe3+.

8. The thermogalvanic cell material according to any one of the preceding claims, wherein the thermogalvanic cell material displays one or more of the following properties:(ai) a Young’s modulus of greater than 1 kPa, such as from 10.0 to 10.4 kPa, such as from 10.1 to 10.2 kPa;(aii) an elongation to break of greater than 100%, such as greater than 1 ,000%; and(aiii) an ionic conductivity of up to 3 S nr1, such as up to 2 S nr1, such as about 1.84 S nrr1.

9. The thermogalvanic cell material according to any one of the preceding claims, wherein the thermogalvanic cell material displays a water vapour transmission rate of from 3 to 10 kg / m2«24 h, such as from 6 to 9 kg / m2«24 h, such as from 6.74 to 8.70 kg / m2«24 h.

10. The thermogalvanic cell material according to any one of the preceding claims, wherein a weight to weight ratio of the at least two multivalent metal ions that form a redox couple is from 20:1 to 1 :20 for a first multivalent metal ion to a second multivalent metal ion, such as from 10:1 to 1 :10, such as from 5:1 to 1 :5, such as from 2:1 to 1 :2, such as about 1 :1.

11. The thermogalvanic cell material according to any one of the preceding claims, wherein the biocompatible ionically-crosslinked hydrogel material further comprises a biocompatible monovalent metal ion.

12. The thermogalvanic cell material according to Claim 12, wherein the biocompatible monovalent metal ion is selected from one or more of the group consisting of Li+, and more particularly, Na+, and K+, optionally wherein a weight to weight ratio of the monovalent metal ion to the total weight of the at least two multivalent metal ions is from 1 :3 to 1 :20, such as from 1 :4 to 1 :12, such as about 1 :6.

13. The thermogalvanic cell material according to any one of the preceding claims, wherein the thermogalvanic cell material generates an exogenous electric field when placed on a substrate and where the substrate has a temperature that is different to the ambient environment.

14. The thermogalvanic cell material according to Claim 13, wherein when the temperature difference is about 5 K, then the voltage of the electric field generated by the thermogalvanic cell material is from 10 to 60 mV, such as from 20 to 55 mV, such as from 40 to 50 mV.

15. The thermogalvanic cell material according to any one of the preceding claims, wherein when: the thermogalvanic cell material is placed on substrate, such that the second surface of the biocompatible polymeric material is in contact with the substrate; and an external power source is connected by the attachment of a first electrode to the first surface of the biocompatible polymeric material and a second electrode to the second surface of the biocompatible polymeric material, then a cooling temperature difference of from 1 to 5 K, such as from 2 to 4 K, is achieved between the temperature of the first surface and the second surface of the biocompatible polymeric material when a current of about 1 A is applied by the external power source.

16. The thermogalvanic cell material according to any one of the preceding claims, wherein a weight to weight ratio of the biocompatible hydrophobic polymeric material to the biocompatible ionically-crosslinked hydrogel material is from 1 :1.5 to 1 :4, such as from 1 :2 to 1:3, such as about 1.5:2.

17. A device suitable for use as a wound dressing, the device comprising: a thermogalvanic cell material according to any one of Claims 1 to 16; and a flexible printed circuit board, comprising one or more components, electrically connected to the thermogalvanic cell material.

18. The device according to Claim 17, wherein the one or more components include one or more of: a controlling unit, e.g. a central processing unit or a microcontroller unit; a Bluetooth low energy module; an analogue to digital converter; a signal amplifier; and a power management module.

19. A wound dressing comprising a thermogalvanic cell material according to any one of Claims 1 to 16.

20. The wound dressing according to Claim 19, further comprising a flexible printed circuit board, comprising one or more components, electrically connected to the thermogalvanic cell material.

21. The wound dressing according to Claim 20, wherein the one or more components include one or more of: a controlling unit, e g. a central processing unit or a microcontroller unit; a Bluetooth low energy module; an analogue to digital converter; a signal amplifier; and a power management module.

22. A thermogalvanic cell material according to any one of Claims 1 to 16, a device according to Claim 17 or Claim 18, or a wound dressing according to any one of Claims 19 to 21 , for use in treating a wound.

23. Use of a thermogalvanic cell material according to any one of Claims 1 to 16, a device according to Claim 17 or Claim 18, or a wound dressing according to any one of Claims 19 to 21 , in the manufacture of a medicament for treating a wound.

24. A method of treating a wound on a subject comprising the steps of applying one of: a thermogalvanic cell material according to any one of Claims 1 to 16; a device according to Claim 17 or Claim 18; or a wound dressing according to any one of Claims 19 to 21 , to the wound.

25. A thermogalvanic cell material according to any one of Claims 1 to 16, a device according to Claim 17 or Claim 18, or a wound dressing according to any one of Claims 19 to 21 , for use in medicine.

26. A method of making a thermogalvanic cell material according to any one of Claims 1 to 16, the method comprising the steps of:(a) providing a thermogalvanic cell precursor material, comprising: a biocompatible hydrophobic polymeric material; and a biocompatible ionically-crosslinked hydrogel material, wherein: the biocompatible polymeric material is provided in the form of a non-woven three-dimensional network formed from nanofibers having a first surface, a second surface and a middle portion therebetween; the biocompatible ionically-crosslinked hydrogel material is located in the middle portion of the three-dimensional network, such that the ionically-crosslinkedhydrogel material encapsulates at least part of the nanofibers in the middle portion of the non-woven three-dimensional network; and the ionically-crosslinked hydrogel material is crosslinked by a bivalent metal ion; and(b) immersing the thermogalvanic cell precursor material in a redox couple solution comprising at least two multivalent metal salts, where the at least two multivalent metal ions form a redox couple.

27. The method according to Claim 26, wherein the at least two multivalent metal ions are a first multivalent metal ion and a second multivalent metal ion and a weight to weight ratio of the first multivalent metal ion to the second multivalent metal ion is from 20:1 to 1 :20, such as from 10:1 to 1 :10, such as from 5:1 to 1 :5, such as from 2:1 to 1 :2, such as about 1:1.

28. The method according to Claim 26 or Claim 27, wherein the biocompatible ionically- crosslinked hydrogel material further comprises a biocompatible monovalent metal ion.

29. The method according to Claim 28, wherein the biocompatible monovalent metal ion is selected from one or more of the group consisting of Li+, and more particularly Na+, and K+, optionally wherein a weight to weight ratio of the monovalent metal ion to the total weight of the at least two multivalent metal ions is from 1 :3 to 1:20, such as from 1 :4 to 1:12, such as about 1 :6.

30. The method according to any one of Claims 26 to 29, wherein the thermogalvanic cell precursor material is provided by:(ai) providing a pre-hydrogel composite material, comprising: a biocompatible hydrophobic polymeric material; and a biocompatible pre-hydrogel material, wherein: the biocompatible polymeric material is provided in the form of a non-woven three-dimensional network formed from nanofibers having a first surface, a second surface and a middle portion therebetween; the biocompatible pre-hydrogel material is located in the middle portion of the three-dimensional network, such that the pre-hydrogel material coats a surface of at least part of the nanofibers in the middle portion of the non-woven three-dimensional network; and(b) the pre-hydrogel composite material is immersed in a coagulation bath to generate the thermogalvanic cell precursor material.

31. The method according to Claim 30, wherein the pre-hydrogel composite material is prepared by:(bi) providing a solution comprising an organic solvent and the biocompatible polymeric material and subjecting it to an electrospinning for a first period of time onto a collector plate to generate the first surface formed of nanofibers of the biocompatible polymeric material;(bii) subsequently combining the electrospinning with a simultaneous spraying of the biocompatible pre-hydrogel material onto the collector for a second period of time, so as to provide nanofibers of the biocompatible polymeric material coated with the pre-hydrogel material; and(biii) subsequently continuing the electrospinning for a third period of time onto a collector plate to generate the second surface formed of nanofibers of the biocompatible polymeric material.

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