Abstract
Neural implants establish information exchange between electronics and tissues of the nervous system. Depending on the therapeutic context, they can be implanted in the brain, spinal cord, or peripheral nerves. Traditionally, implanted probes are made from stiff materials such as metals or silicon because of their favorable conductive and electrochemical properties. From a mechanical perspective, electrodes are very different from the soft and hydrated host tissues. This is implicated as a cause for suboptimal biointegration, especially when long-term implantation is required. Hydrogels have recently gained attention in bioelectronics, owing to their similarity with tissues in terms of mechanical properties, water content, and bioactivity. A number of approaches have been developed to improve their electrical properties and processability to make this class of material suitable for integration in electrode arrays. This chapter covers current development of conductive hydrogels for bioelectronic interfaces, including fabrication methods, common characterization techniques, strategy for patterning, and some examples of their applications.
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References
Ahadian, S., et al. (2014). Hybrid hydrogels containing vertically aligned carbon nanotubes with anisotropic electrical conductivity for muscle myofiber fabrication. Scientific Reports, 4. https://doi.org/10.1038/srep04271.
Ahadian, S., et al. (2016). Hybrid hydrogel-aligned carbon nanotube scaffolds to enhance cardiac differentiation of embryoid bodies. Acta Biomaterialia, 31, 134. https://doi.org/10.1016/j.actbio.2015.11.047.
Ahearne, M., Yang, Y., & Liu, K.-K. (2008). Mechanical characterisation of hydrogels for tissue engineering applications hydrogels for tissue engineering. In Ashammakhi, N., Reis, R., & Chiellini F. (Eds.), Topics in Tissue Engineering, 4, 4–13.
Arcaute, K., Mann, B., & Wicker, R. (2010). Stereolithography of spatially controlled multi-material bioactive poly(ethylene glycol) scaffolds. Acta Biomaterialia, 6, 1047. https://doi.org/10.1016/j.actbio.2009.08.017.
Aregueta-Robles, U. A., et al. (2014). Organic electrode coatings for next-generation neural interfaces. Frontiers in Neuroengineering, 7. https://doi.org/10.3389/fneng.2014.00015.
Balint, R., Cassidy, N. J., & Cartmell, S. H. (2014). Conductive polymers: Towards a smart biomaterial for tissue engineering. Acta Biomaterialia, 10, 2341. https://doi.org/10.1016/j.actbio.2014.02.015.
Bredas, J. L., et al. (1984). The role of mobile organic radicals and ions (solitons, polarons and bipolarons) in the transport properties of doped conjugated polymers. Synthetic Metals, 9, 265–274.
Cogan, S. F. (2008). Neural stimulation and recording electrodes. Annual Review of Biomedical Engineering, 10, 275. https://doi.org/10.1146/annurev.bioeng.10.061807.160518.
Cogan, S. F., et al. (2016a). Tissue damage thresholds during therapeutic electrical stimulation. Journal of Neural Engineering, 13, 021001. https://doi.org/10.1088/1741-2560/13/2/021001.
Cogan, S. F., Garrett, D. J., & Green, R. A. (2016b). Electrochemical principles of safe charge injection. In Neurobionics: The biomedical engineering of neural prostheses. https://doi.org/10.1002/9781118816028.ch3.
Cong, H. P., et al. (2012). Macroscopic multifunctional graphene-based hydrogels and aerogels by a metal ion induced self-assembly process. ACS Nano, 6, 2693. https://doi.org/10.1021/nn300082k.
Darabi, M. A., et al. (2017). Skin-inspired multifunctional autonomic-intrinsic conductive self-healing hydrogels with pressure sensitivity, stretchability, and 3D printability. Advanced Materials, 29. https://doi.org/10.1002/adma.201700533.
Ding, Y., et al. (2017). Preparation of high-performance ionogels with excellent transparency, good mechanical strength, and high conductivity. Advanced Materials, 29. https://doi.org/10.1002/adma.201704253.
Dvir, T., et al. (2011). Nanowired three-dimensional cardiac patches. Nature Nanotechnology, 6, 720. https://doi.org/10.1038/nnano.2011.160.
Elgrishi, N., et al. (2018). A practical Beginner’s guide to cyclic voltammetry. Journal of Chemical Education, 95, 197–206.
Elschner, A., et al. (2011). PEDOT: Principles and applications of an intrinsically conductive polymer. Boca Raton: CRC.
Fan, L., et al. (2017). Polyaniline promotes peripheral nerve regeneration by enhancement of the brain-derived neurotrophic factor and ciliary neurotrophic factor expression and activation of the ERK1/2/MAPK signaling pathway. Molecular Medicine Reports, 16, 7534–7540.
Fedorovich, N. E., et al. (2007). Hydrogels as extracellular matrices for skeletal tissue engineering: State-of-the-art and novel application in organ printing. Tissue Engineering, 13, 1905. https://doi.org/10.1089/ten.2006.0175.
Feig, V. R., et al. (2018). Mechanically tunable conductive interpenetrating network hydrogels that mimic the elastic moduli of biological tissue. Nature Communications, 9, 2740. https://doi.org/10.1038/s41467-018-05222-4.
Goding, J., et al. (2018a). Considerations for hydrogel applications to neural bioelectronics. Journal of Materials Chemistry B, 7, 1625. https://doi.org/10.1039/c8tb02763c.
Goding, J. A., et al. (2018b). Living bioelectronics: Strategies for developing an effective long-term implant with functional neural connections. Advanced Functional Materials, 28. https://doi.org/10.1002/adfm.201702969.
Goding, J., et al. (2017). A living electrode construct for incorporation of cells into bionic devices. MRS Communications, 7, 487. https://doi.org/10.1557/mrc.2017.44.
Guillonneau, G., et al. (2012). Determination of mechanical properties by nanoindentation independently of indentation depth measurement. Journal of Materials Research, 27, 2551. https://doi.org/10.1557/jmr.2012.261.
Guimard, N. K., Gomez, N., & Schmidt, C. E. (2007). Conducting polymers in biomedical engineering. Progress in Polymer Science (Oxford), 32, 876. https://doi.org/10.1016/j.progpolymsci.2007.05.012.
Han, L., et al. (2017). A mussel-inspired conductive, self-adhesive, and self-healable tough hydrogel as cell stimulators and implantable bioelectronics. Small, 13. https://doi.org/10.1002/smll.201601916.
Hassarati, R. T., et al. (2014). Improving Cochlear implant properties through conductive hydrogel coatings. IEEE Transactions on Neural Systems and Rehabilitation Engineering, 22, 411. https://doi.org/10.1109/tnsre.2014.2304559.
Higgins, T. M., et al. (2011). Gellan gum doped polypyrrole neural prosthetic electrode coatings. Soft Matter, 7, 4690. https://doi.org/10.1039/c1sm05063j.
Hinton, T. J., et al. (2015). Three-dimensional printing of complex biological structures by freeform reversible embedding of suspended hydrogels. Science Advances, 1, e1500758. https://doi.org/10.1126/sciadv.1500758.
Hockaday, L. A., et al. (2012). Rapid 3D printing of anatomically accurate and mechanically heterogeneous aortic valve hydrogel scaffolds. Biofabrication, 4, 035005. https://doi.org/10.1088/1758-5082/4/3/035005.
Huang, C. T., et al. (2017). A graphene-polyurethane composite hydrogel as a potential bioink for 3D bioprinting and differentiation of neural stem cells. Journal of Materials Chemistry B, 5, 8854–8864.
Ido, Y., et al. (2012). Conducting polymer microelectrodes anchored to hydrogel films. ACS Macro Letters, 1, 400–403.
Ismail, Y. A., et al. (2011). Sensing characteristics of a conducting polymer/hydrogel hybrid microfiber artificial muscle. Sensors and Actuators B Chemical, 160, 1180–1190.
Jeong, J. W., et al. (2015). Soft materials in neuroengineering for hard problems in neuroscience. Neuron, 86, 175. https://doi.org/10.1016/j.neuron.2014.12.035.
Kim, D. H., Abidian, M., & Martin, D. C. (2004). Conducting polymers grown in hydrogel scaffolds coated on neural prosthetic devices. Journal of Biomedical Materials Research Part A, 71A, 577. https://doi.org/10.1002/jbm.a.30124.
Kim, D. H., et al. (2010). Conducting polymers on hydrogel-coated neural electrode provide sensitive neural recordings in auditory cortex. Acta Biomaterialia, 6, 57. https://doi.org/10.1016/j.actbio.2009.07.034.
Kishi, R., et al. (2014). Mechanically tough double-network hydrogels with high electronic conductivity. Journal of Materials Chemistry C, 2, 736. https://doi.org/10.1039/c3tc31999g.
Lacour, S. P., Courtine, G., & Guck, J. (2016). Materials and technologies for soft implantable neuroprostheses. Nature Reviews Materials, 1. https://doi.org/10.1038/natrevmats.2016.63.
Leach, J., et al. (2010). Bridging the divide between neuroprosthetic design, tissue engineering and neurobiology. Frontiers in Neuroengineering, 2. https://doi.org/10.3389/neuro.16.018.2009.
Leaf, M. A., & Muthukumar, M. (2016). Electrostatic effect on the solution structure and dynamics of PEDOT:PSS. Macromolecules, 49, 4286. https://doi.org/10.1021/acs.macromol.6b00740.
Liang, S., et al. (2018). Paintable and rapidly bondable conductive hydrogels as therapeutic cardiac patches. Advanced Materials, 30. https://doi.org/10.1002/adma.201704235.
Lim, C., et al. (2019). Stretchable conductive nanocomposite based on alginate hydrogel and silver nanowires for wearable electronics. APL Materials, 7. https://doi.org/10.1063/1.5063657.
Liu, S., et al. (2018). Dual ionic cross-linked double network hydrogel with self-healing, conductive, and force sensitive properties. Polymer (Guildf)., 144, 111. https://doi.org/10.1016/j.polymer.2018.01.046.
Liu, Y., et al. (2019). Soft and elastic hydrogel-based microelectronics for localized low-voltage neuromodulation. Nature Biomedical Engineering, 3, 58–68.
Lu, Y., et al. (2016). Flexible neural electrode array based-on porous graphene for cortical microstimulation and sensing. Scientific Reports, 6. https://doi.org/10.1038/srep33526.
Lu, B., et al. (2019). Pure PEDOT: PSS hydrogels. Nature Communications, 10, 1043. https://doi.org/10.1038/s41467-019-09003-5.
Lukachova, L. V., et al. (2003). Electroactivity of chemically synthesized polyaniline in neutral and alkaline aqueous solutions. Journal of Electroanalytical Chemistry, 544, 59. https://doi.org/10.1016/s0022-0728(03)00065-2.
MacDiarmid, A. G., & Epstein, A. J. (1994). The concept of secondary doping as applied to polyaniline. Synthetic Metals, 65, 103. https://doi.org/10.1016/0379-6779(94)90171-6.
Mario Cheong, G. L., et al. (2014). Conductive hydrogels with tailored bioactivity for implantable electrode coatings. Acta Biomaterialia, 10, 1216. https://doi.org/10.1016/j.actbio.2013.12.032.
Mawad, D., Lauto, A., & Wallace, G. G. (2016). Conductive polymer hydrogels. In Kalia, S. (Ed.), Polymeric hydrogels as smart biomaterials. https://doi.org/10.1007/978-3-319-25322-0_2.
Merker, J., et al. (2001). High temperature mechanical properties of the platinum group metals: Elastic properties of platinum, rhodium and iridium and their alloys at high temperatures. Platinum Metals Review, 45, 74.
Merrill, D. R., Bikson, M., & Jefferys, J. G. R. (2005). Electrical stimulation of excitable tissue: Design of efficacious and safe protocols. Journal of Neuroscience Methods, 141, 171. https://doi.org/10.1016/j.jneumeth.2004.10.020.
Minev, I. R., et al. (2015). Electronic dura mater for long-term multimodal neural interfaces. Science (80), 347, 159–163.
Murphy, S. V., Skardal, A., & Atala, A. (2013). Evaluation of hydrogels for bio-printing applications. Journal of Biomedical Materials Research Part A, 101A, 272. https://doi.org/10.1002/jbm.a.34326.
Navaei, A., et al. (2016). Gold nanorod-incorporated gelatin-based conductive hydrogels for engineering cardiac tissue constructs. Acta Biomaterialia, 41, 133. https://doi.org/10.1016/j.actbio.2016.05.027.
Novoselov, K. S., et al. (2012). A roadmap for graphene. Nature, 490, 192–200.
Odent, J., et al. (2017). Highly elastic, transparent, and conductive 3D-printed ionic composite hydrogels. Advanced Functional Materials, 27, 1701807.
Oyen, M. L. (2014). Mechanical characterisation of hydrogel materials. International Materials Review, 59, 44. https://doi.org/10.1179/1743280413y.0000000022.
Pardo-Yissar, V., et al. (2001). Gold nanoparticle/hydrogel composites with solvent-switchable electronic properties. Advanced Materials, 13, 1320–1323.
Park, S. I., et al. (2015). Soft, stretchable, fully implantable miniaturized optoelectronic systems for wireless optogenetics. Nature Biotechnology, 33, 1280–1286.
Pok, S., et al. (2014). Biocompatible carbon nanotube–chitosan scaffold matching the electrical conductivity of the heart. ACS Nano, 8, 9822. https://doi.org/10.1021/nn503693h.
Polikov, V. S., Tresco, P. A., & Reichert, W. M. (2005). Response of brain tissue to chronically implanted neural electrodes. Journal of Neuroscience Methods, 148, 1. https://doi.org/10.1016/j.jneumeth.2005.08.015.
Ramón-Azcón, J., et al. (2013). Dielectrophoretically aligned carbon nanotubes to control electrical and mechanical properties of hydrogels to fabricate contractile muscle myofibers. Advanced Materials, 25, 4028. https://doi.org/10.1002/adma.201301300.
Ray, S. C. (2015). Application and uses of graphene oxide and reduced graphene oxide. In Applications of graphene and graphene-oxide based nanomaterials. https://doi.org/10.1016/b978-0-323-37521-4.00002-9.
Rho, J. Y., Ashman, R. B., & Turner, C. H. (1993). Young’s modulus of trabecular and cortical bone material: Ultrasonic and microtensile measurements. Journal of Biomechanics, 26, 111–119.
Rodger, D. C., et al. (2008). Flexible parylene-based multielectrode array technology for high-density neural stimulation and recording. Sensors and Actuators B Chemical, 132, 449–460.
Rose, T. L., Kelliher, E. M., & Robblee, L. S. (1985). Assessment of capacitor electrodes for intracortical neural stimulation. Journal of Neuroscience Methods, 12, 181. https://doi.org/10.1016/0165-0270(85)90001-9.
Sanchez-Sanchez, A., Del Agua, I., Malliaras, G. G., & Mecerreyes, D. (2019). Conductive poly(3,4-Ethylenedioxythiophene) (PEDOT)-based polymers and their applications in bioelectronics. In Smart Polymers and their Applications. https://doi.org/10.1016/B978-0-08-102416-4.00006-5.
Saravanan, P., Padmanabha Raju, M., & Alam, S. (2007). A study on synthesis and properties of Ag nanoparticles immobilized polyacrylamide hydrogel composites. Materials Chemistry and Physics, 103, 278–282.
Sasaki, M., et al. (2014). Highly conductive stretchable and biocompatible electrode-hydrogel hybrids for advanced tissue engineering. Advanced Healthcare Materials, 3, 1919–1927.
Sekine, S., et al. (2010). Conducting polymer electrodes printed on hydrogel. Journal of the American Chemical Society, 132, 13174. https://doi.org/10.1021/ja1062357.
Shah, K., et al. (2015). Development and characterization of polyethylene glycol-carbon nanotube hydrogel composite. Journal of Materials Chemistry B, 3, 7950. https://doi.org/10.1039/c5tb01047k.
Shi, Y., et al. (2014). Nanostructured conductive polypyrrole hydrogels as high-performance, flexible supercapacitor electrodes. Journal of Materials Chemistry A, 2, 6086–6091.
Shin, S. R., et al. (2013). Carbon-nanotube-embedded hydrogel sheets for engineering cardiac constructs and bioactuators. ACS Nano, 7, 2369. https://doi.org/10.1021/nn305559j.
Shin, S. R., et al. (2015). Aligned carbon nanotube-based flexible gel substrates for engineering biohybrid tissue actuators. Advanced Functional Materials, 25, 4486. https://doi.org/10.1002/adfm.201501379.
Skardal, A., et al. (2010). Dynamically crosslinked gold nanoparticle-hyaluronan hydrogels. Advanced Materials, 22, 4736–4740.
Staples, N. A., et al. (2018). Conductive hydrogel electrodes for delivery of long-term high frequency pulses. Frontiers in Neuroscience, 11. https://doi.org/10.3389/fnins.2017.00748.
Stejskal, J. (2017). Conducting polymer hydrogels. Chemical Papers, 71, 269. https://doi.org/10.1007/s11696-016-0072-9.
Stejskal, J., Kratochvíl, P., & Jenkins, A. D. (1995). Polyaniline: Forms and formation. Collection of Czechoslovak Chemical Communications, 60, 1747. https://doi.org/10.1135/cccc19951747.
Stejskal, J., et al. (2016). Polypyrrole salts and bases: Superior conductivity of nanotubes and their stability towards the loss of conductivity by deprotonation. RSC Advances, 6, 88382. https://doi.org/10.1039/c6ra19461c.
Sydney Gladman, A., et al. (2016). Biomimetic 4D printing. Nature Materials, 15, 413. https://doi.org/10.1038/nmat4544.
Tang, Q., et al. (2008). Polyaniline/polyacrylamide conducting composite hydrogel with a porous structure. Carbohydrate Polymers, 74, 215. https://doi.org/10.1016/j.carbpol.2008.02.008.
Tan, Y., et al. (2014). 3D printing facilitated scaffold-free tissue unit fabrication. Biofabrication, 6, 024111. https://doi.org/10.1088/1758-5082/6/2/024111.
Tasis, D., et al. (2006). Chemistry of carbon nanotubes. Chemical Reviews, 106, 1105–1136.
Thuy Pham, T. P., Cho, C. W., & Yun, Y. S. (2010). Environmental fate and toxicity of ionic liquids: A review. Water Research, 44, 352–372.
Tondera, C., et al. (2019). Highly conductive, stretchable, and cell-adhesive hydrogel by nanoclay doping. Small, 1901406, 1–8.
Vernitskaya, T. V., & Efimov, O. N. (1997). Polypyrrole: a conducting polymer; its synthesis, properties and applications. Russian Chemical Reviews, 66, 443–457.
Wang, K., et al. (2006). Neural stimulation with a carbon nanotube microelectrode array. Nano Letters, 6, 2043. https://doi.org/10.1021/nl061241t.
Wang, S., et al. (2017). Neural stem cell proliferation and differentiation in the conductive PEDOT-HA/Cs/gel scaffold for neural tissue engineering. Biomaterials Science, 5, 2024. https://doi.org/10.1039/c7bm00633k.
Wu, Y., et al. (2016). Fabrication of conductive gelatin methacrylate-polyaniline hydrogels. Acta Biomaterialia, 33, 122. https://doi.org/10.1016/j.actbio.2016.01.036.
Wu, S., et al. (2017). Biocompatible chitin/carbon nanotubes composite hydrogels as neuronal growth substrates. Carbohydrate Polymers, 174, 830–840.
Xiao, X., et al. (2017). Preparation and property evaluation of conductive hydrogel using poly (vinyl alcohol)/polyethylene glycol/graphene oxide for human electrocardiogram acquisition. Polymers (Basel), 9. https://doi.org/10.3390/polym9070259.
Xu, Y., et al. (2010). Self-assembled graphene hydrogel via a one-step hydrothermal process. ACS Nano, 4, 4324. https://doi.org/10.1021/nn101187z.
Xu, Y., et al. (2018). Noncovalently assembled electroconductive hydrogel. ACS Applied Materials & Interfaces, 10, 14418. https://doi.org/10.1021/acsami.8b01029.
Yamato, H., Ohwa, M., & Wernet, W. (1995). Stability of polypyrrole and poly(3,4-ethylenedioxythiophene) for biosensor application. Journal of Electroanalytical Chemistry, 397, 163. https://doi.org/10.1016/0022-0728(95)04156-8.
Yao, B., et al. (2017). Ultrahigh-conductivity polymer hydrogels with arbitrary structures. Advanced Materials, 29. https://doi.org/10.1002/adma.201700974.
Yuan, J., & Antonietti, M. (2011). Poly(ionic liquid)s: Polymers expanding classical property profiles. Polymer, 52, 1469. https://doi.org/10.1016/j.polymer.2011.01.043.
Yue, J., Epstein, A. J., & Macdiarmid, A. G. (1990). Sulfonic acid ring-substituted polyaniline, a self-doped conducting polymer. Molecular Crystals and Liquid Crystals Incorporating Nonlinear Optics, 189, 255. https://doi.org/10.1080/00268949008037237.
Yuk, H., Lu, B., & Zhao, X. (2018). Hydrogel bioelectronics. Chemical Society Reviews, 48, 1642. https://doi.org/10.1039/C8CS00595H.
Zhai, D., et al. (2013). Highly sensitive glucose sensor based on Pt nanoparticle/polyaniline hydrogel heterostructures. ACS Nano, 7, 3540. https://doi.org/10.1021/nn400482d.
Zhao, Y., et al. (2013). 3D nanostructured conductive polymer hydrogels for high-performance electrochemical devices. Energy and Environmental Science, 6, 2856. https://doi.org/10.1039/c3ee40997j.
Zhou, Y., et al. (2018a). Highly stretchable, elastic, and ionic conductive hydrogel for artificial soft electronics. Advanced Functional Materials, 29. https://doi.org/10.1002/adfm.201806220.
Zhou, L., et al. (2018b). Soft conducting polymer hydrogels cross-linked and doped by tannic acid for spinal cord injury repair. ACS Nano, 12, 10957. https://doi.org/10.1021/acsnano.8b04609.
Zhu, F., et al. (2018). Tough and conductive hybrid hydrogels enabling facile patterning. ACS Applied Materials & Interfaces, 10, 13685. https://doi.org/10.1021/acsami.8b01873.
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Akbar, T.F., Tondera, C., Minev, I. (2020). Conductive Hydrogels for Bioelectronic Interfaces. In: Guo, L. (eds) Neural Interface Engineering. Springer, Cham. https://doi.org/10.1007/978-3-030-41854-0_9
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