Micro- and Macro-Sized Mixed Conducting Hydrogels via 2-Photon Printing for Individual Cell Interaction and Stimulation

The mixed transport of electrons and ions in polymeric systems gives rise to numerous applications, ranging from energy storage to bioelectronics¹. Conducting scaffolds composed of conducting polymers can enhance interactions with cells for biosensing and stimulation². Interfacing tailored micro-sized conducting scaffolds with neuronal cells thus allows insights into electrical activity, signal transmission properties, and proliferation³. The conducting material in these scaffolds can be the base material itself or an additive that infers conducting properties to an insulator^4,5.<br/>We employ 2-photon polymerization to generate interpenetrated hydrogel structures with sub-micron resolution. The properties of acrylamide hydrogels can be tuned to maximize compatibility with cells⁶. Conductivity is achieved through <i>in-situ</i> oxidation and implementation of organic conducting polymers, such as polypyrrole and poly(3,4-ethylenedioxythiophene) (PEDOT). Additionally, electrospun conductive fiber templates are implemented into macro-sized hydrogels to infer electrical conductivity.<br/>To validate our material, the formation of the conductive double network is characterized using conductivity measurements, FTIR analysis and SEM.<br/>By tailoring conductive 3D hydrogel scaffolds, we will be able to optimize the way we interface with single cells, cell populations, or tissues. The generation of an interpenetrating network of organic polymers with mixed conductance behaviour within 3D printed hydrogel structures provides a first step towards enhancing interaction with living systems.<br/><br/>¹<i>ACS Omega</i> 7, 37, 32849–32862 (2022); ²<i>Adv. Funct. Mater.</i> 34, 2308613 (2024); ³<i>Adv. Funct. Mater.</i> 30, 1901369 (2010); ⁴<i>Trends Biotechnol</i>., 0167-7799 (2024); ⁵<i>Nano Lett.</i> 21, 8, 3690–3697 (2021); ⁶<i>Nat. Methods</i> 13, 405–414 (2016)