Supporting Cells in Biohybrid Bioelectronics—3D Printed Conducting Scaffolds with Soft Tissue-Like Stiffness

Bio-hybrid devices combine living cells with technology through functional materials with electronic, magnetic or optical properties. Electronically conducting materials, for example, can help stimulate or monitor on-board cellular activity. This growing field has a wide set of applications including tissue regeneration, soft robotics, biosensors, and implantable therapies. Such bio-hybrid devices require that cells be supported near functional materials and require maintenance of their viability and desired behaviors. Challenges arise, however, in designing conducting materials for supporting populations of cells long-term while maintaining technological function in wet, physiological conditions. In this work, we took inspiration from the field of tissue engineering to apply scaffold design principles to electronically conducting materials. Scaffold fabrication was pursued with 3D printing as it is a leading technique for finely controlling microstructure and manipulating cell-material interactions. Here, we present methods of 3D printing poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) hydrogel scaffolds and provide techniques to achieve stiffness relevant to many soft tissues (<100 kPa). We demonstrate that these the bioelectronic scaffolds simultaneously achieve biostable electronic function suitable for device integration, while still supporting native cellular processes through its soft, tissue-matching mechanical environment and microporosity. When electronically connected to instrumentation, we show these scaffolds can serve microporous scaffold electrodes, opening avenues for cellular monitoring. With these findings, we contribute a customizable 3D platform that provides favorable soft cellular microenvironments and envision it to be adaptable to several bioelectronic applications.