Looking both ways: Electroactive biomaterials with bidirectional implications for dynamic cell-material crosstalk.

Cells exist in natural, dynamic microenvironmental niches that facilitate biological responses to external physicochemical cues such as mechanical and electrical stimuli. For excitable cells, exogenous electrical cues are of interest due to their ability to stimulate or regulate cellular behavior via cascade signaling involving ion channels, gap junctions, and integrin receptors across the membrane. In recent years, conductive biomaterials have been demonstrated to influence or record these electrosensitive biological processes whereby the primary design criterion is to achieve seamless cell-material integration. As such, currently available bioelectronic materials are predominantly engineered toward achieving high-performing devices while maintaining the ability to recapitulate the local excitable cell/tissue microenvironment. However, such reports rarely address the dynamic signal coupling or exchange that occurs at the biotic-abiotic interface, as well as the distinction between the ionic transport involved in natural biological process and the electronic (or mixed ionic/electronic) conduction commonly responsible for bioelectronic systems. In this review, we highlight current literature reports that offer platforms capable of bidirectional signal exchange at the biotic-abiotic interface with excitable cell types, along with the design criteria for such biomaterials. Furthermore, insights on current materials not yet explored for biointerfacing or bioelectronics that have potential for bidirectional applications are also provided. Finally, we offer perspectives aimed at bringing attention to the coupling of the signals delivered by synthetic material to natural biological conduction mechanisms, areas of improvement regarding characterizing biotic-abiotic crosstalk, as well as the dynamic nature of this exchange, to be taken into consideration for material/device design consideration for next-generation bioelectronic systems.