Polypyrrole/sulfonated multi-walled carbon nanotubes conductive hydrogel for electrochemical sensing of living cells

Conductive hydrogels, a class of novel polymeric material that combine the electronic conductivity of intrinsically conductive materials and diverse functionalities of hydrogels, are promising candidates for a range of applications in bioelectronics. However, poor conductivity and biocompatibility of conventional conducting hydrogels compromise the reliable function of hydrogel bioelectronic devices. Herein, we report the development of a conjugated polypyrrole (PPy) hydrogel with conductive sulfonated multi-walled carbon nanotubes (s-MWCNTs) as crosslinking agent. The electrostatic interaction between -SO3- groups of s-MWCNTs and nitrogen groups of PPy facilitates the hydrogel gelation, and the conductivity of PPy/s-MWCNTs hydrogel with interconnected 3D conducting network is measured to be 30 S m−1. Furthermore, the in vitro cytocompatibility results suggest that the proposed PPy/s-MWCNTs hydrogels have excellent biocompatibility. For bioelectronics applications, the PPy/s-MWCNTs hydrogels were demonstrated to serve as highly sensitive electrochemical biosensors for in situ detection of biomolecules released from living cells and cell-substrate impedance biosensors for real-time monitoring of cell proliferation. Our strategy for assembling conjugated polymer hydrogel with conductive crosslinker would offer new insight for the construction of highly conductive hydrogels for various potential applications in bioelectronics.