Hybrid Bioelectronic Interfaces with Supramolecularly Immobilized Redox Mediators for Ultra-Stable and High-Performance Enzyme Electrodes

An effective immobilization strategy for redox mediators and enzymes is essential for enhancing the performance of bioelectronic devices in biosensing and energy conversion. However, challenges such as limited accessibility to the enzyme's active center, low electron transfer rates in rigid systems, and the inherent instability of conventional redox mediator immobilization methods persist. In this study, we introduce a supramolecular immobilization strategy that ensures high stability while maintaining significant molecular flexibility, thereby facilitating efficient and robust electron transfer in redox enzymes. This approach utilizes cationic phenothiazine-based redox mediators with oxoanion functionality integrated onto phosphate-functionalized metal-organic frameworks (MOFs) through electrostatic interactions and coordination bonding. To address the inherent low conductivity of the MOF matrix, we incorporated PEDOT:PSS. The interactions among the sulfonate groups of PEDOT:PSS and the metal sites within the MOF, supported by electrostatic interactions and hydrogen bonding, promote physical cross-linking. This reduces the swelling of PEDOT:PSS and creates an interconnected conductive polymer network, enhancing the catalytic current of flavin adenine dinucleotide-dependent glucose dehydrogenase (FADGDH) by 1400%. Remarkably, the electrode maintained its high performance for over 7 days of continuous operation without notable degradation, setting a new benchmark for enzyme electrode stability using cost-effective, low-redox-potential organic-based redox mediators. The proposed strategy holds significant promise for the future of bioelectronic devices with potential applications extending from continuous health monitoring and self-powered devices to broader fields.