Harnessing Redox Polymer Dynamics for Enhanced Glucose-Oxygen Coupling in Dual Biosensing and Therapeutic Applications.

The burgeoning field of continuous glucose monitoring (CGM) for diabetes management faces significant challenges, particularly in achieving precise and stable biosensor performance under changing environmental conditions such as varying glucose concentrations and O2 levels. To address this, we present a novel biosensor based on the electroless coupling of glucose oxidation catalyzed by flavin-dependent glucose dehydrogenase (FAD-GDH) and O2 reduction catalyzed by bilirubin oxidase (BOD) via a redox polymer, dimethylferrocene-modified linear poly(ethylenimine), FcMe2-LPEI. Initial cyclic voltammetry tests confirm the colocalization of both enzymatic reactions within the potential range of the polymer, indicating an effective electron shuttle mechanism. As a result, we created a hybrid biosensor that operates at open-circuit potential (OCP). It can detect glucose concentrations of up to 100 mM under various O2 conditions, including ambient air. This resulted from optimizing the enzyme ratio to 120 ± 10 mUBOD·UFAD-GDH-1·atmO2-1. This biosensor is highly sensitive, a crucial feature for CGM applications. This distinguishes it from FAD-GDH traditional biosensors, which require a potential to be applied to measure glucose concentrations up to 30 mM. In addition, this biosensor demonstrates the ability to function as a noninvasive, external device that can adapt to changing glucose levels, paving the way for its use in diabetes care and, potentially, personalized healthcare devices. Furthermore, by leveraging the altered metabolic pathways in tumor cells, this system architecture opened up new avenues for targeted glucose scavenging and O2 reduction in cancer therapy.

Advances in electrochemical cofactor regeneration: enzymatic and non-enzymatic approaches.

Nicotinamide adenine dinucleotide(NAD(P)H) is a metabolically interconnected redox cofactor serving as a hydride source for the majority of oxidoreductases, and consequently constituting a significant cost factor for bioprocessing. Much research has been devoted to the development of efficient, affordable, and sustainable methods for the regeneration of these cofactors through chemical, electrochemical, and photochemical approaches. However, the enzymatic approach using formate dehydrogenase is still the most abundantly employed in industrial applications, even though it suffers from system complexity and product purity issues. In this review, we summarize non-enzymatic and enzymatic electrochemical approaches for cofactor regeneration, then discuss recent developments to solve major issues. Issues discussed include Rh-catalyst mediated enzyme mutual inactivation, electron-transfer rates, catalyst sustainability, product selectivity and simplifying product purification. Recently reported remedies are discussed, such as heterogeneous metal catalysts generating H+ as the sole byproduct or high activity and stability redox-polymer immobilized enzymatic systems for sustainable organic synthesis.