In-situ generation of Co-Fe bimetallic electrocatalysts on lignosulfonate-derived graphene by direct laser writing for wearable glucose biosensors

Abstract

Wearable biosensors are promising tools for real-time analysis and tracking of human physiological dynamics. However, their fabrication often requires additional electrocatalysts deposited on inert electrode materials, which consistently limits large-scale application. In this study, cobalt-iron Prussian blue analogues (Co-Fe PBA)-mediated sodium lignosulfonate (LS) nanohybrids (PBA-LS) were incorporated into carboxylated nitrile butadiene rubber (XNBR) by latex compounding technology to yield a flexible substrate (PLX). Through CO₂ direct laser writing (DLW), PBA-LS was in-situ transformed into Co-Fe transition metal compound-doped laser-induced graphene (TMC@LIG) electrodes on the PLX surface. For non-invasive and real-time sweat glucose detection, a wearable glucose biosensor was fabricated by directly loading glucose oxidase (GOx) on TMC@LIG, followed by simple microfluidic packaging and connection to a portable miniature electrochemical workstation. The resulting enzymatic glucose biosensor exhibited a sensitivity of 31.28 μA mM⁻¹ cm⁻² and a detection limit of 25 μM. To enhance pathological diagnosis and analysis after identifying health issues through the wearable glucose biosensor, this study further developed a non-enzymatic TMC@LIG-based glucose sensor in an alkaline system with higher sensitivity (340.68 μA mM⁻¹ cm⁻²), a lower detection limit (10 μM), and a wide detection range (0.01-8 mM), enabling precise body fluid analysis. The two TMC@LIG-based biosensors facilitate comprehensive glucose health monitoring and analysis on the same platform, which offers new insights into the rapid fabrication and systematic application of glucose biosensors.