Solid/Liquid/Gas Three-Phase Interface Enzymatic Reaction-Based Lactate Biosensor with Simultaneously High Sensitivity and Wide Linear Range

Electrochemical lactate biosensors with simultaneously high sensitivity and wide linear detection range are desirable for health monitoring. Nevertheless, the low oxygen level in biological fluids compromises oxidase enzymatic kinetics, which consequently results in a narrow linear detection range and/or low sensitivity. In this study, we addressed this issue by fabricating a solid/liquid/gas three-phase enzyme electrode with sufficiently high oxygen levels in the local reaction zone and much enhanced oxidase enzymatic kinetics. The three-phase enzyme electrode was fabricated by successively immobilizing H₂O₂ electrocatalyst and lactate oxidase (LOx) on a superhydrophobic porous carbon substrate. Owing to the much-enhanced oxidase enzymatic kinetics, the linear detection upper limit of the three-phase lactate biosensor was increased up to 40 mM, about 57-fold higher than that of the conventional two-phase system (0.7 mM), while a sensitivity as high as 22.28 μA mM^-1 cm^-2 was maintained. Moreover, a sweat lactate sensing device was fabricated based on the three-phase enzyme electrode and utilized for lactate detection in undiluted sweat during exercise. This three-phase enzyme electrode with both high sensitivity and wide linear range provides a new approach for the development of high-performance lactate sensing systems.