A self-powered amperometric lactate biosensor based on lactate oxidase immobilized in dimethylferrocene-modified LPEI

Lactate is an important biomarker due to its excessive production by the body during anerobic metabolism. Existing methods for electrochemical lactate detection require the use of an external power source to supply a positive potential to the working electrode of a given device. Herein we describe a self-powered amperometric lactate biosensor that utilizes a dimethylferrocene-modified linear poly(ethylenimine) (FcMe2-LPEI) hydrogel to simultaneously immobilize and mediate electron transfer from lactate oxidase (LOx) at the anode and a previously described enzymatic cathode. Operating as a half-cell, the FcMe2-LPEI electrode material generates a jmax of 1.51±0.13 mA cm−2 with a KM of 1.6±0.1 mM and a sensitivity of 400±20 μA cm−2 mM−1 while operating with an applied potential of 0.3 V vs. SCE. When coupled with an enzymatic biocathode, the self-powered biosensor has a detection range between 0 mM and 5 mM lactate with a sensitivity of 45±6 μA cm−2 mM−1. Additionally, the FcMe2-LPEI/LOx-based self-powered sensor is capable of generating a power density of 122±5 μW cm−2 with a current density of 657±17 μA cm−2 and an open circuit potential of 0.57±0.01 V, which is sufficient to act as a supplemental power source for additional small electronic devices.