Highly Sensitive Lactic Acid Biosensors Based on Photoresist Derived Carbon

In this study, a highly sensitive electrochemical capacitive lactic acid enzymatic sensor based on a carbon-microelectromechanical system (C-MEMS) is developed. The sensing platform of the biosensor, which is photoresist-derived carbon (PDC) microelectrode, was synthesized by pyrolysis of photo-patterned photoresist polymer in oxygen-free and high-temperature conditions. The surfaces of the microelectrodes were functionalized by the oxygen-plasma pretreatment technique to form -COOH functional groups. The lactate oxidase enzyme was immobilized on the carboxylic group covered surfaces of the microelectrodes. The sensor demonstrated the detection of lactic acid over a wide dynamic range of 0.1-$5000~\mu \text{M}$ with a low detection limit of $1.45~\mu \text{M}$ (S/N=3). The sensitivity found to be 33.48 mF.cm
^-2
. (Log (M))
^-1
. This mediator-free lactic acid sensor exhibited 80.07% accuracy in the presence of uric and ascorbic acid and only a 2.35% decrease of measured capacitance in 20 days, which implies good selectivity and high stability. The presented results show that the C-MEMS based lactic acid biosensor is a promising contender for the highly demanding point of care health monitoring applications.