Lactic Acid Biosensor Based on Lactate Dehydrogenase Immobilized on Au Nanoparticle Modified Microwire Electrode

Lactate, a key metabolite of the anerobic metabolic pathway serves as a biomarker for lactic acidosis in clinical diagnostics. A variety of electrochemical biosensors have been exploited for the determination of lactate. Here we describe an improved electrochemical lactic acid biosensor that utilizes self-assembled monolayers (SAMs) of cysteamine-modified gold nanoparticles (AuNPs) on flexible tungsten microwire electrode to immobilize lactate dehydrogenase (LDH) to the microwire electrode. The fabricated AuNP-cysteamine-LDH electrode showed excellent behavior towards lactic acid at pH 6 and at 35 °C at an applied potential of +0.4 V (vs Ag/AgCl reference electrode). The biosensor exhibited a linear dynamic range of 500 μM to 7 mM with a very high sensitivity of 31.40μA/mM cm
²
. The biosensor demonstrated good selectivity towards lactic acid, wherein a nafion layer was utilized to screen out interfering species. The AuNP-cysteamine-LDH electrode remained stable up to 18 days. The practicalityof the AuNP-cysteamine-LDHelectrodewas assessedby determining lactic acid concentrations in sera and a sensitivity of 73.16μA/mM cm
²
was observed up to 5 mM.