Electrochemical Detection of Triglycerides Using a TEMPO/Lipase-Modified Electrode

Abstract

A phenol-substituted derivative of the representative electrocatalyst 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), designated as 2-PH-TEMPO, was synthesized. Using this compound, a modified electrode was prepared via electrochemical polymerization, enabling the encapsulated immobilization of lipase. This electrode allowed the electrochemical detection of triglycerides (TG) through a single-enzyme reaction. The polymer film formed by the electropolymerization of 2-PH-TEMPO retained the electrooxidative activity of the TEMPO moieties toward alcohols while simultaneously allowing the gentle immobilization of the enzyme lipase. The immobilized lipase catalyzed the hydrolysis of TG to produce glycerol, which was subsequently electrochemically oxidized at the TEMPO sites, resulting in a concentration-dependent increase in current. Cyclic voltammetry measurements revealed a clear increase in anodic current with increasing concentration of tributyrin. The resulting calibration curve exhibited good linearity over a wide concentration range from 0.1 mM to 10 mM, allowing for reliable quantification. The limit of detection and limit of quantification in the low concentration range were calculated to be 29.3 and 98.1 μM, respectively, with a correlation coefficient (R²) of 0.9741. These results demonstrate that the present method enables highly sensitive and accurate detection of TG. Overall, this study shows that the combination of an organocatalyst and enzyme allows for selective and sensitive electrochemical sensing of TG, with potential applications in food analysis, clinical diagnostics, and lipid metabolism research.