Electrochemical enzyme biosensor for carnitine detection based on cathodic stripping voltammetry

Recently, the amount of carnitine in saliva has been considered a biomarker for pancreatic cancer. Traditional analytical instrument such as liquid chromatography and mass-spectroscopy (MS) has been employed for carnitine detection. Only FET based biosensor was reported for carnitine, but the limit of detection was far above the required concentration. Here, we describe a highly sensitive and selective enzyme biosensor that we have developed for carnitine by using an enzyme-modified electrode combined with cathodic stripping voltammetry. The biosensor exhibits high sensitivity because of the preconcentration on the gold electrode of CoA, which was generated by the enzymatic reaction between carnitine and acetyl coenzyme A (acetyl-CoA) with carnitine acetyltransferase. Although both acetyl-CoA and CoA can adsorb on the gold electrode, the potential difference of reductive desorption detects CoA selectively. Under optimized conditions, the biosensor exhibited a linear range from 0.025 to 25 μM with a detection limit (S/N = 3) of 0.025 μM for carnitine determination. Moreover, the recovery experiments determination results show a stable range from 96.6 to 97.2 %. This developed carnitine biosensor has a potential in clinical detection due to the excellent performance.