Amperometric determination of cholesterol in serum using a biosensor of cholesterol oxidase contained within a polypyrrole-hydrogel membrane

A rapid, two-step method for constructing cholesterol biosensors by entrapment of cholesterol oxidase (ChOx) within a composite poly(2-hydroxyethyl methacrylate) (p(HEMA))/polypyrrole (p(pyrrole)) membrane has been developed. Platinum electrode-supported polymer films were prepared by UV polymerization of the hydrogel component containing dissolved enzyme followed immediately by electrochemical polymerization of entrapped pyrrole monomer (Py) within the performed hydrogel network. The optimized cholesterol biosensor exhibited a linear response range from 5 × 10^-4 to 1.5 × 10^-2 M and detection limit of 120 μM toward cholesterol. The response time of the biosensor was 30s. The analytical recovery of cholesterol in serum samples ranged from 97 to 103% with mean coefficients of variation of 3% (within-day analyses) and 3.9% (day-to-day analyses). Up to 60 samples/h can be manually analyzed. The cholesterol biosensor retained 80% of initial activity after 12 months when stored desiccated in the absence of buffer. When applied to the analysis of cholesterol in serum samples of clinical patients, >0.998 correlation was obtained between the biosensor results and those obtained by a standard hospital method using an Abbott V.P. Chemistry Analyzer.