Amperometric cholesterol biosensor based on immobilized cholesterol esterase and cholesterol oxidase on conducting polypyrrole films

Fabrication of an amperometric cholesterol biosensor by co-immobilization of cholesterol esterase (ChEt) and cholesterol oxidase (ChOx) onto conducting polypyrrole (PPY) films using electrochemical entrapment technique is described. Electrochemical polymerization was carried out using a two-electrode cell configuration at 0.8 V. Characterization of resulting amperometric biosensor for the estimation of cholesterol has been experimentally determined in terms of linear response range, optimum pH, applied potential, temperature, and shelf-life. These PPY/ChEt/ChOx electrodes can be used for cholesterol ester estimation from 1 to 8 mM and have shelf-life of about 4 weeks at 4 °C during which about 15 estimations of cholesterol ester could be made. The sensitivity of PPY/ChEt/ChOx electrode has been found to be 0.15 μA/mM and the apparent K_m value for this electrode is 9.8 mM. Conductivity of the polymer films found to be about 3×10⁻³ S/cm.