The Determination of Lipase Activity by Measuring pH Using ion-Sensitive Field-effect Transistor

Lipases play an important role in the human metabolism and their abnormal function appear to be associated with many pathological conditions including obesity, Alzheimer disease, atherosclerosis, dyslipideamia associated with diabetes, some infections etc. Measurement of lipase activity therefore becomes important for instrumental diagnosis of the mentioned pathologies. In this work, lipase activity was measured using ion-sensitive field-effect transistor (ISFET) enzyme biosensor based on Tween 20 as a substrate. Developed biosensor is based on measurement of pH change induced by reaction of lipase with Tween 20 when potentiometric ISFET was used for determination of pH changed by the analyte. Tween 20 in concentration range from 0 to 4 % was measured for determination of optimal Tween 20 concentration. Limit of detection was set to be 0.02 %and result curve showed Michaelis-Menten dependency with the Michaelis-Menten constant equal to 0.11 %. Concentration curve of lipase in concentration range from 0 - 4 mg/ml was measured with 2 % Tween 20. Limit of detection was calculated to be 0.02 mg/ml with correlation coefficient 0.998 and Michaelis-Menten constant was equal to 0.36 mg/ml. Effect of interferences and matrix was tested with different concentration. Novel ionsensitive field-effect transistor method is undemanding for laboratory equipment, chemicals and easy repeatable and shows good analytical results comparable with other analytical methods.