Since the first discovery of the connection between high cholesterol levels in human serum and various diseases, such as heart disease and arteriosclerosis, there has been a need to develop a fast, accurate method to measure its level.

Now, a team at Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, has developed a fast response cholesterol sensor based on an amperometric enzymatic technique, using a layer of palladium electrodeposited on a glassy carbon electrode (S. Dong. Q. Deng and G. Cheng, Anal. Chim. Acta, 1993, 279, (2), 235–240).

The dispersed palladium particles electro-catalysed the oxidation of hydrogen peroxide giving a large decrease in overvoltage. Cholesterol oxidase was immobilised on the electrode by cross-linking with glutaraldehyde. A layer of poly(o-phenylenediamine) film was electropolymerised on the enzyme layer thus preventing interference from uric acid and ascorbic acid and increasing the thermal stability of the sensor. The sensor had a response of less than 20 seconds in a concentration range 0.05–4.5 mmol/1. The sensor can be used for 200 assays without any decrease in activity.