New determination of cholesterol using a surface plasmon resonance sensor with an enzymatic reaction

A surface plasmon resonance (SPR) sensor was applied to a simple and speedy measurement of cholesterol. The lower detection limit was 5.6 x 10(-4) mol/l for an ethanol solution of cholesterol. The measurable range for cholesterol almost equaled that of the concentration of cholesterol in serum without any pretreatment of the serum. There were differences between the data obtained by using a gold film and those by using an enzyme film, due to the presence of hydrogen peroxide produced by a reaction between the enzyme and cholesterol. The differences gave a linear plot in the cholesterol-concentration region of 2.0 x 10(-3) to 2.0 x 10(-2) mol/l, and reached a constant value in the region of 4.0 x 10(-2) to 5.0 x 10(-2) mol/l. The 3.0 x 10(-3) mol/l ascorbic acid, which largely interfered with the spectroscopic measurement of cholesterol, did not interfere with this measurement of a 1.0 x 10(-2) mol/l cholesterol/ethanol solution.