Enzymic analysis of L-lactate dehydrogenase (LDH) with a surface acoustic wave impedance sensor and its application in the determination of LDH activity in human serum

Abstract

A new method is described for the determination of L-lactate dehydrogenase (LDH) using a surface acoustic wave impedance sensor. The assay of this enzyme is based on the change in conductance of the solution caused by enzymic reaction between lactate, NAD⁺ and LDH. A linear relationship between frequency response and enzyme concentration was obtained and the detection limit was 4.8 U ml^–1. The Michaelis constant for lactate and the corresponding maximum initial rate were 0.03 mol l^–1 and 13 kHz min^–1, respectively. Influences such as temperature, pH value and interferents were also investigated. The method was successfully applied in the clinical assay of LDH activity in human serum. The results compared well with the reported values and support the clinical diagnosis.