Construction of an Amperometric Lactate Biosensor Based on Immobilization of Lactate Dehydrogenase Nanoparticles onto Pencil Graphite Electrode

Abstract

Nanoparticles (NPs) of commercial lactate dehydrogenase from rabbit muscle were prepared, characterized and immobilized covalently onto pencil graphite (PG) electrode to fabricate an improved amperometric lactate biosensor (LDHNPs/PGE). The biosensor showed an optimum response within 2.5s at pH 7.0, temperature 35°C, at an applied potential of -0.4V. The wide linear response was produced by biosensor with in a concentration range of lactic acid (0.001 μM to 45 mM) and current (mA) under optimal conditions. The LDHNPs/PGE electrode showed high sensitivity (2.45 ± 2.0 μA cm−2 μM−1); a lower detection limit (0.001 μM) and good correlation coefficient (R2 = 0.99) with a standard enzymic colorimetric method. The evaluation study of biosensor offered a good analytical recovery of 98.01%, when lactic acid concentration was added in the sera sample. In addition, within and between batches coefficients of variation for working electrode were detected as 0.03% and 0.04%, respectively. The biosensor was applied for the detection of lactic acid in the serum of apparently healthy subject and patients affected from cardiogenic shocks. There was a 10% loss in initial activity of biosensor after its regular use over a time period of 180 days, while being stored at 4°C.