Background. Most pathologies of the human body (in particular, malignant neoplasms, myocardial hypoxia, liver diseases, etc.) are accompanied by a violation of the integrity of cells in target tissues and the release of intracellular macromolecules into the extracellular environment. Thus, an important diagnostic and prognostic indicator is the level of activity of certain enzymes in blood serum, which are normally intracellular. One of the most promising areas of modern medical electronics and biophysics is the development and optimization of enzyme screening methods in biological fluids. In this study, we aimed to investigate the biophysical characteristics of using a recombination sensor for determining LDH activity in biological fluids. Materials and Methods. Experiments were performed on preparations of standard human blood serum. The reference determination of lactate dehydrogenase activity was carried out photometrically based on the change (decrease) in the concentration of the reduced form of the NADH coenzyme. The passage of the lactate dehydrogenase reaction was experimentally recorded by measuring the photocurrent of a silicon structure with a buried barrier under light irradiation from the region of strong absorption (λ = 532 nm). Results. The biophysical features of the device were studied. The detection of lactate dehydrogenase becomes possible due to the transfer of a hydrogen ion from nicotinamide adenine dinucleotide (NADH) to pyruvate, as a result of which lactate and NAD+ are formed. The effect is explained by the local electrostatic influence on the parameters of the recombination centers in the near-surface bending zone near the silicon surface, which leads to a change in the surface recombination rate. Conclusions. Our approach can be considered as a promising way to develop a highly sensitive method for the detection of lactate dehydrogenase. It has been experimentally shown that effective detection is possible in two changes at the surface bending of the deep barrier silicon substrate zone.
