Direct electrochemistry of lactate dehydrogenase in aqueous solution system containing l(+)-lactic acid, β-nicotinamide adenine dinucleotide, and its reduced form

Detection of lactate in human sweat via surface-modified, screen-printed carbon electrodes

Real-time and continuous monitoring of lactate levels in sweat has been used as an indicator of physiological information to evaluate exercise outcomes and sports performance. We developed an optimal enzyme-based biosensor to detect the concentrations of lactate in different fluids (i.e., a buffer solution and human sweat). The surface of the screen-printed carbon electrode (SPCE) was first treated with oxygen plasma and then surface-modified by lactate dehydrogenase (LDH). The optimal sensing surface of the LDH-modified SPCE was identified by Fourier transform infrared spectroscopy and electron spectroscopy for chemical analysis. After connecting the LDH-modified SPCE to a benchtop E4980A precision LCR meter, our results showed that the measured response was dependent on the lactate concentration. The recorded data exhibited a broad dynamic range of 0.1-100 mM (R² = 0.95) and a limit of detection of 0.1 mM, which was unachievable without the incorporation of redox species. A state-of-the-art electrochemical impedance spectroscopy (EIS) chip was developed to integrate the LDH-modified SPCE for a portable bioelectronic platform in the detection of lactate in human sweat. We believe the optimal sensing surface can improve the sensitivity of lactate sensing in a portable bioelectronic EIS platform for early diagnosis or real-time monitoring during different physical activities.

Current Status and Future Perspectives of Lactate Dehydrogenase Detection and Medical Implications: A Review

The demand for glucose uptake and the accompanying enhanced glycolytic energy metabolism is one of the most important features of cancer cells. Unlike the aerobic metabolic pathway in normal cells, the large amount of pyruvate produced by the dramatic increase of glycolysis in cancer cells needs to be converted to lactate in the cytoplasm, which cannot be done without a large amount of lactate dehydrogenase (LDH). This explains why elevated serum LDH concentrations are usually seen in cancer patient populations. LDH not only correlates with clinical prognostic survival indicators, but also guides subsequent drug therapy. Besides their role in cancers, LDH is also a biomarker for malaria and other diseases. Therefore, it is urgent to develop methods for sensitive and convenient LDH detection. Here, this review systematically summarizes the clinical impact of lactate dehydrogenase detection and principles for LDH detection. The advantages as well as limitations of different detection methods and the future trends for LDH detection were also discussed.

Fluorescence determination of lactate dehydrogenase activity based on silicon quantum dots

Silicon quantum dots (SiQDs) synthesized based on 3-aminopropyltrimethoxysilane (ATPMS) as silicon source were used to detect the activity of lactate dehydrogenase (LDH) through changes of fluorescence intensity of SiQDs. In this system, the fluorescence of SiQDs was first quenched by nicotinamide adenine dinucleotide (NADH), and then recovered with the addition of LDH, as NADH was consumed by catalytic reaction of LDH. A linear calibration chart of LDH is obtained in the range of 0.77-385 U/mL. The assay displays high selectivity towards LDH detection, and was successfully applied to the analysis of LDH in human serum samples. This assay has great prospects for the diagnosis and prognosis of various diseases, especially melanoma.