Electroanalysis of Enzyme Activity in Small Biological Samples: Alkaline Phosphatase.

The discovery of sulfite-stabilized anodic current of hydroquinone (HQ) at high pH was used to develop two new methods for measuring the activity of the key biomarker alkaline phosphatase (ALP). Both approaches relied on the monitoring of ALP-triggered release of HQ from a substrate hydroquinone diphosphate (HQDP) into a pH 10.00 solution.

Determination of sorbitol dehydrogenase in microsamples of human serum.

The enzyme sorbitol dehydrogenase (SDH) is an emerging biomarker of drug-induced liver injury (DILI). This paper introduces determination of SDH in microliter samples of human serum at commercial glucose test strips. The determination relies on the oxidation of NADH cofactor, which is used by SDH reacting with its substrates.

Infection Screening in Biofluids with Glucose Test Strips.

The four glucosyl esters were synthesized and tested for the determination of infection enzyme leukocyte esterase (LE) in human synovial (joint) fluid and urine. The esters acted as LE substrates releasing glucose in a direct proportion to the activity of LE in a sample. The freed glucose was then detected by a coupled-enzyme assay at either a nitrogen-doped carbon nanotube (N-CNT) electrode or a commercial glucose test strip.

Electroanalysis of Infection with Methyl Pyruvate.

The discovery of infection enzyme leukocyte esterase (LE) hydrolyzing a mitochondrial substrate methyl pyruvate (MP) was explored in the development of electroanalytical methods for LE in human biofluids. The LE + MP reaction was coupled with alcohol oxidase to produce hydrogen peroxide, which was then reduced at a nitrogen-doped carbon nanotube electrode at -0.20 V, yielding current proportional to the LE content in a sample.

Electrochemical Assays and Immunoassays of the Myeloperoxidase/SCN/HO System.

Strategies to detect and characterize myeloperoxidase (MPO) are needed, given that this "split personality" enzyme kills harmful microorganisms but also damages a host tissue. Here, we describe electrochemical approaches to measure MPO by using the pseudohalogenation (MPO/SCN/HO) and catalase-like (MPO/HO) cycles. Their kinetics were determined by monitoring the consumption of HO with a nitrogen-doped carbon nanotubes (N-CNT) electrode, which could detect 0.

Determination of omega-3 fatty acids in fish oil supplements using vibrational spectroscopy and chemometric methods.

The potential of Fourier transform infrared (FT-IR), near-infrared (NIR), and Raman spectroscopic techniques combined with partial least squares (PLS) regression (PLSR) to predict concentrations of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and total omega-3 fatty acids (n-3 FAs) in fish oil supplements was investigated. FT-IR spectroscopy predicted EPA (coefficient of determination (R(2)) of 0.994, standard error of cross-validation (SECV) of 2.