Establishing preanalytical stability of vitamin A and vitamin E.

Vitamin A and Vitamin E, a group of lipid-soluble vitamins, can be degraded by photolysis and photooxidation after exposure to light. As an essential area of the preanalytical stage, inappropriate storage conditions of patient samples could lead to inaccurate results. In this study, we evaluated three of the most common preanalytical storage conditions (RT, +4°C, and -20 °C) in the workflow in the clinical laboratory setting using both clear and amber Eppendorf tubes.

Development and Validation of an Automated Zone Fluidics-Based Sensor for In Vitro Dissolution Studies of Captopril Using Total Error Concept.

In the present research, a zone fluidics-based automated sensor for the analysis of captopril in in vitro dissolution samples is reported. Captopril is reacted under flow conditions with Ni(II) (10 mmol L) in alkaline medium (0.15% NH) to form a stable derivate, which is monitored spectrophotometrically at 340 nm.

Micelles Mediated Zone Fluidics Method for Hydrazine Determination in Environmental Samples.

An automated flow method for the determination of hydrazine based on the concept of zone-fluidics has been developed. The analyte reacts under flow conditions with -dimethylamino benzaldehyde (25 mmol L) in micellar medium (100 mmol L SDS) to form a stable derivative (460 nm). Micelles mediated catalysis excludes the use of highly acidic environment typical for this kind of reaction.

Multi-omics Biomarker Pipeline Reveals Elevated Levels of Protein-glutamine Gamma-glutamyltransferase 4 in Seminal Plasma of Prostate Cancer Patients.

Seminal plasma, because of its proximity to prostate, is a promising fluid for biomarker discovery and noninvasive diagnostics. In this study, we investigated if seminal plasma proteins could increase diagnostic specificity of detecting primary prostate cancer and discriminate between high- and low-grade cancers. To select 147 most promising biomarker candidates, we combined proteins identified through five independent experimental or data mining approaches: tissue transcriptomics, seminal plasma proteomics, cell line secretomics, tissue specificity, and androgen regulation.

Biochemical characterization of human tissue kallikrein 15 and examination of its potential role in cancer.

Objective: Human tissue kallikrein 15 (KLK15) is the last cloned member of the KLK-related gene family. Despite being implicated in multiple cancers, its pathophysiological role remains unknown. We aimed to biochemically characterize KLK15 and preliminarily study its role in cancer.

Preclinical evaluation of a TEX101 protein ELISA test for the differential diagnosis of male infertility.

Background: TEX101 is a cell membrane protein exclusively expressed by testicular germ cells and shed into seminal plasma. We previously verified human TEX101 as a biomarker for the differential diagnosis of azoospermia, and developed a first-of-its-kind TEX101 ELISA. To demonstrate the clinical utility of TEX101, in this work we aimed at evaluating ELISA performance in a large population of fertile, subfertile, and infertile men.

A new enzyme-linked immunosorbent assay (ELISA) for human free and bound kallikrein 9.

Background: Kallikrein 9 (KLK9) is a member of the human kallikrein-related peptidases family, whose physiological role and implications in disease processes remain unclear. The active form of the enzyme is predicted to have chymotryptic activity. In the present study, we produced for the first time the active recombinant protein and monoclonal antibodies, and developed novel immunoassays for the quantification of free and bound KLK9 in biological samples.

Quantification of Human Kallikrein-Related Peptidases in Biological Fluids by Multiplatform Targeted Mass Spectrometry Assays.

Human kallikrein-related peptidases (KLKs) are a group of 15 secreted serine proteases encoded by the largest contiguous cluster of protease genes in the human genome. KLKs are involved in coordination of numerous physiological functions including regulation of blood pressure, neuronal plasticity, skin desquamation, and semen liquefaction, and thus represent promising diagnostic and therapeutic targets. Until now, quantification of KLKs in biological and clinical samples was accomplished by enzyme-linked immunosorbent assays (ELISA).

Zwitterionic hydrophilic interaction chromatography coupled with post-column derivatization for the analysis of glutathione in wine samples.

In this study the development, validation and application of a new chromatographic method for the determination of glutathione (GSH) in wine samples is presented. The separation of the GSH was carried out using a sulfobetaine-based hydrophilic interaction chromatography (HILIC) analytical column whereas its detection was carried out spectrofluorimetrically (λext/λem=340/455 nm) after post-column derivatization with o-phthalaldehyde. GSH was separated efficiently from matrix endogenous compounds of wines by using a mobile phase of 15 mmol L(-1) CH3COONH4 (pH=2.

Selective fluorimetric method for the determination of histamine in seafood samples based on the concept of zone fluidics.

In the present article we report our results on the development of a selective automated method for the determination of histamine in seafood using the concept of zone fluidics. The method is based on the sequential on-line reaction of the analyte with o-phthalaldehyde in the absence of a nucleophilic reagent, followed by acidification. The careful selection of the chemical and instrumental variables enabled the determination of the analyte with adequate sensitivity at the low micromolar level and with specificity against other biogenic amines and amino acids such as histidine.

Determination of glutathione and cysteine in yeasts by hydrophilic interaction liquid chromatography followed by on-line postcolumn derivatization.

In the present study, we report a new method for the determination of two primary thiols, cysteine (CYS) and glutathione (GSH), by hydrophilic interaction LC. The polar analytes are separated isocratically using a mobile phase consisting of 65% acetonitrile/35% ammonium acetate (15 mmol/L, pH 2.0) and are detected at 285 nm following on-line postcolumn derivatization by the thiol-selective reagent methyl propiolate.

Automated determination of total captopril in urine by liquid chromatography with post-column derivatization coupled to on-line solid phase extraction in a sequential injection manifold.

The present study reports a new liquid chromatographic (HPLC) method for the determination of the anti-hypertension drug captopril (CAP) in human urine. After its separation from the sample matrix in a reversed phase HPLC column, CAP reacts with the thiol-selective reagent ethyl-propiolate (EP) in a post-column configuration and the formed thioacrylate derivative is detected at 285 nm. Automated 4-fold preconcentration of the analyte prior to analysis was achieved by an on-line solid phase extraction (SPE) step using a sequential injection (SI) manifold.

Automated pre-column derivatization of thiolic fruit-antibrowning agents by sequential injection coupled to high-performance liquid chromatography using a monolithic stationary phase and an in-loop stopped-flow approach.

The present study reports the very first application of ethyl propiolate (EP) as an advantageous pre-column derivatization reagent for the determination of thiols by liquid chromatography (LC). Cysteine (CYS), glutathione (GSH) and N-acetylcysteine (NAC) were derivatized online under stopped-flow conditions in a sequential injection (SI) system coupled to HPLC. The formed derivatives were separated isocratically with a monolithic stationary phase (100×4.

Automated tagging of pharmaceutically active thiols under flow conditions using monobromobimane.

The thiol-specific derivatization reagent monobromobimane (MBB) is applied--for the first time--under flow conditions. Sequential injection analysis allows the handling of precise volumes of the reagent in the micro-liter range. The effect of the main chemical and instrumental variables was investigated using captopril (CAP), N-acetylcysteine (NAC) and penicillamine (PEN) as representative pharmaceutically active thiols.