Molecular and nanoparticle postcolumn reagents for assay of low-molecular-mass biothiols using high-performance liquid chromatography

Colorimetric detection of biothiols and Hg2+ based on the peroxidase-like activity of GTP

Guanosine-5'-triphosphate (GTP) not only plays a key role in a majority of cellular processes but also be proposed as a peroxidase-like mimic. Compared with nanozymes, GTP shows good tolerance under harsh conditions, which can be used to construct an easy colorimetric analysis for the detection of biomolecules. Here, on the basis of the peroxidase-like activity of GTP which can catalyze the oxidation of 3,3',5,5'-tetramethyl benzidine dihydrochloride (TMB), colorimetric sensing was established for biothiols and Hg²⁺. Biothiols reduced the oxTMB back to colorless TMB, and Hg²⁺ restored the formation of oxTMB, leading to the recovery of color. This method not only provides a platform for the detection of metal ions and biothiols, but also shows that GTP has great potential for analytical detection.

Colorimetric determination of biothiols with AuNPs@MoS2 NSs as a peroxidase mimetic enzyme

The synthesis of AuNPs@MoS2 NSs was achieved and the sensing of biothiols was carried out using AuNPs@MoS2 NSs as enzyme mimics.

Facile synthesis of IrO2/rGO nanocomposites with high peroxidase-like activity for sensitive colorimetric detection of low weight biothiols

In this work, we reported a novel nanozyme synthesized by decorating highly dispersed ultrafine IrO₂ nanoparticles on reduced graphene oxide (rGO) nanosheets via a simple hydrothermal method. The as-prepared IrO₂/rGO nanocomposites exhibited intrinsic peroxidase-like activity and could catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to produce blue product in the presence of H₂O₂. Catalytic kinetic of IrO₂/rGO nanocomposites followed Michaelis-Menten behavior, exhibiting a higher affinity to TMB than horseradish peroxidase (HRP) enzyme. Catalytic mechanism studies suggested that the peroxidase-like activity of IrO₂/rGO nanocomposites originated from their ability of electron transfer between substrate and H₂O₂. On the basis of high peroxidase-like activity of IrO₂/rGO nanocomposites, a colorimetric strategy for rapid and sensitive detection of low weight biothiols was developed. The colorimetric detection assays for low weight biothiols showed high selectivity against other amino acids. Therefore, the IrO₂/rGO nanozyme is expected for promising potential applications in the biosensor, diagnostics and environment.

Analytical methods involving separation techniques for determination of low-molecular-weight biothiols in human plasma and blood

Low-molecular-weight biothiols such as homocysteine, cysteine, and glutathione are metabolites of the sulfur cycle and play important roles in biological processes such as the antioxidant defense network, methionine cycle, and protein synthesis. Thiol concentrations in human plasma and blood are related to diseases such as cardiovascular disease, neurodegenerative disease, and cancer. The concentrations of homocysteine, cysteine, and glutathione in plasma samples from healthy human subjects are approximately in the range of 5-15, 200-300, and 1-5 μM, respectively. Glutathione concentration in the whole blood is in the millimolar range. Measurement of biothiol levels in plasma and blood is thought to be important for understanding the physiological roles and biomarkers for certain diseases. This review summarizes the relationship of biothiols with certain disease as well as pre-analytical treatment and analytical methods for determination of biothiols in human plasma and blood by using high-performance liquid chromatography and capillary electrophoresis coupled with ultraviolet, fluorescence, or chemiluminescence detection; or mass spectrometry.

Determination of biothiols by a novel on-line HPLC-DTNB assay with post-column detection

A novel on-line HPLC-DTNB method was developed for the selective determination of biologically important thiols (biothiols) such as L-cysteine (Cys), glutathione (GSH), homocysteine (HCys), N-acetylcysteine (NAC), and 1,4-dithioerythritol (DTE) in pharmaceuticals and tissue homogenates. The biothiols were separated on C18 column using gradient elution, reacted with the postcolumn reagent, DTNB in 0.5% M-β-CD (w/v) solution at pH 8, to form yellow-colored 5-thio-2-nitrobenzoic acid (TNB), and monitored with a PDA detector (λ=410 nm). With the optimized conditions for chromatography and the post-column derivatization, 40 nM of NAC, 40 nM of Cys, and 50 nM of GSH can be determined. The relative standard deviations of the recommended method were in the range of 3.2-5.4% for 50 μM biothiols. The negative peaks of biothiol constituents were monitored by measuring the increase in absorbance due to TNB chromophore. The detection limits of biothiols at 410 nm (in the range of 0.04-0.58 μM) after post-column derivatization with DTNB+M-β-CD were much lower than those at 205 nm UV-detection without derivatization, and were distinctly lower than those with post-column DTNB alone. The method is rapid, inexpensive, versatile, nonlaborious, uses stable reagents, and enables the on-line qualitative and quantitative estimation of biothiol constituents of biological fluids and pharmaceuticals.