Colorimetric determination of biothiols based on peroxidase-mimicking Ag nanoparticles decorated TiC nanosheets.

Ag nanoparticle-decorated TiC nanosheets (AgNPs@TiC NSs) were facilely synthesized via a self-reduction approach, in which TiC NSs acted as both reductant and supporter. The AgNPs@TiC NS nanocomposite exhibited excellent peroxidase-like activity with o-phenylenediamine (OPD) and HO as substrates. The catalytic behavior followed the typical Michaelis-Menten kinetics; Michaelis constant (K) and maximum initial velocity (V) for OPD were 0.263 mM and 43.2 × 10 M s, indicating high affinity and high catalytic efficiency towards OPD. The catalytic mechanism was revealed to be an accelerated electron transfer process. Based on the inhibition effect on the peroxidase-like activity of AgNPs@TiC NSs, a simple, fast, and sensitive colorimetric method for detection of low-weight biothiols (cysteine (Cys), homocysteine (Hcy), and glutathione (GSH)) was developed by measuring the absorbance at 425 nm. The colorimetric method displayed wide linear range (50 nM to 50 μM for Cys, 10 nM to 250 μM for Hcy, 10 nM to 50 μM for GSH), low limit of detection (48.5 nM for Cys, 5.5 nM for Hcy, 7.0 nM for GSH), and good selectivity and short assay time (3 min). Moreover, the feasibility of this colorimetric sensor was demonstrated by accurately determining Cys in diluted human serum samples; good recovery (95.9-101.0%) and low relative standard deviations (2.8-4.9%) were obtained, showing great promise for point-of-care test in clinical samples.