N-Acety-L-Cysteine-Stabilized Pt Nanozyme for Colorimetric Assay of Heparin

Abstract N -Acety-L-cysteine (NAC), enriched with multiple electron-rich groups involving –SH, –C=O, and –COOH, exhibits strong affinities to transition metal ions. Herein, NAC was adopted as the stabilizing agent to synthesize a series of peroxidase-like Pt nanoclusters (NCs) with different physicochemical properties. Both the cluster size and the charge state of NAC–Pt NCs are highly dependent upon the molar ratio of [K 2 PtCl 4 ]/[NAC], contributing to different peroxidase mimicking activities. The most active Pt nanozyme (~ 1.7 nm), composed of 60% metallic Pt 0 and 40% positively charged Pt 2+ respectively, exhibits the K m of 0.132 mM for 3,3′,5,5′-tetramethylbenzidine and 35 mM for H 2 O 2 . Based on the heparin-activated enzymatic activity of NAC–Pt at pH 6.0, an ultrasensitive test was established for quantitative determination of heparin, giving the linear response of 0.5–20 μg/mL as well as the limit of detection of 2 × 10 −3  μg/mL. This proposed method is also applicable in biological fluid for practical applications. Such a colorimetric method possesses several advantages involving high sensitivity, short response, eco-friendly synthesis, low consumption of material and energy, free of expensive instrument, as well as simple operation. Graphic abstract