Colorimetric determination of sarcosine in human urine with enzyme-like reaction mediated Au nanorods etching

Abstract

A colorimetric method for sensitive detection of sarcosine was established based on enzyme-like reaction mediated etching of Au nanorods (AuNRs). Carbon quantum dots (CQDs) originated from litchi peel showed peroxidase-like activity, enabling to accelerate the etching of AuNRs in the presence of H2O2 and I− ions. Sarcosine oxidase (SOX) catalyzed the oxidation of sarcosine to release H2O2 which oxidized I− to I2 under the catalysis of CQDs. AuNRs were then etched by I2 along the longitudinal direction, resulting in a blue-shift of the localized surface plasmon resonance (LSPR) peak of AuNRs. The peak-shift was used for the determination of sarcosine. The influences of pH, CQDs concentration and etching time on the signal response were investigated. Under the optimized conditions, the LSPR peak shift of AuNRs was linearly dependent on sarcosine concentration ranged from 0.02 to 1.0 μmol/L, and the detection limit (3σ/k) was calculated to be 0.011 µmol/L. In order to verify its feasibility and reliability, the method was used for determining sarcosine in human urine samples from healthy volunteers with recoveries ranged from 95.7% to 102.2%, indicating the potential application of the developed method.