A Asp/Ce nanotube-based colorimetric nanosensor for H2O2-free and enzyme-free detection of cysteine

A novel colorimetric nanosensor has been developed for high sensitive and selective detection of cysteine (Cys) based on the intrinsic oxidase-like activity of cerium nanotube coordinated with aspartic acid (Asp/Ce-NT). Under the function of Asp/Ce-NT, colorimetric reaction of TMB (3,3',5,5'-tetramethylbenzidine) takes place within five minutes without the assistance of additional oxidizing agents (e.g. H2O2). The oxidase-like activity of Asp/Ce-NT can be modulated by adjusting the ratio of Asp to Ce(NO3)3 during preparation process as well as the chirality of Asp (levogyration/L and dextrorotation/D). Compared with D-Asp/Ce-NT, L-Asp/Ce-NT exhibits more excellent activity which can be specifically depressed by Cys. According to the developed strategy, limit of detection for Cys reaches as low as 33.2 nM. The avoiding use of H2O2 would improve the repeatability and reliability. Nice recoveries from 92.5% to 100.8% are found for Cys detection in serum samples. The developed sensing assay is cost-effective and operated in H2O2-free and enzyme-free condition, providing an effective rapid detection way for practical application in disease monitoring and diagnosis.