A Molecularly Imprinted Chiral Sensor for Colorimetric Resolution of Cysteine Enantiomers Utilizing Oxidase Mimicking of Mn2O3 and Reducing Capacity of Cysteine

A surface molecularly imprinted chiral sensor is designed for colorimetric resolution of cysteine (Cys) enantiomers by utilizing oxidase mimicking of Mn2O3 and reducing capacity of Cys. As the templates, l-Cys is anchored to the Mn2O3 nanozymes through Mn-S bonds, and the resultant Mn2O3-l-Cys is coated by the rigid silicon dioxide (SiO2) imprinting layer. After the l-Cys templates are removed by calcination, molecularly imprinted SiO2@Mn2O3 (MI-SiO2@Mn2O3) is obtained. Owing to the oxidase mimicking of Mn2O3, colorless 3,3',5,5'-tetramethylbenzidine (TMB) can be converted into blue oxidized TMB (oxTMB) by the MI-SiO2@Mn2O3; while the blue colored oxTMB can be reduced to colorless TMB by the reductive Cys. Due to the higher affinity of MI-SiO2@Mn2O3 for l-Cys, more d-Cys is left in the solution after the Cys enantiomers are respectively incubated with the MI-SiO2@Mn2O3, which can make the fading of oxTMB easier. Therefore, colorimetric resolution of the Cys enantiomers can be achieved by the developed molecularly imprinted chiral sensor.