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 Mn 2 O 3 and reducing capacity of Cys. As the templates, l -Cys is anchored to the Mn 2 O 3 nanozymes through Mn–S bonds, and the resultant Mn 2 O 3 - l -Cys is coated by the rigid silicon dioxide (SiO 2 ) imprinting layer. After the l -Cys templates are removed by calcination, molecularly imprinted SiO 2 @Mn 2 O 3 (MI-SiO 2 @Mn 2 O 3 ) is obtained. Owing to the oxidase mimicking of Mn 2 O 3, colorless 3,3′,5,5′-tetramethylbenzidine (TMB) can be converted into blue oxidized TMB (oxTMB) by the MI-SiO 2 @Mn 2 O 3; while the blue colored oxTMB can be reduced to colorless TMB by the reductive Cys. Due to the higher affinity of MI-SiO 2 @Mn 2 O 3 for l -Cys, more d -Cys is left in the solution after the Cys enantiomers are respectively incubated with the MI-SiO 2 @Mn 2 O 3, 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.