Polydopamine-coated bimetallic ZIF derivatives as a H₂O₂-free oxidase mimetic for the colorimetric sensing of l-cysteine

Nanozymes have attracted much attention as a new type of artificial enzyme with great development potential in recent years. Here, a cubic Co and N co-doped porous carbon material (Co-HPNC@NC) was synthesized through the calcination of PDA-modified bimetallic Co-Zn ZIFs. Co-HPNC@NC exhibits exceptionally high oxidase-mimicking activity and effectively oxidizes the colorless 3,3 ',5,5 '-tetramethylbenzidine (TMB) to blue-colored oxidized TMB (oxTMB) without H2O2. However, the formation of oxTMB was inhibited by the addition of L-cysteine (L-Cys). Therefore, the blue color faded to colorless, causing a notable decrease in absorbance. Furthermore, Co-HPNC@NC showed good selectivity and anti-interference ability toward the detection of L-Cys. As a result, a sensitive and efficient colorimetric method has been developed to determine L-Cys with a low detection limit of 0.17 mu M (3 sigma). It is believed that this colorimetric method for the detection of L-Cys based on Co-HPNC@NC will show potential applications in biosensors and medical diagnosis.