Colorimetric detection of cysteine and homocysteine based on an oligonucleotide-stabilized Pd nanozyme

Cytosine-rich oligonucleotides are effective templates to stabilize Pd-based enzymatic nanoparticles with a size distribution of 3.7-5.1 nm, with different surface charge conditions and peroxidase mimicking activities. The d(C-10)-stabilized Pd nanozyme with an average diameter of 4.8 nm possesses a K-m value of 0.033 mM toward TMB and 91.29 mM toward H2O2. On the basis of the thiol-induced shielding of peroxidase-like activity of d(C-10)-Pd, a Pd-based nanozyme is employed for the first time in the sensitive detection of biothiols including cysteine and homocysteine, with a limit of detection of 3.7 nM for cysteine and 4.3 nM for homocysteine. This Pd-based peroxidase nanomimetic material exhibits promising applications in the quantitative detection of thiol-containing compounds in biological fluids.