Experimental Evaluation of Kinetic Characteristics of SiO2@AuNPs Nanocomposite and BSA-stabilized gold Nanoparticles toward Peroxidase-Mediated Reactions

In this study, BSA-stabilized gold nanoparticles and SiO2 @AuNPs nanocomposite were synthesized and then characterized by the TEM imaging method. The average size of BSA-stabilized gold nanoparticles was found to be as small as 13 nm while the SiO2 @AuNPs nanocomposite showed a mean size of 204 nm. The experimental studies revealed that both BSA-stabilized gold nanoparticles and SiO2 @AuNPs nanocomposite exhibit intrinsic peroxidase-like activity. Hence, to explore more precise no their catalytic efficiency and substrate affinity of them, the kinetic characteristics of both nanozymes were quantified using the Menten kinetic model, and the provided results were compared. Upon using TMB as peroxidase substrate, Vmax of 0.022 µM min-1 and a Km of 0.06 mM for the SiO2 @AuNPs nanocomposite was achieved while for the BSA-stabilized gold nanoparticles, a Vmax and Km at about 0.263 μM min-1and 0.03 mM, in order, was estimated. The Vmax of BSA-stabilized gold nanoparticles was 12.0-fold higher than that of SiO2 @AuNPs nanocomposite, revealing that the catalytic efficiency of BSA-stabilized gold nanoparticles is 12.0-fold higher than SiO2 @AuNPs nanocomposite. Besides, the Km value of SiO2 @AuNPs nanocomposite was 2-order higher than that of BSA-stabilized gold nanoparticles, indicating that the substrate affinity toward BSA-stabilized gold nanoparticles is 2.0-order higher than the SiO2 @AuNPs nanocomposite. Since, the active nodes of both nanozymes are same (i.e., gold), the difference between their catalytic efficiency and affinity can be assigned to their different sizes and the ability of the active nodes to bind the substrate. Based on the results of this work, small-size BSA-stabilized gold nanoparticles are characteristically more efficient peroxidase mimic materials than the SiO2 @AuNPs nanocomposite.