Eco-friendly AuNPs@rGO nanocomposite as a peroxidase-mimic for cholesterol detection

This study presents the development of an artificial enzyme based on a nanocomposite composed of green-synthesized gold nanoparticles (AuNPs) and reduced graphene oxide (rGO), (AuNPs@rGO), for the selective and sensitive colorimetric detection of cholesterol (ChO). The nanocomposite exhibits peroxidase-like activity, catalyzing the oxidation of tetramethylbenzidine (TMB) into a blue-colored oxidized product (oxTMB) via hydroxyl radical (˙OH) generation. Cholesterol Oxidase (ChOx) enzymatically oxidizes cholesterol to produce hydrogen peroxide (H₂O₂) and cholest-4-en-3-one, and the resulting H₂O₂ is subsequently utilized by AuNPs@rGO to oxidize TMB. The nanocomposite was synthesized by integrating green-synthesized AuNPs with rGO prepared through a modified Hummers' method. Characterization using TEM, FTIR, and XRD confirmed the successful fabrication and structural features of AuNPs@rGO. The system demonstrated a linear response for cholesterol concentrations ranging from 0.2 to 1.2 mM, with a high correlation coefficient (R ² = 0.996) and a low limit of detection (LOD = 0.062 mM). These findings underscore the potential of AuNPs@rGO as a robust, efficient, and cost-effective platform for cholesterol sensing, offering a promising approach for diagnostic and biomedical applications.