Colorimetric Aptasensor for Sensitive Glypican-3 Detection Based on Hemin-Reduced Oxide Graphene-Platinum@Palladium Nanoparticles With Peroxidase-Like Activity

In recent years, nanozyme-based sensing platforms have been attracted for their excellent performances in practical applications. Glypican-3 (GPC3) has been extensively regarded as a sensitive biomarker for hepatocellular carcinoma (HCC). In this work, the hemin-reduced oxide graphene-platinum@palladium nanoparticles (H-R-Pt@Pd NPs) with the peroxidase-like activity have been used to construct a facile colorimetric aptasensor for GPC3 detection. GPC3 aptamer (Apt) conjugated to the surface of H-R-Pt@Pd NPs serves as a signal probe, and GPC3 antibody (Ab) uses as a capture probe. In the presence of GPC3, it was recognized by the Ab and the Apt on the H-R-Pt@Pd NPs and initiated the formation of an H-R-Pt@Pd NPs-Apt/GPC3/Ab sandwich structure complex. Taking advantage of the excellent enzymatic catalytic properties, H-R-Pt@Pd NPs can oxidase colorless 3,3',5,5'-tetramethylbenzidine (TMB) into blue oxTMB with the presence of H2O2, and the absorbance of the system at 652 nm changed consequently, which realize the sensitive colorimetric detection of GPC3. In addition, the catalytic mechanism of H-R-Pt@Pd NPs was confirmed by free radical experiments to be induced by hydroxyl radicals ( $\cdot $ OH). Under optimal conditions, the aptasensor has a linear range of 10–300 ng/mL and a limit of detection (LOD) of 5.06 ng/mL. Furthermore, the aptasensor is employed to detect GPC3 in human serum samples with the recoveries of 105.94%–116.33% and relative standard deviations (RSDs) of 0.93%–3.08%. Overall, this assay possesses high selectivity and operability, and good sensitivity, indicating the potential for GPC3 detection in the field of clinical HCC diagnosis.