In this study, considering the peroxidase-like activity of the SiO₂@AuNPs nanocomposite, their biochemical properties including, pH stability, cycling stability, shelf stability, and kinetic parameters were investigated. The results revealed that the as-mentioned SiO₂@AuNPs nanocomposite reveal its maximal activity at pH=4.0 along with saving 83.3% of its maximal activity at pH=5.0. Besides, the reusability and shelf-storage studies exhibited that the SiO₂@AuNPs nanocomposite retained 90% and 100% of its initial activity after 5 operational cycles and 30 days of storage, in order. The kinetic parameters of the as-prepared nanozymes were calculated using Menten kinetic model, revealing a V_max of 1.35 µM min^-1 and a K_m as low as 0.06 mM for the SiO₂@AuNPs nanocomposite. Based on the results of this work, the as-prepared SiO₂@AuNPs nanocomposite with intrinsic peroxidase-like activity shows high substrate affinity and catalytic efficiency along with excellent cycling- and shelf-stability, making them suitable for application in peroxidase-mediated reactions instead of the native enzyme.

The COVID-19 pandemic over the past years has shown a great need for rapid, low-cost and on-site detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this paper, an aptamer-based colloidal gold nanoparticle lateral flow test strip was well developed to realize the visual detection of wild type SARS-CoV-2 spike protein (SP) and multiple variants. Under the optimal reaction conditions, a low detection limit of SARS-CoV-2 S protein of 0.68 nM was acquired, and the actual detection recovery was 83.3% to 108.8% for real world samples. This suggests a potential tool for the prompt detection of SARS-CoV-2 with good sensitivity and accuracy, and a new method for the development of alternative antibody test strips for the detection of other viral targets.

Bisphenol A diglycidyl ether (BADGE) is widely existed in the inner coating of canned foods. It migrates into food and generate various derivatives in the process of storage, such as Bisphenol A (2, 3-dihydroxypropyl) glycidyl ether (BADGE·H2O), Bisphenol A (3-chloro-2-hydroxypropyl) glycidyl ether (BADGE·HCl) and Bisphenol A (3-chloro-2-hydroxypropyl) (2, 3-dihydroxypropyl) glycidyl ether (BADGE·HCl·H2O), which have negative effects on human health. A gold nanoparticle-based immu-nochromatographic assay for simultaneous detection of BADGE and its derivatives was developed by using a broad-spectrum polyclonal antibody, and the detection can be finished in 15 min. The visuali-zation of results was processed by Adobe Photoshop CC software to achieve quantitative analysis and the detection limit (IC15) is 0.97ng/mL. The recoveries of BADGE and its derivatives at various spiking levels in canned food samples ranged from 79.86% to 93.81%. The detection results of the proposed immu-nochromatographic assay were also validated by HPLC analysis, and got good consistency (R2=0.9580).