Micro bca protein assay kit

Cap-AuNPs were prepared by mixing AuNPs (1 mL) with recombinant Cap protein (100 μL, 1 mg/mL) and stirred for 1 h at 4°C. To obtain washed Cap-AuNP formulation, excess free Cap protein was removed by repeated centrifugation (12,000 rpm for 60 min at 4°C) and resuspension of the pellet in PBS for a total of three wash cycles. The stability of the conjugate was assessed by adding 10% sodium chloride.30 (link) The conjugates were confirmed by UV-Vis, DLS, and Fourier transform infrared spectroscopy (FTIR) (Thermo Fisher Scientific). The quantification of Cap-AuNPs was measured as follows: 1 mL Cap (20 μg/mL) was added into 1 mL AuNPs, stirred for 1 h at 4°C, and then AuNPs suspension was centrifuged down at 12,000 rpm for 60 min at 4°C. The supernatant was collected and the concentration of Cap was measured by Micro BCA Protein Assay Kit (Boster, Wuhan, People’s Republic of China).

Evaluation of the nonspecific protein adsorption was carried out according to previously reported method [31 (link)]. Cylindrical hydrogels were immersed in 1 mL bovine serum albumin solution (BSA, 2 mg/mL) and incubated at 37 °C for 90 min. The hydrogels were taken out carefully and washed out with PBS to remove loosely adsorbed proteins. The adsorbed proteins were detached by ultrasound for 10 min, and measured by a micro-BCA protein assay kit (Boster Biotechnology Co., Ltd) according to the standard protocol. The test was conducted in triplicate and average values were recorded.