Following washing for four times with DMF and dichloromethane, the resin was dried under vacuum. Subsequently, the as-prepared peptides were cleaved from the resin using standard trifluoroacetic acid (TFA) cleavage procedures in TFA with 5% H2O followed by multiple ether extractions. All synthetic peptides were purified to >95% by reverse-phase high-pressure liquid chromatography performed with a liquid chromatograph (Waters,
Milford, MA, USA). Peptides were analyzed by mass spectrometry to confirm that the desired product was obtained. Preparation of QDs and QD-peptide conjugates The CdTe QDs were prepared according to our previous report . Briefly, 5 mmol of CdCl2·5H2O was dissolved in 110 mL of water, and 12 mM of thioglycolic acid (TGA) BAY 80-6946 solubility dmso was added under stirring. NaOH solution was used to adjust the pH of the resultant solution to 11. The solution was cleared by N2 bubbling for 30 min. Under stirring, 2.5 mM of oxygen-free NaHTe solution
was injected into the solution. After reflux at 100°C for 4 h, the TGA-capped CdTe QDs were synthesized. The obtained QDs were purified by precipitation in ethanol and redispersed in phosphate-buffered saline (PBS; 0.2 mg/mL KCl, 1.44 mg/mL Na2HPO4, 0.24 mg/mL KH2PO4, 8 mg/mL NaCl; pH 7.4). Anlotinib Absorbance spectrum and photoluminescence spectrum were analyzed to characterize the fluorescent properties of QDs with a PerkinElmer LS 55 spectrofluorimeter (Waltham, MA, USA). Afterwards, 0.5 mL of 3 mg/mL QDs and 0.5 mL of 0.8 mg/mL antigenic peptides were mixed, and then 50 μL
of 1 mg/mL EDC was added. The resulting solution reacted at room temperature for 3 h with continuous mixing and then stayed at 4°C for 24 h. Bovine serum albumin (BSA) was added into GNAT2 the solution at a concentration of 1 mg/mL and incubated at room temperature for 3 h. The QD-labeled SPAs were then centrifuged at 15,000×g for 30 min, and the supernatant was discarded. A volume of 1.05 mL PBS with 0.5% Tween-20 (PBST;, v/v) was used to resuspend and wash QD-labeled antigenic peptides by centrifugation at 15,000×g for three times. Finally, the QD-labeled conjugates were dispersed in 1.05 mL PBST and kept at 4°C for usage. Then, 1% agarose gel electrophoresis was performed to analyze the QD-peptide conjugates. Standard serum samples HBV-positive sera were collected from patients who were confirmed by enzyme-linked immunosorbent assay (ELISA) test. The negative sera were collected from healthy volunteers. One hundred anti-HBV surface antigen antibody-positive sera and 100 negative sera were mixed separately at equal volume ratio. The mixtures were used as standard antibody-positive and antibody-negative serum samples.