The mixture was then stirred for an additional 30 min, then was centrifuged at 10,000 × g at 4◦C for 30 min,after which the gold pellets were suspended in 1 mL of dilution buffer: 20 mM Tris/HCl buffer (pH 8.2) containing 1% (w/v) BSA,3% (w/v) sucrose, and 0.02% (w/v) sodium azide.