Fig. 1.

The schematic diagram of preparation of GNPs and GAL-PEG-GNPS. GNPs in 20 nm diameter were prepared using sodium citrate reduction method. To prepare GAL-PEG-GNPs, 0.1 mL of bare GNPs at 0.1 mg/L (pH 7.5) were mixed with excessive amount of thiol-PEG-amino and incubated at 4 °C overnight, followed by thiol-PEG grafting. 100 μL of sulfo-NHS and EDC (5:1, pH 5.0) were incubated with 20 μg of GAL for 6 h at 37 °C to active carboxyl groups of GAL first, and 20 μL of PEGylated GNPs at 0.1 mg/L (pH 7.2) were incubated with the mixture at 37 °C for 2 h to finally produce GAL-PEG-GNPs