For the synthesis of PAMAM-GGPLGVRGDG-mPEG4000, the peptide would be first PEG via click reaction and then conjugate to the folate-modified PAMAM dendrimers. Typically, mPEG4000-N3 (0.025 mmol, 100 mg) and alkynyl-GPLGVRGDGG (0.03 mmol, 25.8 g) were dissolved in 10 ml of DMF, followed by the addition of CuSO4.5H2O (0.04 mmol, 10 mg) and ascorbic acid (0.08 mmol, 15 mg). The reaction was carried out in a single neck flask under nitrogen protection and would continue for 24 hours. The PEGylated peptide was obtained via dialysis (1000 Da, MWCO, Millipore) and denoted as mPEG4000-GPLGVRGDGG. Subsequently, the as-prepared mPEG4000-GPLGVRGDGG (0.02 mmol, 100 mg) was dispersed into 10 ml of DMF, where its carboxylic groups were activated after incubating with EDC (0.06 mmol, 11.5 mg) and NHS (0.06 mmol, 6.9 mg) for 30 min. PAMAM (0.02 mmol, 14.78 mg) was then added to the reaction mixture, and the incubation would continue for another 24 hours, of which the product was extracted via dialysis (2000 Da, MWCO, Millipore) and denoted as mPEG-GPLGVRGDGG-PAMAM.