Maleimide poly ethylene glycol hydroxy mal peg oh

Poly (ethylene glycol) (PEG, M_n = 1500 Da), $\mathsf{\epsilon }$ -caprolactone (CL, 99%) and tert-butyl carbazate (Boc-NHNH₂, 99%) were purchased from Aladdin Industrial Co., Ltd. (Shanghai, China). Stannous octoate (Sn(Oct)₂, 99%) was obtained from Sigma-Aldrich China (Shanghai, China). 4-Nitrophenyl chloroformate (NPC, 99%), trimethylamine (TEA, 99%), and trifluoroacetic acid (TFA, 99%) was purchased from J&K chemical Co. Ltd. (Beijing, China). Doxorubicin (DOX, 99%) and curcumin (CUR, 99%) were purchased from Dalian Meilun biotechnology Co., Ltd. (Dalian, China). Maleimide-poly(ethylene glycol)- hydroxy (Mal-PEG-OH) with the molecular weight of 2000 was purchased from JenKem Technology Co., Ltd. (Beijing, China). Cys–Arg–Gly–Asp–Lys (CRGDK, 99%) peptide was provided by GL Biochem. Ltd. (Shanghai, China). Dichloromethane (DCM, 99%), dimethyl sulfoxide (DMSO, 99%), tetrahydrofuran (THF, 99%), and other reagents were commercially available from Damao Chemical Co., Ltd. (Tianjin, China). N,N-dimethylformamide (DMF, 99%) for HPLC Analysis was purchased form Merck (Darmstadt, Germany).
The Neuropilin-1 overexpressed human umbilical vein endothelial cells (HUVEC) and Adriamycin resistant breast cancer cells (MCF-7/ADR) were obtained from Procell life science and technology Co., Ltd. (Wuhan, China).