1 3 diisopropylcarbodiimide

All required organic solvents were purchased from Wilkem Scientific (Pawtucket, RI, USA). The Fmoc-protected building block of amino acids, including Fmoc-Trp(Boc)-OH, Fmoc-Arg(Pbf)-OH, Dde-K(Boc)-OH, Boc-βAla-OH, 3-(tritylthio)propionic acid, and H-Trp(Boc)-2-chlorotrityl resin, were purchased from Chem-Impex International Inc. (Wood Dale, IL, USA). Hydroxy-7-azabenzotriazole (HOAT), 1,3-diisopropylcarbodiimide (DIC), O-(benzotriazole-1-yl)-N,N,N’,N’-tetramethyluroniumhexafluorophosphate (HBTU), benzotriazol-1-yloxytripyrrolidinophosphonium hexafluorophosphate (PyBOP), and hydroxybenzotriazole (HOBt), glutaric anhydride (95%), triphosgene (99%), 4-dimethylaminopyridine (DMAP, 99%), N,N-diisopropylethylamine (DIPEA), triethylamine (TEA), β-mercaptoethylamine hydrochloride (cystamine hydrochloride), and 2,2′-dithiodipyridine were purchased from Sigma-Aldrich Chemical Co. (Milwaukee, WI, USA). Camptothecin (CPT) was purchased from Santa Cruz Biotech, Inc. (Dallas, TX, USA) and Paclitaxel (PTX) was purchased from Euroasias Group Inc. (Woodbridge, NJ, USA).

Colic acid, D,L-Lactide (3,6-dimethyl-1,4-dioxane-2,5-dione, C₆H₈O₄), 4-(dimethylamino)pyridine (DMAP), 1,3-diisopropylcarbodiimide (DCC), 2-(3,4-dihydroxyphenyl) ethylamine (dopamine) hydrochloride, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and Stannous octoate [Sn(Oct)₂] were purchased from Sigma (St. Louis, MO, United States). 𝜀-caprolactone (CL) was purchased from Acros Organics (Geel, Belgium). Commercial Taxotere^® and docetaxel (DTX) were provided by Shanghai Jinhe Bio-tech Co., Ltd (Shanghai, China). Methanol and acetonitrile were provided by EM Science (ChromAR, HPLC grade, Mallinckrodt Baker, United States). All other agents used were of analytical reagent grade. Boon Environmental Tech. Industry Co., Ltd (Tianjin, China) provided the ultrahigh pure water utilized throughout all the studies. Human breast cancer cell line MCF-7 was purchased from American Type Culture Collection (ATCC, Rockville, MD, United States).