Wang resin

Standard 9-fluorenylmethoxycarbonyl (Fmoc)-protected amino acid, Ac-phenylalanine, N-hydroxy-benzotriazole (HOBt), Wang resin, and 4-dimethyl-aminopyridine (DMAP) were purchased from GL Biochem (Shanghai, China). Doxorubicin hydrochloride (DOX) was obtained from Aladdin (Shanghai, China). All other unspecified reagents were purchased from Sigma-Aldrich (St. Louis, MO, USA). Murine K12 osteosarcoma cells and normal NIH3T3 fibroblast cells were obtained from Keygen Biotech (Jiangsu, China) and cultured in a humidified incubator (37 °C, 5% CO₂). Female BALB/c mice with K12 cells were supplied by the Qinglong Mountain Center (Jiangsu, China). All animal procedures were approved and supervised by the Animal Experiment Ethics Committee of the Army Medical University (Chongqing, China).

TentaGel S Resin was purchased from Rapp Polymere (Germany, loading 0.31 mmol/g). 9-Fluorenylmethoxycarbonyl (Fmoc)-protected amino acids, 2-(1H-benzotriazole-1-yl)-1,1,3,3- tetramethyluronium hexafluoro-phosphate (HBTU), and Wang resin were obtained from GL Biochem (China). Trifluoroacetic acid (TFA), fluorescein isothiocyanate (FITC), N-methyl morpholine (NMM), piperidine, and N,N′-dimethylformamide (DMF) were all from Beijing Chemical Plant (China). 1,2-Ethanedithiol (EDT) was purchased from Alfa Aesar (USA). Dimethyl sulfoxide (DMSO) was purchased from Aldrich Chemical Co. and used without further purification. Cyanogen bromide (CNBr) was from J&K Chemical (China). The HeLa cell lines were received from the Cell Culture Center of the Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences (Beijing, China). Cell culture medium and fetal bovine serum were from WisentInc (Multicell, WisentInc, St. Bruno. The cell counting kit-8 assay (CCK-8) (Beyotime Institute of Biotechnology, China) was used. Hela cells were maintained Dulbecco’s modified eagle’s medium (DMEM) with 10% fetal bovine serum and 1% penicillin. All cells were cultured in a humidified atmosphere containing 5% CO₂ at 37 °C.