Imiquimod r 837

The four-arm polyethylene glycol thiol (PEGSH, ≥95%, MW ​= ​5000) was purchased from Huateng Pharmaceutical (Changsha, China) and stored at −20 ​°C. And poly (ethylene glycol) diacrylate (PEGDA, MW ​= ​700) was purchased from Sigma-Aldrich (St. Louis, USA) and stored at 4 ​°C. PEGSH and PEGDA are used for the preparation of the hydrogel. The chemotherapy drug Doxorubicin (Adriamycin) HCl (Dox) and the immune adjuvant Imiquimod (R837) were purchased from Selleck Chemicals (Shanghai, China). Melanoma cells B16F10 and dendritic cells DC2.4 were gifted by Dr. Xiao Zhou from the Department of Medical Laboratory Science, Xiangya Medical College, Central South University, China. Skin cells HaCaT was gifted by Prof. Hemin Nie from the College of Biology, Hunan University, China. The B16F10 ​cells and DC2.4 ​cells were cultured in RPMI-1640 culture medium (Gibco, ThermoFisher Scientific, Carlsbad, CA, USA), and HaCaT cells were cultured in high-glucose DMEM culture medium (HyClone, Logan, Australia) at 37 ​°C in humidified incubator of 5% CO₂ and supplemented with 10% fetal bovine serum (FBS; Gibco, ThermoFisher Scientific, Carlsbad, CA, USA), penicillin (100 units/mL, NCM biotech, Suzhou, China), and streptomycin (100 ​mg/mL, NCM biotech, Suzhou, China).