Anhydrous dichloromethane

Four-arm PEG (20 kDa) and 8-arm PEG (10 kDa) were purchased from Jemkem (Plano, TX, USA). Anhydrous dichloromethane (DCM) was purchased from JT Baker (Phillipsburg, NJ, USA), and ethyl ether was purchased from Fisher Scientific (Waltham, MA, USA). Norbornene-methyl-amine was purchased from TCI (Tokyo, Japan), and α-chymotrypsin was purchased from VMR Life Science (Randor, PA, USA). Matrix metalloproteinase sensitive peptide linker (MMPs peptide linker, H₂N-KCGPQGIWGQCK-amide) was purchased from BeadTech (Gyoung-gi, Korea). For cell culture, high glucose Dulbecco's Modified Eagle Medium was purchased from Corning Life Science (Tewksbury, MA, USA), and low glucose Dulbecco's Modified Eagle Medium was purchased from HyClone (Anaheim, CA, USA). The fetal bovine serum and antibiotic-antimycotic were purchased from Gibco (Grand Island, NY, USA). For RT-qPCR, we used the NucleoSpin® RNA kit (Macherey-Nagel, Düren, Germany) and TRI reagent (Invitrogen, Carlsbad, CA, USA). PrimeScript RT reagent kit and SYBR Premix Ex Taq II kit were purchased in TaKaRa (Kusatsu, Japan). PCR primers were purchased from Bioneer (Daejon, Korea). All other chemicals were purchased from Sigma-Aldrich (St. Louis, MO, USA) and used without further purification.