Unless otherwise noted, all reagents were purchased from Sigma Aldrich or Fisher Scientific and used without further purification. 5-norbornene-2-carboxylic acid (97 %, predominately endo isomer) was purchased from Alfa Aesar and used without further purification. Dulbecco’s modified Eagle’s media (DMEM), phosphate buffered saline (PBS), fetal bovine serum (FBS), penicillin–streptomycin, Amphotericin B, and trypsin/EDTA were all purchased from ThermoFisher. 8-arm 20 kDa poly(ethylene glycol) thiol was purchased from JenKem Technologies and used without further purification. The norbornene functionalized cell adhesion peptide Norborne-RGDSG was synthesized according to a previously published protocol.16 (link) NIH/3T3 fibroblasts were acquired from the American Type Culture Collection (ATCC CRL1658).