“…Formaldehyde-releasing agent cell cytotoxicity assays were performed as we have previously described. 33 Briefly, healthy human skin fibroblasts (HSFs) from American Type Culture Collection (ATCC, Manassas, VA, USA) were cultured in dermal cell basal media (ATCC) using a serum-free fibroblast growth kit provided by the company (ascorbic acid, EGF/TGF-b1, glutamine, hydrocortisone, insulin, and fibroblast growth supplements). Cells were grown in 5% CO 2 and 95% ambient air at 378C until confluent.…”