Comparative toxicity study of hyaluronic acid fillers crosslinked with 1,4-butanediol diglycidyl ether or poly (ethylene glycol) diglycidyl ether.

Dermal fillers comprising injectable hyaluronic acid (HA) are widely used for soft tissue augmentation, often using crosslinking agents such as 1,4-butanediol diglycidyl ether (BDDE) or poly (ethylene glycol) diglycidyl ether (PEGDE). Here, we assessed the physical properties, toxicity, and inflammatory reactions of HA fillers crosslinked with either BDDE (HA-BDDE filler) or PEGDE (HA-PEGDE filler) in in vitro and in vivo investigations. The HA-PEGDE filler exhibited higher G', tan δ, G*, and complex viscosity values compared to the HA-BDDE filler, while maintaining similar cohesivity. The filler extracts were used to evaluate cytotoxicity. HA-PEGDE filler extracts exhibited reduced cytotoxicity, oxidative stress, and inflammation in human keratinocytes (HaCaTs) and fibroblasts (HDFs) than that of HA-BDDE filler extracts. In animal studies, SKH1-hairless mice were injected subcutaneously with varying volumes of fillers and euthanized at 1- and 4-weeks post-injection. Compared with the HA-BDDE filler, the HA-PEGDE filler displayed favorable biocompatibility, decreased tumor necrosis factor (TNF)-α and interleukin (IL)-1β expression and reduced inflammatory cell infiltration. Our results demonstrate that the HA-PEGDE filler has comparable rheological properties and lower toxicity than the HA-BDDE filler, suggesting its suitability as an alternative in applications where minimal inflammatory response is crucial.