Detection of a new reaction by-product in BDDE cross-linked autoclaved hyaluronic acid hydrogels by LC-MS analysis

Background: Hyaluronic acid (HA), a naturally occurring polysaccharide, is used in the production of dermal fillers for esthetic purposes. As it has a few days of half-life in human tissues, HA-based dermal filler is chemically modified to increase its lifetime in the body. The most common modification used in commercial HA-based filler is the cross-linking of HA chains using 1,4-butanediol diglycidyl ether (BDDE) as cross-linking agent. Residual, or unreacted, BDDE is considered nontoxic when it is <2 parts per million (ppm); therefore, the quantification of residual BDDE in the final dermal filler is mandatory to ensure the safety of the patients. Materials and methods: The present study describes the detection and characterization of one by-product of the cross-linking reaction between BDDE and HA in alkaline conditions by combining both liquid chromatography and mass spectroscopy (LC-MS). Results: After different analyses, it was found that the alkaline conditions and the high temperatures employed to sterilize the HA-BDDE hydrogel promote the formation of this new by-product, a propene glicol-like compound. LC-MS analysis confirmed that this by-product have the same monoisotopic mass as that of BDDE, a different retention time (tR), and also a different UV absorbance (lambda=200 nm) pattern. Unlike BDDE, it was observed in the LC-MS analysis that this by-product had a higher detection at 200 nm in the same assay conditions. Conclusion: These results suggest that this new compound does not have an epoxide on its structure. The discussion is open to assess the risk of this new by-product found in the production of HA-BDDE hydrogels (HA dermal fillers) for commercial purposes.