Detailed characterization of an injectable hyaluronic acid-polyaspartylhydrazide hydrogel for protein delivery

The authors previously reported an injectable crosslinking hydrogel system based on the reaction between a hyaluronic acid (HA) derivative and α,β-polyaspartylhydrazide (PAHy). The HA derivative carrying dialdehyde (HAALD) was shown to react fast (30 s) with PAHy under mild conditions to produce a hydrazone conjugated hydrogel, without addition of crosslinker or catalyst. The present paper completes the initial research by examining the properties of the hydrogels in detail. HAALD-PAHy hydrogels were synthesized in PBSA solution and characterized by different methods including gel content and swelling, Fourier transformed infrared spectra, thermogravimetric analysis, in vitro degradation and biocompatibility experiments. A scanning electron microscope viewed the interior morphology of HAALD-PAHy gel whose porous three-dimensional structure enabled it to efficiently encapsulate the proteins. Sustained and stable protein release from the HAALD-PAHy hydrogel was observed during in vitro delivery experiments and exhibited its potentially high application prospect in the field of protein drug delivery.