Gel properties of carboxymethyl hyaluronic acid/polyacrylic acid hydrogels prepared by electron beam irradiation

Semi-synthetic hydrogels made of carboxymethyl hyaluronic acid (CMHA) and polyacrylic acid (PAA) were synthesized using electron beam irradiation. The CMHA, with a degree of substitution of 0.87 and molecular weight of 141 kDa, was mixed with linear PAA and slightly crosslinked PAA(Carbopol). The gel properties of CMHA-PAA blends containing low amount of linear PAA (i.e. 35% CMHA: 5% PAA) irradiated at 40 kGy seemed to have similar gel properties to those of pure 40% CMHA hydrogels in our previous study. Equimolar ratio of CMHA-Carbopol blends (i.e. 10% CMHA: 10% Carbopol) were successfully crosslinked even at low irradiation dose (20 kGy) producing hydrogel with 60% gel fraction and 430 g/g degree of swelling. Furthermore, the FT-IR spectra of the 10% CMHA- 10% Carbopol blends revealed new peak at 875 cm-1 and increase of peak intensity at 1405 cm-1 due to neutralization reaction between the COOH and COO- groups of PAA and CMHA polymers. Interaction effects between the concentration of CMHA and PAA (small molar ratios) and varying irradiation doses in the gel properties in CMHA-PAA hydrogels will be explored in the future study. Radiation-crosslinking of biocompatible CMHA to other synthetic polymers, including PAA, provides a cleaner method of producing biomaterials with tunable properties that are ideal for pharmaceutical, medical, and cosmetic applications.