Determination of modification degree in BDDE-modified hyaluronic acid hydrogel by SEC/MS

Determination of modification degree in BDDE-modified hyaluronic acid (HA) hydrogel is of particular interest. In this paper, three crosslinking parameters (degree of total modification, t-MOD; degree of cross-link modification, c-MOD; degree of pendent modification, p-MOD) are defined and determined by quantification of the modified fragments in hydrogel digestion by size exclusion chromatography combined with mass spectrometry (SEC-MS). The digestion products of a novel hyaluronidase HAase-B produced by Bacillus sp. A50 are studied and only a few modified fragments are identified by (1)H NMR and MS. As a result, Three HA hydrogels prepared in lab have different t-MOD, c-MOD and p-MOD, but the ratio of c-MOD to p-MOD result in the almost same value of 75%. Hydrogel products from Q-Med have nearly same t-MOD about 0.8% and c-MOD about 0.1%, the ratio of c-MOD to p-MOD is about 13%. Hydrogels from ANTEIS S.A all have much higher t-MOD values, the ratio of c-MOD and p-MOD is about 8%.