Modification of alginate degradation properties using orthosilicic acid.

Biopolymers such as alginates have been widely researched for clinical use. Their clinical application, however, have been limited due to their unpredictable and often rapid degradation rates. Here we show that the degradation of an alginate hydrogel can be tailored through the addition of orthosilicic acid (OSA). On immersion in aqueous media a negligible quantity of orthosilicic acid was released from the gel matrix. The presence of the OSA within the gel was shown to significantly slow degradation of the alginate hydrogel when immersed in a potent calcium chelator (EDTA) when compared with the control group. Sample degradation was associated with a significant calcium release from the non-modified gel; however, the orthosilicic acid modified gel did not release detectable levels of calcium over the same period. This suggests that the orthosilicic acid inhibits degradation of the gel by forming an interaction with the calcium cross-links. A rapid reduction in the storage modulus G', was observed in alginate made without OSA, however, the G'exhibited by the orthosilicic acid modified alginate did not reduce significantly (p<0.05). Furthermore, although both the OSA and alginate exhibit negative charges in solution, it is likely that they form weak interactions, this hypothesis was proven by demonstrating the efficacy of OSA for binding the alginate hydrocolloid. The findings of this study are likely to have utility in applications where controlling gel degradation is desirable, such as in cell delivery or in the controlled release of molecules in the body.