Influence of oligoguluronates on alginate gelation and on alginate gel properties

Abstract

Alginates are very abundant material in nature, mostly known for its gelling ability. Alginate is a family of linear copolymers of β-D-mannuronic acid and α-L-guluronic acid. Due to its biocompatibility, nontoxicity and its mild ionotropic gelation it have paved the way to biomedical and pharmaceutical industries. Where they are used, as immunological isolation barriers between implant and host, functionality for cell entrapment and for controlled drug delivery. Understanding how to control its gelation kinetics and how to yield mechanical properties of alginate hydrogels, is a step to fully exploit the properties of alginates. Oligoguluronates, which are almost pure α-L-guluronic acid (above 90%), opens the possibility of such control without addition of foreign substance. In the thesis high Mw alginate samples mixed with different ratios of oligoguluronates were studied. Gelation was done by in situ technique, where calcium was introduced in an inactive form of CaEGTA, and the gelation speed and the final pH was controlled by d-gluconic acid -lactone. The thesis presents results of measurement done by dynamic light scattering, nanoindentation, small angle X-ray scattering and rheology.