Electrically controlled release of macromolecules from cross-linked hyaluronic acid hydrogels

Abstract

The effect of an electrical field on the swelling and release of two macromolecular solutes from crosslinked hyaluronic acid (HA) hydrogels was investigated. HA is a natural occurring polysaccharide and polyelectrolyte, and its crosslinked hydrogels are highly swollen in water,but it loses much of its water capacity when transferred to solutions of high ionic strength. Application of an electrical field causes rapid deswelling of the hydrogels, due to the partial protonation of the ionized polyelectrolyte network. Gels loaded with macromolecules with a high negative charge poly(styrene sulphonic acid) sodium salt and poly (glutamic acid, tyrosine) sodium salt, exhibit only moderate swelling but when transferred to water, a rapid swelling process was observed. Applying an electrical field to these gels dramatically reduces the swelling process. This behaviour could form the basis of a responsive and pulsatile release system for large negative solutes, releasing solute when the electric field is removed, and inhibiting release when the field is reapplied.