Changes induced by DC electrical field in agar, agarose, alginate and gellan gel beads

Gel beads produced from agar, agarose, alginate and gellan were interposed between a pair of electrodes in a special custom-made apparatus in order to study weight, mechanical and structural changes within them. Their shrinkage was regularly accompanied by electrolysis. The degree of weight loss depended on time and intensity of the DC electrical field, compositions of the bead and the solution in which it was immersed. At a field strength of 64 V/cm, weight losses of ∼22, 24, 35 and 47% of initial weight were observed for agarose, alginate, gellan and agar, respectively. The rate at which the reduction in weight loss occurred was also dependent on the osmotic pressure outside the bead. Contraction took place only in the region of the anode, and was associated with the electrohydrodynamic transport of hydrated ions and concomitant water exudation. The affected area of the bead resembled the shape of the electrode. The spheroid shape of the gel beads did not change significantly after DC contraction. Agarose appeared to be the least affected, with no effect on the inner layers. Agar beads revealed affected inner layers, and gellan and alginate beads were even more influenced. The beads' distortion towards a flatter shape could be beneficial in terms of their spatial arrangement, as well as more convenient for, example, insertion under the skin for transplantation and slow release of medicinal agents.