Article,
Alginate polycation microcapsules .1. Interaction between alginate and polycation
Biomaterials, 17 (10): 1031 -- 1040 (May 1996)
Abstract
The interactions between alginate and polycations have been studied
by using different labelling techniques. Binding of poly-L-lysine
(PLL) to alginate in the gel state is mainly governed by the amount
of dissociable negative charges on the bead surface. PLL was found
to bind more rapidly to gel beads made from alginate with a high
content of mannuronic acid. The binding was enhanced by increasing
the alginate concentration on the surface by making inhomogeneous
beads. When the capsules were stored in the presence of cations with
high affinity for alginate (Ca2+, Sr2+), PLL was washed off. Less
PLL is bound to strontium alginate than to calcium alginate beads.
Two mechanisms appear to be responsible for the binding of sodium
alginate to alginate PLL capsules (coating): (i) an electrostatic
interaction between the soluble coating material and excess positive
charges on PLL on the surface; (ii) the formation of a calcium alginate
gel on the surface owing to leaching of calcium ions from the core.
The stability and efficiency of the coating as a function of molecular
size and sequential structure of the coating polymer have also been
investigated.
Tags
- ;
- ;;
- alginate;
- cytokine
- gels
- immobilization
- insulin
- islets;
- material;
- microcapsules;
- pancreas;
- polylysine;
- production;
- residues;
- transplantation;
- [isi:]
