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Research Article

Coating alginate beads with cross-linked biopolymers: A novel method based on a transacylation reaction

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Pages 169-183 | Received 16 Jul 1994, Accepted 10 Jan 1995, Published online: 27 Sep 2008
 

Abstract

Stable membranes were formed around alginate beads using a transacylation reaction between polysaccharidic esters, namely propylene glycol alginate (PGA) or pectin, and various proteins (human serum albumin (HSA), ovalbumin, bovine hemoglobin, lactoserum proteins). In a standard procedure, two reagents (PGA or pectin + protein) were added to a Na-alginate solution: beads were formed by dropwise addition into a calcium solution. Then the transacylation reaction was started by alkalinization of the bead suspension. A membrane was formed around the beads, made of a protein directly bound to a polysaccharide through amide linkages. The thickness of the membranes and the lysis time in trypsin were increased by raising the amount of NaOH used for the transacylation step. In a modified procedure, coated beads were obtained, incorporating PGA in the initial Na-alginate solution, and HSA in the transacylation bath. Activated charcoal was encapsulated in HSA-PGA beads, giving particles with adsorption properties towards creatinine. Assays were performed using PGA associated with alkaline phosphatase as the membrane-forming protein. Stable beads were obtained having a relative activity of 39.3%, as compared with free enzyme.

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