Effect of preparation method on the capture and release of biologically active molecules in chitosan gel beads

Abstract

Model bioactive compounds with different molecular and functional characteristics were entrapped in gel beads prepared by polyelectrolyte complexation of chitosan and pentasodium tripolyphosphate (TPP). Three compounds of interest to the food and biomedical industries were tested: (1) lysine, (2) bovine serum albumin (BSA), and (3) ␤-galactosidase. Effects of the compound concentration in the initial chitosan solution, pH of the curing solution, and length of the curing phase on the capture efficiency were evaluated. Release rates for lysine and BSA into a phosphate buffer, distilled water, and a synthetic ocean solution were observed, and the activity of the entrapped ␤-galactosidase was determined. The capture efficiencies for lysine and BSA decreased as the concentration increased. The capture efficiency for lysine ranged from 90% at pH 5 to 20% at pH 8.6. There was no significant effect of the release media on the rate of release. BSA and lysine release reached 90% of the maximum after 100 and 50 min, respectively. The capture efficiency of ␤-galactosidase was not affected by the pH of TPP; however, enzyme activity in the beads decreased as the pH increased. Beads prepared in the pH 8.6 TPP solution had significantly higher rates of enzyme release over time.

Immobilization of glucose oxidase in chitosan gel beads

“…Good capture efficiencies were obtained using this entrapment method, for which an average value of 64 ± 2.6% was measured. These results compare well with previous work showing 50–60% capture efficiency for BSA and up to 80% in one study 6, 7. The activity of the enzyme‐containing beads compared to the free enzyme activity (i.e., the activity of the enzyme added to the solution before bead formation) was also measured.…”

“…A shift in optimal operating conditions is often observed for immobilized enzymes and can be an advantage in the final application. Additionally, it has been observed that the pH of surrounding media has an effect on the rate of release of molecules entrapped in a chitosan gel matrix 7, 18. This may be attributable to the swelling characteristics of the chitosan gel, and could be used for pH‐triggered drug delivery.…”

“…Chitosan is naturally derived (from crustaceans and fungi), biocompatible, well tolerated in vivo , and therefore has a great deal of potential for application in the medical and food industries 3, 4. The use of a chitosan gel matrix for the entrapment of proteins and enzymes was investigated by several researchers and found to result in good entrapment efficiencies (in some cases as much as 80%), but also a leakage of protein from the gel bead form 5–7. Ghanem and Skonberg7 showed release of the model protein bovine serum albumin (BSA) from chitosan gel beads over several hours.…”

Smart polymeric gels: Redefining the limits of biomedical devices

“…Importantly, "chitosan" refers to such deacetylated structures with varying molecular weights, degrees of deacetylation, and differential distribution of these deacetylated residues in the polymer network. Three-dimensional scaffolds of chitosan, in addition to chitosan films and membranes, have been fabricated by employing rapid prototyping (RP) technology [289]. Prototype modeling and visualization based on computeraided design and computer-aided manufacturing (CAD and CAM) have been instrumental in applications of the RP technology in tissue engineering [290].…”

Application of chitosan‐entrapped β‐galactosidase in a packed‐bed reactor system

“…Chitosan is an abundant, natural polymer with promising applications in the immobilization and controlled release of biological compounds. Various enzymes have been immobilized with chitosan using absorption,1, 2 covalent binding,3–9 or matrix entrapment 10–14. A primary benefit of matrix entrapment is that is can be used to immobilize enzymes and other proteins in a chitosan gel under mild processing conditions.…”