Protein Retention in Chitosan-Alginate Microcapsules Modified for Possible Oralprotein Deliverywith Selected Excipients

Abstract

The protein retention characteristics of chitosan-alginate microcapsules modified with selected excipients were evaluated in vitro for oral protein delivery using Bovine serum albumin (BSA) as the 'model' protein.The microcapsules were prepared by extruding alginate solution containing BSA and either talc, Eudragit L100, Eudragit RSPM, microcrystalline cellulose (MCC) or HPMCAS, into chitosan/calcium chloride solution. Protein retention in microcapsules at different pH of the elution medium was determined spectrophotometrically at ë max of 280 nm. Microcapsules containing MCC and talc had the highest protein retention capacity, with 68% and 60%, respectively, of protein still available in the core of the microcapsules after 9 h at pH 1.2, while HPMCAS failed to retain any protein after 9 h at the same pH. Protein retention in microcapsules modified with other additives was intermediate. At higher pH values, microcapsules containing talc still exerted the highest protein retention of 77% (pH 3) and 85% (pH 6), followed by microcapsules containing Eudragit RS PM, 65% (pH 3) and 80% (pH 6), after 9 h. This work has demonstrated that blending the core with suitable excipient enhanced protein retention capacity of chitosanalginate microcapsules. This technology can be employed in oral delivery of protein/vaccines to human and aquaculture.

Optimising oral systems for the delivery of therapeutic proteins and peptides

“…Protein release was determined at different pH media spanning the pH range of the gut (Figure 1). It was observed that microcapsules modified with talc and microcrystalline cellulose had higher protein retention in the core in all the pH tested (Okhamafe et al, 1996;Ahonkhai et al, 2005;Arhewoh et al, 2005). This shows that modification of the core of chitosan-alginate microcapsules could facilitate drug targeting to the colon.…”

“…Furthermore, membrane modulation is often employed to improve the strength and stability of the microcapsule itself (Okhamafe and Goosen, 1999). Ahonkhai et al (2005) recently found that by incorporating polymers or solid fillers in the core of chitosan-alginate microcapsule, the release of a model protein, bovine serum albumin (BSA) can be modulated such that 70% of the protein is delivered to the desired absorption site in the gut 9 h later (see Figure 1). Related applications include the pre-purification and concentration of products of cell encapsulation, release into the circulatory system of hormonal and enzymatic products generated by bioartificial organs which are protected from components of the immune system, principally immunoglobulins.…”