Therapeutic proteins/peptides are mostly administered as parenteral (injectable) preparations as a result of their poor oral bioavailability which is due to degradation by proteolytic enzymes, poor membrane permeability and large molecular size. However, the oral route would be preferred to the parenteral administration because it is more convenient for self-administration, non-invasive and more patient friendly. Consequently, efforts have intensified over the past two decades to maximize the extent of absorption of protein and peptide drugs in order to achieve optimum bioavailability via the oral route. A suitable oral delivery system should retain the drug and maintain its integrity until it gets to the region of maximum absorption where the protein/peptide is released. It would be advantageous for such a delivery system to be capable of attaching itself to the absorptive cells in that region during the course of drug release by means of specific interactions with the tissue components. Furthermore, movement of drug should be independent of prevailing factors in the gut during passage. This review examines the various efforts and strategies that have been used to pursue the goals of effective oral peptide delivery, progress made so far, as well as current trends and future prospects. Relevant issues and phenomena such as membrane permeability control, intestinal absorption, paracellular pathway and targeting have also been discussed.

Purpose: The effect of solvent used in dissolving chitosan (membrane material)

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.