Dual pH responsive via double - layered microencapsulation for controlled release of active ingredients in simulated gastrointestinal tract: A model case of chitosan-alginate microcapsules containing basil oil (Ocimum basilicum Linn.)

Phytogenic feed additives (PFAs) have gained more attention to replace antibiotic growth promoters (AGPs) in poultry industry. However, the efficiency of PEAs might be lost during feed pelleting, storage and gastrointestinal (GI) tract resulting in an insufficient level at the small intestine. The present work demonstrates the use of double-layered polymers with opposite charges leading to a dual pH responsiveness where the encapsulated ingredients are remained active through the acidic gastric stage and ready to be released at the intestine. Anionic sodium alginate (SA) and cationic chitosan (CS) are a good combination to represent double-layered polymer of which an effective incorporation of active ingredient, i.e. basil oil (BO), a model PEA, can be achieved. By simply fabricating SA porous microcapsules followed by the absorption of BO before the surface coating with CS, the double-layered microcapsules, CS-SA, are obtained. The release performances confirm that CS-SA retains the antioxidant and antimicrobial activities of BO under storage in addition to a great tolerance of acids, bile, trypsin, including the thermal conditions. The present work, for the first time, proposes the concept of porous double-layered polymer in microcapsule form which shows the dual pH responsive for controlled release application. The use of ionic polysaccharides is simple, biocompatible and environmentally friendly, whereas the plausible upscaling for wide range of controlled release applications has to be further investigated.