Investigation On Microencapsulation Of The PH-Sensitive Material Based On Gelatin/Sodium Alginate And Its Application In Omeprazole

A new pH-sensitive material based on gelatin/sodium alginate interpenetrating polymer network (IPN) by the microencapsulated method was investigated. The mixture solution in which the concentration of gelatin/sodium alginate solution was both 2wt% was used to prepare the microcapsules. Through the approach of the cross-linking microcapsules in the solvent bath composed of glutaraldehyde and calcium chloride, the formed microcapsules had the well-defined sizes of about 900μm. A comparative study of pH-dependent release of Omeprazole was carried out with such microencapsulating system. The results indicated that the microcapsules deswelled in acidic medium and swelled in alkaline, and the drugs' cumulative release had the similar principle.The cross-linking time had no great influence on the medicament release in the preparation process of microcapsules. However, it was tied up with swelling rate, swelling ratio of the microcapsules and release rate of the medicament therein. The long cross-linking time resulted in more compact structure of microcapsules and the low release rate of the medicament in the medium of same pH value. As for the cross-linking time investigated, the microcapsules of 4h cross-linking time exhibited a shorter time to reach the maximum swelling ratio and showed a minimum swelling influence on the medicament release. The microcapsules at different temperature exhibited different swelling behavior. At the medium with the same pH value, the higher the temperature was, the faster the swelling process exhibited, the greater the swelling ratio as well. All these indicated that the higher temperature was favorable to the medicament release. At a neutral or basic pH value solution, the microcapsule exhibited a greater swelling ratio, but the lower swelling ratio at an acid pH value, indicating that the influence of pH value on the swelling ratio of the microcapsules was a key factor for the control of medicament release.The release process of the microcapsules prepared by gelatin/sodium alginate was simulated using Peppas Equation. The release kinetics parameters of the microcapsules at different cross-linking time and different pH values were determined. In the neutral condition, the medicament release showed a non-Fickian form. The cross-linked molecular weights of the microcapsules at different cross-linking time were calculated via Flory-Rehner Equation. The results showed that the longer cross-linking time resulted in a lower cross-linked molecular weight of gelatin/sodium alginate IPN and was unfavorable to the medicament release into mediums. With the increasing of temperature, the cross-linked molecular weight increased which could make the release of medicament easier.It was concluded that the gelatin/sodium alginate as a kind of backing material possesses a great application merit for the preparation of pH-sensitive microcapsule for omeprazole.