pH responsive itaconic acid grafted alginate microspheres for the controlled release of nifedipine

A series of pH responsive alginate-g-poly(itaconic acid) (NaAlg-g-PIA) microspheres were prepared as drug delivery matrices of nifedipine cross-linked by glutaraldehyde (GA) in the hydrochloric acid catalyst. Graft copolymers of sodium alginate with itaconic acid were synthesized using ceric ammonium nitrate. The chemical stability of the nifedipine after encapsulation into microspheres was confirmed by FTIR, DSC and X-RD analysis. The preparation conditions of the NaAlg-g-PIA microspheres such as graft yield, GA concentration, exposure time to GA and drug amount were optimized by considering the percentage entrapment efficiency, particle size, swelling capacity and their release data. The results showed that NaAlg-g-PIA microspheres are pH responsive. The release of nifedipine from grafted microspheres was slower for the pH 1.2 solution than that of the pH 7.4 buffer solution. It has been observed that an increase in exposure time, drug amount, GA and NaAlg-g-PIA concentrations causes a decrease in the nifedipine release from the microspheres, whereas an increase in graft yield leads to an increase in the nifedipine release. (C) 2010 Elsevier Ltd. All rights reserved.