Spray dried ispaghula microspheres loaded with aspirin: a report on unsuccessful encapsulation

Aspirin loaded microspheres were prepared by spray drying using ispaghula husk mucilage (IM) and arabinoxylan (AX) as carriers. Aspirin is known for ester hydrolysis, and the degradation rate depends on pH. An attempt is made to encapsulate aspirin using IM and AX at pH of 3 and 7.4. The pH was selected based on the lowest rate of degradation reported on the literature. The yield of microspheres prepared at acid pH was low (less than 5 ) and hence discontinued. The yield of microspheres prepared at the alkaline pH was 30-40 and further characterised to study the stability of the encapsulated drug. Scanning electron microscopy revealed spherical and smooth surfaces of drug loaded AX microspheres. In contrast, IM microspheres were non-spherical and shown crystals of degraded drug product on the surface. Particle size analysis of IM and AX microspheres showed an average size of 33.1 and 24.4 ?m, respectively. Infra-red spectroscopy and X-ray diffraction analysis of the drug loaded microspheres indicated aspirin degradation. The use of IM/AX as carriers and the spray drying conditions did not prevent aspirin degradation.