POST-GRADUATE STUDENTS

A unique process was used to prepare matrix-type modified release drug delivery systems by moulding and drying cross-linked chitosan gels in 24-well polystyrene plates. Different cross-linked matrix systems were prepared and evaluated in terms of their physical properties, drug content, surface morphology and swelling. The in vitro drug release profiles were subjected to kinetic modelling at two different pH values. In general, the moulded matrix systems showed statistically significantly slower drug release compared to the control group (i.e. immediate release tablet) as measured by the mean dissolution time. The moulded matrix systems obtained from chitosan cross-linked with tripolyphosphate showed the best potential for controlled drug release, but it was highly pH dependent as can be seen from the release exponent value (n) of 0.75 at pH 5.8 (anomalous transport, erosion), while the n value was only 0.40 at pH 7.4 (quasi-Fickian diffusion). The matrix systems obtained from chitosan cross-linked with sodium lauryl sulphate showed higher swelling but lower release exponent values, representing mostly quasi-Fickian diffusional release (n = 0.25 at pH 7.4, n = 0.48 at pH 5.8). This can be explained by the ability of sodium lauryl sulphate, a surface active agent, to increase the wetability of the matrix system and consequently cause an increase in the dissolution rate and release of the model drug.