Performance of three-layer controlled release devices with uniform or non-uniform material properties: Experiment and computer simulation

We report a study on the release process of an osmotically active solute from three-layer (ABA) matrices, with either uniform or non-uniform material properties. The ABA matrices consisted of inner cellulose (CEL) layer, loaded with NaCl, and solute-free, outer layers made from either cellulose or cellulose acetate (CA). The experimental release performance of the ABA devices, pertaining to unsaturated matrices, showed that (i) the outer CA or CEL layers are effective in suppressing the burst effect to an extent determined by the relative thicknesses of the outer and inner layers, LA/L (ii) manipulation of the ratio LA/L modifies the duration of the release process but is ineffective in stabilizing the variation with time of the release rate at later stages of the process. Simulation of the experimental data was performed on the basis of a previously developed relevant model, with input parameters derived from the release experiments from monolithic matrices or taken from literature. Theoretical predictions on the effect of various system parameters are also presented.