Theoretical study of diffusional release of a dispersed solute from a hollow cylindrical polymeric matrix

An exact solution for the release kinetic of a solute from inside a hollow cylindrical polymeric matrix into an infinite medium has been developed, when the initial concentration of the solute (A) is greater than the solubility limit (Cs). A combination of analytical and numerical methods was used to calculate the solute concentration profile and the release rate. The model was developed for two different strategies: 1) the release medium is flowing through the hollow cylinder in which boundary layer may be neglected, 2) the release medium inside the hollow cylinder is stagnant and the boundary layer should be considered. The results indicated that the release profiles were close to the constant release rate after a typical burst release. Also, the release profile from a solid cylindrical matrix and a hollow cylinder was compared. The results indicated that the hollow cylindrical matrix is a promising carrier when zero-order release is desirable. The present model demonstrates the potential of the hollow cylindrical matrix as a suitable geometry for sustained drug delivery systems.