The effect of starch material, encapsulated protein and production conditions on the protein release from starch microspheres.

The present study describes the preparation of 11 batches of starch microspheres for drug delivery. Parameters such as the type of starch material, the type of protein, and the incubation time of the process were varied, and the obtained microspheres differed in yield, encapsulation efficiency and physical properties. The crystalline/ordered structure (obtained through X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC)), the microscopic appearance and the surface morphology (viewed with scanning electron microscopy (SEM)) were found to differ between the batches depending on the starch type, encapsulated protein and incubation conditions that were employed. Freeze-drying was found to have a destructive effect on the ordered structure of the starch and this effect varied with regard to preparation conditions. Drug release experiments demonstrated that the release from the starch matrix depended on the type of protein as well as on the incubation time during the manufacturing at temperatures of 6 degrees C and 37 degrees C. The enzymatic degradation of starch was slightly different between the materials depending on the crystalline/ordered structure that had formed during the preparation.