The Comparison of Mannitol Prepared with Different PVP: Crystal Form, Morphology, Functional Properties, and In Vitro Release

The aim of this study was to investigate the effect of polyvinylpyrrolidone (PVP) with different molecular weights on the crystal form as well as the properties of mannitol. The liquid properties, morphology, and flowability of the composite excipients were first characterized. Then, the differences in compactibility, disintegrability, and in vitro release behavior of the composite excipient and curcumin-loaded samples were discussed by nanoindentation, disintegration force, etc. Finally, the effect of PVP with different molecular weights on the crystal form of mannitol and the mechanism of improvement of the properties were analyzed. Liquid properties and scanning electron microscopy showed that the solution viscosity of PVP was higher than that of mannitol, resulting in a larger particle size of the composite excipient. X-ray diffraction results revealed that PVP K12 had a stronger crystalline inducing effect on mannitol. This may be due to the shorter molecular chain of PVP K12, which may easily contact with mannitol molecules. Measurements of angle of repose, tensile strength, and nanoindentation showed that mannitol-PVP K90 had the lowest angle of repose and the highest tensile strength and plastic deformation energy, resulting in the best flowability and compactibility of mannitol-PVP K90. This suggests that modifier viscosity had a stronger influence on the functional properties of mannitol than on its crystalline properties. The in vitro release results indicated that mannitol-PVP K17 had a stronger promoting effect on the release of curcumin. This study provides guidance for the application of mannitol and the improvement of its properties.