The physicochemical interactive mechanism between nanoparticles and raffinose during freeze-drying

New methods of preparing nanoparticles and in vivo studies of their behavior have been the subject of much study. However, there exist few studies on maintaining the nanoparticle size. In this work, we report on the interaction mechanism between raffinose and nanoparticles during freeze-drying. The mean particle size of the rehydrated freeze-dried raffinose-containing nanoparticles (170.5 nm) was similar to the initial particle size before freeze-drying (156.1 nm), indicating that the particle size was maintained. The powder X-ray diffraction of the freeze-dried raffinose-containing nanoparticles shows a halo pattern, while that of the normal-dried raffinose shows a crystalline pattern. No endothermic peak of the freeze-dried raffinose appeared, while the normal-dried raffinose had an endothermic peak at 84.0 degrees C. These results suggest that there exists a relationship between the nanoparticles and the raffinose, and that the relationship depends on whether the mixture is freeze-dried or normal-dried. In the case of normal drying, the raffinose molecules have space and time to arrange themselves into regular arrangement because the nanoparticles and raffinose molecules can move around freely in water. In contrast, in the case of freeze-drying, the moisture was sublimed while the raffinose molecules and nanoparticles were immobilized in the ice, thereby preventing aggregation. (c) 2014 Elsevier B.V. All rights reserved.