Structural analysis of nanocapsules by nuclear magnetic resonance.

The applicability of nuclear magnetic resonance spectroscopy to dispersed pharmaceutical carriers is demonstrated on poly-n-butylcyanoacrylate nanocapsules as a model system. Spectroscopic data are presented that simultaneously reflect the chemical nature and the molecular mobility of individual system components. The results are analysed by numeric simulation procedures that reproduce the spectroscopic results based on the given experimental conditions together with rotational and lateral diffusion of the particles. Under consideration of the complete data set, a comprehensive model on the structure of the nanocapsule system is developed. Details of the model include the assignment of system components to the capsule wall as well as to the internal and the external liquid phase. Further, the capsule size, the permeability of the capsule walls, and molecular adsorption to the capsule surface is observed and determined.