Nano-organized shells and their application in controlled release.

AIM: The release characteristics of hollow-shell drug-delivery carriers are strongly dependent on the properties of the capsule shell, in particular its thickness and porous structure. The aim of this investigation was to conduct a detailed study of the relationship between capsule processing parameters, the resulting shell characteristics and subsequent release of an encapsulated liquid. METHODS: Hollow spherical polymer capsules of constant outer diameter were prepared using electrohydrodynamic processing and the shell thickness of the capsules varied between 100-150 nm. For each type of capsule, the size and structure of channels present in the shell were extensively studied using electron microscopy. To investigate the effect upon the release characteristics the capsules were loaded with a water-soluble dye of molecular weight approximately 961 and release profiles determined using ultraviolet spectroscopy. RESULTS: The channel diameter was found to be similar for all shell thicknesses (-5 nm). The majority of the channels were radially aligned and through the full thickness of the shell. It was found that the rate of release decreased with increasing shell thickness and it became increasingly linear with respect to time; modeling confirmed that the release was diffusion dominated. CONCLUSIONS: The results of the study show that by controlling the structural characteristics of the shell of the hollow drug-carrier particles at the nanoscale through their forming methodology, the release profile can in turn be tailored according to the application requirements.