Engineering approaches for drug delivery systems production and characterization.

To find and to test the therapeutic effectiveness (and the limited adverse effects) of a new drug is a long and expensive process. It has been estimated a period of ten years and an expense of the order of one billion USD are required. Meanwhile, even if a promising molecule has been identified, there is the need for operative methods for its delivery. The extreme case is given by gene therapy, in which molecules with tremendous in-vitro efficacy cannot be used in practice because of the lack in useful vector systems to deliver them. Most of the recent efforts in pharmaceutical sciences are focused on the development of novel drug delivery systems (DDSs). In this review, the work done recently on the development and testing of novel DDSs, with particular emphasis on the results obtained by European research, is summarized. In the first section of the review the DDSs are analyzed accordingly with their scale-size: starting from nano-scale (liposomes, nanoparticles), up to the micro-scale (microparticles), until the macroscopic world is reached (granules, matrix systems). In the following two sections, non-conventional testing methods (mechanical methods and bio-relevant dissolution methods) are presented; at last, the importance of mathematical modeling to describe drug release and related phenomena is reported.