Nanoparticles and liposomes: a state of the art.
The loading of drugs into ultrafine host vesicles or colloidal capsules in the nanometer size range is an acknowledged technique for the optimization of controlled drug delivery. The main purpose will always be to design inert auxiliary accompanying materials; to use body-friendly and biodegradable excipients; and to miniaturize the drug carrier system dramatically in order to get good stability, excellent absorption, quantitative tissular transfer and, therefore, the expected pharmacodynamic activity. Furthermore, side effects and foreign body irritation should be avoided and a good local and systemic tolerance during and after medication should be a condition sine qua non. The actual state of the art is shown with 4 practical application examples, namely: a cellular uptake by endocytosis and a specific lysosomotropic cell transfer with cell tracer-loaded nanoparticles; the strong immunosuppressive stimulation of nanocapsules--as new adjuvants--when loaded with viral or other antigens; the better blood-brain barrier transfer of an antiparkinson drug when covalently bound to special liposomes; and the use of minivesicles for controlled site-specific anticancer drug release (tumor targeting). In the future, we must find a possibility to deliver the correct dose of the drug precisely to the diseased target organs, tissues or cells of destination, without flooding the organism with massive drug doses. One technologic answer could be the minicarrier concept with specific pathfinders and aspecific pretargeters that serve as switchmen to guide the drug-loaded carrier to the organs, with precise spot landing.