Nanodevices for Facing New Challenges of Medical Treatments: Stimuli-Responsive Drug Delivery Systems

The administration of therapeutic agents for the treatment of diseases without inclusion in a pharmaceutical formulation has been rarely reported in the current literature. In this condition, drugs show poor biodistribution profiles, a lack of predictable therapeutic response, and possible toxicity. For overcoming this issue, delivery systems were developed to carry, release drugs that finally interact with target sites with accuracy. The advent of nanotechnology has encouraged the improvement of these devices for facing new challenges of medical treatments. Therefore, pharmaceutical formulations have evolved from dissolutions and powders towards nanosized-smart drug delivery systems. Consequently, in this review, they are shown the main applications of nanotechnology on the design and development of drug delivery devices such as niosomes, liposomes, lipid-based nanoparticles, polymeric micelles, polymer-based devices, liquid crystals-based systems, and nanocomposites; and their capability for responding to different external and/or internal stimuli and thus release their content in the specific site. Owing to the progress in drug (or another therapeutic agent) delivery system and those applied to the imaging diagnostics, a new subarea known as theranostic, have been launched. This strategy combines the diagnosis of diseases and their treatment in a one-step procedure through the application of external stimuli to a formulation that once administrated to the body can release their content for treating and also for following the progress of the disease. For that reason, theranostic therapy has also described in this text as another example of the evolution of formulations based on nanodevices.