Polymeric nanoparticles as carriers for stimuliresponsive drug delivery systems

Abstract

Targeted drug delivery systems has emerged from the necessity to overcome the flaws of conventional therapeutics, such as poor targeting, lack of specificity, short circulation time, etc. Drug delivery systems are required to be nontoxic and biodegradable to normal tissue cells and, at the same time, toxic and lethal to the tumor cells. The fast release of drugs may lead to undesired results caused by systemic side effects, while a slow rate may reduce the efficiency of the drug at the site of action. Even more, the drug release should take place in a controlled manner upon arrival at the target site. Nanoparticles with optimal size and surface characteristics have been designed to increase their time in the bloodstream and, subsequently, to improve their distribution. They are able o selectively carry and deliver drugs to designated sites using unique features of physiology of the tumor and its environment. The use of nanoparticles as drug carriers may be a solution to overcome the drug resistance that limits the activity of therapeutic agents. At the same time, nanoparticles accumulate in cells without being recognized by mediators of multidrug resistance and, consequently, contribute to the increase of intracellular drug concentration. Detailed information on polymers structure nd characteristics are required in order to design polymeric nanoparticles for stimuli-responsive drug carriers. Typical stimuli include pH, temperature, light, redox potential, glucose gradient, magnetic field intensity and concentration of electrolytes. The responses of the drug carriers may be different phenomena such as: dissolution/precipitation, swelling/collapsing, hydrophilic/hydrophobic transition, bond cleavage, degradation, etc. This paper provides an overview of some recent data concerning polymeric nanoparticles used as carriers for stimuli-responsive rug delivery systems and future development directions.