ABSTRACT
The surface-modified long-circulating polymeric nanoparticles are used to deliver both genes and drugs to the tumor tissues. The mechanisms of long-circulation through steric hindrance when in circulation and preferential accumulation in the tumor mass or inside the cells as a result of the cleavage of the disulfide bonds in the highly reductive tumor-microenvironment can be exploited for the delivery of drugs and genes in clinical applications. There are multiple factors affecting the delivery of drugs and genes to tumors. Factors such as blood flow, angiogenesis, microvessel density, interstitial pressure, macrophage activity, extracellular and intracellular components, and, most importantly, the physicochemical properties of the drug carrier play an important role in the transport of drugs and macromolecules to tumors. The accumulation of polymeric nanoparticles carrying drugs is dependent on the physical chemistry of the polymer, including molecular weight, surface charge, nature of the polymer.
