Cellular Uptake and Targeting

Tumor invasion, metastasis, and resistance to chemotherapeutic drugs and radiation are major obstacles for the successful treatment of cancer [65]. Some of these limitations can be overcome by therapeutic strategies that increase specificity and efficacy and at the same time reduce toxicity of the anticancer drugs. One of the approaches includes targeting the polymeric delivery systems specifically to the cancer cells. 

The targetability of polymeric forms of nanodelivery systems to cancer cells and tumors can be achieved by adopting either of the following two approaches (i) passive targeting and (ii) active targeting [66]. 

FIGURE 6.20 Schematic representation of (a) the EPR effect and (b) further cellular uptake mechanisms. Source Khandare et al. [68]. Reproduced with permission of Royal Society of Chemistry. See insert for color representation of the figure.) 

All of the earlier mentioned passive approaches for targeting the polymeric forms of nanodelivery systems can be utilized to enhance a tumor-specific delivery of drugs. However, these approaches are rarely used as the predominant methodologies in current cancer therapies. The preferred and more routinely employed technique involves an active targeting of the polymeric forms of nanodelivery systems. 

These and other observations clearly demonstrate that active targeting enhances the overall accumulation of a polymeric nanodelivery system by the cancer cells, thereby increasing the amount of the applied dose to actually penetrate the cancer cells. This may in turn lead to a substantial increase in the cytotoxicity of the drug and thus to a more effective anticancer activity. 

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