Targeted Drug Delivery to Cancer Stem Cells through Nanotechnological Approaches

Cancer Stem Cells (CSCs) are responsible for tumor development, invasion and metastasis and resistance to chemotherapy and radiotherapy. Therefore, treatment strategies have turned to targeting CSCs, and utilizing nanotechnological approaches to target CSCs has become increasingly fascinating. Functionalized nanoparticles (NPs), such as metallic NPs, liposomes, polymeric NPs, albumin microspheres and nanomicelles, can easily cross the cytoplasmic membrane and accumulate at their targets to continuously release therapeutic agents in response to the characteristics of the tumor microenvironment. Different kinds of NPs possess different characteristics. Inducing immune responses might be the disadvantage they commonly owned through the summary and analysis of these NPs. For natural polymers, they have many attractive properties, but deficiencies also exist such as poor water-solubility, high viscosity, high permeability, etc. The drug-encapsulated NPs launched in the market and those in the clinical trials exhibit a bright prospect in cancer targeted therapy. In addition, the application of nanodiagnostic techniques, such as nanocantilever and DNA microarray technology and early cancer detection has become an indispensable component in clinical practice to improve in vivo detection and enhance targeting efficiency. This review mainly determines the species and usages of NPs in drug delivery and disease diagnosis, the delivery mechanisms of NPs, the main factors that affect nanomedicine efficiency and toxicity and the further trends in the development of targeted therapy. Nevertheless, more and deeper investigations are still needed to avert potential adverse effects and improve the delivery efficiency to achieve better therapeutic effects.