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Chemo-drug controlled-release strategies of nanocarrier in the development of cancer therapeutics.

Nanoparticles have been widely used in cancer therapy because of its nanoscale, high surface ratio, multifuntions and so on. With specific construction of nanoparticles, such as choosing magnetic nanomaterials or citric acid coated nanoparticle, scientists can kill tumor cells effectively and accurately，importantly， reducing the side effect of conventional chemotherapy. Currently, they have been continually applied in cancer therapeutics research. Scientists not only designed nanoparticles loading with therapeutic drugs, but also equipped with targeted molecules. These works make nanoparticles become a multifuntional nanocarrier. In the construction of multifunctional nanocarriers, nanoparticles play the important work of drug delivery. Normally, enabling drugs delivery to tumor tissues is a difficult task. During the period of internal circulation, it is hard to keep the nanocarriers stability. As well as not attach to normal cells or serum. With the application of stimulus-responsive nanomaterials, scientists develop many nanocarriers with controllable drug release. These controllable drug delivery systems can quickly respond to microenvironmental changes (PH, enzyme, etc.) or external stimuli (photo, heat, magnetic or electric fields). Thus, it is to overcome the side effects by controllable drug delivery systems in vivo. In this article, we summarize the various kinds of stimulus-responsive nanocarriers for cancer therapy and discuss its possibilities and challenges in future application.