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The toolbox of designing nanoparticles for tumors.

Nanoparticles (NPs) show great promise in the treatment of a wide range of diseases, which provides advantages and offers a new prospect for tumor detection, prevention and treatment. In order to eradicate the cancer cell, the NPs need to flow to different regions of tumors via blood vessels, and then penetrate through the interstitial space to reach the target cells. However, the environment and physiological characteristics in tumor tissues are different from that in normal ones, mainly in the irregular blood vessels, the lack of lymphatic network, low pH, hypoxia, immune function and so on. Meanwhile, the differences also exist among different tumor tissues. To achieve the optimal therapeutic effect, the NPs should be carefully designed by considering the therapeutic application, the target site and the route of administration. This review shows a variety of barriers in the tumor tissues, and provides a toolbox of designing the NPs for tumor treatment. In particular, the particle size, shape and surface chemistry, and the NPs in preclinical and clinical stage use have been discussed.