Poly(Vinylpyrollidone)- and Selenocysteine-Modified Bi Se Nanoparticles Enhance Radiotherapy Efficacy in Tumors and Promote Radioprotection in Normal Tissues.

The development of a new generation of nanoscaled radiosensitizers that can not only enhance radiosensitization of tumor tissues, but also increase radioresistance of healthy tissue is highly desirable, but remains a great challenge. Here, this paper reports a new versatile theranostics based on poly(vinylpyrollidone)- and selenocysteine-modified Bi Se nanoparicles (PVP-Bi Se @Sec NPs) for simultaneously enhancing radiotherapeutic effects and reducing the side-effects of radiation. The as-prepared nanoparticles exhibit significantly enhanced free-radical generation upon X-ray radiation, and remarkable photothermal effects under 808 nm NIR laser irradiation because of their strong X-ray attenuation ability and high NIR absorption capability. Moreover, these PVP-Bi Se @Sec NPs are biodegradable. In vivo, part of selenium can be released from NPs and enter the blood circulation system, which can enhance the immune function and reduce the side-effects of radiation in the whole body. As a consequence, improved superoxide dismutase and glutathione peroxidase activities, promoted secretion of cytokines, increased number of white blood cell, and reduced marrow DNA suppression are found after radiation treatment in vivo. Moreover, there is no significant in vitro and in vivo toxicity of PVP-Bi Se @Sec NPs during the treatment, which demonstrates that PVP-Bi Se @Sec NPs have good biocompatibility.