6.5.6 The application of polymer nano-drug carrier...
Radiotherapy is a very effective treatment for cancer in clinic.Although it has been reported that some melanoma can tolerate radiation，it has also been reported that radiotherapy has a good therapeutic effect on melanoma.Radiotherapy uses radiation to destroy DNA in cells，making them unable to proliferate.However，how to reduce the side effects of radiotherapy and enhance the therapeutic effect are the key problems to be solved in radiotherapy.Radiotherapy can be divided into two categories：treating tumors by external radiation and injecting radioactive drugs into the body.For the external radiation therapy，elements with high atomic number（e.g.，gold，bismuth，and hafnium）can enhance the destruction effect of radiation by enhancing the scattering of radiation in the tumor area.For the injection of radioactive drugs，how to improve the tumor accumulation of drugs is the key to improve the therapeutic effect.Deng et al.synthesized the amphiphilic polymer by coupling PEG-b-poly（L-thyroxine）and radioactive iodine-131（131I）and assembled them into polymer nanomaterials.This kind of polymer nano-drug carrier containing radioactivity has a good tumor inhibition effect on melanoma.
In conclusion，polymer nano-drug carriers can enhance the therapeutic effect of chemotherapy，photothermal/photodynamic therapies，radiotherapy and other therapies of melanoma.The EPR effect is the basis for the design of most antitumor nano-drugs.Recently，there are some results suggesting that EPR effects may vary from tumors to tumors，patients to patients，and different tumor stages.At present，the bottleneck problems of tumor therapy of nano-drug lie in the limited tumor accumulation and therapeutic effect.In addition，the latest research results indicated that some nanomaterials may enter tumor tissues mainly through the trans-endocytosis process through the endothelial cells in tumor vascular walls，rather than through the leakiness in the vascular walls in the traditional EPR theory.These new results need to be further studied and confirmed，but the development of EPR theory also indicates that the current design strategies of polymer nanodrug delivery system need to be further improved.In addition，the toxic and side effects of polymer nano-drug carriers require further study.The development of polymer nano-drug carriers with good biocompatibility and biodegradability is also the direction that demands continuous investigation.(https://www.daowen.com)