CONCLUSION AND PERSPECTIVE
Immunotherapy is an essential approach to cancer treatment that has high specificity, long-term efficacy, reduces a large intake of drugs, and provides less invasive treatment than traditional therapies. Due to special properties or conjugation with different adjuvants, CDs are developed to inspire immune response which can be a novel approach to clinical application in tumor immunotherapy. In this review, we summarize and discuss the current application of CDs in tumor immunotherapy, including vaccines, immunoadjuvants, and synergistic therapy with PDT/PTT/CDT. In general, depending on the recent progress of CD good absorption in NIR and high ROS generation caused by CDs surface electronic transitions under light irradiation, it is rational for CDs to act as important tools in targeted tumor PDT/PTT. Further, smaller particle size, variable surface structure, and easy cell internalization make CDs become great vehicles for the delivery of chemotherapeutics, such as doxorubicin and platinum drugs. Nevertheless, it is often difficult to get the ideal long-term therapeutic effect with monotherapy. To address this, current studies on tumor therapy by using CDs are moving toward the synergistic use of multiple treatments, especially combined with immunotherapy. By ingenious design, CDs are able to elicit an anti-tumor immune response while performing PDT/PTT/CDT. On the other side, CDs, as presented, are directly used in tumor immunotherapy, namely, as vaccines or immunoadjuvants. Although the application of CDs in vaccines and immunoadjuvants is still in its infancy, high biocompatibility and various functional surface groups help CDs to stimulate the tumor immune response and transform the low immunogenic “cold tumors” into the high immunogenic “hot tumors”. In addition, CDs are explored to combine with tumor antigen models, such as OVA, to perform the dual role of immunoadjuvant and vaccine in tumor therapy.
However, there are also many challenges and clinical translation concerns of CDs in tumor immunotherapy. Firstly, the pharmacokinetic changes of CDs in vivo , especially the structure and functional group changes of CDs are unclear. Clinical application is often holding a cautious attitude to unclear medicines. Secondly, although most CDs have lower toxicity and better clearance efficiency in vivo , the information related to long-term toxicity remains missing since cancer treatment is a long and cumulative process. Thirdly, the current efficiency of CDs in immunotherapy has yet to be improved. Enhancing targeting and reducing side effects are long-term questions of CDs in immunotherapy. Last but not least, the applications of CDs in tumor immunotherapy are still in the earlier stages and the therapeutic experiments are mainly conducted in rodents. Further studies are needed to translate the results obtained in animal models into human applications. Collectively, CDs have made remarkable progress in tumor immunotherapy. The applications of CDs so far are very promising in tumor immunotherapy. CDs can play a role in directing immune response, but further investigation is essential to explore their full potential and revolutionize the future of medicine.