Emerging biodegradable nanomaterials for innovative tumor immunotherapy.

Immunotherapy has rapidly emerged as the new pillar of cancer treatment alongside surgery, radiotherapy and chemotherapy. However, existing immunotherapeutic approaches face significant limitations such as inefficient tumor-targeted drug delivery, poor cellular internalization and off-target effects, all of which lead to suboptimal therapeutic outcomes. Recent advances in nanotechnology have introduced nanomedicines as a promising solution to these challenges, which can precisely deliver immunomodulators, enhance antigen presentation, and increase T-cell infiltration as well as improve their targeting and safety, and thus powerfully enhance the therapeutic effect of tumor immunotherapy. Among numerous types of nanomedicines, biodegradable nanomaterials have recently received extensive attention for tumor immunotherapy due to their unique advantages including biodegradability, simple and cost-effective synthesis, and use of renewable resources, aligning with environmental and sustainable development goals. More importantly, many biodegradable nanomedicine platforms, such as liposomes, polymeric micelles and polymeric nanoparticles, have already entered clinical trials or received approval. Thus, the biodegradable nanomaterials exhibit promising potential for tumor immunotherapy. However, comprehensive reviews systematically summarizing the application of biodegradable nanomaterials for tumor immunotherapy are still rare. Herein, this review provides a detailed introduction to this field. Firstly, the general types of biodegradable nanomaterials for tumor immunotherapy are introduced. Secondly, the common mechanisms of tumor immunotherapy are elucidated. Thirdly, the basic research applications of biodegradable nanomedicine-mediated tumor immunotherapy are emphasized. Next, the clinical transformation prospects of biodegradable nanomaterials for tumor immunotherapy are highlighted. Furthermore, the potential impacts of degradation behaviors on the immune microenvironment are pointed out. Finally, the challenges and future outlooks are discussed.