Background: Recently, cancer immunotherapy has become standard for cancer treatment. Immunotherapy not only treats primary tumors, but also prevents metastasis and recurrence, representing a major advantage over conventional cancer treatments. However, existing cancer immunotherapies have limited clinical benefits because cancer antigens are often not effectively delivered to immune cells. Furthermore, unlike lymphoma, solid tumors evade anti-cancer immunity by forming an immune-suppressive tumor microenvironment (TME). One approach for overcoming these limitations of cancer immunotherapy involves nanoparticles based on biomaterials. Main body: Here, we review in detail recent trends in the use of nanoparticles in cancer immunotherapy. First, to illustrate the unmet needs for nanoparticles in this field, we describe the mechanisms underlying cancer immunotherapy. We then explain the role of nanoparticles in the delivery of cancer antigens and adjuvants. Next, we discuss how nanoparticles can be helpful within the immune-suppressive TME. Finally, we summarize current and future uses of nanoparticles with image-guided interventional techniques in cancer immunotherapy. Conclusion: Recently developed approaches for using nanoparticles in cancer immunotherapy have enormous potential for improving cancer treatment. Cancer immunotherapy based on nanoparticles is anticipated not only to overcome the limitations of existing immunotherapy, but also to generate synergistic effects via cooperation between nanoparticles and immune cells.

Hyaluronic acid (HA)–graphene oxide (GO) conjugates, with a high loading of photosensitizers (PS; Ce6), were developed as a cancer cell targeted and photoactivity switchable nanoplatform for photodynamic therapy (PDT). HA–GO conjugates with size below 100 nm were first prepared by the chemical conjugation between ADH-modified HA and fractionated GO sheets with size relevant for drug delivery. Before evaluating the drug delivery efficacies, their chemical structure, morphology, and biocompatibility were characterized by ¹H NMR, UV, TGA, AFM, DLS and MTT assays. The physical adsorption of Ce6 onto HA–GO nanocarriers was mainly due to the π–π stacking as well as hydrophobic interactions. It was demonstrated by CLSM and FACS that the cellular internalization of the HA–GO/Ce6 nanohybrids was much more effective when compared with free Ce6, which was also found to be significantly influenced by the co-treatment with an excess amount of HA polymers, illustrating their active targeting to HA receptors overexpressed on cancer cells. The photoactivity of Ce6 adsorbed on HA–GO nanocarriers was mostly quenched in aqueous solution to ensure biocompatibility, but was quickly recovered after the release of Ce6 from HA–GO nanocarriers upon cellular uptake. As a result, the PDT efficiency of the HA–GO/Ce6 nanohybrids was remarkably improved ∼10 times more than that of free Ce6, as well demonstrated in both MTT and LIVE/DEAD assays.