Nano-immunotherapy: Unique mechanisms of nanomaterials in synergizing cancer immunotherapy

•Biomaterials can be used in nano-immunotherapy to overcome current Achilles’ heel of cancer immunotherapy.•Nanomaterials can be used for immuno-bioimaging and deliver immune modulating agents to the host and tumor microenvironment.•Nanomaterials can be used for immunity elicitation and CTL activity promotion in tumor microenvironment.•Combination of nanomedicine and immunotherapy will provide synergistic efficacy for effectively treating various cancers.