In recent years immunotherapy has been developed as a promising oncotherapy strategy after surgery, chemotherapy and radiotherapy. Immunotherapy has been widely used in the treatment of cancer including a variety of approaches. It is interesting that the overall efficiency of therapeutic cancer vaccines can be greatly improved when nanoparticle-based adjuvants are used. Significant efforts have been made to synthesize diverse nanoparticles which can fundamentally achieve surface modification and functionalization. In this review, we introduce the role of multifunctional nanoparticle-based adjuvants used in cancer vaccines, particularly focusing on synthesis methods of different types of nanoparticles and therapeutic effects of vaccines. In addition, some new ideas about nanotechnology used in cancer immunotherapy are summarized. Finally, the preliminary analysis and perspective on applying nanotechnology to overcoming the challenges of cancer vaccines are presented.

Contents
1 Introduction
2 Multifunctional nanoparticle-based adjuvants in cancer vaccines
2.1 Protection and controlled release of antigens
2.2 Co-delivery of antigens and immunopotentiators to the same APC
2.3 Immunostimulatory characteristic
2.4 Targeting draining lymph nodes
2.5 Formation of cross-presentation
3 New ideas on nanotechnology used in cancer vaccines
3.1 Self-assembled DNA nanostructures
3.2 Nanoscale artificial antigen presenting cells
3.3 Cancer cell membrane-coated nanoparticles
3.4 Multifunctional nanorods
3.5 Multifunctional Fe₃O₄-CdSe/ZnS nanoclusters
3.6 Chitosan-coated hollow copper sulfide nanoparticles
4 The influence of administration route on immune response
5 The dilemma of cancer vaccines
6 Outlook