## 4 Nanodelivery Platform for Vaccine
### Polymeric Nanocarriers
Significant immune infiltration was detected in mice after vaccination with a vaccine loaded with breast cancer neoantigen, inducing specific T cell immune responses and humoral immunity [68]. Chitosan nanoparticle vaccines loaded with whole tumor cell lysates have also been found to target specific DCs, and in vivo studies in mice have found that the nanoc vaccines can be taken up by endogenous DCs, eliciting cellular immune responses [143]. Overall, these studies have illustrated the ability of polymeric nanoparticles to serve as a self-assembling, excellently flexible, and highly efficient delivery platform for new antigenic vaccines with advantages such as lysosomal escape, targeting of LNs, uptake by APCs, and enhancement of cellular immune responses. Polymeric materials can also be delivered in the form of depots: hydrogels, microcapsules, microneedles, etc. A hydrogel is defined as a 3D network based on polymer chains [144], which has some degree of similarity to biological tissues, and has a broad range of applications in wound recovery and drug/antigen delivery. [PERSON] et al. found that implanting a hydrogel vaccine (PancVax) with pancreatic cancer neoantigens into the PDAC resection site exerted a long-lasting effect, inducing immune infiltration and immune cell mass activation, preventing tumor recurrence while promoting wound healing [98]. This is a new approach to the prevention of tumor recurrence and improvement of prognosis in the clinic. The idea of using a rich variety of nanoparticles in combination with hydrogels to solve the problem of limited types of hydrogel-loaded substances has aroused extensive attention. A thermosensitive hydrogel carrying black phosphorus quantum dot nanovesicles (BPQD-CCNVs) encapsulating tumor cell membranes was prepared by [PERSON] et al., containing lipopolysaccharide-acrylamide (LPS) and granulocyte-macrophage colony-stimulating factor (GM-CSF). This personalized photo-thermal hydrogel vaccine has both the slow-release effect of the hydrogel and the local recruitment and antitumor effect of the BPQD-CCNVs nanoparticles, which avoids repeated injections and improves the uptake of the vaccine [82]. Additionally, hydrogels (Gel) containing bacterial-derived vesicles loaded with neoantigens and GM-CSF can continuously recruit DCs [145]. A PDT-driven autologous tumor cell vaccine (P-ATV) coated by PEI-Ce6 with a Fmoc-KCRGDK-phenylboronicacid (FK-PBA) hydrogel targeted tumor cells that overexpress sialic acid, and the gel was injected serially on demand in the area of residual tumor [80]. Unlike hydrophilic hydrogels, microcapsules can be loaded with diverse substances, building a plentiful antigen library. [PERSON] reported a self-healing microcapsule capable of carrying protein/peptide chains, which modulates the immune microenvironment in situ, effectively loading antigen molecules into macroporous microspheres based on polylactic acid (PLA) and poly(ethylene glycol)-b-poly-dl-lactide (PELA) to form a sustained release antigen library, promoting the uptake and cross-presentation of the antigen and recruitment and activation of APCs [146]. In addition, polymeric microneedle vaccines based on transdermal delivery have been explored, for instance, biodegradable microneedles (bMNs) based on PEG- and PSMEU-carrying DNA vaccines can elicit specific humoral immune responses and continuously release and inhibit lung metastasis [147]. Another is a patch of B16F10 whole tumor lysates loaded into a polymer microneedle that releases the lysates continuously for 5 days after insertion into the skin, and under NIR light irradiation, the patch's self-contained melanin produces heat, which promotes the uptake of antigens by DCs and enhances antitumor vaccination [148].