Fig. 1: Schematic of PPSU-based hierarchical hydrogels that enable ratiometric loading of multiple adjuvants for vaccine optimization.

Hydrophobic adjuvants are encapsulated through network assembly of PPSU (1^st gelation). Water-soluble adjuvants are adsorbed during the formation of microgels triggered by bridging nanogels with the antigen OVA (2^nd gelation, only simple mixing steps that take less than 5 min before injection). Microgels anchor onto collagens upon subcutaneous injection (3^rd gelation), allowing sustained release. Within the first 24 h after vaccination, Th1/Th2 cytokine levels increased. By day 7, anti-OVA IgM antibodies had risen, and over the subsequent four days, the vaccination effectively promoted the proliferation of adoptively transferred antigen-specific T cells. Anti-OVA IgG2b and IgG2c responses remained significantly elevated for up to one month, while significant levels of anti-OVA IgG1 antibodies persisted through day 84. Following a prime-boost administration on day 90 and a subsequent 15-day period, marked increases in neutrophils, CD11b⁺ conventional dendritic cells (cDCs), and B cells were observed.