Supramolecular assembly of cholesterol-conjugated mannan and polyethylenimine into polyplex micelle: a potential biocompatible vaccine adjuvant platform

The development of potent subunit vaccines requires adjuvant systems capable of eliciting robust cellular (Th1) immunity while maintaining high biocompatibility. Herein, We engineered a novel "safety-by-design" nanoadjuvant platform via the supramolecular co-assembly of cholesteryl-conjugated Mannan (MN-CLS) and cholesteryl-conjugated branched polyethylenimine (BPEI-CLS). This design induced the spontaneous formation of polyplex micelles driven by a "dual-lock" mechanism: electrostatic attraction between the cationic BPEI and anionic Mannan, reinforced by hydrophobic associations between cholesterol domains. Structural characterization (1H-NMR, FT-IR) confirmed successful synthesis, and the resulting micelles exhibited superior thermodynamic stability with a significantly reduced Critical Micelle Concentration (CMC). FRET and DLS analyses verified a unified core-shell architecture of approximately 200 nm, which is suitable for APC-mediated cellular uptake and subsequent lymph node delivery. Crucially, in vitro assays demonstrated that MN-CLS/CLS-BPEI micelles significantly reduced cytotoxicity compared to native BPEI and BPEI-CLS while maintaining colloidal stability. This platform is expected to effectively synergizes the receptor-targeting specificity of Mannan with the immunostimulatory potential of BPEI, presenting a promising, biocompatible adjuvant system for next-generation vaccines.