The relationship between the chemical structure, physicochemical properties, and mucosal adjuvanticity of sugar-based surfactants

The relationship between the chemical structure, physicochemical properties, and mucosal adjuvanticity of sugar-based surfactants (SBSs) has not been sufficiently elucidated. Thus, in the present study, we systematically analyzed 11 SBSs for mucosal adjuvanticity. Ovalbumin (OVA)-specific antibody titers were measured in mice immunized intranasally with OVA plus SBS. We found that four SBSs (trehalose monododecanoate, sucrose monododecanoate, n-dodecyl-α-d-maltopyranoside, and n-dodecyl-β-d-maltopyranoside) exhibited the most potent adjuvanticity. We identified the following associations between chemical structure and adjuvanticity: 1) OVA-specific antibody titer increased with an increasing number of carbon atoms in the alkyl chain; 2) the adjuvanticity was not affected by the type of sugar or bond between the sugar and alkyl chain; and 3) SBSs with rigid structures exhibited less adjuvanticity. The relationship between physicochemical properties and adjuvanticity was as follows: 1) SBSs exhibited adjuvanticity above the critical micelle concentration and 2) in the SBSs with potent adjuvanticity, the diameter of the SBS-OVA complex was 70–75 nm. Our study indicates evidence for the direct involvement of chemical structure and physicochemical properties in determining adjuvanticity in SBSs.