Heat-induced structural changes in lactoferrin for enhanced mucoadhesion

The development of biocompatible and safe mucoadhesive materials is critical for improving therapeutic strategies, where cationic proteins such as lactoferrin are emerging as promising alternatives to synthetic polymers. Here, we demonstrate how thermal denaturation of lactoferrin can be used as a viable strategy to enhance mucoadhesion. We identify and study in detail the structural changes in lactoferrin upon thermal denaturation using light scattering, circular dichroism spectroscopy, gel-electrophoresis, and atomic force microscopy. Lactoferrin-mucin binding was evaluated using rheology, confocal microscopy, and quartz crystal microbalance with dissipation monitoring. We find that lactoferrin binds to mucin at its native state, heat-treatment at 95 °C enhances its affinity for mucin, and that the adhesion mechanism relies on hydrophobic interactions with no obvious contributions of disulfide bonds. Lactoferrin and its resulting complexes with mucin present high surface activity, which induces an artificial shear-thinning rheological response. While electrostatic interactions have been considered the dominant mucoadhesive mechanism of native lactoferrin up to now, our findings highlight the role of hydrophobic interactions, providing a design route to alter the structural state of the protein to inspire the development of future natural protein-based mucoadhesive systems.