Hydrophobic ion pairing as a rational surface engineering strategy for enhanced protein integration within lipid-based nanocarriers

Although promising for enhancing lipophilicity, its influence on protein stability, activity, and interactions with lipids remains unclear at the molecular level. In this study, lysozyme was used as a model protein, and ion paired with two surfactants, sodium dodecyl sulphate (SDS) and dioctyl sodium sulfosuccinate (DOSS).

The impact of surfactant complexation on lysozyme solubility, activity, and structure was investigated at various charge ratios. An up-to-2-fold increase in lysozyme catalytic activity was observed alongside enhanced lipophilicity upon complexation with SDS at sub-stoichiometric ratios, suggesting that favourable conformational changes, driven by partial protein unfolding, led to higher substrate accessibility. To understand the mechanism of protein release for downstream formulation design, an ion exchange chromatography method was developed and validated using the ÄKTA start fast protein liquid chromatography system for accurate quantification of lysozyme–surfactant complexes dissociation as a function of pH, ionic strength, and simulated intestinal fluid components, with lysozyme–SDS complex showing greater susceptibility to dissociation.