Non-covalent Lysine–docosahexaenoic acid amphiphilic complexes as interfacial stabilizers for emulsions and lutein delivery

Non-covalent amphiphilic complexes offer potential as interfacial stabilizers in emulsion-based delivery systems. However, the relationship between their molecular composition, interfacial assembly, and emulsion performance remains inadequately understood. Lysine–docosahexaenoic acid (Lys-DHA) complexes with varying mass ratios were synthesized to investigate how the Lys/DHA ratio influences oil–water interfacial behavior and lutein delivery. Analytical techniques and computational simulations revealed that Lys and DHA interacted through electrostatic forces, hydrogen bonding, and van der Waals interactions. Higher DHA content increased hydrophobic exposure and facilitated interfacial adsorption. The Lys-DHA (1:3) complex exhibited optimal interfacial properties, characterized by the lowest interfacial tension, highest surface pressure, fastest diffusion rate, and a predominantly elastic interfacial film. Emulsions stabilized by Lys-DHA (1:3) displayed smaller droplet sizes, lower ζ-potential, and more excellent physical stability, with an average droplet size of 317.97 nm and ζ-potential of −51.37 mV. Regarding lutein delivery, these emulsions achieved encapsulation efficiencies exceeding 80%, retained over 70% of lutein after 14 d, and enhanced lutein bioaccessibility to 44.9%. These results highlight the potential of Lys-DHA complexes as functional lipid-containing amphiphilic interfacial stabilizers, offering insights into the correlation between non-covalent molecular interactions and interfacial/emulsion characteristics.