Design and characterization of antibiotic-free lyotropic liquid crystalline coatings based on binary docosahexaenoic acid monoglyceride/glycerol monooleate systems for combating orthopedic implant-associated infections

There is a growing interest in innovative strategies for effectively preventing implant-associated bacterial infections. Here, we report on a simple-by-design approach for production of antibacterial coatings from docosahexaenoic acid monoacylglycerol (MAG-DHA) and glycerol monooleate (GMO). In addition to its amphiphilic nature, MAG-DHA is a safe precursor of docosahexaenoic acid (DHA) and has different beneficial health effects, including antibacterial activities. Using binary combinations of MAG-DHA and GMO, we describe the structural features and the antibacterial activities of antibiotic-free non-lamellar liquid crystalline (LLC) coatings. Small-angle X-ray scattering (SAXS) and in situ grazing incidence small-angle X-ray scattering (GISAXS) were employed to gain insight into the structural features of the fully hydrated coatings and the hydration-induced dynamic self-assembly of MAG-DHA and GMO on model implants. In a lipid composition-dependent manner, SAXS results revealed hydration-induced formation of different inverse LLC self-assemblies, including hexagonal (H₂) and bicontinuous cubic (Q₂) phases. Further, GISAXS analysis showed that lipid composition and employed relative humidity level play important roles in controlling the out-of-equilibrium self-assembly properties. Moreover, the coatings containing MAG-DHA displayed unique inherent antibacterial activities against Staphylococcus aureus and Staphylococcus epidermidis strains. This study describes the first antibiotic-free coatings with nanostructural architectures and inherent antibacterial activities for orthopedic implants.