Preparation, characterization, and antimicrobial activity of cubosome encapsulated metal nanocrystals.

Herein, we demonstrate a method for the functionalization of cubic phase lipid nanoparticles (cubosomes) with a series of magnetite (Fe3O4), copper oxide (Cu2O), and silver (Ag) nanocrystals, with prospective applications across a wide range of fields, including antimicrobial treatments. The resulting cubosomes are characterized using small-angle X-ray scattering and dynamic light scattering, demonstrating retention of typical cubic phase structure and particle size subsequent to nanocrystal encapsulation at concentrations up to 20% w/w. Cryogenic transmission electron microscopy reveals significant loading and association of each nanocrystal type with both monoolein and phytantriol based cubosomes. The antibiotic potential of these hybrid nanoparticles is demonstrated for the first time; cubosomes with embedded silver nanocrystals display a high level of antimicrobial activity against both Gram-positive and Gram-negative bacteria, with observed MIC values ranging 15.625-250 µg/mL. Lastly, total internal reflection fluorescence (TIRF) microscopy is used to visualize cubosome-bacteria interactions, suggesting the involvement of particle interaction as a delivery mechanism.