The disclosure provides compositions and methods of use of formulations effective for the delivery of biologically active molecules and materials, including therapeutic and diagnostic agents, and combinations thereof, to cells, tissues, and living organisms. More particularly, the present invention is related to the incorporation of hydrophobic nanoparticles, such as hydrophobic metal nanoparticles, into the membranes of vesicular delivery vehicles. These hydrophobic nanoparticles enhance the endosomal membrane fusogenicity of the formulations through the promotion of inverted hexagonal phase formation in the lipid bilayers of the vesicular delivery vehicles. As a result, the vesicular delivery vehicles more readily fuse with the endosomal membranes, leading to enhanced endosomal escape of the vesicular delivery vehicle and its contents, thereby facilitating the delivery of the biologically active molecules and materials incorporated within the vesicular delivery vehicles to their sites of action.