Formulation and characterization of W/O nano-dispersions for bioactive delivery applications

Abstract: The main objective of this study was the formulation of food-grade water-in-oil (W/O) nano-dispersions based mainly on medium or long-chain triglycerides. Two types of dispersions were formulated and structurally compared, namely emulsions and microemulsions. The systems were used as matrices for encapsulating targeted bioactive molecules with specific characteristics such as antioxidants or peptides.The structural characterization of the formulated systems was investigated using techniques such as Electron Paramagnetic Resonance (EPR) spectroscopy, Dynamic Light Scattering (DLS), Cryogenic Transmission Electron Microscopy (Cryo-TEM) and Small Angle Xray Scattering (SAXS). The existence of swollen inverse micelles was revealed for the case of microemulsions whereas larger droplets still at the nano-scale were observed for the case of emulsions. Structural differences in the presence of the bioactive molecules or induced by the alteration of components were also observed.In order to study the efficacy of the formulations, the proposed loaded systems were assessed either using EPR spectroscopy or Well Diffusion Assay (WDA) depending on the bioactive molecule. It was found that the encapsulated molecules retained their claimed characteristics when encapsulated to the proposed matrices.Finally, some of the formulated dispersions were investigated for their behavior under gastrointestinal (GI) conditions. A two-step digestion model using recombinant Dog Gastric Lipase (rDGL) and Porcine Pancreatic Lipase (PPL) was proposed to simulate lipid hydrolysis in humans. The studies revealed significant decrease of the rDGL specific activity in the presence of the microemulsion while in the presence of lower percent of surfactants (case of emulsion) no alterations were observed.