Inorganic surface chemistry and nanostructure controls lipolytic product speciation and partitioning during the digestion of inorganic-lipid hybrid particles.

Hypothesis: Solid-state lipid formulations, whereby liquid lipids are encapsulated in inorganic particle matrices, have attracted significant interest for drug/nutrient delivery in recent years. We hypothesized that the surface chemistry of the inorganic material used to encapsulate lipids impacts the lipase-mediated digestion and partitioning of lipolytic species between the solubilized aqueous and insoluble pellet phases.

Experiments: Medium chain triglycerides were spray dried with silica nanoparticles, montmorillonite or laponite platelets to form inorganic-lipid hybrid particles. In vitro lipolysis studies were conducted under gastric (pH 1.6) and intestinal (pH 7.5) conditions, and the speciation and partitioning of lipolytic products between the aqueous and pellet phases was characterized using solution-state proton nuclear magnetic resonance and fourier transform infrared spectroscopy.

Findings: Under gastric conditions, greater than 80% of all lipid species remained adsorbed within each lipolysis pellet after 60 min. Approximately 40%, 50-60% and 80-90% of all lipid species were adsorbed from solution by silica-, montmorillonite- and laponite-based particle matrices during intestinal lipolysis. Monoglycerides were preferentially adsorbed by silica, whereas triglycerides and fatty acids were adsorbed by montmorillonite and laponite. Adsorption of lipolytic products from solution is expected to impact significantly on drug/nutrient solubilization and absorption in vivo. To the best of our knowledge, this is the first report characterizing the speciation and phase behavior of lipolytic products released from solid-state lipid formulations during in vitro lipolysis studies.