Surface coating of l-glutamine solid microparticles for enteric delivery

The objective of this work was to produce enteric delivery systems to minimize gastric degradation of bioactives, using l-glutamine microparticles as a model, by surface-coating with a layer of enteric polymer (hydroxypropyl methylcellulose phthalate). Suspensions of solid glutamine microparticles in a methanol solution with enteric polymer and different concentrations of plasticizer (glycerol or triethyl citrate) and medium chain fatty acids (MCFA) were spray-dried at 55 °C. Spray-dried powders were characterized for in vitro release kinetics in simulated gastric (pH 1.2) and intestinal (pH 6.8) fluids at 37 °C. At a MCFA:polymer mass ratio of 2:1, formulations with plasticizer used at 30% of polymer mass resulted in <30% glutamine release after 2 h and <40% after 4 h at pH 1.2. At pH 6.8, complete release of glutamine was observed for most samples after 4 h. Our work demonstrated a simple approach for enteric delivery of food and pharmaceutical compounds.

► Reshaping glutamine crystals by spray drying produced spheres with little crystallinity.
► Coating was obtained by spray drying glutamine spheres suspended in enteric polymer solution.
► With addition of medium chain fatty acids, glutamine release at gastric pH was minimized.
► Plasticizer glycerol or triethyl citrate was important to the enteric delivery system.
► Most samples showed complete release at the intestinal pH, without the use of lipase.