Spray congealing as a microencapsulation technique to develop modified-release ibuprofen solid lipid microparticles: the effect of matrix type, polymeric additives and drug-matrix miscibility.

This study aimed to achieve modified-release of ibuprofen (IBU) by encapsulation within lipid-based matrix materials [cetyl alcohol (CA), stearic acid (SA) and glyceryl dibehenate (GB)] using spray congealing to produce solid lipid microparticles (SLMs). Polymeric additives, polyvinyl-2-pyrrolidone-vinyl-acetate and ethylcellulose, were employed as release-modifying agents. Spray-congealed SLMs yield, scanning electron microscopy (SEM)-based morphology, particle size, drug content and entrapment efficiency were investigated. The influence of matrix type, additive type and concentration and drug-matrix miscibility on release of IBU was elucidated. Yields (81.4-96.4%) and drug encapsulation efficiencies (88.4-100%) of SLMs were high for all formulations. SLMs were generally discrete, spherical and dense. Increasing additives concentration led to not only larger median size SLMs but also faster drug release due to increased hydrophilicity conferred by the additives. Solid solution systems (SA-IBU, GB-IBU) sustained the release of IBU better than solid dispersion system (CA-IBU). CA- and GB-based SLMs closely adhered to the Weibull model of drug release, while SA counterparts followed the Korsmeyer-Peppas model.