Sponges carrying self-microemulsifying drug delivery systems

Abstract

Self-microemulsifying drug delivery systems (SMEDDS) increase the solubility of lipophilic drugs. One barrier to their wide application is their liquid nature. We report on a new method to solidify SMEDDS-their incorporation in sponges made from a hydrophilic natural polymer. Using different freeze-drying schemes, sponges were prepared from alginate gels containing microemulsions. The sponges' structures were studied with scanning electron microscopy and small angle X-ray scattering. The oil droplets survived the drying process, and SMEDDS were present as 9 nm-sized objects in the dried sponges. The sponges were rehydrated in water, and evidence of the presence of SMEDDS in the rehydrated sponges was found. A model hydrophobic molecule, Nile red, was soluble in all dry and rehydrated sponges. SMEDDS containing Nile red were gradually released from the sponges, at a rate that depended on the drying method. The equilibrium water uptake of the sponges was also found to be influenced by the drying scheme. The combination of SMEDDS and sponges may be a way to overcome the disadvantages of each component separately, provide a solid dosage form for SMEDDS that can sustain the release of drugs and also enable utilization of hydrophilic sponges for the delivery of hydrophobic drugs.