Composite hydrogels as a vehicle for releasing drugs with a wide range of hydrophobicities

Many vitamins, bioactive lipids and over 40% of newly developed drugs are hydrophobic, and their poor water solubility limits their delivery using conventional formulations. In this work we investigated a composite gel system formulated from microemulsions embedded in alginate hydrogels, and showed that it is capable of loading several hydrophobic compounds with a wide range of aqueous solubility. All gels were clear, with no precipitations, indicating the solubility of the drugs in the gels. The release behavior was similar for different microemulsion formulations, various drugs and increasing concentrations of a drug. These findings indicate that our system could potentially act as a generic system, where the properties of the release do not depend on the drug but rather on the attributes of the gel. The structure of composite gels was investigated using small-angle scattering of X-rays and neutrons (SAXS and SANS, respectively). SANS showed more sensitivity to the structure of the microemulsion in the composite gel than SAXS did. SAXS and SANS plots of the composite gels show that both the droplets and the gel network preserve their structure when mixed together.