In vitro drug release studies from organoclay/poly(dimethyl siloxane) nanocomposite matrices

Silicone elastomers are versatile biomaterials and have been used for fabrication of drug release systems, usually incorporating lipophilic drugs. However, attempts have been made to extend the use of these biomaterials to the delivery of hydrophilic drugs. Furthermore, the need to improve mechanical properties of silicones led, among others, to the incorporation of organoclay nanoparticles and, therefore, has introduced some new parameters to be investigated regarding their effect on the release profile. In this work, the delivery of 2-methyl-5-nitroimidazole-1-ethanol (metronidazole) from nanocomposites with silicone matrix based on condensation cured elastomers with different molecular weights was investigated in various surrounding liquids. The results showed that incorporation of organic modified montmorillonite (OMMT) generally decreases the drug release rate and restricts the initial burst effect. Interestingly, OMMT concentrations of 2 phr in low MW silicone systems seem to enhance drug release and, independently of interpretation, it might indicate a route for the adjustment of diffusivity through the nanoclay concentration. Maximum drug release rates can rather be achieved with low MW PDMS than with the higher MW elastomers.