A novel process for coating of silica aerogel microspheres for controlled drug release applications

Aerogels are nanoporous materials with an open-pore structure and high specific surface area. Because of their outstanding properties they have been investigated in immense fields of applications like novel insulation materials, catalysts and catalysts carrier, optics, waste treatment and drug delivery systems. However, the limitation of aerogels (specially hydrophilic ones) in a number of applications is their open-pore structure, allowing the penetration of liquids therein resulting in destruction of their textural properties. Applying a polymeric coating layer on aerogels surface can be a solution for this problem and can open a wide window of new applications for aerogels, especially in pharmaceutical industry. This work suggests a novel process for coating of aerogels with polymeric materials using spouted bed technology. Firstly, spherical silica aerogel particles with a high surface area up to 1100 m(2)/g and particles diameter ranging from 200 mu m to few millimetres were produced. Then, the aerogel particles were loaded with a model drug (Ibuprofen) by adsorption from supercritical CO2 phase. The loaded aerogel particles were coated with different polymeric materials in a slit-shaped spouted fluidized bed with two horizontal gas inlets and adjustable gas supply. The corresponding polymers were sprayed as an aqueous suspension or as melts. The process conditions for coating (coating material, fluidization air flow rate, temperature, etc.) were optimized accordingly. The physical, mechanical, structural and release properties of the resulting formulations were evaluated. This technology allows to provide a specific release mechanism of pharmaceuticals (thermal, pH-sensitive or enzyme triggered release) from aerogels and to broaden aerogel applications in pharmaceutical technology. (C) 2012 Elsevier Inc. All rights reserved.