Aqueous sol-gel routes to bio-composite capsules and gels

Due to their solvent-free chemistry and low environmental impact, aqueous silicates appear as promising alternative precursors to silicon alkoxides for the development of a greener sol-gel process. In this context, aqueous routes to silica/biopolymer composite materials are described here, allowing the formation of silica-coated agarose capsules and hybrid silica/carboxymethyl-cellulose hybrid gels. Infra-red spectroscopy and thermogravimetric analyses suggest that the silica-polymer interface is controlled by hydrogen bond formation. In addition, scanning electron microscopy suggests limited modi. cation of the agarose surface and of carboxymethylcellulose network organization. However, the presence of silica has a significant impact on the release of rhodamine B, a cationic dye, from the biocomposites. These materials not only comply with several requirements of Green Chemistry but also open new perspectives in the field of hybrid drug carrier design and plant silicification mimicry.