Biomimetic sol-gel mineralization of polysaccharides by silicon and titanium polyolates

Abstract

In this work, we have demonstrated that in addition to silicon tetraglycerolate, a new water-soluble biocompatible polyolate precursors – silicon tetrapolyethylene glycolate Si[O(CH2CH2O)nH]4 [5, 6] and titanium tetrapolyethylene glycolate Ti[O(CH2CH2O)nH]4 [5] – can be successfully utilized in biomimetical mineralization of polysaccharides of various nature. By the example of chitosan (cationic), xanthan gum (anionic), and hydroxyethyl cellulose (uncharged) polysaccharides, an accelerating effect has been demonstrated on the gelation process and a stabilizing effect has been revealed on the hydrogels formed as transparent monoliths showing resistance to syneresis. Thus formed silicon- and titanium-containing 3D-network of gels is found to be polymeric and appears to have ordered amorphous morphostructure, which can be explained as caused by the influence from the polysaccharides serving as templates. The presence of polyolate bridges between silicon or titanium atoms in the polymeric network is characteristic of polyolate precursors only and is determined mainly by the nature of the precursor and by the contents of polyol and water in the system. The formation of polyolate bridges is facilitated by the low reactivity of the precursor, by low water content, and also by polyol excess in the system. The sol-gel process utilized to obtain the silicon- and titanium-polysaccharide-containing hydrogels proceeds under the mild conditions at room temperature, with no catalyst or any organic solved to be used, and thus can be regarded as belonging to the green chemistry methods that show promise for biomedical materials applications.