Considerations about 3-glycidoxypropyltrimethoxysilane reactivity in function of the complexity of aqueous and plasma gel media

Abstract

Organosilanes are versatile reactants for the chemical modification of silicas and organic polymers. The objective of this work is to evaluate the organic–inorganic reactivity of 3-glycidoxypropyltrimethoxysilane on aqueous media in the presence of a glutamic-like nucleophile residue and on protein gels. This is made by the combination of computational, spectroscopic, and thermal methods. Correlations are found between the in-silico results, calculated with Density Functional Theory, and sol-gel chemistry of 3-glycidoxypropyltrimethoxysilane in water. They explain the prevalence of esterification reaction with glutamic-like residue over hydrolysis of methoxy groups and epoxy ring of this molecule. This esterification contributes to the obtention of crosslinked gels when this organosilane is added to the blood plasma at concentrations higher than 75 mM at neutral pH. On the other hand, the prehydrolyzed molecule under acidic conditions is less reactive toward nucleophiles, and the silanol and diol groups act as a plasticizer on the gels. This in conjunction with non-extensive condensation in the protein media, shown by 29Si NMR spectroscopy, allows the identification of oligomers and silsesquioxanes on these samples. In summary, this kind of reactivity study contributes to overcoming the challenges of rationalizing organosilane chemical reactions, and effects in the gelation of proteins from complex sources.