Biocompatible Sol−Gel Route for Encapsulation of Living Bacteria in Organically Modified Silica Matrixes

An alcohol-free sol−gel route based on the controlled vacuum evaporation of the alcohol that results as a byproduct of the hydrolysis and condensation of alkoxyde precursors is described for the encapsulation of living bacteria. The ability of the encapsulated cells (a genetically engineered E. coli strain) to express a fluorescent protein in response to the presence of dicyclopropyl ketone has been used to study both the biocompatibility of the encapsulation route and the viability of the encapsulated cells with aging time. Thus, up to 95% of the integrity of the living cell along the encapsulation process has been preserved through alcohol removal of the starting sol. In addition, the use of organically modified rather than pure silica gels as the host matrix has shown a notable improvement in the viability of encapsulated cells (18 versus 6 days, respectively).