Improving silica matrices for encapsulation of Escherichiacoli using osmoprotectors

M. PERULLINI; M AMOURA; C. ROUX; T. CORADIN; J. LIVAGE; ML JAPAS; M. JOBBAGY; S. ALDABE BILMES

MATERIALS CHEMISTRY AND PHYSICS

ELSEVIER SCIENCE SA

Año: 2011 vol. 21 p. 4546 - 4552

0254-0584

The development of sol–gel based processes for the encapsulation of living cells is a challenging taskwhere the host material must be optimized both in terms of intrinsic properties and impact on cellviability. Here, the mechanical stability of silica hosts obtained via a mixed aqueous route based onsodium silicate–silica nanoparticle mixtures could be improved by increasing the relative content ofmolecular precursors over colloidal silica. The specific surface area, pore volume and diffusionproperties of the host were also modified. Moreover, this resulted in an increase in the ionic strength,inducing high osmolarity that is detrimental to encapsulated Escherichia coli bacteria. Glycine betaine,a well-known E. coli osmoprotector, could be successfully used as an additive to the sol–gel formulationto limit this osmotic stress. Compared to the previously studied glycerol additive, glycine betaine wasfound more efficient to preserve the bacterial viability. Moreover, this efficiency was obtained withmuch lower amounts of glycine betaine, whose addition has therefore no detrimental impact on thesilica host structure. These data provide new information about the different cellular stresses resultingfrom the sol–gel encapsulation process and demonstrate the importance of combining chemical andbiological approaches to design more robust functional ‘‘living’’ materials.