The Entrapment of E. coli in Sol-Gel-Derived Silica for Compound Screening

Abstract

<p>Sol-gel derived silica provides a bio-compatible material for the solid-phase entrapment of viable cells. A selection of <em>E. coli</em> cells containing unique promoter-linked GFP expression vectors were applied to fluorescence microwell plate assays, plate counting and various microscopy methods to assess changes in the entrapped bacteria and compatibility towards compound screening. Materials screening showed that a fastgelation sol-gel composition from sodium silicate precursor and PBS buffer provided a consistently greater fluorescence signal than non-entrapped cells. It is shown for the first time that entrapped cells are capable of dividing within pockets of the silica gel, and can di vide at a comparable rate to free cells. The entrapment of cells within a silica matrix does not induce the basal expression level of promoters tested here. Silica entrapment provides improved storage capabilities over non-entrapped cells in solution. A set of 12 related GFP-linked promoters were induced in solution and within silica when screened by two DNA gyrase inhibitors, providing similar expression profiles but greater signal-tonoise ratios in silica. The sol-gel derived material is amenable in an array format, and is a prospective material for the fabrication of sol-gel cell microarrays.</p>