Fluorescent Bacteria Encapsulated in Sol−Gel Derived Silicate Films

Abstract

Recombinant fluorescent E. coli cells were encapsulated in sol-gel derived silicate films. Green and red fluorescent proteins expression by recombinant E. coli strains within the silicate film were studied. The effect of the preparation protocol on the viability of the encapsulated cells and their ability to express the fluorescent proteins in response to genotoxicity stress were evaluated. Confocal microscopy studies revealed a homogeneous distribution of the recombinant cells within the silicate film. We further showed by confocal microscopy studies that the encapsulated cells do not divide within the silicate film. Further, dynamic green fluorescent protein expression studies of a single encapsulated cell were carried out for the first time. No contamination of the surroundings by the encapsulated cells or contamination of the encapsulated culture by the surrounding population of bacteria was observed. The implications of these observations for dual sensing and multistep biosynthesis and biodegradation are discussed.

Bioluminescence of Pseudomonas fluorescens HK44 in the course of encapsulation into silica gel. Effect of methanol

“…But in the thinnest biofilm (F1), 4 h after encapsulation, ≈4 × the original CFU was determined. This increase is in good agreement with the generation period of our strain (1-1½ h) and cannot be attributed to surface proliferation as observed by Premkumar et al (2002b), because we scratched away the surface layer. Even if we take into account the inaccuracy of CFU determination, this result suggests the proliferation of HK44 inside the silica gel.…”

“…In general, silica matrices, due to the zero Young modulus of elasticity, are believed to disable cell proliferation (Inama et al 1993). Nevertheless, some authors have admitted cell growth (Finnie et al 2000;Rooke et al 2008;Alvarez et al 2009) while others have not (Premkumar et al 2002b). In our films, CFU started to increase between 1 and 4 h after encapsulation.…”

Production and properties of threonine aldolase immobilisates

“…The reaction mixture comprises of 0.02 mol of the correspondent silicate (4.5 ml TEOS, 3.95 ml TMOS, 3.98 ml TRIEMOS, 2.85 ml TRIMMOS), 0.4 ml ultrapure H 2 O and 1 ml 0.01 M HCl [37]. The initial two phase system is stirred vigorously at 40 • C until a homogenous sol is obtained.…”

Encapsulation of cells within silica matrixes: Towards a new advance in the conception of living hybrid materials

“…The encapsulated recombinant bacteria maintain their ability to fluorescent signal in the presence of chemical inducers over months at 4°C [74,75]. The silica cages surrounding the bacteria avoid both their proliferation and leaching [76]. As a function of the selected genetically engineered strain, different silica based biosensors have been reported.…”