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RESEARCH PRODUCT

Bacteria survival and growth in multi-layered silica thin films

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International audience; The fields of application of sol–gel encapsulation technology for living cells have been greatly extended over the last few years. Photobioreactors,1 biofuel cells,2 bio-remediation materials,3 biosensors4 and biomedical devices5 are currently being developed taking advantage of the robustness of inorganic materials compared to their (bio)-organic counterparts. In many of these applications, the formation of stable thin films (<1 μm) would be highly desirable for integration, for instance, in bio-chips.6 However, several limitations exist when trying to transfer a protocol mainly developed from bulk hydrogels to thin films. Especially, the storage stability becomes more challenging because preservation in liquid media may lead to fast film dissolution whereas drying can impact on both cell viability and film behaviour (cracking, peeling-off, …). Previous reports on thin film storage at 4 °C in a humid atmosphere were successful for algae and bacterial spores but not for bacterial cells.7,8 The use of phospholipids that self-organize around cells and confine water at their vicinity was described allowing long-term preservation under ambient conditions.9 However, another important issue for applicability is that the number of cells available for further transformation/sensing decreases with film thickness.