Bacteria viability in sol-gel materials revisited: Cryo-SEM as a suuitable tool to study the structural integrity of encapsulated bacteria

Biocompatibility is an important issue that still needs research if one desires to fully preserve the metabolic activity of cells encapsulated in any type of material. Spectroscopic techniques (e.g., NMR and fluorescence) have been used to study the viability decrease upon aging time of bacteria encapsulated in silica gel materials. Unfortunately, none of these spectroscopic techniques are able to provide insights about the detrimental causes affecting the viability of encapsulated cells. The current work uses cryoscanning electron microscopy (cryo-SEM) for the in situ study of hydrated biocomposites, given its ability for mapping the water distribution within the host matrix. Cryo-SEM is accompanied by fluorescence experiments which allow correlating the metabolic activity of the cells with their structural integrity. The combination of these techniques provides useful information for the design of new biocomposites where encapsulated bacteria preserve their structural integrity and, thus, are viable for periods of time in a range similar to those found for bacteria suspended in buffered solutions.