Ion Depletion in the Interfacial Microenvironment from Cell-Surface Interactions.

The nanoscale region immediately adjacent to surfaces, although challenging to probe, is directly responsible for local chemical and physical interactions between a material and its surroundings. Cell-surface contacts are mediated by a combination of electrostatic and acid-base interactions that alter the local environment over time. In this study, a label-free vibrational probe with a nanometer length scale reveals that the electrostatic potential at a silica surface gradually increases in the presence of bacteria in solution.

Monitoring Early Stages of Bacterial Adhesion at Silica Surfaces through Image Analysis.

Bacterial adhesion and biofilm formation on abiotic surfaces are important phenomena with industrial, environmental, and biological relevance. Recent findings using vibrational spectroscopy to study () K12 adhesion on silica indicated that interfacial water signals are linked to changes at the surface in the presence of bacteria. Although such techniques provide a unique glimpse into the surface microenvironment, the origin of the features tracked by the water signals remains to be identified.

Ions, metabolites, and cells: Water as a reporter of surface conditions during bacterial growth.

Surface-specific nonlinear vibrational spectroscopy, combined with bulk solution measurements and imaging, is used to study the surface conditions during the growth of E. coli. As a result of the silica high surface charge density, the water structure at the silica-aqueous interface is known to be especially sensitive to pH and ionic strength, and surface concentration profiles develop that can be appreciably different from the bulk solution conditions.

Surface-Bulk Vibrational Correlation Spectroscopy.

Homo- and heterospectral correlation analysis are powerful methods for investigating the effects of external influences on the spectra acquired using distinct and complementary techniques. Nonlinear vibrational spectroscopy is a selective and sensitive probe of surface structure changes, as bulk molecules are excluded on the basis of symmetry. However, as a result of this exquisite specificity, it is blind to changes that may be occurring in the solution.