| AVS 64th International Symposium & Exhibition | |
| Biomaterial Interfaces Division | Thursday Sessions |
| Session BI+AS+SA-ThM |
| Session: | Characterisation of Biological and Biomaterial Surfaces |
| Presenter: | Dmitri Petrovykh, International Iberian Nanotechnology Laboratory, Portugal |
| Authors: | C. Sousa, International Iberian Nanotechnology Laboratory, Portugal K. Jankowska, International Iberian Nanotechnology Laboratory, Portugal L. Parga Basanta, International Iberian Nanotechnology Laboratory, Portugal I.M. Pinto, International Iberian Nanotechnology Laboratory, Portugal D.Y. Petrovykh, International Iberian Nanotechnology Laboratory, Portugal |
| Correspondent: | Click to Email |
Physicochemical properties of bacterial cells make them challenging subjects for methods typically used to characterize micro- and nanoparticles. Even for conceptually simple parameters, such as size and concentration, direct characterization of live bacteria (and their agglomerates) in solution is far from trivial because bacterial cells are soft and often anisotropic particles with sizes of not more than a few microns. Low contrast, in terms of optical and electronic properties, between bacteria and their aqueous environment complicates any attempted direct measurements in solution. Comparing bacterial cells to non-biological micro- or nanoparticles, whether in the context of mixed samples or calibration measurements, further compounds the complexity of characterizing these systems.
We are using Staphylococcus aureus (S. aureus) bacteria as a model system for quantitative characterization of bacterial cells. For systematic measurements, S. aureus bacteria offer the advantages of nearly spherical shape and of robust viability under a wide range of experimental conditions and treatments. The approximately one micron diameter of live S. aureus cells also makes them representative of the sensitivity and resolution challenges encountered in the characterization of bacterial cells. In microscopy, for example, the apparent size of individual S. aureus bacteria changes dramatically as they are prepared for measurements with increased spatial resolution: from confocal optical microscopy, to environmental scanning electron microscopy (SEM), to SEM in vacuum.
The objective of our work is to develop and validate a set of complementary techniques that can be used to characterize live bacterial cells. We will describe the use of nanoporous membranes with S. aureus suspensions and commonly overlooked effects of centrifugation, mechanical agitation, and other typical sample preparation procedures on the apparent distribution and properties of particles in biological samples. The forced contact of bacteria with these membranes during filtering also suggests their use as model systems for investigating the interactions of bacteria with surfaces having different chemistries and/or morphological features.