Study of Laser Light Scattering Methods in Rapid Viability Assessment of Microorganisms under Antibiotics Exposure for Adaptation in Lab-on-A-Chip Format.

The antibiotic resistance (ABR) problem is becoming increasingly disturbing and it is important to implement express methods of ABR testing to allow operative antibiotic therapy decisions. The application of laser light scattering (LLS) in microbiological analysis for express ABR testing of microorganisms has been considered. The ways of miniaturization of laser light scattering for creating the bases of their integration into microbiological laboratory-on-a-chip (MLOC) for clinical express diagnostics have been analysed. The advantage of miniaturization in the context of clinical express analysis realization problems are investigated. A system of parallel measuring cells and illumination, enabling simultaneous testing of a group of antibiotics, was tested by splitting a laser beam with a two-dimensional collimator prepared of nanoporous anodic aluminum oxide. It has been demonstrated that the application of LLS methods, providing high concentration and mass sensitivity as well as a miniaturization potential, is an effective approach in the development of new generation diagnostic instruments. The studies have demonstrated the ability of methods to register effects of antibiotics on microbiological samples within 10 min. The following microorganisms were used in the study: Escherichia coli M-17, Lactobacillus plantarum, Bifidobacterium bifidum, Stenotrophomonas maltophilia.

Salt effects on the phase behavior, structure, and rheology of chromonic liquid crystals.

Chromonic liquid crystals are formed by the addition of aromatic molecules such as disodium chromoglycate (cromolyn) to water. In this study, we investigate the addition of salts to the lyotropic nematic phase of cromolyn aqueous solutions. The addition of sodium and potassium salts shifts the isotropic-nematic phase boundary upward by more than 10 degrees C, so that samples that were isotropic at room temperature are transformed into nematic phases. Salt effects are predominantly dictated by the cation, not the anion, and appear to differ based on cation size. In contrast to small, hydrated cations like sodium, large, weakly hydrated cations such as tetraethylammonium and tetrabutylammonium shift the phase boundary downward, thus stabilizing the isotropic phase at the expense of the nematic one. The phase behavior results are highly correlated with viscosity measurements, with an upward shift in the phase boundary correlating with an increase in solution viscosity and vice versa. We also probe the microstructure in cromolyn-salt solutions, both indirectly by small-angle neutron scattering (SANS) and directly by cryo-transmission electron microscopy (cryo-TEM). The cryo-TEM images show the presence of rodlike aggregates that possibly undergo a higher order aggregation into bundles in the presence of salt.