KEYWORDS: Luminescence, Bacteria, Pathogens, Microscopy, Statistical analysis, Biological research, Signal processing, Microorganisms, Blood, Signal to noise ratio
Bacterial infectious diseases remain one of the major health hazards nation- and worldwide. The expedience of detection
and identification of bacterial pathogens determines how early the diagnosis is, and hence, what the treatment and the
outcome of the illness would be. As we have previously reported, the dynamics of fluorescence staining provides venues
for the development of expedient assays for detection and identification of bacterial species[1]. We measured the kinetics
of bacterial staining with cyanine and thioflavin dyes and investigated their photophysical properties. We demonstrated
that the pseudo first-order kinetic constants of the fluorescence staining processes have species specificity without
contrition dependence. Combining the dynamics of staining with real-time fluorescence microscopy we characterized the
fluorescence staining process at the single-cell level with improved sensitivity and contrast.
Near-infrared (NIR) optically active nanoparticles are promising exogenous chromophores for applications in medical imaging and phototherapy. Since nanoparticles can be rapidly eliminated from the body by cells of the reticuloendothelial system, a thriving strategy to increase their blood circulation time is through surface modification with polyethylene glycol (PEG). We constructed polymeric nanocapsules loaded with indocyanine green (ICG), an FDA-approved NIR dye, and coated with aldehyde-terminated PEG. Using optical absorbance spectroscopy and flow cytometry, we investigated the effect of PEG coating and molecular weight (MW) of PEG [5000 and 30,000 Daltons (Da)] on the phagocytic content of human spleen macrophages incubated with ICG-containing nanocapsules (ICG-NCs) between 15 to 360 min. Our results indicate that surface coating with PEG is an effective method to reduce the phagocytic content of ICG-NCs within macrophages for at least up to 360 min of incubation time. Coating the surface of ICG-NCs with the low MW PEG results in lower phagocytic content of ICG-NCs within macrophages for at least up to 60 min of incubation time as compared to ICG-NCs coated with the high MW PEG. Surface coating of ICG-NCs with PEG is a promising approach to prolong vasculature circulation time of ICG for NIR imaging and phototherapeutic applications.
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