Search

The surface morphology and structural properties of polystyrene (PS)/TiO₂ nanocomposites were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD), while optical properties were assessed via UV-Vis spectroscopy and Fluorescence measurements. SEM images revealed uniform dispersion of TiO₂ nanoparticles with sizes ranging from 48 to 58.5 nm in the PS matrix, showing no significant agglomeration. XRD analysis revealed a decrease in crystallite size with increasing TiO₂ concentration. UV-Vis spectra demonstrated a decrease in the band gap with increasing TiO₂ concentration, indicating a shift towards enhanced visible light absorption. PL spectra excited at 330 nm revealed distinct emission peaks, with significant increases in intensity at higher TiO₂ concentrations, particularly at 399 nm and 422.5 nm, corresponding to near-band-edge and defect-related emissions. FTIR analysis demonstrated that the incorporation of TiO₂ led to disruption of C-O bonds in the PS matrix, particularly at 10% TiO₂, suggesting strong interactions between the TiO₂ nanoparticles and the polymer, which may weaken the polymer backbone. Overall, these findings suggest that TiO₂ incorporation not only impacts crystallite size and strain but also enhances the optical and fluorescence properties of PS/TiO₂ nanocomposites. [ABSTRACT FROM AUTHOR]

Understanding the ontogeny of teleost mucosa-associated lymphoid tissues (MALT) is critical for determining the earliest timepoint for effective mucosal vaccination of young fish. Here, we describe the developmental sequence that leads to the formation of an organized MALT structure in rainbow trout, the organized nasopharynx-associated lymphoid tissue (O-NALT). Control rainbow trout were sampled between 340 and 1860 degree days (DD) and routine histology and immunofluorescence staining were used to determine cellular changes in immune cells in the nasal cavity as well as O-NALT formation. We identified that O-NALT is first seeded by CD8α + T cells at 700 DD followed by IgM + B cells and cd4-2b +  cells at 1000 DD. Histomorphologically, trout O-NALT is fully formed at 1400 DD. Whole body gene expression analyses uncovered waves of igmh, cd4-2b, and cd8a expression that recapitulate the cellular seeding sequence of O-NALT by specific lymphocyte subsets. Our results indicate that 1) O-NALT formation results from a specific sequence of lymphocyte subset colonization pioneered by CD8α + T cells and 2) the presence of the full O-NALT structure at 1400 DD may mark this timepoint as the earliest developmental stage at which mucosal vaccines can induce long lasting, specific immune responses., (Copyright © 2024 Elsevier Ltd. All rights reserved.)