Biogenic Silver Nanoparticles and Stressors Generate Synergistic Growth Inhibition in Candida Species through Cell Wall Damage, Osmotic Stress, and Oxidative Stress.

BACKGROUND: The need to combat and reduce the incidence, virulence, and drug resistance of species belonging to Candida genus, has led to the development of new strategies. Nanotechnology, through the implementation of nanomaterials, has emerged as an infallible tool to treat various diseases caused by pathogens, where its mechanisms of action prevent the development of undesirable pharmacological resistance. OBJECTIVE: The antifungal activity and adjuvant properties of biogenic silver nanoparticles in different Candida species (C. parapsilosis, C. glabrata, and C. albicans) are evaluated. METHODS: The biogenic metallic nanoparticles were developed by quercetin-mediated biological synthesis. The physicochemical properties were studied by light scattering, electrophoretic mobility, UV-vis and infrared spectroscopy, and transmission electron microscopy. The elucidation of mechanisms of antifungal action was carried out under stress conditions in Candida species at the cell wall and response to oxidative stress. RESULTS: Small silver nanoparticles (≈ 16.18 nm) with irregular morphology, and negative surface electrical charge (≈ -48.99 mV), were obtained through quercetin-mediated biosynthesis. Infrared spectra showed that the surface of silver nanoparticles is functionalized with the quercetin molecule. The antifungal activity of biogenic nanoparticles had efficacy in the following trend C. glabrata ≥ C. parapsilosis > C. albicans. Biogenic nanoparticles and stressors showed synergistic and potentiated antifungal effects through cell damage, osmotic stress, cell wall damage, and oxidative stress. CONCLUSIONS: Silver nanoparticles synthesized by quercetin-mediated biosynthesis could be implemented as a powerful adjuvant agent to enhance the inhibition effects of diverse compounds over different Candida species.

Nanostructured mesoporous silica materials induce hormesis on chili pepper (Capsicum annuum L.) under greenhouse conditions.

Current agricultural practices for vegetable production are unsustainable, and the use of certain nanomaterials has shown significant potential for either plant growth promotion or defense induction in crop species. The aim of the present work was to evaluate the possible effects of two SBA nano-structured silica materials differing in morphology; SBA-15, with porous structure in parallel and with a highly ordered hexagonal array and SBA-16, with spheric nano-cages located in cubic arrays, as plant growth promoters/eustressors on chili pepper (Capsicum annuum L.) during cultivation under greenhouse conditions. The study was carried out at three foliarly applied concentrations (20, 50 and 100 ppm) of either SBA materials to determine effects on seed germination, seedling growth, plant performance and cold tolerance under greenhouse. Phytotoxicity tests were carried out using higher concentrations (100, 1000 and 200 ppm) applied by dipping or spraying onto chili pepper plants. Deionized water controls were included. The results showed that the SBA materials did not affect seed germination; however, SBA-15 at 50 ppm and 100 ppm applied by imbibition significantly increased seedling height (up to 8-fold) and provided enhanced growth performance in comparison with controls under select treatment regimes. Weekly application of SBA-15 at 20 ppm significantly increased stem diameter and cold tolerance; however, SBA-16 showed significant decreases in plant height (20 ppm biweekly applied) and stem diameter (20, 50 and 100 ppm biweekly applied). The results demonstrate that both SBA materials provided hormetic effects in a dose dependent manner on chili pepper production and protection to cold stress. No phytotoxic response was evident. These findings suggested the nanostructured mesoporous silica have potential as a sustainable amendment strategy to increase crop production under stress-inducing cultivation conditions.

Pathogen associated molecular pattern-decorated mesoporous silica-A colloidal model for studying bacterial-host cell interactions.

Tuberculosis is the top infectious disease worldwide and the development of a vaccine and diagnostic tools to control the disease is a priority that requires a better understanding of the factors involved in the pathogenesis of Mycobacterium tuberculosis, the infectious agent. It is known that bacterial cell surface components are released, interact with immune cell receptors, and may traffic toward host cell structures. Many of these compounds are lipids that have been associated with mycobacterial virulence. However, their hydrophobic nature has frequently hampered their biological study. In this work, silica particles were coated with functional lipids to obtain a colloidal bioinspired system based on nonhydrosoluble glycolipids. Mycobacterium tuberculosis phosphatidylinositol mannosides (PIMs), known to interact with receptors of innate immune cells, were purified from the M. tuberculosis H37Rv type strain, and used to prepare large unilamellar liposomes in combination with zwitterionic phosphatidyl choline. Then, bacillary-like Santa Barbara Amorphous-15 (SBA-15) silica particles were cationized and the vesicle fusion method was used to promote the attachment of anionic PIM-containing lipid bilayers. Thermogravimetric analysis, x-ray diffraction, N2 adsorption-desorption isotherm analysis, Fourier transform infrared spectroscopy, electron microscopy, and zeta potential analyses were used to characterize the materials obtained. The as-prepared PIM-containing colloids, named PIM@SBA-15, showed biocompatibility toward human fibroblasts and were found to colocalize with Toll-like receptor (TLR)2 upon their incubation with THP1-derived macrophages. Furthermore, the particles induced the formation of pseudopods and were internalized into phagocytic cells. In all, these data suggest the usefulness of PIM@SBA-15 particles to better comprehend the interactions between immune cells and PIMs.