Mechanistic insights into silica nanoparticle-allergen interactions on antigen presenting cell function in the context of allergic reactions.

The incorporation of nanomaterials into consumer products has substantially increased in recent years, raising concerns about their safety. The inherent physicochemical properties of nanoparticles allow them to cross epithelial barriers and gain access to immunocompetent cells. Nanoparticles in cosmetic products can potentially interact with environmental allergens, forming a protein corona, and together penetrate through damaged skin. Allergen-nanoparticle interactions may influence the immune response, eventually resulting in an adverse or beneficial outcome in terms of allergic reactivity. This study determines the impact of silica nanoparticle-allergen interactions on allergic sensitization by studying the major molecular mechanisms affecting allergic responses. The major birch pollen allergen Bet v 1 was chosen as a model allergen and the birch pollen extract as a comparator. Key events in immunotoxicity including allergen uptake, processing, presentation, expression of costimulatory molecules and cytokine release were studied in human monocyte-derived dendritic cells. Using an in vivo sensitization model, murine Bet v 1-specific IgG and IgE levels were monitored. Upon the interaction of allergens with silica nanoparticles, we observed an enhanced uptake of the allergen by macropinocytosis, improved proteolytic processing, and presentation concomitant with a propensity to increase allergen-specific IgG2a and decrease IgE antibody levels. Together, these events suggest that upon nanoparticle interactions the immune response is biased towards a type 1 inflammatory profile, characterized by the upregulation of T helper 1 (Th1) cells. In conclusion, the interaction of the birch pollen allergen with silica nanoparticles will not worsen allergic sensitization, a state of type 2-inflammation, but rather seems to decrease it by skewing towards a Th1-dominated immune response.

The red alga Tsunamia transpacifica (Stylonematophyceae) from plastic drift shows adaptation to its uncommon habitat in ultrastructure and soluble low molecular weight carbohydrate composition.

The recently described red alga Tsunamia transpacifica (Stylonematophyceae) was previously isolated from plastic drift found at the pacific coast, but the natural habitat remains unknown. Here, we investigate ultrastructural details and the low molecular weight soluble carbohydrate composition to get further insight into the adaptation to this uncommon habitat. By means of high pressure freeze fixation, followed by freeze substitution, we could detect an up to 2-µm-thick cell wall surrounded by a distinct layer of extracellular polymeric substances (EPS), likely responsible for the adhering capacities of Tsunamia. The central position of the nucleus and multilobed parietal chloroplast, already observed by light microscopy, could be confirmed. The ultrastructure revealed large electron-dense bodies (EB) in the central cytoplasm, likely resembling degradation products of the chloroplast. Interestingly, these structures contained phosphorous and cobalt, and iron was found in smaller rounded electron-dense bodies by electron energy loss spectroscopy (EELS). Accumulation of these elements suggests a high biosorption activity of Tsunamia. Liquid chromatography-mass spectrometry (LC-MS) data showed the presence of two heterosides (floridoside and digeneaside) together with the polyol sorbitol, which are known as organic osmolytes and compatible solutes. Taken together, these are the first observations on ultrastructural details, element storage and accumulation of protective compounds are contributing to our understanding of the ultrastructural and osmotic solute basis for the ability of Tsunamia to thrive on plastic surfaces.