Ultrabright Red to NIR Emitting Fluorescent Organic Nanoparticles Made from Quadrupolar Dyes with Giant Two-Photon Absorption (2PA) in the NIR Region. Confinement Effect on Fluorescence and 2PA and Tuning of Surface Properties

Fluorescent Organic Nanoparticles (FONs) are light-emitting, molecular-based nanoparticles that can be obtained from the nanoprecipitation of dedicated hydrophobic organic dyes in water. They represent a versatile family of water-soluble fluorescent nanotools whose luminescent properties can be tuned by bottom-up molecular engineering of their composing dyes. We recently reported on a quadrupolar red-emitting dye that yields spontaneously stealthy bare FONs which do not require coating to hinder interactions with cell membranes. Its quadrupolar design also hints to the possibility that it may be a strong two-photon absorber for bioimaging purposes. In this paper, we further investigate the two-photon absorption (2PA) of this dye and resulting FONs and report on a structure-related series of extended dyes engineered to yield NIR-emitting FONs. All dyes lead to stable, small (12–20 nm in diameter), and bright FONs. The experimental study reveals that molecular confinement strongly influences the fluorescence and 2PA properties of these dyes depending on the nature of the π-extended system. As expected, extension of the π-conjugated system induces a red-shift of the absorption and emission bands as well as an increase and spectral broadening of the 2PA responses in solution. Upon aggregation of the dyes within nanoparticles, a reduction of the fluorescence quantum yield is observed whose amplitude depends strongly on the nature of the π-conjugated systems. Interestingly, the peak 2PA cross sections increase upon confinement of the shortest dye, while a spectral broadening and slight red shift of the 2PA bands of the most extended dyes is observed. Taken together, these properties allow the most extended dye to yield very bright NIR-emitting FONs (εmaxΦ = 7 × 106 M–1 cm–1, σ2maxΦ = 4 × 105 GM). Interestingly, the nature of the π-conjugated system was also found to modulate the stealthiness of the resulting nanoparticles toward biological membranes. As a result, by fine-tuning the molecular design of the quadrupolar FON-composing dyes, we achieved NIR-absorbing, NIR-emitting, spontaneously stealthy small nanoparticles having record one- and two-photon brightness. Finally, we demonstrate that these FONs can be noncovalently surface-coated with a polycationic polymer, thanks to their highly negative surface potentials. This induces a reversal of their surface potential which in turn triggers their internalization within cells.Développment d'une infrastructure française distribuée coordonné

Global phylogeography of marine synechococcus in coastal areas reveals strong community shifts

Marine Synechococcus comprise a numerically and ecologically prominent phytoplankton group, playing a major role in both carbon cycling and trophic networks in all oceanic regions except in the polar oceans. Despite their high abundance in coastal areas, our knowledge of Synechococcus communities in these environments is based on only a few local studies. Here, we use the global metagenome data set of the Ocean Sampling Day (June 21st, 2014) to get a snapshot of the taxonomic composition of coastal Synechococcus communities worldwide, by recruitment on a reference database of 141 picocyanobacterial genomes, representative of the whole Prochlorococcus, Synechococcus, and Cyanobium diversity. This allowed us to unravel drastic community shifts over small to medium scale gradients of environmental factors, in particular along European coasts. The combined analysis of the phylogeography of natural populations and the thermophysiological characterization of eight strains, representative of the four major Synechococcus lineages (clades I to IV), also brought novel insights about the differential niche partitioning of clades I and IV, which most often co-dominate the Synechococcus community in cold and temperate coastal areas. Altogether, this study reveals several important characteristics and specificities of the coastal communities of Synechococcus worldwide

From phenomenology to a neurophysiological understanding of hallucinations in children and adolescents

Typically reported as vivid, multisensory experiences which may spontaneously resolve, hallucinations are present at high rates during childhood. The risk of associated psychopathology is a major cause of concern. On the one hand, the risk of developing further delusional ideation has been shown to be reduced by better theory of mind skills. On the other hand, ideas of reference, passivity phenomena, and misidentification syndrome have been shown to increase the risk of self-injury or heteroaggressive behaviors. Cognitive psychology and brain-imaging studies have advanced our knowledge of the mechanisms underlying these early-onset hallucinations. Notably, specific functional impairments have been associated with certain phenomenological characteristics of hallucinations in youths, including intrusiveness and the sense of reality. In this review, we provide an update of associated epidemiological and phenomenological factors (including sociocultural context, social adversity, and genetics, considered in relation to the psychosis continuum hypothesis), cognitive models, and neurophysiological findings concerning hallucinations in children and adolescents. Key issues that have interfered with progress are considered and recommendations for future studies are provided

Travailler à l’hôpital avec la peur en temps de COVID-19

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Taking care of relatives during the COVID-19 pandemic. The experiences of hospital workers in Western Switzerland

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