From In Situ to satellite observations of pelagic Sargassum distribution and aggregation in the Tropical North Atlantic Ocean

International audienceThe present study reports on observations carried out in the Tropical North Atlantic in summer and autumn 2017, documenting Sargassum aggregations using both ship-deck observations and satellite sensor observations at three resolutions (MSI-10 m, OLCI-300 m, VIIRS-750 m and MODIS-1 km). Both datasets reported that in summer, Sargassum aggre-gations were mainly observed off Brazil and near the Caribbean Islands, while they accumulated near the African coast in autumn. Based on in situ observations, we propose a five-class typology allowing standardisation of the description of in situ Sargassum raft shapes and sizes. The most commonly observed Sargassum raft type was windrows, but large rafts composed of a quasi-circular patch hundreds of meters wide were also observed. Satellite imagery showed that these rafts formed larger Sargassum aggregations over a wide range of scales, with smaller aggregations (of tens of m 2 area) nested within larger ones (of hundreds of km 2). Match-ups between different satellite sensors and in situ observations were limited for this dataset, mainly because of high cloud cover during the periods of observation. Nevertheless, comparisons between the two datasets showed that satellite sensors successfully detected Sargassum abundance and aggregation patterns consistent with in situ observations. MODIS and VIIRS sensors were better suited to describing the Sargas-sum aggregation distribution and dynamics at Atlantic scale, while the new sensors, OLCI and MSI, proved their ability to detect Sargassum aggregations and to describe their (sub-) mesoscale nested structure. The high variability in raft shape, size, thickness, depth and biomass density observed in situ means that caution is called for when using satellite maps of Sargassum distribution and biomass estimation. Improvements would require additional in situ and airborne observations or very high-resolution satellite imagery

Fluorescent and magnetic stellate mesoporous silica for bimodal imaging and magnetic hyperthermia

There is currently a crucial need of innovative multifunctional nanoparticles combining, in one formulation, imaging and therapy capacities allowing thus an accurate diagnosis and a therapy monitored by imaging. Multimodal imaging will ensure to speed up diagnosis, and to increase its sensitivity, reliability and specificity for a better management of the disease. Combined with a therapeutic action, it will also enable to treat the disease in a specific personalized manner in feedback mode. The mastered design of such bioprobes as well as the demonstration of their efficiency are still challenges to face in nanomedicine. In this work, novel fluorescent and magnetic core–shell nanocomposites have been designed to ensure, in one nanoformulation, bimodal fluorescence and MRI imaging coupled with therapy by magnetic hyperthermia. They consist in the coating of a magnetic iron oxide (IO) core (ca. 18 nm diameter to ensure magnetic hyperthermia) by an original large pore stellate mesoporous silica (STMS) shell to produce uniform and mono-core magnetic core–shell nanocomposites denoted IO@STMS NPs. To confer fluorescence properties, CdSe/ZnS quantum dots (QDs) NPs were grafted inside the large pores of the IO@STMS nanocomposites. To provide biocompatibility and opsonization-resistance, a tightly-bound human serum albumin (HSA) coating is added around the nanocomposite using an original IBAM-based strategy. Cellular toxicity and non-specific cell–nanomaterial interactions allowed to determine a concentration range for safe application of these NPs. Cellular endosomes containing spontaneously-uptaken NPs displayed strong and photostable QD fluorescence signals while magnetic relaxivity measurements confirm their suitability as contrast agent for MRI. HeLa cell-uptaken NPs exposed to a magnetic field of 100 kHz and 357 Gauss (or 28.5 kA m−1) display an outstanding 65% cell death at a very low iron concentration (1.25 μg Fe mL−1), challenging current magnetic hyperthermia nanosystems. Furthermore, at the particularly demanding conditions of clinical use with low frequency and amplitude field (100 kHz, 117 Gauss or 9.3 kA m−1), magnetic hyperthermia combined with the delivery of a chemotherapeutic drug, doxorubicin, allowed 46% cell death, which neither the drug nor the NPs alone yielded, evidencing thus the synergistic effect of this combined treatment.Facultad de Ciencias VeterinariasInstituto de Investigaciones Fisicoquímicas Teóricas y AplicadasInstituto de Física La Plat

Mesoporous silica templated-albumin nanoparticles with high doxorubicin payload for drug delivery assessed with a 3-D tumor cell model

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Multiscale characterization of the in vitro digestion of a milk-based emulsion

The luminal phase of lipid digestion consists in a succession of physical (emulsification, aggregation, solubilization, micellarization…) and biochemical modifications (enzymatic hydrolysis of molecules). These modifications take place in various digestive compartments and under the action of a large set of lipolytic enzymes having welldefined substrate selectivity (gastric lipase, pancreatic triglyceride lipase, bile salt stimulated lipase, phospholipase A2 …). This complex phenomena is approached using dynamic or static models of digestion.[br/] Static models (with constant ratio food/simulated digestive fluids for a given compartment) are considered as effective tools to screen a high number of experimental conditions though they reproduce less precisely the transient conditions occurring in vivo. Static models present the main advantage of using a small amount of substrate, enzymes and simulated fluids

Photodynamic Efficacy of Cercosporin in 3D Tumor Cell Cultures

In the present work, we study the photodynamic action of cercosporin (cerco), a naturally occurring photosensitizer, on human cancer multicellular spheroids. U87 spheroids exhibit double the uptake of cerco than T47D and T98G spheroids as shown by flow cytometry on the single cell level. Moreover, cerco is efficiently internalized by cells throughout the spheroid as shown by confocal microscopy, for all three cell lines. Despite their higher cerco uptake, U87 spheroids show the least vulnerability to cerco‐PDT, in contrast to the other two cell lines (T47D and T98G). While 300 μm diameter spheroids consistently shrink and become necrotic after cerco PDT, bigger spheroids (>500 μm) start to regrow following blue‐light PDT and exhibit high viability. Cerco‐PDT was found to be effective on bigger spheroids reaching 1mm in diameter especially under longer exposure to yellow light (~590 nm). In terms of metabolism, T47D and T98G undergo a complete bioenergetic collapse (respiration and glycolysis) as a result of cerco‐PDT. U87 spheroids also experienced a respiratory collapse following cerco‐PDT, but retained half their glycolytic activity

Drug-Loaded Lipid-Coated Hybrid Organic-Inorganic “Stealth” Nanoparticles for Cancer Therapy

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<p>An unexpected case of <em>Bartonella alsatica</em> prosthetic vascular graft infection</p>

International audienceBartonella alsatica is a wild rabbit pathogen causing bacteremia rarely reported in humans, with only three cases published so far, including one lymphadenitis and two endocarditis cases. Here, we report the case of a 66-year-old man who suffered from acute renal failure due to a membranoproliferative glomerulonephritis. Fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) showed diffuse FDG uptake around the aortobifemoral graft with no indication of infection. A white blood cell scan showed an accumulation of labeled neutrophils on the left femoral part of the graft. The patient underwent surgery and an abscess around the left iliac part of the graft was found intraoperatively. Intraoperative samples were all negative, but 16S rRNA gene-based PCR was positive, and the sequence was positioned among the Bartonella species cluster. Specific PCRs targeting groEL/hsp60, rpoB and gltA genes were performed and led to the identification of B. alsatica. Accordingly, indirect immunofluorescence serological analyses were positive for Bartonella henselae and Bartonella quintana. The patient had a history of regularly hunting wild rabbits. He was treated with 100 mg of doxycycline twice a day for six months and his renal function significantly improved with no sign of persistent infection. This case highlights the contribution of serology assays and molecular-based methods in prosthetic vascular graft infection diagnosis

Design of hybrid protein-coated magnetic core-mesoporous silica shell nanocomposites for MRI and drug release assessed in a 3D tumor cell model

International audienceIn this work, we describe the design and the use of a novel theranostic hybrid nanocomposite made of an iron oxide core and a mesoporous silica shell (IO@MS) of ca. 30 nm coated by human serum albumin (HSA) layer for magnetic resonance imaging and drug delivery applications. The porosity of IO@MS nanoparticles was loaded with an antitumoral drug, Doxorubicin (Dox) reaching a high drug loading capacity (DLC) of 34 w%. To entrap the drug, a tight HSA coating held via isobutyramide (IBAM) binders was deposited. We show that this protein nanoassembly entraps the drugs efficiently and behaves as an innovative enzyme-sensitive gatekeeper that is degraded upon protease action. Finally we assess the Dox release in a 3D cell model via confocal imaging and its cytotoxicity is shown by growth inhibition studies on liver cancer cell spheroid