Inert Coats of Magnetic Nanoparticles Prevent Formation of Occlusive Intravascular Co-aggregates With Neutrophil Extracellular Traps

If foreign particles enter the human body, the immune system offers several mechanisms of response. Neutrophils forming the first line of the immune defense either remove pathogens by phagocytosis, inactivate them by degranulation or release of reactive oxygen species or immobilize them by the release of chromatin decorated with the granular proteins from cytoplasm as neutrophil extracellular traps (NETs). Besides viable microbes like fungi, bacteria or viruses, also several sterile inorganic particles including nanoparticles reportedly activate NET formation. The physicochemical nanoparticle characteristics fostering NET formation are still elusive. Here we show that agglomerations of non-stabilized superparamagnetic iron oxide nanoparticles (SPIONs) induce NET formation by isolated human neutrophils, in whole blood experiments under static and dynamic conditions as well as in vivo. Stabilization of nanoparticles with biocompatible layers of either human serum albumin or dextran reduced agglomeration and NET formation by neutrophils. Importantly, this passivation of the SPIONs prevented vascular occlusions in vivo even when magnetically accumulated. We conclude that higher order structures formed during nanoparticle agglomeration primarily trigger NET formation and the formation of SPION-aggregated NET-co-aggregates, whereas colloid-disperse nanoparticles behave inert and are alternatively cleared by phagocytosis

Aluminum oxide nanowires as safe and effective adjuvants for next-generation vaccines

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A Novel Integrated Way for Deciphering the Glycan Code for the FimH Lectin

The fimbrial lectin FimH from uro- and enteropathogenic Escherichia coli binds with nanomolar affinity to oligomannose glycans exposing Manα1,3Man dimannosides at their non-reducing end, but only with micromolar affinities to Manα1,2Man dimannosides. These two dimannoses play a significantly distinct role in infection by E. coli. Manα1,2Man has been described early on as shielding the (Manα1,3Man) glycan that is more relevant to strong bacterial adhesion and invasion. We quantified the binding of the two dimannoses (Manα1,2Man and Manα1,3Man to FimH using ELLSA and isothermal microcalorimetry and calculated probabilities of binding modes using molecular dynamics simulations. Our experimentally and computationally determined binding energies confirm a higher affinity of FimH towards the dimannose Manα1,3Man. Manα1,2Man displays a much lower binding enthalpy combined with a high entropic gain. Most remarkably, our molecular dynamics simulations indicate that Manα1,2Man cannot easily take its major conformer from water into the FimH binding site and that FimH is interacting with two very different conformers of Manα1,2Man that occupy 42% and 28% respectively of conformational space. The finding that Manα1,2Man binding to FimH is unstable agrees with the earlier suggestion that E. coli may use the Manα1,2Man epitope for transient tethering along cell surfaces in order to enhance dispersion of the infection

Reduced Graphene Oxide Embedded Polymeric Nanofiber Mats: An ‘On-Demand’ Photothermally-Triggered Antibiotic Release Platform

International audienceThe steady increase in antimicrobial resistance in different 16 pathogens requires the development of alternative treatment strategies 17 next to the oral delivery of antibiotics. A photothermally activated 18 platform based on reduced graphene oxide (rGO)-embedded polymeric 19 nanofiber mats for on-demand release of antibiotics upon irradiation in 20 the near-infrared is fabricated. Cross-linked hydrophilic nanofibers, 21 obtained by electrospinning a mixture of poly(acrylic acid) (PAA) and 22 rGO, show excellent stability in aqueous media. Importantly, these PAA@ 23 rGO nanofiber mats exhibit controlled photothermal heating upon 24 irradiation at 980 nm. Nanofiber mats are efficiently loaded with 25 antibiotics through simple immersion into corresponding antibiotics 26 solutions. Whereas passive diffusion based release at room temperature is 27 extremely low, photothermal activation results in increased release within 28 few minutes, with release rates tunable through power density of the 29 applied irradiation. The large difference over passive and active release, as well as the controlled turn-on of release allows 30 regulation of the dosage of the antibiotics, as evidenced by the inhibition of planktonic bacteria growth. Treatment of superficial 31 skin infections with the antibiotic-loaded nanofiber mats show efficient wound healing of the infected site. Facile fabrication and 32 implementation of these photothermally active nanofiber mats makes this novel platform adaptable for on-demand delivery of 33 various therapeutic agents. 3

Flexible Nanoholey Patches for Antibiotic-Free Treatments of Skin Infections

Despite the availability of different antibiotics, bacterial infections are still one of the leading causes of hospitalization and mortality. The clinical failure of antibiotic treatment is due to a general poor antibiotic penetration to bacterial infection sites as well as the development of antibiotic-resistant pathogens. In the case of skin infection, the wound is covered by exudate, making it impermeable to topical antibiotics. The development of a flexible patch allowing a rapid and highly efficient treatment of subcutaneous wound infections via photothermal irradiation is presented here. The skin patch combines the near-infrared photothermal properties of a gold nanohole array formed by self-assembly of colloidal structures on flexible polyimide films with that of reduced graphene oxide nanosheets for laser-gated pathogen inactivation. In vivo tests performed on mice with subcutaneous skin infection and treated with the photothermal skin patch show wound healing of the infected site, while nontreated areas result in necrotic muscular fibers and bacterial infiltrate. No loss in efficiency is observed upon multiple use of these patches during in vivo experiments because of their robustness

Improved photodynamic effect through encapsulation of two photosensitizers in lipid nanocapsules

International audiencePhotodynamic therapy (PDT) has developed into a new clinical and non-invasive treatment for cancer over the past 30 years. By the combination of three non-toxic partners, i.e. a photosensitizer (PS), molecular oxygen (O2) and light, cytotoxic reactive oxygen species (ROS) are locally produced leading to irreversible vascular and cellular damage. In the present study, we report for the first time that the combination of two photosensitizers (2 PSs: Protoporphyrin IX, PpIX and Hypericin, Hy) loaded in the same lipid nanocapsules (LNCs) leads to enhanced photodynamic therapy efficiency when compared with previously reported systems. The 2 PS-loaded LNCs are shown to increase the in vitro phototoxicity at the nanomolar range (IC50 = 274 and 278 nM on HeLa and MDA-MB-231 cell lines, respectively), whereas the corresponding single PS-loaded LNCs at the same concentration exhibit a phototoxicity two times lower. Intracellular localization in HeLa cells indicates a subcellular asymmetry of PpIX and Hy, in the plasma, ER membranes and round internal structures. The biodistribution of LNCs was studied upon different routes of injection into Swiss nude mice; based on the obtained data, LNCs were injected intratumorally and used to slow the growth of xenograft tumors in mice. The results obtained in this study suggest that the combination of two or more PSs may be a promising strategy to improve the efficacy of conventional photodynamic therapy as well as to reduce dark toxicity

Neutrophil Extracellular Traps Initiate Gallstone Formation

The presence of gallstones (cholelithiasis) is a highly prevalent and severe disease and one of the leading causes of hospital admissions worldwide. Due to its substantial health impact, we investigated the biological mechanisms that lead to the formation and growth of gallstones. We show that gallstone assembly essentially requires neutrophil extracellular traps (NETs). We found consistent evidence for the presence of NETs in human and murine gallstones and describe an immune-mediated process requiring activation of the innate immune system for the formation and growth of gallstones. Targeting NET formation via inhibition of peptidyl arginine deiminase type 4 or abrogation of reactive oxygen species (ROS) production, as well as damping of neutrophils by metoprolol, effectively inhibit gallstone formation in vivo. Our results show that after the physicochemical process of crystal formation, NETs foster their assembly into larger aggregates and finally gallstones. These insights provide a feasible therapeutic concept to prevent cholelithiasis in patients at risk