Interaction of Antibiotics with Lipid Vesicles on Thin Film Porous Silicon Using Reflectance Interferometric Fourier Transform Spectroscopy

International audienceThe ability to observe interactions of drugs with cell membranes is an important area in pharmaceutical research. However, these processes are often difficult to understand due to the dynamic nature of cell membranes. Therefore, artificial systems composed of lipids have been used to study membrane properties and their interaction with drugs. Here, lipid vesicle adsorption, rupture, and formation of planar lipid bilayers induced by various antibiotics (surfactin, azithromycin, gramicidin, melittin and ciprofloxacin) and the detergent dodecyl-b-D-thiomaltoside (DOTM) was studied using reflective interferometric Fourier transform spectroscopy (RIFTS) on an oxidized porous silicon (pSi) surface as a transducer. The pSi transducer surfaces are prepared as thin films of 3 μm thickness with pore dimensions of a few nanometers in diameter by electrochemical etching of crystalline silicon followed by passivation with a thermal oxide layer. Furthermore, the sensitivity of RIFTS was investigated using three different concentrations of surfactin. Complementary techniques including atomic force microscopy, fluorescence recovery after photobleaching, and fluorescence microscopy were used to validate the RIFTS-based method and confirm adsorption and consequent rupture of vesicles to form a phospholipid bilayer upon the addition of antibiotics. The method provides a sensitive and real-time approach to monitor the antibiotic-induced transition of lipid vesicles to phospholipid bilayers

Mimicking Influenza Virus Fusion Using Supported Lipid Bilayers

Influenza virus infection is a serious public health problem in the world, and understanding the molecular mechanisms involved in viral replication is crucial. In this paper, we used a minimalist approach based on a lipid bilayer supported on mica, which we imaged by atomic force microscopy (AFM) in a physiological buffer, to analyze the different steps of influenza fusion, from the interaction of intact viruses with the supported bilayer to their complete fusion. Our results show that sialic acid recognition and priming upon acidification are sufficient for a complete fusion with the host cell membrane. After fusion, a flat and continuous membrane was observed. Because of the fragility of the viral membrane that was removed by the tip, most probably due to the disorganization of the matrix layer at acidic pH, fine structural details of ribonucleoproteins (RNP) were obtained. In addition, AFM topography of intact virus in interaction with the supported lipid bilayer confirms that hemeagglutinin and neuraminidase can form isolated clusters within the viral membrane

Interaction of Antibiotics with Lipid Vesicles on Thin Film Porous Silicon Using Reflectance Interferometric Fourier Transform Spectroscopy

The ability to observe interactions of drugs with cell membranes is an important area in pharmaceutical research. However, these processes are often difficult to understand due to the dynamic nature of cell membranes. Therefore, artificial systems composed of lipids have been used to study membrane properties and their interaction with drugs. Here, lipid vesicle adsorption, rupture, and formation of planar lipid bilayers induced by various antibiotics (surfactin, azithromycin, gramicidin, melittin and ciprofloxacin) and the detergent dodecyl-<i>b</i>-d-thiomaltoside (DOTM) was studied using reflective interferometric Fourier transform spectroscopy (RIFTS) on an oxidized porous silicon (pSi) surface as a transducer. The pSi transducer surfaces are prepared as thin films of 3 μm thickness with pore dimensions of a few nanometers in diameter by electrochemical etching of crystalline silicon followed by passivation with a thermal oxide layer. Furthermore, the sensitivity of RIFTS was investigated using three different concentrations of surfactin. Complementary techniques including atomic force microscopy, fluorescence recovery after photobleaching, and fluorescence microscopy were used to validate the RIFTS-based method and confirm adsorption and consequent rupture of vesicles to form a phospholipid bilayer upon the addition of antibiotics. The method provides a sensitive and real-time approach to monitor the antibiotic-induced transition of lipid vesicles to phospholipid bilayers

'Continuous Droplet Interface Crossing Encapsulation (cDICE): artificial cells and capsules

The Continuous Droplet Interface Crossing Encapsulation (cDICE) is an easy and robust method for producing, at high yield, monodisperse lipid vesicles with a controlled content as well as capsules with a designed shell. It consists in forcing a droplet through an interface between two imiscible fluids, using an external force such as centrifugation. At high inertia, the droplet entrain fluid that will constitute the shell of the capsule. At low inertia, the presence of amphiphile and the deformable interface interactions lead to monolayers zipping and formation of an amphiphile bilayer around the droplet. We will discuss the physical mechanisms involved in the production of both cDICE vesicles (low droplets inertia) and capsules (at high inertia), and the potential applications of this method. This method founds indeed many applications in biomimetics as it allows to encapsulate various biological solutions (biopolymers, hemoglobin, colloids, polymeric gels, cells. . . ) in membranes that can be composite and/or assymetric, or polymeric, and in the field of microencapsulation

Real-time Multi-Messenger Analysis Framework of KM3NeT

KM3NeT is a multi-purpose cubic-kilometer neutrino observatory in construction in the Mediter- ranean Sea. It consists of ORCA and ARCA (for Oscillation and Astroparticle Research with Cosmics in the Abyss, respectively); currently both have a few detection lines in operation. Al- though having different primary goals, both detectors can be used to do neutrino astronomy over a wide energy range, from a few GeV to a few tens of PeV. In view of the growing field of time-domain astronomy, it is increasingly crucial to be able to identify neutrinos in real-time. This online neu- trino sample will serve to trigger neutrino alerts that will be sent to the astronomy community and to look for time/space coincidence around external electromagnetic and multi-messenger triggers. These real-time searches can significantly increase the discovery potential of transient cosmic accelerators and refine the pointing directions in the case of poorly localized triggers, such as gravitational waves. In the field of core-collapse supernovae (CCSN), the detection of the MeV- scale CCSN neutrinos is crucial as an early warning. KM3NeT’s digital optical modules act as good detectors for these neutrinos. This proceeding presents the status of KM3NeT’s real-time multi-messenger activities, including supernova monitoring, online event reconstruction, event classification and selection, alert distribution, and the first test of the selection on data

KM3NeT Core Collapse Supernovae observation program in standalone and multi-messenger modes

The KM3NeT research infrastructure in the Mediterranean is a multi-purpose cubic-kilometre neutrino observatory consisting of two detectors optimised to study cosmic and atmospheric neutrinos between GeV to PeV energies. Additionally, KM3NeT multi-photomultiplier optical modules allow the detection of interaction products from neutrinos with energies of a few MeV by selecting nanosecond coincidences within the photomultipliers of the same module. The distribution of the number of photomultipliers forming a coincidence (multiplicity) for the duration of the supernova emission is used as a proxy of the average neutrino energy. Using an optimised coincidence selection the KM3NeT detectors will be sensitive to supernovae in our Galaxy and beyond. A high number of detected events from a core collapse supernova explosion is expected in KM3NeT thanks to its large effective volume. The measurement of the neutrino light curve properties, such as the light curve start time and the presence of the standing accretion shock instability oscillations is possible with such statistics. Sub-millisecond time synchronisation between KM3NeT detectors allows joint observation. Such a scheme can be also a viable solution to synchronise the KM3NeT telescopes with other detectors aiming to observe neutrino emission from core collapse supernovae through the SNEWS network