arXiv subjects

Florence Gazeau

Publications and source records attributed to Florence Gazeau.

3 recordsLinked to original sources

arXiv2025

Illuminating extracellular vesicles biology with super resolution microscopy: Insights into morphology and composition

Super-Resolution Microscopy (SRM) is emerging as a powerful and innovative tool for imaging, characterizing, and understanding the structure of Extracellular Vesicles (EVs). By addressing the need for single-particle analysis with the high resolution required to study the composition and organization of these nanoparticles, SRM provides unique insights into EV biology. However, its application is accompanied by significant challenges, ranging from experimental setup to data analysis. This review outlines the fundamentals of SRM and its position within the broader field of EV research. We then explore its applications in evaluating (i) the morphological structure of EVs, (ii) their molecular composition, and (iii) their roles in biological systems. By offering practical guidance and an overview of critical parameters for standardization, this review aims at providing researchers with the tools and insights necessary to effectively apply SRM to EV investigation.

physics.bio-ph↗

arXiv2022

Calibrated photoacoustic spectrometer based on a conventional imaging system for in vitro characterization of contrast agents

Photoacoustic (PA) imaging systems are spreading in the biomedical community, and the de-velopment of new PA contrast agents is an active area of research. However, PA contrast agents are usually characterized with spectrophotometry or uncalibrated PA imaging systems, leading to partial assessment of their PA efficiency. To enable quantitative PA spectroscopy of contrast agents in vitro with conventional PA imaging systems, we have developed an adapted calibration method. Contrast agents in solution are injected in a dedicated non-scattering tube phantom imaged at different optical wavelengths. The calibration method uses a reference solu-tion of cupric sulfate to simultaneously correct for the spectral energy distribution of excitation light at the tube location and perform a conversion of the tube amplitude in the image from ar-bitrary to spectroscopic units. The method does not require any precise alignment and provides quantitative PA spectra, even with non-uniform illumination and ultrasound sensitivity. It was implemented on a conventional imaging setup based on a tunable laser operating between 680 nm and 980 nm and a 5 MHz clinical ultrasound array. We demonstrated robust calibrated PA spectroscopy with sample volumes as low as 15 μL of known chromophores and commonly used contrast agents. The validated method will be an essential and accessible tool for the de-velopment of new and efficient PA contrast agents by improving their quantitative characterization.

physics.ins-det↗

arXiv2005

Controlled Clustering of Superparamagnetic Nanoparticles using Block Copolymers : Design of New Contrast Agents for Magnetic Resonance Imaging

When polyelectrolyte-neutral block copolymers are mixed in aqueous solutions with oppositely charged species, stable complexes are found to form spontaneously. The mechanism is based on electrostatics, and on the compensation between the opposite charges. Electrostatic complexes exhibit a core-shell microstructure. In the core, the polyelectrolyte blocks and the oppositely charged species are tightly bound and form a dense coacervate microphase. The shell is made of the neutral chains and surrounds the core. In this paper, we report on the structural and magnetic properties of such complexes made from 6.3 nm diameter superparamagnetic nanoparticles (maghemite gamma-Fe2O3) and cationic-neutral copolymers. The copolymers investigated are poly(trimethylammonium ethylacrylate methylsulfate)-b-poly(acrylamide), with molecular weights 5000-b-30000 gmol-1 and 110000-b-30000 gmol-1. The mixed copolymer-nanoparticle aggregates were characterized by a combination of light scattering and cryo-transmission electron microscopy. Their hydrodynamic diameters were found in the range 70 - 150 nm and their aggregation numbers (number of nanoparticles per aggregate) between several tens to several hundreds. In addition, Magnetic Resonance Spin-Echo measurements show that the complexes have a better contrast in Magnetic Resonance Imaging than single nanoparticles, and that these complexes could be used for biomedical applications.

cond-mat.soft↗