Blood cell - vessel wall interactions probed by reflection interference contrast microscopy

Numerous biophysical questions require the quantification of short-range interactions between (functionalized) surfaces and synthetic or biological objects such as cells. Here, we present an original, custom built setup for reflection interference contrast microscopy that can assess distances between a substrate and a flowing object at high speed with nanometric accuracy. We demonstrate its use to decipher the complex biochemical and mechanical interplay regulating blood cell homing at the vessel wall in the microcirculation using an in vitro approach. We show that in the absence of specific biochemical interactions, flowing cells are repelled from the soft layer lining the vessel wall, contributing to red blood cell repulsion in vivo. In contrast, this so-called glycocalyx stabilizes rolling of cells under flow in the presence of a specific receptor naturally present on activated leucocytes and a number of cancer cell lines

Development of a selective cell capture and release assay: impact of clustered RGD ligands

There is a growing interest in isolating tumor cells from biological samples. Considering that circulating tumor cells can be rare in blood, it appears challenging to capture these cells onto a surface with high selectivity and sensitivity. In the present paper, we describe the design of functionalized surfaces aimed at selectively capturing tumor cells by using an RGD peptide ligand with either a tetrameric or a monomeric presentation. β-Cyclodextrin-coated self-assembled monolayers were used as platforms for the binding of RGD ligands endowed with a redox ferrocene cluster. The dissociation of the inclusion complex on the surface accounts for the release of the captured cells upon the electrochemical oxidation of ferrocene. For this purpose, we determined suitable RGD densities for both monovalent and tetravalent ligand presentations. The results indicate that the clustered RGD architecture efficiently improves selective cell capture at a very low RGD surface density (∼10 RGD per μm2) compared to the monovalent presentation (∼1000 RGD per μm2)

Negative SPR Signals during Low Molecular Weight Analyte Recognition

International audienc

Surface modification of synthetic clay aimed at biomolecule adsorption: synthesis and characterization

This work describes the process for functionalization of laponite through the grafting of 3-mercaptopropyltrimethoxysilane (MPTS). Laponite is synthetic smectite clay with surface area of 350 m²/g. The samples, prior to and after functionalization, were characterized by chemical analyses, thermogravimetric analysis (TGA), x ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), scanning electron microscopy and energy dispersive spectrometry (MEV/EDS). Infrared spectroscopy and elemental analyses confirmed the presence of organic chains and thiol groups in the modified clay. The immobilized and available thiol group, measured according to the Volhard method, totaled 1.4 meq/g of clay, with approximately 90% accessible for Ag+ trapping. These results represent an improvement as compared to other works concerning the functionalization of smectite-type clays in which the effect produced by functional group blockage limits the access of species to less than 10% of the complexing sites

Towards a Versatile Photoreactive Platform for Biosensing Applications

International audienc