Nanoscopic Characterization of Cell Migration under Flow Using Optical and Electron Microscopy.

Hematopoietic stem/progenitor cell (HSPC) and leukemic cell homing is an important biological phenomenon that takes place through essential interactions with adhesion molecules on an endothelial cell layer. The homing process of HSPCs begins with the tethering and rolling of the cells on the endothelial layer, which is achieved by the interaction between selectins on the endothelium to the ligands on HSPC/leukemic cells under shear stress of the blood flow. Although many studies have been based on in vitro conditions of the cells rolling over recombinant proteins, significant challenges remain when imaging HSPC/leukemic cells on the endothelium, a necessity when considering characterizing cell-to-cell interaction and rolling dynamics during cell migration. Here, we report a new methodology that enables imaging of stem-cell-intrinsic spatiotemporal details during its migration on an endothelium-like cell monolayer. We developed optimized protocols that preserve transiently appearing structures on HSPCs/leukemic cells during its rolling under shear stress for fluorescence and scanning electron microscopy characterization. Our new experimental platform is closer to in vivo conditions and will contribute to indepth understanding of stem-cell behavior during its migration and cell-to-cell interaction during the process of homing.

Single Cell Microwave Biosensor for Monitoring Cellular Response to Electrochemotherapy.

This paper presents a 40 GHz microwave biosensor used to monitor and characterize single cells (THP-1) subjected to electrochemotherapy and obtain an electronic signature of the treatment efficiency. This biosensor proposes a non-destructive and label-free technique that first allows, with the rapid measurement of single untreated cells in their culture medium, the extraction of two frequency-dependent dielectric parameters, the capacitance (C (f)) and the conductance (G (f)). Second, this technique can powerfully reveal the effects of a chemical membrane permeabilizing treatment (Saponin). At last, it permits us to detect, and predict, the potentiation of a molecule classically used in chemotherapy (Bleomycin) when combined with the application of electric pulses (principle of electrochemotherapy). Treatment-affected cells show a decrease in the capacitive and conductive contrasts, indicating damages at the cellular levels. Along with these results, classical biological tests are conducted. Statistical analysis points out a high correlation rate (R2>0.97), which clearly reveals the reliability and efficacy of our technique and makes it an attractive technique for biology related researches and personalized medicine.