Papers by Olivier FRANCAIS
New Journal of Physics, Dec 9, 2008
HAL (Le Centre pour la Communication Scientifique Directe), Jun 12, 2018
HAL (Le Centre pour la Communication Scientifique Directe), Apr 27, 2017
Real-time monitoring of the physiological state of plants using Electrical Impedance Spectroscopy... more Real-time monitoring of the physiological state of plants using Electrical Impedance Spectroscopy (EIS) may help to optimize their need for watering in order for them to efficiently contribute to urban cooling. This paper presents first results obtained from continuous EIS acquisition during 9 days, applied on a celery stalk, in order to follow it physiological stage. A Cole-Cole modeling is used in order to extract parameter evolution versus time or mass loss of the plant. As a first result, a link is established between the curve shape obtained and the celery stalk tampering.
HAL (Le Centre pour la Communication Scientifique Directe), Oct 23, 2022
Thanks to their membrane elasticity and fluidity, red blood cells (RBCs) are capable to pass thro... more Thanks to their membrane elasticity and fluidity, red blood cells (RBCs) are capable to pass through the smallest microcapillaries while exchanging oxygen and CO2 with organs. For several blood disorders like sickle cells disease (SCD), RBCs lose their deformability leading to vaso-occlusions. To assess the deformability of RBC, successive mechanical stresses are applied in our device mimicking blood microcapillaries network, while RBCs circulating being monitored optically by microscopy. Normal and sickled RBCs behaviors are compared using such approach. This device could be a promising tool for the diagnostic of different blood disorders.
International journal of molecular sciences, Jan 4, 2015
Electrical properties of living cells have been proven to play significant roles in understanding... more Electrical properties of living cells have been proven to play significant roles in understanding of various biological activities including disease progression both at the cellular and molecular levels. Since two decades ago, many researchers have developed tools to analyze the cell's electrical states especially in single cell analysis (SCA). In depth analysis and more fully described activities of cell differentiation and cancer can only be accomplished with single cell analysis. This growing interest was supported by the emergence of various microfluidic techniques to fulfill high precisions screening, reduced equipment cost and low analysis time for characterization of the single cell's electrical properties, as compared to classical bulky technique. This paper presents a historical review of single cell electrical properties analysis development from classical techniques to recent advances in microfluidic techniques. Technical details of the different microfluidic tech...
This paper presents a novel electrorotation device composed of double-layer electrode array. Two ... more This paper presents a novel electrorotation device composed of double-layer electrode array. Two electrode layers are formed on the top and bottom of thick dielectric (SU-8) pillars and are electrically connected by through-the-SU-8 vias (TSSV). This unique structure electrically fixes vertical height of cells subjected to electro-rotational (ROT) test, which has been the critical issue. All components of electrodes are formed on a single substrate. This makes cells introducing procedure easy (pipetting from above) and thus microfluidic structure is not required. This allows us to locate electrodes two-dimensionally and densely. Therefore, the proposed device realizes reliable and high-throughput electrorotation analyses.
This paper presents a new electrorotation (ROT) device composed of thick walls and multi-electrod... more This paper presents a new electrorotation (ROT) device composed of thick walls and multi-electrode layers, called as mille-feuille electrode device. The proposed device has three advantages: (1) The height of a measured particle is controllable by adjusting levitation forces. (2) The rotation of the particle is not affected by the friction to the substrates. (3) The number of electrode layers is extensible.
Biosensors and Bioelectronics, Nov 1, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Biosensors and Bioelectronics, Aug 1, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Data in Brief, Apr 1, 2018
Haematologica, Aug 27, 2020
V aso-occlusive crises are the hallmark of sickle cell disease (SCD). They are believed to occur ... more V aso-occlusive crises are the hallmark of sickle cell disease (SCD). They are believed to occur in two steps, starting with adhesion of deformable low-dense red blood cells (RBC), or other blood cells such as neutrophils, to the wall of post-capillary venules, followed by trapping of denser RBC or leukocytes in the areas of adhesion because of reduced effective lumen-diameter. In SCD, RBC are heterogeneous in terms of density, shape, deformability and surface proteins, which accounts for the differences observed in their adhesion and resistance to shear stress. Sickle RBC exhibit abnormal adhesion to laminin mediated by Lu/BCAM protein at their surface. This adhesion is triggered by Lu/BCAM phosphorylation in reticulocytes but such phosphorylation does not occur in mature dense RBC despite firm adhesion to laminin. In this study, we investigated the adhesive properties of sickle RBC subpopulations and addressed the molecular mechanism responsible for the increased adhesion of dense RBC to laminin in the absence of Lu/BCAM phosphorylation. We provide evidence for the implication of oxidative stress in post-translational modifications of Lu/BCAM that impact its distribution and cis-interaction with glycophorin C at the cell surface activating its adhesive function in sickle dense RBC.
Blood Advances, Sep 10, 2019
Specific phosphorylation events are associated with RBC deformation. • Inhibition of GSK3 and Lyn... more Specific phosphorylation events are associated with RBC deformation. • Inhibition of GSK3 and Lyn impairs RBC capacity to undergo successive deformation and resist shear stress. The capacity to undergo substantial deformation is a defining characteristic of the red blood cell (RBC), facilitating transit through the splenic interendothelial slits and microvasculature. Establishment of this remarkable property occurs during a process of reticulocyte maturation that begins with egress through micron-wide pores in the bone marrow and is completed within the circulation. The requirement to undertake repeated cycles of deformation necessitates that both reticulocytes and erythrocytes regulate membrane-cytoskeletal protein interactions in order to maintain cellular stability. In the absence of transcriptional activity, modulation of these interactions in RBCs is likely to be achieved primarily through specific protein posttranslational modifications, which at present remain undefined. In this study, we use high-throughput methods to define the processes that underlie the response to deformation and shear stress in both reticulocytes and erythrocytes. Through combination of a bead-based microsphiltration assay with phosphoproteomics we describe posttranslational modification of RBC proteins associated with deformation. Using microsphiltration and microfluidic biochip-based assays, we explore the effect of inhibiting kinases identified using this dataset. We demonstrate roles for GSK3 and Lyn in capillary transit and maintenance of membrane stability following deformation and show that combined inhibition of these kinases significantly decreases reticulocyte capacity to undergo repeated deformation. Finally, we derive a comprehensive and integrative phosphoproteomic dataset that provides a valuable resource for further mechanistic dissection of the molecular pathways that underlie the RBC's response to mechanical stimuli and for the study of reticulocyte maturation.
Scientific Reports, Aug 26, 2016
Human adipose mesenchymal stem cells (haMSCs) are multipotent adult stem cells of great interest ... more Human adipose mesenchymal stem cells (haMSCs) are multipotent adult stem cells of great interest in regenerative medicine or oncology. They present spontaneous calcium oscillations related to cell cycle progression or differentiation but the correlation between these events is still unclear. Indeed, it is difficult to mimic haMSCs spontaneous calcium oscillations with chemical means. Pulsed electric fields (PEFs) can permeabilise plasma and/or organelles membranes depending on the applied pulses and therefore generate cytosolic calcium peaks by recruiting calcium from the external medium or from internal stores. We show that it is possible to mimic haMSCs spontaneous calcium oscillations (same amplitude, duration and shape) using 100 μs PEFs or 10 ns PEFs. We propose a model that explains the experimental situations reported. PEFs can therefore be a flexible tool to manipulate cytosolic calcium concentrations. This tool, that can be switched on and off instantaneously, contrary to chemicals agents, can be very useful to investigate the role of calcium oscillations in cell physiology and/or to manipulate cell fate.
Scientific Reports, Jun 17, 2020
This paper describes the use of a microfluidic device comprising channels with dimensions mimicki... more This paper describes the use of a microfluidic device comprising channels with dimensions mimicking those of the smallest capillaries found in the human microcirculation. The device structure, associated with a pair of microelectrodes, provides a tool to electrically measure the transit time of red blood cells through fine capillaries and thus generate an electrical signature for red blood cells in the context of human erythroid genetic disorders, such as sickle cell disease or hereditary spherocytosis, in which red cell elasticity is altered. Red blood cells from healthy individuals, heated or not, and red blood cells from patients with sickle cell disease or hereditary spherocytosis where characterized at a single cell level using our device. Transit time and blockade amplitude recordings were correlated with microscopic observations, and analyzed. The link between the electrical signature and the mechanical properties of the red blood cells is discussed in the paper, with greater transit time and modified blockade amplitude for heated and pathological red blood cells as compared to those from healthy individuals. Our single cell-based methodology offers a new and complementary approach to characterize red cell mechanical properties in human disorders under flow conditions mimicking the microcirculation. Red blood cells (RBCs) are the most abundant and simple type of blood cells whose main role is fulfilling the gas exchange to deliver oxygen to the tissues. Human RBCs are biconcave and flexible discs with an average diameter of 6-8 µm and a thickness of 2 µm. They lack nucleus and organelles and have a specific membrane composition and organization that enables them to deform and squeeze through the microcirculatory system 1. However, under certain pathophysiological conditions, these properties are altered triggering changes in the deformability and survival rate of circulating RBCs, as observed in several human disorders like sickle cell disease and hereditary spherocytosis 2. Sickle cell disease (SCD) is a genetic hereditary disorder caused by a single point mutation in the β-globin gene, generating an abnormal hemoglobin (HbS) that polymerizes under hypoxic conditions leading to the sickling and alteration of circulating red cells 3. The hallmarks of sickle cell disease are hemolytic anemia and painful vaso-occlusive crises because of the obstruction of fine capillaries 4,5. In SCD, RBC properties are severely altered, with increased cellular dehydration, rigidity and fragility 6,7. Hereditary spherocytosis (HS) is the most prevalent cause of hemolytic anemia due to genetic mutations in membrane or cytoskeletal proteins that disturb the structural and morphological stability of the RBC altering its biconcave shape and plasticity. HS RBCs are recognized by their spherical shape and extreme fragility, and are mainly trapped in the spleen, leading to decreased cell life span and resultant anemia 8 .
Algal Research-Biomass Biofuels and Bioproducts, 2019
Electroporation is investigated as a possible means to facilitate the extraction of valuable comp... more Electroporation is investigated as a possible means to facilitate the extraction of valuable compounds from microalgae. In addition, reversible or irreversible pores on the cell membrane can be obtained by changing the PEF conditions. In this paper, we discuss the impact of PEF parameters (pulse duration, ranging from 5 to 500 μs, and electrical field amplitude, values up to 7 kV•cm −1) and biomass characteristics (cell concentration, physiology) on the treatment efficiency and energy demand to induce reversible and irreversible permeabilization. Though similar levels of maximum reversible and irreversible permeabilization were obtained for all PEF conditions, the lowest energy demand and temperature increase were found for the lowest pulse duration (5 μs) tested. To better characterize microalgae electroporation, pore characterization (size and resealing time) was assessed. Pores with a maximum radius ranging from 0.8 to 0.9 nm reseal in few seconds, and do not affect cell division capability.
Procedia Engineering, 2016
This work presents an original approach to sense the lipid intracellular content of microalgae, b... more This work presents an original approach to sense the lipid intracellular content of microalgae, by the Radio Frequency (RF) dielectric spectral characterization of these unicellular organisms. To do so, a "homemade" openended coaxial sensor was associated to a Vector Network Analyzer (VNA), which allowed a broadband characterization in the frequency range from 30 MHz to 3 GHz. The sensor combines a coaxial line with a modified SMA connector. This study shows that the lipid quantification can be determined with the complex dielectric spectra properties extracted from the reflection coefficient (S 11) measurement. A calibration of the open-ended coaxial probe is performed by using three different conditions (vacuum, water, methanol) from which the complex dielectric behavior is mastered. A model inversion is finally achieved to estimate the complex permittivity spectrum of the biological samples in a large frequency range, which is related to the microalgae lipid content.
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Papers by Olivier FRANCAIS