Multititration: The New Method for Implementing Ultrasensitive and Quantitative Multiplexed In-Field Immunoassays Despite Cross-Reactivity?

The accurate in-field titration of multiple pathogens is essential to efficiently describe and monitor environmental or biological contamination, isolate, act, and treat adequately. This underscores the requirement of portable, fast, quantitative, and multiplexed detection technologies, which, however, have not been properly developed so far, notably because it has been hindered by the phenomenon of cross-reactivity. In this work, we proposed a new analytical method based on the imaging through a portable device of lanthanide-based nanoparticles (YVO:Eu) for spatially multiplexed detection, relying on a multiparameter analysis, i.

The tetraspanin CD9 controls migration and proliferation of parietal epithelial cells and glomerular disease progression.

The mechanisms driving the development of extracapillary lesions in focal segmental glomerulosclerosis (FSGS) and crescentic glomerulonephritis (CGN) remain poorly understood. A key question is how parietal epithelial cells (PECs) invade glomerular capillaries, thereby promoting injury and kidney failure. Here we show that expression of the tetraspanin CD9 increases markedly in PECs in mouse models of CGN and FSGS, and in kidneys from individuals diagnosed with these diseases.

Ultra-wide range field-dependent measurements of the relaxivity of GdEuVO nanoparticle contrast agents using a mechanical sample-shuttling relaxometer.

The current trend for Magnetic Resonance Imaging points towards higher magnetic fields. Even though sensitivity and resolution are increased in stronger fields, T1 contrast is often reduced, and this represents a challenge for contrast agent design. Field-dependent measurements of relaxivity are thus important to characterize contrast agents.

Differential interaction kinetics of a bipolar structure-specific endonuclease with DNA flaps revealed by single-molecule imaging.

As DNA repair enzymes are essential for preserving genome integrity, understanding their substrate interaction dynamics and the regulation of their catalytic mechanisms is crucial. Using single-molecule imaging, we investigated the association and dissociation kinetics of the bipolar endonuclease NucS from Pyrococcus abyssi (Pab) on 5' and 3'-flap structures under various experimental conditions. We show that association of the PabNucS with ssDNA flaps is largely controlled by diffusion in the NucS-DNA energy landscape and does not require a free 5' or 3' extremity.

Multifunctional rare-Earth vanadate nanoparticles: luminescent labels, oxidant sensors, and MRI contrast agents.

Collecting information on multiple pathophysiological parameters is essential for understanding complex pathologies, especially given the large interindividual variability. We report here multifunctional nanoparticles which are luminescent probes, oxidant sensors, and contrast agents in magnetic resonance imaging (MRI). Eu(3+) ions in an yttrium vanadate matrix have been demonstrated to emit strong, nonblinking, and stable luminescence.

Regulation of the ROS response dynamics and organization to PDGF motile stimuli revealed by single nanoparticle imaging.

Although reactive oxygen species (ROS) are better known for their harmful effects, more recently, H2O2, one of the ROS, was also found to act as a secondary messenger. However, details of spatiotemporal organization of specific signaling pathways that H2O2 is involved in are currently missing. Here, we use single nanoparticle imaging to measure the local H2O2 concentration and reveal regulation of the ROS response dynamics and organization to platelet-derived growth factor (PDGF) signaling.

Receptor displacement in the cell membrane by hydrodynamic force amplification through nanoparticles.

We introduce an intrinsically multiplexed and easy to implement method to apply an external force to a biomolecule and thus probe its interaction with a second biomolecule or, more generally, its environment (for example, the cell membrane). We take advantage of the hydrodynamic interaction with a controlled fluid flow within a microfluidic channel to apply a force. By labeling the biomolecule with a nanoparticle that acts as a kite and increases the hydrodynamic interaction with the fluid, the drag induced by convection becomes important.

Amplification and temporal filtering during gradient sensing by nerve growth cones probed with a microfluidic assay.

Nerve growth cones (GCs) are chemical sensors that convert graded extracellular cues into oriented axonal motion. To ensure a sensitive and robust response to directional signals in complex and dynamic chemical landscapes, GCs are presumably able to amplify and filter external information. How these processing tasks are performed remains however poorly known.

Biological applications of rare-earth based nanoparticles.

Biomedicine and cell and molecular biology require powerful imaging techniques of the single molecule scale to the whole organism, either for fundamental science or diagnosis. These applications are however often limited by the optical properties of the available probes. Moreover, in cell biology, the measurement of the cell response with spatial and temporal resolution is a central instrumental problem.

A mechanism for the polarity formation of chemoreceptors at the growth cone membrane for gradient amplification during directional sensing.

Accurate response to external directional signals is essential for many physiological functions such as chemotaxis or axonal guidance. It relies on the detection and amplification of gradients of chemical cues, which, in eukaryotic cells, involves the asymmetric relocalization of signaling molecules. How molecular events coordinate to induce a polarity at the cell level remains however poorly understood, particularly for nerve chemotaxis.

Single europium-doped nanoparticles measure temporal pattern of reactive oxygen species production inside cells.

Low concentrations of reactive oxygen species, notably hydrogen peroxide (H(2)O(2)), mediate various signalling processes in the cell. Production of these signals is highly regulated and a suitable probe is needed to measure these events. Here, we show that a probe based on a single nanoparticle can quantitatively measure transient H(2)O(2) generation in living cells.

Asymmetric redistribution of GABA receptors during GABA gradient sensing by nerve growth cones analyzed by single quantum dot imaging.

During development of the nervous system, the tip of a growing axon, the growth cone (GC), must respond accurately to stimuli that direct its growth. This axonal navigation depends on extracellular concentration gradients of numerous guidance cues, including GABA. GCs can detect even weak directional signals, yet the mechanisms underlying this sensitivity remain unclear.

Single quantum dot tracking of membrane receptors.

The dynamics of membrane proteins in living cells has become a major issue to understand important biological questions such as chemotaxis, synaptic regulation, or signal transduction. The advent of semi-conductor quantum dots (QDs) has opened new perspectives for the study of membrane properties because these new nanomaterials enable measurements at the single molecule level with high signal-to-noise ratio. Probes used until now indeed encounter significant limitations: organic fluorophores and fluorescent proteins rapidly photobleach, whereas gold particles and latex beads, although more stable, are bulky and usually stain only one protein per experiment.

Tracking individual proteins in living cells using single quantum dot imaging.

Single quantum dot imaging is a powerful approach to probe the complex dynamics of individual biomolecules in living systems. Due to their remarkable photophysical properties and relatively small size, quantum dots can be used as ultrasensitive detection probes. They make possible the study of biological processes, both in the membrane or in the cytoplasm, at a truly molecular scale and with high spatial and temporal resolutions.

Transient directed motions of GABA(A) receptors in growth cones detected by a speed correlation index.

Single-molecule tracking of membrane proteins has become an important tool for investigating dynamic processes in live cells, such as cell signaling, membrane compartmentation or trafficking. The extraction of relevant parameters, such as interaction times between molecular partners or confinement-zone sizes, from the trajectories of single molecules requires appropriate statistical methods. Here we report a new tool, the speed correlation index, designed to detect transient periods of directed motion within trajectories of diffusing molecules.

DNA unzipped under a constant force exhibits multiple metastable intermediates.

Single molecule studies, at constant force, of the separation of double-stranded DNA into two separated single strands may provide information relevant to the dynamics of DNA replication. At constant applied force, theory predicts that the unzipped length as a function of time is characterized by jumps during which the strands separate rapidly, followed by long pauses where the number of separated base pairs remains constant. Here, we report previously uncharacterized observations of this striking behavior carried out on a number of identical single molecules simultaneously.