Laminin and hyaluronan supplementation of collagen hydrogels enhances endothelial function and tight junction expression on three-dimensional cylindrical microvessel-on-a-chip.

Vasculature-on-chip (VoC) models have become a prominent tool in the study of microvasculature functions because of their cost-effective and ethical production process. These models typically use a hydrogel in which the three-dimensional (3D) microvascular structure is embedded. Thus, VoCs are directly impacted by the physical and chemical cues of the supporting hydrogel.

Protocol for fabricating and characterizing microvessel-on-a-chip for human umbilical vein endothelial cells.

Organ-on-a-chip technologies enable the fabrication of endothelial tissues, so-called microvessels (MVs), which emulate the endothelial barrier function in healthy or disease conditions. In this protocol, we describe the fabrication of perfusable open-chamber style MVs embedded in collagen gels. We then report a simple technology to characterize the MV barrier properties in static or under pressure based on fluorescence confocal imaging.

Asymmetry of tensile versus compressive elasticity and permeability contributes to the regulation of exchanges in collagen gels.

The Starling principle describes exchanges between blood and tissues based on the balance of hydrostatic and osmotic flows. However, the permeation properties of the main constituent of tissues, namely, collagen, in response to the stress exerted by blood pressure remain poorly characterized. Here, we develop an instrument to determine the elasticity and permeability of collagen gels under tensile and compressive stress based on measuring the temporal change in pressure in an air cavity sealed at the outlet of a collagen slab.

Endothelial tissue remodeling induced by intraluminal pressure enhances paracellular solute transport.

The endothelial layers of the microvasculature regulate the transport of solutes to the surrounding tissues. It remains unclear how this barrier function is affected by blood flow-induced intraluminal pressure. Using a 3D microvessel model, we compare the transport of macromolecules through endothelial tissues at mechanical rest or with intraluminal pressure, and correlate these data with electron microscopy of endothelial junctions.

Solute transport in the brain tissue: what are the key biophysical parameters tying and studies together?

The mechanisms of solute transport in brain tissues are still under debate. The medical relevance of this topic has put the blood-brain barrier and the mechanisms of solute transport through the brain parenchyma in the spotlight, notably in the context of brain clearance. In the last decade, the classical view of pure diffusive flow across the brain parenchyma was tested against the recent proposal of an active, convectional fluid flow model known as the glymphatic model.

Microvessel-on-Chip Fabrication for the Modeling of Nanomedicine Transport.

Tumor-on-chip devices are becoming ideal platforms to recreate the particular physiological microenvironment of interest for onco-nanomedicine testing and development. This work presents a strategy to produce a round artificial microvessel on-a-chip device for the study of physiologically relevant nanomedicine transport dynamics. The microchannels have a diameter in the range of the tumor capillaries and a semicircular geometry.

micro-RNA 21 detection with a limit of 2 pM in 1 min using a size-accordable concentration module operated by electrohydrodynamic actuation.

We present a fluorimetry-based technology for micro-RNA-21 (miR-21) sensing based on the concentration of miR-molecular beacon (MB) complexes and flushing of unbound MB. This concentration module consists of a microfluidic channel with the shape of a funnel operated with electrohydrodynamic actuation. We report a limit of detection of 2 pM in less than 1 min for miR-21 alone, and then demonstrate that miR-21 levels, measured in fine needle biopsy samples, from patients with pancreatic cancer correlate with the reference technique of reverse-transcription polymerase chain reaction (RT-PCR).

Technological Challenges and Future Issues for the Detection of Circulating MicroRNAs in Patients With Cancer.

In the era of precision medicine, the success of clinical trials, notably for patients diagnosed with cancer, strongly relies on biomarkers with pristine clinical value but also on robust and versatile analytical technologies to ensure proper patients' stratification and treatment. In this review, we will first address whether plasmatic and salivary microRNAs can be considered as a reliable source of biomarkers for cancer diagnosis and prognosis. We will then discuss the pre-analytical steps preceding miRNA quantification (from isolation to purification), and how such process could be biased and time-consuming.

Complete Set of Elastic Moduli of a Spin-Crossover Solid: Spin-State Dependence and Mechanical Actuation.

Molecular spin crossover complexes are promising candidates for mechanical actuation purposes. The relationships between their crystal structure and mechanical properties remain, however, not well understood. In this study, combining high pressure synchrotron X-ray diffraction, nuclear inelastic scattering, and micromechanical measurements, we assessed the effective macroscopic bulk modulus ( B = 11.

Spatial Analysis of Nanofluidic-Embedded Biosensors for Wash-Free Single-Nucleotide Difference Discrimination.

In this work, we demonstrate that the analysis of spatially resolved nanofluidic-embedded biosensors permits the fast and direct discrimination of single-nucleotide difference (SND) within oligonucleotide sequences in a single step interaction. We design a sensor with a linear dimension much larger than the channel depth in order to ensure that the reaction over the whole sensor is limited by the convection rate. Thus, the targets are fully collected, inducing a nonuniform spatial hybridization profile.

Accelerated Transport of Particles in Confined Channels with a High Roughness Amplitude.

We investigate the pressure-driven transport of particles 200 or 300 nm in diameter in shallow microfluidic channels ∼1 μm in height with a bottom wall characterized by a high roughness amplitude of ∼100 nm. This study starts with the description of an assay to generate cracks in hydrophilic thin polymer films together with a structural characterization of these corrugations. Microfluidic chips of variable height are then assembled on top of these rough surfaces, and the transport of particles is assessed by measuring the velocity distribution function for a set of pressure drops.

A Bistable Microelectromechanical System Actuated by Spin-Crossover Molecules.

We report on a bistable MEMS device actuated by spin-crossover molecules. The device consists of a freestanding silicon microcantilever with an integrated piezoresistive detection system, which was coated with a 140 nm thick film of the [Fe(HB(tz) ) ] (tz=1,2,4-triazol-1-yl) molecular spin-crossover complex. Switching from the low-spin to the high-spin state of the ferrous ions at 338 K led to a reversible upward bending of the cantilever in agreement with the change in the lattice parameters of the complex.