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The enhanced and direct immobilization of the enzyme horseradish peroxidase on poly(methyl methacrylate) (PMMA) microchannel surfaces to create a miniaturized enzymatic reactor for the biocatalytic oxidation of phenols is demonstrated. Enzyme immobilization occurs by physical adsorption after oxygen plasma treatment, which micro-nanotextures the PMMA surfaces. A five-fold enhancement in immobilized enzyme activity was observed, attributed to the increased surface area and, therefore, to a higher quantity of immobilized enzymes compared to an untreated PMMA surface. The enzymatic reaction yield reached 75% using a flow rate of 2.0 μL/min for the reaction mixture. Additionally, the developed microreactor was reused more than 16 times without affecting the enzymatic conversion yield. These results demonstrate the potential of microchannels with plasma micro/nanotextured surfaces for the rapid and facile fabrication of microfluidic enzymatic microreactors with enhanced catalytic activity and stability. [ABSTRACT FROM AUTHOR]

Bone marrow has raised a great deal of scientific interest, since it is responsible for the vital process of hematopoiesis and is affiliated with many normal and pathological conditions of the human body. In recent years, organs-on-chips (OoCs) have emerged as the epitome of biomimetic systems, combining the advantages of microfluidic technology with cellular biology to surpass conventional 2D/3D cell culture techniques and animal testing. Bone-marrow-on-a-chip (BMoC) devices are usually focused only on the maintenance of the hematopoietic niche; otherwise, they incorporate at least three types of cells for on-chip generation. We, thereby, introduce a BMoC device that aspires to the purely in vitro generation and maintenance of the hematopoietic niche, using solely mesenchymal stem cells (MSCs) and hematopoietic stem and progenitor cells (HSPCs), and relying on the spontaneous formation of the niche without the inclusion of gels or scaffolds. The fabrication process of this poly(dimethylsiloxane) (PDMS)-based device, based on replica molding, is presented, and two membranes, a perforated, in-house-fabricated PDMS membrane and a commercial poly(ethylene terephthalate) (PET) one, were tested and their performances were compared. The device was submerged in a culture dish filled with medium for passive perfusion via diffusion in order to prevent on-chip bubble accumulation. The passively perfused BMoC device, having incorporated a commercial poly(ethylene terephthalate) (PET) membrane, allows for a sustainable MSC and HSPC co-culture and proliferation for three days, a promising indication for the future creation of a hematopoietic bone marrow organoid. [ABSTRACT FROM AUTHOR]

Legionella pneumophila has been pinpointed by the World Health Organization as the highest health burden of all waterborne pathogens in the European Union and is responsible for many disease outbreaks around the globe. Today, standard analysis methods (based on bacteria culturing onto agar plates) need several days (~12) in specialized analytical laboratories to yield results, not allowing for timely actions to prevent outbreaks. Over the last decades, great efforts have been made to develop more efficient waterborne pathogen diagnostics and faster analysis methods, requiring further advancement of microfluidics and sensors for simple, rapid, accurate, inexpensive, real-time, and on-site methods. Herein, a lab-on-a-chip device integrating sample preparation by accommodating bacteria capture, lysis, and DNA isothermal amplification with fast (less than 3 h) and highly sensitive, colorimetric end-point detection of L. pneumophila in water samples is presented, for use at the point of need. The method is based on the selective capture of viable bacteria on on-chip-immobilized and -lyophilized antibodies, lysis, the loop-mediated amplification (LAMP) of DNA, and end-point detection by a color change, observable by the naked eye and semiquantified by computational image analysis. Competitive advantages are demonstrated, such as low reagent consumption, portability and disposability, color change, storage at RT, and compliance with current legislation. [ABSTRACT FROM AUTHOR]

A novel approach for multisensing has been developed based on the integration of a parallel-channel microfluidic module with a surface acoustic wave (SAW) sensor chip. The microfluidic module was used to compartmentalize the surface of a single SAW sensor into N equal subareas in order to deliver and detect multiple samples on the sensor. The design concerns and fabrication procedure using soft lithography of polydimethyisiloxane are described. Successful demonstration of a four-channel module is reported, along with a sensitivity evaluation and comparison with a standard flow cell used so far. Very promising results were revealed during the tests concerning the system's operation with liquid samples. The reliability and reproducibility of the results in all four subareas render the proposed setup very suitable for biological testing and screening of various biomolecules in an array format. Index Terms--Microfluidics, polydimethylsiloxane (PDMS), soft lithography, surface acoustic waves (SAWs).

The issue of controlled modification of the surface topography of polydimethylsiloxane (PDMS) when subjected to oxygen-based plasma treatments is addressed. The resulting enhanced surface area is investigated as a means of controlling the surface wetting properties.

Long‐lasting underwater superhydrophobicity involves stable‐in‐time air layer trapped and retained between a submersed surface and the overlying liquid. Due to its underwater nature, it is rather difficult to accurately observe this air layer in submerged systems, let alone to measure it. Here, white light reflectance spectroscopy is used for real‐time monitoring (acquisition speed 50–200 ms) of underwater superhydrophobicity as well as for the calculation of the entrapped air layer thickness on "everlasting" underwater polymeric superhydrophobic surfaces fabricated by plasma micro‐nanotexturing. The proposed method enables real‐time monitoring and accurate calculation of air layers with thicknesses ranging from a few nanometers to several tens of micrometers involving small underwater bubbles. In addition, different scale topographies of superhydrophobic plasma micro‐nanotextured surfaces are tested and found to retain underwater superhydrophobicity for at least 60 days. As a demonstration, the air layer thickness is also monitored in real time when titrating water with low surface tension liquids. Among several topographies tested, a superhydrophobic surface exhibiting hierarchical topography and a high roughness ratio is able to retain a stable air layer when submersed in liquids with surface tension down to 44 mN m−1. [ABSTRACT FROM AUTHOR]

Two-photon-allowed laser-induced fluorescence of a 10MHz parallel-plate rf discharge facilitates determination of spatial distribution and O2 atom evolution through detection of atomic oxygen. The production of oxygen atoms in the interelectrode space is regular, as revealed by uniform spatial oxygen distribution. The increase in O concentration implies the dependence of production on time, while the decrease in concentration of O indicates a reaction between the O atoms and surface materials in the plasma.

A method which employed two-photon absorption laser-induced fluorescence was used to achieve spatial distribution of H atoms in the rf reactor's interelectrode space. The surface loss coefficients of H atoms that were generated at the sheath boundary ranged from 0.1% to 20%. This method was also used to evaluate real-time and in situ energetic plasma-induced surface alterations.

Absolute H-atom concentration profiles in continuous and pulsed rf discharges were investigated. The results showed that two-photon absorption laser-induced fluorescence in a pure hydrogen rf discharge determined the absolute concentrations of ground state atomic hydrogen. A constant concentration in the region around the center of the discharge was observed. Diffusion originating from the source regions towards the electrode space determined the distribution of the plasma produced hydrogen.