1,721,049 research outputs found
"active" drops as phantom models for living cells: A mesoscopic particle-based approach
No full textDrops and biological cells share some morphological features and visco-elastic properties. The modelling of drops by mesoscopic non-atomistic models has been carried out to a high degree of success in recent years. We extend such treatment and discuss a simple, drop-like model to describe the interactions of the outer layer of cells with the surfaces of materials. Cells are treated as active mechanical objects that are able to generate adhesion forces. They appear with their true size and are made of "parcels of fluids" or beads. The beads are described by (very) few quantities/parameters related to fundamental chemical forces such as hydrophilicity and lipophilicity that represent an average of the properties of a patch of material or an area of the cell(s) surface. The investigation of adhesion dynamics, motion of individual cells, and the collective behavior of clusters of cells on materials is possible. In the simulations, the drops become active soft matter objects and different from regular droplets they do not fuse when in contact, their trajectories are not Brownian, and they can be forced "to secrete" molecules, to name some of the properties targeted by the modeling. The behavior that emerges from the simulations allows ascribing some cell properties to their mechanics, which are related to their biological features
Electrochemical Characterization of O2 Metabolism in Isolated Mitochondria Revealed Massive Production of H2O2 Upon ATP Synthase Activation
No full textHydrogen peroxide (H2O2) is a highly reactive compound produced by cells after secondary reactions as a result of the leakage of electrons from the electron transport chain in mitochondria or as a consequence of other enzymatic reactions. This book examines the detection, applications and health implications of hydrogen peroxide. Topics discussed include the ambient conditions of hydrogen peroxide advanced oxidation processes for wastewater treatment; the electrochemical approach to quantify cellular hydrogen peroxide and monitor its release process from living cells; H2O2 signalling and role in inflammation; H2O2 as a useful oxidative stressor to investigate various intracellular events under pathological conditions; uses of hydrogen peroxide in aquaculture; H2O2 in regulating fungal viability and pathogenicity; massive production of H2O2 upon ATP synthase activiation; and H2O2 based green oxidation reactions. (Imprint: Nova
Oxygen Redox Reaction in Ionic Liquid and Ionic Liquid-like Based Electrolytes: A Scanning Electrochemical Microscopy Study
No full textImproving the stability of the cathode interface is one of the critical issues for the development of high-performance Li/O2 batteries. The most critical feature to address is the development of electrolytes that mitigate side reactions that bring about cathode passivation. It is well known that superoxide anion (O2-) formed during O2 reduction plays a critical role. Here, we propose the scanning electrochemical microscopy (SECM) as analytical tool to screen the electrolyte of Li/O2 batteries. We demonstrate that by SECM it is possible to evaluate the stability of O2 - and of the cathode to the passivation process occurring during the oxygen redox reaction. Specifically, we report about a study carried out at glassy carbon electrode in 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and tetraethylene glycol dimethyl ether with LiTFSI, the latter ranging from salt insolvent to solvent-in-salt region
Print-Light-Synthesis of ruthenium oxide thin film electrodes for electrochemical sensing applications
Full text linkPrint-Light-Synthesis (PLS) combines the inkjet printing of a ruthenium precursor ink with the simultaneous photo-induced generation of ruthenium oxide films. During PLS, inkjet-printing generates on conductive as well as insulating substrates micrometer-thin reaction volumes that contain with high precision defined precursor loadings. Upon direct UV light irradiation, the Ru precursor converts to RuO 2 while all other ink components escape in the gas phase. No post PLS processes are required, and the as-obtained RuO 2 films can be immediately used as electrochemical devices. Two-dimensional RuO 2 patterns with micrometric resolution and highlycontrolled ruthenium loadings (few µg/cm 2) are realized. Thin RuO 2 films are generated on insulating substrates, such as polyimide, as well as individual RuO 2 particles on conductive substrates, such as graphene layers. The RuO 2 films are characterized by electron microscopy and spectroscopic techniques. The sensoristic applicability of the PLS-RuO 2 electrodes is demonstrated by potentiometric pH sensing in cell cultures and amperometric detection of L-cysteine. For pH sensing the RuO 2 film electrodes show Nernstian sensitivity. L-cysteine detection of RuO 2-modified graphene electrodes showed an electrocatalytical effect and resulted in the possibility of selectively detecting L-Cysteine also in presence of the interfering compound uric acid. ☆ This article is part of a special issue entitled: '11th SMCBS 2023 Workshop' published in Bioelectrochemistry.GR-LU
Reactive Oxygen Species Produced by Mutated Mitochondrial Respiratory Chains of Entire Cells Monitored Using Modified Microelectrodes
No full textGenetic alterations affecting subunits of the mitochondrial respiratory chain complexes often impair their catalytic activities and result in enhanced production of reactive oxygen species (ROS). An electrochemical setup was employed to quantify mitochondrial ROS production in plasma membrane-permeabilized cellular models of two genetic diseases: the Δcytb cell line bearing a microdeletion in the mitochondrial MT-CYB gene causing a severe encephalomyopathy and the RJ206 cell line, harbouring a pathogenic mutation associated with Leber's hereditary optic neuropathy. The responses of black platinum modified microelectrodes to the most common cellular redox buffers, namely, NADH and glutathione, as well as substrates deriving from the oxidative metabolism of glucose, were investigated; a relatively high sensitivity, although lower than that for ROS, was shown for NADH. Time-resolved amperometric measurements of ROS production upon respiratory chain activation at high NADH/NAD+ ratio revealed a 50 % and 100 % increase of ROS in cells bearing defective complex I and complex III, respectively, as compared to wild type cells
Electrochemical and Surface Characterization of Dense Monolayers Grafted on ITO and Si/SiO2 Surfaces via Tetra (tert‐Butoxy) Tin Linker
No full textIndium tin oxide (ITO) and silicon with a thermally grown SiO2 layer (Si/SiO2) substrates have been functionalized by ferrocene bound through Sn(O)x (x=2 or 3) linkers preliminarly grafted on the surface by reaction of the terminal hydroxyl groups with tetra(tert-butoxy)tin. The two steps modification of the surface was carried out by chemical vapour deposition metathesis reaction producing a self-assembled monolayer of ferrocene. The ITO and Si/SiO2 thus functionalized have been characterized by voltammetric, amperometric, electrochemical impedance spectroscopy and scanning probe microscopy techniques which assessed the formation of a stable and rather compact covalently bound ferrocenyl monolayer with improved electron transfer properties
Local desorption of thiols by scanning electrochemical microscopy: patterning and tuning the reactivity of self-assembled monolayers
No full textSelf-assembled monolayers (SAMs) are widely
used in the field of nanotechnologies and (bio)sensors. The
monolayer surface properties are tailored by employing several
techniques. A large set of SAM post-modification routes
are commonly performed to adapt them to a variety of nanotechnological
and bio-technological studies as well as to several
bio-sensoristic applications. Here, we report a procedure
to locally modify SAMs by electrochemical desorption of
alkanethiols in order to create microsized spots of bare gold
area without affecting the surrounding monolayer stability.
The tip of the scanning electrochemical microscope (SECM)
was employed to draw microstructured pattern according to a
defined geometry. The time stability of the pattern was also
tested. Furthermore, the patterned surface was postfunctionalized
using the same alkanethiol or a ferroceneterminated
thiol, in order to tune the surface reactivity of the
microstructure. The local surface properties, including reactivity
and electron transfer kinetics toward redox mediator
reduction, were characterized by SECM
Glucose Micro-Biosensor For Scanning Electrochemical Microscopy Characterization of Cellular Metabolism in Hypoxic Microenvironments
Full text linkMapping of the metabolic activity of tumor tissues represents a fundamental approach to better identify the tumor type, elucidate metastatic mechanisms and support the development of targeted cancer therapies. The spatially resolved quantification of Warburg effect key metabolites, such as glucose and lactate, is essential. Miniaturized electrochemical biosensors scanned over cancer cells and tumor tissue to visualize the metabolic characteristics of a tumor is attractive but very challenging due to the limited oxygen availability in the hypoxic environments of tumors that impedes the reliable applicability of glucose oxidase–based glucose micro-biosensors. Herein, the development and application of a new glucose micro-biosensor is presented that can be reliably operated under hypoxic conditions. The micro-biosensor is fabricated in a one-step synthesis by entrapping during the electrochemically driven growth of a polymeric matrix on a platinum microelectrode glucose oxidase and a catalytically active Prussian blue type aggregate and mediator. The as-obtained functionalization improves significantly the sensitivity of the developed micro-biosensor for glucose detection under hypoxic conditions compared to normoxic conditions. By using the micro-biosensor as non-invasive sensing probe in Scanning Electrochemical Microscopy (SECM), the glucose uptake by a breast metastatic adenocarcinoma cell line, with an epithelial morphology, is measured
Real-Time Visualization of Endogenous H2O2 Production in Mammalian Spheroids by Electrochemiluminescence
Full text linkTwo-dimensional cell culture may be insufficient when it comes to understanding human disease. The redox behavior of complex, three-dimensional tissue is critical to understanding disease genesis and propagation. Unfortunately, few measurement tools are available for such three-dimensional models to yield quantitative insight into how reactive oxygen species (ROS) form over time. Here, we demonstrate an imaging platform for the real-time visualization of H2O2 formation for mammalian spheroids made of noncancerous human embryonic kidney cells (HEK-293) and metastatic breast cancer cells (MCF-7 and MDA-MB-231). We take advantage of the luminol and H2O2 electrochemiluminescence reaction on a transparent tin-doped indium oxide electrode. The luminescence of this reaction as a function of [H2O2] is linear (R2 = 0.98) with a dynamic range between 0.5 μM to 0.1 mM, and limit of detection of 2.26 ± 0.58 μM. Our method allows for the observation of ROS activity in growing spheroids days in advance of current techniques without the need to sacrifice the sample postanalysis. Finally, we use our procedure to demonstrate how key ROS pathways in cancerous spheroids can be up-regulated and downregulated through the addition of common metabolic drugs, rotenone and carbonyl cyanide-p-trifluoromethoxyphenylhydrazone. Our results suggest that the Warburg Effect can be studied for single mammalian cancerous spheroids, and the use of metabolic drugs allows one to implicate specific metabolic pathways in ROS formation. We expect this diagnostic tool to have wide applications in understanding the real-time propagation of human disease in a system more closely related to human tissue
Local desorption of thiols by scanning electrochemical microscopy: patterning and tuning the reactivity of self-assembled monolayers
No full textSelf-assembled monolayers (SAMs) are widely used in the field of nanotechnologies and (bio)sensors. The monolayer surface properties are tailored by employing several techniques. A large set of SAM post-modification routes are commonly performed to adapt them to a variety of nano-technological and bio-technological studies as well as to several bio-sensoristic applications. Here, we report a procedure to locally modify SAMs by electrochemical desorption of alkanethiols in order to create microsized spots of bare gold area without affecting the surrounding monolayer stability. The tip of the scanning electrochemical microscope (SECM) was employed to draw microstructured pattern according to a defined geometry. The time stability of the pattern was also tested. Furthermore, the patterned surface was post-functionalized using the same alkanethiol or a ferrocene-terminated thiol, in order to tune the surface reactivity of the microstructure. The local surface properties, including reactivity and electron transfer kinetics toward redox mediator reduction, were characterized by SECM
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