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Register a new userNanoelectrodes for intracellular measurements of reactive oxygen and nitrogen species in single living cells
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Reactive oxygen and nitrogen species (ROS and RNS) play important roles in various physiological processes (e.g., phagocytosis) and pathological conditions (e.g., cancer). The primary ROS/RNS, viz., hydrogen peroxide, peroxynitrite ion, nitric oxide, and nitrite ion, can be oxidized at different electrode potentials and therefore detected and quantified by electroanalytical techniques. Nanometer-sized electrochemical probes are especially suitable for measuring ROS/RNS in single cells and cellular organelles. In this article, we survey recent advances in localized measurements of ROS/RNS inside single cells and discuss several methodological issues, including optimization of nanoelectrode geometry, precise positioning of an electrochemical probe inside a cell, and interpretation of electroanalytical data.
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We present an electrophoretic platform based on 3D hollow nanoelectrodes capable of controlling and quantifying the intracellular delivery of single nanoparticles in single selected cells by surface-enhanced Raman spectroscopy (SERS). The gold-coated hollow nanoelectrode has a sub-femtoliter inner volume that allows the confinement and enhancement of electromagnetic fields upon laser illumination to distinguish the SERS signals of a single nanoparticle flowing through the nanoelectrode. The tight wrapping of cell membranes around the nanoelectrodes enables effective membrane electroporation such that single gold nanorods are delivered into a living cell with a delivery rate subject to the applied bias voltage. The capability of the 3D hollow nanoelectrodes to porate cells and reveal single emitters from the background under live flow is promising for the analysis of both intracellular delivery and sampling.
Clusters appear in nature in a diversity of contexts, involving distances as long as the cosmological ones, and down to atoms and molecules and the very small nuclear size. They also appear in several other scenarios, in particular in biological systems as in ants, bees, birds, fishes, gnus and rats, for instance. Here we describe a model composed of a set of female and male individuals that obeys simple rules that rapidly transform an uniform initial state into a single cluster that evolves in time as a stable dynamical structure. We show that the center of mass of the structure moves as a random walk, and that the size of the cluster engenders a power law behavior in terms of the number of individuals in the system. Moreover, we also examine other possibilities, in particular the case of two distinct species that can evolve to form one or two distinct clusters.
The nonequilibrium activity taking place in a living cell can be monitored with a tracer embedded in the medium. While microrheology experiments based on optical manipulation of such probes have become increasingly standard, we put forward a number of experiments with alternative protocols that, we claim, will provide new insight into the energetics of active fluctuations. These are based on either performing thermodynamic--like cycles in control-parameter space, or on determining response to external perturbations of the confining trap beyond simple translation. We illustrate our proposals on an active itinerant Brownian oscillator modeling the dynamics of a probe embedded in a living medium.
Trajectories of endosomes inside living eukaryotic cells are highly heterogeneous in space and time and diffuse anomalously due to a combination of viscoelasticity, caging, aggregation and active transport. Some of the trajectories display switching between persistent and anti-persistent motion while others jiggle around in one position for the whole measurement time. By splitting the ensemble of endosome trajectories into slow moving sub-diffusive and fast moving super-diffusive endosomes, we analyzed them separately. The mean squared displacements and velocity auto-correlation functions confirm the effectiveness of the splitting methods. Applying the local analysis, we show that both ensembles are characterized by a spectrum of local anomalous exponents and local generalized diffusion coefficients. Slow and fast endsomes have exponential distributions of local anomalous exponents and power law distributions of generalized diffusion coefficients. This suggests that heterogeneous fractional Brownian motion is an appropriate model for both fast and slow moving endosomes. This article is part of a Special Issue entitled: Recent Advances In Single-Particle Tracking: Experiment and Analysis edited by Janusz Szwabinski and Aleksander Weron.
A very small number of biomaterials investigated for bone regeneration was reported as able to prevent the oxidative stress. In this study beads based on alginate hydrogel and mesoporous glasses (MG) containing different amounts of cerium oxides (Ce3+/Ce4+) exhibiting antioxidant properties were investigated as a good approach to mimic the action of antioxidant enzymes in our organism. The effect of cerium contents on the bioactivity and biocompatibility of beads were investigated. Moreover, the potential capability of Ce-containing MG to prevent the oxidative stress caused by the activity of reactive oxygen species (ROS) was here investigated for the first time. The increment of cerium oxide from 1.2, to 3.6 and 5.3 mol-% decreases the surface area and porosity of MG and increases the catalase mimetic activity after 168 h. Swelling tests in different cell culture media (D- and {alpha}-MEM) demonstrated the rehydration capability of beads. The presence of beads with the highest Ce-contents (3.6 and 5.3 %) improved the proliferation of pre-osteoblastic cells MC3T3-C1 cells. However, the cell differentiation decreased when increased the cerium content. Lactate dehydrogenase assays showed beads are cytocompatible materials. Moreover, oxidative stress tests with H2O2 showed a better response related to cell viability and the elimination of oxidant species when increased cerium content. Beads of glasses with 1.2 and 3.6 % of CeO2 are excellent candidates as bioactive scaffolds for bone regeneration capable of counteract the oxidative stress.
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