Stress, ageing and their influence on functional, cellular and molecular aspects of the immune system

The immune response is essential for keeping an organism healthy and for defending it from different types of pathogens. It is a complex system that consists of a large number of components performing different functions. The adequate and controlled interaction between these components is necessary for a robust and strong immune response. There are, however, many factors that interfere with the way the immune response functions. Stress and ageing now consistently appear in the literature as factors that act upon the immune system in the way that is often damaging. This review focuses on the role of stress and ageing in altering the robustness of the immune response first separately, and then simultaneously, discussing the effects that emerge from their interplay. The special focus is on the psychological stress and the impact that it has at different levels, from the whole system to the individual molecules, resulting in consequences for physical health

Chemiresistor dopamine sensor based on ultrathin gold nanowires.

Chemiresistor dopamine sensor based on ultrathin gold nanowiresIrina Muratovaa, Yulia G. Mourzinab A. Offenhäusserb and Konstantin MikhelsonaaSt.Petersburg State University, [email protected] Jülich GmbH and Jülich Aachen Research Alliance (JARA)-Fundamentals of Future Information Technology, Jülich, GermanyThe development of various Dopamine (DA) sensors is an expanding area in bio-sensing technology. We describe here a novel NW chemiresistor sensor capable of dopamine quantification within the range 10−8 - 10−5 M. When the size of a metal piece goes down to nano-scale, the specific resistivity of the metal is not constant anymore, and is strongly depending on the interactions of the adsorbate species and the metal surface. The sensor response is based on this effect. The approach is based on earlier results [1]. Chips (Fig. 1) were prepared on a silicon wafer using an e-beam lithography. Each chip contained a number of gold electrodes with spacing of 400, 600, 800 nm, and 1 μm. Next, ultrathin gold nanowires (NWs) were synthesized directly on chips, and then PMMA insulation was applied leaving open only the nanowires as sensing elements (Fig. 2). SEM microphotograph of nanowires is shown in Fig. 3.Current-voltage responses of gold NWs (electrode spacing 800 nm) in dopamine hydrochloride solutions with phosphate buffer pH 7 background are presented in Fig. 4. Dopamine is adsorbed on NWs, and therefore increase of the dopamine concentration causes increase of the NWs resistance which, in turn, manifests itself in decrease of the current/voltage response slope. The effect can be seen clearly already at dopamine concentration of 10−8 M.The response of the sensor (see Fig. 5) is roughly linear vs. log of DA concentration over the range 10−8 - 10−5 M so that the sensor appears promising for biomedical applications. [1] A. Kisner, M. Heggen, D. Mayer, U. Simon, A. Offenhäusser, Y. Mourzina, Probing the effect of surface chemistry on the electrical properties of ultrathin gold nanowire sensors . Nanoscale 6(10), 5146 -5155 (2014) doi: 10.1039/c3nr05927h.Financial support from the St.Petersburg State University (grant 12.38.235.2014) is greatly acknowledged

GOLD NANOWIRE-BASED CHEMIRESISTORS.

GOLD NANOWIRE-BASED CHEMIRESISTORSMuratova I.S.1, Mourzina Y.G.2, Offenhäusser A.2, Mikhelson K.N.11Saint Petersburg State University, Saint Petersburg, Russia2Forschungszentrum Jülich, Jülich, GermanyUltrathin metal nanowires (NWs) with diameter ˂ 10 nm are of interest for various applications, in particular due to high spatial resolution of measurements, high surface area and sensitivity when NWs are used in sensor arrays. This work was focused on the techniques to assemble gold NWs on sensor chips and on the study of the gold NW sensors as chemiresistors.Two techniques were explored: (i) applying pre-synthesized NWs to electrodes using a microfluidic channel (MFC), and (ii) a direct synthesis technique (DST) when NWs were synthesized directly on the electrodes.The sensor chips were prepared on a silicon wafer using e-beam lithography. Each chip contained a number of gold electrodes with spacing of 400, 600, 800 nm, and 1 μm. Next, ultrathin gold NWs (Fig. 1) were deposited on chips using either MFC or DST technique. The latter one ensured much better contact and adhesion of NWs to the electrodes, as compared with MFC technique. PMMA insulation was applied leaving open only NWs as sensing elements (Fig. 2).The resistivity of ultrathin NWs is dependent on adsorption of species on the NW surface, and this is the origin of the chemiresistor response. Therefore, current-voltage measurements were performed in aqueous solutions of halogenides: NaF, NaCl, NaBr, NaI and pyridine over concentration range 10‒5–10‒3 M. Fluoride showed only negligible adsorption, therefore 10‒3 M NaF has been used as a background electrolyte in further measurements. The sensors also showed response to dopamine hydrochloride (DA) in phosphate buffer solution, pH 7. The response is linear vs. log of the DA concentration over the range 10−8 - 10−5 M so that the sensor appears promising for biomedical applications.Financial support from the St.Petersburg State University (grant 12.38.235.2014) is greatly acknowledged

Dopamine Electrochemical Sensors: Potentiometric, Voltammetric and Resistometric

Dopamine Electrochemical Sensors: Potentiometric, Voltammetric and Resistometric.Irina S. Muratovaa, Yulia G. Mourzinab Andreas Offenhäusserb,Liudmila A. Kartsovaa and Konstantin N. MikhelsonaaSt.Petersburg State University, RussiabForschungszentrum Jülich GmbH and Jülich Aachen Research Alliance (JARA)-Fundamentals of Future Information Technology, Jülich, Germany26 Universitetskij Pr., Stary Peterhof, 198504, St.Petersburg, [email protected] development of various dopamine sensors is an expanding area in bio-sensing technology. We compare here three different approaches for the electrochemical sensing of dopamine: potentiometric, with a dopamine-selective electrode in a novel flow-through tubular unit; amperometric, with bare gold electrodes in “barrel”-type cells; and resistometric with ultra-thin gold nanowires (NWs).Potentiometric sensors based on dicyclohexyl-18-crown-6 and potassium tetrakis(p-Cl-phenyl)borate don’t suffer interference from ascorbic and uric acid. The sensors were placed into a narrow flow-through cell with the volume of 1-1.5 ml, thus allowing for relatively small sample volumes. Unfortunately, low selectivity against Na+ and K+ hinders practical use of these sensors.Amperometric mode of measurements with bare gold electrodes allowed for reliable dopamine measurements over the range from 1∙10−7 to 1∙10−3 M with PBS background. However, stirring was needed for the measurements below 1∙10−5 M, and therefore large sample volumes (> 10 ml) were required.“Barrel”-type cells with the volume of 200 μl were developed, and differential pulse voltammetry appeared the most promising measurement mode. The calibration curve obtained was non-linear, but the sensors showed sensitivity to dopamine down to 10−7 M.Adsorption of dopamine on ultra-thin gold nanowires (NWs) causes increase of the NWs resistance and the respective decrease of the current/voltage response slope. The response of the sensor is roughly linear vs. log of dopamine concentration over the range from 10−8 to 10−5 M.All in all, use of NWs chemiresistors appears the most promising approach for the dopamine quantification. However, a lot must be done to make these sensors robust in the real-world applications

On “resistance overpotential” caused by a potential drop along the ultrathin high aspect ratio gold nanowire electrodes in cyclic voltammetry

High aspect ratio ultrathin (d < 10 nm) gold nanowires deposited on Si/SiO2 substrate are used as working electrodes for measuring cyclic voltammograms (CVs) in aqueous solutions of ferrocenemethanol and potassium hexacyanoferrate. The broadening of the peak separation as compared with that at a solid working electrode is explained as a result of the potential drop (“resistance overpotential”) along nanowires and nanowire network. The change in the CV shape over a sequence of scans is ascribed to a gradual breakup of individual nanowires and the respective transition of the linear diffusion to hemispherical diffusion regularities