Papers by Keyword: Ionic Current

Abstract: With the miniaturization of the NEMS/MEMS, the size effect becomes significant in the nanochannels/nanopores through which fluid flows as well as the interface effect. By all-atom molecular dynamics (MD) simulations, the ion transportation is investigated in nanopores as well as the physical properties at solid-liquid interface. To describe the anion and cation distributions of NaCl solution in vicinity of graphene nanopores, a new MD model was developed, taking thermal vibration of wall atoms, the structure of solvent molecules and ion sizes into consideration. The main peak locations of ion distributions stayed unchanged by changing the nanopore size, the solution concentration and the electric field strength. The ionic currents increased linearly with the diameter and the electric field strength, while it increased non-linearly with the solution concentration.

Abstract: Ionic current characterization is critical for the application of nanopores with sub 5 nm as bio medical sensors and devices. Here, we demonstrate an eccentric ionic current behavior in graphene nanopore fabricated by high resolution transmission electron microscopy (HR-TEM). A spike-like current enhancement is shown in the absence of any bio molecule or nanoparticle in the LaCl₃ and KCl solution. By tuning the hydrophobicity of the graphene surface, the spikes diminish in the current recordings acquired in graphene nanopore after 20 seconds plasma etching. We consider that the hydrophocity-induced nanobubble is present in the nanopore area, leading to the currents change as the bubbles deformation due to the voltage driven electrostatic forces on the transported ions surrounding the bubble surface.

Abstract: The heart functions normally when the impulses are produced at a rate of 80 bpm. When less than 60 bpm are triggered, pacemakers may be necessary to sustain the electrical activity of the heart. Pacemaker systems used in cardiac resynchronization therapy are made of an implantable pulse generator, leads, and unipolar or bipolar electrodes. They are aimed to simulate the cardiac depolarization, to sense intrinsic cardiac functions, to provide information stored by the system for deeper diagnosis. This paper presents a mathematical model and numerical simulation results on the ionic current distributed by the electrodes, in the absence of concentration gradients, in the cardiac tissue. The external electrical resistance variation with the anode to cathode spacing obtained by this approach may be used in the design phase of the device.

Abstract: The Whole-cell patch clamp technique was used to study the properties of voltage dependent ion channel expressed by the cultured types A、B、C neurosecretory cells dissociated from medulla terminalis X-organ (MTXO) of Chinese mitten crab Eriocheir sinensis 24-48 hours after plating. Under voltage clamp conditions, significantly inward currents were recorded from all three kinds of neurons, followed by large outward currents. When outward currents were suppressed with use of 3mmol/L 4-aminopyridine (4-AP) and 30mmol/L tetraethylammonium (TEA), a tetrodotoxin-sensitive Na⁺ current （I_Na） and a slow (time to peak current 6~8mS at +10mV), Cd²⁺-sensitive Ca²⁺ current (ICa) were resolved. I_Na was activated at potential-40mV and was maximal at-10mV. In TTX, I_Ca was activated at potential-30mV, was maximal at 10~20mV. In the presence of 1mol/L TTX and 0.5mmol/L Cd²⁺, a 4-AP-sensitive transient current and a slower-rising, TEA-sensitive current were recorded from a holding potential of-50mV. On the basis of electric feature and pharmacology, transient current was identified as I_A, and late, slower-rising current as I_K. I_A and I_K showed the same activation threshold of-30mV. In conclusion, no differences were observed on the properties and kinetics of ionic current among the three kinds of neurons. By comparison with those described in crab Cardisoma carnifex and crayfish Procambarus clarkia, there existed diversity of excitability in X-organ peptidergic neurons from different crustaceans.