Effect of Ionic Strength, Nanoparticle Surface Charge Density, and Template Diameter on Self-Limiting Single-Particle Placement: A Numerical Study

Currents carried by Ba2+ through calcium channels were recorded in the whole-cell configuration in isolated frog sympathetic neurons. The effect of surface charge on the apparent saturation of the channel with Ba2+ was examined by varying [Ba2+]o and ionic strength. The current increased with [Ba2+]o, and the I-V relation and the activation curve shifted to more positive voltages. The shift of activation could be described by Gouy-Chapman theory, with a surface charge density of 1 e-/140 A2, calculated from the Grahame equation. Changes in ionic strength (replacing N-methyl-D-glucamine with sucrose) shifted the activation curve as expected for a surface charge density of 1 e-/85 A2, in reasonable agreement with the value from changing [Ba2+]o. The instantaneous I-V for fully activated channels also changed with ionic strength, which could be described either by a low surface charge density (less than 1 e-/1,500 A2), or by block by NMG with Kd approximately 300 mM (assuming no surface charge). We conclude that the channel permeation mechanism sees much less surface charge than the gating mechanism. The peak inward current saturated with an apparent Kd = 11.6 mM for Ba2+, while the instantaneous I-V saturated with an apparent Kd = 23.5 mM at 0 mV. This discrepancy can be explained by a lower surface charge near the pore, compared to the voltage sensor. After correction for a surface charge near the pore of 1 e-/1,500 A2, the instantaneous I-V saturated as a function of local [Ba2+]o, with Kd = 65 mM. These results suggest that the channel pore does bind Ba2+ in a saturable manner, but the current-[Ba2+]o relationship may be significantly affected by surface charge.

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INFLUENCE OF SURFACE PRETREATMENT ON THE SURFACE CHARGE DENSITY AT THE INTERFACE BETWEEN MCT MBE AND AL3 ALD

Автометрия ◽

10.15372/aut20200506 ◽

2020 ◽

Keyword(s):

Charge Density ◽

Surface Charge ◽

Surface Charge Density ◽

Surface Pretreatment

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Mapping Surface Charge Distribution of Single-Cell via Charged Nanoparticle

Cells ◽

10.3390/cells10061519 ◽

2021 ◽

Vol 10 (6) ◽

pp. 1519

Author(s):

Leixin Ouyang ◽

Rubia Shaik ◽

Ruiting Xu ◽

Ge Zhang ◽

Jiang Zhe

Keyword(s):

Cell Surface ◽

Charge Density ◽

Surface Charge ◽

Charge Distribution ◽

Surface Charge Density ◽

Single Cells ◽

Fluorescent Light ◽

Fluorescent Nanoparticles ◽

Cell Surface Charge ◽

Surface Charge Distribution

Many bio-functions of cells can be regulated by their surface charge characteristics. Mapping surface charge density in a single cell’s surface is vital to advance the understanding of cell behaviors. This article demonstrates a method of cell surface charge mapping via electrostatic cell–nanoparticle (NP) interactions. Fluorescent nanoparticles (NPs) were used as the marker to investigate single cells’ surface charge distribution. The nanoparticles with opposite charges were electrostatically bonded to the cell surface; a stack of fluorescence distribution on a cell’s surface at a series of vertical distances was imaged and analyzed. By establishing a relationship between fluorescent light intensity and number of nanoparticles, cells’ surface charge distribution was quantified from the fluorescence distribution. Two types of cells, human umbilical vein endothelial cells (HUVECs) and HeLa cells, were tested. From the measured surface charge density of a group of single cells, the average zeta potentials of the two types of cells were obtained, which are in good agreement with the standard electrophoretic light scattering measurement. This method can be used for rapid surface charge mapping of single particles or cells, and can advance cell-surface-charge characterization applications in many biomedical fields.

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Triboelectrification of nanocomposites using identical polymer matrixes with different concentrations of nanoparticle fillers

Journal of Materials Chemistry A ◽

10.1039/d0ta12441a ◽

2021 ◽

Author(s):

Linards Lapčinskis ◽

Artis Linarts ◽

Kaspars Mālnieks ◽

Hyunseung Kim ◽

Kristaps Rubenis ◽

...

Keyword(s):

Charge Density ◽

Surface Charge ◽

Surface Charge Density ◽

Polymer Layers

In this study, we investigate triboelectrification in polymer-based nanocomposites using identical polymer matrixes containing different concentrations of nanoparticles (NPs). The triboelectric surface charge density on polymer layers increased as the...

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