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Aberrant functioning of the proteasome has been associated with crucial pathologic conditions including neurodegeneration. Yet, the complex underlying causes at the cellular level remain unclear and there are conflicting reports of neuroprotective to neurodegenerative effects of proteasomal inhibitors such as lactacystin that are utilised as models for neurodegenerative diseases. The conflicting results may be associated with different dose regimes of lactacystin and hence we have performed a dose dependent study of the effects of lactacystin to identify concurrent changes in the cell membrane lipid profile and the dynamics of exocytosis using a combination of surface sensitive mass spectrometry and single cell amperometry. Significant changes of negatively charged lipids were associated with different lactacystin doses that showed a weak correlation with exocytosis while changes in PE and PE−O lipids showed dose dependent changes correlated with initial pore formation and total release of vesicle content respectively. [ABSTRACT FROM AUTHOR]

Aberrant functioning of the proteasome has been associated with crucial pathologic conditions including neurodegeneration. Yet, the complex underlying causes at the cellular level remain unclear and there are conflicting reports of neuroprotective to neurodegenerative effects of proteasomal inhibitors such as lactacystin that are utilised as models for neurodegenerative diseases. The conflicting results may be associated with different dose regimes of lactacystin and hence we have performed a dose dependent study of the effects of lactacystin to identify concurrent changes in the cell membrane lipid profile and the dynamics of exocytosis using a combination of surface sensitive mass spectrometry and single cell amperometry. Significant changes of negatively charged lipids were associated with different lactacystin doses that showed a weak correlation with exocytosis while changes in PE and PE−O lipids showed dose dependent changes correlated with initial pore formation and total release of vesicle content respectively. [ABSTRACT FROM AUTHOR]

We report the discovery that in the presence of chaotropic anions (SCN−) the opening of nanometer biological vesicles at an electrified interface often becomes a two‐step process (around 30 % doublet peaks). We have then used this to independently count molecules in each subvesicular compartment, the halo and protein dense‐core, and the fraction of catecholamine binding to the dense‐core is 68 %. Moreover, we differentiated two distinct populations of large dense‐core vesicles (LDCVs) and quantified their content, which might correspond to immature (43 %) and mature (30 %) LDCVs, to reveal differences in their biogenesis. We speculate this is caused by an increase in the electrostatic attraction between protonated catecholamine and the negatively charged dense‐core following adsorption of SCN−. [ABSTRACT FROM AUTHOR]

We report the discovery that in the presence of chaotropic anions (SCN−) the opening of nanometer biological vesicles at an electrified interface often becomes a two‐step process (around 30 % doublet peaks). We have then used this to independently count molecules in each subvesicular compartment, the halo and protein dense‐core, and the fraction of catecholamine binding to the dense‐core is 68 %. Moreover, we differentiated two distinct populations of large dense‐core vesicles (LDCVs) and quantified their content, which might correspond to immature (43 %) and mature (30 %) LDCVs, to reveal differences in their biogenesis. We speculate this is caused by an increase in the electrostatic attraction between protonated catecholamine and the negatively charged dense‐core following adsorption of SCN−. [ABSTRACT FROM AUTHOR]

The dopaminergic system has been suggested to serve as a functional target for ketamine, especially with its addictive and antidepressant effects. In this work, intracellular vesicle impact electrochemical cytometry and single cell amperometry were applied to a model cell line to show that the intravesicular contents and number of exocytotic events increased and the fraction of release decreased after treatment by subanesthetic ketamine (1 μM for 15 min). In addition, time‐of‐flight secondary ion mass spectrometry was used to show that cellular lipids change following acute ketamine administration relative to control cells with an increased proportion of low‐curvature lipids and a decreased proportion of high‐curvature lipids. We propose that ketamine modulates dopaminergic function with a dose‐dependent pharmacologic action by dominantly interacting with different proteins and changing lipid composition. It might be helpful to better understand the relationship of the dopaminergic system and drug abuse, as well as anesthetic and antidepressant effects. [ABSTRACT FROM AUTHOR]

Abstract: A nonintuitive observation of monovalent anion‐induced ion current rectification inversion at polyimidazolium brush (PimB)‐modified nanopipettes is presented. The rectification inversion degree is strongly dependent on the concentration and species of monovalent anions. For chaotropic anions (for example, ClO4−), the rectification inversion is easily observed at a low concentration (5 m m), while there is no rectification inversion observed for kosmotropic anions (Cl−) even at a high concentration (1  m). Moreover, at the specific concentration (for example, 10 m m), the variation of rectification ratio on the type of anions is ranged by Hofmeister series (Cl−≥NO3−>BF4−>ClO4−>PF6−>Tf2N−). Estimation of the electrokinetic charge density (σek) demonstrates that rectification inversion originates from the charge inversion owing to the over‐adsorption of chaotropic monovalent anion. To qualitatively understand this phenomenon, a concentration‐dependent adsorption mechanism is proposed. [ABSTRACT FROM AUTHOR]

Abstract: A nonintuitive observation of monovalent anion‐induced ion current rectification inversion at polyimidazolium brush (PimB)‐modified nanopipettes is presented. The rectification inversion degree is strongly dependent on the concentration and species of monovalent anions. For chaotropic anions (for example, ClO4−), the rectification inversion is easily observed at a low concentration (5 m m), while there is no rectification inversion observed for kosmotropic anions (Cl−) even at a high concentration (1  m). Moreover, at the specific concentration (for example, 10 m m), the variation of rectification ratio on the type of anions is ranged by Hofmeister series (Cl−≥NO3−>BF4−>ClO4−>PF6−>Tf2N−). Estimation of the electrokinetic charge density (σek) demonstrates that rectification inversion originates from the charge inversion owing to the over‐adsorption of chaotropic monovalent anion. To qualitatively understand this phenomenon, a concentration‐dependent adsorption mechanism is proposed. [ABSTRACT FROM AUTHOR]

Development of new principles for fabrication of novel ionic devices has attracted much attention due to the potential applications of ionic devices in molecular computer, biosensing and electronic circuit. Inspired by optogenetics altering membrane voltage via light-controlled proteins, a new kind of light-controlled ionic switch was demonstrated here based on nanopipettes. Upon exposure to visible light, spiropyran (SP) does not coordinate with Zn2+, resulting in a relatively large ionic current. While, upon UV light irradiation, SP was transformed into merocyanine (MC) that coordinates with Zn2+ and thereby results in the decrease in the ionic current. The ionic current could be reversibly modulated by UV/Vis light irradiation. The finite-element simulation was performed to understand the possible mechanism underlying the light-controlled ionic switch based on nanopipettes. [ABSTRACT FROM AUTHOR]

We report the discovery that in the presence of chaotropic anions (SCN−) the opening of nanometer biological vesicles at an electrified interface often becomes a two‐step process (around 30 % doublet peaks). We have then used this to independently count molecules in each subvesicular compartment, the halo and protein dense‐core, and the fraction of catecholamine binding to the dense‐core is 68 %. Moreover, we differentiated two distinct populations of large dense‐core vesicles (LDCVs) and quantified their content, which might correspond to immature (43 %) and mature (30 %) LDCVs, to reveal differences in their biogenesis. We speculate this is caused by an increase in the electrostatic attraction between protonated catecholamine and the negatively charged dense‐core following adsorption of SCN−. [ABSTRACT FROM AUTHOR]

Nanoplastics are recently recognized as neurotoxic factors for the nervous systems. However, whether and how they affect vesicle chemistry (i.e., vesicular catecholamine content and exocytosis) remains unclear. This study offers the first direct evidence for the nanoplastics‐induced neurotoxicity by single‐vesicle electrochemistry. We observe the cellular uptake of polystyrene (PS) nanoplastics into model neuronal cells and mouse primary neurons, leading to cell viability loss depending on nanoplastics exposure time and concentration. By using single‐vesicle electrochemistry, we find the reductions in the vesicular catecholamine content, the frequency of stimulated exocytotic spikes, the neurotransmitter release amount of single exocytotic event, and the membrane‐vesicle fusion pore opening‐closing speed. Mechanistic investigations suggest that PS nanoplastics can cause disruption of filamentous actin (F‐actin) assemblies at cytomembrane zones and change the kinetic patterns of vesicle exocytosis. Our finding shapes the first quantitative picture of neurotoxicity induced by high‐concentration nanoplastics exposure at a single‐cell level. [ABSTRACT FROM AUTHOR]

Nanoplastics are recently recognized as neurotoxic factors for the nervous systems. However, whether and how they affect vesicle chemistry (i.e., vesicular catecholamine content and exocytosis) remains unclear. This study offers the first direct evidence for the nanoplastics‐induced neurotoxicity by single‐vesicle electrochemistry. We observe the cellular uptake of polystyrene (PS) nanoplastics into model neuronal cells and mouse primary neurons, leading to cell viability loss depending on nanoplastics exposure time and concentration. By using single‐vesicle electrochemistry, we find the reductions in the vesicular catecholamine content, the frequency of stimulated exocytotic spikes, the neurotransmitter release amount of single exocytotic event, and the membrane‐vesicle fusion pore opening‐closing speed. Mechanistic investigations suggest that PS nanoplastics can cause disruption of filamentous actin (F‐actin) assemblies at cytomembrane zones and change the kinetic patterns of vesicle exocytosis. Our finding shapes the first quantitative picture of neurotoxicity induced by high‐concentration nanoplastics exposure at a single‐cell level. [ABSTRACT FROM AUTHOR]