Junction Barrier Research Articles

Schottky contacts on ultra-high-pressure-annealed GaN with high rectification ratio and near-unity ideality factor

We investigate the electrical characteristics of Ni Schottky contacts on n-type GaN films that have undergone ultra-high-pressure annealing (UHPA), a key processing step for activating implanted Mg. Contacts deposited on these films exhibit low rectification and high leakage current compared to contacts on as-grown films. By employing an optimized surface treatment to restore the GaN surface following UHPA, we obtain Schottky contacts with a high rectification ratio of ∼109, a near-unity ideality factor of 1.03, and a barrier height of ∼0.9 eV. These characteristics enable the development of GaN junction barrier Schottky diodes employing Mg implantation and UHPA.

Propionate regulates tight junction barrier by increasing endothelial-cell selective adhesion molecule in human intestinal Caco-2 cells

Regulation of the intestinal barrier is closely associated with intestinal microbial metabolism. This study investigated the role of propionate, a major short-chain fatty acid produced by intestinal microorganisms, in the regulation of the tight junction (TJ) barrier in human intestinal Caco-2 cells. Propionate strengthened TJ barrier integrity, as indicated by decreased permeability to macromolecules and increased transepithelial electrical resistance in Caco-2 cells. DNA microarray analysis revealed that propionate upregulated endothelial cell-selective adhesion molecule (ESAM), a TJ-associated protein, without any increase in other TJ proteins. The upregulation of ESAM was confirmed using quantitative reverse transcription-PCR, immunoblotting, and immunofluorescence analyses. Luciferase promoter analysis demonstrated that propionate induced the transcriptional activation of ESAM. The effects of propionate were sensitive to nilotinib inhibition of NR2C2. Overexpression of human ESAM (hESAM) in canine kidney epithelial MDCK-II cells lowered the permeability to macromolecules in a manner similar to that of propionate-treated Caco-2 cells. hESAM overexpression facilitated calcium-induced assembly of the TJ complex in MDCK-II cells. Taken together, propionate strengthened the intestinal TJ barrier by increasing ESAM levels in Caco-2 cells.

Comparative study on short-circuit and surge current capabilities of 1.2 kV SiC SBD-embedded MOSFETs

This paper presents a comparative study on the short-circuit and surge current withstanding capabilities and the static and turn-on switching characteristics of commercial 1.2 kV SiC Schottky barrier diode (SBD)-embedded metal–oxide–semiconductor field-effect transistors (MOSFETs). The results confirmed that MOSFETs with a larger SBD area ratio had higher leakage current through the SBD during short-circuit transients due to a higher electric field and lattice temperatures as high as roughly 1120 K at the SBD, which resulted in reduced short-circuit withstanding capabilities. It was also found that MOSFETs with a smaller SBD area ratio had reduced surge-current capabilities in embedded SBDs. We conclude that is not due to the small SBD area ratio but to a weak bipolar operation of the Junction Barrier and Schottky rectifiers even in high current regions.

Imaging the breaking of electrostatic dams in graphene for ballistic and viscous fluids.

The charge carriers in a material can, under special circumstances, behave as a viscous fluid. In this work, we investigated such behavior by using scanning tunneling potentiometry to probe the nanometer-scale flow of electron fluids in graphene as they pass through channels defined by smooth and tunable in-plane p-n junction barriers. We observed that as the sample temperature and channel widths are increased, the electron fluid flow undergoes a Knudsen-to-Gurzhi transition from the ballistic to the viscous regime characterized by a channel conductance that exceeds the ballistic limit, as well as suppressed charge accumulation against the barriers. Our results are well modeled by finite element simulations of two-dimensional viscous current flow, and they illustrate how Fermi liquid flow evolves with carrier density, channel width, and temperature.

The role of magnetic sphincter augmentation in the gastroesophageal reflux disease treatment pathway: the gastroenterology perspective.

Magnetic sphincter augmentation (MSA) is a surgical intervention for well-characterized gastroesophageal reflux disease (GERD), where the esophagogastric junction barrier is augmented using a bracelet of magnetized titanium beads. MSA could be an attractive option for patients with documented GERD who wish to avoid long-term pharmacologic therapy or whose symptoms are not adequately managed with lifestyle modifications and pharmacologic therapy. The 'ideal' MSA patient is one with prominent regurgitation, without dysphagia or esophageal motor dysfunction, with objective evidence of GERD on upper endoscopy and/or ambulatory reflux monitoring. Appropriate candidates with significant hiatus hernia may pursue MSA with concomitant hiatus hernia repair. The increasing adoption of MSA in the GERD treatment pathway reflects research that shows benefits in long-term outcomes and healthcare costs compared with other established therapies in appropriate clinical settings.

Organ-on-a-Chip Platform with an Integrated Screen-Printed Electrode Array for Real-Time Monitoring Trans-Epithelial Barrier and Bubble Formation.

Cellular tight junctions play a key role in establishing a barrier between different compartments of the body by regulating the selective passage of different solutes across epithelial and endothelial tissues. Over the past decade, significant efforts have been conducted to develop more clinically relevant "organ-on-a-chip" models with integrated trans-epithelial electrical resistance (TEER) monitoring systems to help better understand the fundamental underpinnings of epithelial tissue physiology upon exposure to different substances. However, most of these platforms require the use of high-cost and time-consuming photolithography processes, which limits their scalability and practical implementation in clinical research. To address this need, we have developed a low-cost microfluidic platform with an integrated electrode array that allows continuous real-time monitoring of TEER and the risk of bubble formation in the microfluidic system by using scalable manufacturing technologies such as screen printing and laser processing. The integrated printed electrode array exhibited excellent stability (with less than ∼0.02 Ω change in resistance) even after long-term exposure to a complex culture medium. As a proof of concept, the fully integrated platform was tested with HMT3522 S1 epithelial cells to evaluate the tight barrier junction formation through TEER measurement and validated with standard immunostaining procedures for Zonula occludens-1 protein. This platform could be regarded as a stepping stone for the fabrication of disposable and low-cost organ and tissue-on-a-chip models with integrated sensors to facilitate studying the dynamic response of epithelial tissues to different substances in more physiologically relevant conditions.

Self‐Assembled Junctions of 2D Single‐Layer Semiconductors: A Potential Way toward Advanced Photocatalysis

Self‐Assembled Junctions of <scp>2D</scp> Single‐Layer Semiconductors: A Potential Way toward Advanced Photocatalysis

Lactobacillus acidophilus Induces Enhancement of the Intestinal Epithelial Tight Junction Barrier Function by Toll-like Receptor-2 Independent of MyD88

A defective intestinal epithelial tight junction (TJ) barrier has been postulated to be a key pathogenic factor in allergic disorders, including food allergy. Enhancement of the TJ barrier might be a target for prevention or treatment of such diseases. Our lab recently showed that Lactobacillus acidophilus (LA) caused an enhancement of the intestinal TJ barrier that was mediated by attachment of live LA to toll-like receptor-2 (TLR2) on the apical membrane surface of enterocytes. The aim of this study was to delineate TLR2 signaling mechanisms mediating the LA-induced enhancement of the intestinal TJ barrier.

DOP68 Autophagy induction in the intestinal epithelium protects against inflammation-induced barrier loss in vivo.

Abstract Background Loss of the paracellular tight junction (TJ) barrier and defective autophagy in the gut are pathogenic factors for inflammatory bowel disease (IBD). Earlier, we demonstrated the role of autophagy in the degradation of the pore-forming claudin-2 protein and the resultant TJ barrier enhancement. Here, we investigated the role of autophagy in the regulation of the TJ barrier in vivo and in Crohn’s disease (CD) patient-derived tissues and patient-derived organoids. Methods Wild type and autophagy-deficient Atg7-/- mice were given intraperitoneal rapamycin injection to induce autophagy along with LPS or TNF-α to induce inflammation. Surgically resected tissues from CD patients were incubated with rapamycin and the paracellular barrier was measured by Ussing chambers. Autophagy was induced in human colonic organoids by incubation with either rapamycin or by nutrient starvation. Results Intraperitoneal rapamycin injection in WT mice successfully induced autophagy as evidenced through the degradation of the autophagy substrate p62/SQSTM. Rapamycin injection increased the colonic occludin levels and enhanced the paracellular TJ barrier as evidenced by the decreasing paracellular flux of inulin. Rapamycin prevented LPS and TNF-a induced colonic paracellular barrier loss and reduction in occludin levels in WT mice. Rapamycin reduced the LPS and TNF-a-induced increase in occludin’s association with caveolin-1 thereby preventing its caveolae-mediated endocytosis and degradation. The protective effect of rapamycin was dependent on autophagy. Conditional knockout of Atg7 (cAtg7) in mouse colon decreased baseline occludin levels and increased inulin flux in mouse colon. Furthermore, rapamycin failed to prevent the LPS and TNF-a-induced colonic barrier loss in the cAtg7 mice. Additionally, these mice lacking the ability to undergo autophagy in the colon were more susceptible to Dextran Sodium Sulphate (DSS)-induced colitis. In normal and inflamed colonic tissues from CD patients, incubation with rapamycin induced autophagy, evidenced through the reduction in p62/SQSTM1 protein levels, increased occludin levels and enhanced the paracellular TJ barrier. Autophagy induction by rapamycin or nutrient starvation also increased occludin levels and its membrane localization in patient-derived organoids. Conclusion Our data show that rapamycin successfully induced autophagy in WT mice’s colon and protected these mice from the barrier disruptive effect of both LPS and TNF-α, indicating the importance of autophagy in regulating the intestinal TJ barrier. Our data also highlights the application of autophagy induction as a potential therapeutic approach in the treatment of IBD.

HC067047 as a potent TRPV4 inhibitor repairs endotoxemia colonic injury

Colonic injury causes severe inflammation during systemic infections in patients with endotoxemia. The prevention of colonic injury could effectively reduce the progression of endotoxemia. We investigated the protective effects and detailed mechanisms of the TRPV4 inhibitor HC067047 in the treatment of colonic injury caused by endotoxemia. An LPS-induced endotoxemia colonic injury model was used to assess the in vivo effects of HC067047. Colon slices were detected by hematoxylin and eosin (HE) staining and immunofluorescence assays. Spectrophotometry was used to determine the levels of MDA, calcium, GSH, and GSSG. Alterations in oxidative stress/mitophagy/inflammatory pyroptosis-related markers were evaluated by Q-PCR and western blot assays. HC067047 reduced the body weight loss and spleen weight index of endotoxemic mice and partly recovered the normal morphology of the colonic mucous layer. As an inhibitor of the calcium permeant cation channel, HC067047 suppressed the phosphorylation of the CAMKIIɑ protein and levels of MDA and calcium, upregulated the ratio of GSH/GSSG, shortened the expression of oxidative stress-related proteins, and enhanced the expression of the anti-oxidative protein CAT in damaged colon tissues. Additionally, HC067047 maintained normal mitochondrial functions in endotoxemia colons by promoting mitochondrial fusion and biosynthesis and suppressing mitochondrial fission and the PINK/Parkin/mitophagy pathway. HC067047 potently blocked inflammatory pyroptosis and protected the colonic tight junction barrier. HC067047 restores endotoxemia colons against oxidative stress, mitophagy, inflammatory pyroptosis, and colonic barrier dysfunction. Hence, HC067047 therapy may be potentially useful in the treatment of colonic injury in endotoxemia.

Green tea extract and Piper retrofractum attenuate deoxycholic acid-induced damage and enhance the tight junction barrier: An analysis in a Caco-2 cell culture model and a DSS coinduced mouse model

This study investigated the effect of green tea extract (GTE) and green tea–Piper retrofractum complex (GPX), on tight junctions (TJs) in a cellular model of deoxycholic acid (DCA)-induced intestinal barrier disruption and a mouse DSS + DCA-induced colitis model. Green tea and P. retrofractum were extracted and coadministered to examine the bioavailability and effects of combined catechins and piperine on colonic TJ damage. The ability of GPX to alleviate TJ damage was determined by comparing the transepithelial electrical resistance (TEER), FITC-dextran flux, and mRNA expression of TJ-related components and target expression pathway in the GTE and GPX groups. Compared with the DCA-treated group, the GTE- and GPX-treated groups showed significantly enhanced TEER, FITC-dextran flux, and TJ-related mRNA expression (p < 0.05). Cell treatment also downregulated the mRNA encoding bile acid receptor and decreased ERK1/2 phosphorylation. Compared with the GTE-treated group, the GPX-treated group showed higher mRNA expression of zonula occludens-1, occludin, claudin-3, and claudin-4; greater restoration of TJs, as determined by immunofluorescence; and better modulation of ERK1/2 activation. In the in vivo model, GPX-pretreated mice showed an improved intestinal damage index and colon length compared with mice in the other colitis-induced groups. Both extracts recovered the distal colon mRNA expression of zonula occludens-1 and claudin-1. These results suggest that GTE improves intestinal health by protecting TJs from secondary bile acid damage and that P. retrofractum may potentiate the bioactivity of green tea catechins.

New Data on the Features of Skin Barrier in Hidradenitis Suppurativa.

Hidradenitis suppurativa (HS) is a Th1/17-driven inflammatory skin disease of the apocrine gland-rich (AGR) skin regions, where keratinocytes seem to be the crucial drivers of the initial pathogenic steps. However, the possible role of permeability barrier alteration in activating keratinocytes during HS development has not been clarified. We compared the major permeability barrier elements of non-lesional HS (HS-NL; n = 10) and lesional HS (HS-L; n = 10) skin with healthy AGR regions (n = 10) via RT-qPCR and immunohistochemistry. Stratum corneum components related to cornified envelope formation, corneocyte desquamation and (corneo)desmosome organization were analyzed along with tight junction molecules and barrier alarmins. The permeability barrier function was also investigated with transepidermal water loss (TEWL) measurements (n = 16). Junction structures were also visualized using confocal microscopy. At the gene level, none of the investigated molecules were significantly altered in HS-NL skin, while 11 molecules changed significantly in HS-L skin versus control. At the protein level, the investigated molecules were similarly expressed in HS-NL and AGR skin. In HS-L skin, only slight changes were detected; however, differences did not show a unidirectional alteration, as KRT1 and KLK5 were detected in decreased levels, and KLK7, KRT6 and DSG1 in increased levels. No significant differences in TEWL or the expression of junction structures were assessed. Our findings suggest that the permeability barrier is not significantly damaged in HS skin and permeability barrier alterations are not the driver factors of keratinocyte activation in this disease.

Advances in solar energy harvesting integrated by van der Waals graphene heterojunctions.

Graphene has garnered increasing attention for solar energy harvesting owing to its unique features. However, limitations hinder its widespread adoption in solar energy harvesting, comprising the band gapless in the molecular orbital of graphene lattice, its vulnerability to oxidation in oxidative environments, and specific toxic properties that require careful consideration during development. Beyond current challenges, researchers have explored doping graphene with ionic liquids to raise the lifespan of solar cells (SCs). Additionally, they have paid attention to optimizing graphene/Si Schottky junction or Schottky barrier SCs by enhancing the conductivity and work function of graphene, improving silicon's reflectivity, and addressing passivation issues at the surface/interface of graphene/Si, resulting in significant advancements in their power conversion efficiency. Increasing the functional area of graphene-based SCs and designing efficient grid electrodes are also crucial for enhancing carrier collection efficiency. Flaws and contaminants present at the interface between graphene and silicon pose significant challenges. Despite the progress of graphene/Si-based photovoltaic cells still needs to catch up to the efficiency achieved by commercially available Si p-n junction SCs. The low Schottky barrier height, design-related challenges associated with transfer techniques, and high lateral resistivity of graphene contribute to this performance gap. To maximize the effectiveness and robustness of graphene/Si-based photovoltaic cells, appropriate interlayers have been utilized to tune the interface and modulate graphene's functionality. This mini-review will address ongoing research and development endeavors using van der Waals graphene heterojunctions, aiming to overcome the existing limitations and unlock graphene's full potential in solar energy harvesting and smart storage systems.

Research Progress of Reverse Monte Carlo and Its Application in Josephson Junction Barrier Layer

Research Progress of Reverse Monte Carlo and Its Application in Josephson Junction Barrier Layer

Analysis of Breakdown-Voltage Increase on SiC Junction Barrier Schottky Diode Under Negative Bias Stress

In this study, the increment in the breakdown voltage of a SiC junction barrier Schottky (JBS) diode under negative bias stress (NBS) is investigated. However, when the SiC JBS exhibits an increase in breakdown voltage after NBS, its forward characteristic does not change. The variation in breakdown voltage increases under a higher stress voltage that is close to the breakdown voltage of SiC JBS without stress. Furthermore, the variation in breakdown voltage increases with a higher compliance current and at lower NBS temperature. The electric field of SiC JBS under NBS is simulated to clarify the variation in breakdown voltage under NBS. The electrical characteristics and the simulation of the electric field under NBS demonstrate that the increase in the breakdown voltage of SiC JBS after NBS is induced by the electron injection in the oxide layer of edge termination.

In vitro and in vivo evaluation of effects of high-purity magnesium on tight junction of intestinal epithelial cell.

After anastomosis of sutures or pins, the restoration of intestinal barrier function can avoid several complications, such as tissue damage and inflammation. Our previous studies demonstrated the feasibility of biodegradable magnesium (Mg) pins as novel anastomosing implants to spontaneously absorb in the body, avoiding secondary removal surgery and long-term inflammation. However, the effect of Mg pins on the intestinal tight junction barrier is rarely investigated. In this study, we conducted high-purity Mg pins inserted in the intestine of rats and prepared Mg extracts cultured intestinal epithelial cell line to investigate the biological effect on the intestinal barrier associated with tight junction protein expression. We discovered that the concentration of released Mg ions over 1.7 mM was the critical threshold, above which mRNA expression of intestinal tight junction and cell apoptosis were affected considerably. Results of the immunohistochemical analysis revealed that Mg functions to stimulate ZO-1, caspase-3, occluding, and claudin-3 expressions. We offer new insight into the effectiveness of biodegradable Mg materials as the next generation of intestinal anastomosis pins, which effectively filters toxins as well as bacteria, and reduces inflammation.

Fundamentals and Applications of ZnO-Nanowire-Based Piezotronics and Piezo-Phototronics.

The piezotronic effect is a coupling effect of semiconductor and piezoelectric properties. The piezoelectric potential is used to adjust the p-n junction barrier width and Schottky barrier height to control carrier transportation. At present, it has been applied in the fields of sensors, human-machine interaction, and active flexible electronic devices. The piezo-phototronic effect is a three-field coupling effect of semiconductor, photoexcitation, and piezoelectric properties. The piezoelectric potential generated by the applied strain in the piezoelectric semiconductor controls the generation, transport, separation, and recombination of carriers at the metal-semiconductor contact or p-n junction interface, thereby improving optoelectronic devices performance, such as photodetectors, solar cells, and light-emitting diodes (LED). Since then, the piezotronics and piezo-phototronic effects have attracted vast research interest due to their ability to remarkably enhance the performance of electronic and optoelectronic devices. Meanwhile, ZnO has become an ideal material for studying the piezotronic and piezo-phototronic effects due to its simple preparation process and better biocompatibility. In this review, first, the preparation methods and structural characteristics of ZnO nanowires (NWs) with different doping types were summarized. Then, the theoretical basis of the piezotronic effect and its application in the fields of sensors, biochemistry, energy harvesting, and logic operations (based on piezoelectric transistors) were reviewed. Next, the piezo-phototronic effect in the performance of photodetectors, solar cells, and LEDs was also summarized and analyzed. In addition, modulation of the piezotronic and piezo-phototronic effects was compared and summarized for different materials, structural designs, performance characteristics, and working mechanisms' analysis. This comprehensive review provides fundamental theoretical and applied guidance for future research directions in piezotronics and piezo-phototronics for optoelectronic devices and energy harvesting.

Photo‐Assisted Barrier Effect for Improving the Sensing Performance to Copper Ions

AbstractCopper ions (Cu2+) pollution poses a serious threat to Marine ecology and fisheries, but the online detection is difficult due to seawater interference. Herein, photo‐assisted barrier effect is introduced into electrochemical detection as a driver to generate electrochemical response. The n–n junction barrier exhibits excellent adjusting effect on electrochemical response under photoexcitation and could effectively drive electrochemical response by Cu2+ adsorption. The prepared Ti/TiO2/In2O3/Chitosan wire is used for direct Cu2+ detection, and the trace detection with the low detection limit (59.08 nm) is achieved. The strong interference of seawater is resisted effectively by using photo‐assisted barrier effect, and the good recovery rate (94.9–107.1%) in the actual seawater detection make it promising for practical applications. It is a new approach to develop electrochemical sensors by using photo‐assisted barrier effect to resist interference.

Lactobacillus fermentum (MTCC-5898) based fermented whey renders prophylactic action against colitis by strengthening the gut barrier function and maintaining immune homeostasis.

Nutritional intervention using probiotic fermented dairy product has emerged as a promising prophylactic strategy to curb inflammatory bowel diseases. Under present investigation, the potential of fermented whey prepared with probiotic Lactobacillus fermentum (LF:MTCC-5898) was investigated on dextran sodium sulfate (DSS) induced impaired intestinal barrier function in mice. Probiotic fermented whey (PFW) consumption improved the symptoms of colitis-associated with intestinal inflammation by significantly (p<0.01) diminishing the percent loss in body weight, disease activity index and spleen index with improved colon length besides hematological and histopathological score. Likewise, pre-treatment with PFW improved the barrier integrity (p<0.01) in contrast to leaky condition induced by DSS administration which increased the FITC-dextran permeability across gut epithelium. PFW consumption also provided the gut immune protection through significantly increased (p<0.05) TLR-2 expression and stimulated T-regulatory response by producing TGF-β (p<0.01) and, potently suppressed (p<0.01) inflammatory response (TNF-α, IL-4 and C-reactive protein). Further, PFW intake significantly enhanced (p<0.05) immunoglobulin (sIgA) secretion and concomitantly restored the Occludin, ZO-1 (p<0.01) and Claudin-1(p<0.05) transcriptional expression as compared to colitis mice. Additionally, immune-fluorescence further established the presence of intact actin cytoskeleton and tight junction proteins (claudin-1, occludin and ZO-1) after PFW consumption. Thus, PFW rectified the impaired and leaky barrier junctions not only through modulation of transcriptional expression of tight junction genes but also with reduced secretion of inflammatory mediators and helped in ameliorating the colitis. Hence, probiotic fermented whey prepared with L.fermentum (MTCC-5898) could be used as potential prophylactic functional food in the prevention of gut ailments.

Cathelicidin LL-37 Activates Human Keratinocyte Autophagy through the P2X₇, Mechanistic Target of Rapamycin, and MAPK Pathways

Human cathelicidin LL-37 is a multifunctional antimicrobial peptide that exhibits antimicrobial and immunomodulatory activities. LL-37 regulates skin barrier function and was recently reported to activate autophagy in macrophages. Because autophagy deficiency is associated with skin diseases characterized by a dysfunctional epidermal barrier, we hypothesized that LL-37 might regulate the skin barrier through autophagy modulation. We showed that LL-37 activated autophagy in human keratinocytes and three-dimensional skin equivalent models as indicated by increases in LC3 puncta formation, decreases in p62, and autophagosome and autolysosome formation. LL-37‒induced autophagy was suppressed by P2X7 receptor, adenosine monophosphate‒activated protein kinase, and unc-51-like kinase 1 inhibitors, suggesting that the P2X7, adenosine monophosphate‒activated protein kinase, and unc-51-like kinase 1 pathways are involved. Moreover, LL-37 enhanced the phosphorylation of adenosine monophosphate‒activated protein kinase and unc-51-like kinase 1. In addition, LL-37‒mediated autophagy involves the mechanistic target of rapamycin and MAPK pathways. Interestingly, the LL-37‒induced distribution of tight junction proteins and improvement in the tight junction barrier were inhibited in autophagy-deficient keratinocytes and keratinocytes and skin models treated with autophagy inhibitors, indicating that the LL-37‒mediated tight junction barrier is associated with autophagy activation. Collectively, these findings suggest that LL-37 is a potential therapeutic target for skin diseases characterized by dysfunctional autophagy and skin barriers.