Monolayer System Research Articles

Enhancement of hydrogen storage using functionalized MoSe2/Graphene monolayer and bilayer systems: DFT study

Utilizing the spin-polarized density-functional theory (DFT), we present an investigation of the adsorption properties of hydrogen-gas molecules on ten different substrates, which are based upon defected and TM-doped MoSe2 monolayer (ML) and MoSe2/graphene bilayer (BL) systems (TM = Ni, Cu). Particularly, Ni, and Cu substitutional doping at Se site showed distinct high H2 uptake capacity and thus to be good candidates for H2 storage. On these latter catalysts, H2 molecule exhibited physisorption with moderate respective energies Eads = −0.307 and −0.362 eV, attributed to the enhancement in electric dipole moment and spin splitting (magnetism) induced in the substrate. The desorption processes of the H2 molecule are found to cost energies of about 0.46 and 0.44 eV, respectively. Moreover, the H2 molecule can move parallel to the substrate after crossing potential barriers of 0.56 and 0.65 eV, respectively. Furthermore, the gravimetric uptake density can further be improved by increasing the dopants concentrations. For instance, by increasing the number of Ni dopants from one to two atoms in the computational sample 4 × 4 PCs of MoSe2 ML, the gravimetric density raises from 1.28 wt% to 3.6 wt% (almost triple). This should corroborate the candidacy of TM-doped @Se MoSe2 for hydrogen storage applications. PAC Numbers31.15.E; 68.43.-h; 68.43.Mn; 68.65.Pq; 73.43.Cd; 75.70.Rf.

Rational design of Two-Dimensional Buckled-Hexagonal Nb2S2 monolayer as an efficient anode material for Ca-ion Batteries: A First-Principles study

Presently, great attention is being paid to the search for promising anode materials for metal-ion batteries (MIBs) due to the rapid evolution of numerous modern electronic gadgets. In this investigation, we have predicted for the first time that the buckled-hexagonal Nb2S2 monolayer which may be an efficient anode material for calcium-ion batteries (CIBs). To that objective, we have explored the pristine monolayer system’s energetical, dynamical, and thermal stability. The inherent metallicity of the pristine monolayer facilitates its electrical conductivity as an electrode material. Our study also reveals the structural and electrical properties of the Ca-adsorbed Nb2S2 monolayer. It is observed that Ca-atoms prefer to get intercalated on top of the buckled hexagon of the pristine monolayer, and the metallicity of the 2D nanosheet remains preserved. In the adsorption process, Bader charge analysis is used to determine the amount of charge transfer from the Ca atom to the Nb2S2 monolayer. Furthermore, this system exhibits a high storage capacity of 1288.86 mAh/g and a moderately low diffusion energy barrier of 0.76 eV. The calculated open-circuit voltage of 0.49 V and the other results suggest that the Nb2S2 monolayer may be a potential candidate for anode material for rechargeable Ca-ion batteries.

Establishment of a 96-well transwell system using primary human gut organoids to capture multiple quantitative pathway readouts

Disruptions in the gut epithelial barrier can lead to the development of chronic indications such as inflammatory bowel disease (IBD). Historically, barrier function has been assessed in cancer cell lines, which do not contain all human intestinal cell types, leading to poor translatability. To bridge this gap, we adapted human primary gut organoids grown as monolayers to quantify transcription factor phosphorylation, gene expression, cytokine production, and barrier function. In this work we describe and characterize a novel 96-well human gut organoid-derived monolayer system that enables quantitative assessment of candidate therapeutics. Normal human intestine differentiation patterns and barrier function were characterized and confirmed to recapitulate key aspects of in vivo biology. Next, cellular response to TNF-α (a central driver of IBD) was determined using a diverse cadre of quantitative readouts. We showed that TNF-α pathway antagonists rescued damage caused by TNF-α in a dose-dependent manner, indicating that this system is suitable for quantitative assessment of barrier modulating factors. Taken together, we have established a robust primary cell-based 96-well system capable of interrogating questions around mucosal response. This system is well suited to provide pivotal functional data to support translational target and drug discovery efforts.

Cellular and molecular antiproliferative effects in 2D monolayer and 3D-cultivated HT-29 cells treated with zerumbone.

Zerumbone (ZER) is a phytochemical isolated from plants of the Zingiberaceae family. Numerous studies have demonstrated its diverse pharmacological properties, particularly its potent antitumorigenic activity. This study aimed to assess the antiproliferative effects of ZER on HT-29 cells cultivated in both two-dimensional (2D) monolayer and three-dimensional (3D) spheroid culture systems. The evaluation of growth (size), cell death, and cell cycle arrest in 3D spheroid HT-29 cells was correlated with mRNA expression data. Treatment of 2D cells revealed that ZER exhibited cytotoxicity at concentrations above 30 µM, and an IC50 of 83.54 µM (24-h post-ZER treatment) effectively suppressed cell migration. In the 3D model, ZER induced an increase in spheroid volume over a 72-h period attributed to disaggregation and reconfiguration of characteristic zones. Analysis of cell death demonstrated a significant rise in apoptotic cells after 24 h of ZER treatment, along with cell cycle arrest in the G1 phase. Furthermore, ZER treatment resulted in alterations in mRNA expression, affecting key signaling pathways involved in cell death (BCL2 and BBC3), endoplasmic reticulum stress (ERN1), DNA damage (GADD45A), cell cycle regulation (CDKN1A, NFKB1, MYC, and TP53), and autophagy (BECN1 and SQSTM1). These findings suggested that ZER holds promise as a potential candidate for the development of novel anticancer agents that can modulate crucial cell signaling pathways. Additionally, the use of the 3D culture system proved to be a valuable tool in our investigation.

Ex vivo drug sensitivity screening predicts response to temozolomide in glioblastoma patients and identifies candidate biomarkers

BackgroundPatient-derived glioma stem-like cells (GSCs) have become the gold-standard in neuro-oncological research; however, it remains to be established whether loss of in situ microenvironment affects the clinically-predictive value of this model. We implemented a GSC monolayer system to investigate in situ-in vitro molecular correspondence and the relationship between in vitro and patient response to temozolomide (TMZ).MethodsDNA/RNA-sequencing was performed on 56 glioblastoma tissues and 19 derived GSC cultures. Sensitivity to TMZ was screened across 66 GSC cultures. Viability readouts were related to clinical parameters of corresponding patients and whole-transcriptome data.ResultsTumour DNA and RNA sequences revealed strong similarity to corresponding GSCs despite loss of neuronal and immune interactions. In vitro TMZ screening yielded three response categories which significantly correlated with patient survival, therewith providing more specific prediction than the binary MGMT marker. Transcriptome analysis identified 121 genes related to TMZ sensitivity of which 21were validated in external datasets.ConclusionGSCs retain patient-unique hallmark gene expressions despite loss of their natural environment. Drug screening using GSCs predicted patient response to TMZ more specifically than MGMT status, while transcriptome analysis identified potential biomarkers for this response. GSC drug screening therefore provides a tool to improve drug development and precision medicine for glioblastoma.

Electronic structure and physical properties of the monolayer Kagome lattice system AV3Sb5 (A = K, Rb, Cs)

In this study, we employ density functional theory to investigate the electronic structure and physical properties of the monolayer Kagome lattice system of AV3Sb5 (A = K, Rb, Cs). Our results reveal that charge density wave (CDW) states are present not only in the bulk, but also in the monolayer systems. Notably, we find that the monolayer system exhibits a higher stability of the CDW states compared to the corresponding bulk system. Additionally, we find that external pressure can induce the instability of the CDW states, driving the pristine structure to a stable phase. Our band unfolding and phonon calculations also provide additional support for these findings. Our study suggests that manipulating the dimensions of Kagome lattice materials as well as applying external pressure can lead to desired physical properties, thereby paving the way for material design advancements in the family of AV3Sb5 Kagome lattice systems.

Generation and metabolomic characterization of functional ductal organoids with biliary tree networks in decellularized liver scaffolds.

Developing functional ductal organoids (FDOs) is essential for liver regenerative medicine. We aimed to construct FDOs with biliary tree networks in rat decellularized liver scaffolds (DLSs) with primary cholangiocytes isolated from mouse bile ducts. The developed FDOs were dynamically characterized by functional assays and metabolomics for bioprocess clarification. FDOs were reconstructed in DLSs retaining native structure and bioactive factors with mouse primary cholangiocytes expressing enriched biomarkers. Morphological assessment showed that biliary tree-like structures gradually formed from day 3 to day 14. The cholangiocytes in FDOs maintained high viability and expressed 11 specific biomarkers. Basal-apical polarity was observed at day 14 with immunostaining for E-cadherin and acetylated α-tubulin. The rhodamine 123 transport assay and active collection of cholyl-lysyl-fluorescein exhibited the specific functions of bile secretion and transportation at day 14 compared to those in monolayer and hydrogel culture systems. The metabolomics analysis with 1075 peak pairs showed that serotonin, as a key molecule of the tryptophan metabolism pathway linked to biliary tree reconstruction, was specifically expressed in FDOs during the whole period of culture. Such FDOs with biliary tree networks and serotonin expression may be applied for disease modeling and drug screening, which paves the way for future clinical therapeutic applications.

α-Synuclein colocalizes with AP180 and affects the size of clathrin lattices

α-Synuclein and family members β- and γ-synuclein are presynaptic proteins that sense and generate membrane curvature, properties important for synaptic vesicle (SV) cycling. αβγ-synuclein triple knockout neurons exhibit SV endocytosis deficits. Here, we investigated if α-synuclein affects clathrin assembly invitro. Visualizing clathrin assembly on membranes using a lipid monolayer system revealed that α-synuclein increases clathrin lattices size and curvature. On cell membranes, we observe that α-synuclein is colocalized with clathrin and its adapter AP180 in a concentric ring pattern. Clathrin puncta that contain both α-synuclein and AP180 were significantly larger than clathrin puncta containing either protein alone. We determined that this effect occurs in part through colocalization of α-synuclein with the phospholipid PI(4,5)P2 in the membrane. Immuno-electron microscopy (EM) of synaptosomes uncovered that α-synuclein relocalizes from SVs to the presynaptic membrane upon stimulation, positioning α-synuclein to function on presynaptic membranes during or after stimulation. Additionally, we show that deletion of synucleins impacts brain-derived clathrin-coated vesicle size. Thus, α-synuclein affects the size and curvature of clathrin structures on membranes and functions as an endocytic accessory protein.

Photogalvanic effect induced charge and spin photocurrent in group-V monolayer systems

Photogalvanic effect induced charge and spin photocurrent in group-V monolayer systems

Hydroethanolic Extract of Fritillariae thunbergii Bulbus Alleviates Dextran Sulfate Sodium-Induced Ulcerative Colitis by Enhancing Intestinal Barrier Integrity.

The incidence of ulcerative colitis (UC), an inflammatory disorder of the gastrointestinal tract, has rapidly increased in Asian countries over several decades. To overcome the limitations of conventional drug therapies, including biologics for UC management, the development of herbal medicine-derived products has received continuous attention. In this study, we evaluated the beneficial effects of a hydroethanolic extract of Fritillariae thunbergii Bulbus (FTB) in a mouse model of DSS-induced UC. The DSS treatment successfully induced severe colonic inflammation and ulceration. However, the severity of colitis was reduced by the oral administration of FTB. Histopathological examination showed that FTB alleviated the infiltration of inflammatory cells (e.g., neutrophils and macrophages), damage to epithelial and goblet cells in the colonic mucosal layer, and fibrotic lesions. Additionally, FTB markedly reduced the gene expression of proinflammatory cytokines and extracellular matrix remodeling. Immunohistochemical analysis showed that FTB alleviated the decrease in occludin and zonula occludens-1 expression induced by DSS. In a Caco-2 monolayer system, FTB treatment improved intestinal barrier permeability in a dose-dependent manner and increased tight junction expression. Overall, FTB has potential as a therapeutic agent through the improvement of tissue damage and inflammation severity through the modulation of intestinal barrier integrity.

Flat bands with high Chern numbers and multiple flat bands in multifold staggered-flux models

Topological flat bands (TFBs) have been proposed in Chern-insulator lattice models. Some two-dimensional monolayer systems can host TFBs with the Chern number $|\mathcal{C}|=1$, and some TFBs with higher Chern numbers are achieved in multilayer or multicomponent systems. In this work, we construct a series of TFBs with higher Chern numbers in the monolayer star lattice by adding several distant-neighbor hopping terms with staggered magnetic fluxes. By considering the third and the fourth nearest-neighbor hopping terms, we find the $|\mathcal{C}|=2$ and $|\mathcal{C}|=3$ TFBs with large flatness ratios, respectively. We also obtain the $|\mathcal{C}|=4$ and $|\mathcal{C}|=5$ TFBs when the fifth and the sixth nearest-neighbor hopping terms are added. Intriguingly, we also observe multiple flat bands with various Chern numbers by tuning the distant-neighbor hopping amplitudes and the staggered-flux parameters. Furthermore, a series of fractional Chern insulator (FCI) states have been numerically observed when hard-core bosons are filled into these TFB models, with fractional fillings $\ensuremath{\nu}=1/3, 2/5, 3/7$ and $\ensuremath{\nu}=1/4, 2/7$ in the $|\mathcal{C}|=2$ and $|\mathcal{C}|=3$ TFBs, respectively. Our findings provide an approach to search for more TFBs with higher Chern numbers and further investigate more interesting FCIs.

Probing the Role of Environmental and Sample Characteristics in Gap Mode Tip-Enhanced Raman Spectroscopy.

Tip-enhanced Raman spectroscopy (TERS) has emerged as a powerful analytical tool for nondestructive and label-free molecular characterization at the nanoscale. However, the influence of environmental factors and sample characteristics on the occurrence of spurious signals, enhancement of TERS signals, and longevity of TERS probes is not well understood yet. Herein, we present a detailed investigation of the influence of oxygen, humidity, and atmospheric carbon contaminants on scanning tunneling microscopy-TERS (STM-TERS) measurements of self-assembled monolayer systems in ambient and inert environments. Our results reveal a consistent increase of TERS signals, significant reduction of spurious signals, and drastically improved longevity of TERS probes in the inert environment. Additionally, sample characteristics such as molecular packing, chemisorption behavior, and hydrophilicity are found to have a direct impact on signal enhancement in the TERS measurements of molecular self-assembled monolayers (SAMs). The novel insights gained in this study are expected to pave the way for a more robust data analysis and improved experimental design in the future gap mode STM- and atomic force microscopy-TERS (AFM-TERS) studies.

Serum-free alginate-C2C12 cells microcapsule as a model of alternative animal protein source.

Due to the climate change crisis, and environmental impacts of the traditional meat sector, the production of artificial animal protein based on in vitro cell culture technology is proposed as an alternative. Furthermore, since traditional animal serum-supplemented cultures pose scientific challenges such as batch variation and contamination risks, artificial animal protein cultures are currently in urgent need of not only serum-free cultures, but also microcarrier culture systems for scalability. However, serum-free microcarrier-based culture system for the differentiation of muscle cells is not available to date. Therefore, we established an edible alginate microcapsules culture system for the differentiation of C2C12 cells in serum-free conditions. Furthermore, metabolites related to central carbon metabolism were profiled based on targeted metabolomics using mass spectrometry. The C2C12 cells cultured in alginate microcapsules displayed high viability throughout 7 days and successfully differentiated within 4 days in serum and serum-free cultures except for AIM-V cultures, which was confirmed by CK activity and MHC immunostaining. Lastly, to the best of our knowledge, this is the first report to compare metabolite profiles between monolayer and alginate microcapsule culture systems. Alginate microcapsule culture showed higher levels of intracellular glycolysis and TCA cycle intermediates, lactate, and the contribution of essential amino acids compared to the monolayer culture. We believe our serum-free alginate microcapsule culture system is adaptable to different species of muscle cells and contributes to future food technology as a proof of concept for the scalability of alternative animal protein source production.

Industrial sludge conversion into biochar and reuse in the context of circular economy: Impact of pre-modification processes on pharmaceuticals removal from aqueous solutions

The present research deals with the global challenge of managing industrial sludge with respect to sustainability and circular economy principles. It focuses on raw industrial sludge (IS-R) conversion into valuable biochars that can serve as efficient adsorbents for pharmaceuticals in industrial wastewater. Three biochars were produced through sludge pyrolysis at 750 °C either without modification (IS-R-B), or after pre-treatment with 1 M solution of ZnCl2 (IS–ZnCl2–B) or FeCl3 (IS–FeCl3–B). Compared to the pristine biochar, the modified sludge-derived biochars (SDBs) showed improved structural, textural, and surface chemical properties. As a result, IS-ZnCl2-B and IS-FeCl3-B had AMX adsorption capacities of 31.9 and 32.1 mg g−1 which were 41.2% and 42.0% higher than the non-modified biochar, respectively. Moreover, both modified SDBs effectively removed AMX under various experimental conditions, including the presence of competitive ions and over a wide pH range. The AMX removal was found to be spontaneous, endothermic, and primarily controlled by chemical reactions on a monolayer system. These findings suggest that biochars generated from pyrolysis of salt-modified industrial sludge can be used as effective materials for removing pharmaceuticals from water. Therefore, this study supports the concepts of circular economy and sustainable development by offering engineering solutions.

Site selective behaviour of B, C and N doping in MgO monolayers towards spintronic and optoelectronic applications

The electronic, magnetic and optical properties of graphene-like MgO monolayers doped with B, C and N atoms in both Mg and O sites are investigated in the framework of density functional theory. The impurity atoms induce magnetism in the host material irrespective of the sites of substitution. The HSE based hybrid DFT calculations show that the wide electronic band gap semiconducting pristine MgO monolayer becomes metallic due to B and C doping in the Mg site of MgO monolayer system (BMg and CMg). However, rests of the doped monolayers remain semiconducting with appearance of impurity states that lowers their energy band gaps compared to the pristine value. Accordingly, the optical behaviour of the doped systems get tuned making them optically active for a wide spectral range in electromagnetic spectrum starting from infrared to UV region. Therefore, such site selective modulation of electronic and optical properties achieved through substitutional doping in MgO monolayers may be effective for desirable moulding of these materials for spintronic and optoelectronic applications.

HIV-1 Gag specificity for PIP2 is regulated by macromolecular electric properties of both protein and membrane local environments

HIV-1 assembly occurs at the plasma membrane, with the Gag polyprotein playing a crucial role. Gag association with the membrane is directed by the matrix domain (MA), which is myristoylated and has a highly basic region that interacts with anionic lipids. Several pieces of evidence suggest that the presence of phosphatidylinositol-(4,5)-bisphosphate (PIP2) highly influences this binding. Furthermore, MA also interacts with nucleic acids, which is proposed to be important for the specificity of GAG for PIP2-containing membranes. It is hypothesized that RNA has a chaperone function by interacting with the MA domain, preventing Gag from associating with unspecific lipid interfaces. Here, we study the interaction of MA with monolayer and bilayer membrane systems, focusing on the specificity for PIP2 and on the possible effects of a Gag N-terminal peptide on impairing the binding for either RNA or membrane. We found that RNA decreases the kinetics of the protein association with lipid monolayers but has no effect on the selectivity for PIP2. Interestingly, for bilayer systems, this selectivity increases in presence of both the peptide and RNA, even for highly negatively charged compositions, where MA alone does not discriminate between membranes with or without PIP2. Therefore, we propose that the specificity of MA for PIP2-containing membranes might be related to the electrostatic properties of both membrane and protein local environments, rather than a simple difference in molecular affinities. This scenario provides a new understanding of the regulation mechanism, with a macromolecular view, rather than considering molecular interactions within a ligand-receptor model.

Topological charge measurement in a four-level single layer graphene system

In this letter we have proposed a four-level graphene monolayer system for identifying the topological charge of Laguerre–Gaussian light. Here, we have shown that due to the four-wave mixing mechanism in the monolayer graphene system, a weak signal beam can be generated due to quantum coherence and interference effect. We have discussed the spatially dependent linear absorption spectrums of the weak probe and new generated signal beams via quantum mechanical density matrix formalism. We have found that by numbering the spot areas of the probe and signal beams, one can realize the topological charge of the Laguerre–Gaussian beam interacts by monolayer graphene system. Moreover, we have realized that for some topological charge the new generated signal beam can be amplified in the graphene system.

Linear response based theories for Dzyaloshinskii-Moriya interactions

We investigate abilities of various linear response based techniques for extracting parameters of antisymmetric Dzyaloshinskii-Moriya (DM) interactions from the first-principles electronic structure calculations. For these purposes, we further elaborate the idea of Sandratskii [Phys. Rev. B 96, 024450 (2017)], which states that $z$ component of the DM vector can be computed by retaining only spin-diagonal part of the spin-orbit (SO) coupling. We start our analysis with the magnetic force theorem (MFT), which relies on additional approximations resulting in the linear dependence of the exchange interactions on the response tensor, and compare it with the exact approach formulated in terms of the inverse response. We propose the downfolding procedure transferring the effect of these ligand spins into parameters of effective interactions between the localized spins. These techniques are applied for the series of CrCl$_3$ and CrI$_3$ based materials, including bulk, monolayer, bilayer, and three-layer systems. Particularly, we discuss how the DM interactions are induced by the inversion symmetry breaking at the surface or by the electric field. As long as the SO interaction of the heavy ligand atoms is taken into account in the calculations of the response tensor between the Cr $3d$ states, the MFT appears to be a good approximation for the DM interactions, being in contrast with the isotropic exchange, for which MFT and the exact method provide quite a different description. Finally, we discuss the relevance of our approach to other techniques ever proposed for calculations of the DM interactions. Particularly, we argue that the spin-current model for the DM interactions can be derived from the MFT based expression and is the relativistic counterpart of the double exchange, occurring in metallic systems in the limit of infinite exchange splitting.

Competing chiral d -wave superconductivity and magnetic phases in the strong-coupling Hubbard model on the honeycomb lattice

We address the competing superconducting and magnetic phases on the honeycomb lattice, in a field-theoretic approach suitable to yield a low-energy perturbative theory for the strong-coupling limit of the Hubbard model, both at half filling and in the low and high hole-doped regimes. The effective low-lying Hamiltonian is presented in terms of charge (Grassmann fields) and spin [SU(2) gauge fields] degrees of freedom. We analyze the competing phases by calculating the ground-state energy, electronic spectrum, and other observables associated with the $s$- and ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}+i{d}_{xy}$-wave superconducting phases, doped antiferromagnetic, and doped ferromagnetic states. We find that, while the antiferromagnetic order has the lowest ground-state energy for low hole doping near half filling, a dominant superconducting state with chiral ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}+i{d}_{xy}$-wave symmetry emerges in the vicinity of the Van Hove singularity in the high hole-doped regime, with the presence of a quantum first-order transition accompanied by spatial phase separation. We highlight that advances in the understanding of chiral superconducting states on the honeycomb lattice are relevant to a number of doped compounds including the graphene monolayer system.

Modeling Heart Diseases on a Chip: Advantages and Future Opportunities.

Heart disease is a significant burden on global health care systems and is a leading cause of death each year. To improve our understanding of heart disease, high quality disease models are needed. These will facilitate the discovery and development of new treatments for heart disease. Traditionally, researchers have relied on 2D monolayer systems or animal models of heart disease to elucidate pathophysiology and drug responses. Heart-on-a-chip (HOC) technology is an emerging field where cardiomyocytes among other cell types in the heart can be used to generate functional, beating cardiac microtissues that recapitulate many features of the human heart. HOC models are showing great promise as disease modeling platforms and are poised to serve as important tools in the drug development pipeline. By leveraging advances in human pluripotent stem cell-derived cardiomyocyte biology and microfabrication technology, diseased HOCs are highly tuneable and can be generated via different approaches such as: using cells with defined genetic backgrounds (patient-derived cells), adding small molecules, modifying the cells' environment, altering cell ratio/composition of microtissues, among others. HOCs have been used to faithfully model aspects of arrhythmia, fibrosis, infection, cardiomyopathies, and ischemia, to name a few. In this review, we highlight recent advances in disease modeling using HOC systems, describing instances where these models outperformed other models in terms of reproducing disease phenotypes and/or led to drug development.