Spatial Confinement Research Articles

Mitochondrial mechanotransduction through MIEF1 coordinates the nuclear response to forces.

Tissue-scale architecture and mechanical properties instruct cell behaviour under physiological and diseased conditions, but our understanding of the underlying mechanisms remains fragmentary. Here we show that extracellular matrix stiffness, spatial confinements and applied forces, including stretching of mouse skin, regulate mitochondrial dynamics. Actomyosin tension promotes the phosphorylation of mitochondrial elongation factor 1 (MIEF1), limiting the recruitment of dynamin-related protein 1 (DRP1) at mitochondria, as well as peri-mitochondrial F-actin formation and mitochondrial fission. Strikingly, mitochondrial fission is also a general mechanotransduction mechanism. Indeed, we found that DRP1- and MIEF1/2-dependent fission is required and sufficient to regulate three transcription factors of broad relevance-YAP/TAZ, SREBP1/2 and NRF2-to control cell proliferation, lipogenesis, antioxidant metabolism, chemotherapy resistance and adipocyte differentiation in response to mechanical cues. This extends to the mouse liver, where DRP1 regulates hepatocyte proliferation and identity-hallmark YAP-dependent phenotypes. We propose that mitochondria fulfil a unifying signalling function by which the mechanical tissue microenvironment coordinates complementary cell functions.

Investigation of the Electronic Structure in GaAs/AlxGa1‐xAs Quantum Dots with Four Electrons

AbstractIn this paper, a detailed analysis of the electronic structure of four‐electron quantum dots is performed with finite confinement potential by a modified variational optimization approach based mainly on the quantum genetic algorithm and the Hartree‐Fock‐Roothaan method. For the ground and higher excited configurations, our analysis covers a range of parameters like the average energies of ground and excited states, singlet and triplet state energies, orbital energies, and two‐electron Coulomb and exchange interaction energies. One‐electron kinetic energy, the Coulomb potential energy between electrons and impurity, the confinement potential energy for the electrons, and the probability of finding an electron inside or outside the quantum well are also studied. The results demonstrate that both spatial confinement and the height of the potential barrier have a pronounced effect on all energies in the strong and intermediate confinement regions, but this influence weakens significantly in large dot radii. The most substantial difference between singlet and triplet energies occurs in the 1s22s2p configurations, with this difference decreasing in higher configurations. Significant increases in the 1s and 2s orbital energies are observed at the dot radii where the 2p, 3d, and 4f electrons from the outermost orbit begin to penetrate the well.

Mechanically Stable PMMA‐Based Large‐Area Nano‐Channels with Sub‐10 nm Depth

AbstractArtificial sub‐microfluidic and nanofluidic devices allow for studying mass or ion transport effects under spatial confinement. It remains challenging to fabricate large‐scale, nanofluidic channels of well‐defined thickness for fundamental studies and practical applications, especially for extreme confinement conditions (e.g., with sub‐10 nm channel height). Here, a strategy is reported to fabricate large‐scale nano‐channels with the channel height down to 5.0 nm. The fabrication is enabled by developing ultra‐flat and ultra‐thin polymethylmethaacrylate (PMMA) layers as the spacer. The ease of scaling up the channel length to a millimeter in the lateral dimensions with high mechanical stability is demonstrated. Furthermore, experimental evidence is provided of the role of the mechanical coupling between the spacer and capping materials in determining the device's mechanical properties, and how controlling the channel width and the top graphite thickness can be employed to tailor the device's mechanical properties. Finally, employing near‐field IR experiments, the decay constant is established for the near‐field absorption intensity of PMMA molecules inside the channel by increasing the top layer thickness. This work develops a novel method for fabricating large‐area, mechanically stable nano‐channels for nanofluidic devices and lays the foundation for further in situ spectroscopic studies of electrochemistry within sub‐10 nm confinement.

Controlled Assembly of Lipid Molecules via Regulating Transient Spatial Confinement

The constructs of lipid molecules follow self-assembly, driven by intermolecular interactions, forming stacking of lipid bilayer films. Achieving designed geometry at nano- to micro-levels with packing deviating from the near-equilibrium structure is difficult to achieve due to the strong tendency of lipid molecules to self-assemble. Using ultrasmall (<fL) droplets containing designed molecules, our prior work has demonstrated that molecular assembly, in principle, is governed mainly by transient inter-molecular interactions under their dynamic spatial confinement, i.e., tri-phase boundaries during drying. As a result, the assemblies can deviate, sometimes significantly, from the near-equilibrium structures of self-assembly. The present work applies the approach and concept to lipid molecules using 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). Taking advantage of the high spatial precision and the minute size of the delivery probe in our combined atomic force microscopy and microfluidic delivery, the transient shape of each liquid droplet is regulated. In doing so, the final geometry of the POPC assemblies has been regulated to the designed geometry with nanometer precision. The results extend the concept of controlled assembly of molecules to amphiphilic systems. The outcomes exhibit high potential in lipid-based biomaterial science and biodevice engineering.

Two‐Photon Pumped Wavelength‐Tunable Single‐Mode Plasmonic Nanolaser with Ultralow Threshold

AbstractNonlinear optics play an important role in laser technology, optical communication, integrated optics, and other fields. However, conventional two‐photon lasing faces challenges such as high thresholds and large size, which hinder the miniaturization of lasers. In this study, the structure of single‐crystal Au/Al2O3/CsPbBr3 (ScAu/Al2O3/CPB) is constructed to achieve two‐photon pumped frequency upconversion single‐mode plasmonic lasing. The strong spatial confinement and near‐field enhancement of surface plasmons in metals enable the plasmonic lasing mode output in a hybrid nanocavity, significantly reducing the lasing threshold. Additionally, by applying external mechanical strain, the resonant wavelength of the lasing mode is dynamically regulated, further reducing the threshold to 0.48 mJ cm−2 based on piezo‐electronic effect. These results provide an effective strategy for all‐optical integration and the development of smaller, faster, and more efficient nanophotonics devices.

Construction of Heterointerfaced Nanoreactor Electrocatalyst via In Situ Evolution Toward Practical Room‐Temperature Sodium–Sulfur Batteries

AbstractSodium‐sulfur (Na─S) batteries have drawn considerable research interest owing to their high theoretical energy density and nature abundance. However, the intrinsic sluggish kinetics that has so far been scarcely explored in the conversion reaction of sodium polysulfides (NaPS) hinders its practical application. Herein, the design strategy of heterointerfaced nanoreactor is presented as sulfur reduction reaction (SRR) electrocatalyst for room temperature Na─S batteries. The synergistic incorporation of heterointerface and confined structure design can modulate the electronic structure of transitional metal active site and upshift its d‐band center, leading to enhanced NaPS adsorption and catalytic conversion toward streamlined SRR. Moreover, the spatial confinement of nanoreactor can not only stockpile nanoparticles to avoid their agglomeration and detachment, but also effectively immobilize sulfur species to inhibit shuttle effect and accommodate volume expansion over sodiation. The as‐developed electrocatalyst can achieve high discharge capacity of 1310 mAh g−1, remarkable cycling stability over 2500 cycles, and excellent performance under high sulfur loading and lean electrolyte/sulfur ratio. Ah level pouch cell can also exhibit promising performance for practical application. This strategy affords a synergistic combination of nanoreactor and heterointerface structure engineering toward fast and reliable electrochemistry, paving ways for the practical application of room temperature Na─S batteries.

Ultrathin Self-Healing Nanofibrous Membrane with a Hierarchical Confined Structure for Biomimetic Epidermal Electrodes.

Integrating self-healing capabilities into epidermal electrodes is crucial to improving their reliability and longevity. Self-healing nanofibrous materials are considered an ideal candidate for constructing ultrathin, long-lasting wearable epidermal electrodes due to their lightweight and high breathability. However, due to the strong interaction between fibers, self-healing nanofiber membranes cannot exist stably. Therefore, the development of self-healing and breathable nanofibrous epidermal electrodes still remains a major challenge. Here, a hierarchical confinement strategy that combines molecular and spatial confinement to overcome supramolecular hydrogen bonding between self-healing nanofibers is reported, and an ultrathin self-healing nanofibrous epidermal electrode with a neural net-like structure is developed. It can achieve real-time monitoring of electrophysiological signals through long-term conformal attachment to skin or plants and has no adverse effects on skin health or plant growth. Given the almost imperceptible nature of epidermal electrodes to users and plants, it lays the foundation for the development of biocompatible, self-healing, wearable, flexible electronics.

Cu2-xSe@MXene (Ti3C2Tx) 2D layered heterostructure as an anode for high-performance sodium-ion batteries

With a notable focus on developing efficient sodium storage electrode materials, sodium-ion batteries (SIBs) have been identified as a promising contender in the pursuit of high-performing substitutes for lithium-ion batteries. Among varying sodium storage anode materials for SIBs, nonstoichiometric Cu2-xSe exhibits significant promise. This material stands out due to its ultrahigh electrical conductivity and theoretical sodium storage capacity. However, the practical implementation of Cu2-xSe-based anodes in SIBs is significantly impeded by their sluggish electrochemical reaction kinetics and severe pulverization during the repeated charge–discharge cycles. In the current research, we introduce a novel and straightforward methodology for the synthesis of a heterostructured SIBs anode material (Cu2-xSe@Ti3C2Tx), by coupling Cu2-xSe nanoparticles with two-dimensional (2D) layered MXene (Ti3C2Tx). The 2D layered Ti3C2Tx can provide abundant fast Na+ transport pathways, which effectively promote the ion transport kinetics in the composite anode. Moreover, the pulverization of Cu2-xSe can be effectively mitigated due to the interlamellar spatial confinement of the 2D layered MXene matrix. Consequently, the electrochemical performances of the Cu2-xSe-based anode are significantly improved. Concretely, the Cu2-xSe@Ti3C2Tx anodes demonstrate remarkable rate performance (248mAh g−1 at 10.0 A/g), along with commendable cycling stability, exhibiting a capacity retention of 92 % at 5.0 A/g after 750 cycles. A comprehensive assessment of the Cu2-xSe@Ti3C2Tx anode has been conducted by assembling a full SIB alongside a Na3V2(PO4)3 cathode. This comprehensive study underscores the significant potential of Cu2-xSe-based composite materials, positioning it as a promising candidate for future advancements in SIB technology.

An Oriented Diffusion Strategy to Configure All-Region Ultrahigh-Density Metal Single Atoms for High-Capacity Sodium Storage.

Single-atom metals (SAMs), despite being promising for high-utilization catalysis, biomedicine, and energy storage, usually suffer from limited catalytic performance caused by low metal loading. Herein, via an oriented diffusion strategy, all-region ultrahigh-loading (18.9wt.%) Sn-SAMs over carbon nanorings matrix (Sn-SAMs@CNR) are initially achieved based on the transformation of a g-C3N4@SnO2@polydopamine ring-like nested structure. The formation process of Sn-SAMs involves a critical conversion from oxygen-coordination (SnO2) to nitrogen-coordination (Sn-N4) and simultaneous anti-Osterwalder ripening promoted under spatial confinement. Notably, the g-C3N4-derived N-containing gaseous intermediates dynamically drive the oriented diffusion (inside-out diffusion) of Sn-SAMs across the carbon nanorings, realizing an all-region ultrahigh loading of SAMs throughout the carbon matrix. This strategy is also applied to other metal materials (Fe, Co, Ni, Cu, and Sb), and features excellent universality. When applied as the anode for sodium-ion batteries, experimental analyses and theoretical calculations demonstrate that high-loading Sn-N4 active sites significantly optimize electron density distribution and improve reaction kinetics. Consequently, Sn-SAMs@CNR exhibits outstanding durability of 364mAhg-1 even after 5000 cycles with an impressively low (0.00068%) capacity decay per cycle. This work opens up a universally new avenue for all-region ultrahigh loading of SAMs to carbon matrix for high-performance energy storage.

Regulating Atomically-Precise Pt Sites for Boosting Light-Driven Dry Reforming of Methane.

Light-driven dry reforming of methane is a promising and mild route to convert two greenhouse gas into valuable syngas. However, developing facile strategy to atomically-precise regulate the active sites and realize balanced and stable syngas production is still challenging. Herein, we developed a spatial confinement approach to precisely control over platinum species on TiO2 surfaces, from single atoms to nanoclusters. The configuration comprising single atoms and sub-nanoclusters engenders pronounced electronic metal-support interactions, with resultant interfacial states prompting surface charge rearrangement. The unique geometric and electronic properties of these atom-cluster assemblies facilitate effective activation of CH4 and CO2, accelerating intermediate coupling and minimizing side reactions. Our catalyst exhibits an outstanding syngas generation rate of 34.41 mol gPt -1 h-1 with superior durability, displaying high apparent quantum yield of 9.1 % at 365 nm and turnover frequency of 1289 h-1. This work provides insightful understanding for exploring more multi-molecule systems at an atomic scale.

Regulating Atomically‐Precise Pt Sites for Boosting Light‐Driven Dry Reforming of Methane

AbstractLight‐driven dry reforming of methane is a promising and mild route to convert two greenhouse gas into valuable syngas. However, developing facile strategy to atomically‐precise regulate the active sites and realize balanced and stable syngas production is still challenging. Herein, we developed a spatial confinement approach to precisely control over platinum species on TiO2 surfaces, from single atoms to nanoclusters. The configuration comprising single atoms and sub‐nanoclusters engenders pronounced electronic metal‐support interactions, with resultant interfacial states prompting surface charge rearrangement. The unique geometric and electronic properties of these atom‐cluster assemblies facilitate effective activation of CH4 and CO2, accelerating intermediate coupling and minimizing side reactions. Our catalyst exhibits an outstanding syngas generation rate of 34.41 mol gPt−1 h−1 with superior durability, displaying high apparent quantum yield of 9.1 % at 365 nm and turnover frequency of 1289 h−1. This work provides insightful understanding for exploring more multi‐molecule systems at an atomic scale.

Co nanoparticles confined in N-doped hollow carbon nanospheres as multifunctional oxidase mimic for colorimetric detection of L-Cysteine and Hg2+

In contrast to peroxidase-mimicking nanozymes, oxidase mimics directly employ molecular oxygen (O2) as oxidant to generate reactive oxygen species (ROS). Generally, transition metal-based nanozymes exhibit poor oxidase-like activity. We herein constructed a colorimetric sensor based on Co-based oxidase mimic, where the Co nanoparticles were encapsulated in hollow N-doped carbon nanospheres (Co-N/C). Co nanoparticles confined catalyst effectively anchored the active part, which greatly influenced the catalytic activity of the oxidase-mimic nanozymes. Due to the antioxidative property of L-Cysteine (L-Cys) and the specific complexation between L-Cys and Hg2+, the rationally designed Co-N/C could be utilized to detect L-Cys and Hg2+. The proposed sensing platform exhibited wide linear ranges of 1–30 μM for L-Cys and 0.6–30 μM for Hg2+, respectively. The excellent selectivity of the constructed sensor showed the reliability and practicality for the assay of L-Cys and Hg2+ in fetal bovine serum. The spatial confinement can prevent the aggregation of Co nanoparticles, boosting the stability and catalytic performance in colorimetric sensing.

Polymer Mechanochemistry in Confined Spaces.

With the development of mechanophores, polymer mechanochemistry has emerged as a powerful tool for creating force-responsive materials with a variety of desired functions, ranging from color change to molecular release. However, it remains challenging to improve the efficiency of mechanochemical activation, especially for mechanophores embedded within polymer networks, which has profound implications for translating mechanochemical responses into materials-centered applications. The physical and chemical conditions under spatial confinement differ significantly from those in the surrounding bulk environment, offering opportunities to facilitate mechanochemical activation. In this Minireview, we discuss and summarize recent progress in polymer mechanochemistry within confined spaces including surfaces/interfaces, polymer assemblies, and other nanostructures, specifically focusing on the effects of spatial confinement on the enhancement of mechanophore activation. We envision that combining confinement effects with advances in molecular and materials engineering will further improve the activation efficiency, capitalizing more fully on the potential of mechanophores toward practical applications.

Memory effects of transcription regulator−DNA interactions in bacteria

Memory effect refers to the phenomenon where past events influence a system's current and future states or behaviors. In biology, memory effects often arise from intra- or intermolecular interactions, leading to temporally correlated behaviors. Single-molecule studies have shown that enzymes and DNA-binding proteins can exhibit time-correlated behaviors of their activity. While memory effects are well documented and studied in vitro, no such examples exist in cells to our knowledge. Combining single-molecule tracking (SMT) and single-cell protein quantitation, we find in living Escherichia coli cells distinct temporal correlations in the binding/unbinding events on DNA by MerR- and Fur-family metalloregulators, manifesting as memory effects with timescales of ~1 s. These memory effects persist irrespective of the type of the metalloregulators or their metallation states. Moreover, these temporal correlations of metalloregulator-DNA interactions are associated with spatial confinements of the metalloregulators near their DNA binding sites, suggesting microdomains of ~100 nm in size that possibly result from the spatial organizations of the bacterial chromosome without the involvement of membranes. These microdomains likely facilitate repeated binding events, enhancing regulator-DNA contact frequency and potentially gene regulation efficiency. These findings provide unique insights into the spatiotemporal dynamics of protein-DNA interactions in bacterial cells, introducing the concept of microdomains as a crucial player in memory effect-driven gene regulation.

A theoretical exploration of the electronic structure and single photoionization of the many-electron system confined in Gaussian potential

This manuscript investigates the electronic structures, spectral properties, and photoionization processes of the confined atomic system. For this purpose, a relativistic methodology employing the Dirac–Coulomb Hamiltonian within the context of relativistic configuration interaction is suggested, utilizing independent particle basis wavefunctions. The key idea of this approach is to place the atom inside a Gaussian potential, which gives a realistic description of the spatial confinement in quantum dots due to a smooth change at the quantum dot boundaries and has a finite range and depth for the spatial confinement. As a result, the local central potential is modified, which is determined by a self-consistent process. The solutions to the Dirac equation, incorporating the aforementioned central potential, yield both the continuous and bound state wave functions. The photoionization process is determined through the application of the distorted wave approach within the context of relativistic Dirac theory. As an application, the electronic structures of the confined Li atom, including energies, ionization potentials, transition rates, and photoionization dynamical properties such as wave functions, cross sections, and photoelectron angular distributions, are systematically investigated within the dipole approximation for a wide range of potential depths and confining radii. A systematic comparison of the present outcomes is made with other available results. The present study is not only meaningful for fundamental research in atomic and molecular physics, but also has implications for a range of disciplines, such as nanochemistry, materials science, and other related fields.

Cleft Palate Induced by Augmented Fibroblast Growth Factor-9 Signaling in Cranial Neural Crest Cells in Mice.

Although enhanced fibroblast growth factor (FGF) signaling has been demonstrated to be crucial in many cases of syndromic cleft palate caused by tongue malposition in humans, animal models that recapitulate this phenotype are limited, and the precise mechanisms remain elusive. Mutations in FGF9 with the effect of either loss- or gain-of-function effects have been identified to be associated with cleft palate in humans. Here, we generated a mouse model with a transgenic Fgf9 allele specifically activated in cranial neural crest cells, aiming to elucidate the gain-of-function effects of Fgf9 in palatogenesis. We observed cleft palate with 100% penetrance in mutant mice. Further analysis demonstrated that no inherent defects in the morphogenic competence of palatal shelves could be found, but a passively lifted tongue prevented the elevation of palatal shelves, leading to the cleft palate. This tongue malposition was induced by posterior spatial confinement that was exerted by temporomandibular joint (TMJ) dysplasia characterized by a reduction in Sox9+ progenitors within the condyle and a structural decrease in the posterior dimension of the lower jaw. Our findings highlight the critical role of excessive FGF signaling in disrupting spatial coordination during palate development and suggest a potential association between palatal shelf elevation and early TMJ development.

Smartphone-based dual-mode aptasensor with bifunctional metal-organic frameworks as signal probes for ochratoxin A detection

Ochratoxin A (OTA) poses significant risks to human health, being potentially nephrotoxic, carcinogenic, genotoxic, and immuno-toxic. In this work, we developed a dual-mode aptasensor for OTA analysis, integrating colorimetric, electrochemical, and smartphone-based detection. The bifunctional Fe-MIL-88 metal-organic framework, acting as both a nanozyme capable of catalyzing the 3,3′,5,5′-tetramethylbenzidine substrate and an electrochemical signal amplifier, enabled OTA quantification through current response or changes in color and absorbance intensity. Besides, the spatial confinement effect enhances the local concentration of Fe-MIL-88 signal probes through rolling circle amplification reaction, thereby contributing to a substantial enhancement in sensitivity. The proposed technique is simple, disposable, highly sensitive and selective, enabling OTA detection in the range of 1 fg/mL to 250 ng/mL, with a limit of detection of 0.22 fg/mL (3σ rule). Furthermore, we successfully detected OTA in corn, wheat, and red wine samples, with results good concordance with those obtained using commercial enzyme-linked immunoassay kits.

Spatiotemporal spreading characteristics of dust aerosols by coal mining machine cutting and "partition/multi-level composite field" atomization dust purification technology

To locally atomize the spatial confinement of primary dust generated by the shearer cut-off, the CFD-DPM mathematical model was used to simulate and analyze the wind-borne dust transport law, which resulted in the heavily polluted area of primary dust. A multi-level and multi-dimensional coal machine spray system was developed for the polluted area, its atomization effect was verified by using the TAB breakup model. The results show that the heavily polluted area of primary dust is mainly concentrated in the position of fully mechanized mining face Z=24–39 m area of shearer, and the average concentration is 738.2 mg/m³. The average concentration of droplets generated by the multi-level and multi-dimensional shearer spray system at the shearer drum is 0.66 kg/m³, with a percentage of droplets with particle size between 40 and 160 μm exceeding 85 %. The coverage rate of the shearer drum is 95 %. The relationship between droplet concentration and time is consistent with the Boltzmann function fitting model. Following the implementation of the multi-level and multi-dimensional coal machine spray system in the field, it was observed that the average reduction in dust levels was 90.9 % for total dust and 85.7 % for exhaled dust in the synthesized mining face.

Spatial confinement strategy modulated by kinetic diameters of gaseous molecules for sodium storage

Constructing closed pore structures is essential for improving the plateau capacity of high-capacity hard carbon (HC) anodes for sodium-ion batteries. However, the absence of a straightforward and efficient strategy for constructing closed pores has hindered the advancement of high-capacity HC anodes. Here, we have developed a spatial confinement strategy for constructing closed pore structures using pyrolytic carbon (PC) as substrate and pyrolysis gas as the carbon source for chemical vapor deposition. The deposition of pyrolysis gas effectively tightens the pore entrance, thereby preventing electrolyte infiltration and transforming the open pores in the PC into highly efficient sites for sodium storage. The obtained optimal anodes demonstrate a remarkable specific capacity of 324.6 mAh g-1. More importantly, we calculate the kinetic diameters of the carbon source molecules from their iso-electron density surfaces and correlate them with the mechanism of closed pore formation, which will effectively guide the fabrication of closed pores for sodium storage.

An explore method for quick screening biomarkers based on effective enrichment capacity and data mining

Protein glycosylation acts as a crucial role in regulating protein function and maintaining cellular homeostasis. Efficient peptide enrichment can be utilized to effectively solve the inherent challenges of protein glycosylation analysis to search unknown cancer biomarkers. In this research, a low dimensional porous hydrophilic nanosheets with a multi-level porous structure (Co-MOF-SiO2@HA) was synthetized via an easy one-pot method for the efficient enrichment of the N-glycopeptides in the digests of complex biosamples. The synthetized nanosheets Co-MOF-SiO2@HA demonstrated excellent enriching performances including a high enrichment capacity (300 mg g-1 calculated), a spectacular selectivity (IgG digests and BSA digests at the molar ratio of 1/1200), and an excellent spatial confinement ability (IgG digests, IgG and BSA at the molar ratio of 1/1000/1000). As an explore result, after the enrichment of human colorectal cancer tissue and human healthy tissue by the nanosheets, several proteins related to cancers and one protein directly related to well-known human colorectal cancer were identified by detecting the corresponding glycopeptides. It presented the potential value of the feasibility of this analysis mode by nanosheets Co-MOF-SiO2@HA in proteomic analysis.