Concentration-Driven Evolution of Adaptive Artificial Ion Channels or Nanopores with Specific Anticancer Activities

In nature, ceramides are a class of sphingolipids possessing a unique ability to self-assemble into protein-permeable channels with intriguing concentration-dependent adaptive channel cavities. However, within the realm of artificial ion channels, this interesting phenomenon is scarcely represented. Herein, we report on a novel class of adaptive artificial channels, Pn-TPPs, based on PEGylated cholic acids bearing triphenylphosphonium (TPP) groups as anion binding motifs. Interestingly, the molecules self-assemble into chloride ion channels at low concentrations while transforming into small molecule-permeable nanopores at high concentrations. Moreover, the TPP groups endow the molecules with mitochondria-targeting properties, enabling them to selectively drill holes on the mitochondrial membrane of cancer cells and subsequently trigger the caspase 9 apoptotic pathway. The anticancer efficacies of Pn-TPPs correlate with their abilities to form nanopores. Significantly, the most active ensembles formed by P5-TPP exhibits impressive anticancer activity against human liver cancer cells, with an IC50 value of 3.8 μM. While demonstrating similar anticancer performance to doxorubicin, P5-TPP exhibits a selectivity index surpassing that of doxorubicin by a factor of 16.8.

The effect of the initial temperature, pressure, and shape of carbon nanopores on the separation process of SiO2 molecules from water vapor by molecular dynamics simulation

Today, with the advancement of science in nanotechnology, it is possible to remove dust nanostructures from the air breathed by humans or other fluids. In the present study, the separation of SiO2 molecules from H2O vapor is studied using molecular dynamics (MD) simulation. This research studied the effect of initial temperature, nanopore geometry, and initial pressure on the separation of SiO2 molecules. The obtained results show that by increasing the temperature to 500 K, the maximum velocity (Max-Vel) of the samples reached 2.47 Å/fs. Regarding the increasing velocity of particles, more particles pass via the nanopores. Moreover, the shape of the nanopore could affect the number of passing particles. The results show that in the samples with a cylindrical nanopore, 20 and 40% of SiO2 molecules, and with the sphere cavity, about 32 and 38% of SiO2 particles passed in the simulated structure. So, it can be concluded that the performance of carbon nanosheets with a cylindrical pore and 450 K was more optimal. Also, the results show that an increase in initial pressure leads to a decrease in the passage of SiO2 particles. The results reveal that about 14 and 54% of Silica particles passed via the carbon membrane with increasing pressure. Therefore, for use in industry, in terms of separating dust particles, in addition to applying an EF, temperature, nanopore geometry, and initial pressure should be controlled.

Nanopore-related cellular death through cytoskeleton depolymerization by drug-induced ROS

Prostate cancer (PCa) is a malignant tumor with a very high incidence which ranks second after lung cancer. Although there are many drugs available for the treatment of PCa, their effectiveness and anti-cancer mechanisms still need to be explored. Atomic force microscopy (AFM) could characterize minor morphological changes on cell surfaces, which provides an effective method to explore the interaction between drugs and cells at the nanometer level and further investigate the mechanisms for treating PCa. In our research, AFM visualized pore-like structures in the PC3M cell membrane after treatment with the eminent anticancer agent paclitaxel (PTX). The diameter, depth and number of these pores were in a concentration and time-dependent manner. Reactive oxygen species (ROS) was shown to depolymerize the actin cytoskeleton and make the membrane more sensitive to oxidative damage, thus inducing pore information. After pretreatment with a ROS scavenger, pore formation was prevented. AFM imaging technology provides a new evaluation method for drug-targeted therapy for cancer.

E. coli outer membrane protein T (OmpT) nanopore for peptide sensing

Peptide detection methods with facility and high sensitivity are essential for diagnosing disease associated with peptide biomarkers. Nanopore sensing technology had emerged as a low cost, high-throughput, and scalable tool for peptide detection. The omptins family proteins which can form β-barrel pores have great potentials to be developed as nanopore biosensor. However, there are no study about the channel properties of E. coli OmpT and the development of OmpT as a nanopore biosensor. In this study, the OmpT biological nanopore channel was constructed with a conductance of 1.49 nS in 500 mM NaCl buffer and a three-step gating phenomenon under negative voltage higher than 100 mV and then was developed as a peptide biosensor which can detect peptide without the interfere of ssDNA and dNTPs. The OmpT constructed in this study has potential application in peptide detection, and also provides a new idea for the detection of peptides using the specific binding ability of protease.

A Membrane Tension-Responsive Mechanosensitive DNA Nanomachine

Membrane curvature reflects physical forces operating on the lipid membrane, which plays important roles in cellular processes. Here, we design a mechanosensitive DNA (MSD) nanomachine that mimics natural mechanosensitive PIEZO channels to convert the membrane tension changes of lipid vesicles with different sizes into fluorescence signals in real time. The MSD nanomachine consists of an archetypical six-helix-bundle DNA nanopore, cholesterol-based membrane anchors, and a solvatochromic fluorophore, spiropyran (SP). We find that the DNA nanopore effectively amplifies subtle variations of the membrane tension, which effectively induces the isomerization of weakly emissive SP into highly emissive merocyanine isomers for visualizing membrane tension changes. By measuring the membrane tension via the fluorescence of MSD nanomachine, we establish the correlation between the membrane tension and the curvature that follows the Young-Laplace equation. This DNA nanotechnology-enabled strategy opens new routes to studying membrane mechanics in physiological and pathological settings.

Correction: Study on the controllability of the fabrication of single-crystal silicon nanopores/nanoslits with a fast-stop ionic current-monitored TSWE method

[This corrects the article DOI: 10.1038/s41378-023-00532-0.].

Electrochemical monitoring of enzymatic cleavage in nanochannels with nanoparticle-based enhancement: determination of MMP-9 biomarker

For the first time the use of nanoparticles as carriers of an enzymatic substrate immobilized inside nanoporous alumina membranes is proposed with the aim of amplifying the nanochannel blocking produced and, consequently, improving the efficiency of an enzyme determination through enzymatic cleavage. Streptavidin-modified polystyrene nanoparticles (PSNPs) are proposed as carrier agents, contributing to the steric and the electrostatic blockage due to the charge they present at different pH values. Electrostatic blockage is the predominant effect that governs the blockage in the interior of the nanochannel and is dependent not just in the charge inside the channel, but also in the polarity of the redox indicator used. Hence, the effect of using negatively charged ([Fe(CN)₆]^4-) and positively charged ([Ru(NH₃)₆]³⁺) redox indicator ions is studied for the first time. Under the optimum conditions, matrix-metalloproteinase 9 (MMP-9) is detected at clinically relevant levels (100-1200 ng/mL) showing a detection limit of 75 ng/mL and a quantification limit of 251 ng/mL with good reproducibility (RSD: 8%) and selectivity, also showing an excellent performance in real samples with acceptable recovery percentages (in the range around 80-110%). Overall, our approach represents a cheap and fast sensing methodology of great potential in point-of-care diagnostics.

Study on the controllability of the fabrication of single-crystal silicon nanopores/nanoslits with a fast-stop ionic current-monitored TSWE method

The application of single-crystal silicon (SCS) nanopore structures in single-molecule-based analytical devices is an emerging approach for the separation and analysis of nanoparticles. The key challenge is to fabricate individual SCS nanopores with precise sizes in a controllable and reproducible way. This paper introduces a fast-stop ionic current-monitored three-step wet etching (TSWE) method for the controllable fabrication of SCS nanopores. Since the nanopore size has a quantitative relationship with the corresponding ionic current, it can be regulated by controlling the ionic current. Thanks to the precise current-monitored and self-stop system, an array of nanoslits with a feature size of only 3 nm was obtained, which is the smallest size ever reported using the TSWE method. Furthermore, by selecting different current jump ratios, individual nanopores of specific sizes were controllably prepared, and the smallest deviation from the theoretical value was 1.4 nm. DNA translocation measurement results revealed that the prepared SCS nanopores possessed the excellent potential to be applied in DNA sequencing.

Mobile Molecules: Reactivity Profiling Guides Faster Movement on a Cysteine Track

We previously reported a molecular hopper, which makes sub-nanometer steps by thiol-disulfide interchange along a track with cysteine footholds within a protein nanopore. Here we optimize the hopping rate (ca. 0.1 s-1 in the previous work) with a view towards rapid enzymeless biopolymer characterization during translocation within nanopores. We first took a single-molecule approach to obtain the reactivity profiles of individual footholds. The pK a values of cysteine thiols within a pore ranged from 9.17 to 9.85, and the pH-independent rate constants of the thiolates with a small-molecule disulfide varied by up to 20-fold. Through site-specific mutagenesis and a pH increase from 8.5 to 9.5, the overall hopping rate of a DNA cargo along a five-cysteine track was accelerated 4-fold, and the rate-limiting step 21-fold.

Mobile Molecules: Reactivity Profiling Guides Faster Movement on a Cysteine Track

We previously reported a molecular hopper, which makes sub-nanometer steps by thiol-disulfide interchange along a track with cysteine footholds within a protein nanopore. Here we optimize the hopping rate (ca. 0.1 s-1 in the previous work) with a view towards rapid enzymeless biopolymer characterization during translocation within nanopores. We first took a single-molecule approach to obtain the reactivity profiles of individual footholds. The pKa values of cysteine thiols within a pore ranged from 9.17 to 9.85, and the pH-independent rate constants of the thiolates with a small-molecule disulfide varied by up to 20-fold. Through site-specific mutagenesis and a pH increase from 8.5 to 9.5, the overall hopping rate of a DNA cargo along a five-cysteine track was accelerated 4-fold, and the rate-limiting step 21-fold.

Direct Fabrication of Sub-10 nm Nanopores in WO3 Nanosheets Using Single Swift Heavy Ions

Extending the fabrication methodology of solid-state nanopores in a wide range of materials is significant in the fields of single molecule detection, nanofluidic devices, and nanofiltration membranes. Here, we demonstrate a new method to directly fabricate size- and density-controllable sub-10 nm nanopores in WO₃ nanosheets using single swift heavy ions (SHIs) without any chemical etching process. By selecting ions of different electronic energy losses (S_e), nanopores with sizes from 1.8 to 7.4 nm can be created in WO₃ nanosheets. The creation efficiency of nanopores achieves ∼100% for S_e > 20 keV/nm, and there exists a critical thickness below which nanopores can be created. Combined with molecular dynamics simulations, we propose that the viscosity and surface tension of the transient molten phase caused by SHIs are the key factors for the formation of nanopores. This method paves a way to fabricate solid-state nanopores in materials with a low viscosity and surface tension.

Third-Generation Sequencing of Epigenetic DNA

The discovery of epigenetic bases has revolutionised the understanding of disease and development. Among the most studied epigenetic marks are cytosines covalently modified at the 5 position. In order to gain insight into their biological significance, the ability to determine their spatiotemporal distribution within the genome is essential. Techniques for sequencing on "next-generation" platforms often involve harsh chemical treatments leading to sample degradation. Third-generation sequencing promises to further revolutionise the field by providing long reads, enabling coverage of highly repetitive regions of the genome or structural variants considered unmappable by next generation sequencing technology. While the ability of third-generation platforms to directly detect epigenetic modifications is continuously improving, at present chemical or enzymatic derivatisation presents the most convenient means of enhancing reliability. This Review presents techniques available for the detection of cytosine modifications on third-generation platforms.

High durability and stability of 2D nanofluidic devices for long-term single-molecule sensing

Nanopores in two-dimensional (2D) membranes hold immense potential in single-molecule sensing, osmotic power generation, and information storage. Recent advances in 2D nanopores, especially on single-layer MoS2, focus on the scalable growth and manufacturing of nanopore devices. However, there still remains a bottleneck in controlling the nanopore stability in atomically thin membranes. Here, we evaluate the major factors responsible for the instability of the monolayer MoS2 nanopores. We identify chemical oxidation and delamination of monolayers from their underlying substrates as the major reasons for the instability of MoS2 nanopores. Surface modification of the substrate and reducing the oxygen from the measurement solution improves nanopore stability and dramatically increases their shelf-life. Understanding nanopore growth and stability can provide insights into controlling the pore size, shape and can enable long-term measurements with a high signal-to-noise ratio and engineering durable nanopore devices.

Multifunctionalized carbon-fiber-reinforced polyetheretherketone implant for rapid osseointegration under infected environment

Carbon fiber reinforced polyetheretherketone (CFRPEEK) possesses a similar elastic modulus to that of human cortical bone and is considered as a promising candidate to replace metallic implants. However, the bioinertness and deficiency of antibacterial activities impede its application in orthopedic and dentistry. In this work, titanium plasma immersion ion implantation (Ti-PIII) is applied to modify CFRPEEK, achieving unique multi-hierarchical nanostructures and active sites on the surface. Then, hybrid polydopamine (PDA)@ZnO-EDN1 nanoparticles (NPs) are introduced to construct versatile surfaces with improved osteogenic and angiogenic properties and excellent antibacterial properties. Our study established that the modified CFRPEEK presented favorable stability and cytocompatibility. Compared with bare CFRPEEK, improved osteogenic differentiation of rat mesenchymal stem cells (BMSCs) and vascularization of human umbilical vein endothelial cells (HUVECs) are found on the functionalized surface due to the zinc ions and EDN1 releasing. In vitro bacteriostasis assay confirms that hybrid PDA@ZnO NPs on the functionalized surface provided an effective antibacterial effect. Moreover, the rat infected model corroborates the enhanced antibiosis and osteointegration of the functionalized CFRPEEK. Our findings indicate that the multilevel nanostructured PDA@ZnO-EDN1 coated CFRPEEK with enhanced antibacterial, angiogenic, and osteogenic capacity has great potential as an orthopedic/dental implant material for clinical application.

A Light-Triggered Synthetic Nanopore for Controlling Molecular Transport Across Biological Membranes

Controlling biological molecular processes with light is of interest in biological research and biomedicine, as light allows precise and selective activation in a non-invasive and non-toxic manner. A molecular process benefitting from light control is the transport of cargo across biological membranes, which is conventionally achieved by membrane-puncturing barrel-shaped nanopores. Yet, there is also considerable gain in constructing more complex gated pores. Here, we pioneer a synthetic light-gated nanostructure which regulates transport across membranes via a controllable lid. The light-triggered nanopore is self-assembled from six pore-forming DNA strands and a lid strand carrying light-switchable azobenzene molecules. Exposure to light opens the pore to allow small-molecule transport across membranes. Our light-triggered pore advances biomimetic chemistry and DNA nanotechnology and may be used in biotechnology, biosensing, targeted drug release, or synthetic cells.

Developing dual nano/macroporous starch bioaerogels via emulsion templating and supercritical carbon dioxide drying

In this study, emulsified oil droplets were employed as a temporary porogen to obtain dual nano/macroporous starch aerogels by supercritical carbon dioxide (SC-CO₂) drying. This method took advantage of the solubility of the oil droplet porogens in acetone, and the insolubility of corn starch in this solvent, so this process could be integrated into the typical aerogel processing method. The effect of porogen content and starch concentration on physical and mechanical properties and the internal morphology of the obtained aerogels were studied. While the neat starch aerogel showed a compact structure in macroscale size with interconnected nanopores, the sacrificing oil droplet porogens induced macropores in the emulsion-templated aerogels. Furthermore, the nanoporous structures of starch aerogels were also well-preserved in which the macropores were surrounded by fine and interconnected nanofibrous networks. It resulted in aerogels that exhibited internal morphology in two scales (macropores and nanopores) with a high surface area (156-190 m²/g).

A Nanopore-Based Saccharide Sensor

Saccharides play critical roles in many forms of cellular activities. Saccharide structures are however complicated and similar, setting a technical hurdle for direct identification. Nanopores, which are emerging single molecule tools sensitive to minor structural differences between analytes, can be engineered to identity saccharides. A hetero-octameric Mycobacterium smegmatis porin A nanopore containing a phenylboronic acid was prepared, and was able to clearly identify nine monosaccharide types, including D-fructose, D-galactose, D-mannose, D-glucose, L-sorbose, D-ribose, D-xylose, L-rhamnose and N-acetyl-D-galactosamine. Minor structural differences between saccharide epimers can also be distinguished. To assist automatic event classification, a machine learning algorithm was developed, with which a general accuracy score of 0.96 was achieved. This sensing strategy is generally suitable for other saccharide types and may bring new insights to nanopore saccharide sequencing.

Non-binary Encoded Nucleic Acid Barcodes Directly Readable by a Nanopore

A large collection of unique molecular barcodes is useful in the simultaneous sensing or screening of molecular analytes. Though the sequence of DNA has been widely applied to encode for molecular barcodes, decoding of these barcodes is normally assisted by sequencing. We here demonstrate a barcode system based solely on self-assembly of synthetic nucleic acids and direct nanopore decoding. Each molecular barcode is composed of "n" distinct information nodes in a non-binary manner and can be sequentially scanned and decoded by a Mycobacterium smegmatis porin A (MspA) nanopore. Nanopore events containing step-shaped features were consistently reported. 14 unique information nodes were developed which in principle could encode for 14ⁿ unique molecular barcodes in a barcode containing "n" information nodes. These barcode probes were adapted to detect different antibody proteins or cancer-related microRNAs, suggesting their immediate application in a wide variety of sensing applications.

Electrical monitoring of infection biomarkers in chronic wounds using nanochannels

Chronic wounds represent an important healthcare challenge in developed countries, being wound infection a serious complication with significant impact on patients' life conditions. However, there is a lack of methods allowing an early diagnosis of infection and a right decision making for a correct treatment. In this context, we propose a novel methodology for the electrical monitoring of infection biomarkers in chronic wound exudates, using nanoporous alumina membranes. Lysozyme, an enzyme produced by the human immune system indicating wound infection, is selected as a model compound to prove the concept. Peptidoglycan, a component of the bacterial layer and the native substrate of lysozyme, is immobilized on the inner walls of the nanochannels, blocking them both sterically and electrostatically. The steric blocking is dependent on the pore size (20-100 nm) and the peptidoglycan concentration, whereas the electrostatic blocking depends on the pH. The proposed analytical method is based on the electrical monitoring of the steric/electrostatic nanochannels unblocking upon the specific degradation of peptidoglycan by lysozyme, allowing to detect the infection biomarker at 280 ng/mL levels, which are below those expected in wounds. The low protein adsorption rate and thus outstanding filtering properties of the nanoporous alumina membranes allowed us to discriminate wound exudates from patients with both sterile and infected ulcers without any sample pre-treatment usually indispensable in most diagnostic devices for analysis of physiological fluids. Although size and charge effects in nanochannels have been previously approached for biosensing purposes, as far as we know, the use of nanoporous membranes for monitoring enzymatic cleavage processes, leading to analytical systems for the specific detection of the enzymes has not been deeply explored so far. Compared with previously reported methods, our methodology presents the advantages of no need of neither bioreceptors (antibodies or aptamers) nor competitive assays, low matrix effects and quantitative and rapid analysis at the point-of-care, being also of potential application for the determination of other protease biomarkers.

Expanding the Molecular Alphabet of DNA-Based Data Storage Systems with Neural Network Nanopore Readout Processing

DNA is a promising next-generation data storage medium, but challenges remain with synthesis costs and recording latency. Here, we describe a prototype of a DNA data storage system that uses an extended molecular alphabet combining natural and chemically modified nucleotides. Our results show that MspA nanopores can discriminate different combinations and ordered sequences of natural and chemically modified nucleotides in custom-designed oligomers. We further demonstrate single-molecule sequencing of the extended alphabet using a neural network architecture that classifies raw current signals generated by Oxford Nanopore sequencers with an average accuracy exceeding 60% (39× larger than random guessing). Molecular dynamics simulations show that the majority of modified nucleotides lead to only minor perturbations of the DNA double helix. Overall, the extended molecular alphabet may potentially offer a nearly 2-fold increase in storage density and potentially the same order of reduction in the recording latency, thereby enabling new implementations of molecular recorders.

Influence of sterilization on the performance of anodized nanoporous titanium implants

Towards clinical translation of bioactive nano-engineered titanium implants, achieving appropriate sterilization and understanding its influence on the modified implant characteristics is essential. With limited studies exploring the influence of sterilization techniques on electrochemically anodized titanium with TiO₂ nanostructures, we aimed to advance this domain by performing an in-depth evaluation of the influence of common sterilization techniques (ethanol immersion, various UV irradiation times, gamma irradiation, and dry/wet autoclaving) on TiO₂ nanopores fabricated on micro-rough Ti surfaces (dual micro-nano) via single step anodization. Various sterilized surfaces were systematically compared in terms of topographical, chemical, crystalline, wettability and mechanical characteristics. Next, we investigated the protein adhesion capacity and functions of primary gingival fibroblasts (proliferation, adhesion/alignment and spreading morphology) to compare the bioactivity of the sterilized nanopores. Ethanol immersion, gamma irradiation and UV irradiation conserved the topography of the fabricated nanopores, while autoclave sterilization (both dry and wet) compromised the nanoporous structures. Various duration of UV-sterilization resulted in no significant changes in the surface topography and chemistry of the fabricated TNPs. Our findings revealed that UV irradiation is the most appropriate technique to sterilize nano-engineered titanium implants for appropriate wettability, protein adhesion capacity and enhanced metabolism and proliferation of human gingival fibroblasts (hGFs). This study systematically investigated the influence of sterilization on anodized nano-engineered titanium implants towards achieving reproducible outcomes (in terms of topography, chemistry and bioactivity), and found that UV irradiation holds great promise for application across different nano-engineered metal surfaces.

Potential role of nanobubbles in dynamically modulating the structure and stability of anammox granular sludge within biological nitrogen removal process

The generation of visible macrobubbles considerably affects the structure and function of anammox granules in the anammox granular sludge (AnGS) system. However, the existence of nanobubbles (NBs) and their role in maintaining the AnGS structure and stability are unclear because of the complexity of the system and lack of effective analytical methods. In this study, methods for NB analysis and assessment of their effects were developed to investigate the formation and characteristics of NBs in an AnGS system and the effects of NBs on the properties and function of AnGS. The results indicated that dissolved gas supersaturation caused by AnGS generated NBs of 2.75 × 10⁸ bubbles/mL inside an AnGS reactor after running for 300 min at 30 °C. The increasing absolute value of the zeta potential of NBs with time indicated that the NBs in the AnGS system were gradually stable. The size of the stable NBs ranged from 150 nm to 400 nm. NB formation also increased the space and pressure between cells, leading to the breakage of the cell cluster and causing structural changes in granules. Changes in the local granular microstructure caused by NBs were favorable for the porous structure of granules to avoid granular disintegration and flotation caused by the excessive secretion of extracellular polymeric substances blocking gas channels. The formation and stability of NBs penetrating the cell clusters played a crucial role in the formation and stability of nanopores around or inside the cell clusters, further providing a basis for the formation of high-porosity structures and efficient mass transfer of AnGS.

Artificially intelligent nanopore for rapid SARS-CoV-2 testing

An article in Nature Communications reports a method for the rapid detection of SARS-CoV-2 in saliva samples using nanopores and a machine learning algorithm.

DNA translocation through pH-dependent soft nanopores

Controlling the translocation velocity of DNA is the main challenge in the process of sequencing by means of nanopores. One of the main methods to overcome this challenge is covering the inner walls of the nanopore with a layer of polyelectrolytes, i.e., using soft nanopores. In this paper the translocation of DNA through soft nanopores, whose inner polyelectrolyte layer (PEL) charge is pH-dependent, is theoretically studied. We considered the polyelectrolyte to be made up of either acidic or basic functional groups. It was observed that the electroosmotic flow (EOF) induced by the PEL charge is in the opposite/same direction of DNA electrophoresis (EPH) when the PEL is made up of acidic/basic groups. It was found that, not only the DNA charge and consequently the EPH, but also the EOF are influenced by the electrolyte acidity. The synergy between the changes in the retardation, EOF and EPH, determines how the intensity and direction of DNA translocation alter with pH. In fact, for both cases, at mild values of pH (as long as [Formula: see text] for the case that PEL is of acidic nature), the more the pH, the less the translocation velocity. However, for PELs of acidic nature, higher values of pH increase the intensity of the EOF so much that DNA may experience a change in the translocation direction. Ultimately, conducting the process at a particular range of pH values, and at higher pH values, in the cases of using PELs of acidic nature, and basic nature, respectively, was recommended.

High Osmotic Power Generation via Nanopore Arrays in Hybrid Hexagonal Boron Nitride/Silicon Nitride Membranes

Nanopores embedded in two-dimensional (2D) nanomaterials are a promising emerging technology for osmotic power generation. Here, coupling our new AFM-based pore fabrication approach, tip-controlled local breakdown (TCLB), with a hybrid membrane formed by coating silicon nitride (SiN) with hexagonal boron nitride (hBN), we show that high osmotic power density can be obtained in systems that do not possess the thinness of atomic monolayers. In our approach, the high osmotic performance arises from charge separation induced by the highly charged hBN surface rather than charge on the inner pore wall. Moreover, exploiting TCLB's capability of producing sub 10 nm pore arrays, we investigate the effects of pore-pore interaction on the overall power density. We find that an optimum pore-to-pore spacing of ∼500 nm is required to maintain an efficient selective transport mechanism.

Nanopores: a versatile tool to study protein dynamics

Proteins are the active workhorses in our body. These biomolecules perform all vital cellular functions from DNA replication and general biosynthesis to metabolic signaling and environmental sensing. While static 3D structures are now readily available, observing the functional cycle of proteins - involving conformational changes and interactions - remains very challenging, e.g., due to ensemble averaging. However, time-resolved information is crucial to gain a mechanistic understanding of protein function. Single-molecule techniques such as FRET and force spectroscopies provide answers but can be limited by the required labelling, a narrow time bandwidth, and more. Here, we describe electrical nanopore detection as a tool for probing protein dynamics. With a time bandwidth ranging from microseconds to hours, nanopore experiments cover an exceptionally wide range of timescales that is very relevant for protein function. First, we discuss the working principle of label-free nanopore experiments, various pore designs, instrumentation, and the characteristics of nanopore signals. In the second part, we review a few nanopore experiments that solved research questions in protein science, and we compare nanopores to other single-molecule techniques. We hope to make electrical nanopore sensing more accessible to the biochemical community, and to inspire new creative solutions to resolve a variety of protein dynamics - one molecule at a time.

Molecular basis for the activation of actinoporins by lipids

Actinoporins are a family of homologous pore forming proteins from sea anemones. They are one of the few families of eukaryotic toxins that have been characterized in depth. Actinoporins are activated by lipids in the context of bilayers, especially in cell and in model membranes containing the lipid sphingomyelin. These proteins must undergo conformational changes induced upon interaction with lipids in the membrane, where they form cytotoxic pores causing cell death and lethality. Herein we review a list of procedures and techniques to study this family of toxins, with the goal of elucidating the physicochemical, thermodynamic and structural basis for their activation by lipids. The emerging picture indicates that actinoporins undergo a stepwise process that includes binding to the membrane, oligomerization, and pore formation, in this order. The key transformation from the inactive oligomer to the active pore is catalyzed by sphingomyelin, explaining the key role of this lipid in the function of actinoporins.

Design and Assembly of Membrane-Spanning DNA Nanopores

Versatile lipid membrane-inserting nanopores have been made by functionalizing DNA nanostructures with hydrophobic tags. Here, we outline design and considerations to obtain DNA nanopores with the desired dimensions and conductance properties. We further provide guidance on their reconstitution into lipid membranes.

Preparation of Cytolysin A (ClyA) Nanopores

The ionic currents passing through nanopores can be used to sequence DNA and identify molecules at the single-molecule level. Recently, researchers have started using nanopores for the detection and analysis of proteins, providing a new platform for single-molecule enzymology studies and more efficient biomolecular sensing applications. For this approach, the homo-oligomeric Cytolysin A (ClyA) nanopore has been demonstrated as a powerful tool. Here, we describe a simple protocol allowing the production of ClyA nanopores. Monomers of ClyA are expressed in Escherichia coli and oligomerized in the presence of detergent. Subsequently, different oligomer variants are electrophoretically resolved and stored in a gel matrix for long-term use.

Breakdown of electroneutrality in nanopores

Ion transport in extremely narrow nanochannels has gained increasing interest in recent years due to unique physical properties at the nanoscale and the technological advances that allow us to study them. It is tempting to approach this confined regime with the theoretical tools and knowledge developed for membranes and microfluidic devices, and naively apply continuum models, such as the Poisson-Nernst-Planck and Navier-Stokes equations. However, it turns out that some of the most basic principles we take for granted in larger systems, such as the complete screening of surface charge by counter-ions, can break down under extreme confinement. We show that in a truly one-dimensional system of ions interacting with three-dimensional electrostatic interactions, the screening length is exponentially large, and can easily exceed the macroscopic length of a nanotube. Without screening, electroneutrality breaks down within the nanotube, with fundamental consequences for ion transport and electrokinetic phenomena. In this work, we build a general theoretical framework for electroneutrality breakdown in nanopores, focusing on the most interesting case of a one-dimensional nanotube, and show how it provides an elegant interpretation for the peculiar scaling observed in experimental measurements of ionic conductance in carbon nanotubes.

Exploring the confinement of polymer nanolayers into ordered mesoporous silica using advanced gas physisorption

Over the last two decades, in parallel to the rise of ordered mesoporous silica, porous nanostructured polymer-silica composites have attracted the interest of material scientists due to their promising perspectives of application as sorbents, ion-exchangers, supports, and catalysts. While knowledge is available regarding their synthesis and applications, understanding and controlling their pore properties in order to rationalize their performances remain challenging tasks. Greater knowledge is therefore needed regarding their precise characterization, especially using gas adsorption. To this aim, mesoporous polymer-silica nanocomposites were synthesized from two ordered mesoporous silica materials using a pore-surface restricted polymerization technique. Hydrophobic polystyrene, PS, and hydrophilic poly(2-hydroxyethyl methacrylate), PHEMA, were specifically confined and polymerized in the pores of high-quality SBA-15 and KIT-6 silicas of different pore sizes. The physico-chemical characteristics of the resulting hybrid materials were probed in detail using gas physisorption at cryogenic temperatures (Ar at 87 K and N₂ at 77 K). The polymer loadings and the interactions between the silica host and the polymer were investigated using thermogravimetric analysis coupled with differential thermal analysis (TGA-DTA) and attenuated total reflection infrared spectroscopy (ATR-FTIR). The effects of the pore structure, mode pore size and presence or absence of intra-wall pores in the silica hosts on the final composite characteristics were assessed as a function of the polymer type and loading. Two different polymer filling mechanisms were identified as a function of the polymer-silica interactions, resulting in important changes on the pore topology of the composites. The results of this study allow a better understanding of the nature of the confined interactions between hydrophilic and hydrophobic polymers and large pore mesoporous silicas and shed some light on fundamental aspects regarding the design of silica-based composites.

Controlling DNA Translocation Through Solid-state Nanopores

Compared with the status of bio-nanopores, there are still several challenges that need to be overcome before solid-state nanopores can be applied in commercial DNA sequencing. Low spatial and low temporal resolution are the two major challenges. Owing to restrictions on nanopore length and the solid-state nanopores' surface properties, there is still room for improving the spatial resolution. Meanwhile, DNA translocation is too fast under an electrical force, which results in the acquisition of few valid data points. The temporal resolution of solid-state nanopores could thus be enhanced if the DNA translocation speed is well controlled. In this mini-review, we briefly summarize the methods of improving spatial resolution and concentrate on controllable methods to promote the resolution of nanopore detection. In addition, we provide a perspective on the development of DNA sequencing by nanopores.

Isolated Pt single atomic sites anchored on nanoporous TiO2 film for highly efficient photocatalytic degradation of low concentration toluene

Single atom catalysts with atomically distributed active metal centers have attracted great attention owing to their maximum atom efficiency and excellent activity. Herein, we report a novel photocatalyst with isolated Pt single atomic sites anchored on nanoporous TiO₂ film prepared by a facile immersion and reduction method. HAADF-STEM, XPS, XANES and EXAFS results confirmed the anchoring of Pt single atomic sites on nanoporous TiO₂ film. The effects of immersion concentration of Pt, reduction temperature, relative humidity, inlet toluene concentration and residence time on photocatalytic degradation of low concentration toluene under UV and VUV irradiation were investigated. The results showed that the as-prepared catalyst had considerably high photocatalytic activity. The removal rate of toluene reached 45.88% under VUV irradiation when the inlet toluene concentration and residence time were 200 ppb and 0.3 s, respectively, which was 5.94 times that of pristine nanoporous TiO₂ film. The by-product ozone removal was greatly improved and the corresponding energy consumption was 0.01 kW·h/m³. While the removal rate of toluene increased with the decrease of inlet toluene concentration under UV irradiation. The Pt single atom catalyst exhibits significant potential for photocatalytic degradation of low concentration VOCs in indoor environments.

Durable, Stable, and Functional Nanopores Decorated by Self-Assembled Dipeptides

Nanopores have become an important tool for the detection and analysis of molecules at the single-molecule level. Surface modification of solid-state nanopores can improve their durability and efficiency. Peptides are ideal for surface modifications as they allow tailoring of multiple properties by a rational design of their sequence. Here, silicon nitride nanopores were coated by a dipeptide layer where a l-3,4-dihydroxyphenylalanine (DOPA) residue is the anchoring element and the other amino acid moiety is the functional element. DOPA binds tightly to many types of surfaces and allows a one-step functionalization of surfaces by simple immersion. As a result, the lifetime of coated nanopores increased from hours to months and the current-stability has significantly improved with respect to uncoated pores. This improvement is achieved by controlling the surface wettability and charge. Peptide-coated nanopores can be utilized as sensitive sensors that can be adjusted based on the choice of the functional moiety of the coated peptide. In addition, the coating slows down dsDNA translocation because of the DNA interaction with the pore coating.

Loop-Mediated Isothermal Amplification-Coupled Glass Nanopore Counting Toward Sensitive and Specific Nucleic Acid Testing

Solid-state nanopores have shown great promise and achieved tremendous success in label-free single-molecule analysis. However, there are three common challenges in solid-state nanopore sensors, including the nanopore size variations from batch to batch that makes the interpretation of the sensing results difficult, the incorporation of sensor specificity, and the impractical analysis time at low analyte concentration due to diffusion-limited mass transport. Here, we demonstrate a novel loop-mediated isothermal amplification (LAMP)-coupled glass nanopore counting strategy that could effectively address these challenges. By using the glass nanopore in the counting mode (versus the sizing mode), the device fabrication challenge is considerably eased since it allows a certain degree of pore size variations and no surface functionalization is needed. The specific molecule replication effectively breaks the diffusion-limited mass transport thanks to the exponential growth of the target molecules. We show the LAMP-coupled glass nanopore counting has the potential to be used in a qualitative test as well as in a quantitative nucleic acid test. This approach lends itself to most amplification strategies as long as the target template is specifically replicated in numbers. The highly sensitive and specific sensing strategy would open a new avenue for solid-state nanopore sensors toward a new form of compact, rapid, low-cost nucleic acid testing at the point of care.

Monitoring G-Quadruplex Formation with DNA Carriers and Solid-State Nanopores

G-quadruplexes (Gqs) are guanine-rich DNA structures formed by single-stranded DNA. They are of paramount significance to gene expression regulation, but also drug targets for cancer and human viruses. Current ensemble and single-molecule methods require fluorescent labels, which can affect Gq folding kinetics. Here we introduce, a single-molecule Gq nanopore assay (smGNA) to detect Gqs and kinetics of Gq formation. We use ∼5 nm solid-state nanopores to detect various Gq structural variants attached to designed DNA carriers. Gqs can be identified by localizing their positions along designed DNA carriers, establishing smGNA as a tool for Gq mapping. In addition, smGNA allows for discrimination of (un)folded Gq structures, provides insights into single-molecule kinetics of Gq folding, and probes quadruplex-to-duplex structural transitions. smGNA can elucidate the formation of Gqs at the single-molecule level without labeling and has potential implications on the study of these structures both in single-stranded DNA and in genomic samples.

DNA Nanotechnology for Building Sensors, Nanopores and Ion-Channels

DNA nanotechnology has revolutionised the capabilities to shape and control three-dimensional structures at the nanometre scale. Designer sensors, nanopores and ion-channels built from DNA have great potential for both cross-disciplinary research and applications. Here, we introduce the concept of structural DNA nanotechnology, including DNA origami, and give an overview of the work flow from design to assembly, characterisation and application of DNA-based functional systems. Chemical functionalisation of DNA has opened up pathways to transform static DNA structures into dynamic nanomechanical sensors. We further introduce nanopore sensing as a powerful label-free single-molecule technique and discuss how it can benefit from DNA nanotechnology. Especially exciting is the possibility to create membrane-inserted DNA nanochannels that mimic their protein-based natural counterparts in form and function. In this chapter we review the status quo of DNA sensors, nanopores and ion channels, highlighting opportunities and challenges for their future development.

Label-Free Detection of Post-translational Modifications with a Nanopore

Post-translational modifications (PTMs) of proteins play key roles in cellular processes. Hence, PTM identification is crucial for elucidating the mechanism of complex cellular processes and disease. Here we present a method for PTM detection at the single-molecule level using FraC biological nanopores. We focus on two major PTMs, phosphorylation and glycosylation, that mutually compete for protein modification sites, an important regulatory process that has been implicated in the pathogenic pathways of many diseases. We show that phosphorylated and glycosylated peptides can be clearly differentiated from nonmodified peptides by differences in the relative current blockade and dwell time in nanopore translocations. Furthermore, we show that these PTM modifications can be mutually differentiated, demonstrating the identification of phosphorylation and glycosylation in a label-free manner. The results represent an important step for the single-molecule, label-free identification of proteoforms, which have tremendous potential for disease diagnosis and cell biology.

Factorial two-stage analyses of parameters affecting the oil-gas interface and miscibility in bulk phase and nanopores

In this paper, a factorial analysis approach is applied to characterize the potential single and interactive factors as well as their effects on the interface and miscibility of three light oil-CO₂ systems under 32 different conditions. First, a modified Peng-Robinson equation of state coupled with the parachor model is applied to calculate the vapour-liquid equilibrium and interfacial tensions (IFTs) at a variation of pore radii and different pressures, based on which the MMPs are determined from the diminishing interface method. Second, by means of the factorial-analysis approach and calculated IFTs and minimum miscibility pressures (MMPs), the following five factors are specifically studied to evaluate their main and interactive effects on the IFTs and MMPs: temperature, initial oil and gas compositions, feed gas to oil ratio (feed GOR), and pore radius. It is found that the main and interactive effects of the five factors on the IFTs are inconsistent at different pressures. The effects of the five factors on the MMPs are evaluated quantitatively, which contribute to screen out significant factors, analyze interactions, and identify schemes for the miscible CO₂ enhanced oil recovery. The most positive significant main and interactive effects on the MMPs are Factors C (gas composition) and AB (temperature and oil composition), whereas the most negative results are Factors E (pore radius) and AC (temperature and gas compositions). A three-factor analysis indicates that the MMP is substantially reduced in small pores by controlling the percentage of the CH₄-dominated gas in the impure CO₂ sample and lowering the feed GOR.

The applications of nanopores in studies of proteins

Nanopores are a label-free platform with the ability to detect subtle changes in the activities of individual biomolecules under physiological conditions. Here, we comprehensively review the technological development of nanopores, focusing on their applications in studying the physicochemical properties and dynamic conformations of peptides, individual proteins, protein-protein complexes and protein-DNA complexes. This is followed by a brief discussion of the potential challenges that need to be overcome before the technology can be widely accepted by the scientific community. We believe that with continued refinement of the technology, significant understanding can be gained to help clarify the role of protein activities in the regulation of cellular physiology and pathogenesis.

DNA enrichment and tagmentation method for species-level identification and strain-level differentiation using ON-rep-seq

Despite the massive developments within culture-independent methods for detection of microorganisms during the last decade, culture-based methods remain a cornerstone in microbiology. Yet, the problem of rapid, accurate and inexpensive identification of bacterial isolates down to species/strain level remains unresolved. We have developed a new method for bacterial DNA enrichment and tagmentation allowing fast (<24 h) and cost-effective species level identification and strain level differentiation using the MinION portable sequencing platform (ON-rep-seq). DNA library preparation for 96 isolates takes less than 5 h and ensures highly reproducible distribution of reads that can be used to generate strain level specific read length counts profiles (LCp). We have developed a pipeline that by correcting reads error within peaks of LCp generates a set of high quality (>99%) consensus reads. Whereas, the information from high quality reads is used to retrieve species level taxonomy, comparison of LCp allows for strain level differentiation.

Tau-induced mitochondrial membrane perturbation is dependent upon cardiolipin

Misfolding and aggregate formation by the tau protein has been closely related with neurotoxicity in a large group of human neurodegenerative disorders, which includes Alzheimer's disease. Here, we investigate the membrane-active properties of tau oligomers on mitochondrial membranes, using minimalist in vitro model systems. Thus, exposure of isolated mitochondria to oligomeric tau evoked a disruption of mitochondrial membrane integrity, as evidenced by a combination of organelle swelling, efflux of cytochrome c and loss of the mitochondrial membrane potential. Tau-induced mitochondrial dysfunction occurred independently of the mitochondrial permeability transition (mPT) pore complex. Notably, mitochondria were rescued by pre-incubation with 10-N-nonyl acridine orange (NAO), a molecule that specifically binds cardiolipin (CL), the signature phospholipid of mitochondrial membranes. Additionally, NAO prevented direct binding of tau oligomers to isolated mitochondria. At the same time, tau proteins exhibited high affinity to CL-enriched membranes, whilst permeabilisation of lipid vesicles also strongly correlated with CL content. Intriguingly, using single-channel electrophysiology, we could demonstrate the formation of non-selective ion-conducting tau nanopores exhibiting multilevel conductances in mito-mimetic bilayers. Taken together, the data presented here advances a scenario in which toxic cytosolic entities of tau protein would target mitochondrial organelles by associating with their CL-rich membrane domains, leading to membrane poration and compromised mitochondrial structural integrity.

Early warning sensors for monitoring mercury in water

Poly-4-vinylpyridine grafted poly(vinylidene difluoride) (P4VP-g-PVDF) nanoporous polymer electrodes were found to be sensitive for Hg(II) analysis. The fabrication and characterization of functionalized nanoporous membrane-electrodes by FESEM and FTIR are presented. Functionalized nanopore charge state versus a large range of pH (1-10) was investigated by registering the streaming potential. This isoelectric point is achieved at the pKa of P4VP (pH = 5). Mercury adsorption at solid-liquid interface obeys a Langmuir law. A protocol for accurate Hg(II) analysis at ppb level was established. Calibration curves were performed and different real water samples (mineral water, ground water, surface water) were spiked and analyzed. The resulting sensor is intended to be integrated into existing systems or used standalone as portable devices. A first generation prototype exhibiting its own integrated potentiostat, its software and set of membrane-electrode pads is presented.

Current Enhancement in Solid-State Nanopores Depends on Three-Dimensional DNA Structure

The translocation of double-stranded DNA through a solid-state nanopore may either decrease or increase the ionic current depending on the ionic concentration of the surrounding solution. Below a certain crossover ionic concentration, the current change inverts from a current blockade to current enhancement. In this paper, we show that the crossover concentration for bundled DNA nanostructures composed of multiple connected DNA double-helices is lower than that of double-stranded DNA. Our measurements suggest that counterion mobility in the vicinity of DNA is reduced depending on the three-dimensional structure of the molecule. We further demonstrate that introducing neutral polymers such as polyethylene glycol into the measurement solution reduces electroosmotic outflow from the nanopore, allowing translocation of large DNA structures at low salt concentrations. Our experiments contribute to an improved understanding of ion transport in confined DNA environments, which is critical for the development of nanopore sensing techniques as well as synthetic membrane channels. Our salt-dependent measurements of model DNA nanostructures will guide the development of computational models of DNA translocation through nanopores.

Neuronal-like response of N2a living cells to nanoporous patterns of thin supported anodic alumina

We report about the response of N2a cells, a mouse neuroblastoma cell line, cultured on inert substrates with controlled porous nanostructure. The substrate surfaces were obtained by anodization and post-fabrication etching of thin aluminum films previously deposited onto glass. The morphology of the adherent cells was assessed by scanning electron microscopy. After fluorescent labelling, confocal microscopy was used to assess both the cell density, by cell nuclei counting, and their growth, by characterizing the neurite extensions in both number and length. By comparing with flat and smooth aluminum oxide, we can conclude that the nanoporous morphology of the anodized aluminum is favorable for cell development, which is probably correlated with the high density of regions with high local curvature. The intermediate pore size in the given range seems unfavorable for the number of cells, while the cell shape and the number of extensions point to a dominating differentiation of the N2a cells in correspondence with a characteristic pore size of 60 nm. These results are promising in view of the application of anodic alumina as a platform for the development of neuronal bioassays based on cell interconnectivity.

Natural and synthetic nanopores directing osteogenic differentiation of human stem cells

Bone regeneration is a highly orchestrated process crucial for endogenous healing procedures after accidents, infections or tumor therapy. Changes in surface nanotopography are known to directly affect the formation of osteogenic cell types, although no direct linkage to the endogenous nanotopography of bone was described so far. Here we show the presence of pores of 31.93 ± 0.97 nm diameter on the surface of collagen type I fibers, the organic component of bone, and demonstrate these pores to be sufficient to induce osteogenic differentiation of adult human stem cells. We further applied SiO₂ nanoparticles thermally cross-linked to a nanocomposite to artificially biomimic 31.93 ± 0.97 nm pores, which likewise led to in vitro production of bone mineral by adult human stem cells. Our findings show an endogenous mechanism of directing osteogenic differentiation of adult stem cells by nanotopological cues and provide a direct application using SiO₂ nanocomposites with surface nanotopography biomimicking native bone architecture.

Co-current crossflow microfiltration in a microchannel

Steady state crossflow microfiltration (CMF) is an important and often necessary means of particle separation and concentration for both industrial and biomedical processes. The factors controlling the performance of CMF have been extensively reviewed. A major factor is transmembrane pressure (TMP). Because microchannels have small height, they tend to have high pressure gradients in the feed-flow direction. In the extreme, these gradients may even reverse the pressure across the membrane (inciting backflow). It is therefore desirable to compensate for the effect of feed-flow on the TMP, aiming at constant transmembrane pressure (cTMP) at a value which maximizes filtrate flux. This is especially critical during filtration of deformable particles (e.g. erythrocytes) through low intrinsic resistance membranes. Filtration flux is generally taken to be directly proportional to TMP, with pressure drop along the channel decreasing in the flow direction. A co-current flow of filtrate in a suitably designed filtrate collecting channel is shown to allow the TMP to remain constant and permit the sieving surface to perform optimally, permitting up to twice as much filtration over that of a naïve configuration. Manipulation of the filtrate channel may be even more beneficial if it prevents backflow that might otherwise occur at the end of a sufficiently long channel. Experiments with erythrocyte suspensions, reported here, validate these concepts.

Influence of nanoporous titanium niobium alloy surfaces produced via hydrogen peroxide oxidative etching on the osteogenic differentiation of human mesenchymal stromal cells

Titanium niobium alloys exhibit a lower stiffness compared to Ti6Al4V, the 'gold standard' for load-bearing bone implants. Thus, the critical mismatch in stiffness between the implant and adjacent bone tissue could be addressed with TiNb alloys and thereby reduce stress shielding, which can result in bone resorption and subsequent implant loosening; however, the cellular response on the specific material is crucial for sufficient osseointegration. We therefore hypothesize that the response of human mesenchymal stromal cells (hMSC) and osteoblast-like cells on Ti45Nb surfaces can be improved by a novel nanoporous surface structure. For this purpose, an etching technique using hydrogen peroxide electrolyte solution was applied to Ti45Nb. The treated surfaces were characterized using SEM, LSM, AFM, nanoindentation, and contact angle measurements. Cell culture experiments using hMCS and MG-63 were conducted. The H₂O₂ treatment resulted in surface nanopores, an increase in surface wettability and a reduction in surface hardness. The proliferation of MG-63 was enhanced on TiNb45 compared to Ti6Al4V. MG-63 focal adhesion complexes were detected on all Ti45Nb surfaces, whereas the nanostructures notably increased the cell area and decreased cell solidity, indicating stimulated cell spreading and pseudopodia formation. Alizarin red stainings indicated that the nanoporous surfaces stimulated the osteogenic differentiation of hMSC. It can be concluded that the proposed surface treatment could potentially help to stimulate the osseointegration behaviour of the advantageous low stiff Ti45Nb alloy.

Receptor- and store-operated mechanisms of calcium entry during the nanosecond electric pulse-induced cellular response

Nanosecond electric pulses have been shown to open nanopores in the cell plasma membrane by fluorescent imaging of calcium uptake and fluorescent dyes, including propidium (Pr) iodide and YO-PRO-1 (YP₁). Recently, we demonstrated that nsEPs also induce the phosphoinositide intracellular signaling cascade by phosphatidylinositol-4,5-bisphosphate (PIP₂) depletion resulting in physiological responses similar to those observed following stimulation of G_q11-coupled receptors. In this paper, we explore the role of receptor- and store-operated calcium entry (ROCE/SOCE) mechanisms in the observed response of cells to nsEP. We show that addition of the ROCE/SOCE and transient receptor potential channel (TRPC) blocker gadolinium (Gd³⁺, 300 μM) slows PIP2 depletion following 1 and 20 nsEP exposures. Lipid rafts, regions of the plasma membrane rich in PIP₂ and TRPC, are also disrupted by nsEP exposure suggesting that ROCE/SOCE mechanisms are likely impacted. Reducing the expression of stromal interaction molecule 1 (STIM1) protein, a key protein in ROCE and SOCE, in cells exposure to nsEP resulted in a reduction in induced intracellular calcium rise. Additionally, after exposure to 1 and 20 nsEPs (16.2 kV/cm, 5 Hz), intracellular calcium rises were significantly reduced by the addition of GD³⁺ and SKF-96365 (1-[2-(4-methoxyphenyl)-2-[3-(4-methoxyphenyl) propoxy] ethyl-1H-imidazole hydrochloride, 100 μM), a blocker of STIM1 interaction. However, using similar nsEP exposure parameters, SKF-96365 was less effective at reducing YP₁ uptake compared to Gd³⁺. Thus, it is possible that SKF-96365 could block STIM1 interactions within the cell, while Gd³⁺ could acts on TRPC/nanopores from outside of the cell. Our results present evidence of nsEP induces ROCE and SOCE mechanisms and demonstrate that YP₁ and Ca²⁺ cannot be used solely as markers of nsEP-induced nanoporation.

Spontaneous water adsorption-desorption oscillations in mesoporous thin films

Understanding fluid transport and phase changes in nanopore structures is of great interest to many application fields, from energy conversion to water harvesting. This work discusses the spontaneous oscillations of the water saturation of mesoporous thin films, in the zone adjacent to a sessile water drop, at ambient conditions. The wetting-front dynamics onto the film is described by considering three coexisting phenomena: infiltration from the water drop, condensation from air vapor, and evaporation to the ambient. It was found that the oscillations follow spontaneous condensation-evaporation imbalances, which are governed by the hysteretic character of the adsorption-desorption behavior of the mesoporous material. The outcomes of this work provide insights on the complex interplay between water and nanopore structures, which has practical implications for the handling of humid microenvironments in lab-on-a-chip technology, as well as for many processes that take part of the cycle of water in nature.