ABSTRACT
In recent years, a number of novel pharmaceutical agents have received approval for the management of acute myeloid leukemia (AML). However, there is still ample opportunity for enhancing efficacy. The Wee1 inhibitor adavosertib (ADA) shows promise for the treatment of AML. Based on the effect of drugs on DNA damage, we conducted a combination study involving ADA and fimepinostat (CUDC-907), a dual inhibitor of PI3K and histone deacetylase (HDAC). We observed that the combination of CUDC-907 and ADA exhibited a synergistic effect in enhancing the antileukemic activity in both AML cell lines and primary patient samples, demonstrating through flow cytometry analysis and MTT assay, respectively. Additionally, our study revealed that CUDC-907 has the ability to augment ADA-induced DNA damage, as determined by the measurement of γH2AX levels and the implementation of the alkaline comet assay. Through the utilization of western blotting analyses, targeted inhibitors, and ectopic overexpression, we propose that the downregulation of Wee1, CHK1, RNR, and c-Myc are the potential mechanisms. Our data support the development of ADA in combination with CUDC-907 for the treatment of AML.
Subject(s)
Leukemia, Myeloid, Acute , Morpholines , Pyrazoles , Pyrimidines , Pyrimidinones , Sulfur Compounds , Humans , DNA Damage , Leukemia, Myeloid, Acute/drug therapyABSTRACT
Wormlike micelles (WLMs) are highly sensitive to alkanes, resulting in structural destruction and loss of viscosity. Therefore, the study of WLMs against alkanes holds great significant importance. Surface-active ionic liquids have shown increasing promise for different situations for customizing molecular structures with the specialty of flexible functional assembly. In this paper, we found that WLMs constructed from the long-chain fatty acid surface-active ionic liquid (N,N-dimethylbenzylamine-oleic acid, abbreviated as BD-OA) exhibit strengthened viscoelasticity with the introduction of alkanes, expanding the resistance range to alkane damage. Here, the rheological behavior, microstructure, and dissipative particle dynamics (DPD) simulations of BD-OA WLMs were investigated at macro-, micro-, and mesoscopic scales, before (and after) the introduction of alkane. Our findings confirm the structural transformation of the micellar system from WLMs to lamellar micelles with higher viscoelasticity after alkane induction. The rearrangement of the micelle configuration may be attributed to the infiltration of alkane molecules into the fence layer formed by the BD-OA WLMs, leading to an increase in the boundary accumulation parameter and ultimately resulting in the formation of lower curvature lamellar micelles. More importantly, the against alkanes BD-OA WLMs have exhibited excellent in enhanced oil recovery, which has a promise for substituting common oil-displacing agents in tertiary oil recovery processes.
ABSTRACT
To achieve the green, sustainable, and controllable recovery of oil-water resources and to address the limited functionality of single superwet materials in oil-water separation, this study reports a multifunctional oil-water separation strategy by compositing the underwater superoleophobic and underoil superhydrophobic materials (HS). The underwater superoleophobic quartz sands with an oil contact angle of 152.68° were prepared by adjusting the particle size. This material demonstrated a water flux of 4688 L m-2 h-1 and a low-density oil and water mixture separation efficiency of 98.6%, which remained above 97.9% over 50 cycles. It was effective in separating oil-in-water emulsions with a separation efficiency of >99%. For HS, quartz sands were modified with dodecyltrimethoxysilane. The optimized HS-4 exhibited superhydrophobic properties with a water contact angle of 157.06°. It achieved an oil flux of 5775 L m-2 h-1 and a water and dichloromethane mixture separation efficiency of 98.4%. Additionally, they exhibited significant potential in the separation of water-in-oil emulsions. Furthermore, by placing the underwater superoleophobic and underoil superhydrophobic units at the bottom of the filter, we achieved cyclic separation of high-density oil and water mixtures, low-density oil and water mixtures, water-in-oil emulsions, and oil-in-water emulsions. The separation efficiency consistently exceeded 96.5% over 10 cycles. In addition, the oil-water separation mechanism of underwater oleophobic and underoil hydrophobic materials was demonstrated by the relative concentration distribution of water and oil with molecular dynamics simulations. This intelligent oil-water separation method marks a significant advancement in the sustainable separation of diverse oil-water mixtures.
ABSTRACT
In this study, we employed high-throughput sequencing technology to determine the complete mitochondrial genomes of six ground beetles, encompassing five Harpalinae species and one Carabinae species. The sizes of mitochondrial genomes ranged from 15,334 to 16,972 bp, encompassing 37 genes, including 13 protein-coding genes, 22 transfer RNA genes, and 2 ribosomal RNA genes. Furthermore, each species was found to possess a putative control region. Combining with 65 published mitochondrial genome sequences of Carabidae as ingroups and four species from Trachypachidae, Gyrinidae and Dytiscidae as outgroups, we conducted phylogenetic analyses utilizing Maximum likelihood and Bayesian inference methods. Moreover, we reconstructed a species tree of Carabidae based on mitochondrial genome data using the coalescent-based species tree method (ASTRAL). The results revealed that the family Carabidae was not a monophyletic group. The subfamily Harpalinae was supported to be a monophyletic group in Maximum likelihood analysis. Although the subfamily Carabinae was found to be nonmonophyletic in the concatenation analyses under both Maximum likelihood and Bayesian inference criteria, it was identified as a monophyletic group in the species tree analysis.
Subject(s)
Coleoptera , Genome, Mitochondrial , Animals , Phylogeny , Coleoptera/genetics , Bayes TheoremABSTRACT
Parkinson's disease (PD) is a progressive neurodegenerative disorder causing the loss of dopaminergic neurons in the substantia nigra and the drastic depletion of dopamine (DA) in the striatum; thus, DA can act as a marker for PD diagnosis and therapeutic evaluation. However, detecting DA in the brain is not easy because of its low concentration and difficulty in sampling. In this work, we report the fabrication of a covalent organic framework (COF)-modified carbon fiber microelectrode (cCFE) that enables the real-time detection of DA in the mouse brain thanks to the outstanding antibiofouling and antichemical fouling ability, excellent analytical selectivity, and sensitivity offered by the COF modification. In particular, the COF can inhibit the polymerization of DA on the electrode (namely, chemical fouling) by spatially confining the molecular conformation and electrochemical oxidation of DA. The cCFE can stably and continuously work in the mouse brain to detect DA and monitor the variation of its concentration. Furthermore, it was combined with levodopa administration to devise a closed-loop feedback mode for PD diagnosis and therapy, in which the cCFE real-time monitors the concentration of DA in the PD model mouse brain to instruct the dose and injection time of levodopa, allowing a customized medication to improve therapeutic efficacy and meanwhile avoid adverse side effects. This work demonstrates the fascinating properties of a COF in fabricating electrochemical sensors for in vivo bioanalysis. We believe that the COF with structural tunability and diversity will offer enormous promise for selective detection of neurotransmitters in the brain.
Subject(s)
Metal-Organic Frameworks , Parkinson Disease , Mice , Animals , Dopamine/analysis , Parkinson Disease/drug therapy , Levodopa/therapeutic use , Levodopa/pharmacology , Metal-Organic Frameworks/therapeutic use , Microelectrodes , BrainABSTRACT
OBJECTIVE: Diffuse midline glioma, H3 K27-altered (DMG) is a lethal pediatric brainstem tumor. Despite numerous efforts to improve survival benefits, its prognosis remains poor. This study aimed to design and synthesize a novel CDK4/6 inhibitor YF-PRJ8-1011, which exhibited more potent antitumor activity against a panel of patient-derived DMG tumor cells in vitro and in vivo compared with palbociclib. METHODS: Patient-derived DMG cells were used to assess the antitumor efficacy of YF-PRJ8-1011 in vitro. The liquid chromatography tandem-mass spectrometry method was used to measure the activity of YF-PRJ8-1011 passing through the blood-brain barrier. DMG patient-derived xenograft models were established to detect the antitumor efficacy of YF-PRJ8-1011. RESULTS: The results showed that YF-PRJ8-1011 could inhibit the growth of DMG cells both in vitro and in vivo. YF-PRJ8-1011 could well penetrate the blood-brain barrier. It also significantly inhibited the growth of DMG tumors and prolonged the overall survival of mice compared with vehicle or palbociclib. Most notably, it exerted potent antitumor efficacy in DMG in vitro and in vivo compared with palbociclib. In addition, we also found that YF-PRJ8-1011 combined with radiotherapy also showed more significant inhibition of DMG xenograft tumor growth than radiotherapy alone. CONCLUSION: Collectively, YF-PRJ8-1011 is a novel, safe, and selective CDK4/6 inhibitor for DMG treatment.
Subject(s)
Brain Stem Neoplasms , Glioma , Humans , Mice , Animals , Glioma/drug therapy , Glioma/radiotherapy , Cyclin-Dependent Kinase 4ABSTRACT
Because of high sensitivity and specificity, isothermal nucleic acid amplification are widely applied in many fields. To facilitate and improve their performance, various nanomaterials, like nanoparticles, nanowires, nanosheets, nanotubes, and nanoporous films are introduced in isothermal nucleic acid amplification. However, the specific application, roles, and prospect of nanomaterials in isothermal nucleic acid amplification have not been comprehensively reviewed. Here, the application of different nanomaterials (0D, 1D, 2D, and 3D) in isothermal nucleic acid amplification is comprehensively discussed and recent progress in the field is summarized. The nanomaterials are mainly used for reaction enhancer, signal generation/amplification, or surface loading carriers. In addition, 3D nanomaterials can be also functioned as isolated chambers for digital nucleic acid amplification and the tools for DNA sequencing of amplified products. Challenges and future recommendations are also proposed to be better used for recent covid-19 detection, point-of-care diagnostic, food safety, and other fields.
Subject(s)
COVID-19 , Nanostructures , Nucleic Acids , Humans , Nucleic Acid Amplification Techniques , SARS-CoV-2ABSTRACT
We propose a system to eliminate the graininess of an integral imaging 3D display by using a transmissive mirror device (TMD). The proposed system consists of a 2D display, a micro-lens array (MLA), and a TMD. The TMD comprises square apertures with mirror-reflective inner wall. The light rays pass through the square aperture to form a diffraction spot, and the diffraction light intensity has a Sinc-function distribution. Therefore, the TMD can be used as an optical low-pass filter. In a certain imaging range, the mainlobe of the Sinc-function distribution is almost unchanged. The TMD has the property of a volumetric optical low-pass filter. It can interpolate the interval between discrete 3D pixels. Therefore, the TMD can be used to eliminate the graininess. The resolution of the 3D image is improved by 2.12 times. The experimental results verify the feasibility of the proposed system.
ABSTRACT
With the rapid development of immunotherapy, the efficacy and feasibility of neoadjuvant immunotherapy for early resectable non-small-cell lung cancer (NSCLC) has been demonstrated. However, there are still difficulties and controversies in evaluating the efficacy of neoadjuvant immunotherapy. In our report, we described a 43-year-old female patient who was diagnosed with stage IIIA (cT1N2M0) pulmonary adenocarcinoma. After two cycles of neoadjuvant immunotherapy (sintilimab) combined with chemotherapy, according to imaging evaluation, the efficacy of the primary lesion was evaluated as stable disease and the mediastinal lymph nodes were evaluated as partial response. However, the postoperative pathological evaluation showed the primary lesion was pathological complete response and the mediastinal lymph nodes were major pathological response. This indicated that neoadjuvant chemo-immunotherapy was effective for both primary and mediastinal lymph nodes, but regression of the lesions was not synchronous. This study provided a complete process of neoadjuvant treatment, illustrating the effectiveness and safety of neoadjuvant chemo-immunotherapy to a certain extent. It is also suggested that the evaluation of neoadjuvant immunotherapy should be combined with imaging and pathology, and the primary tumor and lymph nodes should be evaluated, respectively.
Subject(s)
Antibodies, Monoclonal, Humanized/therapeutic use , Carcinoma, Non-Small-Cell Lung/drug therapy , Lung Neoplasms/drug therapy , Adult , Antibodies, Monoclonal, Humanized/administration & dosage , Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Carcinoma, Non-Small-Cell Lung/pathology , Carcinoma, Non-Small-Cell Lung/surgery , Female , Humans , Lung Neoplasms/pathology , Lung Neoplasms/surgery , Lymph Nodes/pathology , Lymphatic Metastasis/pathology , Neoadjuvant Therapy , Neoplasm StagingABSTRACT
High-precision aspherical cylindrical (acylindrical) lenses are difficult to directly measure because of the phase deviation in the off-axis region. To achieve rapid and non-contact measurement of the acylindrical lens surface, a novel optical structure phase measurement, to the best of our knowledge, is presented in this work. Both common finite-difference and noise-reduction finite-difference methods were used for solving the transport of intensity equation (TIE) for reconstruction of high-resolution surface measurement. The results suggest that both common finite-difference and noise-reduction finite-difference methods can obtain good measurement results. The proposed method allows for the direct measurement of surface information without interference stitching. The accuracy of the TIE measurement has been verified through direct contact measurement.
ABSTRACT
Programmable engineered DNA origami provides infinite possibilities for customizing nanostructures with controllable precision and configurable functionality. Here, a strategy for fabricating an amphiphilic triangular DNA origami with a central nanopore that integrates phase-stabilizing, porous-gated, and affinity-delivering effects is presented. By introducing the DNA origami as a single-component surfactant, the water-in-oil-in-water (W/O/W) emulsion is effectively stabilized with decreased interfacial tension. Microscopic observation validates the attachment of the DNA origami onto the water-in-oil and oil-in-water interfaces. Furthermore, fluorescence studies and molecular docking simulations indicate the binding interactions of DNA origami with arbutin and coumaric acid at docking sites within central nanopores. These central nanopores are functionalized as molecular gates and affinity-based scaffold for the zero-order release of arbutin and coumaric acid at a constant rate regardless of concentration gradient throughout the whole releasing period. In vivo zebrafish results illustrate the advantages of this zero-order release for anti-melanogenesis therapy over direct exposure or Fickian diffusion. The DNA origami-based W/O/W emulsion presents anti-melanogenic effects against UV-B exposure without cardiotoxicity or motor toxicity. These results demonstrate that this non-toxic amphiphilic triangular DNA origami is capable of solely stabilizing the W/O/W emulsion as well as serving as nanopore gates and affinity-based scaffold for constant release.
Subject(s)
Nanopores , Nanostructures , Animals , DNA , Emulsions , Molecular Docking Simulation , Nucleic Acid Conformation , ZebrafishABSTRACT
BACKGROUND: Boscalid is often used to extend the storage time of postharvest cherry tomato. Pesticide residue has become an issue of food safety. This study sought to investigate the spatial distribution of boscalid residue in cherry tomato fruits and to determine the effect of 24-epibrassinolide (EBR) in promoting boscalid degradation. RESULTS: Boscalid could quickly penetrate into cherry tomatoes, but mainly remained in the peel. The migration of boscalid from the peel into the core was a time-consuming and complex process during storage. After 72 h, boscalid residues in the pulp and the core began to accumulate gradually. The exogenous application of EBR activated peroxidase, glutathione reductase and glutathione S-transferase, and effectively promoted the degradation of boscalid by a maximum decrease of 44.8% in peel, 54.0% in pulp and 71.2% in core. CONCLUSION: As one of the common pesticides, boscalid had a strong ability to enter the cherry tomato and thus become a potential risk for public consumption. Therefore, rational use of pesticides is recommended. The results of this study indicate that the possible risk of boscalid residue could be alleviated by EBR pretreatment through activating detoxification enzymes. © 2020 Society of Chemical Industry.
Subject(s)
Biphenyl Compounds/metabolism , Brassinosteroids/pharmacology , Fungicides, Industrial/metabolism , Niacinamide/analogs & derivatives , Plant Proteins/metabolism , Solanum lycopersicum/enzymology , Steroids, Heterocyclic/pharmacology , Biphenyl Compounds/chemistry , Enzyme Activation/drug effects , Fruit/chemistry , Fruit/drug effects , Fruit/enzymology , Fruit/metabolism , Fungicides, Industrial/chemistry , Glutathione Reductase/metabolism , Glutathione Transferase/metabolism , Solanum lycopersicum/chemistry , Solanum lycopersicum/drug effects , Solanum lycopersicum/metabolism , Niacinamide/chemistry , Niacinamide/metabolism , Peroxidase/metabolism , Pesticide Residues/chemistry , Pesticide Residues/metabolismABSTRACT
Raman spectroscopy and surface-enhanced Raman spectroscopy (SERS) have been extensively explored in the design of accurate, transparent, and conclusive food safety and quality control assays. Its hyphenation with chemometric algorithms is instrumental in securing safe food campaigns. To provide valuable recommendations and meet the growing demands for food screening, the current study begins with a brief description of the Raman spectroscopy and SERS theory followed by a comprehensive overview of spectral preprocessing, qualitative algorithms, variable selection methods, and quantitative algorithms. The review emphasizes on the importance of food monitoring practices using multivariate regression models. The applicability of the distinct chemometrics modes toward monitoring pesticide, food and illicit additives, heavy metals, pathogens, and its metabolites in Raman spectroscopy and SERS is covered in dairy, poultry, oil, honey, beverages, and other selected food matrices. Its pertinence toward classification and/or discrimination in food quality and safety monitoring and authentication is examined. Finally, it also complies with the limitations, key challenges, and prospects. The chemometrics processing spectra implemented with simpler or no complicated sample pretreatment step make Raman spectroscopy/SERS technique a potential approach that is expected to achieve simultaneous and fast detection of multiple analytes in food matrices.
Subject(s)
Pesticides , Spectrum Analysis, Raman , Algorithms , Food Quality , Food SafetyABSTRACT
BACKGROUND: Intermittent hypoxia (IH), a hallmark of obstructive sleep apnea (OSA), is prevalent in older adults and associated with inflammation. We previously showed that IH induces renal fibrosis and cardiomyopathy and hypothesized that lung inflammatory changes may underlie deficits in pulmonary function in OSA. METHODS: Pulmonary inflammatory and oxidative markers were assessed in metallothionein KO (MT-KO) mice and WT 129S1 controls exposed to IH or to normoxia for 8 weeks. RESULTS: MT expression increased at 3 days in WT, falling back at 1 week. Pro-fibrotic markers CTGF and PAI-1 were unchanged in WT, but increased at 3 or 8 weeks, with enhanced Sirius Red staining at 8 weeks, in IH-exposed MT-KO. Cellular infiltration, TNF-α and IL-6 increased earlier in IH-exposed MT-KO than in WT. Oxidative markers, 3-nitrotyrosine and 4-hydroxynonenal increased in both but persisted in MT-KO. Antioxidant Nrf2, HO-1 and NQO1, increased at 3 days in WT mice and at 8 weeks IH in MT-KO. While early Nrf2 induction required MT, its later increase at 8 weeks in MT-KO was independent from MT. CONCLUSIONS: We conclude that early MT and antioxidant gene response protects from fibrotic changes in long-term IH-exposed mouse lung. Without this response, pulmonary fibrosis may develop with longer IH exposure.
Subject(s)
Hypoxia/metabolism , Lung Injury/metabolism , Metallothionein/metabolism , Animals , Hypoxia/complications , Hypoxia/pathology , Interleukin-6/metabolism , Lung/metabolism , Lung/pathology , Lung Injury/etiology , Lung Injury/pathology , Metallothionein/genetics , Mice, Knockout , Oxidative Stress , Tumor Necrosis Factor-alpha/metabolismABSTRACT
The selective electrochemical determination of fluoride is reported by phenylboronic acid-functionalized vertically ordered mesoporous silica film attached to the indium tin oxide electrode, designed as PBA-VMSF/ITO. Fluoride ion can selectively bind to phenylboronic acid to generate boronate anions, leading to negative charges inside the ultrasmall nanochannel of VMSF and ultimately rejecting the access of potassium ferricyanide ions to the electrode surface. By recording the reduced electrochemical signal of potassium ferricyanide, determination of fluoride ion in aqueous solution was achieved with a fast response, wide response range, and high selectivity. Furthermore, with the specific recognition of PBA and anti-fouling ability of VMSF, the PBA-VMSF/ITO sensor has been successfully used to detect fluoride ion in tap water.
Subject(s)
Boronic Acids/chemistry , Drinking Water/analysis , Electrochemical Techniques/methods , Fluorides/analysis , Silicon Dioxide/chemistry , Electrochemical Techniques/instrumentation , Electrodes , Limit of Detection , Porosity , Tin Compounds/chemistryABSTRACT
Foodborne pathogen contamination has become a severe threat to human health. Traditional methods for foodborne pathogen detection have several disadvantages, including long detection time, low sensitivity, and low selectivity. The emergence of multiple excellent nanomaterials enables the construction of novel biosensors for foodborne pathogen detection. Based on the outstanding properties of nanomaterials, the novel biosensors possess the advantages of sensitivity, specificity, rapidity, accuracy, and simplicity. The present review comprehensively summarizes the advanced biosensors, including electrochemical, colorimetric, fluorescent, and surface enhanced Raman scattering biosensors for sensing key foodborne pathogens in recent decades. Furthermore, several issues are identified for further exploration, and possible directions for the development of biosensors are discussed.
Subject(s)
Biosensing Techniques/instrumentation , Food Microbiology/instrumentation , Nanostructures , Bacteria/isolation & purification , Biosensing Techniques/methods , Food Contamination/analysis , Food Microbiology/methodsABSTRACT
Model coliphages (e.g., ΦX174, MS2, and PRD1) have been widely used as surrogates to study the fate and transport of pathogenic viruses in the environment and during wastewater treatment. Two groups of coliphages (F-specific and somatic) are being explored as indicators of viral fecal pollution in ambient water. However, the detection and quantification of coliphages still largely rely on time-consuming culture-based plaque assays. In this study, we developed an in-gel loop-mediated isothermal amplification (gLAMP) system enabling coliphage MS2 quantification within 30 min using standard laboratory devices. Viral particles (MS2) were immobilized with LAMP reagents in polyethylene glycol hydrogel, and then viral RNAs were amplified through a LAMP reaction. Due to the restriction effect of the hydrogel matrix, one viral particle would only produce one amplicon dot. Therefore, the sample virus concentrations can be determined based on the number of fluorescent amplicon dots using a smartphone for imaging. The method was validated by using artificially spiked and naturally contaminated water samples. gLAMP results were shown to correlate well with plaque assay counts ( R2 = 0.984, p < 0.05) and achieved similar sensitivity to quantitative reverse-transcription polymerase chain reaction (RT-qPCR; 1 plaque-forming unit per reaction). Moreover, gLAMP demonstrated a high level of tolerance against inhibitors naturally present in wastewater, in which RT-qPCR was completely inhibited. Besides MS2, gLAMP can also be used for the quantification of other microbial targets (e.g., Escherichia coli and Salmonella). Considering its simplicity, sensitivity, rapidity, and versatility, gLAMP holds great potential for microbial water-quality analysis, especially in resource-limited settings.
Subject(s)
Levivirus , Smartphone , Coliphages , Real-Time Polymerase Chain Reaction , Sensitivity and Specificity , Water PollutionABSTRACT
Metoprolol (MTP) is one of the most widely used antihypertensive drugs yet banned to use in sport competition. Therefore, there has been an increasing demand for developing simple, rapid, and sensitive methods suited to the identification and quantification of MTP in human biofluids. In this work, ultrathin silica nanochannel membrane (SNM) with perforated channels was employed to support nanoscale liquid/liquid interface (nano-ITIES) array for investigation of the ion-transfer voltammetric behavior of MTP and for its detection in multiple human biofluids and pharmaceutical formulation. Several potential interfering substances, including small molecules, d-glucose, urea, ascorbic acid, glycine, magnesium chloride, sodium sulfate and large molecules, bovine serum albumin (BSA), were chosen as models of biological interferences to examine their influence on the ion-transfer current signal of MTP. The results confirmed that the steady-state current wave barely changed in the presence of small molecules. Although BSA displayed an apparent blockade on the transfer of MTP, the accurate determination of MTP in multiple human biofluids (i.e., urine, serum and whole blood) and pharmaceutical formulation were still feasible, thanks to the molecular sieving and antifouling abilities of SNM. A limit of detection (LOD) within the physiological level of MTP during therapy could be achieved for all cases, i.e., 0.5 and 1.1 µM for 100 times diluted urine and serum, respectively, and 2.2 µM for 1000 times diluted blood samples. These results demonstrated that the nano-ITIES array behaved as a simplified and integrated detection platform for ionizable drug analysis in complex media.
Subject(s)
Body Fluids/chemistry , Electrochemical Techniques , Metoprolol/analysis , Pharmaceutical Preparations/chemistry , Humans , Nanostructures/chemistry , Particle Size , Silicon Dioxide/chemistry , Tablets/chemistryABSTRACT
An ideal molecular filtration membranes should be highly permeable and selective, thus desiring the membranes to be ultrathin, be highly porous, and consists of small and uniform pores or channels. In this work, we report the molecular filtration by free-standing ultrathin silica nanochannel membranes (SNMs) using a U-shaped cell and spectrophotometric detection, focusing on the quantitative evaluation of permeability and selectivity of SNMs. Thanks to the ultrasmall channel size, namely, â¼2-3 nm, and the negatively charged channel surface arising from the deprotonation of silanol groups, the SNM displayed excellent size and charge selectivity for molecular filtration. The selectivity coefficient for separation of small methyl viologen from large cytochrome c is as high as 273, because of the uniform pore/channel size. The charge-based filtration can be modulated by the salt concentration and solution pH, which control the overlap of radial electrical double layer and surface charge sign/density, respectively. Owing to the high relative pore density, namely, 16.7%, and the straight and vertical channel orientation, the SNM is highly permeable, displaying a molecule flux much higher than commercially available dialysis membrane and others reported previously. In addition, we demonstrated that, by biasing a small voltage across the SNM, both the flux and separation selectivity could be significantly enhanced.
ABSTRACT
Free-standing silica nanochannel membrane (SNM) with perforated channels was utilized to create arrays of nanoscale interfaces between two immiscible electrolyte solutions (nano-ITIES), at which permselective ion transfer and detection were achieved. The SNM consisted of a high density of straight nanochannels with a diameter of 2-3 nm and a length of 70 nm. The silicon wafer coated by 150 nm-thick porous silicon nitride film (p-SiNF) with pores of 5 µm-in-diameter was used to support the SNM in a form of nanochannel-on-micropore. Considering the material surface lipophilicity, the nano-ITIES array was formed at the boundary between SNM and p-SiNF, with a diffusion geometry equivalent to two back-to-back inlaid microdisc interfaces. Thus, the transfer of tetraethylammonium (TEA(+)) across the nano-ITIES array yielded symmetric sigmoidal current responses. In addition, because of the ultrasmall size and negatively charged surface of silica nanochannels, the nano-ITIES displayed obvious size and charge permselectivities. Transfer of ions with a size comparable with or larger than the nanochannel was sterically blocked. Also that of anions with a size smaller than the nanochannels encountered the strong electrostatic repulsion from channel walls, showing obvious dependence on the ionic strength of aqueous solution. The present approach is facile and inexpensive for building a nano-ITIES array with potential applications in ion detection and separation.