Effect of Membrane Permeance and System Parameters on the Removal of Protein-Bound Uremic Toxins in Hemodialysis

Inadequate clearance of protein-bound uremic toxins (PBUTs) during dialysis is associated with morbidities in chronic kidney disease patients. The development of high-permeance membranes made from materials such as graphene raises the question whether they could enable the design of dialyzers with improved PBUT clearance. Here, we develop device-level and multi-compartment (body) system-level models that account for PBUT-albumin binding (specifically indoxyl sulfate and p-cresyl sulfate) and diffusive and convective transport of toxins to investigate how the overall membrane permeance (or area) and system parameters including flow rates and ultrafiltration affect PBUT clearance in hemodialysis. Our simulation results indicate that, in contrast to urea clearance, PBUT clearance in current dialyzers is mass-transfer limited: Assuming that the membrane resistance is dominant, raising PBUT permeance from 3 × 10-6 to 10-5 m s-1 (or equivalently, 3.3 × increase in membrane area from ~ 2 to ~ 6 m2) increases PBUT removal by 48% (from 22 to 33%, i.e., ~ 0.15 to ~ 0.22 g per session), whereas increasing dialysate flow rates or adding adsorptive species have no substantial impact on PBUT removal unless permeance is above ~ 10-5 m s-1. Our results guide the future development of membranes, dialyzers, and operational parameters that could enhance PBUT clearance and improve patient outcomes.

Cascaded compression of size distribution of nanopores in monolayer graphene

Monolayer graphene with nanometre-scale pores, atomically thin thickness and remarkable mechanical properties provides wide-ranging opportunities for applications in ion and molecular separations1, energy storage2 and electronics3. Because the performance of these applications relies heavily on the size of the nanopores, it is desirable to design and engineer with precision a suitable nanopore size with narrow size distributions. However, conventional top-down processes often yield log-normal distributions with long tails, particularly at the sub-nanometre scale4. Moreover, the size distribution and density of the nanopores are often intrinsically intercorrelated, leading to a trade-off between the two that substantially limits their applications5-9. Here we report a cascaded compression approach to narrowing the size distribution of nanopores with left skewness and ultrasmall tail deviation, while keeping the density of nanopores increasing at each compression cycle. The formation of nanopores is split into many small steps, in each of which the size distribution of all the existing nanopores is compressed by a combination of shrinkage and expansion and, at the same time as expansion, a new batch of nanopores is created, leading to increased nanopore density by each cycle. As a result, high-density nanopores in monolayer graphene with a left-skewed, short-tail size distribution are obtained that show ultrafast and ångström-size-tunable selective transport of ions and molecules, breaking the limitation of the conventional log-normal size distribution9,10. This method allows for independent control of several metrics of the generated nanopores, including the density, mean diameter, standard deviation and skewness of the size distribution, which will lead to the next leap in nanotechnology.

More than magnetic isolation: Dynabeads as strong Raman reporters towards simultaneous capture and identification of targets

Dynabeads are superparamagnetic particles used for immunomagnetic purification of cells and biomolecules. Post-capture, however, target identification relies on tedious culturing, fluorescence staining and/or target amplification. Raman spectroscopy presents a rapid detection alternative, but current implementations target cells themselves with weak Raman signals. We present antibody-coated Dynabeads as strong Raman reporter labels whose effect can be considered a Raman parallel of immunofluorescent probes. Recent developments in techniques for separating target-bound Dynabeads from unbound Dynabeads makes such an implementation feasible with high specificity. We deploy Dynabeads anti-Salmonella to bind and identify Salmonella enterica, a major foodborne pathogen. Dynabeads present major peaks around 1000 and 1600 cm-1 from aliphatic and aromatic C-C stretching of the polystyrene coating and near 1350 cm-1 from the ɣ-Fe2O3 and Fe3O4 core, confirmed with electron dispersive X-ray (EDX) imaging. Minor to no contributions are made from the surface antibodies themselves as confirmed by Raman analysis of surface-activated, antibody-free beads. Dynabeads' Raman signature can be measured in dry and liquid samples even at single shot ~30 × 30 μm area imaging using 0.5 s, 7 mW laser acquisition with single and clustered beads providing a 44- and 68-fold larger Raman intensity compared to signature from cells. Higher polystyrene and iron oxide content in clusters yields larger signal intensity and conjugation to bacteria strengthens clustering as a bacterium can bind to more than one bead as observed via transmission electron microscopy (TEM). Our findings shed light on the intrinsic Raman reporter nature of Dynabeads. When combined with emerging techniques for the separation of target-bound Dynabeads from unbound Dynabeads such as using centrifugation through a density media bi-layer, they have potential to demonstrate their dual function for target isolation and detection without tedious staining steps or unique plasmonic substrate engineering, advancing their applications in heterogeneous samples like food, water, and blood.

Longitudinal Assessment of Left Ventricular Function in Patients with Myopericarditis After mRNA COVID-19 Vaccination

BACKGROUND

Multiple reports have described myopericarditis following mRNA COVID-19 vaccination. However, data on the persistence of subclinical myocardial injury assessed by left ventricular (LV) longitudinal strain (LVLS) is limited.

OBJECTIVES

Our aim was to assess LV function longitudinally in our cohort of COVID-19 vaccine-related myopericarditis using ejection fraction (EF), fractional shortening (FS), LVLS, and diastolic parameters.

METHODS

Retrospective, single-center review of demographic, laboratory, and management data was performed on 20 patients meeting diagnostic criteria for myopericarditis after mRNA COVID-19 vaccination. Echocardiographic images were obtained on initial presentation (time 0), at a median of 12 days (7.5, 18.5; time 1), and at a median of 44 days (29.5, 83.5; time 2). FS was calculated by M-mode, EF by 5/6 area-length methods, LVLS by utilization of TOMTEC software, and diastolic function by tissue Doppler. All parameters were compared across pairs of these time points using Wilcoxon signed-rank test.

RESULTS

Our cohort consisted predominantly of adolescent males (85%) with mild presentation of myopericarditis. The median EF was 61.6% (54.6, 68.0), 63.8% (60.7, 68.3), 61.4% (60.1, 64.6) at times 0, 1, and 2, respectively. Upon initial presentation, 47% of our cohort had LVLS < -18%. The median LVLS was -18.6% (-16.9, -21.0) at time 0, -21.2% at time 1 (-19.4, -23.5) (p = 0.004) and -20.8% (-18.7, -21.7) at time 2 (p = 0.004, as compared to time 0).

CONCLUSIONS

Though many of our patients had abnormal strain during acute illness, LVLS improved longitudinally, indicating myocardial recovery. LVLS can be used as marker of subclinical myocardial injury and risk stratification in this population.

Molecular Self-Assembly Enables Tuning of Nanopores in Atomically Thin Graphene Membranes for Highly Selective Transport

Atomically thin membranes comprising nanopores in a 2D material promise to surpass the performance of polymeric membranes in several critical applications, including water purification, chemical and gas separations, and energy harvesting. However, fabrication of membranes with precise pore size distributions that provide exceptionally high selectivity and permeance in a scalable framework remains an outstanding challenge. Circumventing these constraints, here, a platform technology is developed that harnesses the ability of oppositely charged polyelectrolytes to self-assemble preferentially across larger, relatively leaky atomically thin nanopores by exploiting the lower steric hindrance of such larger pores to molecular interactions across the pores. By selectively tightening the pore size distribution in this manner, self-assembly of oppositely charged polyelectrolytes simultaneously introduced on opposite sides of nanoporous graphene membranes is demonstrated to discriminate between nanopores to seal non-selective transport channels, while minimally compromising smaller, water-selective pores, thereby remarkably attenuating solute leakage. This improved membrane selectivity enables desalination across centimeter-scale nanoporous graphene with 99.7% and >90% rejection of MgSO₄ and NaCl, respectively, under forward osmosis. These findings provide a versatile strategy to augment the performance of nanoporous atomically thin membranes and present intriguing possibilities of controlling reactions across 2D materials via exclusive exploitation of pore size-dependent intermolecular interactions.

Nonlinear ion transport mediated by induced charge in ultrathin nanoporous membranes

Ultrathin membranes with nanoporous conduits show promise for ionic separations and desalination applications, but the mechanisms underlying the nonlinear ionic transport observed in these systems are not well understood. Here, we demonstrate how induced charge at membrane interfaces can lead to nonlinear ionic transport and voltage-dependent conductance through such channels. The application of an electric field on a polarizable membrane leads to induced charges at the membrane interfaces. The induced charges in turn are screened by diffuse charges in the electrolyte, which are acted upon by the electric field. For extremely thin membranes, the induced charge effect can be significant even for moderate applied voltages commonly used in experiments. We apply a continuum Poisson-Nernst-Planck model to characterize the current-voltage behavior of ultrathin membranes over a wide parameter space. The predictions of the model are compared to recent experiments on graphene and MoS_{2} membranes in an electric field. We expect the role of induced charge to be especially pronounced in the limit of atomically thin membranes.

Highly porous nanofiber-supported monolayer graphene membranes for ultrafast organic solvent nanofiltration

Scalable fabrication of monolayer graphene membrane on porous supports is key to realizing practical applications of atomically thin membranes, but it is technologically challenging. Here, we demonstrate a facile and versatile electrospinning approach to realize nanoporous graphene membranes on different polymeric supports with high porosity for efficient diffusion- and pressure-driven separations. The conductive graphene works as an excellent receptor for deposition of highly porous nanofibers during electrospinning, thereby enabling direct attachment of graphene to the support. A universal “binder” additive is shown to enhance adhesion between the graphene layer and polymeric supports, resulting in high graphene coverage on nanofibers made from different polymers. After defect sealing and oxygen plasma treatment, the resulting nanoporous membranes demonstrate record-high performances in dialysis and organic solvent nanofiltration, with a pure ethanol permeance of 156.8 liters m⁻² hour⁻¹ bar⁻¹ and 94.5% rejection to Rose Bengal (1011 g mol⁻¹) that surpasses the permeability-selectivity trade-off.

Molecular size-dependent subcontinuum solvent permeation and ultrafast nanofiltration across nanoporous graphene membranes

Selective solvent and solute transport across nanopores is fundamental to membrane separations, yet it remains poorly understood, especially for non-aqueous systems. Here, we design a chemically robust nanoporous graphene membrane and study molecular transport in various organic liquids under subnanometre confinement. We show that the nature of the solvent can modulate solute diffusion across graphene nanopores, and that breakdown of continuum flow occurs when pore size approaches the solvent's smallest molecular cross-section. By holistically engineering membrane support, modelling pore creation and defect management, high rejection and ultrafast organic solvent nanofiltration of dye molecules and separation of hexane isomers are achieved. The membranes exhibit stable fluxes across a range of solvents, consistent with flow across rigid pores whose size is independent of the solvent. These results demonstrate that nanoporous graphene is a rich materials system for controlling subcontinuum flow that could enable new membranes for a range of challenging separation needs.

Rapid screening of nanopore candidates in nanoporous single-layer graphene for selective separations using molecular visualization and interatomic potentials

Nanoporous single-layer graphene is promising as an ideal membrane because of its extreme thinness, chemical resistance, and mechanical strength, provided that selective nanopores are successfully incorporated. However, screening and understanding the transport characteristics of the large number of possible pores in graphene are limited by the high computational requirements of molecular dynamics (MD) simulations and the difficulty in experimentally characterizing pores of known structures. MD simulations cannot readily simulate the large number of pores that are encountered in actual membranes to predict transport, and given the huge variety of possible pores, it is hard to narrow down which pores to simulate. Here, we report alternative routes to rapidly screen molecules and nanopores with negligible computational requirement to shortlist selective nanopore candidates. Through the 3D representation and visualization of the pores' and molecules' atoms with their van der Waals radii using open-source software, we could identify suitable C-passivated nanopores for both gas- and liquid-phase separation while accounting for the pore and molecule shapes. The method was validated by simulations reported in the literature and was applied to study the mass transport behavior across a given distribution of nanopores. We also designed a second method that accounts for Lennard-Jones and electrostatic interactions between atoms to screen selective non-C-passivated nanopores for gas separations. Overall, these visualization methods can reduce the computational requirements for pore screening and speed up selective pore identification for subsequent detailed MD simulations and guide the experimental design and interpretation of transport measurements in nanoporous atomically thin membranes.

Iron oxide xerogels for improved water quality monitoring of arsenic(III) in resource-limited environments via solid-phase extraction, preservation, storage, transportation, and analysis of trace contaminants (SEPSTAT)

Arsenic is a widespread trace groundwater contaminant that presents a range of health risks and has an acceptable level of only 10 μg L-1 in drinking water. However, in many countries arsenic quantification in water is limited to centralized laboratories because it requires the use of elemental analysis techniques with high capital cost. As a result, routine water samples are frequently not tested for trace contaminants such as arsenic. In order to facilitate improved arsenic monitoring, we present the use of iron oxide xerogels for adsorption of arsenic(iii) from water samples at neutral pH, dry storage for over 120 days, and desorption of stored arsenic at elevated pH. Iron oxide xerogels offer high surface area (340 m2 g-1) and an As(iii) adsorption capacity of 165 mg g-1. Using an extraction solution of 100 mM sodium hydroxide and 1 mM sodium phosphate, As(iii) is reliably eluted from iron oxide xerogels for initial As(iii) concentrations from 10 μg L-1 to 1000 μg L-1, with a calculated detection limit of less than 4 μg L-1 and less than 17% difference in recovered As(iii) between test solutions with low and high interfering ion concentrations. By demonstrating the ability for iron oxide xerogels to reliably adsorb, store, and release arsenic, we enable the development of protocols for solid-phase extraction, preservation, storage, transportation, and analysis of trace contaminants (SEPSTAT), where arsenic would be adsorbed from water samples onto xerogel-based sorbents and shipped to centralized laboratories for recovery and quantification.

Engineering and characterization of gymnosperm sapwood toward enabling the design of water filtration devices

Naturally-occurring membranes in the xylem tissue of gymnosperm sapwood enable its use as an abundantly-available material to construct filters, with potential to facilitate access to safe drinking water in resource-constrained settings. However, the material’s behavior as a filter is poorly understood, and challenges such as short shelf life have not been addressed. Here, we characterize the operational attributes of xylem filters and show that the material exhibits a highly non-linear dependence of flow resistance on thickness upon drying, and a tendency for self-blocking. We develop guidelines for the design and fabrication of xylem filters, demonstrate gravity-operated filters with shelf life >2 years, and show that the filters can provide >3 log removal of E. coli, MS-2 phage, and rotavirus from synthetic test waters and coliform bacteria from contaminated spring, tap, and ground waters. Through interviews and workshops in India, we use a user-centric approach to design a prototype filtration device with daily- to weekly-replaceable xylem filters, and uncover indicators of social acceptance of xylem as a natural water filter. Our work enhances the understanding of xylem as a filtration material, and opens opportunities for engineering a diverse range of low-cost, biodegradable xylem-based filtration products on a global scale.

Gymnosperm sapwood is an abundantly available material to construct water filters but the material’s behaviour as a filter is poorly understood and challenges such as short shelf live have not been addressed. Here, the authors develop guidelines for the design and fabrication of xylem filters and demonstrate gravity-operated filters with a shelf life of more than two years for the removal of contaminants from spring, tap and ground water.

Impact of chronic sequential LV-RV pacing with cardiac resynchronization therapy for patients with narrower (&lt;130 ms) QRS complexes following evaluation of acute myocardial strain characteristics

Background

Prior studies have shown acute improvement in myocardial strain patterns (SP) and strain rates (SR), left ventricular ejection fraction (LVEF), and long-term clinical improvement by Cardiac Resynchronization Therapy (CRT) preferential LV pacing. This relationship has not been studied in patients (pts) with narrower QRS.

Objectives

We aimed to evaluate myocardial speckle tracking SP and SR at different VV intervals in pts with narrow (&lt;130 ms) and wide (&gt;130 ms) QRS.

Methods

We assessed LVEF and speckle tracking myocardial SP and SR as per the American Society of Echocardiography (ASE) Dyssynchrony Writing Group methods in pts with CRT in acute settings at VV0, VV60 and LV-only pacing. For SP assessment, we used Bull's eye format display of the LV segments, and scores for SR, 2 = early stretch, late peak, 1= early stretch, early peak, and 0 = single peak at aortic closure.

Results

Total cohort of 271 pts; age 69.2±10.3 yrs (mean ± SD), male - 60%, divided into 2 groups; Gp A (QRS &lt;130 ms, n=69) and Gp B (QRS &gt;130 ms, n=202). QRS width and LVEF in Gp A and B were 120.1±12.3 ms and 152.1±12.9 ms, and 22.3±9.4% and 23.3±10.2% respectively. With VV0 increase in LVEF, 67±6.0% from baseline 22.3±9.4% was seen in Gp A compared to 43±6.5% from 23.3±10.2% in Gp B (p&lt;0.01). With VV60 and LV-only pacing further rise in LVEF to 100.0±7.1% and 112.0±7.2% in Gp A and 80.2±8.0% and 93±8.1% in Gp B was seen. (Figure 1). Strain scores at different VV timings in both groups are shown in Table 1.

Conclusions

In pts with CRT, different VV timings show differences in acute myocardial speckle tracking SP and SR, and LVEF. These changes are markedly favorable with LV-only and sequential LV-RV pacing even in pts with narrower QRS. Our findings support chronic sequential LV-RV pacing programming in CRT pts with narrow QRS.

Figure 1

Funding Acknowledgement

Type of funding source: None

High permeability sub-nanometre sieve composite MoS2 membranes

Two-dimensional membranes have gained enormous interest due to their potential to deliver precision filtration of species with performance that can challenge current desalination membrane platforms. Molybdenum disulfide (MoS2) laminar membranes have recently demonstrated superior stability in aqueous environment to their extensively-studied analogs graphene-based membranes; however, challenges such as low ion rejection for high salinity water, low water flux, and low stability over time delay their potential adoption as a viable technology. Here, we report composite laminate multilayer MoS2 membranes with stacked heterodimensional one- to two-layer-thick porous nanosheets and nanodisks. These membranes have a multimodal porous network structure with tunable surface charge, pore size, and interlayer spacing. In forward osmosis, our membranes reject more than 99% of salts at high salinities and, in reverse osmosis, small-molecule organic dyes and salts are efficiently filtered. Finally, our membranes stably operate for over a month, implying their potential for use in commercial water purification applications.

Solid-Phase Extraction, Preservation, Storage, Transport, and Analysis of Trace Contaminants for Water Quality Monitoring of Heavy Metals

Accurate quantification of trace contaminants currently requires collection, preservation, and transportation of large volumes (250-1000 mL) of water to centralized laboratories, which impedes monitoring of trace-level pollutants in many resource-limited environments. To overcome this logistical challenge, we propose a new paradigm for trace contaminant monitoring based on dry preservation: solid-phase extraction, preservation, storage, transport, and analysis of trace contaminants (SEPSTAT). We show that a few grams of low-cost, commercially available cation exchange resin can be repurposed to extract heavy metal cations from water samples even in the presence of background ions, dryly preserve these cations for at least 24 months, and release them by acid elution for accurate quantification. A compact, human-powered device incorporating the sorbent removes spiked contaminants from real water samples in a few minutes. The device can be stored and transported easily and produces a sample suitable for measurement by standard methods, predicting the original sample heavy metal concentration generally within an error of 15%. These results suggest that, by facilitating the collection, storage, handling, and transportation of water samples and by enabling cost-effective use of high-throughput capital-intensive instruments, SEPSTAT has the potential to increase the ease and reach of water quality monitoring of trace contaminants.

Fieldwork-based determination of design priorities for point-of-use drinking water quality sensors for use in resource-limited environments

Improved capabilities in microfluidics, electrochemistry, and portable assays have resulted in the development of a wide range of point-of-use sensors intended for environmental, medical, and agricultural applications in resource-limited environments of developing countries. However, these devices are frequently developed without direct interaction with their often-remote intended user base, creating the potential for a disconnect between users' actual needs and those perceived by sensor developers. As different analytical techniques have inherent strengths and limitations, effective measurement solution development requires determination of desired sensor attributes early in the development process. In this work, we present our findings on design priorities for point-of-use microbial water sensors based on fieldwork in rural India, as well as a guide to fieldwork methodologies for determining desired sensor attributes. We utilized group design workshops for initial identification of design priorities, and then conducted choice-based conjoint analysis interviews for quantification of user preferences among these priorities. We found the highest user preference for integrated reporting of contaminant concentration and recommended actions, as well as significant preferences for mostly reusable sensor architectures, same-day results, and combined ingredients. These findings serve as a framework for future microbial sensor development and a guide for fieldwork-based understanding of user needs.

Drug loading augmentation in polymeric nanoparticles using a coaxial turbulent jet mixer: Yong investigator perspective

HYPOTHESIS

In conventional 'bulk' nanoprecipitation, the capacity to load hydrophobic drugs into the polymeric nanoparticles (NPs) is limited to about 1%. The size distribution of the resulting NPs becomes polydisperse when higher precursor concentration is used to increase the drug loading. Hence, it should be possible to enhance the hydrophobic drug loading in polymeric NPs while maintaining the uniform NP size distribution by optimizing the nanoprecipitation process and purification process.

EXPERIMENTS

Systematic studies were performed to enhance the loading of docetaxel (Dtxl) by using a process of centrifugal spin-down, rapid mixing by turbulence, and addition of co-solvent. The size distributions and Dtxl loading of the NPs were measured using dynamic light scattering and HPLC, respectively.

FINDINGS

The centrifugal spin-down process helps to maintain uniform size distribution even at the high precursor concentration. In bulk nanoprecipitation, the resulting NPs achieved Dtxl loading up to 3.2%. By adopting turbulence for rapid mixing, the loading of Dtxl increased to 4.4%. By adding hexane as co-solvent, the loading of Dtxl further increased to 5.5%. Because of the drug loading augmentation, high degree of control, and extremely high production rate, the developed method may be useful for industrial-scale production of personalized nanomedicines by nanoprecipitation.

Facile Fabrication of Large-Area Atomically Thin Membranes by Direct Synthesis of Graphene with Nanoscale Porosity

Direct synthesis of graphene with well-defined nanoscale pores over large areas can transform the fabrication of nanoporous atomically thin membranes (NATMs) and greatly enhance their potential for practical applications. However, scalable bottom-up synthesis of continuous sheets of nanoporous graphene that maintain integrity over large areas has not been demonstrated. Here, it is shown that a simple reduction in temperature during chemical vapor deposition (CVD) on Cu induces in-situ formation of nanoscale defects (≤2-3 nm) in the graphene lattice, enabling direct and scalable synthesis of nanoporous monolayer graphene. By solution-casting of hierarchically porous polyether sulfone supports on the as-grown nanoporous CVD graphene, large-area (>5 cm² ) NATMs for dialysis applications are demonstrated. The synthesized NATMs show size-selective diffusive transport and effective separation of small molecules and salts from a model protein, with ≈2-100× increase in permeance along with selectivity better than or comparable to state-of-the-art commercially available polymeric dialysis membranes. The membranes constitute the largest fully functional NATMs fabricated via bottom-up nanopore formation, and can be easily scaled up to larger sizes permitted by CVD synthesis. The results highlight synergistic benefits in blending traditional membrane casting with bottom-up pore creation during graphene CVD for advancing NATMs toward practical applications.

Antibody-modified conduits for highly selective cytokine elimination from blood

Cytokines play an important role in dysregulated immune responses to infection, pancreatitis, ischemia/reperfusion injury, burns, hemorrhage, cardiopulmonary bypass, trauma, and many other diseases. Moreover, the imbalance between inflammatory and antiinflammatory cytokines can have deleterious effects. Here, we demonstrated highly selective blood-filtering devices - antibody-modified conduits (AMCs) - that selectively eliminate multiple specific deleterious cytokines in vitro. AMCs functionalized with antibodies against human vascular endothelial growth factor A or tumor necrosis factor α (TNF-α) selectively eliminated the target cytokines from human blood in vitro and maintained them in reduced states even in the face of ongoing infusion at supraphysiologic rates. We characterized the variables that determine AMC performance, using anti-human TNF-α AMCs to eliminate recombinant human TNF-α. Finally, we demonstrated selective cytokine elimination in vivo by filtering interleukin 1 β from rats with lipopolysaccharide-induced hypercytokinemia.

A Scalable Route to Nanoporous Large-Area Atomically Thin Graphene Membranes by Roll-to-Roll Chemical Vapor Deposition and Polymer Support Casting

Scalable, cost-effective synthesis and integration of graphene is imperative to realize large-area applications such as nanoporous atomically thin membranes (NATMs). Here, we report a scalable route to the production of NATMs via high-speed, continuous synthesis of large-area graphene by roll-to-roll chemical vapor deposition (CVD), combined with casting of a hierarchically porous polymer support. To begin, we designed and built a two zone roll-to-roll graphene CVD reactor, which sequentially exposes the moving foil substrate to annealing and growth atmospheres, with a sharp, isothermal transition between the zones. The configurational flexibility of the reactor design allows for a detailed evaluation of key parameters affecting graphene quality and trade-offs to be considered for high-rate roll-to-roll graphene manufacturing. With this system, we achieve synthesis of uniform high-quality monolayer graphene ( I_D/ I_G < 0.065) at speeds ≥5 cm/min. NATMs fabricated from the optimized graphene, via polymer casting and postprocessing, show size-selective molecular transport with performance comparable to that of membranes made from conventionally synthesized graphene. Therefore, this work establishes the feasibility of a scalable manufacturing process of NATMs, for applications including protein desalting and small-molecule separations.

Enhanced water transport and salt rejection through hydrophobic zeolite pores

The potential of improvements to reverse osmosis (RO) desalination by incorporating porous nanostructured materials such as zeolites into the selective layer in the membrane has spurred substantial research efforts over the past decade. However, because of the lack of methods to probe transport across these materials, it is still unclear which pore size or internal surface chemistry is optimal for maximizing permeability and salt rejection. We developed a platform to measure the transport of water and salt across a single layer of zeolite crystals, elucidating the effects of internal wettability on water and salt transport through the ≈5.5 Å pores of MFI zeolites. MFI zeolites with a more hydrophobic (i.e., less attractive) internal surface chemistry facilitated an approximately order of magnitude increase in water permeability compared to more hydrophilic MFI zeolites, while simultaneously fully rejecting both potassium and chlorine ions. However, our results also demonstrated approximately two orders of magnitude lower permeability compared to molecular simulations. This decreased performance suggests that additional transport resistances (such as surface barriers, pore collapse or blockages due to contamination) may be limiting the performance of experimental nanostructured membranes. Nevertheless, the inclusion of hydrophobic sub-nanometer pores into the active layer of RO membranes should improve both the water permeability and salt rejection of future RO membranes (Fasano et al 2016 Nat. Commun. 7 12762).

Microfluidic multiplexing of solid-state nanopores

Although solid-state nanopores enable electronic analysis of many clinically and biologically relevant molecular structures, there are few existing device architectures that enable high-throughput measurement of solid-state nanopores. Herein, we report a method for microfluidic integration of multiple solid-state nanopores at a high density of one nanopore per (35 µm²). By configuring microfluidic devices with microfluidic valves, the nanopores can be rinsed from a single fluid input while retaining compatibility for multichannel electrical measurements. The microfluidic valves serve the dual purpose of fluidic switching and electric switching, enabling serial multiplexing of the eight nanopores with a single pair of electrodes. Furthermore, the device architecture exhibits low noise and is compatible with electroporation-based in situ nanopore fabrication, providing a scalable platform for automated electronic measurement of a large number of integrated solid-state nanopores.

Water and Solute Transport Governed by Tunable Pore Size Distributions in Nanoporous Graphene Membranes

Nanoporous graphene has the potential to advance membrane separations by offering high selectivity with minimal resistance to flow, but how mass transport depends on the structure of pores in this atomically thin membrane is poorly understood. Here, we investigate the relationship between tunable pore creation using ion bombardment and oxygen plasma etching, the resulting pore size distributions, and the consequent water and solute transport. Through tuning of the pore creation process, we demonstrate nanofiltration membranes that reject small molecules but offer high permeance to water or monovalent ions. Theoretical multiscale modeling of transport across the membranes reveals a disproportionate contribution of large pores to osmotic water flux and diffusive solute transport and captures the observed trends in transport measurements except for the smallest pores. This work provides insights into the effects of graphene pore size distribution and support layer on transport and presents a framework for designing atomically thin membranes.

Nanoporous Atomically Thin Graphene Membranes for Desalting and Dialysis Applications

Dialysis is a ubiquitous separation process in biochemical processing and biological research. State-of-the-art dialysis membranes comprise a relatively thick polymer layer with tortuous pores, and suffer from low rates of diffusion leading to extremely long process times (often several days) and poor selectivity, especially in the 0-1000 Da molecular weight cut-off range. Here, the fabrication of large-area (cm² ) nanoporous atomically thin membranes (NATMs) is reported, by transferring graphene synthesized using scalable chemical vapor deposition (CVD) to polycarbonate track-etched supports. After sealing defects introduced during transfer/handling by interfacial polymerization, a facile oxygen-plasma etch is used to create size-selective pores (≤1 nm) in the CVD graphene. Size-selective separation and desalting of small model molecules (≈200-1355 Da) and proteins (≈14 000 Da) are demonstrated, with ≈1-2 orders of magnitude increase in permeance compared to state-of-the-art commercial membranes. Rapid diffusion and size-selectivity in NATMs offers transformative opportunities in purification of drugs, removal of residual reactants, biochemical analytics, medical diagnostics, therapeutics, and nano-bio separations.

Molecular Sieving Across Centimeter-Scale Single-Layer Nanoporous Graphene Membranes

Molecular sieving across atomically thin nanoporous graphene is predicted to enable superior gas separation performance compared to conventional membranes. Although molecular sieving has been demonstrated across a few pores in microscale graphene membranes, leakage through nonselective defects presents a major challenge toward realizing selective membranes with high densities of pores over macroscopic areas. Guided by multiscale gas transport modeling of nanoporous graphene membranes, we designed the porous support beneath the graphene to isolate small defects and minimize leakage through larger defects. Ion bombardment followed by oxygen plasma etching was used to produce subnanometer pores in graphene at a density of ∼10¹¹ cm^-2. Gas permeance measurements demonstrate selectivity that exceeds the Knudsen effusion ratio and scales with the kinetic diameter of the gas molecules, providing evidence of molecular sieving across centimeter-scale nanoporous graphene. The extracted nanoporous graphene performance is comparable to or exceeds the Robeson limit for polymeric gas separation membranes, confirming the potential of nanoporous graphene membranes for gas separations.

Assessment and control of the impermeability of graphene for atomically thin membranes and barriers

Two-dimensional materials such as graphene offer fundamentally transformative opportunities in membrane separations and as impermeable barriers, but the lack of facile methods to assess and control its 'impermeability' critically limits progress. Here we show that a simple etch of the growth catalyst (Cu) through defects in monolayer graphene synthesized by chemical vapor deposition (CVD) can be used to effectively assess graphene quality for membrane/barrier applications. Using feedback from the method to tune synthesis, we realize graphene with nearly no nanometer-scale defects as assessed by diffusion measurements, in contrast to commercially available graphene that is largely optimized for electronic applications. Interestingly, we observe clear evidence of leakage through larger defects associated with wrinkles in graphene, which are selectively sealed to realize centimeter-scale atomically thin barriers exhibiting <2% mass transport compared to the graphene support. Our work provides a facile method to assess and control the 'impermeability' of graphene and shows that future work should be directed towards the control of leakage associated with wrinkles.

Fundamental transport mechanisms, fabrication and potential applications of nanoporous atomically thin membranes

Graphene and other two-dimensional materials offer a new approach to controlling mass transport at the nanoscale. These materials can sustain nanoscale pores in their rigid lattices and due to their minimum possible material thickness, high mechanical strength and chemical robustness, they could be used to address persistent challenges in membrane separations. Here we discuss theoretical and experimental developments in the emerging field of nanoporous atomically thin membranes, focusing on the fundamental mechanisms of gas- and liquid-phase transport, membrane fabrication techniques and advances towards practical application. We highlight potential functional characteristics of the membranes and discuss applications where they are expected to offer advantages. Finally, we outline the major scientific questions and technological challenges that need to be addressed to bridge the gap from theoretical simulations and proof-of-concept experiments to real-world applications.

Single-Layer Graphene Membranes Withstand Ultrahigh Applied Pressure

High mechanical strength is essential for pressure-driven membrane separations with nanoporous single-layer graphene, but its ability to withstand high pressures remains to be demonstrated. We monitored failure of centimeter-scale single-layer graphene membranes on porous supports subjected to high pressures. Consistent with theory, the membranes were found to withstand higher pressures when placed on porous supports with smaller pore diameters, but failure occurred over a surprisingly broad range of pressures, attributed to heterogeneous susceptibility to failure at wrinkles, defects, and slack in the suspended graphene. Remarkably, nonwrinkled areas withstood pressure exceeding 100 bar at which many kinds of membrane suffer from compaction. Our study shows that single-layer graphene membranes can sustain ultrahigh pressure especially if the effect of wrinkles is isolated using supports with small pores and suggests the potential for the use of single-layer graphene in high-pressure membrane separations.

Knudsen effusion through polymer-coated three-layer porous graphene membranes

Graphene membranes have the potential to exceed the permeance and selectivity limits of conventional gas separation membranes. Realizing this potential in practical systems relies on overcoming numerous scalability challenges, such as isolating or sealing permeable defects in macroscopic areas of graphene that can compromise performance and developing methods to create high densities of selective pores over large areas. This study focuses on a centimeter-scale membrane design, where leakage is reduced by substrate selection, permeable polymer film coating, and stacking of three independent layers of graphene, while (selective) pores are created by high density ion bombardment. The three-layer graphene provides high resistance to gas flow, which decreases with ion bombardment and results in selectivity consistent with Knudsen effusion. The results suggest that the permeable pores created in three layer graphene were larger than those required for molecular sieving and that designs based on single layer graphene may lend themselves more easily to molecular sieving of gases.

Harnessing the hygroscopic and biofluorescent behaviors of genetically tractable microbial cells to design biohybrid wearables

Cells' biomechanical responses to external stimuli have been intensively studied but rarely implemented into devices that interact with the human body. We demonstrate that the hygroscopic and biofluorescent behaviors of living cells can be engineered to design biohybrid wearables, which give multifunctional responsiveness to human sweat. By depositing genetically tractable microbes on a humidity-inert material to form a heterogeneous multilayered structure, we obtained biohybrid films that can reversibly change shape and biofluorescence intensity within a few seconds in response to environmental humidity gradients. Experimental characterization and mechanical modeling of the film were performed to guide the design of a wearable running suit and a fluorescent shoe prototype with bio-flaps that dynamically modulates ventilation in synergy with the body's need for cooling.

Selective Nanoscale Mass Transport across Atomically Thin Single Crystalline Graphene Membranes

Atomically thin single crystals, without grain boundaries and associated defect clusters, represent ideal systems to study and understand intrinsic defects in materials, but probing them collectively over large area remains nontrivial. In this study, the authors probe nanoscale mass transport across large-area (≈0.2 cm² ) single-crystalline graphene membranes. A novel, polymer-free picture frame assisted technique, coupled with a stress-inducing nickel layer is used to transfer single crystalline graphene grown on silicon carbide substrates to flexible polycarbonate track etched supports with well-defined cylindrical ≈200 nm pores. Diffusion-driven flow shows selective transport of ≈0.66 nm hydrated K⁺ and Cl^- ions over ≈1 nm sized small molecules, indicating the presence of selective sub-nanometer to nanometer sized defects. This work presents a framework to test the barrier properties and intrinsic quality of atomically thin materials at the sub-nanometer to nanometer scale over technologically relevant large areas, and suggests the potential use of intrinsic defects in atomically thin materials for molecular separations or desalting.

Design of Insulin-Loaded Nanoparticles Enabled by Multistep Control of Nanoprecipitation and Zinc Chelation

Nanoparticle (NP) carriers provide new opportunities for controlled delivery of drugs, and have potential to address challenges such as effective oral delivery of insulin. However, due to the difficulty of efficiently loading insulin and other proteins inside polymeric NPs, their use has been mostly restricted to the encapsulation of small molecules. To better understand the processes involved in encapsulation of proteins in NPs, we study how buffer conditions, ionic chelation, and preparation methods influence insulin loading in poly(lactic-co-glycolic acid)-b-poly(ethylene glycol) (PLGA-PEG) NPs. We report that, although insulin is weakly bound and easily released from the NPs in the presence of buffer ions, insulin loading can be increased by over 10-fold with the use of chelating zinc ions and by the optimization of the pH during nanoprecipitation. We further provide ways of changing synthesis parameters to control NP size while maintaining high insulin loading. These results provide a simple method to enhance insulin loading of PLGA-PEG NPs and provide insights that may extend to other protein drug delivery systems that are subject to limited loading.

Isolation of Circulating Plasma Cells in Multiple Myeloma Using CD138 Antibody-Based Capture in a Microfluidic Device

The necessity for bone marrow aspiration and the lack of highly sensitive assays to detect residual disease present challenges for effective management of multiple myeloma (MM), a plasma cell cancer. We show that a microfluidic cell capture based on CD138 antigen, which is highly expressed on plasma cells, permits quantitation of rare circulating plasma cells (CPCs) in blood and subsequent fluorescence-based assays. The microfluidic device is based on a herringbone channel design, and exhibits an estimated cell capture efficiency of ~40–70%, permitting detection of <10 CPCs/mL using 1-mL sample volumes, which is difficult using existing techniques. In bone marrow samples, the microfluidic-based plasma cell counts exhibited excellent correlation with flow cytometry analysis. In peripheral blood samples, the device detected a baseline of 2–5 CD138⁺ cells/mL in healthy donor blood, with significantly higher numbers in blood samples of MM patients in remission (20–24 CD138⁺ cells/mL), and yet higher numbers in MM patients exhibiting disease (45–184 CD138⁺ cells/mL). Analysis of CPCs isolated using the device was consistent with serum immunoglobulin assays that are commonly used in MM diagnostics. These results indicate the potential of CD138-based microfluidic CPC capture as a useful ‘liquid biopsy’ that may complement or partially replace bone marrow aspiration.

Accidental separation and lodgment of rotary endodontic file into the dentist's thumb

Separation of the endodontic instrument within the root canal system and sharp injuries to the dentist is not an uncommon event in endodontic practice. Although root canal instruments can fracture at any stage of endodontic treatment, its fracture within the dentist's hand is a very rare event. An unusual case of accidental separation and lodgment of rotary endodontic file in the dentist's thumb is presented along with its management. A 33-year-old dentist reported with an accidental lodgment of rotary endodontic file into his thumb. The fractured instrument was removed successfully by a surgeon. The present case describes a rare event of occupational risk in endodontic practice.

Polymeric Nanoparticles Amenable to Simultaneous Installation of Exterior Targeting and Interior Therapeutic Proteins

Effective delivery of therapeutic proteins is a formidable challenge. Herein, using a unique polymer family with a wide-ranging set of cationic and hydrophobic features, we developed a novel nanoparticle (NP) platform capable of installing protein ligands on the particle surface and simultaneously carrying therapeutic proteins inside by a self-assembly procedure. The loaded therapeutic proteins (e.g., insulin) within the NPs exhibited sustained and tunable release, while the surface-coated protein ligands (e.g., transferrin) were demonstrated to alter the NP cellular behaviors. In vivo results revealed that the transferrin-coated NPs can effectively be transported across the intestinal epithelium for oral insulin delivery, leading to a notable hypoglycemic response.

Heterogeneous sub-continuum ionic transport in statistically isolated graphene nanopores

Graphene and other two-dimensional materials offer a new class of ultrathin membranes that can have atomically defined nanopores with diameters approaching those of hydrated ions. These nanopores have the smallest possible pore volumes of any ion channel, which, due to ionic dehydration and electrokinetic effects, places them in a novel transport regime and allows membranes to be created that combine selective ionic transport with ultimate permeance and could lead to separations and sensing applications. However, experimental characterization and understanding of sub-continuum ionic transport in nanopores below 2 nm is limited. Here we show that isolated sub-2 nm pores in graphene exhibit, in contrast to larger pores, diverse transport behaviours consistent with ion transport over a free-energy barrier arising from ion dehydration and electrostatic interactions. Current-voltage measurements reveal that the conductance of graphene nanopores spans three orders of magnitude and that they display distinct linear, voltage-activated or rectified current-voltage characteristics and different cation-selectivity profiles. In rare cases, rapid, voltage-dependent stochastic switching is observed, consistent with the presence of a dissociable group in the pore vicinity. A modified Nernst-Planck model incorporating ion hydration and electrostatic effects quantitatively matches the observed behaviours.

Nanofiltration across Defect-Sealed Nanoporous Monolayer Graphene

Monolayer nanoporous graphene represents an ideal membrane for molecular separations, but its practical realization is impeded by leakage through defects in the ultrathin graphene. Here, we report a multiscale leakage-sealing process that exploits the nonpolar nature and impermeability of pristine graphene to selectively block defects, resulting in a centimeter-scale membrane that can separate two fluid reservoirs by an atomically thin layer of graphene. After introducing subnanometer pores in graphene, the membrane exhibited rejection of multivalent ions and small molecules and water flux consistent with prior molecular dynamics simulations. The results indicate the feasibility of constructing defect-tolerant monolayer graphene membranes for nanofiltration, desalination, and other separation processes.

Transepithelial transport of Fc-targeted nanoparticles by the neonatal fc receptor for oral delivery

Nanoparticles are poised to have a tremendous impact on the treatment of many diseases, but their broad application is limited because currently they can only be administered by parenteral methods. Oral administration of nanoparticles is preferred but remains a challenge because transport across the intestinal epithelium is limited. We show that nanoparticles targeted to the neonatal Fc receptor (FcRn), which mediates the transport of immunoglobulin G antibodies across epithelial barriers, are efficiently transported across the intestinal epithelium using both in vitro and in vivo models. In mice, orally administered FcRn-targeted nanoparticles crossed the intestinal epithelium and reached systemic circulation with a mean absorption efficiency of 13.7%*hour compared with only 1.2%*hour for nontargeted nanoparticles. In addition, targeted nanoparticles containing insulin as a model nanoparticle-based therapy for diabetes were orally administered at a clinically relevant insulin dose of 1.1 U/kg and elicited a prolonged hypoglycemic response in wild-type mice. This effect was abolished in FcRn knockout mice, indicating that the enhanced nanoparticle transport was specifically due to FcRn. FcRn-targeted nanoparticles may have a major impact on the treatment of many diseases by enabling drugs currently limited by low bioavailability to be efficiently delivered though oral administration.

Ultra-high throughput synthesis of nanoparticles with homogeneous size distribution using a coaxial turbulent jet mixer

High-throughput production of nanoparticles (NPs) with controlled quality is critical for their clinical translation into effective nanomedicines for diagnostics and therapeutics. Here we report a simple and versatile coaxial turbulent jet mixer that can synthesize a variety of NPs at high throughput up to 3 kg/d, while maintaining the advantages of homogeneity, reproducibility, and tunability that are normally accessible only in specialized microscale mixing devices. The device fabrication does not require specialized machining and is easy to operate. As one example, we show reproducible, high-throughput formulation of siRNA-polyelectrolyte polyplex NPs that exhibit effective gene knockdown but exhibit significant dependence on batch size when formulated using conventional methods. The coaxial turbulent jet mixer can accelerate the development of nanomedicines by providing a robust and versatile platform for preparation of NPs at throughputs suitable for in vivo studies, clinical trials, and industrial-scale production.

Carbon nanotube membranes with ultrahigh specific adsorption capacity for water desalination and purification

Development of technologies for water desalination and purification is critical to meet the global challenges of insufficient water supply and inadequate sanitation, especially for point-of-use applications. Conventional desalination methods are energy and operationally intensive, whereas adsorption-based techniques are simple and easy to use for point-of-use water purification, yet their capacity to remove salts is limited. Here we report that plasma-modified ultralong carbon nanotubes exhibit ultrahigh specific adsorption capacity for salt (exceeding 400% by weight) that is two orders of magnitude higher than that found in the current state-of-the-art activated carbon-based water treatment systems. We exploit this adsorption capacity in ultralong carbon nanotube-based membranes that can remove salt, as well as organic and metal contaminants. These ultralong carbon nanotube-based membranes may lead to next-generation rechargeable, point-of-use potable water purification appliances with superior desalination, disinfection and filtration properties.

Nanofluidic transport governed by the liquid/vapour interface

Liquid/vapour interfaces govern the behaviour of a wide range of systems but remain poorly understood, leaving ample margin for the exploitation of intriguing functionalities for applications. Here, we systematically investigate the role of liquid/vapour interfaces in the transport of water across apposing liquid menisci in osmosis membranes comprising short hydrophobic nanopores that separate two fluid reservoirs. We show experimentally that mass transport is limited by molecular reflection from the liquid/vapour interface below a certain length scale, which depends on the transmission probability of water molecules across the nanopores and on the condensation probability of a water molecule incident on the liquid surface. This fundamental yet elusive condensation property of water is measured under near-equilibrium conditions and found to decrease from 0.36 ± 0.21 at 30 °C to 0.18 ± 0.09 at 60 °C. These findings define the regime in which liquid/vapour interfaces govern nanofluidic transport and have implications for understanding mass transport in nanofluidic devices, droplets and bubbles, biological components and porous media involving liquid/vapour interfaces.

Selective ionic transport through tunable subnanometer pores in single-layer graphene membranes

We report selective ionic transport through controlled, high-density, subnanometer diameter pores in macroscopic single-layer graphene membranes. Isolated, reactive defects were first introduced into the graphene lattice through ion bombardment and subsequently enlarged by oxidative etching into permeable pores with diameters of 0.40 ± 0.24 nm and densities exceeding 10(12) cm(-2), while retaining structural integrity of the graphene. Transport measurements across ion-irradiated graphene membranes subjected to in situ etching revealed that the created pores were cation-selective at short oxidation times, consistent with electrostatic repulsion from negatively charged functional groups terminating the pore edges. At longer oxidation times, the pores allowed transport of salt but prevented the transport of a larger organic molecule, indicative of steric size exclusion. The ability to tune the selectivity of graphene through controlled generation of subnanometer pores addresses a significant challenge in the development of advanced nanoporous graphene membranes for nanofiltration, desalination, gas separation, and other applications.

Parallel microfluidic synthesis of size-tunable polymeric nanoparticles using 3D flow focusing towards in vivo study

Microfluidic synthesis of nanoparticles (NPs) can enhance the controllability and reproducibility in physicochemical properties of NPs compared to bulk synthesis methods. However, applications of microfluidic synthesis are typically limited to in vitro studies due to low production rates. Herein, we report the parallelization of NP synthesis by 3D hydrodynamic flow focusing (HFF) using a multilayer microfluidic system to enhance the production rate without losing the advantages of reproducibility, controllability, and robustness. Using parallel 3D HFF, polymeric poly(lactide-co-glycolide)-b-polyethyleneglycol (PLGA-PEG) NPs with sizes tunable in the range of 13-150 nm could be synthesized reproducibly with high production rate. As a proof of concept, we used this system to perform in vivo pharmacokinetic and biodistribution study of small (20 nm diameter) PLGA-PEG NPs that are otherwise difficult to synthesize. Microfluidic parallelization thus enables synthesis of NPs with tunable properties with production rates suitable for both in vitro and in vivo studies.

FROM THE CLINICAL EDITOR

Applications of nanoparticle synthesis with microfluidic methods are typically limited to in vitro studies due to low production rates. The team of authors of this proof-of-principle study reports on the successful parallelization of NP synthesis by 3D hydrodynamic flow focusing using a multilayer microfluidic system to enhance production rate without losing the advantages of reproducibility, controllability, and robustness.

Implications of permeation through intrinsic defects in graphene on the design of defect-tolerant membranes for gas separation

Gas transport through intrinsic defects and tears is a critical yet poorly understood phenomenon in graphene membranes for gas separation. We report that independent stacking of graphene layers on a porous support exponentially decreases flow through defects. On the basis of experimental results, we develop a gas transport model that elucidates the separate contributions of tears and intrinsic defects on gas leakage through these membranes. The model shows that the pore size of the porous support and its permeance critically affect the separation behavior, and reveals the parameter space where gas separation can be achieved regardless of the presence of nonselective defects, even for single-layer membranes. The results provide a framework for understanding gas transport in graphene membranes and guide the design of practical, selectively permeable graphene membranes for gas separation.

Mechanisms of molecular permeation through nanoporous graphene membranes

We present an investigation of molecular permeation of gases through nanoporous graphene membranes via molecular dynamics simulations; four different gases are investigated, namely helium, hydrogen, nitrogen, and methane. We show that in addition to the direct (gas-kinetic) flux of molecules crossing from the bulk phase on one side of the graphene to the bulk phase on the other side, for gases that adsorb onto the graphene, significant contribution to the flux across the membrane comes from a surface mechanism by which molecules cross after being adsorbed onto the graphene surface. Our results quantify the relative contribution of the bulk and surface mechanisms and show that the direct flux can be described reasonably accurately using kinetic theory, provided the latter is appropriately modified assuming steric molecule-pore interactions, with gas molecules behaving as hard spheres of known kinetic diameters. The surface flux is negligible for gases that do not adsorb onto graphene (e.g., He and H2), while for gases that adsorb (e.g., CH4 and N2) it can be on the order of the direct flux or larger. Our results identify a nanopore geometry that is permeable to hydrogen and helium, is significantly less permeable to nitrogen, and is essentially impermeable to methane, thus validating previous suggestions that nanoporous graphene membranes can be used for gas separation. We also show that molecular permeation is strongly affected by pore functionalization; this observation may be sufficient to explain the large discrepancy between simulated and experimentally measured transport rates through nanoporous graphene membranes.

A cell rolling cytometer reveals the correlation between mesenchymal stem cell dynamic adhesion and differentiation state

This communication presents quantitative studies of the dynamic adhesion behavior of mesenchymal stem cells (MSCs) enabled by the combination of cell-surface receptor-ligand interactions and three-dimensional hydrodynamic control by microtopography.