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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Effects of Intercalating Molecules on the Polymer Properties of DNA

Atomic force microscopy (AFM) enables determination of physical properties from single DNA molecules. Insertion of aromatic molecules into the structure of DNA results in morphological changes. However, the accompanying changes to elastic properties due to this insertion are not fully understood. AFM was used to examine the morphological effects of intercalator binding and report changes in the elastic properties of intrinsically straight DNA molecules. The persistence length and polymer extension were characterized in the presence of three intercalating molecules: ethidium bromide and the less well studied chloroquine and acridine. It was found that all three intercalators significantly increased the bending persistence length. In addition, an analysis of the normal bending modes of the static molecules corroborated these results. Furthermore, this approach of measuring binding effects of intercalators on DNA physical properties using a model system of intrinsically straight DNA is applicable to other DNA binding ligands and other modes of DNA interaction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Cultured human amniocytes express hTERT, which is distributed between nucleus and cytoplasm and is secreted in extracellular vesicles

Background: An increasing number of studies on stem cells suggests that the therapeutic effect they exert is primarily mediated by a paracrine regulation through extracellular vesicles (EVs) giving solid grounds for stem cell EVs to be exploited as agents for treating diseases or for restoring damaged tissues and organs. Due to their capacity to differentiate in all embryonic germ layers, amniotic fluid stem cells (AFCs), represent a highly promising cell type for tissue regeneration, which however is still poorly studied and in turn underutilized. In view of this, we conducted a first investigation on the expression of human hTERT gene − known to be among the key triggers of organ regeneration − in AFCs and in the EVs they secrete. Methods: Isolated AFCs were evaluated by RT-qPCR for hTERT expression. The clones expressing the highest levels of transcript, were analyzed by Immunofluorescence imaging and Nuclear/cytoplasmic fractionation in order to evaluate hTERT subcellular localization. We then separated EVs from FBS depleted culture medium by serial (ultra) centrifugations steps and characterized them using Western blotting, Atomic force Microscopy and Nanoplasmonic assay. Results: We first demonstrated that primary cultures of AFCs express the gene hTERT at different levels. Then we evidenced that in AFCs with the higher transcript levels, the hTERT protein is present in the nuclear and cytoplasmic compartment. Finally, we found that cytosolic hTERT is embodied in the EVs that AFCs secrete in the extracellular milieu. Conclusions: Our study demonstrates for the first time the expression of the full protein hTERT by AFCs and its release outside the cell mediated by EVs, indicating a new extra telomeric role for this protein. This finding represents an initial but crucial evidence for considering AFCs derived EVs as new potential sources for tissue regeneration. - Highlights: • Primary cultures of AFCs express the gene hTERT at different levels. • hTERT protein is present in the nuclear and cytoplasmic compartment of AFCs. • Cytosolic hTERT is embodied in AFCs secreted extracellular vesicles. • Those findings indicate a new potential extra telomeric role for hTERT. • AFCs derived EVs might represent a useful tool for regenerative medicine.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Calibration of higher eigenmodes of cantilevers

A method is presented for calibrating the higher eigenmodes (resonant modes) of atomic force microscopy cantilevers that can be performed prior to any tip-sample interaction. The method leverages recent efforts in accurately calibrating the first eigenmode by providing the higher-mode stiffness as a ratio to the first mode stiffness. A one-time calibration routine must be performed for every cantilever type to determine a power-law relationship between stiffness and frequency, which is then stored for future use on similar cantilevers. Then, future calibrations only require a measurement of the ratio of resonant frequencies and the stiffness of the first mode. This method is verified through stiffness measurements using three independent approaches: interferometric measurement, AC approach-curve calibration, and finite element analysis simulation. Power-law values for calibrating higher-mode stiffnesses are reported for several cantilever models. Once the higher-mode stiffnesses are known, the amplitude of each mode can also be calibrated from the thermal spectrum by application of the equipartition theorem.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Adsorption, desorption, and film formation of quinacridone and its thermal cracking product indigo on clean and carbon-covered silicon dioxide surfaces

The evaporation of quinacridone from a stainless steel Knudsen cell leads to the partial decomposition of this molecule in the cell, due to its comparably high sublimation temperature. At least one additional type of molecules, namely indigo, could be detected in the effusion flux. Thermal desorption spectroscopy and atomic force microscopy have been used to study the co-deposition of these molecules on sputter-cleaned and carbon-covered silicon dioxide surfaces. Desorption of indigo appears at temperatures of about 400 K, while quinacridone desorbs at around 510 K. For quinacridone, a desorption energy of 2.1 eV and a frequency factor for desorption of 1 × 10{sup 19} s{sup −1} were calculated, which in this magnitude is typical for large organic molecules. A fraction of the adsorbed quinacridone molecules (∼5%) decomposes during heating, nearly independent of the adsorbed amount, resulting in a surface composed of small carbon islands. The sticking coefficients of indigo and quinacridone were found to be close to unity on a carbon covered SiO{sub 2} surface but significantly smaller on a sputter-cleaned substrate. The reason for the latter can be attributed to insufficient energy dissipation for unfavorably oriented impinging molecules. However, due to adsorption via a hot-precursor state, the sticking probability is increased on the surface covered with carbon islands, which act as accommodation centers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Biophysical characteristics of hematopoietic cells during division

Cell division is managed by a complex and coordinated sequence of cytoskeleton alterations that give rise to major morphological changes. During dividing the cleavage furrow of the cell is significantly stiffened due to the accumulation of actomyosin. However, it is unclear whether the stiffness on top of the cell is changed or not. Here, we used atomic force microscopy to measure stiffness on this location of non-adhesion Jurkat T cell and its derivative D1.1 cell from interphase to cytokinesis. The results showed that during division the cell stiffness significantly increases at anaphase and telophase. These increases in cell stiffness are most likely due to the cell surface tension created by the pulling forces of the microtubules to separate sister chromatids in the anaphase and the contraction forces of the contractile ring to separate the mother cell into daughters in the telophase. The dynamic measurement of cell elasticity during cell division may be used as a tool to gain further insight into the involved molecules and mechanisms.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Nanomechanical sampling of material for nanoscale mass spectrometry chemical analysis

The ability to spatially resolve the chemical distribution of compounds on a surface is important in many applications ranging from biological to material science. To this extent, we have recently introduced a hybrid atomic force microscopy (AFM)-mass spectrometry (MS) system for direct thermal desorption and pyrolysis of material with nanoscale chemical resolution. However, spatially resolved direct surface heating using local thermal desorption becomes challenging on material surfaces with low melting points, because the material will undergo a melting phase transition due to heat dissipation prior to onset of thermal desorption. Therefore, here we developed an approach using mechanical sampling and collection of surface materials on an AFM cantilever probe tip for real-time analysis directly from the AFM tip. This approach allows for material to be concentrated directly onto the probe for subsequent MS analysis. We evaluate the performance metrics of the technique and demonstrate localized MS sampling from a candelilla wax matrix containing UV stabilizers avobenzone and oxinoxate from areas down to 250 nm × 250 nm. Overall, this approach removes heat dissipation into the bulk material allowing for a faster desorption and concentration of the gas phase analyte from a single heating pulse enabling higher signal levels from a given amount of material in a single sampling spot.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Direct nanoscale mapping of open circuit voltages at local back surface fields for PERC solar cells

The open circuit voltage (V OC) is a critical and common indicator of solar cell performance as well as degradation, for panel down to lab-scale photovoltaics. Detecting V OC at the nanoscale is much more challenging, however, due to experimental limitations on spatial resolution, voltage resolution, and/or measurement times. Accordingly, in this work an approach based on Conductive Atomic Force Microscopy is implemented to directly detect the local V OC , notably for monocrystalline Passivated Emitter Rear Contact (PERC) cells which are the most common industrial-scale solar panel technology in production worldwide. This is demonstrated with cross-sectioned monocrystalline PERC cells around the entire circumference of a poly-Aluminum-Silicide via through the rear emitter. The V OC maps reveal a local Back Surface Field extending ~2 μm into the underlying p-type Si absorber due to Al in-diffusion as designed. Such high spatial resolution methods for photovoltaic performance mapping are especially promising for directly visualizing the effects of processing parameters, as well as identifying signatures of degradation for silicon and other solar cell technologies.

14 SOLAR ENERGY↗
DOE OSTI2018

Tuning of Magnetic and Optical Properties of Co{sub 0.8}Zn{sub 0.2}Fe{sub 2}O{sub 4} Spinel Ferrite Thin Films Based on Post Annealing Temperature

This paper is dedicated to deposit zinc substituted cobalt ferrite (Co{sub 0.8}Zn{sub 0.2}Fe{sub 2}O{sub 4}) thin films on glass substrate using electron beam deposition technique. The effect of post annealing temperature on structural, magnetic, and optical properties of thin films has been investigated. Thin films have been characterized using x-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), vibrating sample magnetometer (VSM), UV-VIS spectroscopy, and spectroscopic ellipsometry (SE) analysis. The as-deposited thin films are amorphous in nature. After deposition, these thin films post annealed at different temperature ranges from 200 to 500 {sup ∘}C to enhance the crystallinity of films. The film post annealed at 200 {sup ∘}C is also amorphous in nature. As the post annealing temperature increases, the thin films become more crystalline. X-ray diffractometer and Raman analysis confirm the formation of cubical inverse spinel structure of thin films. The saturation magnetization of the thin films decreases with the annealing temperature due to the sites occupancy of cations between tetrahedral and octahedral. The reduction in coercivity is correlated with the anisotropy constant, but the anisotropy value is still high which is suitable to form stable magnetic storage memories. The band gap energy are decreased which is mainly attributed due to increase in grain size of the film. It is noted that the band gap energy of these thin films are higher than that of bulk material, so these may be suggested for use in wide band gap applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

In Situ Measurement of the Plane-Strain Modulus of the Solid Electrolyte Interphase on Lithium-Metal Anodes in Ionic Liquid Electrolytes

In this paper, we present an experimental approach for in situ measurement of elastic modulus of the solid electrolyte interphase (SEI), which is formed from reactions between a lithium thin-film [on a polydimethylsiloxane (PDMS) substrate] and a room-temperature ionic liquid (RTIL) electrolyte. The SEI forms under a state of compressive stress, which causes buckling of the sample surface. In situ atomic force microscopy is used to measure the dominant wavelength of the wrinkled surface topography. A mechanics analysis of strain-induced elastic buckling instability of a stiff thin film on a soft substrate is used to determine the plane strain modulus of the SEI from the measured wavelength. The measurements are performed for three RTIL electrolytes: 1-butyl 1-methylpiperidinium bis(trifluoromethylsulfonyl)imide (P 14 TFSI) without any lithium salt, 1.0 M lithium bis(trifluoromethylsulfonyl)imide (Li TFSI) in P 14 TFSI, and 1.0 M lithium bis(fluorosulfonyl)imide (Li FSI) in P 14 TFSI to investigate the influence of lithium salts on the plane strain modulus of the SEI. The measurements yield plane-strain moduli of approximately 1.3 GPa for no-salt P 14 TFSI and approximately 1.6 GPa for 1.0 M Li TFSI in P 14 TFSI and 1.0 M Li FSI in P 14 TFSI. Finally, the experimental technique presented here eliminates some of the uncertainties associated with traditional SEI mechanical characterization approaches and offers a platform to engineer an SEI with desired mechanical properties by approaches that include altering the electrolyte composition.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Structure and physicochemical properties of thin film photosemiconductor cells based on porphine derivatives

Photosemiconductor thin films based on two organic porphine derivatives have been investigated. These compounds have different pendent groups; the film morphology, along with the specific fabrication technique, is determined to a great extent by these groups. The films have been fabricated by vacuum sputtering and using the Langmuir−Schaefer method. According to the atomic force microscopy (AFM) data, the Langmuir−Schaefer films are more homogeneous than the sputtered ones. It is shown that the sputtered films based on substituted porphine have a looser stacking than the initial analog. A spectroscopy study revealed a bathochromic shift of the Soret band in the Langmuir−Schaefer films–sputtered films series. This shift is explained by the increase in the concentration and size of molecular aggregates in sputtered films. It is shown that a polycrystalline C{sub 60} fullerene film deposited onto an amorphous substituted porphine layer improves the photoelectric characteristics of the latter. Both the time stability of the photodiode structure and its ampere‒watt sensitivity increase (by a factor of 10 in the transition regime). The steady-state current does not change. The effect of polarity reversal of the photovoltaic signal is observed in a planar C{sub 60}‒substituted metalloporphine heterostructure, which is similar to the pyroelectric effect. The polarity reversal can be explained by the contribution of the trap charge and discharge current at the interface between the amorphous photosemiconductor and crystalline photosemiconductor to the resulting photoelectric current.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Machine learning-based multidomain processing for texture-based image segmentation and analysis

Atomic and molecular resolved atomic force microscopy (AFM) images offer unique insights into materials' properties such as local ordering, molecular orientation, and topological defects, which can be used to pinpoint physical and chemical interactions occurring at the surface. Utilizing machine learning for extracting underlying physical parameters increases the throughput of AFM data processing and eliminates inconsistencies intrinsic to manual image analysis, thus enabling the creation of reliable frameworks for qualitative and quantitative evaluation of experimental data. Here, we present a robust and scalable approach to the segmentation of AFM images based on flexible pre-selected classification criteria. The usage of supervised learning and feature extraction allows us to retain the consideration of specific problem-dependent features (such as types of periodical structures observed in the images and the associated numerical parameters: spacing, orientation, etc.). We highlight the applicability of this approach for the segmentation of molecular resolved AFM images based on the crystal orientation of the observed domains, automated selection of boundaries, and collection of relevant statistics. Finally, we outline a general strategy for machine learning-enabled analysis of nanoscale systems exhibiting periodic order that could be applied to any analytical imaging technique

36 MATERIALS SCIENCE↗
DOE OSTI2025

Predictive numerical modeling of plasma-induced surface roughness and wettability evolution in LM-PAEK/CF tape

Plasma surface modification effectively enhances adhesion in thermoplastic composites, yet its impacts on high-performance polymers like low-melting polyaryletherketone (LM-PAEK) remain inadequately quantified. Here, this study integrates experimental analysis and numerical modeling to characterize surface roughness and wettability changes in LM-PAEK/carbon fiber composites treated with atmospheric plasma. Atomic Force Microscopy quantified surface topography (n = 10 per condition for contact angles), while static contact-angle assessments measured wettability. Roughness rapidly increased from ∼0.2 nm to 1.6 nm, and contact angle reduced from ∼90° to 24°, both stabilizing after 25–30 s of exposure. A semi-empirical, physics-informed framework was calibrated to these data, coupling surface chemistry via the Owens–Wendt decomposition with topography via the Wenzel roughness factor, and evaluated using out-of-sample (cross-validated) tests, while static contact angle assessments measured wettability. Numerical predictions matched experimental results closely (RMSE <5%, R 2 > 0.95). Incorporating material-specific parameters, the calibrated model supports plasma-treatment optimization and provides quantitative guidance for improving interfacial adhesion in thermoplastic composite manufacturing.

Atomic Force Microscopy↗
DOE OSTI2019

The Effect of Crystallographic Orientation and Nanoscale Surface Morphology on Poly -Si/SiO x Contacts for Silicon Solar Cells

High-efficiency crystalline silicon (Si) solar cells require textured surfaces for efficient light trapping. However, passivation of a textured surface to reduce carrier recombination is difficult. Here, we related the electrical properties of cells fabricated on a KOH-etched, random pyramidal textured Si surface to nanostructure of the passivated contact and the textured surface morphology. The effects of both microscopic pyramidal morphology and nanoscale surface roughness on passivated contacts consisting of a polycrystalline Si (poly-Si) deposited on top of an ultrathin, 1.5-2.2 nm, SiO x layer is investigated. Using atomic force microscopy we show a pyramid face, which is predominantly a Si(111) plane to be significantly rougher than a polished Si(111) surface. This roughness results in a nonuniform SiOx layer as determined by transmission electron microscopy (TEM) of a poly-Si/SiO x contact. Our device measurements also show an overall more resistive, and hence thicker SiO x layer over the pyramidal surface as compared to a polished Si(111) surface, which we relate to increased roughness. Using electron-beam-induced current measurements of poly-Si/SiO x contacts we further show that the SiO x layer near the pyramid valleys is preferentially more conducting, and hence likely thinner than over pyramid tips, edges and faces. Hence, both the microscopic pyramidal morphology and nanoscale roughness lead to nonuniform SiO x layer, thus leading to poor poly-Si/SiO x contact passivation. Finally, we report >21% efficient and =80% fill factor front/back poly-Si/SiO x solar cells on both single-side and double-side textured wafers without the use of transparent conductive oxide layers and show that the poorer contact passivation on a textured surface is limited to boron-doped poly-Si/SiO x contacts.

14 SOLAR ENERGY↗
DOE OSTI2016

Fabrication of electrocatalytic Ta nanoparticles by reactive sputtering and ion soft landing

About 40 years ago, it was shown that tungsten carbide exhibits similar catalytic behavior to Pt for certain commercially relevant reactions, thereby suggesting the possibility of cheaper and earth-abundant substitutes for costly and rare precious metal catalysts. In this work, reactive magnetron sputtering of Ta in the presence of three model hydrocarbons (2-butanol, heptane, and m-xylene) combined with gas aggregation and ion soft landing was employed to prepare organic-inorganic hybrid nanoparticles (NPs) on surfaces for evaluation of catalytic activity and durability. The electro-catalytic behavior of the NPs supported on glassy carbon was evaluated in acidic aqueous solution by cyclic voltammetry. The Ta-heptane and Ta-xylene NPs were revealed to be active and robust toward promotion of the oxygen reduction reaction, an important process occurring at the cathode in fuel cells. In comparison, pure Ta and Ta-butanol NPs were essentially unreactive. Characterization techniques including atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) were applied to probe how different sputtering conditions such as the flow rates of gases, sputtering current, and aggregation length affect the properties of the NPs. AFM images reveal the focused size of the NPs as well as their preferential binding along the step edges of graphite surfaces. In comparison, TEM images of the same NPs on carbon grids show that they bind randomly to the surface with some agglomeration but little coalescence. The TEM images also reveal morphologies with crystalline cores surrounded by amorphous regions for NPs formed in the presence of 2-butanol and heptane. In contrast, NPs formed in the presence of m-xylene are amorphous throughout. XPS spectra indicate that while the percentage of Ta, C, and O in the NPs varies depending on the sputtering conditions and hydrocarbon employed, the electron binding energies of the elements are similar for all of the NPs. Here, the difference in reactivity between the NPs is attributed to their Ta/C ratios. Collectively, the findings presented herein indicate that reactive magnetron sputtering and gas aggregation combined with ion soft landing offer a promising physical approach for the synthesis of organic-inorganic hybrid NPs that have potential as low-cost durable substitutes for precious metals in catalysis

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Effect of CO 2 on the water slip flow at silica surfaces for nanometer slit pores of talc

In our previous study, Molecular Dynamics (MD) simulated water flow with no dissolved gas in nanometer slit pores of the hydrophobic talc surfaces revealed a slip length of about 0.5 nm, which is close to the size of “water exclusion zone” but much less than experimental slip length. Atomic Force Microscopy (AFM) imaging confirmed the presence of pancake shape nanobubbles at the hydrophobic talc (001) surface (size from tens to hundreds of nanometers). The effect of CO 2 on water slip flow in talc nanopores is reported to reveal the importance of dissolved gas for confined fluid flow. MD simulated 7 nm CO 2 nanobubbles were found to attach and spread at the talc (001) surface, consistent with the AFM observation. Simulated CO 2 saturated water flow in the slit pores of talc (001) surfaces predicted the generation of CO 2 nanobubbles at the end of the slit pore, due to the stabilization of a CO 2 film at the talc (001) surfaces and a water barrier at the edge surfaces of talc. A “critical thickness” of about 1.5 nm was found for CO 2 nanobubbles to be stabilized at the end of the talc (001) surface. With 1.5 nm CO 2 nanobubbles at the talc (001) surface of a 6 nm slit pore, a water slip length of 1.8 nm was determined. Furthermore, the nanometer slit pore simulations with dissolved CO 2 in water revealed an increased slip length. It is expected that an increased slip length value would be found with an increased CO 2 film thickness.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Surface deposition of nanometer scale carbon structures on Bi 2 Sr 2 CaCu 2 O 8+δ using a low-cost scanning electron microscope

In this work, we investigate optically active nanostructures on Bi 2 Sr 2 CaCu 2 O 8+δ (BSCCO). The nanostructures are constructed from carbon nanocrystals formed using the electron beam of a scanning electron microscope to locally decompose residual hydrocarbons at the BSCCO surface. Atomic force microscopy is used to characterize the dimensions of these structures as a function of beam exposure time. This technique has been used to induce localized intercalation to form carbon nanoparticles up to tens of nanometers into a variety of 2D materials. Cross-sectional scanning transmission electron microscopy in BSCCO shows the presence of these carbon deposits on the surface, but there is no evidence they penetrate into the BSCCO substrate. Therefore, this technique is not suitable for localized intercalation in BSCCO, and it does have promise as a cost-effective approach to pattern nanometer scale etch stops.

2D materials↗
DOE OSTI2020

Reduction of uranyl and uranyl-organic complexes mediated by magnetite and ilmenite: A combined electrochemical AFM and DFT study

Reduction of mobile aqueous uranyl complexes can be hindered by the strength of the uranyl-ligand complex and the resistivity of the complexes to electron transfer. Semiconducting solids, such as magnetite (Fe 3 O 4 ) and ilmenite (FeTiO 3 ), can facilitate otherwise-slow electron transfer between the reductant and oxidant, especially if these species are adsorbed on their surfaces as inner-sphere complexes. Electrons can then be shuttled through the surface or the structure. This process can be facilitated by either finding a new electron transfer path or by weakening or destroying the ligand-uranyl complex. Using in situ electrochemical atomic force microscopy (EC-AFM), we imaged reduction products of uranyl as mediated by magnetite and ilmenite in the absence or presence of the organic ligands, ethylenediaminetetraacetate (EDTA) and oxalate. In situ images of uranyl reduction show gradual nucleation and growth of reduced uranium on the mineral surfaces with decreasing reduction potentials. X-ray photoelectron spectroscopy (XPS) measurements indicate pentavalent uranium as the dominant uranium species resulting from uranyl reduction mediated by magnetite and ilmenite. The reduction potentials of uranyl-organic species relevant to our reaction system, (U VI O 2 ∙oxalate) 0 and (U VI O 2 ∙HEDTA) - , are derived using quantum–mechanical modeling and compared with the midpoint potentials obtained from cyclic voltammetry measurements. The spectroscopic, electrochemical, and computational data suggest that the catalysis of Fe-bearing minerals facilitates the reduction of uranyl-organic complexes. U(VI)-oxalate complexes are redox-active and participate directly in the reduction mediated by magnetite. In the presence of EDTA, reduction of uranyl may proceed in concert with ligand exchange between metals (i.e., U and Fe) on the mineral surface. Finally, the proposed mechanism is the breaking of uranyl-organic bonds upon interaction with the mineral surface followed by the formation of Fe-organic bonds, thereby allowing the reduction of hexavalent uranyl to pentavalent one.

58 GEOSCIENCES↗
DOE OSTI2016

Differential elastic responses to barrier-altering agonists in two types of human lung endothelium

Vascular integrity is primarily determined by endothelial cell (EC) cytoskeletal structure that is differentially regulated by various stimuli. In this study, atomic force microscopy (AFM) was used to characterize structural and mechanical properties in the cytoskeleton of cultured human pulmonary artery EC (HPAEC) and human lung microvascular EC (HLMVEC) by determining elastic properties (Young's modulus) in response to endogenous barrier protective agents sphingosine 1-phosphate (S1P) and hepatocyte growth factor (HGF), or the barrier disruptive molecule thrombin. Initial studies in unstimulated cells indicate higher baseline peripheral elastic modulus values in HPAEC (mean 2.9 KPa) than in HLMVEC (1.8 KPa). After 30 min of stimulation, S1P induced the highest Young's modulus increase (6.1 KPa) compared to the other barrier enhancing stimuli, HGF (5.8 KPa) and the pharmaceutical agent and S1P analog FTY720 (4.1 KPa). In contrast, the barrier disruptive agent thrombin decreased values from 2.5 KPa to 0.7 KPa depending on the cell type and treatment time. AFM topographical imaging supports these quantitative biophysical data regarding differential peripheral elastic properties in EC. Overall, these AFM studies provide novel insights into the biomechanical properties of human lung EC that regulate vascular barrier function and have potential applicability to pathophysiologic vascular leak syndromes such as acute lung injury. - Highlights: • AFM dynamically measures cellular biophysical properties in live endothelial cells. • Macrovascular human lung EC exhibit different biophysical responses than microvascular. • Agonists that promote EC barrier function increase peripheral elastic properties. • Provide insights into potential therapeutic modulation of human lung EC.

60 APPLIED LIFE SCIENCES↗