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Results for “Microscopy, Scanning Probe”

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At least 91 records · Page 5Linked to original sources
PubMed2001

Drastic change of local stiffness distribution correlating to cell migration in living fibroblasts.

Sequential images of the local stiffness distribution of living fibroblasts (NIH3T3) were captured under a culture condition using scanning probe microscopy in a force modulation mode. We found a clear relation between cell migration and local stiffness distribution on the cell: When cells were stationary at one position, the stiffness distribution of their cellular surface was quite stable. On the other hand, once the cells started to move, the stiffness in their nuclear regions drastically decreased. Possible explanations for the correlation between the cell migration and the cell stiffness are proposed.

3T3 Cells↗
PubMed2002

Ferroelectric molecular films for nanoscopic ultrahigh-density memories.

The formation and visualization of nanometer-scale polarized domains in ultrathin ferroelectric molecular films by scanning-probe microscopy are described. These operations to the ferroelectric domains correspond to the "writing" and the "reading" process, respectively, for the data-storage application. In addition, nanometer-scale structures and the local electrical properties of the local domains, including the interface effect, are discussed. The achieved minimum diameter of the written ferroelectric domains was 30 nm. The size of the "recording" dot corresponds to the recording density of about 230 Gbit/in.(2). The "erasing" process by switching domains was also demonstrated. Furthermore, nanometer-scale ferroelectric domains using VDF oligomer molecular films were successfully formed, which has opened the way to the control of single molecular dipoles.

Iron↗
PubMed2001

Ultramicrostructure and microthermomechanics of biological IR detectors: materials properties from a biomimetic perspective.

Microstructural organization of the biological infrared (IR) receptors was studied to elucidate their materials properties useful for prospective biomimetic design of artificial IR sensors from organic/polymeric materials. The IR receptors in Melanophila acuminata beetles were studied with ultrahigh-resolution scanning probe microscopy (SPM) in a range of temperatures. By application of micromechanical mapping and thermal stage, we made attempts to reveal the micromechanical and thermomechanical properties of the cuticular apparatus of the IR sensillum. The main component of the cuticular apparatus is an internal endocuticular sphere with a diameter of about 15-20 microm. Highly ordered multilayered organization of the lamellated peripheral mantle of the sphere was confirmed and characterized. We observed that the interlayer spacing of this microstructure varied along the circumference and decreased to 300 nm in the vertex of the sphere. We demonstrated that the microlayered structure is composed of nanolayers with very different micromechanical properties and thermal behaviors. Thermal expansion of the outer mantle was observed, and the local thermal expansion coefficient under given preparation conditions was estimated to be below 1.5 x 10(-4) grad(-1).

Animals↗
PubMed2000

Quantification of the surface morphologies of lactose carriers and their effect on the in vitro deposition of salbutamol sulphate.

Application of the scanning probe microscopy technique for quantitative measurement of the surface roughness of lactose carriers was evaluated. The roughness values of four different lactose carriers were related to the in vitro deposition results of the drug, salbutamol sulphate. The rugosity values of the lactose carriers were represented by Ra values which were in the order of DCL-40>DCL-11>lactose 325M>lactose 200 M. In vitro deposition results using a twin impinger showed that rougher carrier surfaces generally allowed more drug particles to be emitted from the capsules and inhaler but the availability of the drug to stage 2 was reduced, as detachment of drug particles from the carrier surfaces was more hindered. There was an optimum Ra value for greater delivery of the drug particles to stage 2 of the twin impinger. A balance between adherence and detachment of the drug from the carrier surface was needed in order to optimize the delivery of a drug to the desired target sites using a dry powder inhaler.

Adrenergic beta-Agonists↗
PubMed2000

Threshold Energy Effects in Secondary Electron Emission.

In large bandgap semiconductors and insulators, the threshold energies for e-h pair production and ionization damage can lie above the vacuum level. For low energy imaging, a window is then opened whose width is potentially sensitive to local changes in work function, doping level, or acidity. Recent progress and future opportunities for damage-free imaging of these properties using low energy electrons are discussed in the light of the underlying physics, as well as of recent instrumental developments in low energy electron microscopy (LEEM), environmental scanning electron microscopy (ESEM), photoelectron emission microscopy (PEEM), scanned probe microscopy (SPM), and projection electron microscopy.

Journal Article↗
PubMed1998

Analytical Microscopy in the Real Semiconductor Processing World.

: In the microelectronic semiconductor world we are bombarded with reports of how the drive toward faster, denser, lower power-consuming and more reliable semiconductor products will accelerate with time. This paper discusses the instrumental evolution from visible light microscopy to scanning electron microscopy and on to transmission electron microscopy and scanned probe microscopy. The increased demands placed on specimen preparation of precise locations in a semiconductor chip for microscopy are discussed. Analytical microscopy has to be timely in order to be a viable adjunct to semiconductor manufacturing. The factors governing analysis of turn-around time are explained and an optimum strategy is suggested for effective utilization of finite laboratory resources. The new instrumentation available to the microscopist is introduced along with an overview of the exciting new analyses that will be available in the immediate future.

Journal Article↗
PubMed1999

A comparative study of colloidal particles as imaging standards for microscopy.

Colloidal particles have long been used as imaging standards for electron microscopy and, more recently, for scanning probe microscopy. We have analysed gold, polystyrene and silica colloidal particles by both transmission electron microscopy and atomic/scanning force microscopy in an attempt to determine if any can be truly used as 'standards' of shape and/or size. From the transmission electron micrographs, we have obtained precise information of the particle circumference and mean diameter. By comparing the ratio of these to the value for pi, we obtained a measure of the sphericity of the particles. We have also shadowed the particles with metal at a known angle and have analysed the shadow length to determine the particles' heights and shapes. The height information obtained from the shadow length data collected from the transmission electron micrographs was then compared with that obtained by atomic/scanning force microscopy. Our results show that cleaned (washed) silica or polystyrene particles closely approach true spheres. In the case of gold particles, height data obtained from shadow lengths analysed in transmission electron micrographs show good agreement with that obtained from the atomic/scanning force microscopy images even without washing. However, the gold particles often deviate from sphericity. Based upon both the shape and the physical properties of the colloidal particles, silica would be the best choice as a standard. We also have noticed that metal shadowing of colloidal particle samples used for atomic/scanning force microscopy offers an advantage which we call a 'nanoscale metric' visible in the image directly at each particle site. This information can be important if one wishes to use samples prepared from colloidal particles simply and reliably to determine the probe shape for scanning probe microscopy from image deconvolution/restoration methods or as a calibration sample.

Calibration↗
PubMed2002

Room temperature scanning Hall probe microscopy using GaAs/AlGaAs and Bi micro-hall probes.

A room temperature scanning Hall probe microscope system utilizing GaAs/AlGaAs and bismuth micro-Hall probes was used for magnetic imaging of ferromagnetic domain structures on the surfaces of crystalline thin film garnets and permanent magnets. The Bi micro-Hall probes had dimensions ranging between 0.25 and 2.8 microm2 and were fabricated using a combination of optical lithography and focused ion beam milling. The use of bismuth was found to overcome surface depletion effects associated with semiconducting micro-Hall probes. Our experiments demonstrated that Bi is a practical choice of material for fabricating sub-micron sized Hall sensors.

Journal Article↗
PubMed2003

Photonic nanopatterns of gold nanostructures indicate the excitation of surface plasmon modes of a wavelength of 50-100 nm by scanning near-field optical microscopy.

Scanning near-field optical microscopy images of metal nanostructures taken with the tetrahedral tip (T-tip) show a distribution of dark and bright spots at distances in the order of 25-50 nm. The images are interpreted as photonic nanopatterns defined as calculated scanning near-field optical microscopy images using a dipole serving as a light-emitting scanning near-field optical microscopy probe. Changing from a positive to a negative value of the dielectric function of a sample leads to the partition of one spot into several spots in the photonic nanopatterns, indicating the excitation of surface plasmons of a wavelength in the order of 50-100 nm in metal nanostructures.

Gold↗
PubMed1993

Measurement of Howship's resorption lacunae by a scanning probe microscope system.

We have developed a novel ultrastructural assay system for osteoclastic resorptive function. After osteoclasts had been co-cultured on dentine slices for 48 hr, the slices were fixed with glutaraldehyde and examined by means of backscattered electron, scanning electron, and scanning probe microscopies. Backscattered electron images showed areas of low mineralization on dentine surfaces, which, by superimposition of concave-convex images, corresponded to resorption lacunae. The measurement of such resorption lacunae by scanning probe microscopy revealed 3-dimensional topography and their exact depths and volumes. Analysis based on this system provides reliable qualitative and quantitative assessment of osteoclastic resorption.

Animals↗
PubMed2001

Cholesterol, a modulator of membrane-associated Abeta-fibrillogenesis and neurotoxicity.

Recent studies have suggested that cholesterol, an important determinant of the physical state of biological membranes, plays a significant role in the development of Alzheimer's disease. We have employed in situ scanning probe microscopy, fluorescence anisotropy, and electron microscopy to investigate how cholesterol levels within total brain lipid bilayers effect amyloid beta-peptide (Abeta)-assembly. Fluorescence anisotropy measurements revealed that the relative fluidity of the total brain lipid membranes was influenced by the level of cholesterol and the addition of Abeta40 resulted in a decrease in the overall vesicle fluidity. In situ scanning probe microscopy performed on supported planar bilayers of total brain lipid revealed a correlation between membrane fluidity, as influenced by cholesterol level, and the extent of Abeta-insertion and subsequent fibrillogenesis. These observations were consistent with fluorescence microscopy studies of PC-12 and SH-SY5Y cell lines exposed to exogenous Abeta, which revealed an inverse correlation between membrane cholesterol level, and Abeta-cell surface binding and subsequent cell death. These results collectively suggest that Abeta-cell surface interactions are mediated by cellular cholesterol levels, the distribution of cholesterol throughout the cell, and membrane fluidity.

Alzheimer Disease↗
PubMed2000

[Near-field microscopy: from the isolated molecule to the living cell].

Near field (or scanning probe) microscopy is a recent technology which, owing to the huge amount of publications, is becoming a reference method in molecular and cellular imaging. These microscopies consist in the scanning of the sample, line by line, with a very tiny tip and thus providing informations on its surface down to the nanometer scale. These methods gather scanning tunelling microscopy (STM), which measures a current between the tip and the specimen support, atomic force microscopy (AFM), which measures the repulsive and attractive forces of the tip in contact or very close to the specimen, and scanning near field optical microscopies (SNOM), for which a glass tip allows to catch light signals. Atomic force microscopy, which allows the observation of specimens in air or physiological conditions environments, is presently dominant in biology, in complementarity with the classical optical and electron microscopies, which by the way, have also shown considerable improvements during the last years. The complementarity of these microscopies is due to their very different basic principles, which provide them various possibilities and limits. The biological applications of STM is limited by the need of conducting samples, but the different models of SNOM, often still in development, allow to consider very interesting applications, particularly for detecting very faint and tiny fluorescence signals. Different examples will be given concerning the visualization by AFM of isolated DNA molecules, naked or associated with proteins, the observation of intact or decondensed chromosomes, as well as living cells. One of the originality of AFM is its capacity to observe objects in a wide range of enlargements, with fields from a few hundred of nanometers to several micrometers.

Animals↗
PubMed2003

Nanoscale in vivo evaluation of the stiffness of Drosophila melanogaster integument during development.

A quasistatic nanoindentation technique, enhanced by scanning probe microscopy, was used to measure cuticle stiffness of live Drosophila melanogaster during its larval, pupal, and early adult development in vivo. Stiffness was defined as the reduced elastic modulus (E(r)), which is a material property related to the elastic modulus. E(r) was measured at the local contact while indenting the live sample at a constant loading rate using a spherical tip. E(r) was derived from the resultant force-displacement curves. Insect cuticle exhibits viscoelastic behavior. Constant loading rate quasistatic measurements were used so that the effects of viscosity and contact force adhesion introduced systematic measurement effects. E(r) values were as follows: larvae, mean (SE), 0.39 (0.01) MPa; the puparium without evidence of adult structures 15.43 (1.78) MPa; and the adult, measured in the puparium at the completion of metamorphosis, 4.37 (0.31) MPa. Thus, as expected, the puparium and adult cuticle were very much stiffer than larval cuticle. Results also indicated stiffness variation that related to developmental events. This study has shown that this quasistatic nanoindentation-scanning probe microscopy approach is a suitable method for analyzing live biological samples.

Animals↗
PubMed1992

The scanning probe microscope.

Scanning probe microscopy has evolved into a powerful tool since its inception in 1982. The scanning probe microscope has found applications in metrology, spectroscopy, and lithography. We will review the background of the technology, discuss the different types of scanning probe microscopes including the scanning tunneling microscope and the scanning force microscope, and present many of the applications for the instrument.

DNA↗
PubMed2001

High resolution scanning force microscopy of cardiac myocytes.

The advent of scanning probe microscopy has introduced a powerful new method of probing the structural features of biological specimens. In this study, high resolution atomic force microscopy micrographs of single, isolated, cardiac myocytes are presented. Significantly, our images show not only the features to be expected of the external sarcolemma, but also resolve sub-surface features, including the striated pattern of the contractile proteins and their associated sarcoplasmic reticulum and mitochondria.

Animals↗
PubMed2000

Atomic force microscopy with carbon nanotube probe resolves the subunit organization of protein complexes.

Among many scanning probe microscopies, atomic force microscopy (AFM) is a useful technique to analyse the structure of biological materials because of its applicability to non-conductors in physiological conditions with high resolution. However, the resolution has been limited to an inherent property of the technique; tip effect associated with a large radius of the scanning probe. To overcome this problem, we developed a carbon nanotube probe by attaching a carbon nanotube to a conventional scanning probe under a well-controlled process. Because of the constant and small radius of the tip (2.5-10 nm) and the high aspect ratio (1:100) of the carbon nanotube, the lateral resolution has been much improved judging from the apparent widths of DNA and nucleosomes. The carbon nanotube probes also possessed a higher durability than the conventional probes. We further evaluated the quality of carbon nanotube probes by three parameters to find out the best condition for AFM imaging: the angle to the tip axis; the length; and the tight fixation to the conventional tip. These carbon nanotube probes, with high vertical resolution, enabled us to clearly visualize the subunit organization of multi-subunit proteins and to propose structural models for proliferating cell nuclear antigen and replication factor C. This success in the application of carbon nanotube probes provides the current AFM technology with an additional power for the analyses of the detailed structure of biological materials and the relationship between the structure and function of proteins.

Carbon↗