Biological applications of scanning probe microscopies

Morris, Victor J.

doi:10.1016/0079-6107(94)90008-6

Cited by 67 publications

(19 citation statements)

References 229 publications

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“…Dried, wet-fixed and living cells have formed three major subjects of investigation over recent years (Häberle et al, 1991;Henderson et al, 1992;Kasas et al, 1993;Barbee et al, 1994). One of the advantages of AFM over SEM is the fact that samples require no coating, no vacuum is needed and electrons are avoided (Morris, 1994). In addition, the AFM can be successfully operated in an aqueous environment (Oberleithner et al, 1993;Beckmann et al, 1994;Le Grimellec et al, 1994;.…”

Section: Introductionmentioning

confidence: 99%

“…Since its invention by Binnig et al (1986), atomic force microscopy (AFM), also called scanning force microscopy (SFM), has been used to image a wide variety of samples (for reviews see Hansma & Hoh, 1994;Morris, 1994). Dried, wet-fixed and living cells have formed three major subjects of investigation over recent years (Häberle et al, 1991;Henderson et al, 1992;Kasas et al, 1993;Barbee et al, 1994).…”

Section: Introductionmentioning

confidence: 99%

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Comparative atomic force and scanning electron microscopy: an investigation on fenestrated endothelial cells in vitro

Braet¹,

Kalle

Zanger³

et al. 1996

Journal of Microscopy

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SummaryRat liver sinusoidal endothelial cells (LEC) contain fenestrae, which are clustered in sieve plates. Fenestrae control the exchange of fluids, solutes and particles between the sinusoidal blood and the space of Disse, which at its back side is flanked by the microvillous surface of the parenchymal cells. The surface of LEC can optimally be imaged by scanning electron microscopy (SEM), and SEM images can be used to study dynamic changes in fenestrae by comparing fixed specimens subjected to different experimental conditions. Unfortunately, the SEM allows only investigation of fixed, dried and coated specimens. Recently, the use of atomic force microscopy (AFM) was introduced for analysing the cell surface, independent of complicated preparation techniques. We used the AFM for the investigation of cultured LEC surfaces and the study of morphological changes of fenestrae. SEM served as a conventional reference.AFM images of LEC show structures that correlate well with SEM images. Dried-coated, dried-uncoated and wetfixed LEC show a central bulging nucleus and flat fenestrated cellular processes. It was also possible to obtain height information which is not available in SEM. After treatment with ethanol or serotonin the diameters of fenestrae increased (6%) and decreased (ÿ15%), respectively. The same alterations of fenestrae could be distinguished by measuring AFM images of dried-coated, dried-uncoated and wet-fixed LEC. Comparison of dried-coated (SEM) and wetfixed (AFM) fenestrae indicated a mean shrinkage of 20% in SEM preparations. In conclusion, high-resolution imaging with AFM of the cell surface of cultured LEC can be performed on dried-coated, dried-uncoated and wet-fixed LEC, which was hitherto only possible with fixed, dried and coated preparations in SEM and transmission electron microscopy (TEM).

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comparative atomic force and scanning electron microscopy: an investigation on fenestrated endothelial cells in vitro

Braet¹,

Kalle

Zanger³

et al. 1996

Journal of Microscopy

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“…With AFM, samples may be imaged in air or in fluids, including culture medium or buffer, in situ, or after processing according to established histological procedures (7,34,48). AFM is nondestructive and nonperturbing, and it can be applied to soft biological samples, particularly when tapping mode scanning is employed (24,62).…”

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confidence: 99%

Atomic Force Microscopy Investigation of Human Immunodeficiency Virus (HIV) and HIV-Infected Lymphocytes

Kuznetsov¹,

Victoria²,

Robinson

et al. 2003

J Virol

103

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Isolated human immunodeficiency virus (HIV) and HIV-infected human lymphocytes in culture have been imaged for the first time by atomic force microscopy (AFM). Purified virus particles spread on glass substrates are roughly spherical, reasonably uniform, though pleomorphic in appearance, and have diameters of about 120 nm. Similar particles are also seen on infected cell surfaces, but morphologies and sizes are considerably more varied, possibly a reflection of the budding process. The surfaces of HIV particles exhibit "tufts" of protein, presumably gp120, which do not physically resemble spikes. The protein tufts, which number about 100 per particle, have average diameters of about 200 Å, but with a large variance. They likely consist of arbitrary associations of small numbers of gp120 monomers on the surface. In examining several hundred virus particles, we found no evidence that the gp120 monomers form threefold symmetric trimers. Although >95% of HIV-infected H9 lymphocytic cells were producing HIV antigens by immunofluorescent assay, most lymphocytes displayed few or no virus on their surfaces, while others were almost covered by a hundred or more viruses, suggesting a dependence on cell cycle or physiology. HIV-infected cells treated with a viral protease inhibitor and their progeny viruses were also imaged by AFM and were indistinguishable from untreated virions. Isolated HIV virions were disrupted by exposure to mild neutral detergents (Tween 20 and CHAPS) at concentrations from 0.25 to 2.0%. Among the products observed were intact virions, the remnants of completely degraded virions, and partially disrupted particles that lacked sectors of surface proteins as well as virions that were split or broken open to reveal their empty interiors. Capsids containing nucleic acid were not seen, suggesting that the capsids were even more fragile than the envelope and were totally degraded and lost. From these images, a good estimate of the thickness of the envelope protein-membrane-matrix protein outer shell of the virion was obtained. Treatment with even low concentrations (<0.1%) of sodium dodecyl sulfate completely destroyed all virions but produced many interesting products, including aggregates of viral proteins with strands of nucleic acid.

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“…The unique utility of xanthan microgels in various applications is due to the strong inter-and intramolecular aggregation. As shown by atomic force microscopy (AFM) [35][36][37][38], the entangled network of individual fibrous molecules is formed when a clear solution of xanthan is dried on a mica surface, as shown in Figure 17.2a, which is taken from Ref. [38].…”

Section: Origin Production and Molecular Properties Of Xanthan Gummentioning

confidence: 99%

Applications of Biopolymer Microgels

Pashkovski

2011

Microgel Suspensions

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IntroductionAs a result of their structural versatility, rich dynamic behavior, biocompatibility, and sustainability, biopolymer microgels are employed in a wide range of industrial applications. Most biopolymers are linear or branched macromolecules forming microgel particles due to intermolecular binding. As was discussed in previous chapters, an essential property of microgel particles is their ability to swell, thus occupying a large volume in solution at very low-weight fractions of polymer. In the case of synthetic microgels, swelling is due to osmotic effects and the equilibrium swelling ratio is given by a balance between the entropic elasticity of the macromolecules, the polymer-solvent interactions [1-3], and, for flexible polyelectrolytes, the ionic strength and/or solution pH. By contrast, microgels of biological origin are composed of relatively rigid macromolecules; it is this intrinsic rigidity that largely determines the swelling of these biopolymer microgels.Above a critical overlap, concentrated suspensions of microgel particles behave as jammed materials [4,5], or more precisely, as soft glassy materials [6], which possess both a high elastic modulus and a yield stress. In the linear viscoelastic regime, the stress relaxation is very slow because the stress relaxes via collective rearrangements of the microgel particles. This makes microgels ideal for applications in consumer and food industries, where they are used to stabilize emulsions and suspensions and to control the rheological characteristics of the products. Microgel particles formed by biopolymers are preferred in pharmaceutical, food, and oral care industries due to their natural origin and biocompatibility [7][8][9]. In addition, microgels of biological origin have found applications in oil recovery because of their high solubility in water, low sensitivity to temperature, and high thickening potential. Biogels also find applications in drug delivery, particularly for oral [10] and ocular [11] delivery.There are other important reasons for using microgels of biological origin. First, high prices of petrochemicals make synthetic microgels, such as polyacrylates or Microgel Suspensions: Fundamentals and Applications Edited

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Biological applications of scanning probe microscopies

Cited by 67 publications

References 229 publications

Comparative atomic force and scanning electron microscopy: an investigation on fenestrated endothelial cells in vitro

Comparative atomic force and scanning electron microscopy: an investigation on fenestrated endothelial cells in vitro

Atomic Force Microscopy Investigation of Human Immunodeficiency Virus (HIV) and HIV-Infected Lymphocytes

Applications of Biopolymer Microgels

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