scholarly journals Abstract P-42: Structure of Hydrogels of an Anionic Polysaccharide Studied by Freeze-Fracture Transmission Electron Microscopy

2021 ◽  
Vol 11 (Suppl_1) ◽  
pp. S30-S31
Author(s):  
Andrey Shibaev ◽  
Maria Smirnova ◽  
Olga Philippova ◽  
Vladimir Matveev ◽  
Anatoly Chalykh
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Liquid Nitrogen ◽  
Freeze Fracture ◽  
Mesh Size ◽  
Polymer Chains ◽  
Self Healing ◽  
Polymer Backbone ◽  
Transmission Electron ◽  
Cross Linker

Background: Polysaccharide hydrogels draw attention due to the ability to form mechanically tough gels at low concentrations (typically 1 wt% or lower), combined with biocompatibility and biodegradability. Biopolymer hydrogels can be used as a matrix for cell growth, in order to obtain materials for the replacement of damaged tissues. “Physical” gels with macromolecules cross-linked by dynamic reversible cross-links are of great interest due to their self-healing ability. However, investigation of the native un-perturbed structure of such hydrogels presents a challenge, since they collapse upon drying, and present a difficulty for preparing a thin specimen for cryo-TEM experiments due to very high viscosity. The aim of this work is to study the native structure of hydrogels of an anionic polysaccharide – carboxymethyl hydroxypropyl guar (CMHPG) – cross-linked by borax. Methods: Freeze-fracture transmission electron microscopy (FF-TEM) was conducted on a Phillips EM-301 microscope. A small volume of the sample (100 μl) was put into the copper cell and cooled down by liquid nitrogen, put under vacuum (10−5 torr) at continuous cooling with liquid nitrogen, and fractured. The surface was etched for 10–20 min at 10−5 torr and then replicated by spraying platinum and carbon. Results: The gels have a microphase-separated microstructure – a rather thick (several nm) polymer backbone is seen, which is presumably formed by multiple aggregated macromolecules, and meshes between the backbone do not contain polymer and are filled with solvent. Mesh size determined from the micrographs qualitatively coincides with the value determined from the elastic modulus of the gels. Upon increasing the concentrations of cross-linker, the network becomes denser: the mesh size becomes lower, and the thickness of the backbone increases. Thus, the addition of cross-linker favors the aggregation of polymer chains forming the backbone. Conclusion: It was shown by FF-TEM that cross-linked CMHPG gels have a microphase-separated structure with a dense backbone formed by polymer chains and rather large meshes between them.

A freeze fracture technique for examining human hair medulla with Scanning and Transmission Electron Microscopy

1987 ◽  
Vol 45 ◽  
pp. 868-869
Author(s):  
D. W. Coble ◽  
E. O. Kairinen
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Liquid Nitrogen ◽  
Human Hair ◽  
Freeze Fracture ◽  
Low Viscosity ◽  
Transmission Electron ◽  
Scanning Electron

Examination of hair medulla by transmission electron microscopy (TEM) is difficult because of the keratinous composition of hair and because of sectioning problems that result from insufficient infiltration and nonmiscibility of hair with embedding resins, even those of low viscosity. Although longitudinally cutting or tearing fibers will expose the medulla for embedment or direct viewing, considerable disruption occurs in its structure. Less disruption results from the use of freeze fracture techniques for either transmission or scanning electron microscopy (SEM).Freshly plucked human scalp and beard hairs were submersed in liquid nitrogen for a minimum of three minutes, held at proximal and distal ends with Dumont #10 tweezers, and slowly bent to an arc until the specimens broke at the apex. Customarily, clean bevelled fractures occurred along the tips of the arcs and exposed not only the medulla but also the cortex and cuticle. The fractured specimens were then removed from liquid nitrogen.

scholarly journals Applicability of Freeze-Fracture and Cryo-TEM to Complex Liquids

1992 ◽  
Vol 00 (7) ◽  
pp. 9-9
Author(s):  
Janet L. Burns ◽  
Richard J. Spontak
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Sample Preparation ◽  
Freeze Fracture ◽  
Traditional Methods ◽  
Conventional Transmission Electron Microscopy ◽  
Transmission Electron ◽  
Multicomponent Complex ◽  
Complex Liquids

Traditional methods of sample preparation and analysis in conventional transmission electron microscopy (TEM) are not readily applicable to multicomponent complex liquids which may contain a wealth of microstructural information. Two techniques which facilitate the study of structure in such liquids are freeze-fracture (FF) TEM and cryo-TEM.

Self-Healing and Self-Organized Gold Nanoparticle Films at a Water/Organic Solvent Interface

2006 ◽  
Vol 6 (1) ◽  
pp. 130-134 ◽  
Author(s):  
Olivier Balmes ◽  
Jan-Olov Bovin ◽  
Jan-Olle Malm
Keyword(s):  
Thin Film ◽  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Gold Nanoparticles ◽  
Organic Solvent ◽  
Continuous Production ◽  
Self Healing ◽  
Self Organized ◽  
Transmission Electron ◽  
20 Nm

Gold nanoparticles (5 nm and 20 nm) have been synthesized and stabilized with mercaptoundecanol. These particles, although insoluble in water or common organic solvents, spread as a thin film at the liquid–liquid interface between a water phase and an organic phase. Films of these gold nanoparticles have been observed both by conventional transmission electron microscopy of deposited samples and by cryo-transmission electron microscopy of plunge-frozen samples. The film can be monolayered and extend over centimeter-sized areas. The particle films spontaneously re-assemble and self-organize at the interface when disrupted. This self-healing capacity of the film should make it possible to build a device for continuous production and deposition of the film.

Ion implantation in β-SiC: Effect of channeling direction and critical energy for amorphization

1988 ◽  
Vol 3 (2) ◽  
pp. 321-328 ◽  
Author(s):  
J. A. Edmond ◽  
R. F. Davis ◽  
S. P. Withrow ◽  
K. L. More
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Computer Program ◽  
Liquid Nitrogen ◽  
Cross Section ◽  
Damage Accumulation ◽  
Room Temperature ◽  
Critical Energy ◽  
Implantation Dose ◽  
Transmission Electron

Damage in single-crystal β-SiC(100) as a result of ion bombardment has been studied using Rutherford backscattering/channeling and cross-section transmission electron microscopy. Samples were implanted with Al (130 keV) and Si (87 keV) with doses between 4 and 20 × 1014 cm−2 at liquid nitrogen and room temperatures. Backscattering spectra for He+ channeling as a function of implantation dose were initially obtained in the [110] direction to determine damage accumulation. However, the backscattered yield along this direction was shown to be enhanced as a result of uniaxial implantation-induced strain along [100]. Spectra obtained by channeling along this latter direction were used along with the computer program TRIM to calculate the critical energy for amorphization. The results for amorphization of β-SiC at liquid nitrogen and room temperature are ∼ 14.5 eV/atom and ∼ 22.5 eV/atom, respectively.

A freeze-fracture study of the cuticle of adult Nippostrongylus brasiliensis (Nematoda)

Parasitology ◽  
1993 ◽  
Vol 107 (5) ◽  
pp. 545-552 ◽  
Author(s):  
D. L. Lee ◽  
K. A. Wright ◽  
R. R. Shivers
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Freeze Fracture ◽  
Surface Coat ◽  
Nippostrongylus Brasiliensis ◽  
Freeze Fracturing ◽  
Transmission Electron ◽  
Fracture Study ◽  
20 Nm

SUMMARYThe surface of the cuticle of adult Nippostrongylus brasiliensis has been studied by means of the freeze-fracture technique and by transmission electron microscopy. Some of the surface coat appears to have been shed from the surface of the cuticle of adults fixed in situ in the intestine of its host and from the surface of individuals removed from the intestine and freeze-fractured. Freeze-fracturing the cuticle of individuals removed from the host has shown that this surface coat varies in thickness from 30 to 90 nm. The epicuticle is about 20 nm thick and cleaves readily to expose E- and P-faces. The P-face of the epicuticle possesses a small number of particles, similar to intra-membranous particles, whilst the E-face possesses a few, widely scattered depressions. Despite the presence of these particles the epicuticle is not considered to be a true membrane. Freeze-fracturing the remainder of the cuticle has confirmed its structure as described by conventional transmission electron microscopy. Clusters of particles on the P-face of the outer epidermal (hypodermal) membrane and corresponding depressions on the E-face of the membrane are thought to be associated with points of attachment of the cuticle to the epidermis (hypodermis). No differences in appearance of the cuticle and its surface layers were observed in individuals taken from 7-, 10-, 13- and 15-day infections.

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