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Bioresponsive Hydrogels for Controlled Drug Delivery
Published in Deepa H. Patel, Bioresponsive Polymers, 2020
Tamgue Serges William, Dipali Talele, Deepa H. Patel
The scanning electron microscope (SEM) uses a focused beam of high-energy electrons to generate a variety of signals at the surface of solid specimens. SEM is used to reveal information about sample, surface morphology, chemical composition, and crystalline structure. Areas of approximately 1 cm to 5 microns in width can be imaged in a scanning mode using conventional SEM techniques (magnification ranging from 20X to approximately 30,000X, spatial resolution of 50 to 100 nm). SEM study is usually used also to determine pore size in the sample.
Electron Microscopy in Lung Research
Published in Joan Gil, Models of Lung Disease, 2020
Two types of electron microscope are widely available: transmission electron microscopes (TEMs) and scanning electron microscopes (SEMs). Each uses a different mechanism of image formation and gives a different kind of information (Fig. 1) (Watt, 1985). In the TEM, a thin specimen, usually less than 0.1 μm thick, is placed in the electron beam. The electrons pass through the specimen and are brought to a focus on a fluorescent screen or photographic film beneath it. Contrast results from scattering of electrons as they pass through the specimen. The unscattered electrons pass through the specimen to interact with the fluor of the screen or photographic emulsion. Scattering of electrons is a function of the atomic number of the atoms making up the specimen. The bulk of biological material is made up of elements of low atomic number (hydrogen, oxygen, carbon, and nitrogen), so most biological samples have little inherent electron contrast. Contrast is usually introduced by the OsO4 used nearly universally as a fixative, and by the use of heavy metal stains.
Animal Models of Tendon Repair
Published in Yuehuei H. An, Richard J. Friedman, Animal Models in Orthopaedic Research, 2020
Standard histologic methods have been used quite extensively to study tendons. For light microscopy, specimens are fixed in 10% neutral buffered formalin, embedded in paraffin, sectioned and stained. Haematoxylin and eosin is the most commonly used stain. Other commonly used stains include Milligan’s trichrome, Van Gieson’s and Verhoeff’s stains. Transmission and scanning electron microscopy are also useful techniques. Specimens for SEM may be fixed in 0.2 NSorensen’s phosphate-buffered glutaraldehyde, dehydrated in an ethanol series and dried in liquid CO2.56
Lipoplexes and polyplexes as nucleic acids delivery nanosystems: The current state and future considerations
Published in Expert Opinion on Drug Delivery, 2022
Bruno Costa, Beatriz Boueri, Claudia Oliveira, Isabel Silveira, Antonio J. Ribeiro
In line with the non-viral vectors thorough characterization, no single technique can fully characterize a disperse nanosystem sample. All size distribution assessment results presented in Table 1 stem from DLS measurements, providing the mean hydrodynamic diameter. Yet, it is advocated to resort to at least one other method, such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM), popular imaging techniques. Found to make use of TEM as a second method are just three among all reported vectors in Table 1. In recent times, nanoparticle tracking analysis or NTA emerged as a better verification tool for DLS [100]. Even though none of Table 1ʹs entries reported making use of it, NTA is arguably the best tool to verify DLS measurements since it relies on the same physical property, their diffusion coefficient. While the size reports of DLS rely on fluctuations of the scattered light, NTA ones depend on the number of single particles captured in a series of optical images. In this way, we can account for DLS’s inherent limitation of biased intensity-based detection when significantly larger aggregates than the main population offset the size distribution curve.
Use of electron microscopy to study platelets and thrombi
Published in Platelets, 2020
Maurizio Tomaiuolo, Rustem I. Litvinov, John W. Weisel, Timothy J. Stalker
The study of platelet biology using electron microcopy methods has a long and rich history. It was not long after the introduction of the electron microscope that the first studies of platelet ultrastructure using transmission electron microscopy were published [1]. Conventional electron microscopy is divided into transmission electron microscopy (TEM) and scanning electron microscopy (SEM). In TEM, a beam of electrons is transmitted through a thin section in order to visualize the internal structures. By contrast in SEM, a focused beam of electrons is used to scan the surface of a specimen. A considerable amount of work went into developing the protocols to fix soft tissues so that they could be imaged by electron microscopy, work strongly motivated by the need to visualize tissues and their internal structures in ways that were not possible with any other microscopy technique before. Once the proper fixation protocols had been developed, electron microscopy became instrumental to study platelets, both for basic research [2] and as a diagnostic tool [3]. Today, conventional TEM and SEM approaches remain valuable tools in platelet and thrombosis research, even as EM approaches continue to evolve and new imaging modalities are developed.
Effect of reserpine on Pseudomonas aeruginosa quorum sensing mediated virulence factors and biofilm formation
Published in Biofouling, 2018
Debaprasad Parai, Malabika Banerjee, Pia Dey, Arindam Chakraborty, Ekramul Islam, Samir Kumar Mukherjee
For scanning electron microscopy (SEM), sample preparation was done following Parai et al. (2017). P. aeruginosa PAO1 was allowed to form biofilms on the glass coverslips (12 mm, Blue Star, Mumbai, India) and subsequently treated with reserpine (IC50 and IC80) for 24 h. Biofilms were fixed with freshly prepared 2% depolymerised paraformaldehyde for 30 min and washed with distilled water. The coverslips were then dehydrated with an increasing concentration series of ethanol (50–100%) for 10 min in each concentration. Images were captured by SEM (EVO® LS 10, Zeiss, Jena, Germany) and analysed by smartSEM graphical user interface software. The imaging conditions were 5–10 kV acceleration potential, 10–15 mm working distance, 50–100 pA probe current and 6,000×/13,000× magnification.