The Emerging Role of Exosome Nanoparticles in Regenerative Medicine
Harishkumar Madhyastha, Durgesh Nandini Chauhan in Nanopharmaceuticals in Regenerative Medicine, 2022
A pre-processing step is often necessary for biological sample preparation, to be visible under EM (Mehdizadeh et al. 2014). These sample preparations consisted of some treatments like dehydration (organic solvents are replaced by water), chemical fixation (chemical crosslinking of lipids with osmium tetroxide and proteins with formaldehyde or glutaraldehyde), and cryofixation (called cryogenic electron microscopy (cryo-EM)). Sometimes electron beam may damage the sample to overcome this problem. The cryo-EM could be applied for EVs analysis. It is the method used to study heterogeneous shapes of exosomes close to their native state. The specimen rapidly (in milliseconds) becomes cooled and frozen to cryogenic temperatures (usually at the temperature of liquid nitrogen), which are enough to form icecrystals. The water molecules are not regularly arranged in a hexagonal lattice and a vitreous ice is formed, which is an amorphous solid form of water (Tivol et al. 2008; Debenedetti 2003).
Cellular Injury Associated with Organ Cryopreservation: Chemical Toxicity and Cooling Injury
John J. Lemasters, Constance Oliver in Cell Biology of Trauma, 2020
Organ cryopreservation is a frontier discipline both in cryobiology and in pathology. Cryopreservation refers to preservation at cryogenic temperatures, which for our present purposes will be considered any temperature below about -100°C. For organ cryopreservation to succeed, it is necesary that the organ survive low-temperature exposure per se, and it appears necessary for the organ to survive exposure to certain chemical agents (known generically as cryoprotective agents [CPAs] or cryoprotectants) at concentrations so high that they preclude ice formation during cooling.1 Aqueous solutions that do not freeze upon cooling eventually revert to the glassy state, a glass being a liquid the molecular motions of which have been largely arrested.2 This conversion to the glassy state is referred to as vitrification, and organ cryopreservation in the absence of ice is referred to as organ vitrification.
Alternative Modes of Tissue Coagulation and Removal
Sujoy K. Guba in Bioengineering in Reproductive Medicine, 2020
Within the tissue around the probe there is a temperature gradient with the lowest temperature being in the immediate vicinity of the probe and the temperature further away being higher, that is closer to the normal body temperature (Figure 14.3). Approximately a hemispherical pattern of temperature isotherms prevail.8 The temperature can be monitored by bioelectrical low frequency measurement.9 The region near the probe may be considered as a fast freezing and slow thawing area where tissue necrosis is virtually complete. Beyond this zone variable reactions of necrosis, blood vessel thrombosis, inflammatory effects on thawing and minimal reversible cellular function change are manifested. The nature and size of the lesion to be produced therefore determines the size of the probe to be used and the equipment cooling parameters. Hence different types of cryogenic systems and probes have been developed for a variety of medical applications.
Spray freeze-drying for inhalation application: process and formulation variables
Published in Pharmaceutical Development and Technology, 2022
Mostafa Rostamnezhad, Hossein Jafari, Farzad Moradikhah, Sara Bahrainian, Homa Faghihi, Reza Khalvati, Reza Bafkary, Alireza Vatanara
Unlike the SFV/L, the nozzle in the SFL is located in the lower parts, directly in contact with the liquid (Figure 1). This liquid can be cryogenic. SFL can be conducted at atmospheric pressure with liquid nitrogen, hydrofluoroether, pentane, and argon. Also, it is applicable in the pressurized systems of liquid carbon dioxide, propane, and/or ethane. Droplets are frozen immediately after formation. The cryogenic agents may be stirred to prevent particle aggregation. Then, the frozen droplets are freeze-dried to produce a dry powder with an elegant flow. In the SFL, a liquid–liquid collision occurs between the atomized droplets ejected from the nozzle and the cryogenic liquid. The higher density and viscosity of liquids compared to gases cause the necessity for more vigorous atomization leading to create smaller droplets accordingly (Hu et al. 2002). The smaller droplets increase the specific surface area of the resultant particles and the heat transfer (Engstrom et al. 2007). Furthermore, supersaturation generates a high rate of nucleation from the dissolved components. Rapid nucleation, followed by a limited core growth, results in very small particles (Hu et al. 2002). The high surface area and minimum drug destruction have made this method suitable for preparing the dosage forms (Yu et al. 2004).
Frostbite injury; an unknown risk when using nitrous oxide as a party drug
Published in Acta Chirurgica Belgica, 2020
Marcel Libertus Johannes Quax, Timothy Jason Van Der Steenhoven, Benjamin Lucas Emmink
Cryogenic burns differ from thermal burns; with cold burns, the cells freeze and the structural integrity of the cells becomes damaged. Two distinct mechanisms are responsible for tissue injury in cold burns: cellular death occurring at the time of exposure to the cold, and deterioration and necrosis to progressive dermal ischemia. The freezing of tissue leads initially to the formation of extracellular ice crystals. These ice crystals expand, causing the mechanical destruction of cells. Initially, the body responds to tissue cooling by alternating cycles of vasoconstriction and vasodilatation. With vasodilatation comes the reestablishment of blood flow and, thus, thawing. Intra- and extracellular ice crystals are formed, and cause thrombosis of the capillaries [5]. This thrombosis and partial thawing and refreezing causes the most damage [6].
Hydroxypropyl beta cyclodextrin: a water-replacement agent or a surfactant upon spray freeze-drying of IgG with enhanced stability and aerosolization
Published in Drug Development and Industrial Pharmacy, 2020
Shahriar Milani, Homa Faghihi, Abdolhosein Roulholamini Najafabadi, Mohsen Amini, Hamed Montazeri, Alireza Vatanara
Initially, human IgG was dialyzed against deionized water (cut off: 15 kDa) at 4 °C overnight to achieve a pure IgG solution. Aqueous antibody solutions containing 200 mg IgG with different ratios of HPβCD and trehalose were prepared (Table 1). To prepare a cryogenic vapor for each experiment, a 2 L glass container was selected and filled with 0.4 L liquid nitrogen. Utilizing a lab-scale spray drier equipped with a 2-fluid nozzle (Buchi 191, Switzerland), the feed solution was atomized above the liquid nitrogen at 6 mL/min flow rate. Then, the formed slurry was placed on the bench until the remaining nitrogen was completely evaporated. The prepared frozen droplets were collected and lyophilized using a freeze drier (Christ, Germany). Primary drying took place at –50 °C and 0.005 mbar for 24 h followed by a secondary drying by gradually elevating the temperature to –20 °C over a period of 24 h. The yield of powder recovery was estimated to be about 85%.
Related Knowledge Centers
- Cryobiology
- Cryopreservation
- Cryosurgery
- Helium
- Hydrocarbon
- Neon
- Oxygen
- Nitrogen
- Hydrogen
- Absolute Zero