Abstract

Cryopreservation is an important technique used to store various types of cells, tissues, and organs at very low temperature, usually in liquid nitrogen (-196 °C) [1]. However, freezing and thawing process causes cryo-injuries to cells. During cryopreservation creation of extracellular ice may cause rupture of the cell membrane and recrystallization of intracellular and extracellular ice may further damage the cells during the freezing and thawing process, respectively. Many compounds act as cryoprotectants and are used for protection of cells against freezing. There are two types of cryoprotectants: (a) membrane permeating which can freely diffuse the membrane such as glycerol (G), ethylene glycol (EG) and dimethyl sulfoxide (DMSO); (b) non permeating membrane which cannot permeate the cell membrane such as sugars and antifreeze proteins [2]. Antifreeze proteins (AFPs) and Antifreeze glycoproteins (AFGPs) are produced by certain fish, insects, plants and bacteria that protect them in extremely cold climates from deep freezing temperatures [1]. AFPs act by decreasing the freezing point, modifying the ice-crystal formation process, preventing recrystallization and interacting with plasma membrane at low temperatures [3], thus allowing these species to survive in waters colder than the equilibrium freezing point of their internal fluids [4]. Antifreeze glycoproteins (AFGPs) are categorized into 8 classes of descending size from AFGP1 with Mw =33.7kDa to AFGP8 with Mw =2.6kDa [5]. In their order of discovery, AFPs are sequentially numbered type I, II, III, and IV [6].