Cryopreservation of biological specimens

Abstract

Rapid cooling is the first, critical step in the preservation of biological specimens for examination using a wide variety of electron microscopic techniques. The choice of which cooling method to use depends on many factors, such as the restrictions of specimen geometry, the type of structural information desired and the microscopic techniques to be employed. This summary will highlight some recent technical innovations and novel applications of cryopreservation of biological specimens to study ultrastructure, chemical composition, and dynamic processes.For cryofixation to give realistic preservation of structural details, the specimen must be rapidly brought into intimate contact with the coolant and the contact must be maintained throughout the critical stages of the cooling process. During the last decade, four cooling methods have become prominent because they produce excellent preservation without cryoprotectants, are commercially available and are relatively simple to use:plunge cooling, jet cooling, slam cooling, and high-pressure cooling.Plunge cooling, the most commonly used method for cryofixation, is simply the immersion of a specimen into a liquid coolant usually held near its melting point.