7 - Cryopreservation

Summary

It is quite often the case that particular lines of cells used by a laboratory are not required in culture continuously, but it can be important to have ready access to fresh stocks when required. Cell lines can be purchased direct from national collections but this takes time and could be expensive depending on the number purchased annually. Supplies from fellow researchers in other laboratories may not be readily available and may be of unknown quality. Most laboratories involved in cell culture establish cell banks of their own in liquid nitrogen refrigerators providing instant access when required.

Establishing a cell bank

A cell bank is very simple to set up and requires the following:

1. a liquid nitrogen refrigerator or −150 °C ultra-low freezer. Liquid nitrogen refrigerators come in varying sizes from small units holding cryotubes to very large units holding many thousands of tubes (see Chapter 2 for details of suppliers);

2. storage racks and boxes in which to place the tubes;

3. a regular source of liquid nitrogen;

4. insulated gloves and a visor;

5. a supply of cryotubes. These are thick-walled screw-capped polypropylene tubes, specifically designed for liquid nitrogen storage and available in various capacities from 1.0 ml upwards. Never use any other type of plastic tube for this purpose;

6. a comprehensive and accurate record system for logging every cell line stored in it. This can be either computer based (with or without hard copies) or handwritten in folders.