One of the most useful techniques in biomedical and biological research is cryopreservation of mammalian cells. The variety of applications for which cultured mammalian cells are suited is virtually limitless. For this reason, one property that is taken advantage of by essentially every lab using cultured cells is their ability to be stored indefinitely at freezing temperatures. In fact, the fear of losing a cell line to contamination or incubator failure is frequently the impetus for making archival storage of cells the first order of business after receiving or generating a new cell line.
While there are numerous different protocols for freezing cells, all involve the use of a ‘freezing medium’ containing a cryoprotectant such as DMSO or glycerol. Once transferred from growth medium to freezing medium, the cells are then frozen at a controlled rate and stored in liquid nitrogen vapor or at -130°C in a mechanical deep freeze. Although freezing cells is a relatively simple procedure, problems arise when suitable freezers are not available. This had been a problem for our lab until we started using Bambanker, a freezing medium made by LYMPHOTEC, Inc. (Tokyo, Japan) and sold in the United States by Wako Chemicals USA, Inc. (Richmond, VA). The unique feature of Bambanker is that it permits cryopreservation of cells at -80°C, obviating the need for an additional and expensive ultra-low freezer.
Bambanker is a serum-free cryopreservation medium that is sold ready-to-use and can be kept in the refrigerator for up to two years. The protocol is very simple: 1) harvest cells and pellet them by centrifugation, 2) aspirate growth medium, 3) resuspend cells in 1 ml Bambanker (for 0.5 to 10 million cells), 4) transfer cell suspension to a cryovial and put it in a -80°C freezer. No controlled freezing is required.
The Wako website (http://www.wakousa. com) has an impressive list of cell lines that have been tested by freezing in Bambanker. The list includes mouse, rat, monkey, and human cells. I have used it for cryopreservation of several cell lines and recently thawed out a human lung adenocarcinoma cell line that had been frozen for 10 months at -80°C in Bambanker. The next morning, I washed off all nonadherent cells and counted them. Approximately 92% of the cells in the cryovial had attached and appeared to be quite happy.
So far, our lab has been very happy with Bambanker. It has eliminated the guesswork from freezing cells and has worked well for all cell lines we have tried, including both human and mouse lines. Bambanker sells for about $120 for a 120 ml bottle, which is quite a deal considering we can now use our existing -80°C freezers without worry of losing cell lines.
Michael Campa, Ph.D.
Assoc. Research Professor
Duke University Medical Center
Radiology