Lyophilization as an alternative method for preservation of some continuous cell cultures

This work is a trial to provide lyophilization as a simple method for preservation of continuous cell lines instead of the freezing process in liquid nitrogen. Comparative evaluation of lyophilized African green monkey kidney (VERO), baby hamster kidney (BHK) and Madin Darby bovine kidney (MDBK) cell lines and those preserved by freezing in liquid nitrogen was carried out. Such evaluation on 6 months intervals revealed that both of lyophilized cell cultures showed delayed cell adhesion to the culture surface extending to 2-3 days post culturing while propagated and frozen cells adhered to the culture surface within few hours. However there were an increased number of adhered viable cells in case of loading of cells using trehalose and sucrose on days post culturing. In addition cultured lyophilized cells which loaded by trehalose or sucrose exhibited abnormal shape (showing cell rounding) in comparison to the other cultures. Also cell dispersing of confluent sheets of cultured lyophilized cells were found to take longer time (one hour) than that required to other cultures (few minutes) even on using EDTA and incubation at 37 °C. Further studies are needed to investigate the biological behavior or cell changes which may be occurred through the lyophilization process in addition to study the susceptibility of such cells to virus infection. Depending on these facts it could be said that lyophilization is not valid for VERO, BHK and MDBK which usually used for preparation of virus vaccine in stationary or roller systems. It also could be suggested that preservation of cell lines by lyophilization may be of value in cell culturing suspension system.