Survival of mammalian cells under high vacuum condition for ion bombardment

An ion beam has been used to irradiate various organisms and its effects have been studied. Because of the poor tolerance that mammalian cells have for vacuum, such studies have not been carried out on living mammalian cells until now. However, this work is important both for elucidating the mechanism of mutation in response to low-energy ions and in exploring possible new applications of ion beam technology. The current paper describes an investigation of the survival of mammalian cells (the A(L) cell line) in a high-vacuum chamber in preparation for ion bombardment studies. The ion beam facility is described and the actual vacuum profile that the cells endured in the target chamber is reported. Cells were damaged immediately following vacuum exposure; the injury was characterized by alteration of the membrane permeability, loss of firm adhesion to the dish, and increased fragility. Three cryoprotective agents were tested (glycerol, propylene glycol, and trehalose) and of these, glycerol showed the highest potency for protecting cells against vacuum stress. This was revealed by an increase in the cell survival level from <1 to >10% with a glycerol concentration of 15 and 20%. Two glycerol-based protocols were investigated (freezing-vacuum vs. non-freezing-vacuum), but there was no significant difference (P > 0.1) in their ability to improve cell survival, the values being 10.31 +/- 4.5 and 12.7 +/- 3.37%, respectively with 20% glycerol concentration. These cells had a normal growth capability, and also retained integrity of the cell surface antigen CD59. These initial experiments indicate that mammalian cells can withstand vacuum to the degree that is needed to study the effect of the ion beam. In addition to the improvements made in this study, other factors are discussed that may increase the survival of mammalian cells exposed to a vacuum in future studies. (C) 2004 Elsevier Inc. All rights reserved.