Cell electroporation: estimation of the number of pores and their sizes.

In this paper the size and the apparent number of the pores induced in human red blood cells under the influence of a single electric field pulse have been estimated. The size of the pores was evaluated by two different approaches: (i) by measuring the kinetics of ascorbic acid entrance into the cells and (ii) by studying the protective action of mannitol and sucrose against colloid-osmotic lysis. The data presented here indicated that (i) the pores are small (0.2 < r < 0.5 nm); (ii) pores with a size such that the molecules of ascorbic acid and mannitol could penetrate through them appear when the field strength exceeds 2.5 kV/cm (tau i = 20 microseconds); (iii) with increasing pulse intensity there is an increase in both the radius of the pores and the number of cells permeable to mannitol or sucrose. It has been concluded that the presence of only one small (r approximately 0.3 nm) pore in the human erythrocyte is sufficient for a cell to be regarded as porated.