257066 The Effects of Intermolecular Interactions On Transmission of Plasmid DNA Through Ultrafiltration Membranes
The effects of intermolecular interactions on transmission of plasmid DNA through ultrafiltration membranes.
There is considerable interest in developing new methods for the purification of plasmid DNA for use as gene therapy agents or DNA-based vaccines. Several previous studies have demonstrated that plasmid transmission through an ultrafiltration membrane occurs by elongation of the plasmid in the converging flow field into the membrane pore at large filtration flux. However, these data were obtained with very dilute DNA solutions, i.e., under conditions where there were no intermolecular interactions between the DNA molecules. The objective of this work was to examine the effect of DNA – DNA interactions during ultrafiltration processes.
Experimental data were obtained with plasmids from 3.0 and 16.9 kbp (kilo base pairs) in size using Omega (modified polyethersulfone) ultrafiltration membranes. In contrast to the behavior with dilute solutions, the transmission of the plasmid DNA showed a distinct maximum at intermediate values of the filtrate flux, with the sieving coefficient decreasing to near zero at very high values of the flux. The critical filtrate flux for plasmid transmission appears to remain independent of plasmid size, consistent with results for dilute plasmid solutions. However, the maximum plasmid transmission was a strong function of the plasmid size, with the extent of plasmid transmission decreasing with increasing plasmid size. The experimental results were analyzed using available models for concentrated polymer solutions to provide additional insights into the effects of intermolecular interactions on plasmid elongation during ultrafiltration. These results provide new insights into the factors governing the ultrafiltration of plasmid DNA solutions.