Determination of protection from serum nuclease activity by DNA-polyelectrolyte complexes using an electrophoretic method

Polyelectrolyte complexes between cationic polymers and DNA have emerged as potential nonviral vectors for DNA delivery. For successful in vivo delive ry, methods for analyzing their ability to prevent digestion of the DNA pay load by serum nucleases are essential. We report here a simple assay to det ermine degradation of DNA in these complexes using standard electrophoretic techniques. The assay is based on a high pH buffer which can dissociate th e complexes under standard electrophoretic conditions. This assay can be us ed qualitatively to determine the time taken for degradation to occur. Alte rnatively, with a standard gel analysis program it can be used quantitative ly to investigate rates of DNA degradation from complexes in the presence o f serum nucleases, We have shown that it can distinguish between different formulations with the same polymer, and also to distinguish between the tim e taken to degradation and the rates of degradation of DNA in complexes for med with two structurally related, Linear polyamidoamine polymers. The assa y could also distinguish between the time to degradation using poly-L-lysin e complexes, although these were less well dissociated by the electrophores is buffer, and could not be analyzed quantitatively. This assay will be of value in investigating and developing polyelectrolyte formulations for pare nteral administration. (C) 2001 Academic Press.