(251a) Structure and Application of Nucleic Acid-Surfactant Films for Transfection In Human Cells

Cationic surfactants have tremendous potential as non-viral transfection reagents. Although studies to date have not been able to achieve the levels of transfection attainable using viral vectors, they have significant advantages including ease of preparation and a lack of immunogenic and oncogenic concerns.  Nucleic acid (NA)-surfactant complexes (lipoplexes) form via electrostatic interactions between the negatively charged backbone of NAs and the cationic surfactant headgroup. While the majority of transfection studies have focused on the use of lipoplexes in solution, we present here the use of solid NA-surfactant films for localized transfection. This method has the potential to enable both higher transfection efficiencies compared to solution-based methods and allows for the controlled release of transfection agents via the use of a layered film structure.

Characterization of both lipoplexes and NA-surfactant films has demonstrated that a rich variety of self assembled structures can be achieved; including lamellar bilayers, inverted hexagonal rods, and bicontinuous cubic geometries.  In the case of DNA-surfactant films, however, the DNA has been observed to undergo a fast and reversible transition from double-stranded DNA to single-stranded DNA, coupled with a corresponding rearrangement of the surfactant layers upon drying. In films composed of DNA-dimethyldidodecylammonium bromide (DDAB) which forms a lamellar structure, the change from double-stranded to single-stranded DNA is accompanied by a change in the surfactant layers, transitioning from a bilayer structure to a monolayer structure.  The particular advantage of the change from double-stranded to single-stranded NA is that it allows for long-term storage of dry films in a biologically inactive state while also imparting an improved resistance against nuclease degradation.^1-3 When needed, these films can then be made biologically active once more by simple rehydration.

In addition to benefits associated with long-term storage, solid films have the potential to increase transfection efficiency by localizing the transfection agents (i.e. surfactant complexed DNA/siRNA) close to the cell surface. However, improvements in transfection efficiency due to increased local concentrations of the transfection agents must be balanced with the potential for commensurate increases in cytotoxicity from the complexing surfactant. Preliminary results have indicated the potential for very high levels of GFP transfection in HeLa cells (>90% cells transfected). Further experiments to validate these results, examine the delivery of siRNA for gene silencing, and extend the utility of these films to enable the controlled and/or sequential release of transfection agents are ongoing. 

References:

(1)   Neumann, T.; Gajria, S.; Bouxsein, N. F.; Jaeger, L.; Tirrell, M. J Am Chem Soc 2010, 132, 7025.

(2)   Neumann, T.; Gajria, S.; Tirrell, M.; Jaeger, L. J Am Chem Soc 2009, 131, 3440.

(3)   Smitthipong, W.; Neumann, T.; Gajria, S.; Li, Y.; Chworos, A.; Jaeger, L.; Tirrell, M. Biomacromolecules 2009, 10, 221.