The Structureand Application of Nucleic Acid-Surfactant Films for Transfection in Human Cells
S. Gajria,*S.L. Perry, J. Ni, J. Weinstein, D. Schaeffer, M.V. Tirrell†
*Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara CA 93106,†Department of Bioengineering, University of California at Berkeley, Berkeley, CA 94720
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Summary: Here we present work on the use of layered nucleic acid-surfactant films for gene transfection in human cells.
The use of cationic surfactants for gene delivery has continued to attract interest in the 20 years since they were first used to effect transfection.1 Nucleic acid (NA)-surfactant complexes (lipoplexes) form via electrostatic interactions between the negatively charged backbone of the NAs and the cationic surfactant headgroup. While the majority of effortsforgene transfectionand gene silencing have focused on lipoplexes in solution, there are tremendous benefits which can be realized through the use of solid lipoplex films for targeted local delivery of transfection agents.2
Initial work on the structure of a model NA-surfactant film composed of DNA and dimethyldidodecylammonium bromide (DDAB) demonstrated that the film has a lamellar structure composed of alternating layers of DNA and DDAB. More interestingly, the structure of the film undergoes a reversible transition from double-stranded DNA and surfactant bilayers in the dry state to single-stranded DNA and surfactant monolayers upon hydration (Figure 1). These structural changes occur quickly and provide added stability for long-term storage of the films and improved resistance against nuclease degradation.3-5
While the cytotoxicity of DDAB was too high to allow for its use in transfection studies, similar structural transitions have been observed in films composed of less cytotoxic surfactants based on glutamic acid. In addition to the lamellar structure observed for DDAB, these changes were observed for films which self assemble into inverted hexagonal and cubic structures. The variety of curvature observed in these various films provides an interesting basis from which to explore the structural relevance of various lipoplex features on cytotoxicity and transfection efficiency in human cells. These films have been used successfully to stably transfect HeLa cells with green fluorescent protein (GFP) and further optimization of these results is ongoing.
Figure. 1. Three known structural states of a DNA-DDAB film in dry, wet, and heated wet states.3
(1)Felgner, P. L.; Gadek, T. R.; Holm, M.; Roman, R.; Chan, H. W.; Wenz, M.; Northrop, J. P.; Ringold, G. M.; Danielsen, M. P Natl Acad Sci USA1987, 84, 7413.
(2)Gajria, S.; Neumann, T.; Tirrell, M. V. Wiley Interdisciplinary Reviews: Nanomedicine and Nanobiotechnology, (submitted).
(3)Neumann, T.; Gajria, S.; Bouxsein, N. F.; Jaeger, L.; Tirrell, M. J Am Chem Soc2010, 132, 7025.
(4)Neumann, T.; Gajria, S.; Tirrell, M.; Jaeger, L. J Am Chem Soc2009, 131, 3440.
(5)Smitthipong, W.; Neumann, T.; Gajria, S.; Li, Y.; Chworos, A.; Jaeger, L.; Tirrell, M. Biomacromolecules2009, 10, 221.