We have investigated the interaction of DNA with a highly ordered functional ultrathin layer of cationic surfactant, dioctadecyl ammonium bromide (DOAB). The ultrathin film of DOAB is fabricated by Langmuir-Blodgett technique onto the pretreated quartz crystal wafers. The solution of DNA in phosphate buffer saline (PBS) is injected through a flow cell in a quartz crystal microbalance (QCM) loaded with the functional ultrathin film. The QCM data indicate a slower kinetics (time constant？？=？？162.2 seconds) for the adsorption of DNA on DOAB layer as compared to PBS on DOAB. The surface morphology of the aggregation of DNA over the DOAB layer is investigated using atomic force microscope (AFM). The AFM image indicates the trapping of DNA over the DOAB layer. Such trapping of DNA can be potentially employed in the field of genomics. 1. Introduction The molecular interactions in the biological world govern numerous vital activities essential for physiological processes [1]. The field of biophysics relies on the investigation of molecular interactions at the relevant physiological conditions. The field of interaction of DNA with the biological relevant materials is matured. Understanding the molecular interactions of the biological relevant molecules is essential not only for the design of novel drugs but also devices for probing the systems rapidly and accurately. There are molecular specific interactions like antibody-antigen which work on the principle of lock-key mechanism. Such molecular specific interactions are potentially employed for the development of sensors [2, 3]. There are numerous studies on the interaction of DNA with proteins, lipids membranes, and cationic surfactants [4–7]. The phosphate backbone of the DNA strand acquires the negative charge in the aqueous environment. Such charged state of DNA can form complexes with the cationic surfactants due to the static charge-charge interaction. Due to complex formation, the DNA strands condense to form very small particles. These complexes may be employed for nonvirial gene delivery vehicles in vaccines and gene therapy [8–11]. The efficiency and the sensitivity of the functional material increases manifold when the material is spread into thin films. This is due to gain in surface-to-volume ratio when the bulk material is spread to form thin films [12, 13]. In this paper, we report our study on the interaction of DNA with the ultrathin film of a cationic surfactant using a quartz crystal microbalance (QCM) and atomic force microscope (AFM). A highly organized single layer of Langmuir-Blodgett (LB)
References
[1]
B. Alberts, D. Bray, J. Lewis, M. Raff, K. Roberts, and J. D. Watson, Molecular Biology of the Cell, Garland, New York, NY, USA, 1983.
[2]
B. Byrne, E. Stack, N. Gilmartin, and R. O'Kennedy, “Antibody-based sensors: principles, problems and potential for detection of pathogens and associated toxins,” Sensors, vol. 9, pp. 4407–4445, 2009.
[3]
M. S. Ozdemir, M. Marczak, H. Bohets et al., “A label-free potentiometric sensor principle for the detection of antibody-antigen interactions,” Analytical Chemistry, vol. 85, pp. 4770–4776, 2013.
[4]
D.-M. Zhu and R. K. Evans, “Molecular mechanism and thermodynamics study of plasmid DNA and cationic surfactants interactions,” Langmuir, vol. 22, no. 8, pp. 3735–3743, 2006.
[5]
K. Hayakawa, J. P. Santerre, and J. C. T. Kwak, “The binding of cationic surfactants by DNA,” Biophysical Chemistry, vol. 17, no. 3, pp. 175–181, 1983.
[6]
M. Slutsky and L. A. Mirny, “Kinetics of protein-DNA interaction: facilitated target location in sequence-dependent potential,” Biophysical Journal, vol. 87, no. 6, pp. 4021–4035, 2004.
[7]
C. R. Safinya, “Structures of lipid-DNA complexes: supramolecular assembly and gene delivery,” Current Opinion in Structural Biology, vol. 11, pp. 440–448, 2001.
[8]
E. Dauty, J.-S. Remy, T. Blessing, and J.-P. Behr, “Dimerizable cationic detergents with a low cmc condense plasmid DNA into nanometric particles and transfect cells in culture,” Journal of the American Chemical Society, vol. 123, no. 38, pp. 9227–9234, 2001.
[9]
V. Vijayanathan, T. Thomas, and T. J. Thomas, “DNA nanoparticles and development of DNA delivery vehicles for gene therapy,” Biochemistry, vol. 41, no. 48, pp. 14085–14094, 2002.
[10]
P. C. Bell, M. Bergsma, I. P. Dolbnya et al., “Transfection mediated by gemini surfactants: engineered escape from the endosomal compartment,” Journal of the American Chemical Society, vol. 125, no. 6, pp. 1551–1558, 2003.
[11]
I. van der Woude, A. Wagenaar, A. A. P. Meekel et al., “Novel pyridinium surfactants for efficient, nontoxic in vitro gene delivery,” Proceedings of the National Academy of Sciences of the United States of America, vol. 94, no. 4, pp. 1160–1165, 1997.
[12]
A. Ulman, “Formation and structure of self-assembled monolayers,” Chemical Reviews, vol. 96, pp. 1533–1554, 1996.
[13]
A. Zribi and J. Fortin, Eds., Functional Thin Films and Nanostructures for Sensor, Springer, New York, NY, USA, 2009.
[14]
G. L. Gaines Jr., Insoluble Monolayers at Liquid-Gas Interfaces, Wiley-Interscience, New York, NY, USA, 1966.
[15]
R. K. Gupta and V. Manjuladevi, Molecular Interactions at Interfaces, Intech, Rijeka, Croatia, 2012.
[16]
R. K. Gupta and V. Manjuladevi, “Liquid crystals at interfaces,” Israel Journal of Chemistry, vol. 52, pp. 809–819, 2012.
[17]
H. M？hwald, “Phospholipid monolayers,” in Handbook of Biological Physics, R. Lipowski and E. Sackmann, Eds., Elsevier, Amsterdam, The Netherlands, 1995.
[18]
G. Sauerbrey, “Verwendung von schwingquarzen zur w？gung dünner schichten und zur mikrow？gung,” Zeitschrift Für Physik A, vol. 155, p. 206, 1959.
