Abstract
Our study aims at a better control and understanding of the transfer of a complex [DNA supercoiled plasmid – dodecyltrimethylammonium surfactant] layer from a liquid–vapour water interface onto a silicon surface without any additional cross-linker. The production of the complexed layer and its transfer from the aqueous subphase to the substrate is achieved with a Langmuir–Blodgett device. The substrate consists of a reconstructed boron doped silicon substrate with a nanometer-scale roughness. Using X-ray photoelectron spectroscopy and atomic force microscopy measurements, it is shown that the DNA complexes are stretched in a disorderly manner throughout a 2–4 nm high net-like structure. This architecture is composed of tilted cationic surfactant molecules bound electrostatically to DNA, which exhibits a characteristic network arrangement with a measured average fiber diameter of about 45 ± 15 nm covering the entire surface. The mechanism of transfer of this layer onto the planar surface of the semi-conductor and the parameters of the process are analysed and illustrated by atomic force microscopy snapshots. The molecular layer exhibits the typical characteristics of a spinodal decomposition pattern or dewetting features. Plasmid molecules appear like long flattened fibers covering the surface, forming holes of various shapes and areas. The cluster–cluster aggregation of the complex structure gets very much denser on the substrate edge. The supercoiled DNA plasmids undergo conformational changes and a high degree of condensation and aggregation is observed. Perspectives and potential applications are considered.
Highlights
This work aims at developing a method for depositing onto a planar conductive surface a well-characterized monolayer of self-assembled desoxyribonucleic acid (DNA) supercoiled plasmids bound to cationic surfactant molecules
Less than 8% ± 1 of the DNA population are in the circular conformation according to our measurements based on 1% agarose gel electrophoresis in TAE buffer at 6.7 V cmÀ1 for 7 min and 5.0 V cmÀ1 for 68 min
The ratio of positive charges due to tetradecylmethyl ammonium bromide (TDAB) cations (250 mL, 10À5 M) over the total negative electrical charges due to the DNA (27 lL, 4 · 10À8 M) smeared over the Langmuir film is a key parameter in our experiments
Summary
This work aims at developing a method for depositing onto a planar conductive surface a well-characterized monolayer of self-assembled desoxyribonucleic acid (DNA) supercoiled plasmids bound to cationic surfactant molecules (tetradecyltrimethylammonium bromide, TDAB or C14TAB). Many contributions have focused on the formation of complexes involving DNA These systems have been extensively studied even though the mechanism of formation is not completely understood [5]. In such experiments, the DNA layers must be characterized, in particular it is essential to understand the underlying self-assembly processes resulting in the formation of the supramolecular structures under investigation. Trying to understand the effect of 2D nanoscale supramolecular organization and patterning when mixing DNA with a cationic amphiphile monolayer in complex Langmuir–Blodgett (LB) films is a more recent topic. Learning how to control such biomolecular assembly processes and application of these principles to fabricate new functional nanostructures and nanostructured materials can be an effective approach in nanoscale science, advanced materials research and molecular nanotechnology
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
