Browsing by Author "Lin, Hsien-Kuang"

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Thermally-induced order-order transition of DNA-cationic surfactant complexes
(2006-08-29)
Hsu, Wei-Long
;
Li, Yen-Cheng
;
Chen, Hsin-Lung
;
Liou, Willisa
;
Jeng, U-Ser
Polyanionic DNA interacts with cationic amphiphiles to form electrostatic complexes exhibiting rich self-assembled structures. This type of complex has been considered as a nonviral carrier in gene therapy and as a template for nanostructure construction. Here we report a thermally-induced phase transition of the complexes of DNA with the mixtures of a cationic surfactant, dodecyltrimethyl bromide (DTAB), and a neutral lipid, dioleoylphosphatidylethanolamine (DOPE), in fully hydrated state. An order-order transition between a multilamellar (L-alpha(c)) phase and an inverted hexagonal (H-II(c)) phase was found to occur with the transition temperature adjustable by the DTAB-to-DNA base pair molar ratio (x) and DOPE-to-DTAB molar ratio (m). The stability of the L-alpha(c) phase was enhanced at lower m and x, as the L-alpha(c)-to-H-II(c) transition temperature increased with the decreases of these two parameters. The suppression of L-alpha(c)-to-H-II(c) transition at lower x was attributed to the lower entropic gain from the counterion release due to the presence of uncomplexed DNA in the bulk solution.
Two-dimensional densely packed DNA nanostructure derived from DNA complexation with a low-generation poly(amidoamine) dendrimer
(2007-01-30)
Su, Chun-Jen
;
Liu, Yi-Chun
;
Chen, Hsin-Lung
;
Li, Yen-Cheng
;
Lin, Hsien-Kuang
One of the keys for using deoxyribonucleic acid (DNA) as a nanomaterial relies on how the individual DNA chain can be aligned and how a multitude of DNA chains can be packed into ordered nanostructures. Here we present a simple method for constructing a 2-D densely packed DNA nanostructure using the electrostatic complex of DNA with a poly(amidoamine) (PAMAM) dendrimer of generation two. Ordered DNA arrays are formed by drop-casting an aqueous solution containing positively overcharged complexes onto mica followed by a prolonged incubation. During the incubation, the complexes tend to adsorb onto the negatively charged mica surface through electrostatic attraction. The rodlike complexes organize to form ordered arrays to increase the surface density of the adsorbed complexes and hence the attractive free energy of adsorption. The densely packed nanostructure obtained here is distinguished from the previously reported spheroid or toroid structure derived from DNA complexations with the higher-generation dendrimers.