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The Assembly of DNA Amphiphiles at Liquid Crystal-Aqueous Interface.

ABSTRACT: In this article, we synthesized a type of DNA amphiphiles (called DNA-lipids) and systematically studied its assembly behavior at the liquid crystal (LC)-aqueous interface. It turned out that the pure DNA-lipids at various concentrations cannot trigger the optical transition of liquid crystals from planar anchoring to homeotropic anchoring at the liquid crystal-aqueous interface. The co-assembly of DNA-lipid and l-dilauroyl phosphatidylcholine (l-DLPC) indicated that the DLPC assembled all over the LC-aqueous interface, and DNA-lipids prefer to couple with LC in certain areas, particularly in polarized and fluorescent image, forming micron sized net-like structures. The addition of DNA complementary to DNA-lipids forming double stranded DNA-lipids caused de-assembly of DNA-lipids from LC-aqueous interface, resulting in the disappearance of net-like structures, which can be visualized through polarized microscope. The optical changes combined with DNA unique designable property and specific interaction with wide range of target molecules, the DNA-lipids decorated LC-aqueous interface would provide a new platform for biological sensing and diagnosis.

SUBMITTER: Zhou J

PROVIDER: S-EPMC5302708 | biostudies-other | 2016 Dec

REPOSITORIES: biostudies-other

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The Assembly of DNA Amphiphiles at Liquid Crystal-Aqueous Interface.

Zhou Jingsheng J Dong Yuanchen Y Zhang Yiyang Y Liu Dongsheng D Yang Zhongqiang Z

Nanomaterials (Basel, Switzerland) 20161201 12

In this article, we synthesized a type of DNA amphiphiles (called DNA-lipids) and systematically studied its assembly behavior at the liquid crystal (LC)-aqueous interface. It turned out that the pure DNA-lipids at various concentrations cannot trigger the optical transition of liquid crystals from planar anchoring to homeotropic anchoring at the liquid crystal-aqueous interface. The co-assembly of DNA-lipid and l-dilauroyl phosphatidylcholine (l-DLPC) indicated that the DLPC assembled all over ...[more]

PMID: 28335357

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Project description:Quantitatively understanding the self-assembly of amphiphilic macromolecules at liquid-liquid interfaces is a fundamental scientific concern due to its relevance to a broad range of applications including bottom-up nanopatterning, protein encapsulation, oil recovery, drug delivery, and other technologies. Elucidating the mechanisms that drive assembly of amphiphilic macromolecules at liquid-liquid interfaces is challenging due to the combination of hydrophobic, hydrophilic, and Coulomb interactions, which require consideration of the dielectric mismatch, solvation effects, ionic correlations, and entropic factors. Here we investigate the self-assembly of a model block copolymer with various charge fractions at the chloroform-water interface. We analyze the adsorption and conformation of poly(styrene)-block-poly(2-vinylpyridine) (PS-b-P2VP) and of the homopolymer poly(2-vinylpyridine) (P2VP) with varying charge fraction, which is controlled via a quaternization reaction and distributed randomly along the backbone. Interfacial tension measurements show that the polymer adsorption increases only marginally at low charge fractions (<5%) but increases more significantly at higher charge fractions for the copolymer, while the corresponding randomly charged P2VP homopolymer analogues display much more sensitivity to the presence of charged groups. Molecular dynamics (MD) simulations of the experimental systems reveal that the diblock copolymer (PS-b-P2VP) interfacial activity could be mediated by the formation of a rich set of complex interfacial copolymer aggregates. Circular domains to elongated stripes are observed in the simulations at the water-chloroform interface as the charge fraction increases. These structures are shown to resemble the spherical and cylindrical helicoid structures observed in bulk chloroform as the charge fraction increases. The self-assembly of charge-containing copolymers is found to be driven by the association of the charged component in the hydrophilic block, with the hydrophobic segments extending away from the hydrophilic cores into the chloroform phase.

Project description:ConspectusThe liquid-microjet technique combined with soft X-ray photoelectron spectroscopy (PES) has become an exceptionally powerful experimental tool to investigate the electronic structure of liquid water and nonaqueous solvents and solutes, including nanoparticle (NP) suspensions, since its first implementation at the BESSY II synchrotron radiation facility 20 years ago. This Account focuses on NPs dispersed in water, offering a unique opportunity to access the solid-electrolyte interface for identifying interfacial species by their characteristic photoelectron spectral fingerprints. Generally, the applicability of PES to a solid-water interface is hampered due to the small mean free path of the photoelectrons in solution. Several approaches have been developed for the electrode-water system and will be reviewed briefly. The situation is different for the NP-water system. Our experiments imply that the transition-metal oxide (TMO) NPs used in our studies reside close enough to the solution-vacuum interface that electrons emitted from the NP-solution interface (and from the NP interior) can be detected.We were specifically exploring aqueous-phase TMO NPs that have a high potential for (photo)electrocatalytic applications, e.g., for solar fuel generation. The central question we address here is how H2O molecules interact with the respective TMO NP surface. Liquid-microjet PES experiments, performed from hematite (α-Fe2O3, iron(III) oxide) and anatase (TiO2, titanium(IV) oxide) NPs dispersed in aqueous solutions, exhibit sufficient sensitity to distinguish between free bulk-solution water molecules and those adsorbed at the NP surface. Moreover, hydroxyl species resulting from dissociative water adsorption can be identified in the photoemission spectra. An important aspect is that in the NP(aq) system the TMO surface is in contact with a true extended bulk electrolyte solution rather than with a few monolayers of water, as is the case in experiments using single-crystal samples. This has a decisive effect on the interfacial processes that can occur since NP-water interactions can be uniquely investigated as a function of pH and provides an environment allowing for unhindered proton migration. Our studies confirm that water is dissociatively adsorbed at the hematite surface and molecularly adsorbed at the TiO2 NP surface at low pH. In contrast, at near-basic pH the water interaction is dissociative at the TiO2 NP surface.The liquid-microjet measurements presented here also highlight the multiple aspects of photoemission necessary for a full characterization of TMO nanoparticle surfaces in aqueous environments. For instance, we exploit the ability to increase species-specific electron signals via resonant photoemission, so-called partial electron yield X-ray absorption (PEY-XA) spectra, and from valence photoelectron and resonant Auger-electron spectra. We also address the potential of these resonance processes and the associated ultrafast electronic relaxations for determining charge transfer or electron delocalization times, e.g., from Fe3+ located at the hematite nanoparticle interface into the aqueous-solution environment.

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The Assembly of DNA Amphiphiles at Liquid Crystal-Aqueous Interface.

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The Assembly of DNA Amphiphiles at Liquid Crystal-Aqueous Interface.

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