Properties and Applications of Novel DNA-Based Surfactants
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Properties and Applications of Novel DNA-Based Surfactants Vesselin N. Paunov*, Chun Xu, Pietro Taylor, Mustafa Ersoz and Paul D.I. Fletcher Department of Chemistry, University of Hull, Hull, HU6 7RX, United Kingdom.
ABSTRACT We have designed a novel class of functional surfactants based on DNA and have explored their properties in relation to several possible applications. The DNA-surfactants consist of short chain DNA oligonucleotides covalently bound to a large hydrophobic group, which makes the DNA molecules amphiphilic. We demonstrate that these materials behave like common detergents and are surface-active at various fluid surfaces, e.g. air-water, oil-water interfaces, and lipid bilayers. We also show that once adsorbed the DNA-surfactants remain on the liquid surface upon hybridisation with a complementary DNA chain. We use complementary DNA-surfactants to functionalise fluid surfaces and to program the interactions between them based on WatsonCrick pairing. By selecting the appropriate DNA base sequences, the interaction between the fluid surfaces functionalised with DNA-surfactants can be programmed with a very high specificity. We have also developed a novel procedure for micro-patterning of solid surfaces with DNA by a microcontact printing with aqueous inks of DNA-surfactants which can be utilised for rapid fabrication of DNA assays and genetic biochips. INTRODUCTION We designed and used a new class of DNA-based surfactants,1 produced by covalent conjugation of a hydrophobic group to one of the ends of a short-chain DNA-oligonucleotide (Fig. 1A). This makes the modified DNA molecules amphiphilic and allows DNA chains to be adsorbed and orientated at fluid surfaces, including the air-water and oil-water interfaces, lipid bilayers (Fig. 1A) and also at the interface between water and a hydrophobic solid.1 Modified oligonucleotides containing hydrophobic ends-group have been synthesized previously,2-9 but have been looked only as “anti-sense” oligonucleotides, where the hydrophobic group may facilitate their penetration through cellular membranes2,3,7 and may serve to stabilise either duplex or triplex strand formation.4.5,9 Here we focus our attention on the possibility to use DNAsurfactants to functionalise fluid surfaces with DNA chains (Fig. 1B). We explore the surfactant properties of these materials at the air-water and oil-water interfaces and address the question related to the stability of their attachment at the liquid interface upon hybridisation with complementary DNA chains. We also use DNA-surfactants adsorbed at liquid surfaces to program the interactions between them based on complementary DNA-base sequences and Watson-Crick pairing (Fig. 1B). For successful hybridisation, the adsorbed DNA-surfactants should have an anti-parallel orientation which is realised only if they are adsorbed at opposite fluid interfaces. Similar strategy has been already used by Mirkin et al.10-13 for DNAfunctionalized solid particles. Recently, we have fabricated DNA-recognising liposomes by adsorption
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