Supramolecular Ultrathin Film Strategies for DNA Assemblies: Substrates for Optobioelectronics, Gene Therapy, and Microa
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Supramolecular Ultrathin Film Strategies for DNA Assemblies: Substrates for Optobioelectronics, Gene Therapy, and Microarrays Rigoberto C. Advincula*, Yingfan Wang, Mi-Kyoung Park, Gautam Bhatia, Seth Stepleton, Cara Monroe, Iman Shelton, Wally Blanton, Xiaowu Fan Department of Chemistry, University of Alabama at Birmingham Birmingham, AL 35294-1240 ABSTRACT We describe our strategies and results in the preparation of supramolecularly ordered ultrathin films of DNA assemblies using the layer-by-layer (LbL) alternate polyelectrolyte adsorption technique. The properties of DNA are intimately associated with their polyelectrolyte behavior in solution. Deposition at interfaces is governed by conformation, orientation, and charge density of these biomolecules in relation to the physisorption phenomena in oppositely charged surfaces. Thus, controlling the nature of surfaces (polymer charge density, ionic strength, other non-covalent interactions, etc.) is important in modifying the adsorption phenomena. In this work, differences in adsorption and incorporation of DNA with dyes, linear polymers and dendrimers are highlighted. A number of surface sensitive spectroscopic and microscopic techniques were used to probe the adsorption and multilayer assembly phenomena, e.g. surface plasmon resonance spectroscopy (SPS), AFM, quartz crystal microbalance (QCM) and ellipsometry. These studies are important for future applications such as the use of polycations as non-viral gene transfection vectors for drug-delivery and DNA adsorption on microarray surfaces. By combining with the alternate assembly of azobenzene and phthalocyanine dyes, we have been able to prepare optobiolelectronic substrates where the phenomena of irradiation and electrochemistry can be used to probe the ordering and response of these films. INTRODUCTION DNA (deoxyribonucleic acid) is a very important biological material because of its function as life’s information storage system for protein synthesis, i.e. a basic function in the heredity of life. Lately, the treatment of human diseases through gene therapy has resulted in increasing use of nucleotide-based drugs in the medical field [1]. DNA as a polynucleotide, is also an interesting anionic polyelectrolyte with its unique double helix structure. On the basis of H-bonding properties of the base pairs (hybridization), oligonucleotide probes have also been designed to detect tumor genes in microarrays or photolithographically patterned "DNA chips"[2]. Various biosensors have also been proposed [3]. Also, the one-dimensionally stacked -electron array along the double helical structure allowed the study of long-range photoinduced electron transfer interactions in oriented DNA for fundamental studies [4]. Thus, a number of potential applications of these systems has been reported for drug delivery, gene therapy agents, microarrays, and biosensors The alternate polyelectrolyte deposition (APD) or layer-by-layer (LbL) self-assembly method is a relatively new technique to prepare ultrathin films with different nanoar
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