A novel approach to surface specific biomolecules: In vitro selection on surfaces (ISOS) S. Sweeney, A. Mahady, S. Lohse, D. Shah, J. A. Berglund, J. Hutchison Department of Chemistry and Institute of Molecular Biology, University of Oregon, Eugene, OR Vision and Goals In Vitro Selection on Surfaces (ISOS) General: Can be used for any planar substrate (organic, inorganic, semiconductor), and any biopolymer (RNA, DNA, peptides). Specific: Design allows for precise selection on the order of crystal orientation. ISOS opens up opportunities in sensor design, surface science, medicine, and other applications in materials science and nanotechnology. Seeded Growth Using RNA Aptamers To develop an approach for the preparation of well-defined anisotropic gold nanoparticles in a green fashion using RNA aptamers selected via in vitro selection on surfaces – ISOS. Direct replacement of CTAB with selected RNA aptamers Development of in vitro RNA selection techniques for inorganic surfaces. Use of these techniques for the selection of RNA aptamers with a high affinity and selectivity for the Au (111) surface. Preparation of shape-controlled gold nanoparticles using Au (111) specific RNA. Growth Solution 100µl Step 1 Step 2 Step 3 1µl Seed E03 in each growth solution TEM Grid Bio-Inspired Nanotechnology Almost every living creature exploits biomineralization for the formation of inorganic structural materials with exquisite control down to the nanoscale. Formation under ambient conditions and neutral pH in water! Examples include diatoms (left), sponges, teeth and bones. ISOS In Action: Evaporated Gold Summary of ISOS Conditions RNA Selection Using ISOS Cyclotella stelligera http://www.indiana.edu/~diatom/cystelli.jpg Why not use naturally diverse biomolecules such as RNA, DNA or peptides to form well-defined technologically relevant nanomaterials? Anisotropic Nanoparticles Unique optical properties make them attractive for many applications – sensors, therapeutics, SERS substrates. Gold Binding RNA Characterization Secondary Structure Conclusions / Future Work Developed novel methods for identifying and characterizing RNA molecules that bind to planar substrates. Selected RNAs that bind to evaporated gold surfaces. Have begun screening these RNAs for nanocrystal formation. Have begun systematic screening of peptides for different gold surfaces using ISOS. Will perform RNA selection on gold nanorods and nanoparticles to act as “templates” in nanocrystal formation reactions. Synthesis (Seeded & Photochemical) 2D Plasmon Resonance -Nonspecific surfactant interactions lead to mixed populations of nanocrystals. -Surfactant is cytotoxic – RNA could be used a a greener, more specific directing agent. RNA Selection Criteria Initial Hypothesis RNAs can be selected with high affinity for a given crystal face of gold and can be used to preferentially affect the rates of growth of crystal faces during nanoparticle preparation, leading to nanoparticles with defined shapes. Acknowledgements Gold Dot Assay Competition Assays Hutchison Lab, Berglund Lab, UO Student Shop, Prof. Ken Doxsee, AFRL for Funding Effect of polyA on binding Effect of polyU on binding Selection Guidelines 1. Careful control over Au crystal face being selected for. - Au (111) vs. Au (100) vs. Au (110). 2. Control over surface concentration of gold atoms. - Important for increasing stringency during selection. 3. General approach that allows for selection on any planar substrate - Au (111) vapor deposited, Au (100) grown as single crystal. - Allows for flexibility. "This material is based on research sponsored by Air Force Research Laboratory under  agreement number FA8650-05-1-5041. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of Air Force Research Laboratory or the U.S. Government.”