Methodology is proposed to develop efficient and general procedures for the synthesis of nontoxic quantum dots, and for conjugating, or 'tagging'these dots to proteins, for the purpose of enhancing and improving biomedical imaging techniques. It is generally agreed that quantum dots (QDs) offer many advantages over organic dyes or gold nanocrystals in applications of protein tagging and other imaging technologies. Approaches to disease detection via imaging techniques require novel methods of QD conjugation to biomolecules. The proposed project involves a collaboration between Principal Investigators with expertise in organic synthesis (to prepare tailored dendrons for use in passivating and stabilizing nanocrystals), nanocrystal synthesis (to design and synthesize nontoxic nanocrystals with tunable electronic and spectroscopic properties), physical biochemistry (to demonstrate the feasibility of attachment of the designed nanocrystals to a representative protein that is involved in cell signaling), and single molecule spectroscopy (to demonstrate the ability of the designed systems to aid in the study of protein folding). The team will develop techniques to characterize previously unrealized structural and/or biological properties of nanocrystal bioconjugates in-vitro, and subsequently in-vivo. Accomplishment of the aims of this project is expected to demonstrate the advantages of bionanotechnology as a new avenue of diagnostic and therapeutic treatment. This exploratory project has 3 specific aims: 1. Synthesize, characterize, and optimize appropriately functionalized dendrons for ligation to nontoxic Mn-doped ZnSe (Mn:ZnSe d-dots) and InAs/InP/ZnS core/shell/shell near infrared (NIR) QDs. 2. Explore solid-phase synthesis strategies to prepare Mn:ZnSe d-dots that are covalently attached to polymer resins. Derivatize the quantum dots for water solubility using methoxyethylamine-capped dendrimers. 3. Functionalize the monovalent d-dots for protein conjugation via four linkers that will provide maximum potential in a wide variety of protein applications: nitrilotriacetic acid (NTA), N-hydroxysuccinimide (NHS), maleimide, and acyl hydrazide. Conjugate the d-dots with representative proteins, purify, and characterize chemically and spectroscopically.
Organic dyes have been used for years in biomedical imaging applications, but they suffer from a number of limitations, many of which can be overcome by using nanometer-sized crystals (nanocrystals, also known as quantum dots). Past efforts in this area have several drawbacks, including toxicity from the heavy metal components of commercially available nanocrystalline materials, methods for the synthesis of nontoxic quantum dots, and inefficient methods for coupling quantum dots to biomolecules such as proteins. The University of Arkansas team directing this project aims to overcome these limitations, and is uniquely qualified to do so, since it comprises Principle Investigators with expertise in every aspect of the synthesis and evaluation of protein-coupled nontoxic quantum dots.
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