Assembly Of Near-IR Fluorescent Nanostructures With Emergent Properties

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With this award from the Organic and Macromolecular Chemistry Program, Prof. Bradley Smith plans to build on his recent discovery of squaraine-rotaxanes as very bright and extremely stable fluorescent near-infrared (NIR) dyes. Next-generation self-assembly methods will be developed to produce squaraine-macrocycle inclusion complexes in quantitative yields. The methods will be employed to construct elaborate NIR fluorescent nanostructures that have emergent properties. That is, the photophysical properties, chemical stabilities, and molecular recognition properties of the assembled nanostructures are superior to the individual building blocks. An attractive feature of this self-assembly strategy is its generality, which means that the building blocks (macrocycles and squaraine dyes) can be combined with almost any type of targeting ligand to rapidly produce fluorescent imaging probes that will have broad impact in materials science, biomedical science and nanotechnology. They will enable scientists to conduct photonic experiments that were previously impossible. One practical aim of the project is to utilize squaraine-rotaxanes as core scaffolds to construct NIR fluorescent dendrimers, which will have many applications, especially in biomedical imaging and diagnostic processes that employ Fluorescence Resonance Energy Transfer (FRET). A specific goal is to provide novel fluorescent reagents that enable new approaches to studying the complex process of gene delivery into cells using cationic dendrimers as transfection agents. Another practical aim is to produce NIR fluorescent imaging probes that can image many types of cancer cells; thus, they will aid studies of tumor biology, allow cancer detection in small animal models, and perhaps eventually facilitate fluorescence guided cancer surgery. The core training of research students will be in supramolecular photochemistry, but the applied aspects of the projects will teach them how to translate their discoveries into practical outcomes. The final practical aim of the proposal is to upgrade "Organic Structure Elucidation", a free internet workbook that already serves several thousands of chemistry students around the world, many of them in poorly equipped schools or under-developed countries.