Papers Published

  1. Achyuthan, Komandoor E. and Lu, Liangde and Lopez, Gabriel P. and Whitten, David G., Supramolecular photochemical self-assemblies for fluorescence ``turn on'' and ``turn off'' assays for chem-bio-helices, PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES, vol. 5 no. 10 (2006), pp. 931--937 [doi] .
    (last updated on 2010/02/08)

    We describe the development of an optical sensing system for the high-throughput screening (HTS) of a broad range of biological molecules, whole cells, organisms and pathogens, and illustrate the technology applications by a hyaluronidase enzyme activity assay as a specific example. At the core of the technology described in this paper, is the exciton concept that is relevant to molecular aggregation. J-aggregates of cyanine dyes have a narrower, red-shifted absorption band compared to monomer. We demonstrate that self-assembly may be driven by the helicogenic nature of the cyanine dye, converting the linear polymers of hyaluronic acid or carboxymethyl cellulose into supramolecular helical assemblies. This self-assembly is accompanied by an intense, sharp, red-shifted J-aggregate fluorescence. We utilized this property to develop an assay for the enzyme hyaluronidase, based upon the concept of ``scaffold destruction,'' whereby the disruption/destruction of the hyaluronic acid polymer by hyaluronidase is accompanied by an attenuation of light emission from the J-aggregate. The extent of light attenuation provides an index of hyaluronidase activity. Other polymers of carbohydrates, proteins, nucleic acids and chemical polymers ( such as the carbon nanotube) might provide a similar scaffold for helicogenic dyes upon which molecular aggregation can occur. A key feature of these assays is that they are label-free.