Quantitative Biosensing at the Single-Molecule Level

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The Chemical Measurement and Imaging (CMI) program of the Division of Chemistry is supporting Professor Joel M. Harris and his students at the University of Utah to develop new microscopy methods to help understand and optimize sensors for ultrasensitive detection of target biomolecules, including DNA and proteins. These goals are being addressed through the quantitative imaging of individual molecules. Single-molecule fluorescence imaging can provide absolute coverage information of both binding sites and bound target molecules on a biosensor surface. This technique represents quantitative analysis at the ultimate limit of counting individual molecules. It is first being applied to studies of peptide binding to lipid bilayers that is relevant to cell signaling and to the behavior of proteins at biosensor surfaces. Quantitative single-molecule imaging is also being adapted to measuring DNA hybridization, which forms the basis of genetic testing and gene-chip applications. The influence of electrostatic interactions on DNA binding is being studied in order to understand how ionic strength acts at controlling variability in DNA sensor applications. Single-molecule imaging can also serve as an analytical method, where counting individual bound DNA molecules on a capture surface enables detection of extremely low concentrations of target DNA in biological specimens. The program is assembling new instrumentation capable of imaging single molecules and data analysis methods for quantitative detection of molecules in the images. This research will provide routes to new understanding of structural factors that influence the performance of biosensors that are used to detect disease and toxins. The research also advances fundamental understanding of protein-membrane interactions and DNA hybridization kinetics, which are critical to development of new pharmaceuticals and biotechnologies. The research provides multidisciplinary training of graduate and undergraduate students in spectroscopy, microscopy, and bioanalytical chemistry and supports several collaborations with other research groups. The project also impacts K-12 science education and public awareness through development of microscopy exercises and their deployment in classrooms of a Title I elementary school in Salt Lake City.