Our
research focuses on applications of bioanalytical chemistry,
biocatalysis, nanobiotechnology, and medical diagnostics.
Our general philosophy is to apply our knowledge of
chemistry and biology to the solution of some of the
problems of our society. Our work pursues advances in
bioanalytical and biological chemistry coupled with
nanoscience as they impact on medical diagnostics, environmental
health, and drug technologies. We have ongoing research
projects in biosensor arrays for in-vitro sensing of
toxicity, arrays for cancer biomarkers for early detection,
high temperature biocatalysis for chiral synthesis,
and fundamental protein redox chemistry.
A major component of our research involves
designing biomembrane-like films containing enzymes,
DNA, polyions, and nanomaterials. We developed layered
films of enzymes and lipid molecules similar to those
in living membranes, and we can sandwich enzymes between
polyions or on top of carbon nanotubes. We have grown
films of proteins, polymers and DNA one layer at a time,
resulting in precisely controlled film designs. We discovered
that electrons are transferred to these enzyme films
on electrodes at rates over 1000-times larger than when
dissolved in water. We use these films to catalyze metabolic
enzyme reactions that produce DNA-damaging products.
This application mimics a major toxicity pathway in
the human liver, and is being used to develop toxicity
sensor arrays. Such arrays are important in early drug
screening for genotoxicity. They utilize electrochemical,
optical, or LC-MS detection. Other applications of these
films include biosensors for stem cell regulators, enzyme
biocatalysis for organic synthesis, elucidating redox
properties of photosynthetic proteins, and toxicity
activation studies. Genetic engineering is used to obtain
the bacterial and human enzymes needed. A related project
involves the combination of carbon nanotubes and immunosensing
technology to develop highly sensitive arrays for cancer
biomarkers that will be used for early cancer detection.
These projects involve collaborations with pharmacologists,
cancer biologists, materials scientists and engineers
on and off campus, as well as in Ireland and Italy,
and are funded by the US National Institutes of Health
and the Army Research Office.
Many techniques are applied to characterize
the films and biosensor chemistry. These include atomic
force and electron microscopy, UV-VIS linear and circular
dichroism, voltammetry, amperometry, quartz crystal
microbalance, spectroelectrochemistry, polarized reflectance
FT-IR, Raman, capillary chromatography-mass spectrometry,
capillary electrophoresis with laser fluorescence detection,
ESR, NMR and computer modeling.
Another major effort is funded by the
National Science Foundation and employs advanced nanostructured
fluids called microemulsions that we are developing
as substitutes for organic solvents for "green"
synthesis of organic compounds. Microemulsions are clear,
stable mixtures of surfactant, oil, and water that are
less toxic and less costly replacements for organic
solvents. Acting like soap solutions, these fluids dissolve
both nonpolar and polar reactants. They allow us to
avoid toxic organic solvents and enhance reaction rates
by unique kinetic control pathways. Successful catalytic
syntheses with rate improvements in excess of 1000-fold
have been obtained. Currently, highly stable, crosslinked
films of enzymes and polyions are being designed on
silica nanoparticles for high temperature biocatalysis
in microemulsions. These new enzyme films can catalyze
stereospecific reactions at temperatures approaching
100 oC, which destroy enzymes in solution in a few minutes.
Techniques used include capLC-MS, GC-MS, diode array
spectroscopy, NMR, voltammetry, and many types of surface
and solution spectroscopy.
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