Research Overview
Biosensors and Nanomedicine
One project in the lab utilizes nanometer sized metallic particles for biosensing and nanomedicine applications. Such nanoparticles alter the optical properties of adjacent chromophores, acting as antennae for absorbed and emitted light. In this project, biopolymers, such as DNA, are used to connect fluorophores to metal particles at defined distances, allowing for the systematic study of metal-fluorophore interactions. From this we can design molecular sensors for the fluorescent detection of specific proteins, DNA, or environmental pollutants.
Fluorescence lifetime measurements are ideally suited to applications in cancer diagnosis since light can be used non-invasively and, unlike light intensity, lifetimes are largely unaltered when light passes through tissue. Metal nanoparticles are known to strongly influence the optical properties of molecules held in close proximity, decreasing the time that an adjacent molecule remains in an excited state. We are producing gold nanoparticle sensors that respond to the genetic expression inside cancerous cells by undergoing an increase in fluorescence lifetime upon binding an overexpressed mRNA sequence.
Gold nanoparticles will be synthesized and appended with stem-loop oligonucleotide sequences. The terminus of the stem-loop DNA will contain a fluorescent molecule that will be characterized before and after exposure to mRNA from the HER2/ neu gene. Binding is anticipated to linearize the stem-loop structure, resulting in an increased metal-fluorophore separation and an increase in lifetime.
Optical diagnosis of cancer using fluorescence lifetime measurements is a technique that can be used non-invasively without causing harm or discomfort to a patient. By attaching metal nanoparticles to fluorophores we aim to create lifetime based sensors that detect genes associated with cancer using optical measurements. A technology that can identify cells expressing a specific gene will also enable more precise, targeted removal of cancerous tissue.
Sol-Gel Based Bio Sensors
The integration of antibody assays into robust automated instrumentation will require methods of antibody immobilization that protect and stabilize the antibodies while maintaining their structure and activity. Sol-gels are glasses prepared from soluble precursors, such as metal alkoxides that have been prepared with antibodies encapsulated inside of them. Immobilization of proteins within glass formed by sol-gel methods has been shown to trap and protect proteins, however, it also renders them immobile. Many methods of quantifying antibody binding assays, such as fluorescence polarization (FP) and fluorescence resonance energy transfer (FRET), require mobility of the antibodies to function properly. The sol-gel nanocavities being developed in this project are designed to allow for mobility of antibodies that are entrapped in a sol-gel.
Mimicking the Cellular Approach to Synthesis
This research integrates lessons learned from biology into the design of environmentally benign syntheses. Research on environmentally benign synthetic methods, or green chemistry, has the potential not only to impact how we perform chemical syntheses, but also to change how we educate students and the public about chemistry. The role chemistry has in improving the lives of people is lost on much of the public as well as students of chemistry who often are more aware of the past failures of chemistry to protect human health and the environment than its successes.
| Contact Information:
Scott M. Reed, Ph.D.
Assistant Professor of Chemistry
Portland State University
PO Box 751
Portland, OR 97207
ph: (503) 725 8512
fax: (503) 725 9525
email: sreed at pdx dot edu |
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