Final Report: Polymer-Based Competitive Flow Sensor Detects Contaminants in the FieldEPA Contract Number: 68D01059
Title: Polymer-Based Competitive Flow Sensor Detects Contaminants in the Field
Investigators: Coolbaugh, M. Todd
Small Business: American Research Corporation of Virginia
EPA Contact: Richards, April
Project Period: September 1, 2001 through September 1, 2003
Project Amount: $225,000
RFA: Small Business Innovation Research (SBIR) - Phase II (2001) Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , SBIR - Monitoring , Small Business Innovation Research (SBIR)
This Phase II research project was designed to develop technology to provide field-based quantitative detection of a wide range of contaminants through the use of a fluorescent competitive flow assay based on the release of labeled analyte from a molecularly imprinted polymer (MIP) in the presence of free analyte in an environmental sample. Molecular imprinting is used to describe a process by which a material is made amenable for binding to specific target molecules by inclusion of the target in the synthesis process. The target is removed from the material, leaving binding sites selective for the molecule of interest. In an MIP, the target molecules are included in the polymerization process and removed to leave a surface with highly selective binding characteristics. In an MIP competitive assay, a labeled-target complex is bound to the MIP. In the presence of the unlabeled target, the labeled target is released from the MIP and can be detected.
The objectives of the project included: (1) preparation of MIPs optimized for use in sensing environmental contaminants; (2) synthesis of near-infrared fluorescent competition reagents for use in MIP-based assays of environmental contaminants; (3) assessment, selection, and optimization of an MIP-based competitive assay for contaminants in environmental samples; (4) design and fabrication of a prototype imprinted polymer competitive assay sensor system for use in field evaluations; and (5) acquisition of families of test data to be used in the optimization and performance assessment of a prototype sensor system for commercialization in Phase III. The project was innovative in combining a selective MIP assay with sensitive near-infrared fluorescence detection to provide an instrument for detecting contaminants in the field environment.
American Research Corporation of Virginia successfully demonstrated that a low-cost miniaturizable diode laser-based fluorescence flow system could be used for the detection of labeled analytes that may be produced on a competitive MIP assay of atrazine. The flow system was found to be sufficiently sensitive to detect fluorophore-analyte complexes at concentrations lower than 3x10-9 M without the use of a lock-in amplifier. Thick-film MIPs were prepared; these materials were optimized to provide selective binding to atrazine in a non-aqueous solution. The Phase II effort also demonstrated the use of fluorescent indicators to measure the concentration of fluorophore-analyte complexes. The indicators were excitable at 780 nm and exhibited a wavelength distribution of fluorescence extending to 100 nm from the absorption maximum. The labels were stable in both aqueous and non-aqueous solvents.
The Phase II project demonstrated that optical sensors could be developed for use in a competitive MIP assay for environmental contaminants. It was determined that the rate of release of the competition reagent from the MIP was extremely important to the successful accomplishment of a flow competition assay.