Grantee Research Project Results

Final Report: Neurotoxic/Cytotoxin Detection in Water Supplies During Sample Collection

EPA Contract Number: 68D03018
Title: Neurotoxic/Cytotoxin Detection in Water Supplies During Sample Collection
Investigators: Spencer, Kevin M.
Small Business: EIC Laboratories Inc.
EPA Contact: Richards, April
Phase: I
Project Period: April 1, 2003 through September 1, 2003
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2003) RFA Text |  Recipients Lists
Research Category: SBIR - Water and Wastewater , Watersheds , Small Business Innovation Research (SBIR)

Description:

There has been an alarming increase in toxic cyanobacteria over the past 2 decades, with numerous poisonings reported from Australia to the United States. The increased toxic risks led the U.S. Environmental Protection Agency (EPA) to include cyanotoxins on the 1998 Contaminant Candidate List. The goal of this research project was to develop a field-portable automated sensor based on surface-enhanced Raman spectroscopy (SERS) that can be used by nonspecialists for rapid identification and quantification of toxic blooms. SERS directly measures chemical bonding and theoretically allows direct determination of all analytes with complete specificity; however, SERS has poor sensitivity. By measuring the Raman signal on a roughened metal surface, enhanced sensitivity (even single-molecule detection) can be achieved for trace detection of environmental contaminants. The utility of SERS for detection of environmental concerns has been demonstrated at EIC Laboratories through the detection of buried landmines.

In this Phase I research project, the potential of SERS to detect five cyanotoxins was evaluated. The five toxins were saxitoxins, anatoxin-a, microcystins, cylindrospermopsin, and domoic acid. The initial thrust of the research was to determine the appropriate uncoated SERS metals to optimize the observed spectral signals for each cyanotoxin under study. Detection of each toxin in the fg-pg mass range was attempted. The preliminary evaluation of coatings such as thiourea and tyrosine to improve selectivity/sensitivity of each of the SERS sensors also was initiated. Finally, the capability of the SERS sensor to detect toxins from a toxin-producing bacterial strain, as opposed to the purified standards, also was examined.

Summary/Accomplishments (Outputs/Outcomes):

The Phase I results were highly encouraging. Cylindrospermopsin, anatoxin-a, and saxitoxins all were highly enhanced by using a roughened gold substrate with a carbonate additive. Domoic acid also showed greatest sensitivity towards roughened gold, but without a carbonate additive, although microcystins showed the greatest enhancement on silver substrates. For each of these toxins, a sample of less than 1 mL is required to detect the toxin near the likely EPA detection limit. The use of monolayer coatings did not appear to improve the signal intensity for any of the toxins, with the possible exception of domoic acid on a thiourea monolayer. However, there is not a statistically relevant data set to rule against coatings at this time. In addition, submonolayer and inorganic coatings have yet to be tested. Finally, the microcystins from a toxin-producing strain of Microcystis aeruginosa were detected successfully.

The Phase I results are extremely encouraging and point to the possibility of a fieldable instrument that can rapidly identify and quantify toxic blooms in surface water, or an online instrument that can monitor toxins in treated water. This sensor can streamline sampling at the source and could be used in an environmental laboratory as a rapid screening diagnostic tool to prevent wasted time and labor on the more complex instrumentation. This sensor can be expanded to other EPA contaminants of interest and will operate equally well for airborne analyses. Finally, this particular sensor has great potential as a monitor for chemical and biological warfare agents in the water supply.

Conclusions:

The main purpose of this Phase I research project was to determine the feasibility of detecting cyanotoxins at environmentally relevant concentrations. This goal was satisfactorily demonstrated with the detection of five different cyanotoxins. Based on anticipated detection limits, volumes between 10 µL to 1 mL are all that would be necessary to observe the desired signals. The initial research into using monolayer coatings to improve selectivity and sensitivity only produced marginal improvements for domoic acid and has led to the belief that submonolayers or metallic overcoatings may be more appropriate. EIC Laboratories collected spectra of microcystins from a toxin-producing bacterial strain. The results were more complicated because of the presence of other adsorbing components, but improved selectivity to the substrates and implementation of chemometrics will remove this added complexity. Phase II will focus on expanding the spectral database to include all cyanotoxins and improve sensitivity/selectivity of the individual SERS sensors.

Journal Articles:

No journal articles submitted with this report: View all 1 publications for this project

Supplemental Keywords:

neurotoxin, cyanotoxin, neurotoxin detection, cyanotoxin detection, water supplies, surface-enhanced Raman spectroscopy, monitoring, saxitoxins, anatoxin-a, microcystins, cylindrospermopsin, domoic acid, thiourea, tyrosine, online automated sensor, Microcystis aeruginosa, bioterrorism, small business, SBIR., RFA, Ecosystem Protection/Environmental Exposure & Risk, Scientific Discipline, Water, Ecological Risk Assessment, Environmental Chemistry, Engineering, Chemistry, & Physics, Monitoring/Modeling, Biochemistry, Environmental Monitoring, field portable monitoring, toxin sensors, field portable systems, cyanobacteria blooms, toxin sensor, environmental contaminants, field monitoring, sensor technology, spectrometry, cytotoxin, analytical chemistry, aquatic toxins, spectroscopic studies, field deployable

SBIR Phase II:

Neurotoxin and Cytotoxin Detection in Water Supplies During Sample Collection  | Final Report