Neurotoxin and Cytotoxin Detection in Water Supplies During Sample Collection

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. Most cyanobacterial blooms, however, are not toxic. Furthermore, bloom toxicity will change over time. Therefore, cyanobacterial identification is not enough; toxin presence must be confirmed. There are many biological/toxicological methods available to detect these toxins. The main drawback of these biological techniques is that they are time consuming, laboratory-based, and require significant technical expertise. With dynamic systems such as cyanobacterial blooms, detection and identification of toxins should be conducted as quickly as possible, preferably in the field. The goal of this research project is to develop a field-portable automated sensor based on Surface-Enhanced Raman Spectroscopy (SERS) that can be used by nonspecialists. The entire system will weigh approximately 10 pounds and will detect the different toxins through a simple dipstick arrangement. SERS spectroscopy, which directly measures chemical bonding, theoretically would allow direct determination of all analytes; however, practical identification of the desired toxins in the presence of nontoxic bacteria and other chemical constituents in the water supply could become unwieldy. There are methods by which SERS substrates can be made specific for certain analytes using chemical modifications. These modifications can alter the surface chemistry to attract chemicals with a certain electronegativity, pH, or chemical reactivity. EIC Laboratories, Inc., (EIC) will use the latter and develop SERS substrates highly specific for the toxins of interest. Phase I demonstrated the potential for SERS as a cyanotoxin sensor, in which cylindrospermopsin, microcystins, anatoxin-a, saxitoxins, and domoic acid all were detected. Rapid detection of high fg toxin quantities was demonstrated with the SERS sensor. Phase II will expand the SERS sensor capabilities to detect microcystin, anatoxin-as, nodularin, domoic acid, and other EPA-defined cyanotoxins of interest. In Phase II, EIC will develop an easy-to-use, automated cyanotoxin methodology that will be tested at an environmental laboratory; a prototype field-portable sensing system that will weigh approximately 10 lbs. also will be designed. The sensor will be capable of being immersed in surface water by a field engineer for rapid results, mounted at a processed water facility for continuous monitoring, or used at an environmental laboratory as a sample prescreener. The final instrument will have a target sensitivity of less than 1 ppb, complete selectivity for each cyanotoxin, and no false positives or negatives.