Suitability of invertebrate and vertebrate cells in a portable impedance-based toxicity sensor: temperature mediated impacts on long-term survival.

Using ECIS (electric cell-substrate impedance sensing) to monitor the impedance of vertebrate cell monolayers provides a sensitive measure of toxicity for a wide range of chemical toxicants. One major limitation to using a cell-based sensor for chemical toxicant detection in the field is the difficulty in maintaining cell viability over extended periods of time prior to use. This research was performed to identify cell lines suitable for ECIS-based toxicity sensing under field conditions. A variety of invertebrate and vertebrate cell lines were screened for their abilities to be stored for extended periods of time on an enclosed fluidic biochip with minimal maintenance. Three of the ten cell lines screened exhibited favorable portability characteristics on the biochips. Interestingly, all three cell lines were derived from ectothermic vertebrates, and the storage temperature that allowed long-term cell survival on the enclosed fluidic biochips was also at the lower end of reported body temperature for the organism, suggesting that reduced cellular metabolism may be essential for longterm survival on the biochip. Future work with the ectothermic vertebrate cells will characterize their sensitivity to a wide range of chemical toxicants to determine if they are good candidates for use in a field portable toxicity sensor.

Response characteristics of an aquatic biomonitor used for rapid toxicity detection.

The response characteristics of an aquatic biomonitor that detects toxicity by monitoring changes in bluegill (Lepomis macrochirus Rafinesque) ventilatory and movement patterns were evaluated in single chemical laboratory studies at concentrations near the 96-h LC(50) concentration and at the EILATox-Oregon Workshop in sequential tests of multiple unknown samples. Baseline data collected prior to exposure allows each fish to serve as its own control. When at least 70% of exposed fish exhibit ventilatory or movement parameters significantly different from baseline observations, a group alarm is declared. In the laboratory studies, the aquatic biomonitor responded to the majority of chemicals at the 96-h lc(50) within an hour or less, although substantially higher response times were found for malathion and pentachlorophenol. Workshop tests of single chemical concentrations presented as blind samples were consistent with the laboratory test results. There were no alarms under control conditions in any test. Although data are limited, the aquatic biomonitor appears to respond more rapidly to chemicals causing membrane irritation, narcosis or polar narcosis than to acetylcholinesterase inhibitors or oxidative phosphorylation uncouplers. All four monitored parameters (ventilatory rate, cough rate, ventilatory depth and movement) contributed to identification of first alarms at acutely toxic levels. Understanding these response patterns can be useful in data interpretation for biomonitor applications such as surface water monitoring for watershed protection, wastewater treatment plant effluent monitoring or source water monitoring for drinking water protection.

Using higher organisms in biological early warning systems for real-time toxicity detection.

Many biological early warning systems (BEWS) have been developed in recent years that evaluate the physiological and behavioral responses of whole organisms to water quality. Using a fish ventilatory monitoring system developed at the US Army Centre for Environmental Health Research as an example, we illustrate the operation of a BEWS at a groundwater treatment facility. During a recent 12-month period, the fish ventilatory system was operational for 99% of the time that the treatment facility was on-line. Effluent-exposed fish responded as a group about 2.8% of the time. While some events were due to equipment problems or non-toxic water quality variations, the fish system did indicate effluent anomalies that were subsequently identified and corrected. The fish monitoring BEWS increased treatment facility engineers' awareness of effluent quality and provided an extra measure of assurance to regulators and the public. Many operational and practical considerations for whole organism BEWS are similar to those for cell- or tissue-based biosensors. An effective biomonitoring system may need to integrate the responses of several biological and chemical sensors to achieve desired operational goals. Future development of an 'electronic canary', analogous to the original canary in the coal mine, could draw upon advances in signal processing and communication to establish a network of sensors in a watershed and to provide useful real-time information on water quality.