Towards environmental toxicogenomics development of a flow-through, high-density DNA hybridization array and its application to ecotoxicity assessment

Assessment of the environmental hazard posed by soils sediments containing low to moderate levels of contaminants using standard analytical chemical methods is uncertain due Žin part. to a lack of information on contaminant bioavailability, the unknown interactive effects of contaminant mixtures, our inability to determine the species of a metal in an environmental matrix, and the relative sensitivity of bioassay species. Regulatory agencies compensate for this uncertainty by lowering cleanup goals, but in this process they effectively exclude otherwise attractive cleanup options Ži.e. bioremediation.. Direct evaluations of soil and sediment toxicity preclude uncertainty from most of these sources. However, the time and cost of chronic toxicity tests limits their general application to higher levels of tiered toxicity assessments. Transcriptional level ŽmRNA. toxicity assessments offer great advantages in terms of speed, cost and sample throughput. These advantages are currently offset by questions about the environmental relevance of molecular level responses. To this end a flow-through, high-density DNA hybridization array Žgenosen- sor. system specifically designed for environmental risk assessment was developed. The genosensor is based on highly regular microchannel glass wafers to which gene probes are covalently bound at discrete Ž200- m diameter spot. and addressable Ž250- m spot pitch. locations. The flow-through design enables hybridization and washing times to be