Biomarker-Based Analysis for Contaminants in Sediments/Soil: Review of Cell-Based Assays and cDNA Arrays

ERDC TN-DOER-C19

December 2000

Biomarker-Based Analysis for Contaminants

in Sediments/Soil: Review of Cell-Based

Assays and cDNA Arrays

PURPOSE: This technical note reviews the existing technology for cell-based biomarker assays

and cDNA arrays and explores their potential as rapid, sensitive, and low-cost tools for sediment/soil

toxicity screening. The current project extends the application of biomarker-based assays initiated

in Technical Note DOER-C1 for dioxins and related compounds to additional sediment/soil contam-

inants and contaminant modes of action (U.S. Army Engineer Waterways Experiment Station

1998).

BACKGROUND: Presently, sediment evaluations and contaminant monitoring for remediation,

confinement, and treatment of high-risk dredged material involve expensive and time-consuming

chemical analyses, toxicity testing, and bioaccumulation testing. Sediment chemical analyses are

sensitive and specific, but do not necessarily reflect the potential impacts of the contaminants on

biota. Tissue residues in exposed organisms provide more relevant information by addressing the

questions of bioavailability and the potential for trophic transfer. However, residues are largely lim-

ited to individual metals and organic chemicals that bioaccumulate rather than compounds that are

metabolized or may be present as complex mixtures. Actual bioassays provide the most interpret-

able results in terms of survival, growth, and reproduction, but are time-consuming, expensive, and

labor-intensive. Application of an appropriate screening assay can reduce the high cost of testing.

Good screening tests must be fast and inexpensive to perform while at the same time capable of dis-

criminating between sediments/soils that are unequivocally acceptable or unacceptable for place-

ment in the open environment and those that are questionable and require more definitive evaluation

via bioassays.

This research is directed at the further development of screening assays for contaminated sediments

using transgenic cell lines and/or copy DNA (cDNA) microarrays that can be applied to extracts of

both sediments and organisms living in the sediments. A one-to-one comparison of assay responses

to sediment extracts and sediment-exposed organisms will allow discrimination between what is

present in the sediments and what is bioavailable. While current cell-based assays offer inexpensive

and rapid screening of one endpoint (e.g., dioxin equivalents), cDNA arrays offer the capability of

simultaneous screening of multiple endpoints. The activation of genes related to apoptosis, tumor

suppression, cell proliferation, cell cycles, cytokines, oxidative stress, and more (including dioxin

activity) will be measured in a single exposure. The information provided by cDNA arrays will pro-

vide valuable insight into the toxic modes of action of the contaminants present in sediments, which

in turn can be utilized to better direct the type of bioassay (e.g., survival, growth and reproduction,

genotoxicity) that should be conducted on those sediments/soils requiring fuller evaluation.

CELL-BASED ASSAYS: Many stable cultured cell lines are commercially available, represent-

ing various species and organ types. The so-called "immortal" cell lines have the ability to grow and

multiply without limitation, unlike normal cells, which can undergo only a limited number of divi-

sions. Given the proper growing conditions (growth media, temperature, humidity, etc.), the immor-

talized cells can easily be maintained under laboratory conditions. Since the cells do not undergo