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Fiber-Optic Microarray for Simultaneous Detection of Multiple Harmful Algal Bloom Species

Soohyoun Ahn,^1, David M. Kulis,² Deana L. Erdner,² Donald M. Anderson,² and David R. Walt^1*

Department of Chemistry, Tufts University, 62 Talbot Ave., Medford, Massachusetts 02155,¹ Biology Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543²

Received 9 February 2006/ Accepted 12 June 2006

Harmful algal blooms (HABs) are a serious threat to coastal resources, causing a variety of impacts on public health, regional economies, and ecosystems. Plankton analysis is a valuable component of many HAB monitoring and research programs, but the diversity of plankton poses a problem in discriminating toxic from nontoxic species using conventional detection methods. Here we describe a sensitive and specific sandwich hybridization assay that combines fiber-optic microarrays with oligonucleotide probes to detect and enumerate the HAB species Alexandrium fundyense, Alexandrium ostenfeldii, and Pseudo-nitzschia australis. Microarrays were prepared by loading oligonucleotide probe-coupled microspheres (diameter, 3 µm) onto the distal ends of chemically etched imaging fiber bundles. Hybridization of target rRNA from HAB cells to immobilized probes on the microspheres was visualized using Cy3-labeled secondary probes in a sandwich-type assay format. We applied these microarrays to the detection and enumeration of HAB cells in both cultured and field samples. Our study demonstrated a detection limit of approximately 5 cells for all three target organisms within 45 min, without a separate amplification step, in both sample types. We also developed a multiplexed microarray to detect the three HAB species simultaneously, which successfully detected the target organisms, alone and in combination, without cross-reactivity. Our study suggests that fiber-optic microarrays can be used for rapid and sensitive detection and potential enumeration of HAB species in the environment.

Present address: School of Molecular Biosciences, Washington State University, Pullman, WA 99164.