Fibre optic microarrays for the detection and enumeration of harmful algal bloom species

Harmful algal blooms (HABs) are a serious threat to coastal resources, causing impacts ranging from the contamination of seafood products with potent toxins to mortalities of wild and farmed fish and other marine animals. As the threat from HABs has expanded, new approaches have become necessary, including monitoring the plankton for HAB species. Preliminary data are presented on an innovative approach to HAB cell enumeration - fibre optic genosensors. Oligonucleotide probes specific for ribosomal RNA (rRNA) of target HAB species are coupled to microspheres (similar to 3 mu m) placed in wells etched in the ends of optical fibre bundles of 6 000 individual fibres. This bead-based microarray is dipped into a plankton or culture sample that has been lysed to release nucleic acids. The target rRNA is 'captured' on the functionalised beads using a probe complementary to a different region of the molecule. Probe-target hybrids are detected using a second 'signal' probe and visualised via the fibre using epifluorescence and image analysis. Preliminary results show the method to be highly sensitive, with detection limits of approximately 5-10 cells sample(-1) for Alexandrium fundyense and Pseudo-nitzschia australis, and about 50 cells sample(-1) for A. ostenfeldii. A multiplexed microarray has also been developed to detect these species simultaneously. In theory, hundreds of species can be detected using a single optical fibre array. The simplicity and the ability to re-use the sensor array without loss of sensitivity makes this a promising procedure for further development, including deployment on moored instruments capable of detecting HAB species in an early warning system.