Detection of the red tide-causing plankton Chattonella marina using a piezoelectric immunosensor

Red tide is a phenomenon caused by small algae or phytoplankton where upon seawater appears red. Both toxic and non-toxic red tides have occurred throughout recorded history but in recent years there has been a global increase in the number of these events due to coastal pollution and to other unclear factors; for example, long-distance transport of species across oceans. Some kinds of red tides cause mass deaths of cultured fish and thus cause serious economic problems for countries where fish is one of the important protein supplies. In Japan, the Chattonella species is one of the dominant representatives among many kinds of flagellates recognized in red tides. In this paper, determination of Chattonella marina was performed using a piezoelectric immunosensor comprising a gold-coated piezoelectric crystal coated with monoclonal antibody MR-21. This antibody shows highly specific reactivity towards the cytoplasmic membrane of C. marina. The resonance frequency of the piezoelectric crystal is associated with a mass change at the surface and measurement of the frequency shift by reaction between the antibody MR-21 immobilized on the piezoelectric crystal and C. marina enables to detect C. marina. This immunosensor system is able to detect 102 to 104 cells ml−1 of C. marina directly in seawater.