Rapid detection of Saxitoxins using MALDI-TOF mass spectrometry

Saxitoxins (STX) is the major paralytic-shellfish-toxins (PSTs) found in some strains of toxic dinoflagellates. Because dinoflagellates are one of the basis of the marine food chains, STX can be bioaccumulated into seafood... [ view full abstract ]

Saxitoxins (STX) is the major paralytic-shellfish-toxins (PSTs) found in some strains of toxic dinoflagellates. Because dinoflagellates are one of the basis of the marine food chains, STX can be bioaccumulated into seafood such as fishes and especially filter-feeders and molluscan shellfish. STX is highly toxic and hence consumption of STX-contaminated seafood is of public concerns. In the context of Hong Kong and the South-East Asia where seafood is served fresh and sometimes raw, there is a strong need to determine the presence of STX in biological samples rapidly. Traditional determination of STX through biological assay such as mice-biotoxicity test is lengthy and consumed many mice. Other methods such as LC-MS/MS was developed. However, in many LC-MS setup, the turn-around time of each sample is still not quick enough to meet rate of human consumption in the Asian context. Some work on detection of STX using MALDI-TOF was conducted previously. However, because of the small sizes of the STX and other kinds of PSTs, their peaks were very close to the irrelevant peaks in the beginning of the spectrum. This affects accuracy of the MALDI-TOF mass-spectrometric approach. To circumvent this problem, we fabricated a series of 2,4-dinitro- phenylhydrazine-based chemicals to react with STX and associated chemicals. On a MALDI-TOF MS, our preliminary results showed that the reaction products are having higher M/Z ratios when compared to the unmodified STX and hence were far away from the initial peaks of the spectrum. More accurate and fast determination of STX could be performed.