PNNL

Abstract

Cyanotoxins can be found in water and air during cyanobacterial harmful algal blooms(cHABs) in lakes and rivers. Therefore, it is very important to monitor their potential uptake by animals and humans as well as their health effects and distribution in affected organs. Herein, the distributionof hepatotoxic peptide microcystin-LR (MC-LR) is investigated in liver tissues of mice gavagedwith this most common MC congener. Preliminary matrix-assisted laser desorption/ionizationmass spectrometry (MALDI-MS) imaging experiments performed using a non-automated MALDI matrix deposition device and a MALDI-time-of-flight (TOF) mass spectrometer yielded ambiguousresults in terms of MC-LR distribution in liver samples obtained from MC-LR-gavaged mice. The tissue preparation for MALDI-MS imaging was improved by using an automated sprayer for matrixdeposition, and liver sections were imaged using an Nd:YAG MALDI laser coupled to a 15 TeslaFourier-transform ion cyclotron resonance (FT-ICR)-mass spectrometer. MALDI-FT-ICR-MS imaging provided unambiguous detection of protonated MC-LR (calculated m/z 995.5560, z = +1) and thesodium adduct of MC-LR (m/z 1017.5380, z = +1) in liver sections from gavaged mice with greatmass accuracy and ultra-high mass resolution. Since both covalently bound and free MC-LR canbe found in liver of mice exposed to this toxin, the present results indicate that the distributionof free microcystins in tissue sections from affected organs, such as liver, can be monitored withhigh-resolution MALDI-MS imaging.