Microcystin (MC) monitoring is challenging due to the large number of congeners, low detection limits, and laborious sample pretreatment. Here we describe a novel analytical method coupling immunoconcentration to quantitative MALDI-TOF MS allowing the rapid identification and highly sensitive detection of these toxins. A site-specific <i>in vivo</i> biotinylated nanobody of broad cross-reactivity with MC congeners is the key element that allows to prepare an oriented and tightly packed magnetic immunoadsorbent, which is partially loaded with an internal standard for MS quantitation. After immunocapture, the washed beads are directly dispensed on the MALDI target and analyzed. Due to the separation of the sample contaminants during the concentration step no sample treatment is needed even for biological samples. The method showed excellent recovery and precision with water and serum samples at quantitation limits of 0.025 ppb.

Ultrasensitive MALDI-TOF quantitation of microcystins in complex matrices by direct on-target analysis of nanobody-captured toxins

2019 Fall National Meeting

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