Modification of MALDI targets by nanoparticles during iron oxide(III) suspension electrospreying under normal conditions

A method for modifying a target for the MALDI-MS analysis is proposed, allowing selective isolation of analytes from biological samples directly on the target surface, as an alternative to classical methods. To modify the target, a suspension of the metal-affinity sorbent based on iron (III) oxide in a 50% aqueous methanol solution was electrosprayed in drip-free mode with dynamic dividing the fluid flow at atmospheric pressure under normal conditions. The MALDI target acted as a counter electrode. A sorbent layer was deposited on the MALDI target in the form of a spot, the particles of which are subsequently resistant to solvents. A metal-affinity enrichment of a phosphorylated peptide with the amino acid sequence SSNGHV(pY)EKLSSI from a sample of human tryptic hydrolyzate was performed on a modified MALDI target. MALDI-mass spectrum was recorded from the sorbent spot. This technique was created as an alternative to the laborious sample preparation of bioassays and allows to limit the minimum volume of the sample and solvents.