Poly(L-dopa) film-assisted laser desorption/ionization of small biomolecules and drugs

Abstract

Although matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) owns unique merits, the applicability of MALDI for small molecule analysis is still very limited due to the matrix-related interferences in low-mass region. We present a new strategy for the analysis of small biomolecules and drugs by LDI MS. Poly(L-dopa) film was in situ polymerized on standard stainless steel MALDI plate, and the analytes deposited on the film were vaporized and ionized under laser irradiation. Poly(L-dopa) film was found highly effective for laser desorption/ionization of small molecules including amino acids, organic acids, nucleosides, monosaccharides and sulfa drugs at pmol levels with extremely low background noise. Amino acids was detectable even in saturated salt solution. The good salt tolerance and high sensitivity allowed its application to the detection of celecoxib in serum at concentration as low as 0.29 μM. The preparation of poly(L-dopa) film is very simple and convenient. It is believed that poly(L-dopa) film-assisted laser desorption/ionization mass spectrometry has potential to be a practical solution for small biomolecule analysis.