Superhydrophobic Glass Substrates Coated with Fluorosilane-Coated Silica Nanoparticles and Silver Nanoparticles for Surface-Assisted Laser Desorption/Ionization Mass Spectrometry

Superhydrophobic delivery is an effective approach to enrich trace amounts of molecules. Herein, we demonstrate a simple method based on superhydrophobic delivery for trace analysis with surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). In this method, silver nanoparticles and a superhydrophobic coating layer composed of fluorosilane-coated silica (termed AgNPs/SHC) are prepared on a cover glass, which is used as SALDI-MS substrate. The AgNPs/SHC substrate allows trace amounts of analytes concentrated onto AgNPs, which can efficiently absorb ultraviolet laser radiation and transfer energy to the analyte. Compared to the hydrophilic cover glass with AgNPs, the AgNPs/SHC substrate can greatly improve the laser desorption/ionization efficiency of the analyte. The detection reproducibility and linearity of the AgNPs/SHC substrate are further confirmed by detecting rhodamine 6G. The SALDI-MS analyses displayed high reproducibility with relative standard deviation (RSD) ≤ 9.4% for 1 pmol/μL of rhodamine 6G, and a good linearity (R2 > 0.99) is shown over the concentration ranges from 1 to 50 fmol/μL. With the AgNPs/SHC substrate, various species of trace molecules, including amino acid, fatty acid, dye molecule, polypeptide, and polymer, can be effectively detected. Moreover, this method has been successfully applied to the analysis of trace malachite green in lake water and bradykinin 1-7 in human serum. All the results show that this method has a great potential for enhancing detection sensitivity and may promote the practical application of SALDI-MS.