Extraction of substance P by functionalized iron oxide nanoparticles for matrix-assisted laser desorption/lonization mass spectrometric analysis

Functionalized iron oxide nanoparticles (IONPs) were used as concentrating probes to extract substance P (SP) from aqueous solution before matrix-assisted laser desorption/ionization mass spectrometric (MALDI/MS) analysis. Adsorption of SP onto the nanoparticles was mainly due to electrostatic interaction. After simple washing, the SP-adsorbed nanoparticles were directly analyzed by MALDI/MS. With this concentration strategy, the limit of detection (LOD) of SP in 500 μL buffer solution (pH 8) was 0.1 nM. In addition, the nanoparticles could isolate SP from a solution with high contents of salts and surfactants, thus alleviating suppression effect during MALDI/MS analysis. This new method was successfully applied to the determination of SP in rat spinal cord samples. The LOD and recovery of SP in a rat spinal cord sample were 3.1 nM and 85.7%, respectively.