Electrospun Nanofibers as Substrates for Surface-Assisted Laser Desorption/Ionization and Matrix-Enhanced Surface-Assisted Laser Desorption/Ionization Mass Spectrometry

Electrospun polymeric nanofibers (polyacrylonitrile, poly(vinyl alcohol), and SU-8 photoresist) and carbon nanofibers pyrolyzed to final temperatures of 600, 800, and 900 degrees C were used as substrates for surface-assisted laser desorption/ionization (SALDI) and matrix-enhanced surface-assisted laser desorption/ionization (ME-SALDI) analyses. Sample preparation of polymeric analytes using the electrospun target plate for SALDI analysis is simple and fast. Signal enhancements for poly(ethylene glycol) were noted with nanofibrous carbon substrates compared to those obtained with commercially available stainless steel plates when no organic matrix is used Minimal fragmentation was observed. Poly(ethylene glycol) with a molecular weight as high as 900 000 Da was successfully detected using the carbon nanofibrous substrate processed to 800 degrees C, which is the highest molecular weight that has been studied by SALDI. Small molecules were detected using nanofibrous carbon substrate processed to 800 degrees C. For example, spectra of glucose, arginine, and crystal violet were obtained with no observed interferences in the low molecular weight range. The SALDI results show enhanced shot-to-shot reproducibility compared to matrix-assisted laser desorption/ionization (MALDI). High-quality polystyrene spectra were obtained for the first time using SALDI nanofibrous polyacrylonitrile substrates. Significantly enhanced signal-to-noise ratios were obtained using ME-SALDI compared to conventional MALDI or SALDI for the studied analytes. A detection limit of 400 amol was achieved for angiotensin I using the nanofibrous carbon ME-SALDI substrate.