Longitudinal surface plasmon resonance based gold nanorod biosensors for mass spectrometry.

A "strategy" for analyte capture/ionization based on chemical derivatization of gold nanorods and infrared laser desorption ionization (IR-LDI) is described. This is the first example of laser desorption/ionization of biomolecules using gold nanorods irradiated with an IR laser. LDI is performed at wavelengths (1064 nm) that overlap with the longitudinal surface plasmon resonance (LSPR) mode of gold nanorods. The absorbed energy from the laser facilitates desorption and ionization of the analyte. The wavelength of the LSPR band can be tuned by controlling the aspect ratio (length-to-diameter) of the nanorod. For example, the SPR band for Au nanorods having an aspect ratio of 5:1 is centered at approximately 840 nm, and this band overlaps with the 1064 nm output of a Nd:YAG laser. We show that a variety of biomolecules can be efficiently desorbed and ionized by 1064 nm irradiation of nanorods. We also show that analyte capture can be controlled by surface chemistry of the nanorods. The results of these studies are important for designing nanomaterial-based capture assays for mass spectrometry and interfacing nanomaterials with imaging/spatial profiling mass spectrometry experiments.