Sampling and homogenization of nanoliter tissue with a nanosecond infrared laser (NIRL) for mass spectrometric proteomics

It was recently shown that ultrashort pulse infrared (IR) lasers, operating at the wavelength of the OH vibration stretching band of water, are highly efficient at softly sampling and homogenizing biological tissue. We utilized a nanosecond infrared laser (NIRL) for tissue sampling and homogenization with subsequent LC-MS/MS analysis for mass spectrometric proteomics. Sampling was performed with murine spleen and colon tissue with an ablation volume of 1.1 x 1.1 x0.4 mm³ (approx. 0.5 µl), determined with optical coherence tomography (OCT). The identified proteins of both tissues contained tissue type specific proteins correlating with the corresponding lists of the Human Protein Atlas. The results demonstrate that tissue sampling and homogenization of small tissue volumes less than 1 µL for subsequent mass spectrometric proteomics is feasible with a NIRL and therefore is an alternative towards sampling of tissue sections with laser capture microdissection (LCM).