Laser-Assisted Desorption/Ionization Mass Spectrometry Using Nanoporous SiO₂ Aerogels for the Diagnosis of Colon Cancer

The SiO2 aerogel has a porous network of spherical silica particles with an average size of 3–5 nm, which provides an extremely high surface area. Herein, SiO2 aerogel was synthesized using the sol–gel method with sodium silicate as a precursor, and the SiO2 aerogel was applied to matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) as an inorganic matrix for quantitative analysis. In this work, a combi-matrix was prepared by mixing the SiO2 aerogel and a conventional organic matrix (CHCA) for quantitative analysis of analytes at an m/z ratio of less than 500. Using the combi-matrix based on the SiO2 aerogel with an extremely high porosity, analyte ionization was performed without the mass peaks of the organic matrix (CHCA) for MALDI-MS. The optimal ratio between the SiO2 aerogel and the organic matrix was determined to eliminate the mass peaks from the organic matrix and maximize the signal-to-noise ratio (S/N ratio) of the analytes. Quantitative analysis was performed using the optimal combi-matrix system (a mixture of SiO2 aerogel and organic matrix (CHCA)). The homogeneous and dense distribution of analytes was demonstrated using fluorescence imaging, and the spot-to-spot and shot-to-shot reproducibility was estimated using the SiO2 aerogel. Finally, LDI-MS based on the combi-matrix was applied for the quantitative analysis of a biomarker for colon cancer, dodecanoyl-l-carnitine (DC). Using real samples from healthy volunteers and patients, a medical diagnosis of colon cancer was demonstrated using a combi-matrix.