Multiplexed Detection of Tumor Markers and Discrimination of Cancer Cell Types by Laser Ablation-Dielectric Barrier Discharge Ionization-Mass Spectrometry

We present an ambient mass spectrometry immunoassay platform based on specific mass tags detected by laser ablation-dielectric barrier discharge ionization-mass spectrometry (LA-DBDI-MS). It features high sensitivity, multiplexed quantitation, minimal sample consumption, and convenient operation. The organic small-molecule mass tags allow very high sensitivity and quantitative detection of multiple proteins, even of membrane-bound proteins on cell surfaces, through signal amplification (approximately 600 times). By using just 2 μL of serum, we achieved the detection of thrombin (LOD 6.6 pM) and cancer antigen 125 (CA125) (LOD 1.4 U/mL). Seven protein biomarkers, including CA125, carcinoembryonic antigen (CEA), epithelial cell adhesion molecule (EpCAM), protein tyrosine kinase 7 (PTK7), transferrin receptor 1 (CD71), cluster of differentiation 8 alpha protein (CD8a), and cluster of differentiation 33 (CD33), were simultaneously detected in situ in four types of cancer cells within 2 h. This platform is expected to enable multiplexed protein detection in single-drop samples or at the single-cell scale, distinguish different types of cells, and has potential applications in clinical diagnosis.