Pulse laser-induced generation of cluster codes from metal nanoparticles for immunoassay applications

In this work, we have developed an assay for the detection of proteins by functionalizednanomaterials coupled with laser-induced desorption/ionization mass spectrometry (LDI-MS)by monitoring the generation of metal cluster ions. We achieved selective detection of threeproteins[thrombin, vascular endothelial growth factor-A165 (VEGF-A165), andplatelet-derived growth factor-BB (PDGF-BB)] by modifying nanoparticles (NPs) of threedifferent metals(Au,Ag, and Pt) withthe corresponding aptamer or antibody in one assay. The Au,Ag, and Pt actedas metal bio-codesfor the analysisof thrombin, VEGF-A165, and PDGF-BB, respectively, and a microporous celluloseacetate membrane(CAM) served as a medium for an in situseparation oftarget protein-bound and -unbound NPs. The functionalized metalnanoparticlesbound to their specific proteins were subjected to LDI-MS on the CAM. The functionalnanoparticles/CAM system can function as a signal transducer andamplifier by transforming the protein concentration into an intense metal cluster ion signal duringLDI-MS analysis.This system can selectively detect proteins at picomolar concentrations. Most importantly, the system hasgreat potential for the detection of multiple proteins without any pre-concentration, separation, or purificationprocess because LDI-MS coupled with CAM effectively removes all signals except for thosefrom the metalcluster ions