Peptide-specific nanoprobes for matrix-free mass spectrometric imaging of multiplexed proteins and their distributions on cells or tissues

In situ detection of multiplexed proteins is greatly constrained by targeted recognition and operational process. Here we design a one-pot method to synthesize several peptide-specific nanoprobes (NPs) for quickly recognizing the targeted protein molecules, and present a matrix-free laser desorption/ionization mass spectrometric imaging (LDI-MSI) strategy for simple in situ imaging of multiplexed proteins on cells or tissues with amplified signals. Unlike conventional citrate-synthesized and post-modified gold nanoparticles, the resulting NPs demonstrate their simple preparation, high resolution and low background with controllable matrix-free and ion-friendly properties. These NPs have been used to conveniently and sensitively detect the relative expression of three specific proteins on four cancer cell lines and efficiently evaluate the suppression of different drugs on these proteins. The proposed MSI method possesses powerful ability to distinctly distinguish different pathological regions of tumor tissues by the change of multiplexed protein distributions, indicating its excellent promise in clinical disease diagnosis and precision medicine.