Rational Modulation of the Luminescence of Upconversion Nanomaterials with Phycocyanin for the Sensing and Imaging of Myeloperoxidase during an Inflammatory Process.

Myeloperoxidase (MPO) is a heme peroxidases protein associated with many inflammation-related diseases. Although many fluorescent probes have been constructed for the assessment of MPO activity, it still remains a challege to develop a nanoprobe for highly sensitive biosensing and high-resolution bioimaging in biological system. In this work, we developed a novel luminescent nanoprobe based on upconversion nanoparticles (UCNPs) conjugated with phycocyanin (PC), which could detect the fluctuation of MPO. By grafting PC onto the surface of UCNPs through amidation reaction, the luminescence of UCNPs is quenched by PC via energy transfer. Due to the specific recognition by PC, the nanoprobe can be used for sensitive evaluation the bioactivity of MPO. The nanoprobe based on PC-UCNPs has been successfully applied for the bioimaging of MPO in living cells and an inflammatory process by taking an acute liver injury mouse as a model.