Developing a Peptide-Based Near-Infrared Molecular Probe for Protease Sensing

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Abstract
Recently near-infrared (NIR) molecular probes have become important reporter molecules for a number of types of in vivo biomedical imaging. A peptide-based NIR fluorescence probe consisting of a NIR fluorescence emitter (Cy5.5), a NIR fluorescence absorber (NIRQ820), and a protease selective peptide sequence was designed to sense protease activity. Using a MMP-7 model, we showed that NIRQ820 efficiently absorbs the emission energy of Cy5.5 resulting in a low initial signal. Upon reacting with its target, MMP-7, the fluorescence signal of the designed probe was increased by 7-fold with a Kcat/Km of 100 000 M-1 s-1. The described synthetic strategy should have wide application for other NIR probe preparations.