A core-shell nanoparticle-peptide@metal-organic framework as pH and enzyme dual-recognition switch for stepwise-responsive imaging in living cells.

A core-shell nanostructure is fabricated with a pH-sensitive metal-organic framework shell and a peptide functionalized gold nanoparticle core via a mild synthetic route. The nanostructure can be applied as a dual-recognition switch in response to an acidic environment and enzyme activity, sequentially, leading to a stepwise-responsive strategy for imaging lysosomal cathepsin B.