A chemical amplifier was constructed based on enzyme-encapsulated mesoporous silica nanoparticles. By employing a supramolecular nanogate assembly that is capable of controlling the access to the encapsulated enzyme, selectivity toward substrate sizes is enabled. When an analyte molecule actuates the mechanical nanogate and exposes the enzymes, a catalytic production of fluorescent molecules is initiated. This study demonstrates a new concept of self-amplification of a chemical sensing process and can potentially increase the detection sensitivity.