A resorufin-based fluorescent turn-on probe responsive to nitroreductase activity and its application to bacterial detection

Abstract

We present two resorufin-based fluorescent turn-on probes responsive to nitroreductase (NTR) activity (NTR probes 1 and 2) and their use toward the detection of bacteria. The probes exhibit a fluorescence turn-on at 586 nm in response to NTR activity, which corresponds to a vivid pink color. These optical changes are based on the NTR-mediated reduction of the nitro groups in the probes, which results in the production of highly fluorescent resorufin. The detection ability, mechanism, and enzyme kinetics of the probes for NTR activity have been thoroughly investigated. The enzyme efficiencies of the probes were superior to those previously reported. In addition, NTR probe 1 exhibited an excellent detection ability for NTR with high selectivity and no background signal when compared to 2. Moreover, NTR probe 1 was applicable for bacterial detection using a wash-free process because it gave rise to a fluorescence turn-on signal in response to bacterial NTR activity.