Luminescent Ln(III)-Metallopeptide Sensors for Monitoring Elastase B Activity in Complex Biological Media.

The detection and monitoring of and its virulence factors, such as the LasB protease, are crucial for managing bacterial infections. Traditional fluorescent sensors for this protease face limitations in bacterial cultures due to interference from pigments like pyoverdine secreted by this opportunistic pathogen. We report here a Ln(III)-metallopeptide that combines a DO3A-Ln(III) complex and a sensitizing unit via a short peptide sequence as a simple, tunable, and selective probe for detecting 's LasB. The probe's luminescence switches off in the presence of 's secretome due to LasB cleavage but remains stable in other bacterial environments, such as non-LasB-secreting strains or cultures. It also resists degradation by other proteases, like human leukocyte elastase and trypsin, and remains stable in the presence of bioanalytes related to infections, such as glutathione, HO, and pyocyanin, and in complex media like FBS. Importantly, time-gated experiments completely remove the background fluorescence of pigments, thus demonstrating the potential of the developed Ln(III)-metallopeptide for real-time monitoring of LasB activity in bacterial cultures.