This doctoral thesis aimed to design and evaluate molecular probes releasing a solid‐state fluorophore (1) for the detection of enzymes of biomedical interest, (2) for the identification of pathogenic bacteria, and (3) for exogenous enzyme activities showing promise as new reporter gene products. Five probes (and a few structural variants) for five different enzyme activities, respectively, were prepared: 1. α-glucosidase (GAA), 2. dipeptidyl peptidase IV (DPP IV), 3. porcine liver esterase (PLE), 4. bacterial carboxypeptidase G2 (CPG2), 5. Genetically modified γ-glutamyl transferase* (GGT*). In particular, the syntheses of the probe structures for GAA and DPPIV activity were hard to accomplish, but efficient routes were finally established. Synthetic pathways to two further probes have been significantly advanced; these probes make use of the double-gating strategy that consists in the presentation of two enzyme substrate units on the same probe so as to make the release of the active fluorophore dependent on the subsequent conversion by two target enzyme activities, here: 1. C8-esterase and α-galactosidase and 2. GAA and phosphatase. In collaboration with biologists in our team, the completed probe molecules were tested in vitro against their enzyme targets and found to respond swiftly to their activities by releasing a solid-state fluorophore. They were also proved to be specific to their target activities with regard to select other enzyme activities that were tested simultaneously. The probes also tested in contact with adequate live cell lines in culture, and will continue to be tested and adapted further in ongoing research. Selected results from above will be the subject of future research publications in peer-reviewed journals. With significant extra personal investment, Junchao XU was also able to make good on the time lost during the repetitive lockdowns he had to endure, be that in France, or during his first visit to his family in China beginning of 2020.