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Identification and quantification of bacteria affecting human life, directly causing diseases and indirectly contaminating natural ecosystems, are mostly carried out by expensive and time-consuming methods. There is the need for rapid and economic ways for detecting bacteria in the environment and in clinics. We propose the use of engineered liposomes for detecting bacteria in drinking water. Our approach exploits cationic liposomes functionalized with a surface potential-sensitive fluorophore, 4-heptadecylumbelliferone (C17-HC). The interaction between liposomes and bacteria involves a change in the surface potential experienced by C17-HC and switches on an optical signal. We investigated, by DLS, zeta-potential and fluorescence experiments, a large number of cationic liposomes formulated with a natural phospholipid 1,2-dipalmitoyl- sn -glycero-3-phosphocholine (DPPC) or 1,2-dioleoyl- sn -glycero-3-phosphocholine (DOPC), C17-HC, and one of three synthetic cationic components, differing from each other for the number of unsaturations on the polar ammonium head, two of which ad hoc synthesized. Then we evaluated the ability of liposomes to produce a fluorescent signal upon interaction with three bacterial strains, Staphylococcus aureus , Escherichia coli and Enterococcus faecalis ; moreover, we analyzed the fluorescent response of each liposome formulation in the presence of the three bacterial strains at the same time, in order to simulate a real scenario. We found that interaction with bacteria triggers an optical signal in six of the evaluated formulations, resulting responsive down to 10 2 CFU/mL of bacteria suspended in pipeline water coming from the water main of Rome (Italy).

5-Fluorouracil (5-FU) is a chemotherapic drug widely employed to treat a wide range of solid tumors. Unfortunately, it has a narrow therapeutic window and the level of its target enzymes in biological fluids of patients can vary considerably. On these premises, a new fluorescent lipid based sensor for the detection of thymidine phosphorylase, one of the target enzymes of 5-FU, was developed, to optimize patient treatment. Both cationic and anionic fluorescent liposomes containing both an amphiphile tail-tagged with a pyrene residue and a 5‐FU derivative were investigated. The effect of the presence of a bulky quencher (the bromine atom) covalently linked to the end of the alkyl chain of the anionic component on the emission signal was also evaluated. The interaction of liposomes with the target enzyme induces the occurrence of a fluorescent signal, at an extent that depends on the formulation, due to the variation of the excimer/monomer ratio. In particular, a promising specific result was obtained upon the interaction of the target enzyme with liposomes formulated with DOPC, the cationic fluorescent surfactant, the 5-FU derivative and 11-bromoundecaonic acid at 5/1/1/3 molar ratio. Langmuir compression isotherms allowed clarifying the influence of lipid organization on the response of the sensor.