Functionalization of thermoswitchable liposomes for rapid detection of Gram-negative bacteria

Biosensors for rapid and sensitive detection of pathogens play a crucial role in healthcare and food safety. Despite the development of numerous sensing devices, it remains a challenge to obtain biosensors that are reliable, easy-to-use and can offer results within minutes. Herein, we report a functionalized liposome, with an embedded fluorescent dye to offer thermoswitchable emission, for selective Gram-negative bacteria detection. This targeting system utilizes polymyxin B (PmB) as a recognition element, where it can be conjugated onto the surface of the liposome to differentiate Gram-negative bacteria from Gram-positive counterparts as well as mammalian cells via fluorescence spectroscopy. The unique thermoswitchable fluorescence conferred through manipulation of aggregation-induced quenching allows for high signal-to-noise detection, reaching up to 3.5-fold increase in emission in the case of E. coli. This is in contrast to typical small organic fluorescent labels and future work includes developing a suitable capture probe to achieve lower limits of detection.Agency for Science, Technology and Research (A*STAR)Ministry of Education (MOE)This work is supported by the Ministry of Education, Singapore, under its Academic Research Fund Tier 1 (No. RT15/19, to C.L.K.L. and No. RG6/20, to B.X.) and the Agency for Science, Technology and Research, Science and Engineering Research Council (A*Star SERC), Singapore (Nos. A1983c0028 and A20E5c0090, to B.X.)