AI Summary
New fluorescent probes incorporating phenyl boronic acid and 1,8-naphthalimide tag were developed. They were able to bind to a polysaccharide and perform in vitro cell imaging. The probes' interaction with their environment and cellular uptake were studied using different microscopy techniques. These probes can sense changes in their environment and penetrate cells effectively.
New design and synthetic strategies were developed to generate functional phenyl boronic acid (BA)-based fluorescent probes incorporating the 1,8-naphthalimide (NI) tag. This fluorescent core was anchored onto the BA unit through small organic linkers consisting of nitrogen groups which are able to arrest, and internally stabilise the phenyl-B(OH)2 units. The newly synthesised fluorophores were characterised spectroscopically by NMR spectroscopy and mass spectrometry and evaluated for their ability to bind to a naturally occurring polysaccharide, β-D-glucan in DMSO and simultaneously as act as in vitro cell imaging reagents. The uptake of these new NI-boronic acid derivatives was studied living cancer cells (HeLa, PC3) in the presence, and absence, of β-D-glucan. Time-correlated single-photon counting (TCSPC) of DMSO solutions and two-photon fluorescence-lifetime imaging microscopy (FLIM) techniques allowed an insight into the probes’ interaction with their environment. Their cellular uptake and distributions were imaged using laser scanning confocal fluorescence microscopy under single- and two-photon excitation regimes (λmax 910 nm). MP FLIM facilitated the estimation of the impact of the probe’s cellular surroundings using the fluorophore lifetime. The extent to which this was mediated by the β-D-glucan was visualised by 2-photon FLIM in living cells. The fluorescence lifetime observed under a range of temperatures varied appreciably, indicating that changes in the environment can be sensed by these probes. Although in all cases, localisation was widely concentrated in the cellular cytoplasm, non-specifically, the cellular penetration of these new probes was remarkable, even under variable temperature conditions and we conclude that these new probes