A series of fluorescent probes from the 6-chloro-2-phenylimidazo[1,2- a ]pyridine-3-yl acetamides ligands featuring the 7-nitro-2-oxa-1,3-diazol-4-yl (NBD) moiety were synthesized and biologically evaluated for their fluorescence properties and for their binding affinity to the 18 kDa translocator protein (TSPO). Spectroscopic studies including UV-Vis absorption and fluorescence measurements showed that the synthesized fluorescent probes exhibit favorable spectroscopic properties, especially in non-polar environments . In vitro fluorescence staining in the brain sections from lipopolysaccharide (LPS)-injected mice revealed partial colocalization of probes with the TSPO. The TSPO binding affinity of probes was measured on crude mitochondrial fractions separated from rat brain homogenates using [ 11 C]PK11195 radioligand binding assay. All the new fluorescent probes demonstrated moderate to high binding affinity to the TSPO, with affinity ( K i ) values ranging from 0.58 nM to 3.28 µM. Taking these data together, we propose that the new fluorescent probes could be used to visualize the TSPO. Keywords: TSPO; fluorescent probes; imaging; neurodegenerative diseases.
