An OFF-ON chemosensor for biological and environmental applications: sensing Cd2+ in water using catanionic vesicles and in living cells

A new OFF-ON fluorescent chemosensor (L-1) for Cd2+ recognition based on a 5-chloro-8-hydroxyquinoline pendant arm derivative of 1,4,7-triazacyclononane ([9]aneN(3)) will be presented and its photochemical features in an MeCN-H2O 1: 1 (v/v) mixture, in pure water, after inclusion within catanionic vesicles, and in living cells will be discussed. The coordination properties of L-1 both in solution and in the solid state were preliminarily studied and its selectivity towards Cd2+ versus a set of different metal ions (Cu2+, Zn2+, Cd2+, Pb2+, Al3+, Hg2+, Co2+, Ni2+, Mn2+, Mg2+, K+, Ca2+, Ag+, and Na+) was verified in MeCN-H2O 1: 1 (v/v). In water, upon addition of increasing amounts of Cd2+ to L-1 an enhancement of the fluorescence emission was detected. To overcome this serious drawback, L-1 was dissolved in an innovative catanionic vesicular solution based on sodium bis(2-ethylhexyl) sulfosuccinate, a traditional surfactant, and 1-dodecyl-3-methylimidazolium bromide, an ionic liquid. When enclosed within the vesicle bilayers in water, L-1 restored its fluorescence emission property upon addition of Cd2+. Remarkably, L-1 enters the cellular membrane of living cells thus allowing the detection of intracellular Cd2+. These findings encourage the application of this new fluorescent chemosensor in real samples for histological and environmental analyses.