New Ln(III) complexes as potential optical probes for biological applications

The unique properties of f-f transitions in trivalent lanthanide complexes are the understandable reason of increasing applications in biosensing field, where their long emission lifetimes, the sharp and easily recognizable emission bands in addition to the large shift between the absorbed and emitted radiation besides a short-lived background fluorescence permit the great advantage to isolate their emission signal from the undesired background fluorescence of the biological samples. Furthermore, luminescent complexes of Eu(III) and Tb(III) are the most employed candidates due to the low sensitivity of their excited state to vibrational quenching effects caused by OH, NH, or CH oscillators, frequently present in solution and imaging environments. For these reasons, Eu(III) and Tb(III) complexes have been extensively exploited as sensors of species in physiological conditions, by allowing the detection of relevant clinical biomarkers in biomedical diagnostics and imaging. For these purposes, a high luminescence emission quantum yield and overall luminosity (or brightness) are strongly required and the intensity of the luminescent response, that it is enhanced with heteroaromatic ligands via antenna effect, is usually correlated to the concentration of target analyte. In this PhD project, a library of new water soluble Eu(III) and Tb(III) complexes based on the chiral fragment 1,2-diaminecyclohexane (DACH) has been successfully synthetized, completely characterized (also in solution) and employed for analytical detection of important bio-analytes such as: bicarbonate, L-lactate, serum albumin, and citrate through mainly total luminescence (TL) and circularly polarized luminescence (CPL). These analytes are the main constituents of extracellular fluid, such as human serum.