Abstract:
Since fluorescence techniques are highly demanded area in biological species detection, the main
objective of this research was to develop real-time, ratiometric fluorescence sensors which can
be used for iron cation detection in physiological systems with high sensitivity and selectivity.
Previously synthesized and characterized two new ligand systems were developed into ratiometric
fluorescence probes for biological Fe3+ ion detection. Both ligands were sulfonamide derivatives
of dipicolylamine with two different R groups, biphenyl (L1=N(SO2biphenyldpa) and azobenzene
(L2=N(SO2azobenzdpa). The ligands were soluble at 0.2%(v/v) methanol solutions. Both L1 and L2
displayed ratiometric change with Fe3+ ions at 319 and 458 nm respectively. L2 had a relatively high
photostability, fluorescence increasing mechanism and a lower detection limit of 18.22 nM which is a
suitable concentration for biological iron detection with high sensitivity and high selectivity. L1 had
a lower detection limit of 0.674 μM and fluorescence increasing and decreasing mechanisms. Since
both ligands had minimum interferences from other common metal cations such as K+, Na+, Ca2+,
Mg2+, Ba2+, Fe2+, Cu2+ and Zn2+, the selectivity was considered to be very high. The pH sensitivity of
the both ligands were also considerably low. L2-Fe3+ complex was blue green in color with a possible
applicability for common fluorescence microscopes. Both ligands metal complexes had higher
UV-Visible absorbance than their respective free ligands. The ligands could be recovered from the
metal complexes with the addition of ethylenediaminetetraacetic acid (EDTA). All the experimental
procedures were carried out at physiological pH, 7.4 using HEPES buffer system. Beside the
biological systems the probes are applicable for other environmental and industrial samples to ferric
iron detection.
