Facile synthesis, cytotoxicity and bioimaging of Fe3+ selective fluorescent chemosensor

The designing and development of fluorescent chemosensors have recently been intensively explored for sensitive and specific detection of environmentally and biologically relevant metal ions in aqueous solution and living cells. Herein, we report the photophysical results of alanine substituted rhodamine B derivative 3 having specific binding affinity toward Fe3+ with micro molar concentration level. Through fluorescence titration at 599 nm, we were confirmed that ligand 3 exhibited ratiometric fluorescence response with remarkable enhancement in emission intensity by complexation between 3 and Fe3+ while it appeared no emission in case of the competitive ions (Sc3+, Yb3+, In3+, Ce3+, Sm3+, Cr3+, Sn2+, Pb2+, Ni2+, Co2+, Cu2+, Ba2+, Ca2+, Mg2+, Ag+, Cs+, Cu+, K+) in aqueous/methanol (60:40, v/v) at neutral pH. However, the fluorescence as well as colorimetric response of ligand-iron complex solution was quenched by addition of KCN which snatches the Fe3+ from complex and turn off the sensor confirming the recognition process was reversible. Furthermore, bioimaging studies against L-929 cells (mouse fibroblast cells) and BHK-21 (hamster kidney fibroblast), through confocal fluorescence microscopic experiment indicated that ligand showed good permeability and minimum toxicity against the tested cell lines.