X-ray structurally characterized sensors for ratiometric detection of Zn(2+) and Al(3+) in human breast cancer cells (MCF7): development of a binary logic gate as a molecular switch.

A very simple molecule derived from salicylaldehyde and N-phenyl ethylenediamine (L1) functions as dual-mode ratiometric fluorescence "turn on" sensors for Zn(2+) and Al(3+) at two different wavelengths. The sensing is based on the combined effect of inhibition of excited-state intra-molecular proton transfer (ESIPT), CH=N isomerization and chelation-enhanced fluorescence (CHEF). Moreover, the [L1-Zn(2+)] system functions as a better Al(3+) sensor where Al(3+) ratiometrically displaces Zn(2+) from the [L1-Zn(2+)] complex. Emission wavelength dependent differentiation of Zn(2+) and Al(3+) using L1 allows us to develop a binary logic gate that functions as a molecular switch. L1 efficiently detects Zn(2+) and Al(3+) in human breast cancer cells (MCF7) while the [L1-Zn(2+)] complex specifically detects Al(3+) in the said cells.