Molecular design strategies of multifunctional probe for simultaneous monitoring of Cu2+, Al3+, Ca2+ and endogenous l-phenylalanine (LPA) recognition in living cells and zebrafishes

Abstract

An innovative strategy of adjusting the molecular polarity of organics is applied for multifunctional simultaneous ions detection. It involved the use of 4-bromo-2-hydroxyben Rhodamine B hydrazide (RHBr) as a colorimetric and fluorescent multifunctional chemosensor. Briefly, it was designed and prepared via integrating 4-bromo-2-hydroxybenzaldehyde with Rhodamine B hydrazide, and Rhodamine B as fluorophore group, CO, −CHN and −OH groups as reaction site, Br atom as electro n-withdrawing group. On the basis of theoretical calculation under Gaussian 09 software suit, RHBr could exclusively recognize Cu2+, Al3+ and Ca2+. This was also experimentally confirmed by the different turn-on colorimetric and fluorescent signals. For example the selective detection of Cu2+ ion in DMSO/H2O (1/1 = v/v, 10.0 mM HEPES pH 7.0) with the “naked-eye” when the color changed from colorless to pink, Al3+ with “turn-on” strong orange-red fluorescence and Ca2+ with strong green fluorescence in EtOH/H2O (v/v = 95/5). Under the optimized conditions, all the ions could be detected at a very low concentrations (1.7 × 10−7 M, 1.0 × 10−8 M, 2.8 × 10−7 M for Cu2+, Al3+, and Ca2+, respectively). In addition, the “in situ” formed RHBr-Al3+ was used to recognize l-phenylalanine (LPA) with a “turn-off” fluorescence ranging from 0.03–10.0 μM with the low detection concetration of 3.0 × 10−7 M. The sensing mechanisms of RHBr toward three metal ions and the ensemble RHBr-Al3+ toward the l-phenylalanine (LPA) were further investigated in detail. Practical application experiments further proved that RHBr had good cell permeability and could be utilized to detect Al3+ and Ca2+, and the complexes of RHBr-Al3+ could be applied to detect l-phenylalanine (LPA) in the living cells and zebrafishes, respectively.