Efficient FRET-based colorimetric and ratiometric fluorescent chemosensor for Al3+ in living cells

In this paper, we have developed the first example for colormetric and ratiometric fluorescent detection of Al3+ based on naphthalimide-rhodamine compound (la). The ratiometric fluorescent signal change of the chemosensor is on the basis of FRET Off-On mechanism modulated by Al3+ induced configuration transformation of the rhodamine from a spirolactam ring to the ring-opened amide. In comparison with the fluorescent chemosensors based on single emission intensity change, ratiometric chemosensors are beneficial for increasing the dynamic response range and providing built-in correction for environmental effects. Under optimized experimental conditions, the chemosensor exhibits a stable response for Al3+ over a concentration range from 5.0 x 10(-7) to 1.0 x 10(-5) M, with a detection limit of 1.0 x 10(-7) M. The experiment results show that the response behavior of la toward Al3+ is pH independent in medium condition (pH 6.0-8.0). Moreover, the fluorescence changes of the chemosensor are remarkably specific for Al3+ in the presence of other metal ions except Mn2+, which can meet the selective requirements for practical application. In addition, the chemosensor was successfully applied for ratiometric visualization of Al3+ in living cells. (C) 2013 Elsevier B.V. All rights reserved.