Dihydroindeno[1,2-b]pyrroles: new Al3+ selective off–on chemosensors for bio-imaging in living HepG2 cells

Abstract

In this study, a new molecular organic probe has been designed and synthesized by using recyclable, inexpensive and non-toxic polyethylene glycol (PEG-400) as a promoting reaction medium in water under environmentally benevolent conditions. The probe has been explored as a potential chemosensor to detect Al³⁺ ions using a HEPES buffer (pH = 7.4) solution. Investigations of the fluorescence behaviour of this sensor in DMSO/H₂O (2 : 8, v/v) solution displayed a dramatic switch-on response only in the presence of Al³⁺, while other metal ions, like Li⁺, Na⁺, K⁺, Ag⁺, Ca²⁺, Mg²⁺, Mn²⁺, Ba²⁺, Cu²⁺, Ni²⁺, Co²⁺, Fe²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺, Sr²⁺, Fe³⁺ or Cr³⁺, have almost no influence on the fluorescence behaviour. Various common anions, such as ClO₄⁻, Cl⁻, or NO₃⁻ in the form of Al³⁺ salts [e.g. Al(ClO₄)₃, AlCl₃ or Al(NO₃)₃], had no influence on the fluorescence behaviour of the sensors. The detection limit for Al³⁺ is in the order of 10⁻⁶ M in DMSO/H₂O (2 : 8, v/v) HEPES buffer (pH = 7.4) solution. Notably, this is the first report of a dihydroindeno[1,2-b]pyrrole moiety acting as a sensor for the selective detection of Al³⁺ ions through an off–on fluorescence response. The potential of the probe was also confirmed by employing it for fluorescence bio-imaging with Al³⁺ on HepG2 cells.