Guanidine-based dual-responsive ‘turn on’ fluorometric probes for the selective detection of Zn2+ cations and F− anions: spectral and theoretical investigations, smartphone assisted colorimetric detection, and applications in bio-imaging of the Artemia salina animal model and molecular logic gate operation

Abstract

Two dual-responsive probe molecules 1,3-bis(5-bromo-2-hydroxyphenylmethylideneamino)guanidine hydrochloride (P1) and 1,3-bis(3-ethoxy-2-hydroxyphenylmethylideneamino)guanidine hydrochloride (P2) have been synthesized for the detection of inorganic ions in solution at room temperature. These dual-responsive sensor molecules showed colorimetric responses toward Cu²⁺ and Fe³⁺ cations and the F⁻ anions and also demonstrated the ‘turn on’ fluorometric responses to the Zn²⁺ cations and the F⁻ anions in CH₃CN : DMSO (9 : 1, v/v) solution. The probe molecules demonstrated reversible binding to Zn²⁺ cations in the presence of EDTA, thus enhancing their versatility. The smartphone-based RGB analysis validated the rapid colorimetric on-site detection of Zn²⁺ cations using probe coated test strips. The density functional theory calculations elucidate the nature of interaction between the probe molecules and the sensed ions. The probes were successfully employed for the in vitro bio-imaging of Zn²⁺ and F⁻ ions in HaCaT and MDA-MB-231 cell lines and in vivo bio-imaging in Artemia salina nauplii. Furthermore, the probe molecules have been employed for the construction of an INHIBIT molecular logic gate operation.