Sensitive and Selective in Vitro Recognition of Biologically Toxic As(III) by Rhodamine Based Chemoreceptor

Arsenic
induced cleavage of the spirolactam ring of a cleft shaped
electronically enriched rhodamine based chemoreceptor molecule 3′,6′-bis­(ethylamino)-2-((2-hydroxy-5-methylbenzylidene)­amino)-2′,7′-dimethylspiro­[isoindoline-1,9′-xanthen]-3-one
(PBCMERI-23) has been reported in the present work. The developed easy, instant and economic luminescent probe instigate toward
unlocking the selectivity for a specific lethal water contaminant
such as As­(III) from aqueous media up to a level of 0.164 ppb (beyond
the critical limit of the World Health Organization). PBCMERI-23 displays
a 2-fold optical response (chromogenic, colorless to reddish pink;
fluorogenic, non-blooming fluorescence to yellow emission) via the
ring opening phenomenon of the developed chemoreceptor. Owing to the
remarkable photophysical and structural properties of the synthesized
probe, the recognition event has been turned on in
the low energy region. Detailed experimental techniques further supported
by theoretical evidence establishes the plausible mechanistic course
of the host:guest interaction. The spectrophotometric response of
the developed chemoreceptor PBCMERI-23 turns out to be reversible
with incremental addition of a stoichiometric amount of I–. The optical recognition phenomenon has been further synchronized
and interfaced with molecular logic gate to molecular electronics.
To explicate the bioapplicability of PBCMERI-23, varying cell lines, viz., pollen grains of Allamanda puberula (Aapocynaceae), radiator plant (Peperomia pellucida), Poecilia reticulata, Danio rerio, and squamous epithelial cells have been monitored. The probe displays
sparkling yellow illumination when the cells were visualized under
fluorescence microscope, which confirms its cell permeability and
is a biomarker toward intracellular investigation and bio-imaging
of As­(III). Furthermore, the chemoreceptor has enormous capability
in detecting As­(III) from a series of wastewater specimens with varying
pH, which makes the present chemoreceptor PBCMERI-23 unique of its
kind.