A new bio-compatible Cd2+-selective nanostructured fluorescent imprinted polymer for cadmium ion sensing in aqueous media and its application in bio imaging in Vero cells

Abstract

Cadmium is a very toxic element found in various aqueous samples. The majority of the highly selective fluorescent ligands, designed for cadmium ion sensing, are hydrophobic compounds, thus making them inactive in aqueous media. Fluorescent imprinted polymers, synthesized by the proficient combination of hydrophilic functional monomers and hydrophobic ligands, may give a new and highly selective opportunity for utilizing most fluorescent ligands for toxic metal ion sensing in aqueous media. A novel fluorescent Cd²⁺-imprinted polymer was synthesized based on the co-polymerization of a mixture of acryl amide, vinyl benzene and ethylene glycol dimethacrylate in the presence of a 5-((3-hydroxynaphthalen-2-yl)methylene)pyrimidine-2,4,6(1,3,5)-trione (HMPT)-Cd²⁺ complex. The polymer was characterized by FT-IR spectroscopy, scanning electron microscopy and thermogravimetric analysis. Cadmium ion recognition by IIP created a new emission peak at about 502 nm based on the ICT mechanism, which was different from the emission peak of IIP in the absence of Cd²⁺ (440 nm). The non-imprinted polymer showed a fluorescence emission at about 500 nm, which was not affected by Cd²⁺, highlighting the recognition sites of IIP. The opto-sensor (IIP) exhibited a dynamic linear response range of 10-0.05 μM with the limit of detection (LOD) and quantification (LOQ) of 12.3 and 41 nM, respectively. Also, the relative standard deviation (RSD) of 3 separate determinations was 3.68%. Moreover, the developed chemosensor was highly selective for Cd²⁺ since the IIP fluorescence was not affected by the presence of other metal ions such as Zn²⁺, Cu⁺, Mn²⁺, Co²⁺, Ni²⁺, and Pb²⁺. The synthesized IIP can be used as a fluorescent probe for cadmium detection in live cells because of its minor cytotoxic effect on them.