One-pot synthesis of carbon dot-entrenched chitosan-modified magnetic nanoparticles for fluorescence-based Cu2+ ion sensing and cell imaging

Abstract

In this work, a new synthetic approach is developed for the synthesis of fluorescent magnetic nanoparticles which are explored for the detection of mostly abundant transition metal Cu²⁺ ions and cell imaging. These fluorescent magnetic nanoparticles are synthesized by decoration of carbon dots (CDs) on carboxymethyl chitosan-wrapped Fe₃O₄ nanoparticles (NPs) in a one-pot method. The fluorescent magnetic nanoparticles are characterized by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), a vibrating sample magnetometer (VSM), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), dynamic light scattering (DLS) and photoluminescence study. Importantly, the fluorescent magnetic nanoparticles exhibit excellent selectivity for the determination of Cu²⁺ ions over other metal ions. The fluorescence intensity was found to be successfully quenched by adding different concentrations of Cu²⁺ ions. Here, the reduction of fluorescence intensity proves the detection of Cu²⁺ ions in a linear range of 0.01–200 µM, with a detection limit of 0.56 µM at a signal-to-noise ratio of 3. The fluorescent magnetic nanoparticles were successfully applied to cell imaging and subsequently conjugated with folic acid for cancer cell imaging, which suggests that the synthesized nanoparticles have great potential for diagnostic purposes.