Nitrogen-doped fluorescent carbon dots used for the imaging and tracing of different cancer cells

Abstract

Here, we report the synthesis of nitrogen-doped fluorescent carbon (C) dots using a one-pot hydrothermal method. Transmission electron microscopy results reveal that the particle size of the nitrogen-doped C-dots is very small, with an average diameter of 4.6 nm. After being kept in water for 10 days, the nitrogen-doped C-dots can still dissolve well in the water, showing good stability and compatibility in aqueous solution. The fluorescence spectra show that the nitrogen-doped C-dots exhibit emission-tunable color from blue to green upon excitation from 230 to 520 nm. Cell tests show that the C-dots are low in cytotoxicity and can be used for imaging, detecting and tracing between hepatoma and HeLa cells, because hepatoma and HeLa cells show different sensitivity to different fluorescent colors pumped at different excitation wavelengths.

Fig. 1. (a) XRD pattern, (b) TEM image, (c) size distribution, (d) high-resolution TEM image and elemental mapping of the as-prepared nitrogen C-dots.

Fig. 2. (a) UV-vis absorption (curve 1) and excitation spectra (curve 2) of the nitrogen C-dots; (b) fluorescence spectra of the nitrogen C-dots upon excitation in the range of 230–480 nm.

Fig. 3. (a) CIE chromaticity coordinates derived from the emission spectra in Fig. 2(b); (b) dependence of the emission intensity in terms of days (λ_ex = 380 nm) and digital fluorescent colors recorded by exciting with different wavelengths of light (inset).

Fig. 4. (a) Viability of HeLa cells after being cultured with 1.0 mg mL⁻¹ of C-dots for 48 h; (b) imaging patterns of HeLa cells upon excitation at 405 and 488 nm; (c) imaging patterns of hepatoma cells upon excitation at 405 and 488 nm; and (d) imaging patterns of HeLa-hepatoma cells upon excitation at 405 and 488 nm.