A label-free multifunctional nanosensor based on N-doped carbon nanodots for vitamin B12 and Co2+ detection, and bioimaging in living cells and zebrafish

Abstract

Multifunctional N-doped carbon nanodots (N-CNDs) with a fluorescence (FL) quantum yield (QY) of 13.6% have been synthesized via a facile one-step hydrothermal process using Artemisia annua and 1,2-ethylenediamine as precursors. As-prepared N-CNDs showed excellent FL properties and were developed as a multifunctional sensing platform for vitamin B₁₂ (VB₁₂) and Co²⁺ determination, and bioimaging in living cells and zebrafish. The FL of N-CNDs is quenched efficiently in the presence of VB₁₂ on the basis of the inner filter effect (IFE) or Co²⁺ by static quenching, respectively. EDTA as a masking agent enables Co²⁺ to be effectively eliminated and N-CNDs were used to selectively detect VB₁₂ in the presence of both VB₁₂ and Co²⁺. The present FL nanosensor can detect VB₁₂ and Co²⁺ in the linear ranges of 0.5–35 μM and 2.5–25 μM with the corresponding detection limits of 47.4 nM and 230.5 nM, respectively. The study proved that the determination of Co²⁺ was based on the static quenching to form a complex between the amino group of N-CNDs and Co²⁺. Inspired by these outstanding properties, practical applications of this nanosensor for the detection of VB₁₂ in actual samples (human serum, egg yolk, VB₁₂ tablets and VB₁₂ injection) and Co²⁺ in water samples were further verified with satisfactory results. The as-constructed N-CNDs have negligible toxicity and good biocompatibility, which facilitates utilization of N-CNDs in bioimaging of A549 cells and zebrafish, and sensing VB₁₂ in living cells.