SYBR Green I and DNA-modulated charge neutralization assembly of naked AuNPs for fast colorimetric sensing of Cd2+ in cosmetics

Abstract

The involvement of cadmium in cosmetics results in inevitable exposure to our daily life. Therefore, it is of great significance to develop a simple and rapid method for fast screening of cadmium in cosmetics. Gold nanoparticles (AuNPs)-based colorimetric sensing offers a simple strategy for analytical detection, but the typical surface functionalization of AuNPs adds complexity to the overall detection. Nucleic acid dye-based charge neutralization offered a truly simple and fast approach for the assembly of AuNPs over the conventional salt-induced strategy. Herein, we developed a simple colorimetric sensing system for Cd2+, based on nucleic acid dye SYBR Green I (SG) and Cd2+ aptamer (Cd-2-1)-modulated charge neutralization assembly of naked AuNPs. The method rationale was based on the higher affinity of Cd2+ to Cd-2-1 DNA over SG, as well as the stable and fast charge neutralization-induced assembly of AuNPs by SG. The limit of detection (LOD) of the proposed method was 0.27 μM, which was substantially lower than the maximum permitted amount of Cd2+ in cosmetics regulated by the Chinese Food and Drug Administration (CFDA, 5 mg/kg, equivalent to 4.45 µM in our assay). Successful exploration of the proposed method was demonstrated for the detection of Cd2+ in cosmetics.