Sensitive CVG-AFS/ICP-MS label-free nucleic acid and protein assays based on a selective cation exchange reaction and simple filtration separation

Abstract

Nowadays, label-free atomic spectrometric bioassays are attracting great research interest because of their advantages of low cost, simple design and operation, etc. Herein, a novel and simple chemical vapor generation-atomic fluorescence spectrometry (CVG-AFS)/inductively coupled plasma-mass spectrometry (ICP-MS) label-free detection method is presented for highly sensitive and selective assay of DNA and proteins. This work mainly combined a phenomenon that CdTe quantum dots (QDs) can be used to selectively differentiate free Hg²⁺ and the T–Hg²⁺–T complex, with the use of simple membrane filtration separation to improve the performance of the label-free bioassay methods. Upon hybridization with the DNA/protein (carcinoembryonic antigen, CEA) target, the T–Hg²⁺–T hairpin structure was opened and Hg²⁺ was released; this initiated the cation exchange reaction between Hg²⁺ and CdTe QDs which released Cd²⁺ simultaneously. Subsequently, the free Cd²⁺ was separated by the filtration membrane without separating the CdTe QDs, which could then be separated from the sample matrices for the CVG-AFS/ICP-MS assay. Under the optimal conditions, this method possessed high sensitivity for DNA and CEA determination with limits of detection (LODs) of 0.2 nM and 0.2 ng mL⁻¹, and linear dynamic ranges of 1–160 nM and 0.5–20 ng mL⁻¹, respectively, and exhibited excellent DNA sequence specificity and protein selectivity. This method preserves the advantages of the label-free atomic spectrometric bioassay, and combined with the selective cation exchange reaction and simple filtration separation to improve the performance.