A Label-free “Lock-key” Fluorescence Aptasensing Based on Triplex-helix DNA and G-quadruplex for CA15-3 Detection

Abstract

Herein, we designed a label-free fluorescent aptasensor based on triple-helix DNA and G-quadruplex for carbohydrate antigen (CA15-3) detection. Triplex-helix structure can be formed with Insert G-rich DNA (IG) and Aptamer DNA (Apt), which likes a "lock" and the G-rich sequences are locked. The CA15-3 was the "key", which specifically combined with aptamer sequences of Apt, causing IG liberated from the triplex-helix "lock". Hereafter, the G-rich sequences of IG were formed into G-quadruplex and specifically interacted with N-methylmesoporphyrin IX (NMM), which greatly enhanced fluorescence of the solution. However, when the "key" was not existing, the "lock" would be fastened and fluorescence intensity didn't change. According to this proposal, the concentration of CA15-3 can be effectively detected from 0.01 U mL-1 to 5 U mL-1 with a detection limit (LOD) of 0.01 U mL-1. Furthermore, this proposal can be applied to spiked human serum with great precision and reproducibility.

Mass spectrometry-based techniques for single-cell analysis

“…Finally, the separation was carried out according to different mass to charge ratios by using a mass spectrometer. 101,102 ICP-MS has the advantages of high precision, sensitivity and accuracy, a wide linear range, multi-element measurement capability, and isotopic analysis capability. 103 It is also used for single-cell analysis and the identification of ppb-scale nanoparticle concentrations, particle size, and particle size distribution.…”