Label-free selective detection of coralyne due to aptamer–coralyne interaction using DNA modified SiO2@Au core–shell nanoparticles as an effective SERS substrate

Abstract

A label-free approach to the detection of coralyne using aptamer modified silica–Au/core–shell nanoparticles (denoted as SiO₂@Au core–shell nanoparticles) through surface enhanced Raman scattering (SERS) spectroscopy was proposed. The silica–Au/core–shell colloids were synthesized and immobilized on a quartz substrate, and a single-stranded DNA (ssDNA) oligonucleotide designed as an aptamer for coralyne, namely, 5′-SH-(CH₂)₆-AAAAAAAAAAAAAAAA-3′, was covalently attached onto the Au nanoshells. The aptamer, with one end on the Au surface, changed conformation upon conjugation with target coralyne, which correspondingly caused changes in the intensity of the Raman band at 1376 cm⁻¹ and the ratio of the Raman intensity at 736 cm⁻¹ to the Raman intensity at 1319 cm⁻¹. The intensity ratio increased with the amount of coralyne added, which therefore allowed the measurement coralyne in a selective and quantitative way, reaching a detection limit as low as 0.1 µM.