Surface Enhanced Raman Spectroscopy Sensor Based on Magnetic Beads-induced Nanoparticles Aggregation for Detection of Bacterial Deoxyribonucleic Acid

Abstract

Abstract A novel method was developed for the highly sensitive detection of bacterial DNA by surface-enhanced Raman spectroscopy (SERS) with 5,5′-dithio-bis(2-nitrobenzoic acid) (DTNB)-modified gold nanoparticles as reporter probes and on the basis of the separation and enrichment effect of magnetic beads and the high affinity of fully complementary hybridization of DNA strands. Capture probe was immobilized onto the surface of Streptavidin-enwrapped magnetic beads (SA-MB) through the force between biotin and avidin, which hybridized with the target bacterial DNA sequence partly, and the remaining connected with the report probe decorated AuNPs with DTNB and SH-DNA (AuNPs@DTNB@DNA). Compared with previous methods, this design shortened the distance between particles by the aggregation effect of the magnetic beads to nanoparticles, and produced the plasma resonance coupling effect, which increased the SERS signal significantly. The results showed that, under the optimized conditions, the concentration of DNA in the range from 5 pM to 5 nM performed a good linear relationship with Raman intensity. The limit of detection (LOD) for bacterial DNA was estimated to be about 5 pM, showing a certain selectivity. The method was simple in design with low cost, also it was used in the sensitive and selective detection of bacterial DNA.