Dual platform based sandwich assay Surface-enhanced Raman scattering DNA biosensor for the sensitive detection of food adulteration
Surface enhanced Raman scattering (SERS) DNA biosensing is an ultrasensitive, selective, and rapid detection technique due to its ability to produce molecule specific distinct fingerprint spectra. It supersedes the long amplicon based PCR assays, fluorescence and spectroscopic techniques by the quenching ability and narrow spectral bandwidth, and electrochemical detection techniques by the multiplexing capability. However, the performance of the SERS DNA biosensor relies on the DNA probe length, platform composition, presence and position of Raman tags and the chosen sensing strategy. In this context, herein we report a SERS biosensor based on dual nanoplatforms, and a uniquely designed Raman tag (ATTO Rho6G) intercalated short-length DNA probe for the sensitive detection of the pig (Sus scrofa) species. In the design of signal probe (SP), Raman tag was incorporated adjacent to the spacer arm followed by a terminal thiol modifier, which consequently had a strong influence on the SERS signal enhancement. The detection strategy involves the probe-target DNA hybridization mediated coupling of the two platforms, i.e. graphene oxide-gold nanorod (GO-AuNR) functionalized capture probe (CP) and SP conjugated gold nanoparticles (AuNPs), hence the consequent enhancement of SERS intensity by the electromagnetic hot spots generated at the junction or interstices of two platforms and chemical enhancement between the AuNPs and adsorbed intercalated Raman tag. This dual platform based SERS DNA biosensor exhibited an outstanding sensitivity in detecting pork DNA with a limit of detection (LOD) of 100 aM as well as validated with DNA extracted from pork sample (LOD – 1fM). Moreover, the fabricated SERS biosensor showed an outstanding selectivity and specificity to differentiate the DNA sequences of the closely related six non-target species and the target DNA sequences with single and three nucleotide base-mismatches. Therefore, the developed short-length DNA linked dual platform based SERS biosensor could replace the less sensitive traditional methods of pork DNA detection, and be adopted as a universal detection approach for the qualitative and quantitative detection of DNA from any sources.