Sub-attomolar HIV-1 DNA detection using surface-enhanced Raman spectroscopy

A subattomolar HIV-1 DNA detection assay based on multilayer metal-molecule-metal nanojunctions (NJs) has been developed using surface-enhanced Raman spectroscopy (SERS). There is a two-step mechanism involved. First, label free target DNA facilitated the precipitation of Detection Unit I on the substrate through forming a sandwiched structure based on the capture probe, resulting in the first level amplification of target. Following that, the binding site on Detection probe I was further recognized by Detection Unit II. These two complementary probes acted as bricks to build up the multi-metal-molecule-metal NJs between Au nanoparticles (NPs) that not only created SERS "hot spots" by the conjugated Au NPs, but also obviously decreased the distance between Au NPs and Raman labels. Therefore, the Raman signal of the tag molecules on these detection probes was significantly enhanced due to the distance dependent electromagnetic enhancement (EM) of SERS. With regards to a HIV-1 DNA sequence, the platform could detect a concentration as low as 10(-19) M (approximately 10(-23) mol) with the ability of single base mismatch discrimination.