(316d) Surface-Enhanced Raman Spectroscopy (SERS) for Ultratrace Viral DNA Detection by Magnetically Concentrating Raman Active Gold Nanoparticles

A practical format for SERS bioassays is to use activated nanoparticles in solution. By performing the assay in solution, one can use high laser power to interrogate the sample without concern of burning the sample (as with solid-phase assays). Moreover, the biomolecules conjugated nanopaticles can be utilized to target pathogen DNA, Virus antigen with high efficiency. In our previous study, we report the demonstration of a SERS-based solution assay for the indirect capture of a viral DNA sequence using a target sequence derived from the West Nile Virus (WNV) genome. However, generally, solution-based assays are not very sensitive since the SERS particles are in low concentrations, not easily interrogated by a narrow laser beam, and freely adrift in solution.

In this study, we propose to overcome the shortcomings in Raman solution assay by developing methods to consistently fabricate highly active SERS reporter particles and to amplify the SERS signal (ie. increase analyte detection sensitivity) through an innovative paramagnetic capture method. A 53-mer sequence derived from the West Nile Virus (WNV) genome was chosen as the target DNA. Two DNA probes complementary to one-half of the target DNA were generated and conjugated to magnetic nanoparticles (MNPs) and Raman active gold nanoparticles (GNPs). After hybridization with target DNA, two nanoparticles form combination structures which can be magnetically collected and located. This concentrated combination of Raman Active gold nanoparticles and paramagnetic particles was will amplify the SERS signal in two ways: 1) by magnetic concentration of the bound analyte and Raman reporter tag and 2) by increasing the content of nanostructured Au and therefore increasing the probability of formation of SERS ?hot spots?. This concentration method will increase the types of sample matrices which can be examined. For example, very ?dirty? or highly dispersed samples can be assayed since the matrix material is eliminated from a magnetically concentrated spot positioned within the focal point of the interrogating laser.