Polarization-Based DNA Sandwich Assay with Au Nanoparticles using the Influence of Inter-Particle Distance

Abstract

Nucleic acid hybridization assay is widely used for application in biomedical research. In these field there is a considerable demand for the development of more sensitive, quantitative, rapid and low-cost method for target detection. To meet these requirements, Nanoparticle-based controlled assembly method via DNA has become a useful tool for clinical diagnostics because of their strict selectivity. Gold nanoparticles(AuNPs) can be synthesized amenably and can be made highly stable. Moreover, they have unique optical response of surface plasmon resonance and this property can be easily adjusted by varying their size, shape, and the surrounding chemical environment. In this research, we focus inter-particle distance of AuNP dimer. Inter-particle separations are greatly sensitive for the resonance wavelength and interaction between AuNP. When it is small(<2nm), it can be observed that specific optical response in occurred such as significantly high intensity scattering, peak shift of absorbance spectra.Recently, plasma mass spectrometry and surface enhanced raman spectroscopy(SERS) were reported as more sensitive method. However, they need sophisticated process and expensive instruments. Hence, We propose the method to use optical anisotropy and scattered light intensity as indices for accurate and robust discrimination between single AuNPs and dimers using single-particle polarization microscopy in aqueous solution. This method is called a direct light scattering(DLS) method. This is homogeneous, rapid low-cost, sensitive method. We tested several way to deduce distance between two AuNP in the step of fabricating AuNP dimers and evaluated these AuNPs to utilize DLS method in colloidal solution. In this presentation, we report the result and conclusion about the influence of inter-particle distance in our experiment.