Fabrication of homogeneous plasmonic nanoparticles for highly sensitive SERS-based immunoassay

Abstract

Fabrication of homogeneous and stable nanoparticles is very important for many biological applications. The shape and physiochemical properties of metal nanoparticles play a vital role in quantitative analysis and detection of a target marker. Surface Enhanced Raman Scattering (SERS) is a highly sensitive and powerful technique which is based on the inelastic scattering of light from the surface of noble metal nanoparticles. To achieve highly reproducible SERS signals, we tried to fabricate homogenous and uniform nanoparticles with highly reproducible signal enhancement. Here, we fabricated gold nanoparticles (AuNPs) by two different methods; one is a kinetically controlled-seeded growth synthesis method and the other is a conventional single-phased citrate reduction method. Then two different types of AuNPs were evaluated to confirm whether they are suitable for highly sensitive SERS-based immunoassay detection. For highly sensitive immunoassay detection, we chose a two-dimensional gold-patterned microarray substrate as the template to perform SERS-based immunoassay. In order to compare their reproducibility, we measured their SERS mapping images. Herein, using the Raman spectrum of reporter molecule, we aimed to obtain the images of homogeneous hot spots for nanoparticles. Through the SERS mapping images, we have clearly shown that seeding-growth synthesis method ensures the formation of more homogeneous AuNPs with identical size distribution, having reproducible signal intensity as compared to conventional single-phased synthesis method. The error data obtained from Raman spectra showed that kinetically controlled seeded-growth synthesis method ensures homogeneous nanoparticles with reproducible SERS signal enhancement as compared to conventional single- phased citrate reduction method.