Nanoscale graphene oxide-induced metallic nanoparticle clustering for surface-enhanced Raman scattering-based IgG detection

Abstract

Surface-enhanced Raman scattering (SERS) has been of great interest to advance sensitive optical biosensors. Clustered metallic nanoparticles as SERS nanoprobes are important to detect specific biomolecules with ultra-sensitivity. We report herein that the cluster formation of gold nanoparticles (GNPs) was induced by nanoscale graphene oxides (NGOs) with 120nm to develop a new class of SERS nanotags for biosensing. The GNPs with 4-mercaptopyridine as a Raman reporter were modified with 1-pyrenemethylamine to introduce hydrophobic moieties on the surfaces and were complexed with NGOs via noncovalent interactions of π-π stacking and van der Waals interactions, resulting in the formation of NGO-GNP clusters (NGO-GNPCs). The NGO-GNPCs increased the SERS signal 3- to 4-fold higher than that of the individual GNPs due to enhancement of the electromagnetic field at the interstices of the GNPs. As a proof of concept, the NGO-GNPCs as SERS nanoprobes and magnetic beads (MBs) were developed to detect immunoglobulin G (IgG). Sandwich-type immunocomplexes of the NGO-GNPCs, IgG, and MBs were formed, representing a linear correlation between Raman intensity and IgG concentration, and a limit of detection of 0.6 pM. It suggests that the NGO-GNPCs as SERS nanoprobes could open a new avenue for highly sensitive SERS-based biosensing.