Abstract
The exploration of the plasmonic field enhancement of nanoprobes consisting of gold and magnetic core@gold shell nanoparticles has found increasing application for the development of surface-enhanced Raman spectroscopy (SERS)-based biosensors. The understanding of factors controlling the electromagnetic field enhancement, as a result of the plasmonic field enhancement of the nanoprobes in SERS biosensing applications, is critical for the design and preparation of the optimal nanoprobes. This report describes findings from theoretical calculations of the electromagnetic field intensity of dimer models of gold and magnetic core@gold shell nanoparticles in immunoassay SERS detection of biomarkers. The electromagnetic field intensities for a series of dimeric nanoprobes with antibody–antigen–antibody binding defined interparticle distances were examined in terms of nanoparticle sizes, core–shell sizes, and interparticle spacing. The results reveal that the electromagnetic field enhancement not only depended on the nanoparticle size and the relative core size and shell thicknesses of the magnetic core@shell nanoparticles but also strongly on the interparticle spacing. Some of the dependencies are also compared with experimental data from SERS detection of selected cancer biomarkers, showing good agreement. The findings have implications for the design and optimization of functional nanoprobes for SERS-based biosensors.
Highlights
Surface-enhanced Raman spectroscopy (SERS) is a powerful technique for bioassays with high sensitivity, high selectivity, and a low detection limit, which stems largely from the strong dependence of signal amplification
We recently demonstrated the combination of Au and magnetic core@Au shell nanoprobes for SERS detection of carcinoembryonic antigen (CEA) via conjugation of the nanoprobes with CEA-specific detection and capture antibodies [9]
A series of dimeric nanoprobes were examined in terms of nanoparticle sizes, core–shell sizes, and interparticle spacing
Summary
Surface-enhanced Raman spectroscopy (SERS) is a powerful technique for bioassays with high sensitivity, high selectivity, and a low detection limit, which stems largely from the strong dependence of signal amplification. A simple and effective strategy involves exploring Au nanoparticles (NPs) and magnetic core–gold shell NPs for effective coupling of magnetic and plasmonic properties in SERS detection of DNAs and cancer biomarkers [4,9,10,11]. A fundamental question for the “hot-spot” detection strategy is how the plasmonic field enhancement depends on nanostructural parameters such as particle core size, shell thickness, and, more importantly, the antigen/antibody sizes. We further studied the “hot-spot” characteristics based on a gold and core–shell NP dimer model [4] using various combinations of magnetic core–gold shell nanoparticles in the detection of cancer biomarkers (CEA, NSE, etc.). The results resultswere werealso alsocompared comparedwith with experimental data from nanoparticle-based detection of cancer biomarkers
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