Assessing Interparticle Spatial Characteristics of DNA-Linked Core–Shell Nanoparticles with or without Magnetic Cores in Surface Enhanced Raman Scattering

Abstract

Surface-enhanced Raman scattering (SERS) of plasmonic nanoparticles enables their use as nanoprobes for the detection of biomolecules in solutions, which exploits the “hot-spot” arisen from small aggregates of the biomolecule-linked nanoprobes for effective harnessing of the interparticle plasmonic coupling of gold nanoparticles. While a “squeezed” interparticle spatial characteristic has been revealed from the duplex DNA-linked gold nanoparticles as dimers in solution, how this interparticle spatial characteristic is operative for plasmonic nanoparticles containing magnetic components remains unknown. We describe herein new findings of an investigation of the interparticle spatial characteristics of DNA-linked core–shell type nanoparticles consisting of magnetic cores and plasmonic gold or silver shells, focusing on theoretical–experimental correlation in terms of localized surface plasmon resonance and electromagnetic field enhancement. While the simulated enhancement for the DNA-linked dimers of plasmonic magnetic core–gold shell nanoprobes shows an agreement with the experimental data in terms of the squeezed interparticle spacing characteristic, it does not seem to show an agreement between the simulated and experimental results for the dimers involving magnetic core–silver shell nanoprobes. Instead, an agreement was revealed by simulations of the DNA-linked dimers of the nanoprobes at an interparticle spacing of essentially zero. This finding was analyzed in terms of effective thickness of DNA layers on the nanoparticles and the strong magnetic attraction for the core–shell nanoprobes, providing new insight into the control of core composition and shell structure in optimizing the plasmonic coupling and spectroscopic enhancements for SERS-based biomolecular detection.

Magnetic Nanoparticles for Nanomedicine

“…An excellent CEA detection limit, LOD = 0.1 pM, has been obtained. Experimental and theoretical assessments of the high field spots formed in the interparticle area in a particle dimer bound via DNA duplex linkages have recently been performed for Au-or Ag-coated magnetite SPIONs [24].…”

“…The nanocarriers must also be able to release the drugs under specific local conditions (acidity, GSH level) [50][51][52] or under external stimuli, such as a light pulse, an X-ray signal, or a heat wave. The novel nanocarriers now include also functionalized magnetic core-based NPs [3,6,7,[53][54][55], where the magnetic core is protected against degradation in biological environments by coating with a silica shell [23], gold film [24], a tight polymeric coat (e.g., PEG, poly-L-lysine, carboxydextran) [16], or a dense self-assembled monolayer of impenetrable ligands [25]. The protective shell provides also an easy means for the attachment of drugs, adjuvants, targeting ligands, and agents ensuring the nanocarrier biocompatibility [53,54,56].…”

“…Generally, all MNPs, even the most stable ones, require some kind of a protection against the biological environment [15]. Thus, coatings of MNPs may include silica shells [23], gold film [24], polymer coats [16], or a dense self-assembled monolayer of impenetrable ligands [25].…”

Localized Surface Plasmon Resonances with Spherical Metallic Nanoparticles

“…Localized surface plasmon resonance (LSPR) is known to be responsible for the electrical intensity enhancement, which determines the optical and spectroscopy properties and has led to advances in several areas of the science and technology such as nano-scale sensing and modern analytical techniques based on spectroscopy applications [1][2][3][4][5][6][7][8][9]. These resonances, associated with noble metallic nanostructures, create sharp spectral absorption and scattering peaks as well as strong near-field enhancement of the electromagnetics.…”

“…These resonances, associated with noble metallic nanostructures, create sharp spectral absorption and scattering peaks as well as strong near-field enhancement of the electromagnetics. Among these is the detection of molecules interactions near the particle surface through shifts in the LSPR spectral peak, namely surfaceenhanced Raman spectroscopy (SERS) [3][4][5][6][7][8][9]. The formation of inter-particle of noble metallic nanoparticles in the dielectric medium constitutes the basis for inter-particle plasmonic coupling responsible for SERS signal amplification, but understanding of its correlation with inter-particle spatial properties, particle sizes and the refractive indices of the surrounded media, remains elusive.…”