Plasmonic biosensors and nanoprobes based on gold nanoshells

Abstract

Gold nanoshells (GNSs), consisting of a dielectric core coated with gold, have gained extensive attention as they show readily tunable optical properties and good biocompatibility. As highly sensitive and label-free optical biosensors with wide applications, GNSs have been investigated in many fields including drug delivery, immunoassay, cancer treatment, biological sensing and imaging. Taking advantage of the adjustability of the local surface plasmon resonance (LSPR) and the sensitivity of the surfaceenhanced Raman scattering (SERS) signal of GNSs, we have developed diverse applications including plasmonic biosensors and nanoprobes based on GNSs. In this review we introduce plasmonic and electromagnetic properties and fabrication methods of GNSs. We describe research progress in recent years, and highlight several applications of GNSs developed by our group. Finally we provide a brief assessment of future development of GNSs as plasmonic materials that can be integrated with complementary analytical techniques. With advances of technology, one-component materials can no longer meet the needs of society. Thus researchers have fabricated composite materials from two or more materials with complementary functions and optimization of performance [1][2][3][4]. In addition, nanomaterials of noble metals have gained widespread attention with their excellent physical and chemical properties and biocompatibility. Gold, as a typical representative of nanomaterials, has become the noble metal with the most dynamic research and development potential. Furthermore, novel core-shell structured nanomaterials with a variety of shapes, structures and/or controllable components have aroused intense interest in recent years. As a result, gold nanoshells (GNSs) have emerged as metal nanocomposite materials of great interest. GNSs containing a spherical dielectric core surrounded by an ultrathin, conductive gold layer not only offer superiority in performance but also great potential for developing simple, fast, and lowcost bioanalytical methods for biosensing and nanoprobes. As a new type of nanocomposite material, GNSs possess many notable features. Their linear optical properties, infrared extinction characteristics, photothermal conversion properties, acoustic properties, cavity absorption and electron dynamics characteristics, make GNSs a focal point of basic and applied research. In addition to tunable LSPR among other features, GNSs show a strong electromagnetic enhancement effect, which makes GNSs a potentially ideal active SERS substrate [5,6]. Research in this area has revealed many new phenomena and raised many new issues, and provided new principles and new methods for nano-characterization technology and sensor technology, which will lead to new types of ultra-high sensitivity sensors for LSPR and SERS. This paper will focus on the fabrication of GNSs and research progress in the field in chemical/biological sensing and surface-enhanced spectroscopy.

Facile synthesis of SiO2–Au nanoshells in a three-stage microfluidic system

“…4 Silica-gold nanoshells, first reported by Halas and co-workers, 3 have a high potential in biomedicine thanks to their biocompatibility and tunable optical properties in the near-infrared (NIR) region where body tissues and water present minimal absorption. 5 However, while most applications of nanoshells are focused on photothermal cancer therapy 6 other applications have been proposed, including surface-enhanced Raman scattering (SERS), 7 drug delivery, 8,9 waveguiding 10 and nanoprobes for sensing 11 and diagnosis. 12 Given the critical dependence of plasmonic properties on the relative dimensions of the core and shell in SiO 2 -Au structures, it is not surprising that considerable effort has been made to finetuning the variables of the synthesis process.…”

High-yield preparation of robust gold nanoshells on silica nanorattles with good biocompatiblity

“…The reason may be that a low concentration of colloidal gold caused a larger distance among the colloidal golds absorbed on the surface of SN. The diversities in the diameter and thickness of the nanoshells result in the broadening SPR absorption spectra [10]. This phenomenon is further confirmed by adding more SNs.…”

“…However, the use of gold nanoshells in clinic is still limited by the complicated synthesis method and structural stability. To date, gold nanoshells are often prepared by the widely used seed-mediated growth and the deposition-precipitation methods [10]. In the typical seed-mediated growth process, colloidal golds served as nucleation sites are firstly modified on the surface of silica, and then the Au nanoparticles grow gradually, forming a shell on the silica surface through a heterogeneous nucleation process.…”

Nanotechnological Methods of Antioxidant Characterization

“…As a result, although the absorbance of the SPR band of SiO 2 /AuNPs increased with H 2 O 2 concentration, the λ max showed a bathochromic rise (red shift) of ≈ 200 nm accompanying an increase in H 2 O 2 concentration from 20 to 200 μM (67), invalidating a fixed-wavelength calibration curve. A similar strategy based on the inhibition of H 2 O 2 -mediated growth of Au nanoshells on 3D ordered SiO 2 / AuNPs precursor nanocomposites as active SERS substrates was also used in other assays, where the hydrogen peroxide quenching ability of biochemically important compounds could be measured (69).…”