Detection of Biomolecular Binding Through Enhancement of Localized Surface Plasmon Resonance (LSPR) by Gold Nanoparticles

To amplify the difference in localized surface plasmon resonance (LSPR) spectra of gold nano-islands due to intermolecular binding events, gold nanoparticles were used. LSPR-based optical biosensors consisting of gold nano-islands were readily made on glass substrates using evaporation and heat treatment. Streptavidin (STA) and biotinylated bovine serum albumin (Bio-BSA) were chosen as the model receptor and the model analyte, respectively, to demonstrate the effectiveness of this detection method. Using this model system, we were able to enhance the sensitivity in monitoring the binding of Bio-BSA to gold nano-island surfaces functionalized with STA through the addition of gold nanoparticle-STA conjugates. In addition, SU-8 well chips with gold nano-island surfaces were fabricated through a conventional UV patterning method and were then utilized for image detection using the attenuated total reflection mode. These results suggest that the gold nano-island well chip may have the potential to be used for multiple and simultaneous detection of various bio-substances

Plasmonic Nanostructures for Nano-Scale Bio-Sensing

The optical properties of various nanostructures have been widely adopted for biological detection, from DNA sequencing to nano-scale single molecule biological function measurements. In particular, by employing localized surface plasmon resonance (LSPR), we can expect distinguished sensing performance with high sensitivity and resolution. This indicates that nano-scale detections can be realized by using the shift of resonance wavelength of LSPR in response to the refractive index change. In this paper, we overview various plasmonic nanostructures as potential sensing components. The qualitative descriptions of plasmonic nanostructures are supported by the physical phenomena such as plasmonic hybridization and Fano resonance. We present guidelines for designing specific nanostructures with regard to wavelength range and target sensing materials

High figure of merit (FOM) of Bragg modes in Au-coated nanodisk arrays for plasmonic sensing

We report that gold-coated nanodisk arrays of nearly micron periodicity have high figure of merit (FOM) and sensitivity necessary for plasmonic refractometric sensing, with the added benefit of suitability for surface-enhanced Raman scattering (SERS), large scale microfabrication using standard photolithographic techniques and a simple instrumental setup. Gold nanodisk arrays were covered with a gold layer to excite the Bragg modes (BM) which are the propagative surface plasmons localized by the diffraction from the disk array. This generated surface-guided modes, localized as standing waves, leading to highly confined fields confirmed by a mapping of the SERS intensity and numerical simulations with 3D finite element method (3D FEM). The optimal gold-coated nanodisk arrays were applied for refractometric sensing in transmission spectroscopy with better performance than nanohole arrays and they were integrated to a 96-well plate reader for detection of IgY proteins in the nM range in PBS. The potential for sensing in biofluids was assessed with IgG detection in 1:1 diluted urine. The structure exhibits a high FOM of up to 46, exceeding the FOM of structures supporting surface plasmon polaritons (SPPs) and comparable to more complex nanostructures, demonstrating that sub-wavelength features are not necessary for high performance plasmonic sensing

Integrated Micro/Nanoengineered Functional Biomaterials for Cell Mechanics and Mechanobiology: A Materials Perspective

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106681/1/adma201304431.pd

Optical properties of nanometer disks, holes and rings prepared by colloidal lithography

The optical properties of nanostructures prepared by colloidal lithography are studied. Colloidal lithography is a fabrication approach based on a self-assembling pattern definition. An electrostatically self-assembled array of nanoparticles is used as a mask and combined with etching or deposition processes. The experimental conditions and procedures required to obtain well controlled particle films with short-range order are discussed. Technical issues addressed are related to either the particle adsorption from solution or drying of the resultant particle film to produce a mask. Specific parameters studied include the influence of salt concentration in the particle solution, the particle size, the particle polydispersity and the use of a binder layer. Colloidal lithography is a new, fast and relatively simple approach for fabrication of nanostructures, with potential for large area (cm2) coverage. Nanostructures can be produced with variable and well defined size, shape and interparticle distance. Optical extinction spectra for the disks, holes and rings, are measured. The spectra for disks and holes show similar peaks with positions, which is interpreted as excitation of localized surface plasmons on the disks and around the holes. The similarities in resonance energy are in agreement with electrostatic cylinder theory for complementary structures (solid cylinder / cylindrical void). The peak positions for rings are red-shifted. This can be explained as symmetric coupling between superimposed disk and hole plasmon modes, lowering the resonance energy. In the short-range ordered arrays (lacking long-range order), we find no evidence for plasmon coupling for particles, while coupling through the gold film gives a blue-shift for hole arrays. The colloidal lithography fabrication approach and the optical results have relevance for, for example, the development of miniaturized biosensors

Optical properties of nanometer disks, holes and rings prepared by colloidal lithography

The optical properties of nanostructures prepared by colloidal lithography are studied. Colloidal lithography is a fabrication approach based on a self-assembling pattern definition. An electrostatically self-assembled array of nanoparticles is used as a mask and combined with etching or deposition processes. The experimental conditions and procedures required to obtain well controlled particle films with short-range order are discussed. Technical issues addressed are related to either the particle adsorption from solution or drying of the resultant particle film to produce a mask. Specific parameters studied include the influence of salt concentration in the particle solution, the particle size, the particle polydispersity and the use of a binder layer. Colloidal lithography is a new, fast and relatively simple approach for fabrication of nanostructures, with potential for large area (cm2) coverage. Nanostructures can be produced with variable and well defined size, shape and interparticle distance. Optical extinction spectra for the disks, holes and rings, are measured. The spectra for disks and holes show similar peaks with positions, which is interpreted as excitation of localized surface plasmons on the disks and around the holes. The similarities in resonance energy are in agreement with electrostatic cylinder theory for complementary structures (solid cylinder / cylindrical void). The peak positions for rings are red-shifted. This can be explained as symmetric coupling between superimposed disk and hole plasmon modes, lowering the resonance energy. In the short-range ordered arrays (lacking long-range order), we find no evidence for plasmon coupling for particles, while coupling through the gold film gives a blue-shift for hole arrays. The colloidal lithography fabrication approach and the optical results have relevance for, for example, the development of miniaturized biosensors