Plasmonic Metal–Insulator–Metal Capped Polymer Nanopillars for SERS Analysis of Protein–Protein Interactions (original) (raw)
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Plasmonic Biosensor Based on Vertical Arrays of Gold Nanoantennas
ACS Sensors, 2018
Implementing large arrays of gold nanowires as functional elements of a plasmonic biosensor is an important task for future medical diagnostic applications. Here we present a microfluidic-channel-integrated sensor for the label-free detection of biomolecules, relaying on localized surface plasmon resonances. Large arrays (~ 1 cm 2) of vertically aligned and densely packed gold nanorods to receive, locally confine and amplify the external optical signal, are used to allow for reliable biosensing. We accomplish this by monitoring the change of the optical nanostructure resonance upon the presence of biomolecules within the tight focus area above the nanoantennas, combined with a surface treatment of the nanowires for a specific binding of the target molecules. As a first application, we detect the binding kinetics of two distinct DNA strands as well as the following hybridization of two complementary strands (cDNA) with different lengths (25 and 100 bp). Upon immobilization, a redshift of 1 nm was detected; further backfilling and hybridization led to a peak shift of additional 2 nm and 5 nm for 25 and 100 bp, respectively. We believe that this work gives deeper insight into the functional understanding and technical implementation of a large array of gold nanowires for future medical applications.
Plasmonic Nanostructured Devices for Chemical and Biological Sensing
2005
The focus of this NIRT project is to investigate the fundamentals of plasmonic phenomena in nanoscale metallic structures and to explore the use of plasmonic chip technologies in biochemical sensing. We investigate metal nanoaperture arrays as a medium for effective interactions among photons, plasmons, and anlytes, and also as a base structure that provides wavelength-dependent transmission of light. The plasmonic interaction in chemically functionalized nanoaperture arrays offers a new strategy for massively parallel detection of chemical and biological analytes. Modulation of the nanoaperture array's optical response by adsorbed analytes is expected to offer improved sensitivity and selectivity over conventional surface plasmon resonance (SPR) methods, which are widely used and commercialized for analysis in detecting biological and chemical agents. The conventional SPR measurement usually involves bulky optics and high-precision mechanics for angular or wavelength interrogation of metal films in contact with analytes. As such, it is difficult to implement and automate the conventional SPR technique in compact instrumentation. We investigate a new approach to SPR sensing of biochemical agents by exploiting the recent breakthroughs in plasmonics that involve metallic nanostructures. The devices being developed in this program are amenable to miniaturization and integration with a photodetector chip so that chip-scale sensor arrays, which will enable massively parallel detection of many analytes and on-chip processing of information in the electronic domain. Research in the first year of this NIRT project has focused on investigating the fundamental physics of optical interactions in nanoapertured metal layers and on chemically modifying the metal surfaces for biochemical sensing.
Gold nanopillar array with sharp surface plasmon resonances and the application in immunoassay
Journal of Applied Physics
Nanoimprinting followed by metal deposition is a low-cost, high-throughput, and highly reproducible process for the fabrication of large-size plasmonic substrates required for commercial products. However, the plasmonic substrates prepared by the process usually have very broad surface plasmon resonances, which cannot be well reproduced by numerical simulations. The poor agreement between experiments and calculations has prevented the detailed analysis of the field enhancement behavior and the improvement of the performance as plasmonic substrates. In this work, we demonstrate that large-area plasmonic substrates with sharp surface plasmon resonances, which can be well reproduced by numerical simulations, are produced by sputter-deposition of gold (Au) on a commercially available nanoimprinted substrate. The good agreement between experiments and simulations allow us to identify the locations and field distributions of the hot spots. The angle dependence of specular reflectance and diffuse reflectance measurements in combination with numerical simulations reveal that a dipolelike bright mode and a higher-order dark mode exist at gaps between Au nanorods. Finally, we demonstrate the application of the developed plasmonic substrates for surface-enhanced fluorescence in sandwich immunoassays for the detection of influenza virus nucleoprotein. We show that the sharp resonance and the capability of precise tuning of the resonance wavelength significantly enhance the luminescence signal.
Designing Efficient Plasmonic Biosensors Based on Gold Metallic Nanostructures
Journal of nanotechnology and smart materials , 2023
The increasing need for plasmonic bio-sensing devices that require analytical platforms which are efficient, instant, extreme sensitivity, and real-time response, have yielded a significant change in the design them in recent years. The development of sensors based on plasmonic nanostructures has exhibited the best quality approach to integrate them in the lab-on-chip platforms with miniaturization and multiplexing. The main goal of this study was to design a highly sensitive nano-sensor based on metallic nanostructures and to investigate the effect of size and shape on the optical properties of metallic nanoparticles in very large spectral range (λ =500-1200 nm) using simulation for nanoparticles of sizes (D = 100-200 nm). In particular, the optical properties of gold nanoparticles were investigated using the Finite-Difference Time-Domain (FDTD) method. The wavelength corresponding to the maximum scattering redshifts (shift to longer wavelengths) were observed as the nanoparticle size increased. The influences of Au NP size and shape were analyzed in detail. The gold nanoparticle diameter between 100 nm to 200 nm is used in determine the shifting of the surface plasmon resonance. The results in this work indicated that the position of the plasmon resonance wavelength for gold nanoparticle was redshift when the size of gold nanoparticle was increased. Data was collected after designing the simulation of nanoplasmonic structures using Finite-Difference-in Time-Domain (FDTD) software. The major finding showed that adjusting of Au nanoparticles sizes/diameters and varying the sensing environment enhanced the resonance wavelength shift; this increased the sensitivity of Au nanoparticles. This study offers a new insight regarding biosensors based on plasmonic nanoparticles and it will provide opportunities for developing Plasmon-enabled applications in biomedicine.
Rational Selection of Gold Nanorod Geometry for Label-Free Plasmonic Biosensors
ACS Nano, 2009
We present the development of an analytical model that can be used for the rational design of a biosensor based on shifts in the local surface plasmon resonance (LSPR) of individual gold nanoparticles. The model relates the peak wavelength of light scattered by an individual plasmonic nanoparticle to the number of bound analyte molecules and provides an analytical formulation that predicts relevant figures-of-merit of the sensor such as the molecular detection limit (MDL) and dynamic range as a function of nanoparticle geometry and detection system parameters. The model calculates LSPR shifts for individual molecules bound by a nanorod, so that the MDL is defined as the smallest number of bound molecules that is measurable by the system, and the dynamic range is defined as the maximum number of molecules that can be detected by a single nanorod. This model is useful because it will allow a priori design of an LSPR sensor with figures-of-merit that can be optimized for the target analyte. This model was used to design an LSPR sensor based on biotin-functionalized gold nanorods that offers the lowest MDL for this class of sensors. The model predicts a MDL of 18 streptavidin molecules for this sensor, which is in good agreement with experiments and estimates. Further, we discuss how the model can be utilized to guide the development of future generations of LSPR biosensors.
Ultra-sensitive detection by metal nanoparticles-mediated enhanced SPR biosensors
Talanta, 2019
Surface plasmon resonance (SPR), as an optical technique, has widely been used for the detection of biomarkers. Various investigations have been conducted to address the impacts of SPR on the kinetics of biological interactions between the ligand and its cognate bio-element. Up until now, various biofunctionalized metal nanoparticles (NPs) have been used for the ultrasensitive detection of biomarkers in the enhanced SPR. The enhancement of plasmonic properties and refractive index using metal NPs in SPR-based biosensors have extremely resulted in the development of multimodal nanosystems used for the cancer diagnosis and monitoring. In all the enhanced SPR systems utilized for the direct/sandwich assay, each NP is covalently modified with the analyte molecules like antibody (Ab) or a nucleic acid such as DNA/RNA aptamer (Ap) capable of interaction with the related biomarker(s). The increasing of density near the gold surface and plasmonic coupling of gold film and NPs can provide a large shift in the 2 refractive index enhancing the plasmonic resonance because the SPR response unit is sensitive to the changing of refractive index and the mass shifting onto the chip surface. In this study, we review the potential applications of two major NPs for enhancing the SPR signals for the detection of molecular biomarkers, including gold and magnetic NPs.
Ultrahigh surface sensitivity of deposited gold nanorod arrays for nanoplasmonic biosensing
Applied Materials Today, 2021
The biosensing performance of plasmonic nanostructures critically depends on detecting changes in the local refractive index near the sensor surface, which is referred to as surface sensitivity. For biosensing applications at solid-liquid interfaces, recent effort s to boost surface sensitivity have narrowly focused on laterally isotropic nanostructures, while there is an outstanding need to explore laterally anisotropic nanostructures such as nanorods that have distinct plasmonic properties. Herein, we report the development of plasmonic gold nanorod (AuNR) arrays that exhibit ultrahigh surface sensitivity to detect various classes of biomacromolecular interactions with superior biosensing performance. A colloidal deposition strategy was devised to fabricate AuNR-coated glass substrates, along with experimental measurements and analytical calculations to investigate how nanorod dimensions and local dielectric environment affect plasmonic properties. To validate the sensing concept, real-time biosensing experiments involving protein adsorption and peptide-induced vesicle rupture were conducted and revealed that rationally tuning nanorod dimensions could yield AuNR arrays with the highest reported degree of surface sensitivity compared to a wide range of plasmonic nanostructures tested in past studies. We discuss plasmonic factors that contribute to this ultrahigh surface sensitivity and the measurement capabilities developed in this study are broadly extendable to a wide range of biosensing applications.
Journal of the American Chemical Society, 2009
Background on LSPR Sensing When the frequency of incident photons matches the collective oscillations of the conduction band electrons of noble metal nanoparticles, localized surface plasmon resonance (LSPR) occurs. 1-5 The result is a strong absorption band or multiple bands for metals such as Au and Ag in the visible region. The intensity and wavelength of the LSPR band depends on several factors, including the composition, size, and shape of the nanoparticles as well as the dielectric properties of the environment surrounding the metal and their local proximity to other metal nanoparticles. 1-5 There are three main types of sensing schemes based on the visible optical properties of metal nanoparticles. The first involves monitoring shifts in the LSPR band due to nanoparticle aggregation or changes in the nanoparticle-nanoparticle distance. This is usually performed with nanoparticles in solution, 6-9 but can be achieved in films. 10, 11 For example, researchers have detected polynucleotides, 6 proteins, 7, 9 solvents, 11 and metal ions 8, 10 through this scheme. Structural changes in DNA or other dynamic biophysical processes have also been probed by monitoring small changes in nanoparticle-nanoparticle distances optically, which is termed "molecular rulers". 12-14 A second approach involves using the nanoparticles as optical tags 15, 16 similar to fluorophores or other labels in an immunoassay or for cell imaging. 17, 18 In
Plasmonic Nanostructures for Biosensing Applications
2018
The aim of this work is the study, the design and the nanofabrication of innovative plasmonic nanostructured materials to develop label-free optical biosensors. Noble metalbased nanostructures have gained interest in the last years due to their extraordinary optical properties, which allow to develop optical biosensors able to detect very low concentrations of specific biomolecules, called analyte, down to the picomolar range. Such biosensors rely on the Surface Plasmon Resonance (SPR) excitation which occurs under specific conditions that depend both on the morphology of the nanostructure and on the adjacent dielectric medium. Therefore, the binding of the biomolecules to metal surfaces is revealed as a change in the SPR condition. Four kinds of nanostructures are investigated in this work: ordered and disordered nanohole array (o-NHA, d-NHA), nanoprism array (NPA) and nanodisk array (NDA). The o-NHA and d-NHA consist of a thin metallic film (50 - 100 nm) patterned with, respective...
Application of Gold Nanoparticle to Plasmonic Biosensors
International journal of molecular sciences, 2018
Gold nanoparticles (GNPs) have been widely utilized to develop various biosensors for molecular diagnosis, as they can be easily functionalized and exhibit unique optical properties explained by plasmonic effects. These unique optical properties of GNPs allow the expression of an intense color under light that can be tuned by altering their size, shape, composition, and coupling with other plasmonic nanoparticles. Additionally, they can also enhance other optical signals, such as fluorescence and Raman scattering, making them suitable for biosensor development. In this review, we provide a detailed discussion of the currently developed biosensors based on the aforementioned unique optical features of GNPs. Mainly, we focus on four different plasmonic biosensing methods, including localized surface plasmon resonance (LSPR), surface-enhanced Raman spectroscopy (SERS), fluorescence enhancement, and quenching caused by plasmon and colorimetry changes based on the coupling of GNPs. We be...