Localized Surface Plasmon Resonance System Research Articles

Multi-channel prismatic localized surface plasmon resonance biosensor for real-time competitive assay multiple COVID-19 characteristic miRNAs

A multi-channel prismatic localized surface plasmon resonance (LSPR) biosensor was developed for quantitative and real-time detection of multiple COVID-19 characteristic miRNAs. The well-dispersed and dense gold nanoparticles (AuNPs) arrays for LSPR biosensing were fabricated through a nano-thickness diblock copolymer template (BCPT). Both theoretical and experimental analyses were conducted to investigate the effects of particle size, interparticle spacing, and surface coverage on LSPR sensing spectrum and intensity sensitivity of varied AuNPs sizes. A competitive assay strategy was proposed and used for non-amplification miRNA detection with a low limit detection of 3.41 nM, while a four-channel prismatic LSPR system enables parallel detection of multiple miRNAs. Furthermore, this sensing strategy can effectively and specifically identify target miRNA, distinguish mismatched miRNA and interfering miRNA, and exhibit low non-specific adsorption. This BCPT-based LSPR biosensor demonstrates the practicality and potential of a multi-channel, adaptable, and integrated prismatic sensor in medical testing and diagnostic applications.

Design of experiment (D.O.E) by Taguchi model for optimization of different process parameters for LSPR system to detect VCO adulteration

Virgin coconut oil (VCO) being one of the costly oils is prone to be adulterated with cheaper oils viz., coconut oil (CO). Attempt were made to develop a new innovative way to detect the adulteration in VCO using Localized surface plasmon resonance (LSPR) system. Optimization of certain process parameters is an prioritize criteria for detection by LSPR system for further development of the calibration curve. The traditional method for optimization involved the study of one variable at a time, which in turn required a large number of experimental runs. The Design of experiments (D.O.E) by Taguchi design employed here for optimization of LSPR system to achieve maximum reliability with a minimum experimental run. The process parameters viz., flowrate, surfactant and pH were selected for the optimization of the LSPR system to detect the VCO adulteration with CO in PBS buffer. For obtaining a maximum response a large signal to noise ratio was applied. An optimal condition for LSPR system was obtained at a Flowrate (200µl/min), pH (7.0) and surfactant (Tween 20) with a significant difference (p

Computational Guided Method Applied to LSPR‐Based Biosensor for Specific Detection of the Four‐Serotypes of Dengue Virus in Seropositive Patients

AbstractIn this paper, a localized surface plasmon resonance (LSPR)‐based biosensor, computationally guided to detect selectively the four Dengue virus (DENVx) serotypes in seropositive patients, is presented. The behavior of gold nanoparticles in the shape of nanorods is theoretically and numerically studied as a function of induced structural variations, which are experimentally evidenced due to the bio‐interaction between the target analytes and its surface during the detection process. Additionally, with the implementation of the largest Lyapunov exponent, it is possible to calculate the notion of predictability for the experimental results, observing chaotic systems with a very low probability of repetition. Due to the above, when analyzing the recurrence map associated with the obtained resonance curve generated by the LSPR system, the genetic similarity of DENV3/DENV2 and DENV4/DENV1 is evidenced. Finally, the biosensors are validated by analyzing samples of seronegative patients for DENVx and seropositive ones for other Flaviviruses such as Zika virus, Yellow Fever virus, and Saint Louis Encephalitis virus.

Peptide Specific Nanoplastic Detection Based on Sandwich Typed Localized Surface Plasmon Resonance

Recently, various waste microplastics sensors have been introduced in response to environmental and biological hazards posed by waste microplastics. In particular, the detrimental effects of nano-sized plastics or nanoplastics have been reported to be severe. Moreover, there have been many difficulties for sensing microplastics due to the limited methodologies for selectively recognizing nanoplastics. In this study, a customized gold nanoparticles (Au NPs) based localized surface plasmon resonance (LSPR) system having bio-mimicked peptide probes toward the nanoplastics was demonstrated. The specific determination through the oligo-peptide recognition was accomplished by chemical conjugation both on the LSPR chip’s 40~50 nm Au NPs and sandwiched 5 nm Au NPs, respectively. The peptide probe could selectively bind to polystyrene (PS) nanoplastics in the forms of fragmented debris by cryo-grinding. A simple UV-Vis spectrophotometer was used to identify the LSPR sensing by primarily measuring the absorbance change and shift of absorption peak. The sandwich-binding could increase the LSPR detection sensitivity up to 60% due to consecutive plasmonic effects. In addition, microwave-boiled DI water inside of a styrofoam container was tested for putative PS nanoplastics resource as a real accessible sample. The LSPR system could be a novel protocol overcoming the limitations from conventional nanoplastic detection.

A multi-channel localized surface plasmon resonance system for absorptiometric determination of abscisic acid by using gold nanoparticles functionalized with a polyadenine-tailed aptamer.

A multi-channel localized surface plasmon resonance system is described for absorptiometric determination of abscisic acid (ABA). The system is making use of gold nanoparticles and consists of a broadband light source, a multi-channel alignment device, and a fiber spectrometer. The method is based on the specific interaction between an ABA-binding aptamer and ABA. This induces the growth of gold nanoparticles (AuNPs) functionalized with a polyadenine-tailed aptamer that act as optical probes. Different concentrations of ABA give rise to varied morphologies of grown AuNPs. This causes a change of absorption spectra which is recorded by the system. ABA can be quantified by measurement of the peak wavelength shifts of grown AuNPs. Under optimized conditions, this method shows a linear relationship in the 1nM to 10μM ABA concentration range. The detection limit is 0.51nM. The sensitivity of the ABA assay is strongly improved compared to the method based on salt-induced AuNP aggregation. This is attributed to the use of a poly-A-tailed aptamer and the catalytic ability of AuNPs. In the actual application, the ABA concentration of ABA in fresh leaves of rice is measured with the maximum relative error of 8.03% in comparison with the ELISA method. Graphical abstractSchematic representation of an absorptiometric approach for determination of abscisic acid based on the growth of polyA-tailed aptamer-AuNPs probes and a multi-channel localized surface plasmon resonance system.

Localized surface plasmon resonance biosensor: an improved technique for SERS response intensification.

As technology continues to advance, the development of novel sensing systems opens new possibilities for low-cost, practical biosensing applications. In this Letter, we demonstrate a localized surface plasmon resonance system that combines both wave-guiding and plasmonic resonance sensing with a single microstructured polymeric structure. Characterizing the sensor using the finite element method simulation shows, to the best of our knowledge, a record wavelength sensitivity (WS) of 111000 nm/refractive index unit (RIU), high amplitude sensitivity (AS) of 2050 RIU-1, high sensor resolution and limit of detection of 9×10-7 RIU and 8.12×10-12 RIU2/nm, respectively. Furthermore, these sensors have the capability to detect an analyte within the refractive index range of 1.33-1.43 in the visible to mid-IR, therefore being potentially suitable for applications in biomolecular and chemical analyte detection.

Effect of graphene layer on the localized surface plasmon resonance (LSPR) and the sensitivity in periodic nanostructure

We study the interaction of gold nanoparticles with a graphene film. Graphene is used as a spacer, as thin as possible, between the gold nanoparticles and the detection dielectric medium, and one of the advantages of graphene is to protect the structure, which allows to avoid the oxidation of nanoparticles. We focus our study on the variation of the resonant structure (LSPR) depending on the thickness of the graphene layer (0.34–5 nm). A stronger resonance behavior of positions in the absorption spectrum shows a strong coupling between the LSP on gold nanoparticles and the covering film. Numerical simulations indicate a significant shift of the resonance wavelength structure SiOx/AuNPs/Graphene/SiOx (657.90 nm) compared with experimental results obtained on SiOx/AuNPs/SiOx (574.71 nm) and optimized for the required parameters proposed LSPR system we achieve the highest detection sensitivity range, while the location of points of the electric field on the best corners of the gold-graphene nanoparticles.

LSPR Cuvette for Real-Time Biosensing by Using a Common Spectrophotometer

Although localized surface plasmon resonance (LSPR) transducers can be optically interrogated without the need of light couplers, normally they need tailor-made optical assemblies for signal monitoring. This fact limits the application of LSPR biosensors in laboratories due to lack of specific optical setups. If commercial equipment like common spectrophotometers were suitable for LSPR interrogation, the LSPR technology could be applied more often in detection applications. In this paper, a universal LSPR cuvette has been developed in order to use a commercial spectrophotometer as a real-time biosensor without the need of any extra optical component. By measuring the changes in absorbance at constant wavelength, the equipment provides sensograms where real-time response is monitored. The cuvette, fully compatible with spectrophotometers, is an LSPR flow-cell (volume less than 10 mL) where a gold nanopatterned surface is emplaced as a window. Gold nanopatterns (period 600 nm) based on lines and pillars were simulated, fabricated, measured, and compared. The resolutions of $1.8\cdot 10^{-4}$ and $6.7\cdot 10^{-5}$ refractive index units were found for nanolines and nanopillars, respectively. The label-free detection of an antibody (anti-IgG) was carried out in the LSPR system with a limit of detection of 1.9 nM. The biosensing protocol was rapid and reproducible and allows the reuse of the surface for multiple sample measurements. The achieved analytical features are comparable with other reported LSPR sensors with tailor-made optical setups. These results indicate that the system (LSPR $\text {cuvette} + \text {spectrophotometer}$ ) can be a useful analytical tool to biosensing applications.

Optimization of Nanoporus Anodic Aluminum Sensor-Based Lspr for Methicillin-Resistant Staphylococcus Aureus detection

Methicillin-resistant Staphylococcus aureus (MRSA) causes foodborne illnesses in approximately 241,000 persons in the United States annually, despite of greatly underreported (about 25 fold) and underdiagnosed (about 29 fold) ratio. MRSA has considered as one of the major foodborne pathogens, and it is considered as one of the most significant threats to public health. Recently, MRSA has gained substantial attention due to its increasing resistance against a broad range of antibiotics. The timely detection and quantification of MRSA are of key importance for the prevention of MRSA outbreaks. Considerable efforts have been directed towards the development of rapid and practical biosensor methods for MRSA detection. To keep up this trend, SPR method has been combined with a nanoporous anodic aluminum (NAA) sensor in this study, which is called as NAA sensor -based localized surface plasmon resonance (LSPR) system (Figure 1). This method will overcome the limitations of SPR method due to larger surface-to-volume ratio of NAA sensor. This study aims to optimize the pore size of NAA prior to employment of the NAA-based LSPR system for MRSA detection. For the fabrication of three different sizes of NAA sensor, a two-step anodizing method was employed using various anodization voltage and time, and electrolyte solution. The topology of NAA sensors were observed by employing FE-SEM for measuring the pore diameter, inter-pore distance, and pore length. The reflectance spectrum and fringe pattern of each NAA sensor were measured by using LSPR for the selection of optimum NAA sensor for MRSA detection. The NAA sensor was modified with 11-mercaptoundecanoic acid and immobilized with anti-S. aureus polyclonal antibody. The NAA immunosensors were then exposed to serially diluted MRSA culture starting from 101 CFU/mL to 108 CFU/mL for the measurement of wavelength shift. The attachment of MRSA on the surface of NAA immunosensor was confirmed by SEM observation. Three different pore sizes of sensors were successfully fabricated in the range of 50 to 200 nm by the modification of fabrication conditions. The inter-pore distance and pore length of each sensor with different pore size were 99.7 ± 4.13 nm and 1.02 ± 0.01 µm for 50 nm size sensor, 201.5 ± 2.12 nm and 1.01 ± 0.01 µm for 100 nm size sensor, and 260 ± 1.40 nm and 1.00 ± 0.01 µm for 200 nm size sensor, respectively. The reflectance spectrum and fringe pattern of 200 nm size of sensor showed clearer and greater reflectance spectrum than those of 50 nm and 100 nm pore size of sensor. In addition, the sensitivity of 50, 100 and 200 nm pore size of NAA sensors were determined to be 747 nm/RIU, 1000 nm/RIU, and 1534 nm/RIU, respectively. The wavelength shift of MRSA on the NAA immunosensor was increased as the concentration of MRSA increased. The confirmed numbers of MRSA captured on the NAA immunosensor were increased in a concentration-dependent manner. Detection limit of NAA-based LSPR method was determined to be 102 ± 0.79 CFU/mL. Taking the excellent advantage in cost-effectiveness and simple fabrication of NAA sensor, an optimized NAA sensor-based LSPR method could be applied to detect MRSA in food with successful practicability. Figure 1

Regenerable Plasmonic Biosensor Based on Gold Nanolines Pattern and Common Laboratory Spectrophotometer

Gold nanostructures can undergo plasmonic behavior without need of light couplers like in traditional surface plasmon resonance (SPR) systems. This effect, known as LSPR (localized SPR), can be exploited to develop optical biosensors in simple configuration. In this paper, an LSPR system based on gold lines nanopattern as transducer has been developed by using a common laboratory spectrophotometer as reader and an adapted flow cell. This novel system was applied to anti-immunoglobulin G (IgG) detection, as proof of concept. For this purpose, the transducer surface was covalently biofunctionalized with IgG and incubated with increasing concentrations of anti-IgG. The response was determined by measuring changes in light transmission spectra (Δλ, in nanometers). Contrary to other reported nanopatterns, biosensor features as repeatability, regeneration, and detectability have been deeply studied. Results indicate that the system can act as a robust and regenerable biosensor with a limit of detection of 5.98 ± 1.34 nM.

A reusable localized surface plasmon resonance biosensor for quantitative detection of serum squamous cell carcinoma antigen in cervical cancer patients based on silver nanoparticles array

Squamous cell carcinoma antigen (SCCa), as a tumor biomarker, plays an important role in adjuvant diagnosis, treatment evaluation, and prognosis prediction for cervical cancer patients. Localized surface plasmon resonance (LSPR) technique based on noble metal nanoparticles bypasses the disadvantages of traditional testing strategies, in terms of free-labeling, short assay time, good sensitivity, and selectivity. Herein, we develop a novel and reusable LSPR biosensor for the detection of SCCa. First, a triangle-shaped silver nanoparticle array was fabricated using the nanosphere lithography method. Next, we investigated and verified the feasibility of amino coupling method using 11-mercaptoundecanoic acid (MUA) to form a functionalized chip surface with monoclonal anti-SCCa antibodies on the silver nanoparticles for distinct detection of SCCa. Different concentrations of SCCa were successfully tested in both buffer and human serum by the ultrasensitive and specific LSPR system, with a linear quantitative detection range of 0.1–1,000 pM under optimal conditions. With appropriate regeneration solution, for example 50 mM glycine-HCl (pH 2.0), the LSPR biosensor featured effective fabrication reproducibility, which reduced both production cost and testing time. Our study represents the first application of the LSPR biosensor in cervical cancer, and demonstrates that the rapid, simple, and reusable nanochip can serve as a potential alternative for clinical serological diagnosis of SCCa in cervical cancer patients.

Localized Surface Plasmon Resonance Detection of Biological Toxins Using Cell Surface Oligosaccharides on Glyco Chips

We have detected biological toxins using localized surface plasmon resonance (LSPR) and synthetic glycosyl ceramides (β-lactoside, globosyl trisaccharide (Gb3), or GM1 pentasaccharide) attached to gold (Au) nanoparticles. The particle diameters ranged from 5-100 nm. The detection sensitivity for three toxins (ricin, Shiga toxin, and cholera toxin) was found to depend not only on the attached glycoside but also on the diameter of the Au nanoparticles. For the detection of ricin, the 20-nm β-lactoside-coated Au nanoparticle exhibited the highest LSPR response, whereas 40-nm Gb3- and GM1-coated Au nanoparticles gave the best results for Shiga toxin and cholera toxin, respectively. In addition, a blocking process on the nanoparticle surface greatly improved the detection sensitivity for cholera toxin. The LSPR system enabled us to detect ricin at 30 ng/mL, Shiga toxin at 10 ng/mL, and the cholera toxin at 20 ng/mL.

Effective medium-based analysis of nanowire-mediated localized surface plasmon resonance

We explore a nanowire-based localized surface plasmon resonance (LSPR) sensor system using an effective medium for the nanowire layer. The effective medium is obtained based on the far-field characteristics of the nanowire-based LSPR system. Near-field properties as well as the sensitivity performance of the effective medium-based SPR structure are compared to exact results of the nanowire-based LSPR system. The results indicate that an effective medium can reproduce the far-field and near-field characteristics of nanowires fairly well, while it represents the nanowire-based LSPR on a limited basis in terms of sensitivity characteristics, particularly when the LSPR is significantly enhanced.