Surface Plasmon Resonance Sensor Chip Research Articles

High-sensitivity concentration detection of trace doxycycline in solution by molecular imprinting based on surface plasmon resonance technology

The abuse of doxycycline (DC) will lead to the presence of its residues in animals and water environments, which threatens human health. It is of great significance to detect the micro-content of DC in solution. Based on surface plasmon resonance (SPR) technology, we develop a detection method for trace DC in solution by modifying the SPR sensor chip with a molecular imprinting technique. The results show that the SPR sensor could specifically recognize DC in solution, and the detection limit of this method reaches 10−6µg/mL, which is 100 times lower than that of the ELISA method. The detection signal has good linearity in the concentration range of 10−6−10µg/mL. This method has the advantages of a low detection limit, large linear range, and high specificity for DC detection.

Surface plasmon resonance sensor with photodiode integrated beneath plasmonic layer

Surface plasmon resonance (SPR)-based sensors have demonstrated exceptional sensitivity in detecting changes in the refractive index (RI) occurring near the sensor surface due to variations in concentration within the medium, chemical reactions, analyte binding with its ligand, and similar factors. However, most conventional SPR sensors rely on an external photodiode system and a complex mechanical system to measure changes in both intensity and position of reflected light. This is the main limitation of typical SPR sensors, making them non-portable and challenging to apply in experiments beyond the laboratory. Here, we propose SPR sensor chips integrated with a photodiode that eliminates the disadvantage of conventional SPR sensors. The photodiode is based on an n-type Silicon (nSi)-intrinsic Silicon (iSi) junction, sandwiched between a transparent conductive oxide layer, specifically Indium Tin Oxide (ITO), and a plasmonic material, namely Gold (Au). The working principle of our photodiode-integrated SPR sensors was revealed, and the impact of nSi and iSi film thicknesses on sensor sensitivity was investigated. Our SPR sensors enhance the efficiency of SPR-based sensors across diverse applications and facilitate integration into completed electronic devices.

Efficiency estimation and hardware implementation of solar PV module system assisted by using surface plasmon resonance sensor

This article presents a multi-mode approach for controlling and optimizing the efficiency of solar photovoltaic systems, as well as for analyzing the response output of optical sensing systems. Solar energy has been detected efficiently in this paper using a surface plasmon chip. Initially, the dual axis tracking system was designed and manufactured according to the standard procedure outlined in the literature. The primary factors affecting the efficiency of a photovoltaic panel are proper site heating and panel cleaning. As a result, the proposed system is aimed at increasing the efficiency of photovoltaic panels by addressing the aforementioned issues. Dual axis tracking ensures that the irradiance is always perpendicular to the photovoltaic panel. Additionally, the cooling system mitigates losses caused by panel heating, and the cleaning system increases the PV panel's efficiency. The solar photovoltaic system's output is analyzed using an optical sensing system equipped with a surface plasmon resonance (SPR) sensor. To monitor and control the performance of a proposed prototype solar photovoltaic system using the Resbri Pi3 controller. The proposed system's efficiency is calculated experimentally and presented to confirm the prototype's efficiency. The result is analyzed in the optical domain by the SPR sensor chip.

Rapid and label-free screening of SARS-CoV-2 virus in the infected human nasopharyngeal swab samples using UiO-66-modified SPR chip

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) virus has become a dangerous human pathogen and caused severe illness that can lead to death. Yet, the standard practical diagnostic tools for detecting the SARS-CoV-2 virus require multi-step assay, including extraction and labeling steps. Thus, a simple and accurate detection tool is incredibly desirable to support on-site screening, preventing its spread. In this work, we developed a portable surface plasmon resonance (SPR) sensor chip modified with metal–organic frameworks (MOF) UiO-66 that serves as an immobilization matrix of single-chain variable fragment (scFv) receptors. Large surface area and good adsorption of UiO-66/scFv-modified surface lead to an improvement of binding capacity towards the protein target of the SARS-CoV-2 receptor binding domain (RBD). We further successfully demonstrated the use of this portable SPR to detect the SARS-CoV-2 virus from patients' nasopharyngeal swab samples. Interestingly, the SPR sensors can directly distinguish the positive and negative patients within 15 minutes on 23 samples, simultaneously, without the need for labeling, and the results are in line with the gold standard PCR tests. In addition, the detection limit of the sensors is 10.085 × 105 virus/mL, which follows the standard of practical screening tools. Therefore, these UiO-66 modified SPR chip sensors offer a rapid, label-free, and low-cost detection of the SARS-CoV-2 virus that can be potentially developed for other infectious diseases.

Investigating membrane-binding properties of lipoxygenases using surface plasmon resonance

Lipoxygenases (LOXs) catalyze the oxidation of polyunsaturated fatty acids and synthesize oxylipin products that drive important cellular signaling processes in plants and animals. While there has been indirect evidence presented for the interaction of mammalian LOXs with membranes, a quantitative study of the molecular details of LOX-membrane interactions is lacking. Here, we mimicked biological membranes using surface plasmon resonance (SPR) sensor chips derivatized with 2-D planar lipophilic anchors (2D LP) to capture liposomes of varying phospholipid compositions that self-assemble into lipid bilayers on the SPR chip. The sensor chip surfaces were then used to investigate the membrane-binding properties of model LOX enzymes. SPR binding assays displayed reproducible and stable liposome capture to the sensor chip surface that allowed for the detailed characterization of LOX-membrane interactions. Our studies demonstrate a calcium-dependence for the membrane binding activities of coral 8R-LOX and human 15-LOX-2. Furthermore, our data confirm the importance of key membrane insertion loop residues in each of these LOX enzymes for membrane binding activity. Experiments utilizing model plant and human LOXs reveal differences in membrane-binding specificities. Our study establishes and validates a robust SPR-based platform using 2D LP sensor chips that allows for the detailed study of LOX-membrane interactions under different experimental conditions, including altered membrane compositions. Collectively, this investigation improves our overall understanding of LOX-membrane interaction properties, and our SPR-based approach holds potential for future use in the development of LOX-based therapeutics.

Localized surface plasmon resonance biosensor chip surface modification and signal amplifications toward rapid and sensitive detection of COVID-19 infections

We developed a multi-pronged approach to enhance the detection sensitivity of localized surface plasmon resonance (LSPR) sensor chips to detect SARS-CoV-2. To this end, poly(amidoamine) dendrimers were immobilized onto the surface of LSPR sensor chips to serve as templates to further conjugate aptamers specific for SARS-CoV-2. The immobilized dendrimers were shown to reduce surface nonspecific adsorptions and increase capturing ligand density on the sensor chips, thereby improving detection sensitivity. To characterize the detection sensitivity of the surface-modified sensor chips, SARS-CoV-2 spike protein receptor-binding domain was detected using LSPR sensor chips with different surface modifications. The results showed that the dendrimer-aptamer modified LSPR sensor chip exhibited a limit of detection (LOD) of 21.9 pM, a sensitivity that was 9 times and 152 times more sensitive than the traditional aptamer- or antibody-based LSPR sensor chips, respectively. In addition, detection sensitivity was further improved by combining rolling circle amplification product and gold nanoparticles to further amplify the detection signals by increasing both the target mass and plasmonic coupling effects. Using pseudo SARS-CoV-2 viral particles as detection targets, we demonstrated that this combined signal intensification approach further enhanced the detection sensitivity by 10 folds with a remarkable LOD of 148 vp/mL, making it one of the most sensitive SARS-CoV-2 detection assays reported to date. These results highlight the potential of a novel LSPR-based detection platform for sensitive and rapid detection of COVID-19 infections, as well as other viral infections and point-of-care applications.

Development of a Point-of-Care SPR Sensor for the Diagnosis of Acute Myocardial Infarction.

A novel point-of-care surface plasmon resonance (SPR) sensor was developed for the sensitive and real-time detection of cardiac troponin I (cTnI) using epitope-imprinted molecular receptors. The surface coverage of a nano-molecularly imprinted polymer (nanoMIP)-functionalized SPR sensor chip and the size of nanoMIPs (155.7 nm) were characterized using fluorescence microscopy and dynamic light scattering techniques, respectively. Atomic force microscopy, electrochemical impedance spectroscopy, square wave voltammetry and cyclic voltammetry techniques confirmed the successful implementation of each step of the sensor fabrication. The SPR bio-detection assay was initially established by targeting the cTnI peptide template, and the sensor allowed the detection of the peptide in the concentration range of 100-1000 nM with a correlation coefficient (R2) of 0.96 and limit of detection (LOD) of 76.47 nM. The optimum assay conditions for protein recognition were subsequently determined, and the cTnI biomarker could be detected in a wide concentration range (0.78-50 ng mL-1) with high reproducibility (R2 = 0.91) and sensitivity (LOD: 0.52 ng mL-1). The overall sensor results were subjected to three binding isotherm models, where nanoMIP-cTnI interaction followed the Langmuir binding isotherm with the dissociation constant of 2.99 × 10-11 M, indicating a very strong affinity between the cTnI biomarker and epitope-imprinted synthetic receptor. Furthermore, the selectivity of the sensor was confirmed through studying with a control nanoMIP that was prepared by imprinting a non-specific peptide template. Based on the cross-reactivity tests with non-specific molecules (i.e., glucose, p53 protein, transferrin and bovine serum albumin), the nanoMIP-SPR sensor is highly specific for the target biomarker. The developed biomimetic sensor, relying on the direct assay strategy, holds great potential not only for the early and point-of-care testing of acute myocardial infarction but also for other life-threatening diseases that can be diagnosed by determining the elevated levels of certain biomarkers.

The revelation of glucose adsorption mechanisms on hierarchical metal-organic frameworks using a surface plasmon resonance sensor.

The gold layer on the surface plasmon resonance (SPR) sensor chip cannot detect small molecules, such as glucose without the use of specific receptors. Metal-organic frameworks (MOFs) are useful in biosensing technologies for capturing and co-localizing enzymes and receptors with the target biomolecule. In many previous studies, the properties of the MOFs were often ignored, with these studies focusing on the selection of appropriate receptors. To take advantage of the unique properties of MOFs in biosensors, one must also consider the technique and transducer used because these aspects will strongly influence the detection mechanism. In this work, we have investigated for the first time, the applications of hierarchical metal-BDC (M-BDC) MOFs for glucose detection using the SPR technique without the use of specific receptors. The underlying interactions and adsorption mechanisms were analyzed using adsorption isotherm and kinetic models. The sensing measurements show that the SPR chips functionalized with M-BDC MOFs exhibit higher sensitivity and lower limit of detection (LOD). Specifically, the sensitivity follows the order of Zr-BDC > Cu-BDC > Mn-BDC > Ni-BDC > bare Au SPR chips with the LOD in the order of Zr-BDC < Mn-BDC < Ni-BDC < Cu-BDC < bare Au SPR chips. The selectivity test results reveal that Zr-BDC exhibits a decent selectivity to glucose in the presence of other interfering compounds, such as ascorbic acid, uric acid, maltose, and urea. These results demonstrate the promising potential of MOFs for SPR biosensing.

Highly Specific Peptide-Mediated Cuvette-Form Localized Surface Plasmon Resonance (LSPR)-Based Fipronil Detection in Egg

Herein, we have developed peptide-coated gold nanoparticles (AuNPs) based on localized surface plasmon resonance (LSPR) sensor chips that can detect fipronil with high sensitivity and selectivity. The phage display technique has been exploited for the screening of highly specific fipronil-binding peptides for the selective detection of the molecule. LSPR sensor chips are fabricated initially by attaching uniformly synthesized AuNPs on the glass substrate, followed by the addition of screened peptides. The parameters, such as the peptide concentration of 20 µg mL-1 and the reaction time of 30 min, are further optimized to maximize the efficacy of the fabricated LSPR sensor chips. The sensing analysis is performed systematically under standard fipronil solutions and spike samples from eggs. The developed sensor has shown excellent sensitivity towards both standard solutions and spike samples with limit of detection (LOD) values of 0.01 ppb, respectively. Significantly, the developed LSPR sensor chips offer distinct features, such as a facile fabrication approach, on-site sensing, rapid analysis, cost-effectiveness, and the possibility of mass production, in which the chips can be effectively used as a promising and potential on-site detection tool for the estimation of fipronil.

An LSPR Sensor Integrated with VCSEL and Microfluidic Chip.

The work introduces a localized surface plasmon resonance (LSPR) sensor chip integrated with vertical-cavity surface-emitting lasers (VCSELs). Using VCSEL as the light source, the hexagonal gold nanoparticle array was integrated with anodic aluminum oxide (AAO) as the mask on the light-emitting end face. The sensitivity sensing test of the refractive index solution was realized, combined with microfluidic technology. At the same time, the finite-difference time- domain (FDTD) algorithm was applied to model and simulate the gold nanostructures. The experimental results showed that the output power of the sensor was related to the refractive index of the sucrose solution. The maximum sensitivity of the sensor was 1.65 × 106 nW/RIU, which gives it great application potential in the field of biomolecular detection.

Site specific biotinylated antibody functionalized Ag@AuNIs LSPR biosensor for the ultrasensitive detection of exosomal MCT4, a glioblastoma progression biomarker

Glioblastoma (GBM) is an incurable brain tumor in which hypoxic GBM cells (GMs) increase the production and release of exosomes, which are 30–200 nm vesicles crossing the blood–brain-barrier, enabling exosomal biomarkers to be promising targets for the tracking of GBM malignancy. Here, a localized surface plasmon resonance (LSPR) sensor chip was developed to detect an infinitesimal amount of exosomal biomarkers. Self-assembly silver nanoparticles decorated on gold nano-islands (Ag@AuNIs) sensor chip was used to provide site-specific bio-conjunction of biotinylated antibodies for detection of exosomal surface biomarkers. The biotinylated antibody functionalized (BAF) Ag@AuNIs LSPR biosensor sensitively detected cluster of differentiation 63, an exosome marker, and monocarboxylate transporter 4 (MCT4), a GBM progression biomarker, in malignant GMs-derived exosomes in the dynamic range of 3.8 × 10−4 to 50 μg/ml with limit of detection (LOD) of 0.38 ng/ml and 1.4 × 10−3 to 500 μg/ml with LOD of 1.4 ng/ml, respectively. Furthermore, it detected the enhanced level of MCT4 in malignant hypoxic GMs-derived exosomes as well as increased MCT4 in the blood serum-derived exosomes of GBM mice in the dynamic range of 4 × 10−4 to 50 μg/ml with LOD of 0.4 ng/ml. Finally, it could quantify MCT4 in the isolated GMs-derived exosomes from the blood of GBM mice by epidermal growth factor receptor variant III-based immunocapture, suggesting its utility for minimally-invasive monitoring of GBM progression as liquid biopsy. With excellent attributes of high sensitivity and selectivity in label-free sensing for exosomal biomarkers, the BAF Ag@AuNIs LSPR biosensor has great potential for early detection of GBM formation and progression.

Integration of a multichannel surface plasmon resonance sensor chip and refractive index matching film array for protein detection in human urine

Most prism-based surface plasmon resonance (SPR) experiments use matching fluid with a similar refractive index to mount the chip on the optical prism. The fluidity of the matching fluid easily affects the transmission of the optical signal. In this paper, an integrated SPR sensor chip comprises a three-layer structure of flow layer, metal layer and refractive index matching layer is demonstrated to address the problems related to consistency and uniformity. The Young's modulus, array spacing, shape and other parameters of the matching film were calculated and optimized. The chip can self-adhere to the optical prism, and effectively avoids the generation of air bubbles. The refractive index detection sensitivity of the integrated SPR sensor chip was 3.4359 × 10−6 RIU (refractive index unit), and the chip stabilization time has been effectively shortened. The integrated SPR sensor chip was also used to detect kappa light chain protein and human serum albumin (HSA) in urine samples. The detection limit of kappa light chain protein was 0.06 μg/mL compared with 18.5 μg/mL by conventional immunoturbidimetry. The integrated SPR sensor chip based on refractive index matching film array has great potential in biomedical detection and other fields, including point-of-care testing (POCT).

Molecularly Imprinted Polymers Based Surface Plasmon Resonance Sensor for Sulfamethoxazole Detection

Sulfamethoxazole (SMX) is a sulfonamide antibiotic primarily used to treat urinary tract infections and used in veterinary and industrialized husbandry to treat diseases and food additives. Like other antibiotics, SMX is considered as a pollutant in water and food that threaten local life. This study developed a surface plasmon resonance (SPR) sensor chip that is fast, highly selective, and reusable, and requires no pretreatment for detecting SMX. As a receptor, SMX imprinted methacrylic acid-2-hydroxyethyl methacrylate-ethylene glycol dimethacrylate polymer [poly(MAA-HEMA-EGDMA)] was used. The surface of the gold SPR chips was coated with a drop-casting method. The nanofilm coated chips were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), ellipsometer, contact angle measurement, and Fourier-transform infrared spectrometry (FTIR). Imprinting factor (IF) was calculated as: ΔR[MIP(molecularly imprinted polymers)]/ΔR[NIP(non-imprinted)]=12/3.5=3.4. Limit of detection (LOD) and limit of quantification (LOQ) values were calculated with 3 s/m and 10 s/m methods, and the results were found to be 0.001 1 µg/L for LOD 0.003 4 µg/L for LOQ. Adsorption studies on both standard SMX solution and commercial milk samples were applied. Also, we investigated the developed chip’s reusability, storability, and selectivity with amoxicillin and cefalexin.

Exploiting a strong coupling regime of organic pentamer surface plasmon resonance based on the Otto configuration for creatinine detection.

The sandwiched material-analyte layer in the surface plasmon resonance (SPR)-Otto configuration emulates an optical cavity and, coupled with large optical nonlinearity material, the rate of light escaping from the system is reduced, allowing the formation of a strong coupling regime. Here, we report an organic pentamer SPR sensor using the Otto configuration to induce a strong coupling regime for creatinine detection. Prior to that, the SPR sensor chip was modified with an organic pentamer, 1,4-bis[2-(5-thiophene-2-yl)-1-benzothiopene]-2,5-dioctyloxybenzene (BOBzBT2). To improve the experimental calibration curve, a normalisation approach based on the strong coupling-induced second dip was also developed. By using this procedure, the performance of the sensor improved to 0.11 mg/dL and 0.36 mg/dL for the detection and quantification limits, respectively.

Testosterone Imprinted poly(HEMA‐MAA) Nanoparticles Based Surface Plasmon Resonance Sensor for Detection of Testosterone

AbstractThe selective, sensitive, and real‐time detection of testosterone was performed from both testosterone aqueous solution and artificial urine samples by using the advantages of surface plasmon resonance sensor (SPR) with molecular imprinting technique. The testosterone imprinted (MIP) and non‐imprinted (NIP) nanoparticle based poly(2‐hydroxyethyl methacrylate‐methacrylic acid (poly(HEMA‐MAA)) SPR sensors were prepared for detection of testosterone. After characterization of MIP and NIP nanoparticles, nanoparticles were attached on the SPR chip surfaces. The characterization of SPR sensor surfaces was carried out with characterization methods such as atomic force microscopy, ellipsometer and contact angle measurements. The real‐time measurements for detection of testosterone were performed with testosterone imprinted SPR sensor in the linear range of 0.5‐20 ng/mL concentration in testosterone aqueous solution. The imprinting factor and the limit of detection was found 4.16 and 0.049 ng/mL, respectively. The validation studies were performed with both SPR sensor and enzyme‐linked immunosorbent assay using testosterone samples prepared in artificial urine samples for the detection of testosterone.

AC-Electroosmosis-Assisted Surface Plasmon Resonance Sensing for Enhancing Protein Signals with a Simple Kretschmann Configuration.

A surface plasmon resonance (SPR) sensor chip fabricated with a comb-shaped microelectrode array to supply alternating current (AC) voltage is reported. The chip induces circulating flow near the surface (i.e., AC electroosmosis). The circulating flow provides a mixing effect, which enhances the binding of the analyte molecules. We evaluated the SPR characteristics of the chip and demonstrated an improvement in protein binding to the chip surface. SPR sensor chips with comb-shaped microelectrodes were fabricated using standard UV lithography. Sensing experiments were conducted using a standard Kretschmann-type SPR measurement system. To demonstrate the mixing effect of AC electroosmosis, we evaluated the binding of immunoglobulin G molecules onto the sensor surface where anti-immunoglobulin G antibodies were covalently immobilized. The result indicates that the amount of binding increases by a factor of 1.7 above that achieved by using a conventional chip, suggesting enhancement of the protein signal.

Facile layered structure of sensing chip of a prism–based surface plasmon resonance device

Surface plasmon resonance (SPR) is a popular optical phenomenon for sensing application owing to its capability for label-free measurement which offers very high resolution and sensitivity. The traditional prism based Kretschmann configuration employs a sensing chip consists of a glass substrate deposited with 50 nm thick gold/silver layer. The parameters of the figure-of-merit (FOM) of an SPR sensor are a quality factor, signal-to-noise ratio, and the strength of the plasmonic field over the gold surface. In this article, we present a simulation work on a facile SPR sensor chip that yields a high FOM as compared to the traditional SPR sensor chip. We introduced a metallic intermediate layer (IML) in the traditional SPR chip and optimized the performance with respect to the material and thickness of IML. We optimized the thickness of the glass substrate such that the plasmonic field generated in the IML can couple with the outer gold film (OGF). Such coupling enhances the overall plasmonic field over the OGF by 112%.

Surface Plasmon Resonance Analysis of PfEMP1 Interaction with Receptors.

A detailed understanding of the interaction between the highly variant Plasmodium falciparum erythrocyte membrane proteins 1 (PfEMP1) and their human binding partners is essential to explain their roles in disease development in malaria, as well as to understand how antibodies can inhibit these interactions and how the parasite manages to evade such an immune response. This chapter focuses on using surface plasmon resonance (SPR) as a reproducible, high-throughput method to quantitatively characterize these interactions. We describe how to utilize protein A or A/G and streptavidin for protein immobilization on SPR sensor chips and provide instructions on how to biotinylate proteins for this purpose and how to use SPR for binding competition assays. Since these experiments rely on recombinant proteins, we also present a method to verify their structural integrity using circular dichroism spectroscopy.

Surface plasmon resonance aptasensor for Brucella detection in milk

A Surface Plasmon Resonance (SPR) aptasensor was developed for the detection of Brucella melitensis (B. melitensis) in milk samples. Brucellosis is a bacterial zoonotic disease with global distribution caused mostly by contaminated milk or their products. Aptamers recognizing B. melitensis were selected following a whole bacteria-SELEX procedure. Two aptamers were chosen for high affinity and high specificity. The high affinity aptamer (B70 aptamer) was immobilized on the surface of magnetic silica core-shell nanoparticles for initial purification of the target bacteria cells from milk matrix. Another aptamer, highly specific for B. melitensis cells (B46 aptamer), was used to prepare SPR sensor chips for sensitive determination of Brucella in eluted samples from magnetic purification since direct injection of milk samples to SPR sensor chips is known for a high background unspecific signal. Thus, we integrated a quick and efficient magnetic isolation step for subsequent instant detection of B. melitensis contamination in one ml of milk sample by SPR with a LOD value as low as 27 ± 11 cells.

Sensitive and selective detection of amitrole based on molecularly imprinted nanosensor.

SPR sensor used for amitrole detection was prepared without using any modification. Molecularly imprinted SPR sensor enabled high selectivity for amitrole pesticide. Amino acid-based functional monomer MATrp was integrated as a recognition element. Tailor-made SPR sensor enables real-time monitoring of amitrole pesticide. Synthetic recognition sites provided by MATrp were prepared without labeling.