Selective Surface Plasmon Resonance Research Articles

Sensitive and selective Cu2+ detection via surface plasmon resonance using ionophore decorated nanocrystalline cellulose-graphene oxide thin film

In this work, highly sensitive and selective surface plasmon resonance (SPR) sensor has been developed using nanocrystalline cellulose-graphene oxide-ionophore (NCC-GO-ionophore) for copper ion (Cu2+) detection. By incorporating SPR with nanocrystalline cellulose-graphene oxide-ionophore (NCC-GO-ionophore) thin film, Cu2+ was able to be detected as low as 0.001 ppm until 0.1 ppm. Moreover, the results show that the NCC-GO-ionophore thin film has good sensitivity towards Cu2+ with sensitivity value of 59.9150° ppm−1 from 0.001 to 0.01 ppm and 2.2261° ppm−1 from 0.01 to 0.1 ppm. Besides that, the developed sensor also shows high affinity towards Cu2+ compared to other metal ions. Using the Langmuir isotherm model, the binding affinity constant, K was calculated i.e., 6.881 × 103 M−1. Furthermore, the ability of the sensor to detect Cu2+ in spiked river water sample was also investigated where Cu2+ as low as 0.5 until 100 ppm can be determined. This result shows that the sensor has high sensitivity and selectivity towards Cu2+ detection.

Ti3C2-MXene-assisted signal amplification for sensitive and selective surface plasmon resonance biosensing of biomarker

Surface plasmon resonance (SPR) technology has become one of the powerful tools for real-time bioassay of various targets without needing labels. However, SPR biosensing faces great challenge with the extension of application fields due to the limited sensitivity. Herein, we report an ultrasensitive SPR biosensing strategy for detecting carcinoembryonic antigen (CEA) with the introduction of amino-functionalized Ti3C2-MXene (N-Ti3C2-MXene) nanosheets. The ultrathin Ti3C2-MXene nanosheets were prepared by hydrochloric acid (HF) etching and further modified by (3-aminopropyl) triethoxysilane (APTES) to obtain amino terminals for conjugating polyclonal anti-CEA antibody (Ab2) via covalent bonding. Staphylococcal protein A (SPA) decorated Au film was utilized as sensing platform to orientedly immobilize monoclonal anti-CEA antibody (Ab1) via its Fc region. The N-Ti3C2-MXene-Ab2 nanoconjugates were introduced to the sensing system after capture of CEA, forming sandwiched immunocomplexes on the SPR chip. A signal amplification strategy of Ti3C2-MXene-induced spontaneous gold reductive deposition on Ti3C2-MXene nanosheets was employed to further enhance sensitivity. The proposed biosensor exhibits a wide linear range for CEA determination of 10−11 to 10−6 g mL−1 with a detection limit of 1.7 pg mL−1 (S/N=3). Moreover, good reproducibility and high specificity were demonstrated by serum samples analysis, which indicates the present method holds potential in evaluating CEA in human serum for early diagnosis and monitoring of cancer.

Highly sensitive and selective surface plasmon resonance biosensor for the detection of SARS-CoV-2 spike S1 protein

The reality that the coronavirus disease 2019 (COVID-19) is still raging around the world and making a comeback with a strong presence has highlighted the need for rapid and sensitive quantitative detection methods of viral RNA, antibody and antigen for widespread tracking and screening applications. Surface plasmon resonance (SPR) detection technology has achieved rapid development and become a standard measurement method in the fields of biosensing, biomedicine, biochemistry and biopharmaceuticals due to its advantages of high sensitivity, fast response and no need for labelling. Here, we report a sandwiched structure-based SPR biosensor for detecting a specific viral antigen, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike S1 protein. The sensor combines a Ti3C2-MXene nanosheet modified sensing platform and polydopamine (PDA)-Ag nanoparticle (AgNP)/anti-SARS-CoV-2 spike S1 protein nanoconjugate signal enhancers, exhibiting a wide linear range of 0.0001 to 1000 ng mL-1 with a low detection limit of 12 fg mL-1 (S/N = 3). In the analysis of artificial saliva and human serum samples, the proposed SPR biosensor exhibits good reproducibility and high specificity, which indicates its potential for application in complex bodily fluids. The exploitation of the MXene-based SPR biochip for recognizing the SARS-CoV-2 antigen provides an accessible and rapid way for COVID-19 diagnosis, and promotes the application of 2D nanomaterial-based sensing chips in clinical diagnosis and disease screening. Significantly, the proposed method possesses general applicability that can be reprogrammed to detect any protein antigen if a corresponding specific nanobody is available.

Molecularly imprinted nanofilms for endotoxin detection using an surface plasmon resonance sensor

In this study, a simple, fast, sensitive and selective surface plasmon resonance (SPR) sensor was prepared using molecular imprinting method for endotoxin detection. Endotoxin imprinted and non-imprinted poly(hydroxyethyl methacrylate-N-methacryloyl-(L)-histidine methyl ester) based nanofilms were synthesized on the SPR chip surfaces using ultraviolet polymerization. Endotoxin imprinted and non-imprinted SPR sensors were characterized by using contact angle, atomic force microscopy and ellipsometry. After characterization studies, kinetic studies was carried out in the concentration range of 0.5–100 ng/mL. The limit of detection and quantification were obtained as 0.023 and 0.078 ng/mL, respectively. The response time for the equilibration, adsorption and regeneration was approximately 14 min. The selectivity studies with cholesterol and hemoglobin of endotoxin imprinted SPR sensor were examined. Validation studies were carried out via limulus amebocyte lysate (LAL) in order to demonstrate the applicability of the SPR sensor.

Molecularly imprinted polymer film based plasmonic sensors for detection of ochratoxin A in dried fig

Ochratoxin A (OTA), a group of highly toxic fungal secondary metabolites, is one of the most common mycotoxins that contaminate a wide range of agricultural products. Herein, we designed a label-free and selective surface plasmon resonance (SPR) based sensor for detection of OTA contamination in dried fig. The molecularly imprinted polymer film (MIP) was fabricated onto the SPR sensor chip by using light-initiated polymerization of N-methacryloyl-(L)-phenylalanine and 2-Hydroxyethyl methacrylate in the presence of OTA as a template. SPR chips were characterized by using contact angle, atomic force microscopy, and ellipsometry. OTA imprinted sensor was displayed a broad linear range, between 0.1 ng/mL and 20 ng/mL. The limit of detection was calculated as 0.028 ng/mL. The selectivity studies of the OTA imprinted SPR sensor was performed in the presence of aflatoxin M1, aflatoxin B1, and citrinin. The imprinting factor was found to be 2.85. The adsorption behavior of the OTA imprinted sensor was found as suitable for the Langmuir model. Results displayed that the OTA imprinted SPR sensor was successfully applied to determine OTA in dried fig samples.

Surface Plasmon Resonance Based on Molecularly Imprinted Polymeric Film for l-Phenylalanine Detection.

In this study, we designed a simple, rapid, sensitive and selective surface plasmon resonance (SPR) sensor for detection of L-phenylalaine by utilizing molecular imprinting technology. l-phenylalanine imprinted and non-imprinted poly(2-hydroxyethyl methacrylate-methacryloyl-l-phenylalanine) polymeric films were synthesized onto SPR chip surfaces using ultraviolet polymerization. l-phenyalanine imprinted and non-imprinted SPR sensors were characterized by using contact angle, atomic force microscopy and ellipsometry. After characterization studies, kinetic studies were carried out in the concentration range of 5.0–400.0 μM. The limit of detection and quantification were obtained as 0.0085 and 0.0285 μM, respectively. The response time for the test including equilibration, adsorption and desorption was approximately 9 min. The selectivity studies of the l-phenylalanine imprinted SPR sensor was performed in the presence of d-phenylalanine and l-tryptophan. Validation studies were carried out via enzyme-linked immunosorbent analysis technique in order to demonstrate the applicability and superiority of the l-phenylalanine imprinted SPR sensor.

Quantitative and Selective Surface Plasmon Resonance Response Based on a Reduced Graphene Oxide-Polyamidoamine Nanocomposite for Detection of Dengue Virus E-Proteins.

Dengue viral infection is one of the most common deadliest diseases and has become a recurrent issue for public health in tropical countries. Although the spectrum of clinical diagnosis and treatment have recently been established, the efficient and rapid detection of dengue virus (DENV) during viremia and the early febrile phase is still a great challenge. In this study, a dithiobis (succinimidyl undecanoate, DSU)/amine-functionalized reduced graphene oxide-–polyamidoamine dendrimer (DSU/amine-functionalized rGO–PAMAM) thin film-based surface plasmon resonance (SPR) sensor was developed for the detection of DENV 2 E-proteins. Different concentrations of DENV 2 E-proteins were successfully tested by the developed SPR sensor-based system. The performance of the developed sensor showed increased shift in the SPR angle, narrow full-width–half-maximum of the SPR curve, high detection accuracy, excellent figure of merit and signal-to-noise ratio, good sensitivity values in the range of 0.08–0.5 pM (S = 0.2576°/pM, R2 = 0.92), and a high equilibrium association constant (KA) of 7.6452 TM−1. The developed sensor also showed a sensitive and selective response towards DENV 2 E-proteins compared to DENV 1 E-proteins and ZIKV (Zika virus) E-proteins. Overall, it was concluded that the Au/DSU/amine-functionalized rGO–PAMAM thin film-based SPR sensor has potential to serve as a rapid clinical diagnostic tool for DENV infection.

Sensitive and selective surface plasmon resonance sensor employing a gold-supported graphene composite film/D-shaped fiber for dopamine detection

An Au film/graphene D-shaped plastic optical fiber (D-POF) functionalized with dopamine-binding aptamer (DBA) was proposed to achieve a sensitive and specific detection of the small molecule dopamine. The surface plasmon resonance sensor combines the virtues of a D-shaped fiber, the transfer of graphene via gold film, and the amplification of the refractive index with the conformational transformation of DBA. The sensitivity of the Au film/graphene D-POF sensor (1539 nm/RIU) is higher than that without graphene in ethanol solution. The dopamine concentrations of 10−10 M to 10−6 M were measured. And the decoration of DBA onto graphene for dopamine detection with a good linearity was verified in experiments. The proposed sensor possesses high sensitivity and specificity, which will provide good application prospects for the development of biosensing in disease treatment.

Determination of Lysozyme by Thiol-Terminated Aptamer-Based Surface Plasmon Resonance

ABSTRACTA sensitive and selective surface plasmon resonance (SPR) aptasensor has been developed for the real-time determination of lysozyme. The thiol-terminated lysozyme aptamer was covalently attached to the surface of sensor through Au–S bonding. In the presence of lysozyme, the aptamer captured lysozyme on the surface and enhanced the SPR signal that was proportional to the concentration of lysozyme. Under the optimized conditions, the SPR signal was linear with lysozyme concentration from 1 to 100 µmol/L. The detection limit for lysozyme was 0.5 µmol/L. The aptasensor also provided high specificity for lysozyme and was unaffected by other proteins. This aptasensor provides rapid, simple, and sensitive determination of lysozyme detection and a promising strategy for other proteins.

SPRI biosensors for quantitative determination of matrix metalloproteinase-2

The aim of this study was to develop a new, label-free, highly selective Surface Plasmon Resonance Imaging biosensor for the quantitative determination of matrix metalloproteinase-2.

Biomimetic self-templating optical structures fabricated by genetically engineered M13 bacteriophage

Here, we describe a highly sensitive and selective surface plasmon resonance sensor system by utilizing self-assembly of genetically engineered M13 bacteriophage. About 2700 copies of genetically expressed peptide copies give superior selectivity and sensitivity to M13 phage-based SPR sensor. Furthermore, the sensitivity of the M13 phage-based SPR sensor was enhanced due to the aligning of receptor matrix in specific direction. Incorporation of specific binding peptide (His Pro Gln: HPQ) gives M13 bacteriophage high selectivity for the streptavidin. Our M13 phage-based SPR sensor takes advantage of simplicity of self-assembly compared with relatively complex photolithography techniques or chemical conjugations. Additionally, designed structure which is composed of functionalized M13 bacteriophage can simultaneously improve the sensitivity and selectivity of SPR sensor evidently. By taking advantages of the genetic engineering and self-assembly, we propose the simple method for fabricating novel M13 phage-based SPR sensor system which has a high sensitivity and high selectivity.

Detection of vascular endothelial growth factor based on rolling circle amplification as a means of signal enhancement in surface plasmon resonance

Vascular endothelial growth factor (VEGF) is a major regulator of angiogenesis. It has been identified as an ideal biomarker for staging of many kinds of cancers, so more specific and intense signal is desirable for VEGF biosensors so that the sensors may have more valuable clinical application. Herein, we report a highly sensitive and selective surface plasmon resonance (SPR) sensor for VEGF detection by using two DNA aptamers which target different VEGF domains used as the capture and detection probe, respectively. Moreover, by making use of carboxyl-coated polystyrene microspheres, 3′–NH2 immobilized aptamer and 3′–NH2 modified primer DNA are loaded through amidation onto the sensing layer for further rolling circle amplification (RCA) process to amplify the SPR signal. With the well-designed sensing platform, VEGF can be determined in a linear range from 100pgmL−1 to 1μgmL−1 with a detection limit of 100pgmL−1. Due to its high specificity and desirable sensitivity, this RCA assisted SPR method may be a useful tool for the assay of VEGF in the future. What is more, by replacing the sensing element, i.e., the aptamer of VEGF used in this work, more biosensors for sensitive detection of other biomarkers proteins can be fabricated based on the strategy proposed in this study.

Molecularly imprinted polymer based surface plasmon resonance sensors for detection of Sudan dyes

A highly sensitive and selective surface plasmon resonance sensor for detection of Sudan dyes based on a molecularly imprinted nanofilm.

Development of indirect competitive immunoassay for highly sensitive determination of ractopamine in pork liver samples based on surface plasmon resonance sensor

In this work, we demonstrate the development of a highly sensitive and selective surface plasmon resonance (SPR) immunosensor for label-free detection of ractopamine (RCT) as low as 0.12 ppb (ng mL −1) direct from pork liver samples. RCT is a kind of the β-adrenergic agonist with N-alkylphenyl substituent, and the development of high performance sensing methods for RCT is a critical issue because of its vital role in human metabolism. To construct the immunosensor system, the biosensor surface was formed by immobilization of ractopamine–ovalbumin (RCT–OVA) conjugate onto an Au-thiolate self-assembled SPR sensor chip by covalent amide binding, and the detection of RCT was performed based on indirect competitive inhibition principle. Detailed works were carried out focusing on optimizing the conditions that affect immunosensitivity, including immobilization buffer, immunobinding buffer, RCT–OVA concentration, antibody concentration, activation time, regeneration buffer, etc. A preferable way to determine the optimal antibody concentration was performed comparing with that used in most other reported researches. Under the optimal conditions, the biosensor exhibits a linear detection range of 0.28–4.29 ng mL −1, LOD of 0.12 ng mL −1 and IC 50 of 1.17 ng mL −1. It improved that the developed SPR immunosensor is more sensitive for detection of RCT against other reported ones.

A simple and versatile self-assembled monolayer based surface plasmon resonance immunosensor for highly sensitive detection of 2,4-D from natural water resources

Abstract In this work, we demonstrate the development of a highly sensitive and selective surface plasmon resonance (SPR) immunosensor for label-free detection of 2,4-dichlorophenoxyacetic acid (2,4-D) as low as 10 ppt (pg ml −1 ) direct from aquatic environmental samples. 2,4- D is a systemic herbicide and a potential endocrine disrupting chemical. Primary screening methods for detection of 2,4- D should be easy-to-use, inexpensive and usable for routine analysis of a large number of food and potable water samples. Here, we fabricate the sensing surface of the SPR immunosensor simply by covalent amide binding of a bovine serum albumin conjugate of 2,4- D (hereafter, 2,4- D –BSA) on the Au-thiolate self-assembly of simple and commercially available 3-mercaptopropionic acid (MPA). An indirect competitive immunoassay method that assures the detection of low-molecular-weight analytes was accomplished for the detection of 2,4- D , in which the specific affinity binding of monoclonal anti-2,4- D antibody (hereafter, 2,4- D –mAb) on the 2,4- D –BSA bound SAM surface was examined at various concentrations of 2,4- D . The extent of the 2,4- D –mAb binding on the sensor surface is inhibited by the presence of 2,4- D , and the SPR angle response is inversely proportional to the concentration of the analyte 2,4- D . With the developed SPR sensor, a low-detection-limit of 0.1 ppb (ng ml −1 ) 2,4- D is established with a response time of only 4 min. By taking advantage of the controlled immobilization of 2,4- D –BSA on the SAM surface, the immunoaffinity interactions of 2,4- D –mAb with the 2,4- D –BSA sensor surface and 2,4- D in solution could be significantly modulated. As a result, the sensitivity of the SPR immunosensor is enhanced by about 10-fold to 10 ppt without using any high-molecular-weight labels. After an immunoaffinity binding cycle, the active sensor surface was retrieved by the removal of 2,4- D –mAb from the sensor surface using an acidic buffer (glycine·HCl, pH 2.0). The SPR immunosensor showed excellent selectivity for 2,4- D detection with a negligible cross-sensitivity against various closely related environmental pollutants and is found capable of detecting ppt levels of 2,4- D from spiked river water samples.

Highly sensitive and selective surface plasmon resonance sensor for detection of sub-ppb levels of benzo[a]pyrene by indirect competitive immunoreaction method

A surface plasmon resonance (SPR)-immunosensor for detection of benzo[a]pyrene (BaP) is developed by using a model BaP-hapten compound, BaP-bovine serum albumin conjugate (BaP–BSA), and an anti-BaP–BSA monoclonal antibody. BaP–BSA conjugate is immobilized on a gold thin-film sensor chip by means of simple physical adsorption. The number of BaP-hapten units in BaP–BSA conjugate is estimated to be 28 from the difference in molecular weight (MW) between BaP–BSA conjugate and BSA based on the results of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) measurement. Anti-BaP–BSA antibody on contact with the BaP–BSA conjugate immobilized sensor chip causes an increase in the incident angle of the sensor chip. Binding of anti-BaP–BSA antibody with surface-immobilized BaP–BSA conjugate is inhibited by the presence of BaP in analyte solution, because of the inhibition effect of BaP. The SPR immunosensor for BaP functioning with the indirect competitive immunoreaction of anti-BaP–BSA antibody between the analyte (BaP) in testing solution and the BaP–BSA conjugate immobilized on the sensor chip provides a rapid determination (response time: ca. 15 min) of BaP in the concentration range of 0.01–1000 ppb. The antibody anchored to the sensor chip by antigen–antibody binding is removed on treatment with a pepsin solution (pH 2.0) for few minutes. The SPR sensor chip is found to be reusable for more than 20 times with a little decrease (<7%) in the sensor response. Detection of BaP by direct competitive immunoreactions is also carried out by enzyme-linked immunosorbent assay (ELISA). The concentration of BaP could be determined as low as 0.01 ppb and 2 ppb using the SPR sensor and the ELISA method, respectively. The SPR sensor is found to detect BaP selectively in the presence of 2-hydroxybiphenyl (HBP); the incident angle shift of the SPR sensor for BaP is found to be same irrespective to the presence or the absence of a same concentration (as much as 30 ppb) of HBP together.

Highly selective surface plasmon resonance sensor for NO2

Changes in the surface plasmon resonance (SPR) of a 45 nm thick gold film, thermally evaporated onto one face of a BK7 glass prism, have been used to detect nitrogen dioxide (NO2). The intensity of the reflected light decreases linearly with the concentration of gas, the change being 0.1% per 1 ppm of NO2 with a response time of ~30 s for adsorption and 30–40 s for desorption. The process is highly selective and other gases, e.g. NH3, H2, CO, CO2, SO2, HCl, Cl2 and H2S, have little or no noticeable effect on the SPR at concentrations of 100 ppm. It is also reversible by flushing with air and the NO2 sensor showed only a 10% deterioration in the SPR response after 1500 adsorption/desorption cycles.