Surface Plasmon Resonance Signal Amplification Research Articles

Cucurbit[7]urils induced bimetallic nanoparticles network for ultra-sensitive detection of Caspase-3 based on surface plasmon resonance

A novel signal amplification method for surface plasmon resonance (SPR) was developed to detect Caspase-3 based on cucurbit[7]urils (CB[7]) and bimetallic nanonetwork. Three-dimensional (3D) bimetallic nanonetwork was formed through CB[7]-integrated self-assembly of gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) (AuNPs-CB[7]-AgNPs) by one-pot synthesis method. Caspase-3 was utilized as a model protein and peptide EEAAADEVDFKKAAAC was used as the substrate. In the presence of Caspase-3, peptide was hydrolyzed and exposed phenylalanine at the N-terminus, which could bind to CB[7] through host-guest interaction. The multivalent receptors CB[7] on bimetallic nanonetwork provide a simple strategy to increase the binding affinities between 3D bimetallic nanonetwork and peptide. Thus, AuNPs-CB[7]-AgNPs could attach to the gold chip with ease. Remarkably, due to the strong optical properties and high refractive index of 3D bimetallic nanonetwork, it has a higher SPR signal enhancement than that of only AuNPs or AgNPs. Therefore, a highly sensitive Caspase-3 sensing strategy could be achieved with a low detection limit of 5.39 pg mL−1, providing a new and facile SPR signal amplification method for detection of cell apoptosis.

Amplification-free Detection of Cytomegalovirus miRNA Using a Modification-free Surface Plasmon Resonance Biosensor.

Cytomegalovirus (CMV) is the most frequent cause of congenital infection worldwide; congenital CMV may lead to significant mortality, morbidity, or long-term sequelae, such as sensorineural hearing loss. The current study presents a newly designed surface plasmon resonance (SPR) biosensor for CMV-specific microRNAs that does not involve extra care for receptor immobilization or treatment to prevent fouling on bare gold surfaces. The modification-free approach, which utilizes a poly-adenine [poly(A)]-Au interaction, exhibited a high affinity that was comparable to that of the gold-sulfur (Au-S) interaction. In addition, magnetic nanoparticles (MNPs) were used to separate the analyte from complex sample matrixes that significantly reduced nonspecific adsorption. Moreover, the MNPs also played an important role in SPR signal amplification due to the binding-induced change in the refractive index. Our SPR biosensing platform was used successfully for the multi-detection of the microRNAs, UL22A-5p, and UL112-3p, which were associated with CMV. Our SPR biosensor offered the detection limits of 108 fM and 24 fM for UL22A-5p and UL112-3p, respectively, with an R2 of 0.9661 and 0.9985, respectively. The precision of this biosensor has an acceptable CV (coefficient of variation) value of <10%. In addition, our sensor is capable of discriminating between serum samples collected from healthy and CMV-infected newborns. Taken together, we believe that our newly developed SPR biosensing platform is a promising alternative for the diagnosis of CMV-specific microRNA in clinical settings, and its application for the detection of other miRNAs may be extended further.

Multi-layer optical fiber surface plasmon resonance biosensor based on a sandwich structure of polydopamine-MoSe2@Au nanoparticles-polydopamine.

An all-optical fiber multi-layer surface plasmon resonance (SPR) biosensor based on a sandwich structure of polydopamine-MoSe2@Au nanoparticles-polydopamine (PDA-MoSe2@AuNPs-PDA) was designed for the detection of specific immunoreactions. By optimizing the multi-layer structure and the ratio of MoSe2: AuNPs, a sensitivity of 5117.59 nm/RIU has been obtained, which is more than double that of the only Au-filmed optical fiber SPR sensor. A large surface area was produced by integrating the MoSe2 primitive unit cell and the AuNPs into a hybrid plasmonic nanostructure of MoSe2@AuNPs, leading to optical fiber SPR signal amplification. The nanostructure of MoSe2@AuNPs was surrounded by the PDA layer to guarantee the efficient immobilization of the protein molecules on the optical fiber by strong covalent bond. This biosensor achieved a detection limit of 54.05 ng/mL for detecting the goat-anti-rabbit IgG, which demonstrated enhancements of 12.1%, 23.3% and 184.6% in comparison with three reported SPR biosensors decorated with PDA-AuNPs-PDA, PDA and Cysteamine-MoSe2@AuNPs-Cysteamine nanostructure, respectively. This biosensor achieved favorable selectivity and outstanding sensitivity compared with the reported SPR immuno-sensors, which will provide a miniaturized, rapid-response and label-free optical fiber bio-sensing platform for clinical diagnosis in the future.

Pyridinium porphyrins and AuNPs mediated bionetworks as SPR signal amplification tags for the ultrasensitive assay of brain natriuretic peptide

Extension of the self-assembled bionanonetworks into surface plasmon resonance (SPR) assay investigation provides an effective signal amplification approach. Wefabricated a bionetwork by nucleic acids, organic compounds, and supramolecular gold nanoparticles for ultrasensitive SPR detection of B-type natriuretic peptide (BNP). The SPR method was developed by a sandwich-type format of aptamer-target-antibody, and the aptamer-modified bionanonetworks induced localized SPR and large refractive index for different concentrations of the target BNP. The linear concentrationrange and limit of detection were 1-10,000pg/mL (R2 = 0.9852) and 0.3pg/mL respectively. The detection recovery wasin the range 92.13 to 108.69%. The approach embraces the following main advantages: (1) Cooperative double recognition was realized by calix[4]arenes for amino aptamers and pyridinium porphyrins. (2) The approach provided the specificity for supramolecular-based nanomaterials and a simple synthesis process via the ordered self-assembly under mild conditions. (3) The bionanonetworks endowed the SPR assay with signal amplification and stable determination for trace proteins. Therefore, it is expected that this study may offer a new SPR signal-amplified platform of organic-inorganic bionanonetworks to achieve sensitive, stable, and real-time determination. Graphical abstract Schematic of bionanonetwork based on porphyrin-mediated functionalized gold nanoparticles for SPR signal amplification to quantitatively detect BNP.

Surface Plasmon Resonance Signal Amplification Using Secondary Antibody Interaction for Illegal Compound Detection

The development of highly selective and sensitive surface plasmon resonance (SPR) immunoassay for the rapid detection of illegal compound using secondary antibody interaction labelled nanoparticle was conducted. For the construction of SPR sensor surface, the illegal compound (clenbuterol) was immobilized as antigen onto gold succinimide-terminated monolayer to perform amide-coupling reaction. In order to avoid non-specific reaction, the blocking agent (ethanol amine) was injected to the SPR system. Furthermore, indirect competitive inhibition method was employed in the detection of clenbuterol. In this work, the antibody solution (PBS solution containing clenbuterol antibody) premixed with a sample solution (PBS solution containing antigen) before the injection into the sensing system. As the premixed solution flowed over the sensor surface, the SPR senses the dielectric constant change at the interface due to the binding of the unreacted primary antibody to antigen-immobilized on the sensor surface. After this primary antibody detection, secondary antibody was injected to the SPR sensor surface. Here, we compared the signal difference of secondary antibody injection labelled Au nanoparticles (d = 40 nm). For the regeneration of the sensor surface, 0.1 M NaOH was used, so primary and secondary antibodies could be detached from the sensor surface. According to the indirect competitive inhibition method, it was found that the sensitivity for clenbuterol detection was enhanced from 2.5 ppt to 0.07 ppt.

MicroRNA detection on microsensor arrays by SPR imaging measurements with enzymatic signal enhancement

We investigated sequence-specific and simultaneous microRNA (miRNA) detections by surface plasmon resonance (SPR) imaging measurements on SPR chips possessing an Au spot array modified with probe DNAs based on a miRNA-detection-selective SPR signal amplification method. MiRNAs were detected with the detection limit of the attomole level by SPR imaging measurements for different miRNA concentrations on a single chip. SPR signals were enhanced based on a combination process of sequence-specific hybridization of the miRNA to the probe DNAs, extension reaction of polyadenine (poly(A)) tails by poly(A) polymerase, binding of a ternary complex of T30-biotin/horseradish peroxidase (HRP)-biotin/streptavidin to the poly(A) tails, and the oxidation reaction of tetramethylbenzidine (TMB) on the HRP by providing a blue precipitate on the surface. This process sequence-specifically and dramatically amplified the SPR signals. This is a simple, cost-effective, and feasible signal amplification method based on the organic compound TMB instead of metal nanoparticles.

Surface plasmon resonance: a versatile technique for biosensor applications.

Surface plasmon resonance (SPR) is a label-free detection method which has emerged during the last two decades as a suitable and reliable platform in clinical analysis for biomolecular interactions. The technique makes it possible to measure interactions in real-time with high sensitivity and without the need of labels. This review article discusses a wide range of applications in optical-based sensors using either surface plasmon resonance (SPR) or surface plasmon resonance imaging (SPRI). Here we summarize the principles, provide examples, and illustrate the utility of SPR and SPRI through example applications from the biomedical, proteomics, genomics and bioengineering fields. In addition, SPR signal amplification strategies and surface functionalization are covered in the review.

Ochratoxin A immunoassay with surface plasmon resonance registration: Lowering limit of detection by the use of colloidal gold immunoconjugates

An immunoanalytical system was developed for the determination of ochratoxin A with the use of a surface plasmon resonance (SPR) sensor amplified by the anti-species antibody–colloidal gold particle (CGP) conjugate. The use of the binding of immune complexes to the CGP–anti-species antibody conjugate leads to the SPR signal amplification by a factor of more than 10 and results in the 60 pg/mL limit of detection of ochratoxin A with an assay time of 30 min. These characteristics are superior to those obtained both in the conventional enzyme immunoassay with the use of the same reagents and the SPR assay with unmodified antibodies and specific antibodies conjugated to colloidal gold.

Surface-enhanced localized surface plasmon resonance biosensing of avian influenza DNAhybridization using subwavelength metallic nanoarrays

We demonstrated enhanced localized surface plasmon resonance (SPR) biosensing based onsubwavelength gold nanoarrays built on a thin gold film. Arrays of nanogratings (1D) andnanoholes (2D) with a period of 200 nm were fabricated by electron-beam lithography andused for the detection of avian influenza DNA hybridization. Experimental results showedthat both nanoarrays provided significant sensitivity improvement and, especially, 1Dnanogratings exhibited higher SPR signal amplification compared with 2D nanohole arrays.The sensitivity enhancement is associated with changes in surface-limited reaction area andstrong interactions between bound molecules and localized plasmon fields. Our approach isexpected to improve both the sensitivity and sensing resolution and can be applicable tolabel-free detection of DNA without amplification by polymerase chain reaction.

Enzymatically biocatalytic precipitates amplified antibody–antigen interaction for super low level immunoassay: An investigation combined surface plasmon resonance with electrochemistry

We demonstrated a simple and efficient strategy, which based on the enzymatically biocatalytic precipitates amplified antibody–antigen interaction, for improving the response signals of surface plasmon resonance (SPR) immunosensing. The antibody–antigen-alkaline phosphatase (AP) labeled secondary antibody sandwich were successfully prepared and characterized by SPR, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The SPR signal amplification was accomplished through probing resonance angle shift and Faradaic electron impedance of [Fe(CN) 6] 3−/4− redox pair after the enzymatically biocatalytic products precipitating on the immunosensing electrode surface. As a result, the accumulation of the enzymatically biocatalytic precipitates leads to significantly resonance angle shift and increase of electron transfer impedance of [Fe(CN) 6] 3−/4− probe. The precipitates-enhanced sandwich SPR immunoassay for mouse immunoglobulin G (m-IgG) can easily detect solution protein concentrations in the linear range of 0.02–40 ng mL −1 and with a detection limit of 200 fg mL −1, which is more than four-orders and 10 times better compared with the values using streptavidin–biotinylated protein complex and biotinylated HRP biocatalyzation amplification methods. Moreover, this method is generally applicable to other sandwich immunoassays and also can be expanded to monitor other antibody–antigen interaction for immunosensing detection at low concentrations.