Surface Plasmon Resonance Signal Research Articles

Smartphone-based selective and sensitive detection of vitamin B1 in synthetic urine using U-bend SPR optical fiber probe

This paper introduces an innovative optical fiber surface plasmon resonance (SPR) biosensor designed for smartphone assistance, aiming at detecting vitamin B1 in synthetic urine. The key novelty lies in the amalgamation of silver nanocoated cysteine with a gold-plated optical fiber probe, fostering efficient detection through the robust electrostatic interaction between negatively charged Cys-capped AgNPs and positively charged vitamin B1 molecules. Notably, this biosensor leverages the smartphone's digital camera capabilities to discern varying color intensities. A self-developed application ensures real-time monitoring of green and red channel intensities in the SPR signal, thereby mitigating the risk of false detections. Moreover, the integration of the fabricated optical fiber probe with the smartphone is achieved through a 3D-printed casing, endowing the biosensor with the advantages of portability, handheld operation, and cost-effectiveness. The proposed U-shaped optical fiber SPR biosensor, coupled with smartphone technology, demonstrates the ability to detect vitamin B1 within the concentration range of 2–10 μM, yielding a commendable R2 value of 0.9973. Experimental findings affirm that this novel biosensor, built on the U-shaped SPR optical fiber architecture and empowered by smartphones, is an economical, uncomplicated, and portable device adept at accurately and efficiently detecting vitamin B1 across a broad concentration spectrum. Its potential applications extend to the area of low-cost biochemical component identification.

Study of cell and drug interactions based on dual-mode detection using SPR and fluorescence imaging

The investigation of the interactions between cells and drugs forms a crucial aspect of biological and clinical medical studies. Generally, single-cell or local-cellular studies require a microscopic imaging system with high magnifications, which suffers from low detection throughputs and poor time responses. The study presented in this paper combined SPR and fluorescence to achieve cell localization, real-time monitoring of cell images and quantitative analysis of drugs. In order to obtain more comprehensive, accurate and real-time data, a dual-mode system based on surface plasmon resonance (SPR) and fluorescence was constructed based on a 4× magnification lens. This enables simultaneous studies of an entire cell and a specific region of the cell membrane. An adaptive adjustment algorithm was established for distorted SPR images, achieving temporal and spatial matching of the dual-mode detection. The combination of SPR and fluorescence not only achieved micro-detection but also complemented the qualitative or quantitative limitations of SPR or fluorescence method alone. In system characterization, the response signal of SPR was noticed to increase with the increasing concentration of EGF in stimulated cells. It indicated that this platform could be employed for quantitative detection of the cell membrane region. Upon addition of EGF, a peak in the SPR curve was observed, and the cells in the corresponding SPR image turned whiter. This indicated that the platform can simultaneously monitor the SPR response signal and image changes. The response time of fluorescence in EGF testing was several seconds earlier than SPR, revealing that signal transduction first occurred in the whole cell and then propagated to the cell membrane region. The inhibitory ability of Gefitinib on cells was verified in a fast and real-time manner within 20 min. The results indicated that the detection limit of this method was 20 IU/mL for EGF and 10 µg/mL for Gefitinib. In conclusion, this study demonstrates the advantages of SPR and fluorescence dual-mode techniques in the analysis of cell-drug interactions, as well as their strong potential in drug screening.

Ultrasound assisted biogenic synthesis of Palladium nanoparticles using Cocculus hirsutus leaf extract: Antimicrobial, anti-inflammatory and catalytic activities

We have synthesized palladium nanoparticles (PdNPs) from aqueous leaf extract of Cocculus hirsutus (CH) by ultra-sonication in an easy, non-toxic, and eco-friendly manner. PdNPs synthesized were analyzed using UV–vis, FT-IR, powder XRD, TEM, and DLS instruments. From UV–vis spectra, the Surface Plasmon Resonance (SPR) signal indicated that the formation of PdNPs. The synthesized PdNPs shows spherical shape, crystalline and polydispersibility nature with a mean particle size of 10±3 nm was observed from XRD and TEM. FTIR analysis reveals the active role of phenolic constituents from CH leaf extract in reduction and surface functionalization of nanoparticles. The stability of the PdNPs was assessed by devious the Zeta potential analysis. The as-prepared PdNPs showed antibacterial efficacy (maximum zone of inhibition is 11.20 mm for S. typhimurium) and antifungal efficacy (maximum zone of inhibition is 32.80 mm for C. albicans) against disease causing human pathogens, strong anti-inflammatory activity for BSA denaturation and blistering catalytic activity against 4-NP reduction up to 5 cycles (6 min; 100 % reduction, rate constant is 0.532 min−1). The potency of the anti-inflammatory activity was found to be 90 % using PdNPs against the standard drug Diclofenac sodium (90 %) for 500 µg/mL. The above mentioned activities were used to evaluate the effectiveness of the PdNPs in treating bacterial, inflammation related conditions and also as an effective catalyst in wastewater treatment.

Unraveling the Dynamics of SARS-CoV-2 Mutations: Insights from Surface Plasmon Resonance Biosensor Kinetics.

Surface Plasmon Resonance (SPR) technology is known to be a powerful tool for studying biomolecular interactions because it offers real-time and label-free multiparameter analysis with high sensitivity. This article summarizes the results that have been obtained from the use of SPR technology in studying the dynamics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mutations. This paper will begin by introducing the working principle of SPR and the kinetic parameters of the sensorgram, which include the association rate constant (ka), dissociation rate constant (kd), equilibrium association constant (KA), and equilibrium dissociation constant (KD). At the end of the paper, we will summarize the kinetic data on the interaction between angiotensin-converting enzyme 2 (ACE2) and SARS-CoV-2 obtained from the results of SPR signal analysis. ACE2 is a material that mediates virus entry. Therefore, understanding the kinetic changes between ACE2 and SARS-CoV-2 caused by the mutation will provide beneficial information for drug discovery, vaccine development, and other therapeutic purposes.

Advancing Sensitivity in Guided-Wave Surface Plasmon Resonance Sensor through Integration of 2D BlueP/MoS2 Hybrid Layers.

The surface plasmon resonance (SPR) signal, generated from the Kretschmann configuration, has been developed as an effective detection technology in chemical and biological sensors. The sensitivity of SPR signals to changes in the surrounding media makes it a valuable tool, as even a slight variation in refractive index can cause a significant change in SPR signals, such as phase, intensity, and resonance angle. However, the detection of ultralow changes in refractive index, which occur in chemical reactions or biological actions, remains a challenge for conventional SPR sensors due to their limited sensitivity. To overcome this limitation, we theoretically propose a novel guided-wave SPR (GWSPR) configuration coated with a few-layer blue phosphorene (blueP)/MoS2 hybrid structure. This configuration aims to enhance the electric field and subsequently achieve a significant improvement in sensitivity. The results of our study demonstrate that the proposed blueP/MoS2-based GWSPR sensor exhibits a high sensitivity of 290°/RIU, which represents an impressive enhancement of approximately 82.4% compared to the conventional Au-based SPR sensor. This advancement addresses the challenge of detecting ultralow changes in refractive index and offers significant potential for enhancing the performance of chemical and biological sensors.

Blue-emitting SiO2-coated Si-doped ZnSeS quantum dots conjugated aptamer-molecular beacon as an electrochemical and metal-enhanced fluorescence biosensor for SARS-CoV-2 spike protein

The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which was first reported in early January 2020, continues to devastate the worlds public health system. Herein, we report on the development of a novel metal-enhanced fluorescence (MEF) and electrochemical biosensor for SARS-CoV-2 spike (S) protein. To develop the MEF biosensor, SiO2-coated Si-doped ZnSeS quantum dots (QDs) were newly synthesized and conjugated to an aptamer-molecular beacon (Apta-MB) probe. Thereafter, cationic AuNPs, used as a localised surface plasmon resonance (LSPR) signal amplifier, were self-assembled on the QDs-Apta-MB conjugate to form a QDs-Apta-MB-AuNP probe. To develop the electrochemical biosensor, the QDs-Apta-MB assay was carried out on a carbon nanofiber-modified screen-printed carbon electrode. Cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were used to characterize the electrode surface whilst spectrophotometric, spectroscopic, fluorescence polarization and electron microscopic techniques were used to characterize the materials. Under optimal experimental conditions, the QDs binding to the Apta-MB, quenched the QDs’ fluorescence and with SARS-CoV-2 S protein binding to the Apta-MB, LSPR signal from cationic AuNPs of different sizes and shapes were used to tune the fluorescence signal to obtain enhanced sensitivity. On the other hand, using [Fe(CN)6]/K3−/4- buffered with NaAc-KAc-TrizmaAc-KSCN-Borax as the electrolyte solution, anodic peaks of the QDs from the CV and DPV plots were unravelled. Electrochemical detection of SARS-CoV-2 S protein was accomplished by a systematic increase in the QDs anodic peak current generated from the DPV plots. The limits of detection obtained for the SARS-CoV-2 S protein were 8.9 fg/mL for the QDs-Apta-MB-AuNP MEF probe and ∼0.5 pg/mL for the QDs-Apta-MB electrochemical probe. Detection of SARS-CoV-2 S protein in saliva was demonstrated using the QDs-Apta-MB-AuNP MEF probe.

Localized surface plasmon resonance properties dependence of green-synthesized Fe3O4/Ag composite nanoparticles on Ag concentration and an electric field for biosensor application

The use of green-synthesized Fe3O4/Ag composites nanoparticles (NPs) on the surface plasmon resonance (SPR) system induced by the electric field generates the effect of electrooptic-localized surface plasmon resonance (EO-LSPR). EO-LSPR is the promising method to increase dispersibility, generate plasmons, bind to biomolecular targets, modify the refractive index, and increase the SPR signal. Green synthesis of Fe3O4/Ag NPs has several advantages, including being environmentally friendly, cost-effective, and sustainable. This research successfully investigated the EO-LSPR properties of green-synthesized Fe3O4/Ag NPs with various Ag concentrations. Green synthesis of Fe3O4/Ag composites NPs was prepared utilizing Moringa oleifera by an aqueous solution method. The EO-LSPR phenomenon was investigated by applying various voltages in the Kretschmann configuration with a layer arrangement of a prism/Au thin film/NPs/air with a wavelength of 632.8 nm. Transmission electron microscope results show that the average size of Fe3O4/Ag particles is around 16.72 ± 7.30 nm. The scanning electron microscopy-energy dispersive x-ray results showed that Ag was distributed on the surface of Fe3O4. The addition of Ag concentration decreased the saturation magnetization while the coercivity field increased. The SPR angle of the prism/Au thin film/air layer structures is 44.66°. After depositing with Fe3O4/Ag with an Ag concentration of 60 millimolar, the LSPR angle shifted by 0.98°. Under an electric field, the LSPR angle shifted to 1.00°, 1.17°, and 1.22° of 2 volts, 4 volts, and 6 volts, respectively. The results show that applying the electric field induces the LSPR angle of Fe3O4/Ag NPs to shift to a larger angle. Applying an electric field causes a change in the material's refractive index. The greater the applied electric field, the more significant the LSPR angle shifts. The significant shifts in the LSPR angle due to the application of an electric field indicate that the EO-LSPR system using green-synthesized Fe3O4/Ag composites NPs could be a promising alternative to increase the performance of SPR biosensors in the future.

High linearity temperature-compensated SPR fiber sensor for the detection of glucose solution concentrations

In the realm of optical fiber sensing, conventional surface plasmon resonance (SPR) sensors often face challenges due to their low linearity, broad resonance, and susceptibility to external temperature changes. To that end, we evaluate a groundbreaking approach with a temperature-compensating SPR biosensor based on the Mach-Zehnder interferometer (MZI), featuring a novel tapered multimode fiber-single mode fiber-multimode fiber (MMF-SMF-MMF) architecture. Specifically, the SPR is excited on a silver film modified by reduced graphene oxide (rGO) and π-π stacked pyrene-1-boric acid providing specific glucose binding ability. The MZI effect compensating for ambient temperature influence on the SPR is realized with the MMF-SMF-MMF structure. The study also explores the use of Fast Fourier Transform (FFT) for separate, granular analysis of the MZI and SPR signals and improves the linearity of the sensor using a novel centroid-fitting technique. This method utilizes the shift of calculated centroid coordinates rather than the single dip resonance wavelength from SPR, enhancing the overall performance of the sensor. The experimental results demonstrate excellent glucose sensitivity of 2.819 nm/mM, a linear range of 0–10 mmol/L, a LOD of 0.12 mM/L and concurrent temperature compensation. Compact and easy to fabricate, the proposed SPR sensor provides a novel solution for accurate glucose concentration detection in human blood.

Separation of shifts in surface plasmon resonance into refractive index and thickness of deposited layers

Routine Surface Plasmon Resonance (SPR) measurements, which are widely applied in affinity (bio)sensors and surface science, do not allow one to separate the obtained SPR signals into the change of the refractive index and thickness of deposited layers. For thin layers the signal is proportional to the product of the layer thickness and the difference in the refractive indices of this layer and of the aqueous media. In this study, we suggest an approach to separate these parameters. It is performed by subsequent measurements in the presence and in the absence of polyethylene glycol (PEG), an inert additive which modifies the refractive index of the liquid phase but do not penetrate into the adsorbed layer. Both parameters were successively determined for human serum albumin (HSA) as well as for anti-HSA IgG in three different settings: i) HSA adsorbed directly onto a gold surface, ii) HSA chemically immobilized on a gold surface coated with a self-assembled monolayer of 1,16 mercaptohexadecanoic acid and iii) chemically immobilized HSA with additional monomolecular layer of anti-HSA IgG antibodies bond to this protein layer. The suggested approach can be applied in most SPR devices with a flow cell for analysis of various adsorbed layers.

Au-strip structure dependent performance investigation of D-shaped SPR sensors for biosensing applications

Surface Plasmon Resonance (SPR)-based sensing technologies show great promise in diverse applications (e.g. biosensing) as one of the most innovative and exciting label-free sensing techniques in the last few years. In general, SPR-based sensors combine metal and dielectric interfaces, where the oscillation of metal’s free electrons occurs by the incident incoming photons. Thus, the SPR signal strength depends on the metal’s optical properties as well as the surrounding dielectric medium. This work thoroughly investigates the performance of a single mode D-shape SPR-based refractive index (RI) sensor with its gold (Au) strip topology to improve the detection sensitivity. Seven distinct Au strip designs: single-arc, inverted single-arc, multi-arc, inverted multi-arc, half-circle, coil, and sinusoidal wave are introduced to explore sensor performances, which are investigated numerically using Comsol Multiphysics. Systematic investigations are carried out for all seven proposed designs and relative comparisons are made in terms of sensitivity (wavelength and amplitude), resolution, and figure of merit (FoM). Coil and sinusoidal wave-shaped designs show excellent performance among all seven designs with a wide range of analytes’ RI (i.e. 1.31 to 1.39). The maximum wavelength and amplitude sensitivities are found to be 48000 nm/RIU and 18.55 RIU−1 respectively, with a wavelength resolution of 2.08 × 10-6 RIU and a consequent FoM of 141.18 RIU−1 for the sinusoidal wave-shaped Au-strip design. Alternatively, the coil-shaped design shows the maximum wavelength and amplitude sensitivities of 45000 nm/RIU and 32.17 RIU−1 respectively, with a wavelength resolution of 2.22 × 10-6 RIU and a FoM of 85.71 RIU−1. As a wide range of analyte’s RI can be detected by the proposed sinusoidal wave and coil Au-strip-based D-shaped sensors with improved sensitivity, these designs could be effectively used for the detection of different bio-analytes.

Development and Analysis of Multifeature Approaches in SPR Sensor Development

This paper presents the development and signal analysis of surface plasmon resonance (SPR)-based sensors in D-shaped polymer optical fibers (POFs). A gold-palladium (Au-Pd) coating was applied to the D-shaped region to obtain the SPR signal in the transmitted spectrum of the POFs, where different samples were fabricated using the same methods and parameters. In this case, the transmitted spectra of three sets of samples were compared, which indicated variations in the SPR signature that can influence the sensors’ application and reproducibility. Then, the intensity of and wavelength shift in the SPR signals were analyzed as a function of the refractive index variation, where it was possible to observe differences in the sensors’ sensitivities and the linearity of the different samples. In this regard, additional features, namely the area below the curve and the peak amplitude of the fast Fourier transform (FFT) applied to the transmitted spectra, were used to enhance the sensors’ accuracy and precision. To verify the use of such additional features in the sensor analysis, an unsupervised approach based on k-means clustering was used considering a single dataset with the results of all the sensors. The results showed clustering with the number of different refractive indices tested, which motivated the use of these features (intensity, wavelength, area and FFT amplitude) in the refractive index assessment. In this context, random forest was the supervised algorithm with the smallest root mean squared error (RMSE) among the algorithms tested, where an RMSE of 0.0057 was obtained considering all the datasets. For the analysis of each sensor (considering the three sets of sensor samples), the mean RMSE using random forest applied to the multifeature approach returned relative errors below 9%, considering the entire tested range of refractive index variation.

Tunable Au@SiO2/Au Film Metasurface as Surface Plasmon Resonance Enhancer for Direct and Ultrasensitive Detection of Exosomes.

Surface plasmon resonance (SPR) spectroscopy with non-labelling, sensitive, and real-time properties is critical for clinical diagnosis applications. However, conventional SPR sensors face the challenge of lower sensitivity and selectivity for trace exosomes assay in complex serum. We proposed a core-shell Au@SiO2-Au film (Au@SiO2-Au film) metasurface to enhance SPR signal based on systematic study on the relationship between gap modes and SPR enhancement. The self-assembled multifunctional peptide was designed as recognition layer with antifouling properties for ultrasensitive and selective detection of PD-L1+ exosomes in serum. The tuning electromagnetic (EM) field model by manipulating the gap was established to guide the preparation of Au@SiO2-Au film metasurface. The in-plane and out-of-plane coupling of Au@SiO2 nanoparticles (NPs) could greatly enlarge and enhance three-dimensional EM field to meet the size of exosomes located in the evanescent field. At the structural level, we achieved high sensitivity (0.16 particles/mL) and a broad response range (10-5 × 103 particles/mL) through optimizing the thickness of SiO2 and surface coverage of Au@SiO2. Furthermore, clinical sample assay achieved the optimal diagnostic accuracy (AUC = 0.97) for differentiating cancer patients from healthy controls. This work provides an opportunity for the construction of a tunable gap mode as SPR enhancer in a total internal reflection architecture. The systematic study on the relationship between gap modes and SPR sensitivity provides a broad scope for promoting direct, efficient, highly selective, and sensitive detection of SPR sensors for clinical application.

Wavelength sequential selection technique for high-throughput multi-channel phase interrogation surface plasmon resonance imaging sensing.

Phase interrogation surface plasmon resonance (P-SPR) biosensors have the highest sensitivity among different types of surface plasmon resonance (SPR) biosensors. However, P-SPR sensors have small dynamic detection range and complex device configuration. To solve these two problems, we designed a multi-channel P-SPR imaging (mcP-SPRi) sensing platform based on a common-path ellipsometry scheme. A wavelength sequential selection (WSS) technique for P-SPRi sensing is developed to select the optimal sensing wavelengths according to different refractive indexes (RIs) of the samples, so the inconsistency of SPR signal response for different biomolecule types caused by the small dynamic detection range is eliminated. And a dynamic detection range of 3.7×10-3 RIU is achieved, which is the largest among the current mcP-SPRi biosensors. Remarkably, the individual SPR phase image acquisition time has been greatly reduced to 1s by using WSS method instead of whole spectrum scanning, which enables the high-throughput mcP-SPRi sensing.

GREEN-SYNTHESIS OF SILVER NANOPARTICLES: SPECTRAL, OPTICAL, AND ANTIBACTERIAL CHARACTERIZATION STUDIES

A green approach was used for synthesizing Silver-NPs by the extract of Artocarpus heterophyllus leaves. The effect of Artocarpus heterophyllus leaf extract was investigated. A powder XRD study has been used to analyze the structure and particle size of as-synthesized Ag-NPs. According to the powder-XRD study, the as-prepared Silver-NPs possess an FCC structure and have a particle size of 23nm. The possible bio-reducing agents within the leaf extracts were confirmed using FTIR spectral analysis. The characteristic surface plasmon resonance signal of the as-synthesized silver nanoparticles was detected at 418 nm using UV–Vis spectroscopic analysis between the wavelength range of 300 and 800nm. An emission peak was observed at 472nm in the PL investigation, indicating the fluorescent emission of Ag-NPs. The FESEM analysis has been exploited to inspect the morphological aspect of biosynthesized silver-NPs. According to FESEM micrographs, the biosynthesized NPs were found to have spherical shapes. Using the agar-well process, the antibacterial efficacy of biosynthesized Silver-NPs was examined. The prepared Silver-NPs exhibited a better antibacterial efficacy against E.coli than against S.typhi. It's also been observed that when the concentration increased, the antibacterial activity increased as well.

Numerical Analysis of Highly Sensitive Twin-Core, Gold-Coated, D-Shaped Photonic Crystal Fiber Based on Surface Plasmon Resonance Sensor.

This research article proposes and numerically investigates a photonic crystal fiber (PCF) based on a surface plasmon resonance (SPR) sensor for the detecting refractive index (RI) of unknown analytes. The plasmonic material (gold) layer is placed outside of the PCF by removing two air holes from the main structure, and a D-shaped PCF-SPR sensor is formed. The purpose of using a plasmonic material (gold) layer in a PCF structure is to introduce an SPR phenomenon. The structure of the PCF is likely enclosed by the analyte to be detected, and an external sensing system is used to measure changes in the SPR signal. Moreover, a perfectly matched layer (PML) is also placed outside of the PCF to absorb unwanted light signals towards the surface. The numerical investigation of all guiding properties of the PCF-SPR sensor is completed using a fully vectorial-based finite element method (FEM) to achieve the finest sensing performance. The design of the PCF-SPR sensor is completed using COMSOL Multiphysics software, version 1.4.50. According to the simulation results, the proposed PCF-SPR sensor has a maximum wavelength sensitivity of 9000 nm/RIU, an amplitude sensitivity of 3746 RIU-1, a sensor resolution of 1 × 10-5 RIU, and a figure of merit (FOM) of 900 RIU-1 in the x-polarized direction light signal. The miniaturized structure and high sensitivity of the proposed PCF-SPR sensor make it a promising candidate for detecting RI of analytes ranging from 1.28 to 1.42.

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.

Nanoscale Adsorption, Assembly, and Deionization Dynamics Recorded by Optical Fiber Sensors.

Capacitive deionization in environmental decontamination has been widely studied and now requires intensive development to support large-scale deployment. Porous nanomaterials have been demonstrated to play pivotal roles in determining decontamination efficiency and manipulating nanomaterials to form functional architecture has been one of the most exciting challenges. Such nanostructure engineering and environmental applications highlight the importance of observing, recording, and studying basically electrical-assisted charge/ion/particle adsorption and assembly behaviors localized at charged interfaces. In addition, it is generally desirable to increase the sorption capacity and reduce the energy cost, which increase the requirement for recording collective dynamic and performance properties that stem from nanoscale deionization dynamics. Herein, we show how a single optical fiber can serve as an in situ and multifunctional opto-electrochemical platform for addressing these issues. The surface plasmon resonance signals allow the in situ spectral observation of nanoscale dynamic behaviors at the electrode-electrolyte interface. The parallel and complementary optical-electrical sensing signals enable the single probe but multifunctional recording of electrokinetic phenomena and electrosorption processes. As a proof of concept, we experimentally decipher the interfacial adsorption and assembly behaviors of anisotropic metal-organic framework nanoparticles at a charged surface and decouple the interfacial capacitive deionization within an assembled metal-organic framework nanocoating by visualizing its dynamic and energy consumption properties, including the adsorptive capacity, removal efficiency, kinetic properties, charge, specific energy consumption, and charge efficiency. This simple "all-in-fiber" opto-electrochemical platform offers intriguing opportunities to provide in situ and multidimensional insights into interfacial adsorption, assembly, and deionization dynamics information, which may contribute to understanding the underlying assembly rules and the exploring structure-deionization performance correlations for the development of tailor-made nanohybrid electrode coatings for deionization applications.

An ultra-sensitive SPR immunosensor for quantitative determination of human cartilage oligomeric matrix protein biomarker

This paper reports the development of a novel surface plasmon resonance (SPR) immunosensor for ultra-sensitive quantitative determination of human articular cartilage oligomeric matrix protein (COMP), a major component of the extracellular matrix and an exploratory biomarker. Capture antibodies against human COMP (anti-COMP16F12) were covalently immobilized on an 11-mercaptoundecanoic acid (11-MUA) self-assembled monolayer (SAM)-coated SPR sensor disk and a dual sandwich-type signal amplification strategy using biotinylated detection antibodies against COMP (anti-COMP17C10-biot) and streptavidin-conjugated quantum dots (SAv‒QDs) were used for the development of an immunosensor. The binding of high-mass SAv‒QDs via biotin–streptavidin interaction to the surface of the immunosensor resulted in a drastic increase in the sensitivity. The developed immunosensor was able to detect concentrations of COMP in a range from 2.80 to 680.54 fM with a limit of detection (LOD) and a limit of quantification (LOQ) of 0.15 and 0.50 fM, respectively. The immunosensor exhibited good repeatability (relative standard deviation (RSD) 8.05%) and reproducibility (RSD 9.88%) as well as excellent operational stability (2.14 % decrease in SPR signal after 13 days). In addition, the analysis of secretomes of human knee articular cartilage explants from patients with osteoarthritis revealed that the immunosensor has good accuracy (analytical error less than 5 %). These results indicate that the immunosensor developed may be suitable for quantitative determination of COMP derived from articular cartilage and other synovial joint tissues in clinical studies.

In-situ detection scheme for EGFR gene with temperature and pH compensation using a triple-channel optical fiber biosensor

An advanced multi-parameter optical fiber sensing technology for EGFR gene detection based on DNA hybridization technology is demonstrated in this paper. For traditional DNA hybridization detection methods, temperature and pH compensation can not be realized or need multiple sensor probes. However, the multi-parameter detection technology we proposed can simultaneously detect complementary DNA, temperature and pH based on a single optical fiber probe. In this scheme, three optical signals including dual surface plasmon resonance signal (SPR) and Mach-Zehnder interference signal (MZI) are excited by binding the probe DNA sequence and pH-sensitive material with the optical fiber sensor. The paper proposes the first research to achieve simultaneous excitation of dual SPR signal and Mach-Zehnder interference signal in a single fiber and used for three-parameter detection. Three optical signals have different sensitivities to the three variables. From a mathematical point of view, the unique solutions of exon-20 concentration, temperature and pH can be obtained by analyzing the three optical signals. The experimental results show that the exon-20 sensitivity of the sensor can reach 0.07 nm nM−1, and the limit of detection is 3.27 nM. The designed sensor gives a fast response, high sensitivity, and low detection limit, which is important for the field of DNA hybridization research and for solving the problems of biosensor susceptibility to temperature and pH.

Abstract LB180: SPOC, A highly multiplexed platform to study the kinetics of hundreds of biomolecular interactions: applications for early cancer detection

Abstract Tissue specific tumor neo-antigens and tumor associated antigens (TAAs) play a pivotal role in immune system interaction with cancer cells. Mutated, alternately spliced, over-expressed, mis-folded and abnormally post-translationally modified proteins may elicit immune responses that suppress tumor development. As these cancer specific proteins are distinct from normal self-proteins they offer the possibility of serving as highly-specific cancer biomarkers for early detection. TAAs are increasingly being targeted for priming the immune response to immunotherapies and cancer vaccines. Consequently, there has been an exponential increase in research on neo-antigen profiling using sequencing and multi-omic technologies. However, proteomic tools capable of studying and profiling the cancer proteome are limited. To contribute to this, we are developing a novel proteomic screening platform termed Sensor-integrated Proteome on Chip (SPOC) that enables high-throughput (HTP) screening of cancer proteins for loss or gain of function analysis, and humoral immune response profiling. SPOC platform enables use of surface plasmon resonance (SPR) biosensing for kinetic interaction profiling of 100s to 1000s of proteins at once, which can be applied to discovery and characterization of autoantibodies and neoantigens. SPOC uses human cell-free in vitro transcription and translation to express fusion capture-tagged proteins of interest from DNA plasmids printed in nanowells etched into a silicon slide. As proteins are expressed, they are captured covalently onto an overlaid gold-coated surface in individual spots via the capture ligand. The capture ligand requires the tag to be properly folded for binding, thus proteins on the surface are presumed to be fully folded when captured. When SPOC chips are analyzed using SPR, kinetic measurements of protein interactions can be obtained for each protein spot over time (RMax, Kon, Koff, etc.). SPOC arrays may be probed with a variety of biological molecules including small molecule drugs, antibodies, and other proteins. Data can be analyzed using bioinformatics and machine learning for neo-antigen discovery and to generate distinct signatures of disease. To demonstrate SPOC utility for neo-antigen discovery and characterization, a serum sample with known anti-p53 autoantibodies was analyzed on a SPOC SPR chip containing expressed p53 protein spots distributed throughout the array. Increases in SPR signals were observed for each p53 spot on the array as anticipated. Citation Format: Rebecca Cook, Chidozie Victor Agu, William Martelly, Peter A. Bell, Mukilan Mohan, Bharath Takulapalli. SPOC, A highly multiplexed platform to study the kinetics of hundreds of biomolecular interactions: applications for early cancer detection [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB180.