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This study explores the surface plasmon resonance (SPR) and the electromagnetic field responses of multi-layer structures with incident light to enhance the sensitivity and range for measurement of nanoscale thin liquid film thickness. We assess the effect of metal layer type and its corresponding thickness on the optical responses. Notably, the silver (Ag) layer exhibits a more acute reflectance curve with a thickness of 50 nm, which is attributable to the minimization of non-radiative losses and a substantial real component of the dielectric constant of the Ag layer. Furthermore, a correlation between liquid film thickness and reflectance has been established across different metal layer types at specified thicknesses. The Ag layer demonstrates the broadest measurement range for liquid film thickness due to its extensive penetration depth into the dielectric material. Conversely, the sodium (Na) layer presents the narrowest measurement range, albeit with the highest SPR sensitivity. [ABSTRACT FROM AUTHOR]

The present study investigated the impact of incorporating copper nanoparticles (CuNPs) on the optical properties of erbium-doped borate glasses. Through melt-quenching and heat treatment techniques, glasses with varying Cu 2 O concentrations (x = 0–5 mol%) were synthesized. Physical and structural analyses revealed that Cu ions serve as effective network modifiers. They foster the formation of a greater proportion of BO 4 tetrahedra and thus enhancing glass homogeneity. Optical absorption spectra demonstrate a distinct modulation of Er3+ absorption bands with Cu 2 O embedding, indicating the formation of CuNPs, as validated by the emergence of surface plasmon resonance bands. This structural evolution results in a noticeable reduction in the bandgap energy, signifying improved semiconducting behavior. Judd-Ofelt analysis highlighted the profound influence of CuNPs on hypersensitive transitions, thereby affecting oscillator strength. Photoluminescence measurements revealed amplified emission in the visible red and near infrared (NIR) region, attributed to the synergistic effects of CuNPs and Er3+ ions, with 5 mol % Cu 2 O exhibiting the highest emission intensity. Analysis of the radiative properties validates the enhancement of the emission cross-section, gain bandwidth, optical gain and radiative transitions. These enhancements contribute to a notable increase in the branching ratio from 0.91 % to 5.41 % accompanied by an increase in the quantum efficiency from ∼79 % to ∼90 %. Moreover, decay analysis revealed a notable enhancement in lifetime from 3.03 ms to 15.74 ms, which is indicative of enhanced radiative transitions. Overall, the incorporation of CuNPs into erbium-doped borate glasses facilitates significant enhancements in physical, structural, and optical properties. This positions them as promising materials for a wide array of optoelectronic applications. This comprehensive study sheds light on the complex interplay between CuNPs and erbium-barium borate glasses, offering valuable insights for the development of advanced optoelectronic materials with enhanced performance and functionality. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper presents a photonic crystal fiber (PCF) sensor that can be used to measure the temperature and magnetic field simultaneously, and to monitor the changes in them in the environment. When we designed the fiber structure, two circular channels of the same size were added to the fiber to facilitate the subsequent addition of materials. A gold film is added to the upper channel (ch1), and the channel is filled with a magnetic fluid (MF). The sensor can reflect changes in the temperature and magnetic field strength. The two channels containing MF and PDMS in the proposed fiber are called ch1 and ch2. The structure, mode and properties (temperature and magnetic field) were analyzed and discussed using the finite element method. By using the control variable method, the influence of Ta2O5 or no Ta2O5, the Ta2O5 thickness, the diameter of the special air hole, the distance from the fiber core and the distance between them in the displacement of the loss spectrum and the phase-matching condition of the coupling mode were studied. The resulting maximum temperature sensitivity is 6.3 nm/°C (SPR peak 5), and the maximum magnetic field sensitivity is 40 nm/Oe (SPR peak 4). Because the sensor can respond to temperature and magnetic field changes in the environment, it can play an important role in special environmental monitoring, industrial production and other fields. [ABSTRACT FROM AUTHOR]

An optical fiber scale sensor based on the detection principle of surface plasmon resonance (SPR) was developed for the rapid, high-sensitivity, real-time evaluation of scale precipitation in geothermal fluids. The optical fiber SPR scale sensor was fabricated by depositing a gold thin film onto the surface of an optical fiber with an exposed core. The optimal gold film thickness of the sensor was determined to be 30 nm, which achieved a refractive index sensitivity of 2140 nm per refractive index unit. A field test was conducted using geothermal brine from the Obama Binary Geothermal Power Plant in Unzen, Nagasaki Prefecture. A conventional optical fiber scale sensor and the SPR sensor were simultaneously assessed using raw and pH-adjusted brines. For the SPR sensor, a peak shift of 0.27 nm/min was observed at a response time of 1 min, whereas no change in transmittance was observed for the conventional sensor until 180 min. After the experiments, a scanning electron microscopy-energy-dispersive spectroscopy analysis was conducted on the sensors, and the findings showed that the deposition of Mg-SiO2 scale did not significantly differ between the two sensors. The developed SPR sensor achieved faster scale precipitation detection (tens of minutes to hours) than the conventional sensor. [ABSTRACT FROM AUTHOR]

2-Furaldehyde (2-FAL) is one of the main by-products of the degradation of hemicellulose, which is the solid material of the oil–paper insulating system of oil-filled transformers. For this reason, it has been suggested as a marker of the degradation of the insulating system; sensing devices for 2-FAL analysis in a wide concentration range are of high interest in these systems. An optical sensor system is proposed; this consists of a chemical chip, able to capture 2-FAL from the insulating oil, coupled with a surface plasmon resonance (SPR) probe, both realized on multimode plastic optical fibers (POFs). The SPR platform exploits gold nanofilm or, alternatively, a double layer of gold and silicon oxide to modulate the sensor sensitivity. The capturing chip is always based on the same molecularly imprinted polymer (MIP) as a receptor specific for 2-FAL. The system with the SPR probe based on a gold nanolayer had a higher sensitivity and a lower detection limit of fractions of μg L−1. Instead, the SPR probe, based on a double layer (gold and silicon oxide), has a lower sensitivity with a worse detection limit, and it is suitable for the detection of 2-FAL at concentrations of 0.01–1 mg L−1. [ABSTRACT FROM AUTHOR]

The cytokine interleukin-6 (IL-6) plays a crucial role in autoimmune and inflammatory diseases. Understanding the precise mechanism of IL-6 interaction at the amino acid level is essential to develop IL-6-inhibiting compounds. In this study, we employed computer-guided drug design tools to predict the key residues that are involved in the interaction between IL-6 and its receptor IL-6R. Subsequently, we generated IL-6 mutants and evaluated their binding affinity to IL-6R and the IL-6R − gp130 complex, as well as monitoring their biological activities. Our findings revealed that the R167A mutant exhibited increased affinity for IL-6R, leading to enhanced binding to IL-6R − gp130 complex and subsequently elevated intracellular phosphorylation of STAT3 in effector cells. On the other hand, although E171A reduced its affinity for IL-6R, it displayed stronger binding to the IL-6R − gp130 complex, thereby enhancing its biological activity. Furthermore, we identified the importance of R178 and R181 for the precise recognition of IL-6 by IL-6R. Mutants R181A/V failed to bind to IL-6R, while maintaining an affinity for the IL-6 − gp130 complex. Additionally, deletion of the D helix resulted in complete loss of IL-6 binding affinity for IL-6R. Overall, this study provides valuable insights into the binding mechanism of IL-6 and establishes a solid foundation for future design of novel IL-6 inhibitors. [ABSTRACT FROM AUTHOR]

Over the past years, Surface Plasmon Resonance (SPR) has been used in various domains including medical diagnostics, chemical and biological sensing, and environmental monitoring. SPR-based biosensors have more advantages than other optical biosensors due to their rapid, label-free, and targeted detection capabilities. There have been challenges to designing SPR biosensors with enhanced performance and improved environmental adaptability, including considerations such as prism-metal bonding, biomolecule adhesion, and oxidation protection. This paper presents sensitivity and performance enhancement in an SPR biosensor based on Kretschmann configuration while using a low refractive index CaF2 glass prism, a zinc oxide (ZnO) layer, a gold-silver alloy (Au10Ag90), and a single layer of 2D graphene. Theoretical analysis shows that the use of a CaF2 prism and the alloy gives a good sensitivity of 280 ∘ / RIU . The sole addition of a ZnO layer improves this sensitivity to 320 ∘ / RIU . Further addition of a graphene layer to make the final proposed structure CaF2/ZnO/Au10Ag90/graphene/SM, improves sensitivity to 340 ∘ / RIU , giving a figure of merit value of 60.28 / RIU and a quality factor value of 102.48 / RIU . Despite supporting the SPR mode and enhancing sensitivity, ZnO improves prism-alloy bonding while graphene promises better biomolecule adhesion and improved oxidation protection. Overall, our proposed structure has better sensing performance compared to other designs in the literature. The high sensitivity makes our proposed biosensor suitable for the detection of tiny cancer bio-markers in body fluids, enabling early medical interventions. [ABSTRACT FROM AUTHOR]

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In this study, we systematically investigate theoretically and experimentally the plasmonic effect and roles of big and small gold nanoparticles (Au NPs) within a mixed solution. The polydisperse solution was initially prepared by mixing small (10, 30 nm) Au NPs with larger ones (50, 80 nm), followed by measuring the extinction using ultraviolet–visible (UV-vis) spectroscopy. The experimental results clearly showed that the extinction of the mixed solution is predominantly influenced by the presence of the larger NPs, even though their quantity is small. Subsequently, we conducted simulations to explore the plasmonic properties of Au NPs of different sizes as well as their mixings and to validate the experimental results. To explain the deviation of the extinction spectra between experimental observations and simulations, we elaborated a simulation model involving the mixture of spherical Au NPs with ellipsoidal NPs, thus showing agreement between the simulation and the experiment. By performing simulations of plasmonic near-field of NPs, our investigation revealed that the maximal electric field intensity does not occur precisely at the plasmonic resonant wavelength but rather at a nearby redder wavelength. The optimal size of the Au NP dispersed in water for achieving the highest field enhancement was found to be 60 nm, with an excitation wavelength of 553.7 nm. These interesting findings not only enrich our understanding of plasmonic NPs' optical behavior but also guide researchers for potential applications in various domains. [ABSTRACT FROM AUTHOR]

Iron delivery to the plasma is closely coupled to erythropoiesis, the production of red blood cells, as this process consumes most of the circulating plasma iron. In response to hemorrhage and other erythropoietic stresses, increased erythropoietin stimulates the production of the hormone erythroferrone (ERFE) by erythrocyte precursors (erythroblasts) developing in erythropoietic tissues. ERFE acts on the liver to inhibit bone morphogenetic protein (BMP) signaling and thereby decrease hepcidin production. Decreased circulating hepcidin concentrations then allow the release of iron from stores and increase iron absorption from the diet. Guided by evolutionary analysis and Alphafold2 protein complex modeling, we used targeted ERFE mutations, deletions, and synthetic ERFE segments together with cell-based bioassays and surface plasmon resonance to probe the structural features required for bioactivity and BMP binding. We define the ERFE active domain and multiple structural features that act together to entrap BMP ligands. In particular, the hydrophobic helical segment 81 to 86 and specifically the highly conserved tryptophan W82 in the N-terminal region are essential for ERFE bioactivity and Alphafold2 modeling places W82 between two tryptophans in its ligands BMP2, BMP6, and the BMP2/6 heterodimer, an interaction similar to those that bind BMPs to their cognate receptors. Finally, we identify the cationic region 96-107 and the globular TNFα-like domain 186-354 as structural determinants of ERFE multimerization that increase the avidity of ERFE for BMP ligands. Collectively, our results provide further insight into the ERFE-mediated inhibition of BMP signaling in response to erythropoietic stress.

Abstract We developed an all optic-fiber waveguide-coupled surface plasmon resonance (SPR) sensor using zirconium disulfide (ZrS2) and poly-dopamine (PDA) as the dielectric layer and biological cross-linker, respectively. This sensor can be employed to monitor the entire process of the C-reactive protein (CRP) sensing, including antibody modification and antigen detection. The design and the optimization of the optical fiber waveguide-coupled SPR sensor were realized, based on the transfer matrix method and first-principles calculations. The sensor was fabricated and characterized according to the optimized parameters. The experimental setup was implemented to measure the entire process of antibody modification and antigen detection for CRP with the detection limit of 3.21 pmol·mL−1, and the specificity tests were also carried out.

Abstract The cytokine interleukin-6 (IL-6) plays a crucial role in autoimmune and inflammatory diseases. Understanding the precise mechanism of IL-6 interaction at the amino acid level is essential to develop IL-6-inhibiting compounds. In this study, we employed computer-guided drug design tools to predict the key residues that are involved in the interaction between IL-6 and its receptor IL-6R. Subsequently, we generated IL-6 mutants and evaluated their binding affinity to IL-6R and the IL-6R − gp130 complex, as well as monitoring their biological activities. Our findings revealed that the R167A mutant exhibited increased affinity for IL-6R, leading to enhanced binding to IL-6R − gp130 complex and subsequently elevated intracellular phosphorylation of STAT3 in effector cells. On the other hand, although E171A reduced its affinity for IL-6R, it displayed stronger binding to the IL-6R − gp130 complex, thereby enhancing its biological activity. Furthermore, we identified the importance of R178 and R181 for the precise recognition of IL-6 by IL-6R. Mutants R181A/V failed to bind to IL-6R, while maintaining an affinity for the IL-6 − gp130 complex. Additionally, deletion of the D helix resulted in complete loss of IL-6 binding affinity for IL-6R. Overall, this study provides valuable insights into the binding mechanism of IL-6 and establishes a solid foundation for future design of novel IL-6 inhibitors.

The confinement of electrons in gold nanoparticles results in Surface Plasmon Resonance (SPR), which is characterized by electric field enhancement in the vicinity of these nanoparticles. This property has been extensively studied and applied in various fields. In our research, we conduct a detailed investigation of plasmonic coupling in spherical gold nanoparticles. Specifically, we use the Discrete Dipole Approximation (DDA) method implemented in DDSCAT to simulate the coupling of electric fields in a doublet of nanoparticles as a function of the distance between them. Our simulations show that the coupling of SPR between two nanoparticles occurs up to a separation of 12 nm. Moreover, we extend our simulations to study the coupling of nanoparticles in linear chains consisting of up to five nanoparticles and in clustered forms. Our results indicate that the SPR coupling in a linear chain occurs, and as the number of nanoparticles increases, the field enhancement also increases. However, we observe that this effect saturates after four nanoparticles in a line. Our study provides insights into the plasmonic coupling in gold nanoparticles, which can aid in the design and optimization of plasmonic devices for various applications.

Objective·To establish various in vitro screening systems for the discovery of peptide inhibitors targeting the interaction between small ubiquitin-like modifier (SUMO)-activating enzyme subunit 1 (SAE1) and subunit 2 (SAE2), as well as to evaluate their advantages, disadvantages, and applicability to this research.Methods·The DNA fragments encoding human SAE1 and SAE2 were cloned into vector pET-28a, respectively, to generate protein SAE1 and SAE2. Purified proteins were used to establish screening assays, including isothermal calorimetry (ITC), fluorescence polarization (FP), surface plasmon resonance (SPR) and a fluorescence assay based on the SAE enzyme activity. The inhibitory activity of peptide candidates in different screening systems was examined, and their performance in terms of sensitivity, robustness, throughput and cost was evaluated.Results·The dissociation constant (Kd) of in vitro SAE1 and SAE2 interaction was determined to be 0.96 μmol/L by ITC, and PEPT7 was identified as the most potent peptide. However, the tracer of FP, which was derived from PEPT7, was not up to snuff due to its low affinity with SAE2. In the SPR assay, the Kd value (=1.13 μmol/L) of SAE1 and SAE2 interaction was in line with the results from ITC. The SAE enzyme activity-based screening assay revealed that HP1B, the most effective peptide, inhibited SAE with an half-maximal inhibitory concentration (IC50) of 15.72 μmol/L. The affinity of HP1B for SAE1 was determined to be 34.4 μmol/L by SPR.Conclusion·Several common screening systems for protein-protein interation (PPI) inhibitors are established and compared. Among them, ITC does not allow for high-throughput screening and it is difficult to accurately evaluate the low-affinity polypeptides with insignificant binding heat. The feasibility of FP relies heavily on the strong affinity between a tracer peptide and the protein target, making it unsuitable for the screening and optimization of low-affinity peptides. SPR is highly sensitive but the cost is high. The SAE enzyme activity-based assay stands out because it is a combination of high sensitivity, robustness, throughput and acceptable cost.

Silver-based grating structures offer means for implementing low-cost, efficient grating couplers for use in surface plasmon resonance (SPR) sensors. One-dimensional grating structures with a fixed periodicity are confined to operate effectively within a single planar orientation. However, two-dimensional grating structures as well as grating structures with variable periodicity allow for the plasmon excitation angle to be seamlessly adjusted. This study demonstrates silver-based grating designs that allow for the plasmon excitation angle to be adjusted via rotation or beam position. The flexible angle adjustment opens up the possibility of developing SPR sensor designs with an expanded dynamic range and increased flexibility in sensing applications. The results demonstrate that efficient coupling into two diffraction orders is possible, which ultimately leads to an excitation angle range from 16° to 40° by rotating a single structure. The findings suggest a promising direction for the development of versatile and adaptable SPR sensing platforms with enhanced performance characteristics. [ABSTRACT FROM AUTHOR]

This paper proposes a surface plasmon resonance (SPR) biosensor based on the Kretschmann configuration including a bilayer of silver metal (Ag), molybdenum disulfide (MoS2), molybdenum trioxide (MoO3), titanium carbide MXene (Ti3C2Tx), and a BK7 coupling prism. The proposed device is designed as a refractive index sensor for hemoglobin measurement in human blood samples. The finite difference time domain (FDTD) technique has been used to evaluate the performance parameters of the sensor. Silver metal and 2D material thickness is optimized using an angular interrogation technique to minimize reflectance. The proposed biosensor exhibits the maximum sensitivity (S) of 218 deg/RIU, at a sensing medium of 1.32919–1.34919 with Δns = 0.005 RIU. Other parameters a detection accuracy of 0.182 deg−1, a figure of merit of 40.63 RIU−1, and a limit of detection of 4.587 × 10–6 have been obtained. The proposed SPR biosensor effectively increases the strength of the interaction between the incident light and the analyte, resulting in a relatively reduced propagation loss. Therefore, the suggested sensor is a suitable candidate to detect and analyze biomolecules. [ABSTRACT FROM AUTHOR]

In this study, a surface plasmon resonance (SPR) sensor based on modified plastic optical fibers (POFs) was combined with a specific molecularly imprinted polymer (MIP), used as a synthetic receptor, for glyphosate (GLY) determination in aqueous solutions. Since GLY is a non-selective herbicide associated with severe environmental and health problems, detecting glyphosate in environmental and biological samples remains challenging. The selective interaction between the MIP layer and GLY is monitored by exploiting the SPR phenomenon at the POF's gold surface. Experimental results show that in about ten minutes and by dropping microliter volume samples, the presented optical–chemical sensor can quantify up to three orders of magnitude of GLY concentrations, from nanomolar to micromolar, due to a thin MIP layer over the SPR surface. The developed optical–chemical sensor presents a detection limit of about 1 nM and can be used for onsite GLY measurements. Moreover, the experimental analysis demonstrated the high selectivity of the proposed POF-based chemical sensor. [ABSTRACT FROM AUTHOR]

Cortisol is a clinically validated stress biomarker that takes part in many physiological and psychological functions related to the body's response to stress factors. In particular, it has emerged as a pivotal tool for understanding stress levels and overall well-being. Usually, in clinics, cortisol levels are monitored in blood or urine, but significant changes are also registered in sweat and saliva. In this work, a surface plasmon resonance probe based on a D-shaped plastic optical fiber was functionalized with a glucocorticoid receptor exploited as a highly efficient bioreceptor specific to cortisol. The developed plastic optical fiber biosensor was tested for cortisol detection in buffer and artificial saliva. The biosensor response showed very good selectivity towards other hormones and a detection limit of about 59 fM and 96 fM in phosphate saline buffer and artificial saliva, respectively. The obtained detection limit, with a rapid detection time (about 5 min) and a low-cost sensor system, paved the way for determining the cortisol concentration in saliva samples without any extraction process or sample pretreatment via a point-of-care test. [ABSTRACT FROM AUTHOR]

A highly sensitive D-shaped microfluidic channel (MFC) incorporated in a single-mode fiber (SMF) equipped with a tungsten trioxide ( W O 3 ) layer coated with gold (Au) or silver (Ag) on the base of the MFC is designed and investigated utilizing a finite element method (FEM) to obtain the sensing performance of the optical fiber surface plasmon resonance (SPR) structure. The proposed sensor is appropriate for both bimetallic layers and analytes. With the sizeable cladding diameter of SMF, the fluidic channel size can be changed following demand, making fabrication more accessible and applicable. The hollow D-section above the core deposited a bimetallic structure of silver (Ag) or gold (Au) as plasmonic materials, followed by a tungsten trioxide ( W O 3 ) nanolayer. This optical fiber biochemical monitors the changes in the refractive index (RI) by measuring the transmission spectral shifts of the fiber at their resonance wavelengths. The W O 3 layer protects the plasmonic material from oxidation and effectively enhances the surface plasmon wave (SPW) while interacting with free electrons. Upon achieving the optimum structural parameters, the numerical investigation results showed that the maximum wavelength sensitivity of 6.0 μ m//RIU and 5.0 μ m//RIU for Au/ W O 3 and Ag/ W O 3 were obtained, with the coefficient of performance of 50.12 R I U - 1 and 134.84 R I U - 1 , respectively, for ultra-wide sensing ranges from 1.28 to 1.38. Also, the simulation outcomes revealed that the tungsten trioxide-coated with Ag or Au layers significantly enhanced the sensor. Finally, the numerical results of this study showed that the proposed sensor has substantial possibilities for large sensing RI applications such as biology and chemistry analytes, and it is also valid for other lower RI analyte sensing requirements as a consequence of its features such as high sensitivity, simple design, cost-effective design, and promising linear sensing performance. [ABSTRACT FROM AUTHOR]

We propose a dual-core, highly sensitive PCF SPR biosensor with C-shaped grooves based on a fusion of graphene and gold film. The performance of our sensor is enhanced by our circular fibre lattice with perforated air holes. We evaluate the biosensor's sensitivity to variations in refractive index (RI) in cancer cells numerically using the Finite Element Method (FEM) in COMSOL Multiphysics. After enhancing fiber parameters and using numerical results from amplitude method and spectral interrogation methods, we found that the biosensor demonstrates the highest sensitivity for MCF7 cells, 2142.86 nm/RIU under spectral interrogation. With HeLa cells, the biosensor shows a sensitivity of – 1058.039 1/RIU under the amplitude interrogation approach. Moreover, for MCF7, the biosensor reaches a resolution of 04.60 × 1E–5 RIU. [ABSTRACT FROM AUTHOR]

This article presents a highly sensitive plasmonic sensor with a focus on enhancing its capabilities through innovative design and simple geometric structure. A hexagonal-shaped photonic crystal fiber (PCF) based surface plasmon resonance sensor is designed and proposed for external sensing applications. The plasmonic material is made of gold and positioned on the outer side of the designed PCF. For detection purposes, the flow of the testing analyte is introduced on the exterior section of the PCF. The sensing capability of this innovative sensor is meticulously examined using the finite element technique facilitated by the COMSOL Multiphysics software. The suggested sensor, with a refractive index of 1.38, has a maximum amplitude sensitivity and wavelength sensitivity of 765.86 RIU−1 and 8,000 nm/RIU respectively. At the same refractive index, the sensing resolution of the sensor is 1.31 × 10–5 for amplitude sensitivity and 1.25 × 10–5 for wavelength sensitivity. Additionally, the sensing capability of the sensor lies in the range of the analyte refractive indices from 1.33 to 1.39. Furthermore, the sensing performance of the designed sensor is analyzed by optimizing the values of several design parameters including air-hole diameter, pitch, and gold layer thickness. The suggested sensor can recognize biological analytes with high sensitivity, improved sensing resolution, and appropriate linearity. [ABSTRACT FROM AUTHOR]

Given the physical constraints in electronic integrated circuit production, the adoption of photonic integrated circuits (PICs) is burgeoning. However, utilizing photonic crystals in PIC construction faces challenges in compressing and efficiently transmitting light in dimensions much smaller than the light wavelength, alongside the lack of direct interaction with conventional electronic integrated circuits. To address these challenges, plasmonic technology has been employed, leveraging the intrinsic interaction between photons and electrons and the phenomenon of extraordinary optical transmission (EOT) through nanohole arrays. This study investigates the significance of plasmonic structures in PIC realization by examining various structural parameters such as hole radius, layer thickness, substrate refractive index, and electric field distribution in EOT properties. Through an analysis of each parameter's effect on the proposed structure, an optimal structure is introduced, maximizing both absolute optical transmission efficiency and high-quality factor Q. Main calculations based on Rayleigh-Wood anomalies analysis, along with simulations using the finite-difference time-domain method, demonstrate the ability to predict and interpret the presence or absence of surface plasmon resonance peaks in the transmission spectrum independently of complex and time-consuming numerical simulations. This phenomenon holds important implications for the design of photonic integrated circuits, plasmonic sensors, and optoelectronic devices. [ABSTRACT FROM AUTHOR]

Photothermal therapy (PTT) is recognized as an effective tool for the treatment of cancer and it has attracted considerable attention of scientists. In this work, gold nanospheres (AuNSs) and gold nanorods (AuNRs) stabilized using poly(N‐vinylpyrrolidone) (PVP), pristine gellan gum (PGG), and poly(2‐ethyl‐2‐oxazoline)‐grafted gellan gum (GG‐g‐PEtOx) are synthesized and evaluated as PTT agents in Ehrlich cancer cells. The physicochemical characteristics of these AuNSs and AuNRs, including their surface plasmon resonance absorption spectra, size, zeta potential, and aspect ratio are studied using UV–vis‐spectroscopy, dynamic light scattering, zeta potential, transmission electron microscopy, and optical microscopy techniques. The polymer‐protected AuNSs exhibit light‐to‐heat conversion, raising the temperature from 37 to 43 °C when irradiated using a visible light source. In the case of AuNSs, considerable damage to Ehrlich cancer cells is observed following irradiation and 40 days of examination. However, with regard to AuNSs, the damage to Ehrlich cancer cells is slightly lower than observed in AuNRs. In vivo experiments demonstrate that laser irradiation of tumors in mice after injecting AuNSs leads to a statistically significant decrease in tumor size as compared to those not irradiated and the control samples. [ABSTRACT FROM AUTHOR]

The high affinity of the biotin–streptavidin interaction has made this non-covalent coupling an indispensable strategy for the immobilization and enrichment of biomolecular affinity reagents. However, the irreversible nature of the biotin–streptavidin bond renders surfaces functionalized using this strategy permanently modified and not amenable to regeneration strategies that could increase assay reusability and throughput. To increase the utility of biotinylated targets, we here introduce a method for reversibly immobilizing biotinylated thrombin-binding aptamers onto a Ni-nitrilotriacetic acid (Ni-NTA) sensor chip using 6xHis-tagged streptavidin as a regenerable capture ligand. This approach enabled the reproducible immobilization of aptamers and measurements of aptamer–protein interaction in a surface plasmon resonance assay. The immobilized aptamer surface was stable during five experiments over two days, despite the reversible attachment of 6xHis-streptavidin to the Ni-NTA surface. In addition, we demonstrate the reproducibility of this immobilization method and the affinity assays performed using it. Finally, we verify the specificity of the biotin tag–streptavidin interaction and assess the efficiency of a straightforward method to regenerate and reuse the surface. The method described here will allow researchers to leverage the versatility and stability of the biotin–streptavidin interaction while increasing throughput and improving assay efficiency. [ABSTRACT FROM AUTHOR]

Cu-PMMA nanocomposite films have been prepared via ex-situ chemical route by reduction of cupric chloride dissolved in aqueous CTAB solution with hydrazine and then incorporated the prepared Cu nanoparticles in a solution of Polymethylmethacrylate (PMMA) in chloroform and cast into thin films. Optical and structural characterizations of resulting nanocomposite films were performed using UV-visible spectroscopy and Transmission Electron Microscopy (TEM). Characteristic Surface Plasmon Resonance (SPR) peak of Cu nanoparticles was observed at about 2.14 eV (577 nm) in absorption spectra of Cu-PMMA nanocomposite films. From the observation of absorption spectra, the optical band gap and Urbach's energy values have been calculated. Band gap values of Cu-PMMA nanocomposite films were found to decrease from 3 eV to 2.4 eV, while Urbach's energy values increased with the increase in the concentration of Cu nanoparticles in PMMA. The decrease in the optical band gap and increase in Urbach's energy values indicated the modifications in the optical band structure of the PMMA matrix on the incorporation of Cu nanoparticles. TEM micrograph revealed spherical Cu nanoparticles embedded in PMMA with an average diameter of 6.5+ 2.5 nm. [ABSTRACT FROM AUTHOR]

Objective·To establish various in vitro screening systems for the discovery of peptide inhibitors targeting the interaction between small ubiquitin-like modifier (SUMO)-activating enzyme subunit 1 (SAE1) and subunit 2 (SAE2), as well as to evaluate their advantages, disadvantages, and applicability to this research. Methods·The DNA fragments encoding human SAE1 and SAE2 were cloned into vector pET-28a, respectively, to generate protein SAE1 and SAE2. Purified proteins were used to establish screening assays, including isothermal calorimetry (ITC), fluorescence polarization (FP), surface plasmon resonance (SPR) and a fluorescence assay based on the SAE enzyme activity. The inhibitory activity of peptide candidates in different screening systems was examined, and their performance in terms of sensitivity, robustness, throughput and cost was evaluated. Results·The dissociation constant (Kd) of in vitro SAE1 and SAE2 interaction was determined to be 0.96 μmol/L by ITC, and PEPT7 was identified as the most potent peptide. However, the tracer of FP, which was derived from PEPT7, was not up to snuff due to its low affinity with SAE2. In the SPR assay, the Kd value (=1.13 μmol/L) of SAE1 and SAE2 interaction was in line with the results from ITC. The SAE enzyme activity-based screening assay revealed that HP1B, the most effective peptide, inhibited SAE with an halfmaximal inhibitory concentration (IC50) of 15.72 μmol/L. The affinity of HP1B for SAE1 was determined to be 34.4 μmol/L by SPR. Conclusion·Several common screening systems for protein-protein interation (PPI) inhibitors are established and compared. Among them, ITC does not allow for high-throughput screening and it is difficult to accurately evaluate the low-affinity polypeptides with insignificant binding heat. The feasibility of FP relies heavily on the strong affinity between a tracer peptide and the protein target, making it unsuitable for the screening and optimization of low-affinity peptides. SPR is highly sensitive but the cost is high. The SAE enzyme activity-based assay stands out because it is a combination of high sensitivity, robustness, throughput and acceptable cost. [ABSTRACT FROM AUTHOR]

Monoclonal antibodies (MAbs) are powerful therapeutic tools in modern medicine and represent a rapidly expanding multibillion USD market. While bioprocesses are generally well understood and optimized for MAbs, online quality control remains challenging. Notably, N‐glycosylation is a critical quality attribute of MAbs as it affects binding to Fcγ receptors (FcγRs), impacting the efficacy and safety of MAbs. Traditional N‐glycosylation characterization methods are ill‐suited for online monitoring of a bioreactor; in contrast, surface plasmon resonance (SPR) represents a promising avenue, as SPR biosensors can record MAb–FcγR interactions in real‐time and without labeling. In this study, we produced five lots of differentially glycosylated Trastuzumab (TZM) and finely characterized their glycosylation profile by HILIC‐UPLC chromatography. We then compared the interaction kinetics of these MAb lots with four FcγRs including FcγRIIA and FcγRIIB at 5°C and 25°C. When interacting with FcγRIIA/B at low temperature, the differentially glycosylated MAb lots exhibited distinct kinetic behaviors, contrary to room‐temperature experiments. Galactosylated TZM (1) and core fucosylated TZM (2) could be discriminated and even quantified using an analytical technique based on the area under the curve of the signal recorded during the dissociation phase of a SPR sensorgram describing the interaction with FcγRIIA (1) or FcγRII2B (2). Because of the rapidity of the proposed method (<5 min per measurement) and the small sample concentration it requires (as low as 30 nM, exact concentration not required), it could be a valuable process analytical technology for MAb glycosylation monitoring. [ABSTRACT FROM AUTHOR]

Background: Huashi Baidu granule (HSBD), an approved herbal formula for treating COVID-19, demonstrates safety and efficacy. Despite its market approval, the detailed methodology and identification of its active components remain unexplored, leaving its bioactive constituents and action mechanisms unclear. Methods: This study investigated the potential mechanisms of HSBD’s active ingredient in treating COVID-19. Our approach integrated various techniques, including the UHPLC-QqQ-MS/MS method, analysis of the GEO database, network pharmacology, surface plasmon resonance, molecular docking and molecular dynamics simulations, to formulate a comprehensive research strategy. Results: The UHPLC-QqQ-MS/MS method employed for HSBD analysis proved stable, reliable, and reproducible. We identified 25 principal components in HSBD, with 7 compounds detected in plasma, namely Pogostone, P-Hydroxybenzoic acid, Paeoniflorin, Rhein, Emodin, Ephedrine hydrochloride, and Pseudoephedrine hydrochloride. Protein-Protein Interaction (PPI) network analysis identified MMP9 as a pivotal target. Surface plasmon resonance analysis revealed that Paeoniflorin and Rhein exert their antiviral effects by interacting with RBD and ACE2. In contrast, Emodin’s antiviral mechanism predominantly involves binding to MMP9. Molecular docking results indicated strong binding affinities of Rhein and Paeoniflorin to the hACE2 protein, and high binding affinities of Emodin to the MMP9 protein, all of which were corroborated by molecular dynamics simulations. Conclusion: We investigated the methodology and identified the active components of HSBD, focusing on those absorbed into the plasma, to elucidate the effective material basis of HSBD in the treatment of COVID-19, our research offered insightful exploration into its mechanisms of action against COVID-19.

Given the medical and social significance of Helicobacter pylori infection, timely and reliable diagnosis of the disease is required. The traditional invasive and non-invasive conventional diagnostic techniques have several limitations. Recently, opportunities for new diagnostic methods have appeared based on the recent advance in the study of H. pylori outer membrane proteins and their identified receptors. In the present study we assess the way in which outer membrane protein–cell receptor reactions are applicable in establishing a reliable diagnosis. Herein, as well as in other previous studies of ours, we explore the reliability of the binding reaction between the best characterized H. pylori adhesin BabA and its receptor, the blood antigen Leb. For the purpose we developed surface plasmon resonance (SPR) and double resonance long period grating (DR LPG) biosensors based on the BabA–Leb binding reaction for diagnosing H. pylori infection. In SPR detection, the sensitivity was estimated at 3000 CFU/mL—a much higher sensitivity than that of the RUT test. The DR LPG biosensor proved to be superior in terms of accuracy and sensitivity—concentrations as low as 102 CFU/mL were detected. [ABSTRACT FROM AUTHOR]

In this paper, we have proposed a new multilayer structure and investigated its performance as a chemical sensor utilizing surface plasmon resonance. Our proposed design consists of a black phosphorus layer sandwiched between a metal layer and a graphene layer, blue phosphorene/MoS2 heterostructure layers placed over it, and the sensing layer containing the analyte placed on top. A CaF2 prism in the Kretschmann configuration is employed to excite surface plasmon resonance (SPR), and the angle interrogation method is used for analysis. Sellmeier equations calculate the reflectivity and other parameters of the multilayer design. We also study the effect of the combination of BP and metal interlayer. Analysis of the proposed design shows significantly improved sensitivity compared to recent SPR-based sensors. In this paper, the sensitivity of 466°/RIU is obtained with silver metal, BP, graphene, and BlueP/MoS2 layers SPR sensor. [ABSTRACT FROM AUTHOR]

The confinement of electrons in gold nanoparticles results in Surface Plasmon Resonance (SPR), which is characterized by electric field enhancement in the vicinity of these nanoparticles. This property has been extensively studied and applied in various fields. In our research, we conduct a detailed investigation of plasmonic coupling in spherical gold nanoparticles. Specifically, we use the Discrete Dipole Approximation (DDA) method implemented in DDSCAT to simulate the coupling of electric fields in a doublet of nanoparticles as a function of the distance between them. Our simulations show that the coupling of SPR between two nanoparticles occurs up to a separation of 12 nm. Moreover, we extend our simulations to study the coupling of nanoparticles in linear chains consisting of up to five nanoparticles and in clustered forms. Our results indicate that the SPR coupling in a linear chain occurs, and as the number of nanoparticles increases, the field enhancement also increases. However, we observe that this effect saturates after four nanoparticles in a line. Our study provides insights into the plasmonic coupling in gold nanoparticles, which can aid in the design and optimization of plasmonic devices for various applications. [ABSTRACT FROM AUTHOR]

Heart failure (HF) is a clinical entity included in cardiovascular diseases affecting millions of people worldwide, being a leading cause of hospitalization of older adults, and therefore imposing a substantial economic burden on healthcare systems. HF is characterized by dyspnea, fatigue, and edema associated with elevated blood levels of natriuretic peptides, such as N Terminal pro-B-type Natriuretic Peptide (NT-proBNP), for which there is a high demand for point of care testing (POCT) devices. Optical fiber (OF) biosensors offer a promising solution, capable of real-time detection, quantification, and monitoring of NT-proBNP concentrations in serum, saliva, or urine. In this study, immunosensors based on plasmonic uncladded OF tips were developed using OF with different core diameters (200 and 600 µm). The tips were characterized to bulk refractive index (RI), anddetection tests were conducted with NT-proBNP concentrations varying from 0.01 to 100 ng/mL. The 200 µm sensors showed an average total variation of 3.6 ± 2.5 mRIU, an average sensitivity of 50.5 mRIU/ng·mL−1, and a limit of detection (LOD) of 0.15 ng/mL, while the 600 µm sensors had a response of 6.1 ± 4.2 mRIU, a sensitivity of 102.8 mRIU/ng·mL−1, and an LOD of 0.11 ng/mL. Control tests were performed using interferents such as uric acid, glucose, and creatinine. The results show the potential of these sensors for their use in biological fluids. [ABSTRACT FROM AUTHOR]

In this study, two regular single-mode fibers [SMF] and two regular multimode fibers [MMF] are combined with a photonic crystal fiber [PCF] [SMF-PCF-SMF] and a photonic crystal fiber MMF-PCF-MMF, respectively, to create a surface plasmon resonance (SPR) based on a Mach–Zehnder interferometer MZI for measuring the refractive index RI for the ion toxic metal nickel using a sensing tapered PCF. The PCF side can be tapered to create the SPR curve, which is then obtained by coating a gold (Au) film over the tapered region. Results of the studies show a clear SPR effect for the suggested sensor, and it was estimated and calculated signal-to-noise ratio (SNR), resolution (R), figures of merit (FOM), and sensitivity (S) are advancing; the SNR 0.18, S is 11.11 μm/RIU, resolution 1.7 × 10−4, and the FOM 22.87 for single-mode fiber–photonic crystal fiber–single-mode fiber [SMF-PCF-SMF], while performance metrics for multimode fiber–photonic crystal fiber–multimode fiber [MMF-PCF-MMF]; for example, the (S) is nearing 10 μm/RIU, FOM is 90.9, resolution is 1 × 10−4, and SNR is 0.209 are achieved. [ABSTRACT FROM AUTHOR]

A dual-channel surface plasmon resonance (SPR) sensor, based upon a multimode-single mode-multimode-single mode- multimode (MSMSM) fiber structure, is reported for the simultaneous measurement of temperature and refractive index. One channel is coated with an indium tin oxide-silver layer for refractive index sensing, and the channel is coated with Au and cyclohexane layer for temperature sensing. The experiments show that the sensor provides high sensitivity with values of 3379 nm/RIU across the refractive index range from 1.333 to 1.3699 and −3.163 nm/°C from 40 °C to 90 °C. The cross-sensitivity problem is resolved by the dual-wavelength matrix method. Moreover, the proposed sensor has good stability, low cost, and a compact structure and may be employed in biology, chemistry, and environmental testing. [ABSTRACT FROM AUTHOR]

Toll-like receptor 4 (TLR4) is a crucial inflammatory signaling pathway that can serve as a potential treatment target for various disorders. A number of inhibitors have been developed for the TLR4 pathway, and although no inhibitors have been approved for clinical use, most have been screened against the TLR4-MD2 conformation. The venom gland is the organ of venomous snakes that secretes substances that are toxic to other animals. The level of gene transcription in venom glands is different from that in other tissues, includes a large number of biologically active ingredients, and is an important natural resource for the development of new drugs. We constructed a T7 phage display library using the cobra (Naja atra) venom gland from the Guangdong Snake Breeding Plant and performed three rounds of screening with TLR4 as the target, randomly selecting monoclonal phage spots for PCR followed by Sanger sequencing. The obtained sequences were subjected to length analysis, molecular docking, solubility prediction, and stability prediction, and a peptide containing 39 amino acids (NA39) was finally screened out. The BLAST results indicated that NA39 was a sequence in RPL19 (Ribosomal Protein L19). After peptide synthesis, the binding ability of NA39 to TLR4 was verified by the surface plasmon resonance (SPR) technique. In this study, a new peptide that can specifically bind TLR4 was successfully screened from the cobra venom gland cDNA library, further demonstrating the effectiveness of phage display technology in the field of drug discovery. [ABSTRACT FROM AUTHOR]

A proposed surface plasmon resonance (SPR) sensor inclusion of black phosphorus (BP) nanomaterial is presented in this paper. The performance of the sensor is compared with sensors based on graphene, MoS2, MoSe2, WS2, and WSe2. The optimal thickness of the Cu-Ni layer with BP is determined using the angular interrogation method, resulting in the highest sensitivity of 525°/RIU at a wavelength of 633 nm. The results indicate that the proposed sensor outperforms other 2D nanomaterial-based sensors in terms of sensitivity. Furthermore, the sensor is used for detecting glucose levels in urine samples. By optimizing the thickness of the Cu layer, a maximum sensitivity of 430.10°/RIU is achieved for glucose level detection. It is observed that the proposed configuration with other 2D nanomaterials enhances the sensitivity at a lower thickness of Ni. [ABSTRACT FROM AUTHOR]

We put forward and numerically analyze a D-shaped surface plasmon resonance fiber sensor with high figure of merit (FOM), within the detection range of 1.33–1.41. The sensing area is coated with platinum (Pt) grating, aluminum oxide (Al2O3) nanofilm, and graphene film. Plasmonic resonance of Pt grating can be excited by the core mode of the D-shaped fiber, so as to detect the change of refractive index (RI). The addition of graphene and Al2O3 layers is to enhance the nearfield electric intensity of the Pt grating, thus improving the sensing performance. Especially, the FOM of the designed sensor can be consumedly improved by the Al2O3/graphene/Pt grating hybrid nanostructure, up to 432 RIU−1, with a high RI sensitivity of 11,252 nm/RIU in near-infrared region. The influence of the three nanolayers on the sensing performance is carefully calculated and analyzed. The designed sensor would be a candidate for biological applications, environmental monitoring, and medical diagnostics. [ABSTRACT FROM AUTHOR]

This paper presents the surface plasmon resonance (SPR) characteristics of D-shaped silica multimode optical fiber coated with bilayer silver-gold film. The effect of various coating thicknesses on the SPR characteristics was investigated through simulation using COMSOL Multiphysics. The inner layer Ag thickness varied from 20 nm to 60 nm, and the outer layer Au thickness ranged from 5 nm to 25 nm. Prior simulation results indicated that a single-layer silver (Ag) coating produces a narrower plasmonic curve than a single-layer gold (Au) coating. The confinement loss and the resonance wavelengths were simulated for the sensing medium with a refractive index (RI) range of 1.40–1.45. The simulation results show that the Ag/Au bilayers coated sensors have better full-width-half-maximum (FWHM) and figure-of-merit (FOM) than the single-layer coated sensors. The Ag/Au with a 40 nm/5 nm thickness exhibits the highest confinement loss, with a wavelength sensitivity of 10 000 nm/RIU and a figure-of-merit (FOM) of 500 RIU−1. The proposed sensor using a D-shaped optical fiber coated with Ag/Au layers has a high potential for remote sensing applications involving chemical liquids, offering robust and accurate measurements within the tested refractive index range.

An optical fiber scale sensor based on the detection principle of surface plasmon resonance (SPR) was developed for the rapid, high-sensitivity, real-time evaluation of scale precipitation in geothermal fluids. The optical fiber SPR scale sensor was fabricated by depositing a gold thin film onto the surface of an optical fiber with an exposed core. The optimal gold film thickness of the sensor was determined to be 30 nm, which achieved a refractive index sensitivity of 2140 nm per refractive index unit. A field test was conducted using geothermal brine from the Obama Binary Geothermal Power Plant in Unzen, Nagasaki Prefecture. A conventional optical fiber scale sensor and the SPR sensor were simultaneously assessed using raw and pH-adjusted brines. For the SPR sensor, a peak shift of 0.27 nm/min was observed at a response time of 1 min, whereas no change in transmittance was observed for the conventional sensor until 180 min. After the experiments, a scanning electron microscopy-energy-dispersive spectroscopy analysis was conducted on the sensors, and the findings showed that the deposition of Mg-SiO2 scale did not significantly differ between the two sensors. The developed SPR sensor achieved faster scale precipitation detection (tens of minutes to hours) than the conventional sensor.

This paper presents a photonic crystal fiber (PCF) sensor that can be used to measure the temperature and magnetic field simultaneously, and to monitor the changes in them in the environment. When we designed the fiber structure, two circular channels of the same size were added to the fiber to facilitate the subsequent addition of materials. A gold film is added to the upper channel (ch1), and the channel is filled with a magnetic fluid (MF). The sensor can reflect changes in the temperature and magnetic field strength. The two channels containing MF and PDMS in the proposed fiber are called ch1 and ch2. The structure, mode and properties (temperature and magnetic field) were analyzed and discussed using the finite element method. By using the control variable method, the influence of Ta2O5 or no Ta2O5, the Ta2O5 thickness, the diameter of the special air hole, the distance from the fiber core and the distance between them in the displacement of the loss spectrum and the phase-matching condition of the coupling mode were studied. The resulting maximum temperature sensitivity is 6.3 nm/°C (SPR peak 5), and the maximum magnetic field sensitivity is 40 nm/Oe (SPR peak 4). Because the sensor can respond to temperature and magnetic field changes in the environment, it can play an important role in special environmental monitoring, industrial production and other fields.

2-Furaldehyde (2-FAL) is one of the main by-products of the degradation of hemicellulose, which is the solid material of the oil–paper insulating system of oil-filled transformers. For this reason, it has been suggested as a marker of the degradation of the insulating system; sensing devices for 2-FAL analysis in a wide concentration range are of high interest in these systems. An optical sensor system is proposed; this consists of a chemical chip, able to capture 2-FAL from the insulating oil, coupled with a surface plasmon resonance (SPR) probe, both realized on multimode plastic optical fibers (POFs). The SPR platform exploits gold nanofilm or, alternatively, a double layer of gold and silicon oxide to modulate the sensor sensitivity. The capturing chip is always based on the same molecularly imprinted polymer (MIP) as a receptor specific for 2-FAL. The system with the SPR probe based on a gold nanolayer had a higher sensitivity and a lower detection limit of fractions of μg L−1. Instead, the SPR probe, based on a double layer (gold and silicon oxide), has a lower sensitivity with a worse detection limit, and it is suitable for the detection of 2-FAL at concentrations of 0.01–1 mg L−1.

A unique no-stirring synthesis has been developed to obtain highly monodisperse hollow silver nanoshells (HAgNSs) with plasmons in the second near-IR (NIR-II) window. The method also introduces dimethylglyoxime (DMG) as a quadrupole-supporting agent. The quadrupole surface plasmon resonance (Q-SPR) was found to be highly intense and tunable from 450 to 558 nm. Two types of dipolar resonances, symmetric dipole surface plasmon resonance (SD-SPR) and antisymmetric dipole surface plasmon resonance (AD-SPR), are also observed. The AD-SPR peaks remain constant at 333 nm while the SD-SPR peaks are tuned gradually from 780 to 850 → 920 → 1000 → 1150 nm. They were accordingly named HAgNS-780, HAgNS-850, HAgNS-920, HAgNS-1000, and HAgNS-1150, and their outer diameters were found to be 53 ± 4, 49 ± 3, 54 ± 3, 62 ± 5, and 39 ± 3 nm, respectively. The corresponding aspect ratios (outer diameter/shell thickness) were 3.31, 3.37, 3.48, 4.13, and 5.2, respectively. A correlation between the tunability of SD-SPR, AD-SPR, and Q-SPR and aspect ratio has been established. The shape and size parameters were utilized for the simulation of the extinction spectra by the discrete dipole approximation (DDA) method. Second derivative FTIR analysis reveals the peculiar binding mode of DMG to the HAgNS which is the genesis of Q-SPR in such smaller-sized nanoshells. The further red shift of Q-SPR and SD-SPR was observed with the addition of folic acid (FA). It also imparts greater aqueous solubility, colloidal stability, and biocompatibility, making them suitable for biomedical applications. [ABSTRACT FROM AUTHOR]

Programmed death ligand-1 (PD-L1) is highly expressed in a variety of cancer cells and suggests a poorer prognosis for patients. The natural compound isorhamnetin (ISO) shows promise in treating cancers and causing damage to canine mammary tumor (CMT) cells. We investigated the mechanism of ISO in reducing PD-L1 expression in CMT cells. Clustered, regularly interspaced short palindromic repeat-associated protein 9 (CRISPR/Cas9) was used to mediate CD274 knockout in U27 cells. Then, monoclonal cells were screened and cultured. Nucleotide sequencing and expression of PD-L1 were detected. Additionally, we examined cell migration, invasion, and damage. Immunofluorescent staining of PD-L1 was examined in U27 cells. The signaling pathways were measured by Western blotting. Murine xenotransplantation models and murine immunocompetent allograft mammary tumor models were established to evaluate the effect of ISO therapy. Expression of Ki-67, caspase3, and PD-L1 were analyzed by immunohistochemistry. A pull-down assay was used to explore which proteins could bind to ISO. Canine EGFR protein was purified and used to detect whether it directly binds to ISO using a surface plasmon resonance assay. ISO inhibited the EGFR-STAT3-PD-L1 signaling pathway and blocked cancer growth, significantly increasing the survival rate of healthy cells. The cell membrane receptor EGFR was identified as a direct target of ISO. ISO could be exploited as an antineoplastic treatment of CMT by targeting EGFR to suppress PD-L1 expression. [ABSTRACT FROM AUTHOR]

Fluidic and non-fluidic surface plasmon resonance measurements were realized for the same type of sensory layer and using the same mouse IgG antibody and anti-mouse IgG antibody biomolecular system. A comparison of the thicknesses of the anti-mouse IgG antibody layers bound to the ligand at increasing analyte concentrations ranging from 0.0 μg mL−1 to 5.0 μg mL−1 in the non-fluidic and the fluidic variant showed that the thickness of the bound anti-mouse antibody layers in the fluidic variant was approximately 1.5–3 times larger than in the non-fluidic variant. The greater thicknesses of the deposited layers were also reflected in the larger increment of the resonant angle in the fluidic variant compared to the non-fluidic variant in the considered range of analyte concentrations. The choice between fluidic and non-fluidic surface plasmon resonance biosensors may be justified by the availability of analyte volume and the intended modulation technique. When working with limited analyte, non-fluidic biosensors with intensity modulation are more advantageous. For larger analyte quantities, fluidic biosensors with angular modulation are recommended, primarily due to their slightly higher sensitivity in this measurement mode. [ABSTRACT FROM AUTHOR]

Ongoing research on the sensitivity and integration of refractive index‐based biosensors has resulted in significant advancements. Here, the study presents an enhanced surface plasmon resonance biosensor that integrates imaging technology and features dual‐parameter interrogation (intensity and phase) with guided mode coupling. By depositing a silica‐waveguide‐layer on a metal‐layer, two‐mode coupling is established to generate a high Q resonance and induce a phase mutation. The sensing performance experiment demonstrated a phase sensing sensitivity of 1.1 × 105 degree RIU−1, Q‐value of the resonant peak up to 314, and figure of merit of 300 RIU−1, superior to most standard plasmonic sensors. An in‐line phase‐polarization modulation scheme combined with imaging technology is proposed to extract the resonant phase carrying refractive index information. Additionally, a pair‐prism module is designed to optimize the sensing system configuration. Meanwhile, dual‐parameters interrogation including the intensity and phase are demonstrated, which offers potential for complementary and multi‐sensing fusion applications. The intensity interrogation also shows a considerable sensitivity of 7.2 × 104 a.u. RIU−1. Furthermore, it is combined with microfluidic chip to detect of alpha‐synuclein protein closely related to Parkinson's disease, and the limit of detection can reach 300 pg mL−1 level, which indicated a considerable potential for high‐throughput diagnosis application. [ABSTRACT FROM AUTHOR]

Optical fiber biosensors can be used to develop point-of-care tests (POCTs) for detecting viruses and bacteria in several matrices. In particular, the surface plasmon resonance (SPR) and localized SPR phenomena (LSPR) can be excited by exploiting low-cost and small-size optical fiber chips. Generally, SPR or LSPR sensors are realized using several kinds of modified optical fibers (silica, plastic, or specialty) or by exploiting other optical waveguides (e.g., slab, spoon-shaped waveguides, etc.). More specifically, optical fiber sensors can be classified as intrinsic or extrinsic. In the "optical fiber intrinsic sensors", the sensing area is realized in the optical fiber directly, such as in the case of plasmonic platforms based on D-shaped plastic optical fibers (POFs), tapered optical fibers, U-bend POFs, or light-diffusing fibers (LDFs). By contrast, when an optical fiber is used as a mere waveguide allowing for the launch of light to the sensing region and its collection, it is defined as an extrinsic optical fiber sensor, like in the case of the plasmonic sensors realized by Cennamo et al. using POFs combined with spoon-shaped waveguides, 3D-printed platforms, bacterial cellulose waveguides, nanogratings, and InkJet-printed chips. To realize optical biosensor chips for the detection of viruses and bacteria, both intrinsic and extrinsic plasmonic POF sensors can be efficiently combined with receptors specific for membrane proteins, either biological (e.g., antibodies, aptamers, enzymes, etc.) or synthetic (e.g., molecularly imprinted polymers), to build groundbreaking POCTs. [ABSTRACT FROM AUTHOR]