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The article introducing an innovative exposed core SPR biosensor employing an asymmetrical elliptic air hole PCF known for remarkable sensitivity. Gold-plated fiber sensor detects changes in refractive index. This sensor effectively covers a RI scale of 1.28 to 1.42 for analytes, showcasing its versatility in simultaneous detection. Taking into account the RI change at the outer surface, attractive sensing implementations such as optimal wavelength sensitivity of 97,000 nm/RIU and optimal amplitude sensitivity of 529.20 RIU−1 are attained. Furthermore, with a resolution of 9.09 × 10−6 RIU, a figure in merit of 170 RIU−1, an FWHM of 570 nm, and a detection accuracy of 0.0166 nm−1, the suggested sensor is impressive. This suggested sensor finds application in monitoring sucrose solutions across a spectrum ranging from 0% to 45% chemical concentration over time. It has an ideal amplitude sensitivity of 530.95 RIU−1 and an ideal wavelength sensitivity of 10,000 nm/RIU for sucrose solutions at the 40% concentration level. Furthermore, the sensor shows an ideal wavelength sensitivity of 35,000 nm/RIU and an ideal amplitude sensitivity of 793.80 RIU−1 for the detection of 2-propanol. Nevertheless, beyond sucrose noticing auspicious sensing qualities by the suggested sensor its feasibility for impact fully identifying a range of biochemical and organic samples. As a result, the proposed sensor holds promise as an exemplary choice the realms in biomedical sensing, the detection of lower RI analyses as well as chemical analysis. Streamlining practical application, the sensor's structure incorporates eight elliptical air holes, uncomplicated readily manufactural with existing technologies.

A deep gold-coated sinusoidal grating is proposed as a transducer for label-free real-time biosensing, operating in a new configuration based on the optical switch effect, which produces complementary optical outputs enabling differential and referenced detection. Biosensing experiments are reported for the first time on this platform, using immunoassays involving biospecific pairs consisting of bovine serum albumin and its antibody, and human serum albumin and its antibody. Direct and sandwich immunoassays are demonstrated along with negative controls. A limit of detection of 6 pg/mm2 was obtained. A theoretical model correlating the variation in the differential referenced output optical signal with adlayer growth is presented and supports the experimental results. The proposed detection device operating in the optical switch configuration makes a promising case for point-of-care detection applications because the differential detection of two diffracted orders enables common noise suppression and robust interrogation.

Extracellular histone proteins in the blood indicate a heightened risk of morbidity after trauma or in major illnesses such as sepsis. We present the development of an aptasensor for histone detection with an extended gate field-effect transistor (EGFET) configuration, which benefits from low power consumption, rapid response, and compatibility with miniaturized gold electrodes. Histones have a high isoelectric point and charge density, which cause them to physically adsorb to non-specific elements of the sensor that have available electrostatic charges. To combat this, the sensing surface is formed with a thiol-modified, high-affinity and histone-specific RNA aptamer sequence and by co-immobilizing with poly(ethylene glycol) methyl ether thiol (PEG) as a blocking agent. Surface plasmon resonance (SPR) is used to analyze aptamer and PEG immobilization strategies, confirm histone binding, and calculate kinetic binding constants. Through comparison of different blocking agents and time-dependent preparation, the ideal equilibrium dissociation constant (KD) is estimated to be below 200 pM, which is the upper range of extracellular histone concentrations in critically ill patients with high mortality. The EGFET sensitivity of the optimized aptasensor is 6.65 mV/decade concentration change for histone H4 with a physiologically relevant 5 pM limit of detection. Selectivity tests with 100 nM bovine serum albumin (BSA) demonstrate a signal response that is 13-fold smaller than for histones. This EGFET aptasensor platform is suitable for future point-of-care monitoring of histone levels in critically ill patients, thus permitting the early detection of increased risk and the need for more aggressive interventional measures to prevent mortality.

The presence of nitrite, a prevalent contaminant in natural environments, presents a significant environmental and human health concern. Hence, it is imperative to develop a sensor with the ability to quantitatively detect nitrite. This study focuses on the design and development of i) probe 1: tilted fiber Bragg gratings (TFBGs) and ii) probe 2: fiber optic tip-based plasmonic sensors utilizing ion-imprinted polymers. The concentration of nitrite was assessed at various levels using both sensing configurations. The outcomes indicated that the TFBGs-based sensor exhibited a sensitivity and limit of detection (LOD) of 0.469 nm/ln(μg/mL) and 0.142 μg/mL in the linear detection range of 0.5–50 μg/mL. The fiber optic tip-based sensor exhibited a sensitivity and LOD of 1.16 nm/ln(μg/mL) and 0.176 μg/mL within the 1–50 μg/mL linear detection range. The obtained sensing results reveal that the sensors presented in this study are able to accurately detect nitrite at various concentrations in a quantitative manner. Moreover, an assessment was conducted to examine the selectivity and reusability of the sensor individually, yielding satisfactory results.

Hydrogen peroxide (H2O2) sensing has been widely investigated using various electrochemical methods, yet the challenge of finding an imaging technique capable of real-time, spatially resolved detection remains. Addressing this, we introduce a Prussian blue (PB) nanofilm-sensitized plasmonic electrochemical microscopy (PEM) technique that successfully visualizes the localized delivery of H2O2. The PB nanofilm was carefully characterized, and its sensing capability towards H2O2 was demonstrated in amperometric mode. Employing a precise micromanipulator system, we controlled a micropipette to create a localized concentration gradient on the sensor surface and monitored the gradient through the PB nanofilm-sensitized PEM. The accuracy of the obtained concentration values was further validated by numerical simulations based on finite-element methods. Our technique ensures dependable localized detection, and we anticipate that advancements in film uniformity will further improve the resolution. The potential applications of this technique are broad and significant, including the opportunity to investigate single-cell exocytosis with neurotransmitters like dopamine, thus offering a promising avenue for future biomedical research.

The signal enhancement in plasmon-enhanced spectroscopy is primarily contributed by hotspots generated through the surface plasmon resonance effect. Precise control of hotspot positions within nanostructures is of great significance in surface-enhanced Raman spectroscopy (SERS) and high spatial resolution imaging. However, predicting the positions of hotspots is challenging due to the small nanogaps and complex plasmonic interactions. In this study, we theoretically investigate the localized surface plasmonic properties of split ring nanostructure. The effects of variations in the inner radius, gap distance and thickness of the split ring on the hotspot distribution at the nanogaps are systematically analyzed using a three-dimensional finite element method. The results demonstrate that precise control over the positions and quantities of hotspots can be achieved by choosing the excitation wavelength and the gap size of the split rings. The calculated maximum Raman enhancement obtained at the hotspots can reach nine orders of magnitude. Our findings not only contribute to a deeper understanding of the SERS enhancement mechanism, but also provide theoretical insights for further development of surface-enhanced fluorescence, plasmonic sensors, and super-resolution imaging in the field of interface spectroscopy.

Summary: Mincle (macrophage-inducible C-type lectin, CLEC4E) is a C-type lectin immune-stimulatory receptor that can be targeted for inducing potent adjuvant effects. Mincle can recognize trehalose dimycolate and related glycolipids. Here, we present a protocol to identify the ligand binding mode of Mincle. We describe steps for preparing labeled Mincle ectodomain, data acquisition, and analysis of nuclear magnetic resonance experiments using non-detergent sulfobetaine-195. This protocol can be applied to other protein-ligand interactions that have aggregation problems for complex formation.For complete details on the use and execution of this protocol, please refer to Furukawa et al.1 : Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.

In recent years, researchers have made significant contributions to the field of Surface Plasmon Resonance sensors and their potential applications. SPR features include real-time monitoring of biomolecular interactions, label-free detection, high sensitivity, and the ability to analyze multiple samples at the same time. These characteristics make SPR biosensors a valuable tool in the pharmaceutical industry for ensuring drug efficacy and safety. Furthermore, SPR sensors have a reputation for providing quantitative and qualitative superior performance in real-time applications such as drug development, environmental monitoring, food safety, medical diagnostics, clinical diagnosis, biological investigations, and biomolecule interactions. This review will go over recent advances in SPR biosensors and how they can be used in drug discovery and development. We will also look at the challenges and opportunities of using SPR biosensors in the pharmaceutical industry.

Olfactory receptors (ORs), the largest family of G protein-coupled receptors (GPCRs), are ectopically expressed in cancer cells and are involved in cellular physiological processes, but their function as anticancer targets is still potential. OR2AT4 is expressed in leukemia cells, influencing the proliferation and apoptosis, yet the limited number of known OR2AT4 agonists makes it challenging to fully generalize the receptor's function. In this study, we aimed to identify new ligands for OR2AT4 and to investigate their functions and mechanisms in K562 leukemia cells. After producing the recombinant OR2AT4 protein, immobilizing it on a surface plasmon resonance chip, and conducting screening to confirm binding activity using 258 chemicals, five novel OR2AT4 ligands were discovered. As a result of examining changes in intracellular calcium by five ligands in OR2AT4-expressing cells and K562 cells, (−)-epigallocatechin gallate (EGCG) was identified as an OR2AT4 agonist in both cells. EGCG reduced the viability of K562 cells and induced apoptosis in K562 cells. EGCG increased the expression of cleaved caspase 3/8 and had no effect on the expression of Bax and Bcl-2, indicating that it induced apoptosis through the extrinsic pathway. Additionally, the initiation of the extrinsic apoptosis pathway in EGCG-induced K562 cells was due to the activation of OR2AT4, using an OR2AT4 antagonist. This study highlights the potential of EGCG as an anti-cancer agent against leukemia and OR2AT4 as a target, making it a new anti-cancer drug.

The combination of gold nanoparticles (Au NPs) incorporated ZnO/rGO heterostructures is unique for sunlight-driven photocatalysis (SPC). Here, hydrothermally synthesized pristine ZnO nanostructures (NSs), ZnO/rGO binary nanocomposites (BNCs) and ZnO/rGO/Au ternary nanocomposites (TNCs) of bandgap (Eg) values 3.56 eV, 3.37 eV and 3.17 eV, respectively are reported. These NSs are analyzed optically, structurally and morphologically via UV–Vis absorption spectroscopy, X-ray diffraction and SEM techniques, respectively. The SPC of methylene blue (MB) organic dye was considered using all three samples. The slow charge transfer over grain boundaries of ZnO results in the prohibition of photogenerated electron-hole pairs, exhibiting low photodegradation efficiency (87%). However, in BNCs the creation of alternative pathway of the carriers due to low work function level of rGO as compared to ZnO enhances the charge separation with an increased photocatalytic efficiency (92%). In contrast, TNCs show rather fast photodegradation efficiency (96%) as the photoexcited electrons on Au NPs surface migrate to the CB of ZnO because of the SPR stimulation of Au. These electrons easily shift to the conductive rGO layers and react with oxygen species (O2) producing superoxide radicals (•O2–). Thus, TNCs sample has appeared to be auspicious candidate for the photodegradation of organic pollutants in untreated water.

The main shortcoming of the Surface Plasmon Resonance (SPR) method is its inability to detect low molecular weight (

The technology of surface plasmon resonance (SPR) is widely recognized and valued for its ability to rapidly and sensitively investigate biomolecular interactivities in real-time. Herein, we numerically investigate the collective influence of metal/ transition metal dichalcogenide (TMDC)/halide perovskite (HP)/2D carbon (C) and phosphorus (P) allotropes on the functionality of an SPR biosensor deploying Kretschmann configuration. The incident light wavelength is held constant at 633 nm, and radiative properties of the hybrid structure are determined using the attenuated total reflection and transfer matrix techniques. Crucial performance metrics such as quality factor (QF), figure of merit (FoM), sensitivity, and detection accuracy are calculated. The comparison is conducted and evaluated against the current literature using performance outcomes in terms of several prisms such as BK7, BAK1, BAF10, SF5, SF10, SF11, 2S2G, CaF2, and CsF, several TMDCs such as WS2, MoS2, WSe2, MoSe2, and PtSe2, several HPs such as CsPbI3, KSnI3, CsSnI3, and FASnI3, and 2D C/P allotropes such as Graphene, MXene, Black phosphorene (BP), and Blue phosphorene (BlueP) in order to search optimum parameters, and then we implement the best one in each layer of this biosensor design. It is noticed that the SPR heterostructure based on BAK1 prism, plasmonic metal Ag, tungsten disulfide (WS2) TMDC, formamidinium tin iodide (FASnI3) HP and 2D BP exhibits outstanding performance with regard to sensor performance characteristics. The observed FoM and sensitivity are 48.2/RIU and 402°/RIU, respectively. The investigation of the electric field distribution within this biosensor along the normal to the interface is also conducted using the finite difference time domain (FDTD) approach to demonstrate the unique contribution of FASnI3. The findings presented in this study are anticipated to play a key role in the improvement of plasmonic resonance-based biosensing domains like DNA hybridization or formalin detection by employing halide perovskite as an additional layer in SPR biosensors.

Water-soluble organic molecules (WSOMs) in inhaled PM2.5 can readily translocate from the lungs into the blood circulation, facilitating their distribution to and health effects on distant organs and tissues in the human body. Human serum albumin (HSA), the most abundant protein carrier in the blood, readily binds exogenous substances to form non-covalent adducts and subsequently transports them throughout the circulatory system, thereby indicating their internal exposure. The direct internal exposure of WSOMs in PM2.5 needs to be understood. In this study, the non-covalent HSA-WSOM adductome was developed as a dosimeter to evaluate the internal exposure potential of WSOMs in urban PM2.5. The WSOM composition was acquired from non-target high-resolution mass spectrometry analysis coupled with multiple ionizations. The binding level of HSA-WSOM non-covalent adducts was obtained from surface plasma resonance. Machine learning combined WSOM composition and the binding level of HSA-WSOM non-covalent adducts to screen bindable (also internalizable) WSOMs. The concentration of WSOM ranged from 4 to 13 μg/m3 during our observation period. Of the 17,513 mass spectral features detected, 9,484 contributed to the non-covalent adductome and possessed the internal exposure potential. 102 major contributors accounted for 90.6 % of the HSA-WSOM binding level. The fraction of internalizable WSOMs in PM2.5 varied from 11.9 % to 61.3 %, averaging 26.2 %. WSOMs that have internal exposure potential were primarily lignin-like and lipid-like substances. The HSA-WSOMs non-covalent adductome represents direct internal exposure potential, which can provide crucial insights into the molecular diagnosis of PM2.5 exposure and precise assessments of PM2.5 health effects.

This study introduces a dual-core photonic crystal fiber incorporating a highly responsive plasmonic refractive index (RI) sensor. The performance of the RI sensor is evaluated based on amplitude sensitivity, wavelength resolution, wavelength sensitivity, and the linearity of the resonance wavelength. Employing the finite element technique (FEM), a numerical analysis of the proposed design is conducted. Results indicate that employing the amplitude interrogation method yields a peak amplitude sensitivity of 605.82 RIU−1 for y-polarization. Furthermore, the wavelength interrogation approach for y-polarized modes demonstrates a maximum wavelength sensitivity of approximately 17,000 nm/RIU and a maximum wavelength resolution of 5.88 × 10−6 RIU. The proposed sensor exhibits a figure of merit of approximately 298 and effectively responds to refractive index variations within the range of 1.28 to 1.40. These promising outcomes, coupled with the broad sensing range, establish the suggested sensor as a promising candidate for the detection of organic chemical solutions.

In this article, Photonic crystal fiber (PCF) based surface plasmon resonance (SPR) sensor is proposed for detecting cancerous cells like Hela for cervical cancer and Basal for skin cancer. The numerical analysis and simulation of the designed biosensor is carried out using the finite element method in conjunction with a layer that is perfectly matched. The PCF sensor based on SPR has a gold layer for the plasmonic effect and a nanolayer of TiO2 to form an adhesion layer in between the gold and silica. The sensor can detect an analyte's refractive index (RI) between 1.360 and 1.392 for two distinct cancerous cell types (Hela and Basal). The proposed biosensor's performance is evaluated using amplitude and wavelength investigation techniques. This study achieves the wavelength sensitivity of 6250 nm/RIU, 5000 nm/RIU, and the amplitude sensitivity of 909.05 RIU−1, 505.53 RIU−1 for Hela and Basal cells, respectively. The results show that the proposed sensor is suitable for real-time biosensing applications.

We report interaction of 1,5-Bis (3-morpholinopropionamido) anthracene-9,10-dione with Human Telomeric G4 DNA sequences, wHTel26 and HTel22 in presence of K+ and Na+ ions, respectively. Surface Plasmon Resonance yields association constant Kb = 1.0–3.8x105 M−1 with HTel22 in K+-rich solution. Significant hypochromism (46–79 %) and fluorescence quenching (83–92 %), no change in absorption and emission maxima, unaltered fluorescence lifetime of ligand, change in conformation of G4 DNA with no overall disruption of G-quartets and absence of induced Circular Dichroism band, suggest external groove binding of ligand. Molecular docking shows short contacts of 9O, 15N, 18O, 11NH, 12CO atoms of ligand with A3, G4, G22, G23 and A1, G3, G14 bases of 3 + 1 hybrid-2 and 2 + 2 anti-parallel conformers, respectively without making any contact with loops, to an energetically more favourable conformation. Ligand-influenced thermal stabilization, up to ΔTm = 37/48 °C, may disrupt access of telomerase enzyme to telomere and promote apoptosis in malignant tissues.

Uric acid is a waste product of the human body where high levels of it or hyperuricemia can lead to gout, kidney disease and other health issues. In this paper, Finite Difference Time Doman (FDTD) simulation method was used to develop a plasmonic optical sensor to detect uric acid with molarity ranging from 0 to 3.0 mM. A hybrid layer of gold-zinc oxide (Au–ZnO) was used in this Kretschmann-based Surface Plasmon Resonance (K-SPR) technique with angular interrogation at 670 nm and 785 nm visible optical wavelengths. The purpose of this study is to observe the ability of the hybrid material as a sensing performance enhancer for differentiating between healthy and unhealthy uric acid levels based on the refractive index values from previous study. Upon exposure to 670 nm wavelength, the average sensitivity of this sensor was found to be 0.028°/mM with a linearity of 98.67 % and Q-factor value of 0.0053 mM−1. While at 785 nm, the average sensitivity is equal to 0.0193°/mM with slightly lower linearity at 94.46 % and Q-factor value of 0.0076 mM−1. The results have proven the ability of hybrid material Au–ZnO as a sensing performance enhancer for detecting uric acid when compared with bare Au and can be further explored in experimental work.

In a fiber-based surface plasmon resonance (SPR) sensor, with multiple layers, including fluoride glass core, cladding, metal (Ag), graphene and alcohols as the analyte, we focused on comparing the effects of 12 different types of fluoride glass cores from three main groups of fluorozirconate (ZrF4-based), fluoroaluminate (AlF3-based) and fluoroindate (InF3-based). The comparison was conducted to evaluate the sensor’s sensitivity and figure of merit (FOM) at specific near infrared (NIR) wavelengths (785 nm, 852 nm, 895 nm and 980 nm) while keeping other parameters constant. The highest FOM was consistently observed at the wavelength of 980 nm for all three categories of fluoride glass cores. Among them, the fluoride glass core IZBSC (40 InF3-20 ZnF2-15 BaF2-20 SrF2-5 CaF2) from InF3-based group presented the largest FOM = 1459.15 RIU−1. Furthermore, we observed that the FOM of the fiber types belonging to the ZrF4-based and InF3-based categories increased with the wavelength. However, the fluoroaluminate fibers showed different trend and they also exhibited the smallest FOM values at 852 nm, 895 nm and 980 nm wavelengths. To enhance the sensor’s performance, we explored the incorporation of an oxide layer into the to the SPR sensor with a ZBLAN (55.8 ZrF4-14.4 BaF2-5.8 LaF3-3.8 AlF3-20.2 NaF) core. We analyzed the effects of various oxide coatings (Sc2O3, Lu2O3, Al2O3, GeO2, TeO2, Ta2O5, MgO, TiO2, and ZnO) on the Ag layer, which has not previously studied, to the best of our knowledge. Among the different oxide coatings, the Ta2O5 layer, with optimized thickness, exhibited a significant enhancement, achieving FOM of 1631.43 RIU−1.

This article investigates the design of a surface plasmon resonance (SPR) sensor that utilizes carbon nanotubes (CNT) and graphene to detect formalin concentration in water. The proposed sensor's design optimization and performance evaluation are achieved by implementing Gradient Boosting Regression (GBR), a machine learning (ML) algorithm, and the artificial hummingbird algorithm. An iterative transfer matrix technique is employed to create training and test sets for machine learning analysis, and a dataset of 8505 × 8 is obtained. The optimized thickness of Ag, CNT, and graphene 51.71 nm, 0.489 nm, and 4.32 nm were obtained using the artificial hummingbird algorithm. The results demonstrate that the SPR sensor achieves excellent reflectance curves, leading to a significant increase in detection sensitivity of 340.44 deg./RIU. Other characteristic parameters such as detection accuracy (DA), full width at half maximum (FWHM), and figure of merit (FoM) have also been evaluated.

We numerically analyze a dual-core gold coated photonic crystal fiber (PCF) biosensor based on surface plasmon resonance that can be used for remote sensing applications in place of the traditional prism-based biosensor. Chemically stable active plasmonic material gold (Au) are positioned outside the fiber structure as a sensing layer to facilitate the construction of the sensor. From finite element method (FEM) based simulation, it is shown that the proposed sensor has the maximum wavelength sensitivity of 5000 nm/RIU. In addition, the amplitude sensitivity of the sensor is 267.66 RIU−1 with the resolution of 2.00 × 10−5 RIU−1 having sensing range of analyte refractive index 1.30 to 1.40. The suggested two-ring dual-core PCF sensor can be used to detect biological analytes, organic compounds, biomolecules, and other unidentified analytes due to its high sensitivity, enhanced sensing resolution, and suitable linearity properties. The proposed sensor has high sensitivity and wide operating range; from visible to mid-infrared which enables the detection of various biomolecules with different absorption or fluorescence spectra. Overall, the unique combination of structural design and optical properties make hexagonal PCF biosensor a promising and innovative platform for advanced and high-performance biosensing applications.

We propose an air-silica core microstructured optical fiber-based surface plasmon resonance (SPR) sensor to simultaneously measure temperature and refractive index (RI). The sensing channel is formed by coating the outside of the fiber with a gold film and a polydimethylsiloxane (PDMS) layer as a temperature sensing medium, and then being immersed into the liquid analyte. The plasmon mode can penetrate through the PDMS layer and then into the analyte, therefore both the temperature and the analyte RI changings can lead to the variations of SPR spectra that will be measured. Our numerical results demonstrate that the proposed sensor can support two resonance peaks in the x-polarized core mode and one resonance peak in the y-polarized core mode, therefore providing two detection approaches, peak-based and polarization-based approaches. By measuring the two peaks in the x-polarized core mode, for the peak-based approach, the temperature coefficients are −2.077 nm/°C and −2.723 nm/°C, and the RI coefficients are 1252 nm/RIU and 1931 nm/RIU, respectively. While by measuring the second peak in x-polarized core mode and the peak in y-polarized core mode, for the polarization-based approach, the temperature coefficients are −2.723 nm/°C and −3.401 nm/°C, and the RI coefficients are 1931 nm/RIU and 2973 nm/RIU, respectively.

A temperature-sensitive gold coated PCF-based surface plasmon resonance (SPR) biosensor was examined for detecting analytes based on their refractive indices. The proposed sensor attained maximum amplitude sensitivities (AS) of 1432 RIU−1 and 1291 RIU−1, wavelength sensitivities (WS) of 13,500 nm/RIU and 13,000 nm/RIU in X and Y- polarized mode individually in RI spectrum of 1.34–1.4. Furthermore, the proposed sensor produced ultimate figure of merit (FOM) values of 546.93 RIU−1 and 521.4601 RIU−1 in x and y polarization modes. High birefringence of 1.5 × 10−3 was also computed for the suggested sensor. Additionally, the proposed sensor shows high temperature sensitivity of 4.5833 nm/°C with a comparable resolution of 2.18××10−2 °C and a maximum FOM value of 0.101 °C−1 in the detection range of −114 °C to 78 °C in the presence of ethanol as a sensing medium. The reported sensor therefore can be considered as a notable solution for any chemical or biological analytes detection.

The Envelope (E) protein of SARS-CoV-2 plays a key role in virus maturation, assembly, and virulence mechanisms. The E protein is characterized by the presence of a PDZ-binding motif (PBM) at its C-terminus that allows it to interact with several PDZ-containing proteins in the intracellular environment. One of the main binding partners of the SARS-CoV-2 E protein is the PDZ2 domain of ZO1, a protein with a crucial role in the formation of epithelial and endothelial tight junctions (TJs). In this work, through a combination of analytical ultracentrifugation analysis and equilibrium and kinetic folding experiments, we show that ZO1-PDZ2 domain is able to fold in a monomeric state, an alternative form to the dimeric conformation that is reported to be functional in the cell for TJs assembly. Importantly, surface plasmon resonance (SPR) data indicate that the PDZ2 monomer is fully functional and capable of binding the C-terminal portion of the E protein of SARS-CoV-2, with a measured affinity in the micromolar range. Moreover, we present a detailed computational analysis of the complex between the C-terminal portion of E protein with ZO1-PDZ2, both in its monomeric conformation (computed as a high confidence AlphaFold2 model) and dimeric conformation (obtained from the Protein Data Bank), by using both polarizable and nonpolarizable simulations. Together, our results indicate both the monomeric and dimeric states of PDZ2 to be functional partners of the E protein, with similar binding mechanisms, and provide mechanistic and structural information about a fundamental interaction required for the replication of SARS-CoV-2.

The controlled orientation of biomolecules on the sensor surface is crucial for achieving high sensitivity and accurate detection of target molecules in biosensing. FcγRI is an immune cell surface receptor for recognizing IgG-coated targets, such as opsonized pathogens or immune complexes. It plays a crucial role in T cell activation and internalization of the cargos, leading downstream signaling cascades. In this study, we repurposed the FcγRI as an analytical ligand molecule for site-oriented ADA capture, a monoclonal antibody-based biosimilar drug, on a plasmonic sensor surface and demonstrated the real-time detection of the corresponding analyte molecule, TNF-α. The study encompasses the analysis of comparative ligand behaviors on the surface, biosensor kinetics, concentration-dependent studies, and sensor specificity assays. The findings of this study suggest that FcγRI has a significant potential to serve as a universal ligand molecule for site-specific monoclonal antibody capture, and it can be used for biosensing studies, as it represents low nanomolar range affinity and excellent selectivity towards the target. However, there is still room for improvement in the surface stability and sensing response, and further studies are needed to reveal its performance on the monoclonal antibodies with various antigen binding sites and glycoforms.

Natamycin (NT) is a polyene natural antimycotic, which has an antimicrobial effect against yeasts and molds and is used as a preservative in the food industry. In the present study, we evaluated NT interaction with bovine serum albumin (BSA) through surface plasmon resonance (SPR) and several spectroscopic techniques, which are accompanied by a molecular docking study. According to the results, the intensity of BSA fluorescence decreased by adding different concentrations of NT. The fluorescence quenching results showed that NT reduces the intensity of BSA fluorescence by forming a complex with BSA through a hybrid quenching. Binding constant decreases from 18.73 to 2.13 (102 M−1) with increasing temperature, which indicates a decrease in complex formation owing to the interaction of NT with BSA. Negative values of ΔH° and ΔS° confirmed that van der Waals forces and hydrogen bonds are the basic forces in the interaction of NT with BSA. Moreover, increasing the equilibrium constants values with increasing temperature indicated that BSA binding to NT decreased. Finally, BSA interaction occurring with NT through Ser 109, Asp 111, Lys 114, Leu 115, Glu 424, and Arg 458 have been verified via molecular docking analysis. Attained results via SPR and fluorimetry showed that the binding constant between BSA and NT decreased when the temperature was raised.

This paper introduces a comprehensive study of a quad-cluster multi-functional Photonic Crystal Fiber (PCF) sensor where gold and Aluminum doped with zinc oxide (AZO) were used as plasmonic materials. A maximum Amplitude Sensitivity (AS) of 5336 RIU−1 and Wavelength Sensitivity (WS) of 40,500 nm/RIU in y pol was obtained incorporating Gold as plasmonic material. When AZO was included as the plasmonic material, AS of 3763 RIU−1 & WS of 9100 nm/RIU for y polarization were determined. The RI detecting range was increased from 1.32 to 1.43 to 1.19–1.42 after using AZO instead of Au that opens up a new horizon for detection. A novel detection technique, ‘Double Step Dual Peak Shift Sensitivity (DS-DPSS)’ was proposed in sensing temperature where highest sensitivity of 1.05 nm/°C having resolution of 0.095 °C for x pol. was achieved. Due to its diverse functionality, the suggested sensor represents a significant advancement in the detection of numerous analytes in biochemical applications.

To enhance the interaction between electromagnetic fields and reduce photoluminescence (PL) lifetime in plasmon-enhanced fluorescence, this study presents a novel approach involving the fabrication of gold (Au) nanohole arrays (ANA) decorated with ring-shaped silver nanoparticles (AgNPs) on a silicon-dioxide (SiO2)/silver (Ag) substrate. The surface plasmon resonance coupling in terms of the PL reactions of ANA substrates with and without ring-shaped AgNPs is investigated via experiments and numerical simulations. The remarkable enhancement of PL intensity of the proposed substrate is attributed to increased absorption, which enables the tuning of surface-enhanced electromagnetic fields. Specifically, the Raman signal of rhodamine 6G (R6G) dye and the PL intensity of 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) molecules are significantly enhanced 3.7 and 2.2 times, respectively, compared to those of the bare ANA substrate. Meanwhile, the PL lifetime is reduced by 46.15%. These results confirm that ANAs decorated with ring-shaped AgNPs can significantly improve plasmon-enhanced fluorescence. The findings presented herein demonstrate the potential to revolutionize biosensing, imaging, and photonics.

In this study, the use of a surface plasmon sensor based on a gold-coated tilted fiber Bragg grating (Au-TFBG) functionalized with graphene oxide (GO) for the detection of lead ions (Pb2+) was demonstrated. To facilitate the modification of the Au-TFBG’s gold surface, cysteamine (Cys) was employed to form a self-assembled monolayer (Cys-SAM). This step was essential for binding the GO sheets on the Au-TFBG surface via the amine functional groups of Cys. Subsequently, the GO-COOH sheets were adsorbed onto the Au-linker surfaces. The sensor’s performance was assessed using several divalent metal ions, including Pb2+, Co2+, Cd2+, Ni2+, Zn2+, and Cu2+. Notably, the sensor exhibited the highest sensitivity for Pb2+. The measured sensitivity and limit of detection (LOD) were recorded at 0.018 dB/µM and 0.711 µM, respectively. Overall, the results demonstrate the potential of the GO-Au-TFBG sensor for sensitive and selective detection of Pb2+ ions, a capability that holds significant importance in environmental monitoring and industrial applications.

Surface plasmon resonance (SPR) is an optical-based detection technique that is of great interest in research because of its rapid detection and label-free features. Current SPR sensor development focuses on modifying the sensing surface for maximum bioreceptor and target immobilization. In this research, we proposed SPR sensor with the Kretschmann configuration modified by adding immobilization layers using a few layers of MXene (Ti3C2T2). MXene is an alternative two-dimensional material suitable for sensors because it has surface termination (T2) which active to immobilize the target. The different surface termination (T=O,OH,F) and number of MXene layers was added on the SPR sensor to obtained the optimum parameters of MXene application. Using Finite-Difference Time-Domain (FDTD) method, the SPR sensor is simulated on a different refractive index background which is assumed as the analyte. The different surface termination produces different SPR curves at the same refractive index conditions, the changes are found in the position of the SPR angle and the width of the curve. Thus, the results of surface termination variations are evaluated based on the full-width half-maximum (FWHM) of the curve which indicates the detection accuracy. Meanwhile, the optimum number of MXene layers was evaluated from the sensitivity value of the MXene-modified SPR sensor to changes in refractive index from 1.33 to 1.34. The result shows that the optimum detection performance was obtained from the application of six layers MXene with surface termination F2(Ti3C2F2). This configuration resulted a sensitivity of 150.131°/RIU and the LOD is 0.01633 RIU.

This paper presents the design and numerical analysis of a circular photonic crystal fiber (PCF) biosensor based on surface plasmon resonance (SPR) for aqueous environments. The proposed biosensor has a geometrical design that uses the cladding at the fiber's exterior to simplify the gold and analyte deposition process. The sensing characteristics and performances of the proposed biosensor are fully investigated with the finite element method. The investigation indicates that the plasmonic material's thickness affects the biosensor's performance. The results of the proposed biosensor demonstrate a wide refractive index range of 1.30 to 1.44, with the highest wavelength or spectral sensitivity as 21,000 nm/RIU and the highest resolution as 9.09×10−6 RIU. The proposed biosensor has a straightforward geometric profile. The proposed biosensor is stable and suited for aqueous surroundings and wide-range detection applications.

Therapeutic drug monitoring (TDM) has played an important role in clinical medicine for precise dosing. Currently, chromatographic technology and immunoassay detection are widely used in TDM and have met most of the needs of clinical drug therapy. However, some problems still exist in practical applications, such as complicated operation and the influence of endogenous substances. Surface plasmon resonance (SPR) has been applied to detect the concentrations of small molecules, including pesticide residues in crops and antibiotics in milk, which indicates its potential for in vivo drug detection. In this study, a new SPR-based biosensor for detecting chloramphenicol (CAP) in blood samples was developed and validated using methodological verification, including precision, accuracy, matrix effect, and extraction recovery rate, and compared with the classic ultra-performance liquid chromatography-ultraviolet (UPLC-UV) method. The detection range of SPR was 0.1–50 ng/mL and the limit of detection was 0.099 ± 0.023 ng/mL, which was lower than that of UPLC-UV. The intra-day and inter-day accuracies of SPR were 98%–114% and 110%–122%, which met the analysis requirement. The results show that the SPR biosensor is identical to UPLC-UV in the detection of CAP in rat blood samples; moreover, the SPR biosensor has better sensitivity. Therefore, the present study shows that SPR technology can be used for the detection of small molecules in the blood samples and has the potential to become a method for therapeutic drug monitoring.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused many deaths and contributed to a tremendous public health concern worldwide since 2020. Angiotensin-converting enzyme 2 (ACE2) binds to the SARS-CoV-2 virus as a receptor. The challenge of different nonhuman primate (NHP) species by SARS-CoV-2 virus demonstrated different effects on virus replication and disease pathology. This study characterizes differences between host ACE2 sequences of three NHP species: Macaca mulatta, Macaca fascicularis, and Chlorocebus sabaeus. In addition, the binding affinity between the ACE2 ectodomain and the SARS-CoV-2 S receptor-binding domain (RBD) was analyzed. Variation of ACE2 sequence among NHP species and the binding affinity may account for different susceptibility and responses to SARS-CoV-2 infection.

P-glycoprotein (P-gp) highly expressed in cancer cells can lead to multidrug resistance (MDR) and the combination of anti-cancer drugs with P-gp inhibitor has been a promising strategy to reverse MDR in cancer treatment. In this study, we established a label-free and detergent-free system combining surface plasmon resonance (SPR) biosensor with styrene maleic acid (SMA) polymer membrane proteins (MPs) stabilization technology to screen potential P-gp inhibitors. First, P-gp was extracted from MCF-7/ADR cells using SMA polymer to form SMA liposomes (SMALPs). Following that, SMALPs were immobilized on an SPR biosensor chip to establish a P-gp inhibitor screening system, and the affinity between P-gp and small molecule ligand was determined. The methodological investigation proved that the screening system had good specificity and stability. Nine P-gp ligands were screened out from 50 natural products, and their affinity constants with P-gp were also determined. The in vitro cell verification experiments demonstrated that tetrandrine, fangchinoline, praeruptorin B, neobaicalein, and icariin could significantly increase the sensitivity of MCF-7/ADR cells to Adriamycin (Adr). Moreover, tetrandrine, praeruptorin B, and neobaicalein could reverse MDR in MCF-7/ADR cells by inhibiting the function of P-gp. This is the first time that SMALPs-based stabilization strategy was applied to SPR analysis system. SMA polymer can retain P-gp in the environment of natural lipid bilayer and thus maintain the correct conformation and physiological functions of P-gp. The developed system can quickly and accurately screen small molecule ligands of complex MPs and obtain affinity between complex MPs and small molecule ligands without protein purification.

We applied Surface Plasmon Resonance (SPR) technology to develop a method for potency screening and quantification of anti-influenza antibodies in minimally processed human plasma samples and intravenous immunoglobulin (IGIV) products. We found that specific antibodies in human plasma or IGIV capable of inhibiting binding of influenza hemagglutinin to receptor-analogous glycans do so in concentration-dependent manner. We ranked the inhibitory activity of plasma samples from multiple donors and found a good correlation (r = 0.87) of SPR assay measurements and conventional hemagglutination inhibition (HAI) assay results. This method was also applied to screen for specific anti-influenza antibodies in IGIV lots manufactured pre- and post-2009 H1N1 pandemic. The SPR method was also applied to study binding inhibition of the intact A/California/04/2009 H1N1 and B/Victoria/504/2000 influenza viruses to α2,6 or α2,3-linked synthetic glycans. In contrast to recombinant H1 hemagglutinin, which was found to interact primarily with α2,6-linked terminal sialic acids, intact H1N1 or influenza B virus recognized both types of receptor analogs with different observed dissociation rates and the inhibitory activity of plasma antibodies was dependent on the type of sialic acid link. The SPR method can provide a high-throughput, time-saving and semi-automated alternative to conventional assays such as HAI or microneutralization in situations where screening of large numbers of plasma donations to identify high titer units is needed to product highly potent immunoglobulins.

This theoretical work proposed an ultra-high sensitive hybrid structure for modified Kretschmann configuration comprised of copper-2D material layer on CaF2 prism for biosensing applications through angular interrogation method. Here, it is reported that such a configuration in association with the low refractive index CaF2 prism provides major contribution for improving the sensitivity. Using 2D materials in the proposed configuration not only acts as a medium for trapping biomolecules but also protect copper from becoming oxidized. On the basis of transfer matrix method, the thickness of copper layer suitability and the number of 2D layers are optimized to achieve high sensitivity, small FWHM, and minimum reflectance. Numerical results shows that a well optimized structure can achieves outstanding results exhibiting sensitivity as high as 514°/RIU with high FOM as 208.09RIU−1. Hence, copper and well optimized 2D material coated on CaF2 prism can be an excellent approach in sensor design for detecting biomolecules.

Chrysanthemum morifolium Ramat. is a kind of food and drug dual-use traditional Chinese medicine possessing multiple pharmacological and biochemical benefits. In our study, a rapid and high-throughput method based on Surface plasmon resonance (SPR) biosensor technology was developed and verified for screening potential xanthine oxidase (XOD) inhibitors exemplarily in the Chrysanthemum morifolium Ramat. Coupled with ultra-high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS), 14 XOD-binders were identified. In the SPR-based biosensor and molecular docking analysis, most compounds exhibited a strong affinity and binding kinetic property (association rate constant, Kon and dissociation rate constant, Koff) for XOD and could be regarded as potential inhibitors. More importantly, to further accurately assess target occupancy of candidate compounds in vivo, a mathematical model was established and verified involving three crucial intrinsic kinetic processes (Pharmacokinetics, Binding kinetic and Target kinetic). Overall, the proposed screening and assessment strategy could be proved an effective theoretical basis for further pharmacodynamic evaluation.

Surface plasmon resonance in optical fibers can result in the creation of a highly sensitive device, compact and robust sensor. Nitrogen dioxide is one of the foremost greenhouse gases responsible for deteoriation of ecosystem and breathing disorder, it plays a direct role in global climate change. To date, all studies on surface plasmon resonance in optical fibers have relied on passive excitation. For the very first time, we propose a novel sensor architecture based on a gain enhancement of surface plasmons in optical fibers in this paper to detect nitrogen dioxide in the atmosphere. Hence, a pair of fiber gratings is embedded in the core, resulting in the formation of a cavity in which incident light with the Bragg wavelength is confined and simulated first in absence of NO2 environment and then by introducing NO2 concentration ranging from (10–100) ppm to accomplish our work, we observed change in reflectance peak varying in accordance with increasing concentration. Thus, the constructive interference between these waves results in optical field gain by a magnitude of 4. Our results indicate that a significant improvement in sensor performance is obtained on active surface plasmon excitation, anticipating to be of importance in high-precision applications.

Investigating peptides and proteins conformations in vitro is of paramount importance in biochemistry and cell biology, as the understanding of many physiological pathways and pathological processes, which underscore the onset and progression of “conformational diseases”, is closely dependent on the actual possibility of monitoring the conformation, oligomerization and the specific properties, such as metal-binding features, that proteins adopt in complex systems.In this work, we report a newly designed Surface Plasmon Resonance (SPR) based dispersion analysis, hereby named D-SPR, which allows to measure the diffusion coefficients of molecules with unprecedented easiness and precision. Several small molecules have been tested with this new approach, and the diffusion coefficients obtained are in accordance with the values reported in the literature. A theoretical background is given and the newly designed method has been also applied to carnosine, a dipeptide which has recently attracted great attention by virtues of its anti-oxidative, anti-aggregating and enzyme activating properties. Results clearly show the high performance of the new method, which is based on the newly unveiled SPR capability to measure diffusion coefficients, to give information on carnosine metal-induced oligomerization, expanding the potentiality of commonly used SPR instruments well over the canonic investigation of biomolecular interactions.

The global pandemic of COVID-19 caused by SARS-CoV-2 has caused more than 400 million infections with more than 5.7 million deaths worldwide, and the number of validated therapies from natural products for treating coronavirus infections needs to be increased. Therefore, the virtual screening of bioactive compounds from natural products based on computational methods could be an interesting strategy. Among many sources of bioactive natural products, compounds from marine organisms, particularly microalgae and cyanobacteria, can be potential antiviral agents. The present study investigates bioactive antiviral compounds from microalgae and cyanobacteria as a potential inhibitor of SARS-CoV-2 by targeting Angiotensin-Converting Enzyme II (ACE2) using integrated in silico and in vitro approaches. Our in silico analysis demonstrates that C-Phycocyanin (CPC) can potentially inhibit the binding of ACE2 receptor and SARS-CoV-2 with the docking score of −9.7 kcal mol−1. This score is relatively more favorable than the native ligand on ACE2 receptor. Molecular dynamics simulation also reveals the stability interaction between both CPC and ACE2 receptor with a root mean square deviation (RMSD) value of 1.5 Å. Additionally, our in vitro analysis using the surface plasmon resonance (SPR) method shows that CPC has a high affinity for ACE2 with a binding affinity range from 5 to 125 µM, with KD 3.37 nM. This study could serve as a reference to design microalgae- or cyanobacteria-based antiviral drugs for prophylaxis in SARS-CoV-2 infections.

Elucidating the active components of traditional Chinese medicine (TCM) is essential for understanding the mechanisms of TCM and promote its rational use as well as TCM-derived drug development. Recent studies have shown that surface plasmon resonance (SPR) technology is promising in this field. In the present study, we propose an SPR-based integrated strategy to screen and analyze the major active components of TCM. We used Radix Paeoniae Alba (RPA) as an example to identify the compounds that can account for its anti-inflammatory mechanism via tumor necrosis factor receptor type 1 (TNF-R1). First, RPA extraction was analyzed using an SPR-based screening system, and the potential active ingredients were collected, enriched, and identified as paeoniflorin and paeonol. Next, the affinity constants of paeoniflorin and paeonol were determined as 4.9 and 11.8 μM, respectively. Then, SPR-based competition assays and molecular docking were performed to show that the two compounds could compete with tumor necrosis factor-α (TNF-α) while binding to the subdomain 1 site of TNF-R1. Finally, in biological assays, the two compounds suppressed cytotoxicity and apoptosis induced by TNF-α in the L929 cell line. These findings prove that SPR technology is a useful tool for determining the active ingredients of TCM at the molecular level and can be used in various aspects of drug development. The SPR-based integrated strategy is reliable and feasible in TCM studies and will shed light on the elucidation of the pharmacological mechanism of TCM and facilitate its modernization.

BN50/NiO50 and Au-loaded BN50/NiO50 nanocomposite films were separately fabricated on the glass substrates for carrier transport and photoconductivity properties. X-ray diffraction pattern of the films show the hexagonal structure of BN and presence of defect states by Nelson Riley factor analysis. Morphological images show spherical shaped particles with highly porous structure. The incorporation of NiO may hindered growth of BN layers and resulted in spherical particles. Temperature-dependent conductivity describes semiconductor transport behaviour for deposited nanocomposite films. Thermal activation conduction with low activation energy (∼0.308 eV) may be responsible for the resulting conductivity. Further, the light intensity dependent photoelectrical properties of BN50/NiO50 and Au-loaded BN50/NiO50 nanocomposites have been explored. The effect of Au nanoparticles loading on enhanced photo-conductivities (∼22% increase) than bare nanocomposite film has been elaborated by proposed mechanism. This study provided the insightful information for carrier transport and photoconductivity of BN-based nanocomposites.

The control of light in photonic crystal fiber (PCF) is a special characteristic that is obtained due to the relations between material and light. In this paper, a surface plasmon resonance (SPR) based PCF sensor is introduced with two open-channel which cover an extensive field of bio-detection applications. Gold (Au) is considered as an effective plasmonic ingredient. The transformation of light through the fiber core is coupled with the gold and stimulates SPR. The proposed PCF-SPR sensor reports the highest wavelength sensitivity (WS) of 7000 nm/RIU (refractive index unit) as well as an amplitude sensitivity (AS) of 593.61 RIU−1. It also acquires an increased sensor resolution of 1.43 × 10−5 RIU and a decent figure of merit (FOM) is 94.97 RIU−1. Additionally, the operating constraints of the sensor such as corresponding air-holes diameter, the pitch, gold layer (Au) thickness and open-channel radius are revised to improve detection performance. The overall measurement is carried out over a broad range of variations in refractive index (RI) from 1.33 to 1.40. The sensor's appreciable performance makes it suitable for bio-sensing applications.

Triangular silver nanoplates exhibit excellent optical and catalytic properties in many fields, such as catalysts, sensors and bio-medicine. In this paper, triangular nanoplates were generated just in the presence of sodium citrate through a light-induced ripening process, which were converted from spherical silver nanoparticles by reducing silver nitrate with sodium borohydride. By using UV–Vis spectroscopy, particle size analyzer, transmission electron microscopy (TEM) and Ag+ concentration analysis, the effects of precursors during the preparation of triangular nanoplates were systematically investigated and the optimal experimental conditions were determined. Based on density functional theory (DFT), the adsorption energies of citrate ion, malate ion and tartronate ion on Ag (111), (110) and (100) were calculated. In addition, theoretical calculations coupled with experimental observations showed that citrate ion as capping agent could more preferentially bind to Ag (111) and thus blocked Ag (111) while only allowing extensive growth along the lateral direction. This well explains sodium citrate is an efficient agent in preparing triangular silver nanoplates.

In this paper, a novel photonic crystal fiber (PCF) is numerically characterized by finite element method (FEM) based mode solver software for bio-analyte sensing, particularly for detecting natural sucrose having a refractive index (RI) ranging from 1.29 to 1.42. The proposed PCF consists of a solid silica core and adjacent rectangular air holes in the cladding. To introduce the widely known surface plasmon resonance (SPR) phenomenon into the proposed sensor, the entire outer surface is covered by a thin gold film. The sensing methodology is appropriately addressed, and each of the designed parameters of the sensor structure is tuned sufficiently to find out the desired sensing performance. Considering RI change at the outer surface, appealing sensing performance such as maximum wavelength sensitivity of 216,000 nm/RIU and maximum amplitude sensitivity of 1138.52 RIU-1 are attained. In addition, the proposed sensor possesses a resolution of 4.63×10-7 RIU, linearity of 0.9891, the figure of merit of 1981.651 RIU-1, and detection accuracy of 0.019802 nm-1. However, except for sucrose detection, the promising sensing characteristics of the proposed sensor indicate its potential to be effectively used to detect biochemical and organic samples.© 2022 Optica Publishing Group under the terms of the Optica Publishing Group Publishing Agreement.

Currently, the controllable fabrication of ultra-small, highly dispersed, stable, and functionalized metal nanoparticles (MNPs) by is crucial for the industrially applicable applications. The simple fabrication of Schiff base stabilized gold nanoparticles (AuNPs) does not require stringent experimental conditions, and thus, a straight forward, rapid, and efficient method for the fabrication of highly active catalysts for treating environmental pollutants. Here, we demonstrate the facile fabrication of AuNPs in aqueous solutions via the reduction of hydrogen tetrachloroaurate(III) trihydrate (HAuCl4⋅3H2O) by the Schiff base ligand ((1-((E)-(4-(trifluoromethoxy)phenylimino)methyl)naphthalen-2-ol)) with ultra-small size (

Severe acute respiratory syndrome-associated coronavirus 2 is a major global health issue and is driving the need for new therapeutics. The surface spike protein, which plays a central role in virus infection, is currently the target for vaccines and neutralizing treatments. The emergence of novel variants with multiple mutations in the spike protein may reduce the effectiveness of neutralizing antibodies by altering the binding activity of the protein with angiotensin-converting enzyme 2 (ACE2). To understand the impact of spike protein mutations on the binding interactions required for virus infection and the effectiveness of neutralizing monoclonal antibody (mAb) therapies, the binding activities of the original spike protein receptor binding domain (RBD) sequence and the reported spike protein variants were investigated using surface plasmon resonance. In addition, the interactions of the ACE2 receptor, an anti-spike mAb (mAb1), a neutralizing mAb (mAb2), the original spike RBD sequence, and mutants D614G, N501Y, N439K, Y453F, and E484K were assessed. Compared to the original RBD, the Y453F and N501Y mutants displayed a significant increase in ACE2 binding affinity, whereas D614G had a substantial reduction in binding affinity. All mAb-RBD mutant proteins displayed a reduction in binding affinities relative to the original RBD, except for the E484K-mAb1 interaction. The potential neutralizing capability of mAb1 and mAb2 was investigated. Accordingly, mAb1 failed to inhibit the ACE2-RBD interaction while mAb2 inhibited the ACE2-RBD interactions for all RBD mutants, except mutant E484K, which only displayed partial blocking.

A novel bis-γ-butyrolactone grifolamine A (1), the first γ-butyrolactone dimer from nature, together with three known γ-butyrolactones (2–4), was isolated from the byproduct from Grifola frondosa polysaccharides preparation process. The structure and stereochemistry of grifolamine A (1) were elucidated by extensive spectroscopic analysis combined with quantum chemical calculation. The biosynthetic origin of compound 1, as well as 2–4 was proposed. Grifolamine A (1) showed an intense inhibition against α-glucosidase in vitro. The underlying inhibitory mechanism was revealed by surface plasmon resonance (SPR), molecular docking, molecular dynamics (MD) simulation and binding free energy calculation. SPR revealed that grifolamine A exhibited a strong affinity to α-glucosidase with an equilibrium dissociation constant (KD) value of 1.178 × 10−4 M. Molecular docking manifested that grifolamine A sat at the active pocket of α-glucosidase by van der Waals force, alkyl interaction and carbon hydrogen bonds, and consequently changed the micro-environmental structure of α-glucosidase. MD simulation revealed that grifolamine A had high binding affinity to α-glucosidase with average free energy of −25.2 ± 3.2 kcal/mol. Free energy decomposition indicated amino acid residues including PHE298, PHE308, PHE309, PHE155 and ARG310 at the binding pocket played a strongly positive effect on the interaction between grifolamine A and α-glucosidase. Our findings provide valuable information for the design and development of novel α-glucosidase inhibitors based on γ-butyrolactone skeleton.

This paper presents numerical modeling of surface plasmon resonance (SPR) sensors for cancerous cell detection by employing tin selenide allotrope (SnSe) and tungsten disulfide (WS2). The structure is based on the Kretschmann configuration that is coated with a gold metallic film to excite the surface plasmons. In this study, we have considered different cancerous cells that contain both healthy and affected cells for the detection process. The transfer matrix method is exploited to analyze the performance parameters at a 633 ​nm wavelength. Initially, the thickness of bimetallic layers is optimized by observing the sensor parameters. Furthermore, the numerical analysis is performed and results show that the maximum attained parameters for the proposed sensor are a sensitivity of 236.43deg/RIU, quality factor of 70.3 RIU−1 and detection accuracy of 1.5. Finally, the field distribution of the proposed sensor is executed by using two-dimensional Opti-FDTD software.

The current study is to develop an easy and eco-friendly method for the synthesis of AgNPs using aqueous seed extract of E. robusta (Er-AgNPs) and evaluated the extract to know the effects of catalytic, antibacterial, antidiabetic, and antioxidant activities. Er-AgNPs were characterized via several techniques, including UV-vis absorption, PL, XRD, FTIR, and TEM, which confirmed the formation of Er-AgNPs. The face centered cubic (FCC) crystal structure of the biosynthesized Er-AgNPs was revealed by the XRD analysis. FTIR study confirmed the presence of OH and NH functional groups of secondary molecules of seed extract capped on the AgNPs surface. The produced Er-AgNPs were dark brown in color with an almost spherical shape in size ranging from 5 to 15 nm. The presence of Er-AgNPs (1 mL) exhibited considerably enhanced dyes degradation (CY, 95.12% and EY, 97.82% in 18 min), antibiotics degradation (TC, 96.45% and CIP, 98.01% in 21 min), and nitroaromatics reduction (4-NP, 88.12% and 4-NA, 92.45% in 15 min). The Er-AgNPs showed a significant antibacterial activity on multi-drug resistance bacteria. These nanoparticles also exhibited strong antioxidant activities for the DPPH assay. Remarkable antidiabetic (α-glucosidase, α-amylase, and HbA1C) activities were noticed with the use of Er-AgNPs. This is the first report on the biosynthesis of AgNPs using seeds extracted from E. robusta.

Rapid development in electronic and optical devices has unequivocally eased human life to an appreciable extent, which, however, involved lots of hard work in the miniaturization of technology. The continual fabrication and characterization of devices in the field of spectroscopy, security/imaging, information technology, nanophotonics, opticalfiber-based devices, photodetectors, etc. is going on in full swing. By citing exemplary instances, this article comprehensively shows various applications based on nanophotonics and optical fiber technologies. This article focuses on the recent advancements in the field of nanophotonics and optical fiber to use them in sensing and active devices. Initiating with an overview of the recent areas of research, design, and implementation of nanophotonics and optical fiber, the paper discusses the instrumentation used for fabricating and characterization of surface plasmon resonance (SPR) based fiber optic refractive index sensor and visible photodetector furnished by cadmium sulfide (CdS) nanostructures. The fabricated CdS nanostructures were characterized using XRD, Raman, SEM, UV–vis and photoluminescence spectroscopic techniques so as to obtain the required/favourable properties for the realization of fiber-optic refractive index sensing device employing SPR technique and for visible photodetection applications. The performance parameters of both the fabricated devices were also evaluated and explained in detail. Lastly, the paper outlines the limitations, challenges as well as available opportunities in this avenue.