Study of a Surface Plasmon Resonance Optical Fiber Sensor Based on Periodically Grating and Graphene

Silicon - In this paper an optical fiber sensor based on plasmonic resonance of graphene and periodically grating is designed and investigated. The proposed sensor consists of an optical fiber core...     

Investigation of Silicon Carbide Based Optical Fiber Coupled Surface Plasmon Resonance Sensor

The performance parameter of a surface plasmon resonance sensor having silicon carbide as an additional layer is theoretically investigated. Using the transfer matrix method, the reflectivity and performance parameter in terms of sensitivity, detection accuracy and quality parameter have been calculated. To understand the dependency of sensitivity and detection accuracy in the proposed sensor, the model electric field, propagation length and penetration depth in aqueous media as well as the metal layer are calculated. It is observed that the sensitivity and detection accuracy of the proposed waveguide based sensor depend on the thickness of the silicon carbide layer. Therefore, by choosing a suitable value of thickness of the silicon carbide layer the overall performance of the proposed waveguide can be increased.     

Effect of a Metamaterial and Silicon Layers on Performance of Surface Plasmon Resonance Biosensor in Infrared Range

Silicon - Metamaterial based surface plasmon resonance biosensor for enhancement of performance parameters at near infrared wavelengths is presented. The thickness of the metamaterial layer and...     

SPR生物传感技术中的光学系统研究

SPR生物传感器是一种强有力的动态检测手段,具有实时检测、无需标记等优点,能够准确、灵敏、快速、简便地检测多种生化指标。本文通过对表面等离子体共振(SPR)分子相互作用仪的光学系统的研究,提出了一种简易光学系统,并通过实验验证了本光学系统的可行性。     

Comparative study of a Surface Plasmon Resonance Biosensor based on Metamaterial and Graphene

In this study, a surface plasmon resonance biosensor at near infrared frequency based on a metamaterial is proposed. The proposed biosensor utilizes the properties of plasmons and metamaterial for enhancement of its performance parameters i.e. sensitivity, detection accuracy and quality factor. The thickness of the metamaterial and gold film has been optimized for optimal performance of the proposed biosensor at near infrared wavelengths. Results obtained from the proposed biosensor were compared with existing two-dimensional nanomaterials such as a graphene based biosensor and a conventional surface plasmon resonance biosensor. Finally, it is observed that the performance parameters of the proposed biosensor are very high when compared to existing surface plasmon resonance biosensors.     

Interaction between Nanoparticles,Membranes and Proteins: A Surface Plasmon Resonance Study

Regardless of the promising use of nanoparticles (NPs) in biomedical applications, several toxic effects have increased the concerns about the safety of these nanomaterials. Although the pathways for NPs toxicity are diverse and dependent upon many parameters such as the nature of the nanoparticle and the biochemical environment, numerous studies have provided evidence that direct contact between NPs and biomolecules or cell membranes leads to cell inactivation or damage and may be a primary mechanism for cytotoxicity. In such a context, this work focused on developing a fast and accurate method to characterize the interaction between NPs, proteins and lipidic membranes by surface plasmon resonance imaging (SPRi) technique. The interaction of gold NPs with mimetic membranes was evaluated by monitoring the variation of reflectivity after several consecutive gold NPs injections on the lipidic membranes prepared on the SPRi biochip. The interaction on the membranes with varied lipidic composition was compared regarding the total surface concentration density of gold NPs adsorbed on them. Then, the interaction of gold and silver NPs with blood proteins was analyzed regarding their kinetic profile of the association/dissociation and dissociation constants (k_off). The surface concentration density on the membrane composed of 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine and cholesterol (POPC/cholesterol) was 2.5 times higher than the value found after the injections of gold NPs on POPC only or with dimethyldioctadecylammonium (POPC/DDAB). Regarding the proteins, gold NPs showed preferential binding to fibrinogen resulting in a value of the variation of reflectivity that was 8 times higher than the value found for the other proteins. Differently, silver NPs showed similar interaction on all the tested proteins but with a variation of reflectivity on immunoglobulin G (IgG) 2 times higher than the value found for the other tested proteins.     

Application of Conducting Polymer Layer for Measurement of Ag Nanoparticle Concentration Using Surface Plasmon Resonance

An application of polypyrrole and polypyrrole–chitosan were presented to measure the concentration of silver ion and silver nanoparticles using surface plasmon resonance sensor. These results were compared to those for atomic absorption spectroscopy method. The sensing layers were prepared using an electrodeposition on gold layer with the sensor limitation at about 1mg/L, and well correlated to prior atomic absorption spectroscopy results. The sensor with a polypyrrole-chitosan layer was more sensitive and accurate than the sensor with just a polypyrrole layer.     

Site‐Specific Immobilization of the Peptidoglycan Synthase PBP1B on a Surface Plasmon Resonance Chip Surface

Surface plasmon resonance (SPR) is one of the most powerful label‐free methods to determine the kinetic parameters of molecular interactions in real time and in a highly sensitive way. Penicillin‐binding proteins (PBPs) are peptidoglycan synthesis enzymes present in most bacteria. Established protocols to analyze interactions of PBPs by SPR involve immobilization to an ampicillin‐coated chip surface (a β‐lactam antibiotic mimicking its substrate), thereby forming a covalent complex with the PBPs transpeptidase (TP) active site. However, PBP interactions measured with a substrate‐bound TP domain potentially affect interactions near the TPase active site. Furthermore, in vivo PBPs are anchored in the inner membrane by an N‐terminal transmembrane helix, and hence immobilization at the C‐terminal TPase domain gives an orientation contrary to the in vivo situation. We designed a new procedure: immobilization of PBP by copper‐free click chemistry at an azide incorporated in the N terminus. In a proof‐of‐principle study, we immobilized Escherichia coli PBP1B on an SPR chip surface and used this for the analysis of the well‐characterized interaction of PBP1B with LpoB. The site‐specific incorporation of the azide affords control over protein orientation, thereby resulting in a homogeneous immobilization on the chip surface. This method can be used to study topology‐dependent interactions of any (membrane) protein.     

Effect of Molybdenum Disulfide Layer on Surface Plasmon Resonance Biosensor for the Detection of Bacteria

In this study, a molybdenum disulfide (MoS₂) based surface plasmon resonance (SPR) biosensor is proposed. The reflectance curves for the proposed SPR biosensor are analyzed and compared with the graphene based and the conventional SPR biosensors. It is observed that the performance parameters of the proposed biosensor- sensitivity, detection accuracy, and the quality factor are enhanced by the utilization of the adsorption property of MoS₂ for monolayer and bi-layer MoS₂. Also, the effect of increasing the number of layers of MoS₂ on the reflectance curve is analyzed and compared.     

Studies on the Interactions of Copper and Zinc Ions with ��-Amyloid Peptides by a Surface Plasmon Resonance Biosensor

The aggregation of β-amyloid peptide (Aβ) into fibrils plays an important role in the pathogenesis of Alzheimer’s disease (AD). Metal ions including copper and zinc are closely connected to the precipitation and toxicity of Aβ. In this study, a surface plasmon resonance (SPR) biosensor was constructed to investigate the interactions between Aβ and metal ions. Aβ peptide was immobilized on the SPR chip surface through a preformed alkanethiol self-assembled monolayer (SAM). Our observations indicate that the immobilized Aβ undergoes a conformational change upon exposure to the metal ions. A difference in metal binding affinity between Aβ_1–28 and Aβ_1–42 was also detected. The results suggest that SPR is an effective method to characterize the interactions between Aβ and metal ions.     

A Theoretical Study on the Influence of Carbon and Silicon Doping on the Structural and Electronic Properties of (BeO)12 Nanocluster

The influence of carbon and silicon atoms doping on the structural and electronic properties of the (BeO)₁₂ nanocluster is investigated through density functional theory calculations. It has been found that doping process induces local deformation at bond lengths and angles near the doping site. The results indicate that C or Si doping decreases the energy gap of the (BeO)₁₂ nanocluster. It seems that the electronic character of the (BeO)₁₂ nanocluster could be adjusted by particular impurity. The electronic charge distributions are also analyzed using Atoms in Molecules theory. Natural bond orbital analyses are also performed for scrutinizing the structural properties of the considered nanoclusters.     

Profile Prediction and Fabrication of Wet-Etched Gold Nanostructures for Localized Surface Plasmon Resonance

Dispersed nanosphere lithography can be employed to fabricate gold nanostructures for localized surface plasmon resonance, in which the gold film evaporated on the nanospheres is anisotropically dry etched to obtain gold nanostructures. This paper reports that by wet etching of the gold film, various kinds of gold nanostructures can be fabricated in a cost-effective way. The shape of the nanostructures is predicted by profile simulation, and the localized surface plasmon resonance spectrum is observed to be shifting its extinction peak with the etching time.     

Experimental Evaluation of Quantum Dots and Antibodies Conjugation by Surface Plasmon Resonance Spectroscopy

The application of antibody-functionalized quantum dots (QDs) in different areas has been widely described in the literature. However, a standard routine method for obtaining information on the conjugation efficiency of QDs with antibodies in terms of the interaction of the functionalized QDs with a specific antigen is still lacking. Herein, surface plasmon resonance (SPR) spectroscopy is proposed for this purpose. Gold-coated SPR sensor disks were modified with a self-assembled monolayer of 11-mercaptoundecanoic acid, and carbodiimide cross-linker chemistry was used to covalently immobilize the CD44 biomarker on the premodified surface (Au/CD44). Meanwhile, QDs functionalized with amine-derivatized polyethylene glycol (PEG) (QDs-NH₂) were chosen for conjugation with antibodies because of their low non-specific adsorption on the Au/CD44 surface. Prior to conjugation, the surface binding capacity (B_max) and equilibrium dissociation constant (K_D) of the specific antibodies against CD44 (anti-CD44) were found to be 263.32 ± 2.44 m° and 1.00 × 10⁻⁷ ± 2.29 × 10⁻⁹ M, respectively. QDs-NH₂ and anti-CD44 were conjugated at their initial molar ratios of 1:3, 1:5, 1:10 and 1:12. SPR measurements showed that the conjugates (QDs-anti-CD44) prepared using 1:10 and 1:12 molar ratios interacted comparably with immobilized CD44 biomarkers. The equilibrium angles in the case of 10- and 12-fold concentrations of anti-CD44 were calculated to be 60.43 ± 4.51 and 61.36 ± 4.40 m°, respectively. This could be explained by the QDs-NH₂ and anti-CD44 having a similar surface loading (about four molecules per QDs-NH₂) and similar hydrodynamic diameters, which were 46.63 ± 3.86 and 42.42 ± 0.80 nm for the 1:10 and 1:12 ratios, respectively. An initial QDs-NH₂: anti-CD44 molar ratio of 1:10 was chosen as being optimal. SPR spectroscopy proved to be the right choice for QDs-anti-CD44 conjugation optimization, and can be used for the evaluation of conjugation efficiency for other nanostructures with various bio-recognition molecules.     

Boosting the Photoelectrochemical Performance of Au/ZnO Nanorods by Co-Occurring Gradient Doping and Surface Plasmon Modification

Band bending modification of metal/semiconductor hybrid nanostructures requires low-cost and effective designs in photoelectrochemical (PEC) water splitting. To this end, it is evinced that gradient doping of Au nanoparticles (NPs) inwards the ZnO nanorods (NRs) through thermal treatment facilitated faster transport of the photo-induced charge carriers. Systematic PEC measurements show that the resulting gradient Au-doped ZnO NRs yielded a photocurrent density of 0.009 mA/cm² at 1.1 V (vs. NHE), which is 2.5-fold and 8-fold improved compared to those of Au-sensitized ZnO and the as-prepared ZnO NRs, respectively. The IPCE and ABPE efficiency tests confirmed the boosted photoresponse of gradient Au-incorporated ZnO NRs, particularly in the visible spectrum due to the synergistic surface plasmonic effect of Au NPs. A gradient Au dopant profile promoted the separation and transfer of the photo-induced charge carriers at the electrolyte interface via more upward band bending according to the elaborated electrochemical impedance spectroscopy and Kelvin probe force microscopy analyses. Therefore, this research presents an economical and facile strategy for preparing gradient plasmonic noble NP-incorporated semiconductor NRs, which have excellent potential in energy conversion and storage technologies.     

硅表面化学镀镍研究

化学镀镍具有优异的特性,广泛应用于塑料、半导体和金属的表面保护涂层,其中半导体硅表面化学镀镍已有深入的研究。针对硅基体表面化学镀镍的研究进展和成果进行了详细介绍,主要包括硅基体表面的预处理方法、化学镀镍工艺,硅基体表面化学镀镍的反应机理和添加剂对化学镀镍的影响研究,并总结展望了硅基体表面化学镀镍的发展趋势。     

纳米金掺杂二氧化钛复合材料制备及表面等离子体效应

当纳米金颗粒受到可见光和近红外光波照射时,其表面导带的自由电子会以一定的频率局限在纳米金颗粒周围振荡,并在其表面激发较强的等离子体共振效应.本文基于纳米金颗粒的表面等离子体效应,设计了一种纳米金颗粒掺杂二氧化钛电荷传输层的器件结构(FTO/TiO2 dense layer(d-TiO2)/Au@TiO2/amorphous TiO2(a-TiO2)/CH3 NH3 PbI3/spiro/Au).在该结构中,采用致密的非晶TiO2和介孔层TiO2能够缩短光电子的迁移距离,降低电子-空穴的复合概率,提高器件的光电性能.纳米金掺杂二氧化钛的表面等离子体效应,促进了光电子的吸收,提高了复合材料的吸光系数和光电性能.     

Application of Polypyrrole-Chitosan Layer for Detection of Zn (II) and Ni (II) in Aqueous Solutions Using Surface Plasmon Resonance

In this study, a polypyrrole-chitosan layer was applied to detect zinc and nickel ions in aqueous solution using surface plasmon resonance. The resonance angle shift was found to monitor the binding interaction between ions and the polymer film. The polypyrrole-chitosan film was coated on the gold layer with an electrochemical deposition method. The Langmuir model was compared with the Freundlich model to explain the binding. Consequently, the Langmuir model was fitted with experimental data better than the Freundlich equation, and the detection limit was 0.01 ppm.     

On the Use of Surface Plasmon Resonance Biosensing to Understand IgG-FcγR Interactions

Surface plasmon resonance (SPR)-based optical biosensors offer real-time and label-free analysis of protein interactions, which has extensively contributed to the discovery and development of therapeutic monoclonal antibodies (mAbs). As the biopharmaceutical market for these biologics and their biosimilars is rapidly growing, the role of SPR biosensors in drug discovery and quality assessment is becoming increasingly prominent. One of the critical quality attributes of mAbs is the N-glycosylation of their Fc region. Other than providing stability to the antibody, the Fc N-glycosylation influences immunoglobulin G (IgG) interactions with the Fcγ receptors (FcγRs), modulating the immune response. Over the past two decades, several studies have relied on SPR-based assays to characterize the influence of N-glycosylation upon the IgG-FcγR interactions. While these studies have unveiled key information, many conclusions are still debated in the literature. These discrepancies can be, in part, attributed to the design of the reported SPR-based assays as well as the methodology applied to SPR data analysis. In fact, the SPR biosensor best practices have evolved over the years, and several biases have been pointed out in the development of experimental SPR protocols. In parallel, newly developed algorithms and data analysis methods now allow taking into consideration complex biomolecular kinetics. In this review, we detail the use of different SPR biosensing approaches for characterizing the IgG-FcγR interactions, highlighting their merit and inherent experimental complexity. Furthermore, we review the latest SPR-derived conclusions on the influence of the N-glycosylation upon the IgG-FcγR interactions and underline the differences and similarities across the literature. Finally, we explore new avenues taking advantage of novel computational analysis of SPR results as well as the latest strategies to control the glycoprofile of mAbs during production, which could lead to a better understanding and modelling of the IgG-FcγRs interactions.