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The FLAG-tag/anti-FLAG system is a widely used biochemical tool for protein detection and purification. Anti-FLAG M2 is the most popular antibody against the FLAG-tag, due to its ease of use, versatility, and availability in pure form or as bead conjugate. M2 binds N-terminal, C-terminal and internal FLAG-tags and binding is calcium-independent, but the molecular basis for the FLAG-tag specificity and recognition remains unresolved. Here we present an atomic resolution (1.17 Å) structure of the FLAG peptide in complex with the Fab of anti-FLAG M2, revealing key binding determinants. Five of the eight FLAG peptide residues form direct interactions with paratope residues. The FLAG peptide adopts a 310 helix conformation in complex with the Fab. These structural insights allowed us to rationally introduce point mutations on both the peptide and antibody side. We tested these by surface plasmon resonance, leading us to propose a shorter yet equally binding version of the FLAG-tag for the M2 antibody.

Surface plasmon resonance (SPR) is a label-free, versatile and highly sensitive method for studying molecular interactions in real time. It is widely used by industry and academia alike in fields ranging from Alzheimer’s disease research to detection of heavy metals. In this review, studies published during the last 10 years using Biacore or other SPR instruments were compiled and compared. Trends were also identified in the field. Amine coupling was found to be the most common ligand strategy for proteins, and most SPR research related to the field of medicine. Furthermore, three main purposes of an SPR experiment were identified: To determine the affinity between a pair of molecules, kinetics between a pair of molecules or to detect a certain molecule in a solution. The results presented are often related to these three purposes, and are most often presented and evaluated in terms of kinetic, affinity and sensitivity constants. SPR can be used for studying a broad range of molecular interactions, and an overview was obtained by dividing up the field into different parts based on molecular interactions and SPR methods. The study of molecular interactions using SPR was divided into protein-protein interactions (PPIs), antibody-antigen, protein-biomolecule interactions, interactions between proteins and small molecules, and non-conventional SPR methods. Non-conventional SPR methods include localized surface plasmon resonance (LSPR) and SPR imaging (SPRi), which are both based on the same optical sensing principles as SPR.

Materials that intrinsically exhibit localized surface plasmon resonance (LSPR) in the visible region have been predominantly researched on nanoparticles (NPs) composed of coinage metals, namely Au, Ag, and Cu. Here, as a coinage metal-free intermetallic NPs, colloidal PtIn₂ NPs with a C1 (CaF₂-type) crystal structure are synthesized by the liquid phase method, which evidently exhibit LSPR at wavelengths similar to face-centered cubic (fcc)-Au NPs. Computational simulations pointed out differences in the electronic structure and photo-excited electron dynamics between C1-PtIn₂ and fcc-Au NPs; reduces interband transition and stronger screening with smaller number of bound d-electrons compare with fcc-Au are unique origins of the visible plasmonic nature of C1-PtIn₂ NPs. These results strongly indicate that the intermetallic NPs are expected to address the development of alternative plasmonic materials by tuning their crystal structure and composition.

Surface plasmon resonance (SPR) sensors have attracted great attention in recent years for various applications such as medical diagnosis and biochemical materials. Among SPR sensors, D-shaped structures based on photonic crystal fibers (PCFs) have shown very high performance and are easy to use. In this paper, a simple design of SPR sensors based on the D-shaped PCFs with the optimized geometrical parameters is proposed. Gold and silver are considered as plasmonic layers on the surface of the D-shaped PCF sensor. By performing multiple simulations using the finite-difference eigenmode (FDE) method, various values of gold and silver thicknesses are investigated to achieve the highest sensitivity and resolution. The results indicate that the highest sensitivity and resolution of 25,600 nm/RIU and 3.9×10-6 are achieved respectively for a gold thickness of 44 nm at the analyte refractive index (RI) of 1.41. Meanwhile, for an analyte RI range of 1.29 to 1.40, silver demonstrates greater sensitivity than gold in the same range. The proposed sensor with superior characteristics compared with other SPR sensors can be considered as a very good candidate for RI measurement with high sensitivity, linearity, and resolution. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.

Despite years of utilizing the transferrin receptor 1 (TfR1) to transport large biomolecules into the brain, there is no consensus on how to optimally measure affinity to it. The aim of this study was to compare different methods for measuring the affinities of anti-TfR1 antibodies. Antibodies 15G11, OX26 and 8D3 are known to successfully carry large biologics across the blood-brain barrier in humans, rats, and mice, respectively. The affinity to their respective species of TfR1 was measured with different surface plasmon resonance setups in Biacore and an on-cell assay. When the antibody was captured and TfR1 was the analyte, the dissociation in Biacore was very slow. The dissociation was faster when the antibody was the analyte and TfR1 was the ligand. The Biacore setup with capture of N-terminal FLAG-tag TfR1 yielded the most similar apparent affinities as the cell assay. In conclusion, it is important to evaluate assay parameters including assay orientation, surface capture method, and antibody format when comparing binding kinetics for TfR1 antibodies. Although it seems possible to determine relative affinities of TfR1 antibodies using the methods described here, both the FLAG-tag TfR1 capture setup and cell assays likely yield apparent affinities that are most translatable in vivo.

HIV-1 antibodies targeting the carboxy-terminal area of the membrane-proximal external region (ctMPER) are close to exerting viral pan-neutralization. Here, we reconstituted the ctMPER epitope as the N-terminal extremity of the Env glycoprotein transmembrane domain helix and immobilized it onto biosensor-supported lipid bilayers. We assessed the binding mechanism of anti-MPER antibody 10E8 through Surface Plasmon Resonance, and found, through equilibrium and kinetic binding analyses as a function of bilayer thickness, peptide length, and paratope mutations, that 10E8 engages first with the epitope peptide (encounter), limited by ctMPER helix accessibility at the membrane surface, and then inserts into the lipid bilayer assisted by favorable Fab-membrane interactions (docking). This mechanistic information may help in devising new strategies to develop more efficient MPER-targeting vaccines.

Clofazimine and Arbidol have both been reported to be effective in vitro SARS-CoV-2 fusion inhibitors. Both are promising drugs that have been repurposed for the treatment of COVID-19 and have been used in several previous and ongoing clinical trials. Small-molecule bindings to expressed constructs of the trimeric S2 segment of Spike and the full-length SARS-CoV-2 Spike protein were measured using a Surface Plasmon Resonance (SPR) binding assay. We demonstrate that Clofazimine, Toremifene, Arbidol and its derivatives bind to the S2 segment of the Spike protein. Clofazimine provided the most reliable and highest-quality SPR data for binding with S2 over the conditions explored. A molecular docking approach was used to identify the most favorable binding sites on the S2 segment in the prefusion conformation, highlighting two possible small-molecule binding sites for fusion inhibitors. Results related to molecular docking and modeling of the structure-activity relationship (SAR) of a newly reported series of Clofazimine derivatives support the proposed Clofazimine binding site on the S2 segment. When the proposed Clofazimine binding site is superimposed with other experimentally determined coronavirus structures in structure-sequence alignments, the changes in sequence and structure may rationalize the broad-spectrum antiviral activity of Clofazimine in closely related coronaviruses such as SARS-CoV, MERS, hCoV-229E, and hCoV-OC43.

Submission received: 18 January 2024 / Revised: 30 January 2024 / Accepted: 1 February 2024 / Published: 5 February 2024, Customized metasurfaces allow for controlling optical responses in photonic and optoelectronic devices over a broad band. For sensing applications, the spectral response of an optical device can be narrowed to a few nanometers, which enhances its capabilities to detect environmental changes that shift the spectral transmission or reflection. These nanophotonic elements are key for the new generation of plasmonic optical sensors with custom responses and custom modes of operation. In our design, the metallic top electrode of a hydrogenated amorphous silicon thin-film solar cell is combined with a metasurface fabricated as a hybrid dielectric multilayer grating. This arrangement generates a plasmonic resonance on top of the active layer of the cell, which enhances the optoelectronic response of the system over a very narrow spectral band. Then, the solar cell becomes a sensor with a response that is highly dependent on the optical properties of the medium on top of it. The maximum sensitivity and figure of merit (FOM) are SB = 36,707 (mA/W)/RIU and ≈167 RIU−1, respectively, for the 560 nm wavelength using TE polarization. The optical response and the high sensing performance of this device make it suitable for detecting very tiny changes in gas media. This is of great importance for monitoring air quality and thecomposition of gases in closed atmospheres., Ministerio de Economía y Competitividad de España, Comunidad de Madrid (España), Depto. de Óptica, Sección Deptal. de Óptica (Óptica), Fac. de Óptica y Optometría, TRUE, pub

Graphene-based materials have been increasingly incorporated to optical fiber plasmonic sensors due to the peculiar physical and chemical properties of these materials (hardness and flexibility, high electrical and thermal conductivity, and very good adsorption for many substances, etc.). In this paper, we theoretically and experimentally showed how the addition of graphene oxide (GO) to optical fiber refractometers permits the development of surface plasmon resonance (SPR) sensors with very good characteristics. We used doubly deposited uniform-waist tapered optical fibers (DLUWTs) as supporting structures because of their already proven good performance. The presence of GO as an effective third layer is useful to tune the wavelength of the resonances. In addition, the sensitivity was improved. We depict the procedures for the production of the devices and characterize the GO+DLUWTs produced in this way. We also showed how the experimental results are in agreement with the theoretical predictions and used these to estimate the thickness of deposited GO. Finally, we compared the performance of our sensors with other ones that have been recently reported, showing that our results are among the best reported. Using GO as the medium in contact with the analyte, in addition to the good overall performance of devices, permit consideration of this option as an interesting possibility for the future development of SPR-based fiber sensors., Universidad Complutense de Madrid (España), Banco Santander (España), Sección Deptal. de Óptica (Óptica), Depto. de Óptica, Fac. de Óptica y Optometría, Fac. de Ciencias Físicas, TRUE, pub

Dopamine (DA) plays a vital role in the brain and central nervous system. Therefore, there is a great need to develop a sensitive and selective sensor to monitor and determine DA concentrations for diagnostic purposes and diseases prevention. Up to now, employing surface plasmon resonance (SPR) sensors in DA determination is very limited, and its utilization to detect analytes with low concentrations still needs sensitivity enhancement. In this work, the SPR gold chips were modified using carbon quantum dots (CQDs), graphene quantum dots (GQDs), graphene oxide (GO), chitosan (CS), (CS-CQDs), and (CS-GQDs) thin films. The sensor performance for all layers was analyzed in terms of two aspects, sensitivity and accuracy. The surface morphology and roughness of all films were analyzed using AFM, and the existence of the functional groups in the samples was confirmed using FTIR spectroscopy. Experimental data were fitted to theoretical data formula to characterize the optical properties and thickness of the films. SPR sensor showed sensitivity of 0.138°/pM, 0.332°/nM, 0.215°/pM, 0.195°/nM, 0.169°/pM, and 0.195°/fM using Au/CQDs, Au/GQDs, Au/GO, Au/CS, Au/CS-CQDs, and Au/CS-GQDs bilayer films, respectively. The changes in the spectral bands and peaks intensity of FTIR spectra for all sensing films following DA injection verified DA binding to the sensor surface. AFM analysis showed that the surface morphology and roughness of all films changed as well. The thickness changed by 4.42, 2.59, 2.53, 1.25, 1.63, and 2.28 nm for CQDs, GQDs, GO, CS, CS-CQDs, CS-GQDs layers, respectively. By comparing the performance of all sensor films, SPR sensor based on Au/CS-GQDs exhibited excellent performance with ultra-sensitivity 0.195°/fM, lowest detection limit down to 1 fM of DA was obtained for the first time, RI sensitivity of 10.186°/RIU and the strongest binding affinity of 0.430 × 1015 M-1. Interestingly, Au/GO based sensor exhibited competitive performance to Au/CS-GQDs based sens

Glass substrates, with their ultrasonic and enhanced Raman signals, are in high demand for medical applications. Over the past two decades, surface plasmon resonance biosensor technology has made tremendous advancements. However, there are multifaceted gaps in the current state-of-the-art that need to be addressed, with sensitivity being one of the most critical concerns. The poor sensitivity is primarily caused by weak Raman scattering of light. Only a small number of incident photons, around 10-12, scatter, making Raman characterization unrealistic without a significant signal improvement. This fundamental problem with Raman scattering observation needs to be addressed. Several strategies have been proposed to improve the sensitivity of the biosensor, utilizing metal nanoparticles, nanoholes, metallic nano slits and colloidal gold nanoparticles in a buffered solution. However, achieving precise control over the geometry and optical properties of nanostructures remains challenging. Limited research has focused on enhancing the properties of the sensor platform, with only a few studies utilizing Er2O3 doping on the zinc borosilicate glass substrate, along with a thin layer of gold as a platform and a layer of silver nanoparticles. Therefore, this research suggests altering the elastic properties and Raman shifting in the surface plasmon resonance results of the glass substrate, which can be beneficial for optical biosensor applications. The objective of this study is to examine the impact of doping Er2O3 in the B2O3-ZnOSiO2 glass system using the melt quenching technique with specific raw materials. The focus is on characterizing the physical, structural, elastic and optical properties, as well as the SPR results of the glass substrate. The materials' amorphous and glassy characteristics were verified using XRD and FTIR techniques. The ultrasonic method was employed to determine the glass’s ultrasonic longitudinal and shear velocities at a 5 MHz resounding frequency

Electrochemical second harmonic generation (ESHG) has been applied as a probe of the slow dynamics in the electric double layer (EDL) at the ionic liquid (IL)/Au interface. When the electrode potential was stepped, the SHG signal from the interface was relaxed on the time scale longer than tens of seconds, which is distinctively slower than the RC time constant of the cell. This ultraslow relaxation in ESHG was quantitatively analyzed and discussed for several ILs, revealing that the ultraslow relaxation itself is a common phenomenon for the EDL in the ILs studied but the asymmetry of the time constants to the potential-step directions depends on the IL ions, which is likely to reflect the structure ordering of the interfacial ionic layer in the EDL depending on both ILs and the potential. The EDL structure in equilibrium has also been investigated via SHG measurements with a potential scan at a sufficiently slow rate; the potential dependence of the SHG signal was found to deviate from a simple parabolic one, reflecting the camel-shaped static differential capacitance for the EDL in ILs.

In recent years, nanoparticles have emerged as an important player in a broad range of applications, especially thanks to recent advances in their synthesis. The silver and copper nanoparticles are often used due to their antibacterial and fungicidal activities, and this article presents the results of the nanoparticle synthesis using electrical glow discharge generated directly in a volume of their salt solutions. Therefore, there is no influence of air (i.e. reactive nitrogen species) as it is usual in other commonly used approaches. Nanoparticles were prepared under various experimental conditions, and they were characterized by ultraviolet/visible spectrometry, dynamic light scattering, X-ray photoelectron spectroscopy, and high-resolution scanning electron microscopy. Particles were produced without any surfactant or stabilizing agent, and some of them showed higher resistance against agglomeration during their short-term (days) storage. The nanoparticle formation mechanism was confirmed by the fast camera imaging. Thus, the developed approach can be applied for simple environmentally friendly nanoparticle production for various applications.

In recent years, nanoparticles have emerged as an important player in a broad range of applications, especially thanks to recent advances in their synthesis. The silver and copper nanoparticles are often used due to their antibacterial and fungicidal activities, and this article presents the results of the nanoparticle synthesis using electrical glow discharge generated directly in a volume of their salt solutions. Therefore, there is no influence of air (i.e. reactive nitrogen species) as it is usual in other commonly used approaches. Nanoparticles were prepared under various experimental conditions, and they were characterized by ultraviolet/visible spectrometry, dynamic light scattering, X-ray photoelectron spectroscopy, and high-resolution scanning electron microscopy. Particles were produced without any surfactant or stabilizing agent, and some of them showed higher resistance against agglomeration during their short-term (days) storage. The nanoparticle formation mechanism was confirmed by the fast camera imaging. Thus, the developed approach can be applied for simple environmentally friendly nanoparticle production for various applications.

In recent years, nanoparticles have emerged as an important player in a broad range of applications, especially thanks to recent advances in their synthesis. The silver and copper nanoparticles are often used due to their antibacterial and fungicidal activities, and this article presents the results of the nanoparticle synthesis using electrical glow discharge generated directly in a volume of their salt solutions. Therefore, there is no influence of air (i.e. reactive nitrogen species) as it is usual in other commonly used approaches. Nanoparticles were prepared under various experimental conditions, and they were characterized by ultraviolet/visible spectrometry, dynamic light scattering, X-ray photoelectron spectroscopy, and high-resolution scanning electron microscopy. Particles were produced without any surfactant or stabilizing agent, and some of them showed higher resistance against agglomeration during their short-term (days) storage. The nanoparticle formation mechanism was confirmed by the fast camera imaging. Thus, the developed approach can be applied for simple environmentally friendly nanoparticle production for various applications.

The correct detection and quantification of pollutants in water is key to regulating their presence in the environment. Biosensors offer several advantages, such as minimal sample preparation, short measurement times, high specificity and sensibility and low detection limits. The purpose of this review is to explore the different types of optical biosensors, focusing on their biological elements and their principle of operation, as well as recent applications in the detection of pollutants in water. According to our literature review, 33% of the publications used fluorescence-based biosensors, followed by surface plasmon resonance (SPR) with 28%. So far, SPR biosensors have achieved the best results in terms of detection limits. Although less common (22%), interferometers and resonators (4%) are also highly promising due to the low detection limits that can be reached using these techniques. In terms of biological recognition elements, 43% of the published works focused on antibodies due to their high affinity and stability, although they could be replaced with molecularly imprinted polymers. This review offers a unique compilation of the most recent work in the specific area of optical biosensing for water monitoring, focusing on both the biological element and the transducer used, as well as the type of target contaminant. Recent technological advances are discussed.

Recent advancements in life science research have greatly improved our understanding of various intricate biological systems, some of which are affiliated with complex diseases. While a great deal of progress has been made towards the comprehension of relevant biophysical interactions, many remain poorly understood. This is especially true for protein interactions involving the cellular membrane. Of the analytical strategies developed for investigating molecular interactions, surface plasmon resonance (SPR) provides marked technical advantages and has become a cornerstone for these studies. However, the SPR method is still facing challenges, from both technical aspects and investigation of diseases, which are the focus of this Dissertation. SPR is susceptible to misidentification in biological matrices, due to cross-reactive and nonspecific interactions. The lack of reliable curved biomimetic membrane platforms has limited the investigation on various disease related protein interactions. The presented Dissertation aims to provide solutions to these challenges through developing novel biomimetic membrane platforms, robust post data acquisitions analysis strategies, and antifouling protocols. Chapter 2 showcases the development of a self-assembled pseudo-myelin sheath microarray. The platform and developed antifouling protocol were shown to be capable of detecting three multiple sclerosis (MS) specific anti-ganglioside antibodies in 10 % serum. Chapter 3 expands and improves upon the platform presented in Chapter 2. The MS specific antibodies were detected at disease relevant concentrations, 3 ng/mL to 25 ng/mL, in undiluted human serum. Machine learning algorithms were applied to facilitate the differentiation and identification of the highly cross reactive analyte-antigen interactions in a clinical setting. In Chapter 4, the characterization and development of a tunable curved membrane mimicking platform is presented. Through the use of statistical analysis, simula

Surface plasmon resonance (SPR) is the collective oscillation of frequency-matched free-space photons and surface electrons at a metal/dielectric interface. Their inherent sensitivity to refractive index changes and ability to couple with exciton species and enhance light-matter interaction make them ideal candidates for low-concentration analyte detection compared to conventional biosensors. The use of metal nanostructures and nanomaterials to excite SPR represents the current state-of-the-art. However, the challenges associated with repeatable synthesis of uniform nanomaterials, complex nanostructure fabrication, low SPR generation efficiency and limited understanding of the mechanism of plasmon-exciton coupling for signal amplification have motivated the search for alternative architectures and procedures. The uniform and repeatable gold nanoslit (NS) and nanoledge (NL) array architectures offers a promising route towards addressing the above issues, and hence this research attempts to take advantage of these platforms to achieve efficient SPR generation and exciton coupling for biosensing applications. The overarching scope of this dissertation extends to the design, fabrication, and optimization of metal NS and NL structures for SPR generation and sensing applications. Emphasis is placed on investigating the mechanism of optical signal enhancement arising from plasmon-exciton coupling (PEC) with particular focus on (a) exploring the role of geometry and size of the nanostructures (b) examining the influence of SPR spectral mode overlap with exciton’s absorption and/or emission energies on the overall optical signal in a NS or NL system, and (c) investigating the analytical sensitivity and signal transduction of the PEC system to biomolecular interactions. The nanoimprinting technique based on soft lithography for NS fabrication, which is used in this work for NS array fabrication, required addressing a critical issue, namely PDMS diffusion into nanoscale patter

In recent years, nanoparticles have emerged as an important player in a broad range of applications, especially thanks to recent advances in their synthesis. The silver and copper nanoparticles are often used due to their antibacterial and fungicidal activities, and this article presents the results of the nanoparticle synthesis using electrical glow discharge generated directly in a volume of their salt solutions. Therefore, there is no influence of air (i.e. reactive nitrogen species) as it is usual in other commonly used approaches. Nanoparticles were prepared under various experimental conditions, and they were characterized by ultraviolet/visible spectrometry, dynamic light scattering, X-ray photoelectron spectroscopy, and high-resolution scanning electron microscopy. Particles were produced without any surfactant or stabilizing agent, and some of them showed higher resistance against agglomeration during their short-term (days) storage. The nanoparticle formation mechanism was confirmed by the fast camera imaging. Thus, the developed approach can be applied for simple environmentally friendly nanoparticle production for various applications., IV posledních letech je pozorován prudký nárůst aplikací nanočástic, a to zejména díky progresu v jejich přípravě. Stříbrné a měděné nanočástice jsou často užívány pro svou antimikrobiální a antimykotickou aktivitu. Článek prezentuje syntézu těchto annočástic pomocí plazmatu generovaného přímo ve vodném roztoku anorganických solí, tedy bez přístupu vzduchu. Proces přípravy probíhal za různých podmínek. K charakterizaci nanočástic bylo využito UVS-VIS spektrometrie, dynamického rozptylu světla, rentgenovské fotoelektronové spektormetrie avysoce rozlišující skenovací elektronové mikroskopie. Částice byly připravovány bez použití surfaktantů nebo jiných stabilizačních činidel, a některé z nich nevykazovaly po řadu dní aglomerační tendence. Mechanismus vzniku nanočástic byl potvrzen s využitím snímání vysokorychlostní kamerou. Použitý přístup představuje efektivní a přírodě přátelský postup přípravy kovových nanočástic.

©2011 Elsevier Ltd. This work has been partially supported by Spanish Ministry of Science research projects SPRINT (CTQ2009-10550) and MAX-MART (CTQ2009-14565-C03-01), and the Community of Madrid research grants FACTOTEM II (S2009/ESP-1781) and FUTURSEN (CM-S-505/AMB/0374) as well as the European Social Fund and the European Fund for Regional Development., We present the results of a chemical attack on the optical fiber surface previous to the deposition of the double layer (metal plus dielectric) in Double-layer uniform-waist tapered fibers (DLUWTs) used for the development of SPR sensors. It is shown how this simple chemical treatment increases the roughness of the surface and permits improvement of the stability of the deposits and the general performance of the sensors. The obtained devices are robust and very compact, their sensitivity is good and repeatability of the measurements is remarkably increased. The procedure can be useful for any fiber-optic sensor., Comunidad de Madrid, Ministerio de Ciencia e Innovación (MICINN), European Social Fund, European Fund for Regional Development, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2009 Elsevier B.V. This work has been partially supported by Spanish Government research project NESTOR, ref. CTM2004-03899; Comunidad de Madrid research project FUTURSEN, ref. S-0505/AMB-0374 and by Proyecto de Investigación Santander/Complutense, ref. PR34/07-15886. This work was supported partially by the Portuguese Government – Fundação para a Ciência e Tecnologia (FCT) through the grant SFRH/BD/30086/2006. N. Díaz-Herrera is thankful for the grant within the program ‘Becas Internacionales Universidad Complutense/Empresa Flores Valles 2008’., In this work a new configuration of a refractometric sensor for aqueous solutions based on the combination of surface plasmon resonance (SPR) with fibre Bragg gratings (FBG) is presented. Two FBGs are selected having reflection maxima in each side of the plasmon resonance peak. These FBGs enable a different processing scheme for the information provided by the SPR transducer. This improved interrogation method increases the sensitivity and resolution of the sensor compared with those obtained with the usual method of tracking the spectral transmittance minimum and makes the system performance independent of optical source power fluctuations. The experimental results obtained with a double-layer uniform-waist tapered fibre show the feasibility of this approach and its applicability in SPR-based biosensors that must face very exigent measuring conditions., Spanish Government, Comunidad de Madrid, Proyecto de Investigación Santander/Complutense, Portuguese Government – Fundação para a Ciência e Tecnologia (FCT), Universidad Complutense de Madrid, Flores Valles, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2013 Elsevier B.V. This work has been partially supported by Spanish Ministry of Science research projects SPRINT (reference CTQ2009-10550), by the Community of Madrid project FACTOTEM II (reference S2009/ESP-1781) and by the European Social Fund and the European Fund for Regional Development., Doubly deposited uniform-waist tapered optical fibers (DLUWTs) have shown their versatility and good performance as basis for surface plasmon resonance (SPR) sensors for a variety of wavelength ranges. In this work we experimentally show how these devices can be employed to extend the technology of SPR fiber sensors to the visible region, down to about 530 nm, with remarkable results in terms of sensitivity, plasmon definition and the availability of multiple plasmon resonances for each configuration. In this way, DLUWTs can be used to cover a range of more than 1000 nm for aqueous media only by changing the thickness of the deposits. Also, it is shown how these results can be used with the so-called absorption method to make selective the response of the sensors and a study is made on the influence of the taper waist in the performance of the devices. The number of SPR fiber sensors working in the visible region, of great interest in biological research, that have been depicted in the literature is very small, and the sensors that we present here notably improve their performance., Comunidad de Madrid, Ministerio de Ciencia e Innovación (MICINN), European Social Fund, European Fund for Regional Development, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

Colloidal copper phosphide (Cu3−xP) nanocrystals are attractive electronic materials due to their ability to support excess delocalized holes, with both synthesis and dynamic redox modulation allowing tuning of localized surface plasmon resonance (LSPR) absorption in the near-IR. This dissertation presents developments in the colloidal syntheses and post-synthetic redox chemistries of high-quality Cu3−xP nanoplatelets with the attainment of tunable nanocrystallite lateral sizes, LSPR energies, compositions, and optoelectronic properties. A one-pot, colloidal synthesis of Cu3−xP nanoplatelets with copper halide salt and aminophosphine in the presence of oleylamine is presented in Chapter 2. The reactivity of an in situ copper-phosphorus precursor is modulated by varying precursor composition and coordinating solvent ratio to tune nanocrystal lateral size. Oleylamine-to-aminophosphine molar ratio is found to alter particle nucleation activity and access atom-efficient size tuning. By modulating precursor reactivity, the syntheses presented in Chapter 2 are used to access nanocrystals with lateral sizes of 6.1–23 nm and LSPR energies of 709–861 meV. The low polydispersity, size- and LSPR-tunability and colloidal stability make aminophosphine-synthesized Cu3−xP nanocrystals promising candidates for investigations into factors governing their LSPR energy, around which the findings of the subsequent chapter are based. Three copper-coupled redox chemistries are presented in Chapter 3 which allow post-synthetic modulation of the delocalized hole concentrations and corresponding LSPR absorption in colloidal Cu3−xP nanocrystals. Changes in the structural, optical, and compositional properties are evaluated by powder X-ray diffraction, electronic absorption spectroscopy, 31P magic-angle spinning solid-state nuclear magnetic resonance spectroscopy and elemental analysis. The redox chemistries are shown to access nanocrystals with LSPR energies of 660–890 meV, a larger range tha

Plasmonic nanoparticleswith surface plasmon resonance (SPR) andscattering response dependent on their geometry and surrounding environmentare predestinated to be used as optical probes for sensing and imaging.Optical microscopy is capable of observing nanoparticles in variousmedia, but their geometry remains hidden below the diffraction limit.Here, a wide-field optical imaging technique is demonstrated, restoringthe aspect ratio and orientation of individual nanoparticles via thepolarization anisotropy (PA) measurement of the scattered light. ThePA is mapped into a single nanoparticle image, formed by decomposingthe scattered light into longitudinal and transverse SPR modes andmanipulating their angular momentum. The wide-field images providethe aspect ratio and orientation of many deposited nanoparticles allowingtheir assessment in heterogeneous suspensions or time-resolved measurements.In calibration experiments, orientation measurement accuracy and excellentsensitivity to nanoparticles with specific aspect ratios are demonstrated.Subsequently, the method is deployed in the automatic shape-dependentcategorization of hundreds of nanoparticles in a heterogeneous mixture.The single-shot capability is demonstrated in the time-resolved imagingof the electrophoretic deposition process.

In recent years, nanoparticles have emerged as an important player in a broad range of applications, especially thanks to recent advances in their synthesis. The silver and copper nanoparticles are often used due to their antibacterial and fungicidal activities, and this article presents the results of the nanoparticle synthesis using electrical glow discharge generated directly in a volume of their salt solutions. Therefore, there is no influence of air (i.e. reactive nitrogen species) as it is usual in other commonly used approaches. Nanoparticles were prepared under various experimental conditions, and they were characterized by ultraviolet/visible spectrometry, dynamic light scattering, X-ray photoelectron spectroscopy, and high-resolution scanning electron microscopy. Particles were produced without any surfactant or stabilizing agent, and some of them showed higher resistance against agglomeration during their short-term (days) storage. The nanoparticle formation mechanism was confirmed by the fast camera imaging. Thus, the developed approach can be applied for simple environmentally friendly nanoparticle production for various applications., IV posledních letech je pozorován prudký nárůst aplikací nanočástic, a to zejména díky progresu v jejich přípravě. Stříbrné a měděné nanočástice jsou často užívány pro svou antimikrobiální a antimykotickou aktivitu. Článek prezentuje syntézu těchto annočástic pomocí plazmatu generovaného přímo ve vodném roztoku anorganických solí, tedy bez přístupu vzduchu. Proces přípravy probíhal za různých podmínek. K charakterizaci nanočástic bylo využito UVS-VIS spektrometrie, dynamického rozptylu světla, rentgenovské fotoelektronové spektormetrie avysoce rozlišující skenovací elektronové mikroskopie. Částice byly připravovány bez použití surfaktantů nebo jiných stabilizačních činidel, a některé z nich nevykazovaly po řadu dní aglomerační tendence. Mechanismus vzniku nanočástic byl potvrzen s využitím snímání vysokorychlostní kamerou. Použitý přístup představuje efektivní a přírodě přátelský postup přípravy kovových nanočástic.

The continuous flow reverse water gas shift (rWGS) process was efficiently catalyzed by a plasmonic Au/TiO2 nanocatalyst using sunlight as sole and sustainable energy source. The influence of the catalyst bed thickness on the CO production rate was studied, and three different catalytic regimes were identified as direct plasmon catalysis (DPC), shielded plasmon catalysis (SPC) and unused plasmon catalysis (UPC). The CO2 : H2 ratio was optimized to 4 : 1 and a maximum CO production rate of 7420 mmol ⋅ m−2 ⋅ h−1 was achieved under mild reaction conditions (p=3.5 bar, no external heating, Ee=14.0 kW ⋅ m−2), corresponding to an aparent quantum efficiency of 4.15%. The stability of the Au/TiO2 catalyst was studied for 110 h continuous operation, maintaining more than 82% of the initial CO production rate. On/off experiments mimicking discontinuous sunlight powered processing furthermore showed that the Au/TiO2 catalyst was stable for 8 consecutive runs.

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.

[Abstract] Plasmonic nanoparticles (NPs) exhibit extraordinary optical properties that stem from their ability to sustain localized surface plasmon resonances. These resonances can be finely tuned by carefully controlling the morphology of the particles, allowing for optimization across a diverse range of applications. Recently, preparing chiral morphologies for these NPs has received considerable attention because it may provide important advantages in fields such as biomedicine. Thus, this undergraduate project focuses on the preparation of a novel type of plasmonic chiral NPs, i.e., chiral gold nanostars. This TFG has been divided into three parts. The first part focuses on synthesizing and characterizing achiral gold nanostars, utilizing UV-Vis spectroscopy and TEM to analyze their morphological and optical properties. The second part involved attempting to introduce chirality into the gold nanostars by replacing the previous surfactant with a chiral one. Unfortunately, the desired results were not achieved. Consequently, in the third part, a new chiral surfactant was synthesized, although due to the project's limited duration, the verification of its effect on achieving chirality in the gold nanostars could not be completed. The chiral surfactant was characterized using 1H-NMR, 13C-NMR spectroscopy, and MS spectrometry., {Resumo] As nanopartículas plasmónicas (NPs) presentan propiedades ópticas extraordinarias que se derivan da súa capacidade para manter as resonancias plasmónicas de superficie localizadas. Estas resonancias pódense afinar controlando coidadosamente a morfoloxía das partículas, permitindo a optimización nunha ampla gama de aplicacións. Recentemente, a preparación de morfoloxías quirais para estes NP recibiu unha atención considerable porque pode proporcionar importantes vantaxes en campos como a biomedicina. Polo tanto, este proxecto de pregrado céntrase na preparación dun novo tipo de NPs quirais plasmónicas, as nanoestrelas quirais de ouro. Este TFG dividiuse en tres partes. A primeira parte céntrase na síntese e caracterización de nanoestrelas aquirales de ouro, utilizando espectroscopia UV-Vis e TEM para analizar as súas propiedades morfolóxicas e ópticas. A segunda parte consistiu en intentar introducir quiralidade nas nanoestrelas de ouro substituíndo o tensioactivo anterior por outro quiral. Desafortunadamente, non se conseguiron os resultados desexados. En consecuencia, na terceira parte, sintetizouse un novo surfactante quiral, aínda que debido á limitada duración do proxecto non se puido completar a verificación do seu efecto na consecución da quiralidade nas nanoestrelas de ouro. O surfactante quiral caracterizouse por espectroscopia 1H-RMN, 13C-RMN e espectrometría MS., [Resumen] Las nanopartículas plasmónicas (NPs) exhiben propiedades ópticas extraordinarias que se derivan de su capacidad para sostener resonancias de plasmones superficiales localizadas. Estas resonancias se pueden ajustar con precisión controlando cuidadosamente la morfología de las partículas, lo que permite la optimización en una amplia gama de aplicaciones. Recientemente, la preparación de morfologías quirales para estas NPs ha recibido una atención considerable porque puede proporcionar importantes ventajas en campos como la biomedicina. Por lo tanto, este proyecto de pregrado se centra en la preparación de un nuevo tipo de NP quirales plasmónicas, las nanoestrellas de oro quirales. Este TFG se ha dividido en tres partes. La primera parte se centra en sintetizar y caracterizar nanoestrellas de oro aquirales, utilizando espectroscopia UV-Vis y TEM para analizar sus propiedades morfológicas y ópticas. La segunda parte consistió en intentar introducir quiralidad en las nanoestrellas de oro reemplazando el surfactante anterior por uno quiral. Desafortunadamente, no se lograron los resultados deseados. En consecuencia, en la tercera parte, se sintetizó un nuevo surfactante quiral, aunque debido a la duración limitada del proyecto, no se pudo completar la verificación de su efecto para lograr la quiralidad en las nanoestrellas de oro. El tensioactivo quiral se caracterizó mediante espectroscopia 1H-NMR, 13C-NMR y espectrometría MS.

Detecting, identifying, and characterizing molecules and structures as the substance of life are essential steps toward unveiling their role as a sole entity or more commonly as a part of a larger molecular assembly for specific biological functionalities. Next, it is of pivotal importance to translate the acquired knowledge of molecular structures and their activity to a more comprehensive understanding of the biological process, such as the biochemical foundations of diseases or metabolic disorders. The aim and ultimate outcomes of this thesis were to address these two aspects by offering new analytical strategies such as focusing on the molecular structure assessment of small molecules, including drug metabolites and potential biomarkers, and drug targets. Addressing challenges encountered in protein characterization and protein interactions studies. And lastly, taking a step forward and analyzing a dynamic chemical reaction in an online fashion by mass, tandem mass, and ion mobility spectrometry.

Monoclonal antibody (mAb) therapy is one of the most promising immunotherapies that have shown the potential to prevent or neutralize the effects of COVID-19 in patients at very early stages, with a few formulations recently approved by the European and American medicine agencies. However, a main bottleneck for their general implementation resides in the time-consuming, laborious, and highly-specialized techniques employed for the manufacturing and assessing of these therapies, excessively increasing their prices and delaying their administration to the patients. We propose a biomimetic nanoplasmonic biosensor as a novel analytical technique for the screening and evaluation of COVID-19 mAb therapies in a simpler, faster, and reliable manner. By creating an artificial cell membrane on the plasmonic sensor surface, our label-free sensing approach enables real-time monitoring of virus-cell interactions as well as direct analysis of antibody blocking effects in only 15 min assay time. We have achieved detection limits in the 102 TCID50/mL range for the study of SARS-CoV-2 viruses, which allows to perform neutralization assays by only employing a low-volume sample with common viral loads. We have demonstrated the accuracy of the biosensor for the evaluation of two different neutralizing antibodies targeting both Delta and Omicron variants of SARS-CoV-2, with half maximal inhibitory concentrations (IC50) determined in the ng/mL range. Our user-friendly and reliable technology could be employed in biomedical and pharmaceutical laboratories to accelerate, cheapen, and simplify the development of effective immunotherapies for COVID-19 and other serious infectious diseases or cancer.

Optical biosensors based on plasmonic sensing schemes combine high sensitivity and selectivity with label-free detection. However, the use of bulky optical components is still hampering the possibility of obtaining miniaturized systems required for analysis in real settings. Here, a fully miniaturized optical biosensor prototype based on plasmonic detection is demonstrated, which enables fast and multiplex sensing of analytes with high- and low molecular weight (80 000 and 582 Da) as quality and safety parameters for milk: a protein (lactoferrin) and an antibiotic (streptomycin). The optical sensor is based on the smart integration of: i) miniaturized organic optoelectronic devices used as light-emitting and light-sensing elements and ii) a functionalized nanostructured plasmonic grating for highly sensitive and specific localized surface plasmon resonance (SPR) detection. The sensor provides quantitative and linear response reaching a limit of detection of 10−4 refractive index units once it is calibrated by standard solutions. Analyte-specific and rapid (15 min long) immunoassay-based detection is demonstrated for both targets. By using a custom algorithm based on principal-component analysis, a linear dose–response curve is constructed which correlates with a limit of detection (LOD) as low as 3.7 µg mL−1 for lactoferrin, thus assessing that the miniaturized optical biosensor is well-aligned with the chosen reference benchtop SPR method.