Surface Plasmon Resonance Chip Research Articles

Surface Plasmon Resonance in the Development of TGF-β Activators for Cosmeceutical Use

Research on new compounds that can improve the skin's condition is no longer focused exclusively on drugs, but is also adequate for cosmeceuticals – cosmetic products with thoroughly tested and scientifically proven biological activity. One of the most important stimulators of collagen biosynthesis is the so-called Transforming Growth Factor-β (TGF-β). Measuring the activation of latent TGF-β and quantification of its efficacy using the Surface Plasmon Resonance (SPR) technique is a great alternative to the currently used Enzyme-linked Immunosorbent Assay (ELISA) method. In this article, the complex process of TGF-β activation and the methods of its quantification are described. SPR was investigated as a relevant method for the TGF-β activity detection. Optimization of measurement conditions is presented, comparing results of antibody immobilization efficacy in different buffers. Two types of antibodies were immobilized onto the SPR chip, and after choosing one of them the selectivity of capturing between active and inactive TGF-β was confirmed. SPR is discussed as a technique with great potential in cosmeceutical design, in comparison to currently applied quantification methods.

Discovery of (−)-epigallocatechin gallate, a novel olfactory receptor 2AT4 agonist that regulates proliferation and apoptosis in leukemia cells

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.

A portable surface plasmon resonance (SPR) sensor for the detection of immunoglobulin A in plasma.

A life-threatening anaphylactic shock can occur if a patient with undiagnosed immunoglobulin A (IgA) deficiency (i.e., IgA levels <500 ng/mL) receives IgA-containing blood, hence the need for a rapid, point-of-care (POC) method for IgA deficiency screening. Enzyme-linked immunosorbent assay (ELISA) is routinely used to detect IgA, but this method requires trained specialists and ≥24 h to obtain a result. We developed a surface plasmon resonance (SPR)-based protocol to identify IgA-deficient patients or donors within 1 h. The SPR sensor relies on the detection of IgAs captured by primary antibodies adsorbed on the SPR chip and quantified with secondary antibodies. The sensor was calibrated from 0 to 2000 ng/mL in buffer, IgA-depleted human serum, and plasma samples from IgA-deficient individuals. A critical concentration of 500 ng/mL was set for IgA deficiency. The optimized sensor was then tested on eight plasma samples with known IgA status (determined by ELISA), including five with IgA deficiency and three with normal IgA levels. The limit of detection was estimated at 30 ng/mL in buffer and 400 ng/mL in diluted plasma. The results obtained fully agreed with ELISA among the eight plasma samples tested. The protocol distinguished IgA-deficient from normal samples, even for samples with an IgA concentration closer to critical concentration. In conclusion, we developed a reliable POC assay for the quantification of IgA in plasma. This test may permit POC testing at blood drives and centralized centers to maintain reserves of IgA-deficient blood and in-hospital testing of blood recipients.

Molybdenum Disulfide‐based Lossy Mode Resonance Sensors: Uncovering Wider Dynamic Range and High Sensitivity Through Computational Approaches

AbstractUntil now, Surface Plasmon Resonance (SPR) biosensors still rely on gold as their transducer element, and this makes cheap analytical devices difficult to achieve. On the other hand, lossy mode resonance (LMR) sensors offer transducers with more alternative materials due to their flexibility, which can be excited in p‐ and s‐polarized light. In this research it is carried out a numerical investigation using the transfer matrix method on LMR sensor composed of molybdenum disulfide (MoS2) as lossy layer and Cytop as matching layer. The reflectance curves for different thicknesses of MoS2 and Cytop are numerically investigated. The results obtained show that the chip consisting of 250 nm Cytop and 4 layers of MoS2 has a penetration depth 3 times higher than conventional SPR chips. If sensors with two types of polarization are compared, sensors with s‐polarized light have shown higher sensitivity reaching 72.13°/RIU with a wider dynamic range starting from a refractive index of 1.331 to 1.401. In this refractive index range, this sensor has displayed good signal stability where the reduction in resonance dip depth is only ≈6%. These computational results make the proposed structure very promising to be applied in the quantification of biological materials.

Fenpicoxamid-Imprinted Surface Plasmon Resonance (SPR) Sensor Based on Sulfur-Doped Graphitic Carbon Nitride and Its Application to Rice Samples.

This research attempt involved the development and utilization of a newly designed surface plasmon resonance (SPR) sensor which incorporated sulfur-doped graphitic carbon nitride (S-g-C3N4) as the molecular imprinting material. The primary objective was to employ this sensor for the quantitative analysis of Fenpicoxamid (FEN) in rice samples. The synthesis of S-g-C3N4 with excellent purity was achieved using the thermal poly-condensation approach, which adheres to the principles of green chemistry. Afterwards, UV polymerization was utilized to fabricate a surface plasmon resonance (SPR) chip imprinted with FEN, employing S-g-C3N4 as the substrate material. This process involved the inclusion of N,N'-azobisisobutyronitrile (AIBN) as the initiator, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, methacryloylamidoglutamic acid (MAGA) as the monomer, and FEN as the analyte. After successful structural analysis investigations on a surface plasmon resonance (SPR) chip utilizing S-g-C3N4, which was imprinted with FEN, a comprehensive investigation was conducted using spectroscopic, microscopic, and electrochemical techniques. Subsequently, the kinetic analysis applications, namely the determination of the limit of quantification (LOQ) and the limit of detection (LOD), were carried out. For analytical results, the linearity of the FEN-imprinted SPR chip based on S-g-C3N4 was determined as 1.0-10.0 ng L-1 FEN, and LOQ and LOD values were obtained as 1.0 ng L-1 and 0.30 ng L-1, respectively. Finally, the prepared SPR sensor's high selectivity, repeatability, reproducibility, and stability will ensure safe food consumption worldwide.

An Analytical Tooth Model Based on Surface Plasmon Resonance Chips Coated with Hydroxyapatite Used for Investigation of the Acquired Dental Pellicle

One of the main targets in modern dentistry is the prevention of caries. Not only daily nutrition plays an important role, but also the so‐called “pellicle” on the outer surface of teeth, which is mainly formed by saliva proteins. Moreover, numerous bacteria are part of this pellicle, which might cause caries by acidic metabolites. In the here‐presented study, a method for electrophoretic deposition (EPD) of hydroxyapatite (HAP) nanoparticles on gold surfaces, suitable for surface plasmon resonance (SPR) measurements, is developed. An “artificial tooth” is created and loaded by natural saliva in different concentrations (to form a natural pellicle), while the influence of an environment with different pH values has been studied. It could be demonstrated that even slight acid solutions damage the pellicle significantly within seconds, exposing the HAP to acidic degradation, which would lead to caries in the human oral cavities. This model allows to study pellicle formation as well as degradation in real time. As a practical example, the influence of beverages on the pellicle could be demonstrated.

A zearalenone detection based on molecularly imprinted surface plasmon resonance sensor including sulfur-doped g-C3N4/Bi2S3 nanocomposite

In present work, a zearalenone detection based on molecularly imprinted surface plasmon resonance (SPR) sensor including sulfur-doped g-C3N4/Bi2S3 (S-g-C3N4/Bi2S3) nanocomposite was presented for selective determination of zearalenone (ZEA) in rice grain samples. After S-g-C3N4/Bi2S3 nanocomposite was synthesized by calcination method with high purity and in accordance with green chemistry, ZEA imprinted SPR chip based on S-g-C3N4/Bi2S3 was prepared in presence of methacryloylamidoglutamicacid (MAGA) as monomer, ethylene glycol dimethacrylate (EGDMA) as cross linker, N,N′-azobisisobutyronitrile (AIBN) as initiator and ZEA as target molecule by using UV polymerization. Then, the spectroscopic, microscopic and electrochemical methods were used for the characterizations of the nanocomposite and the proposed ZEA imprinted SPR chip based on S-g-C3N4/Bi2S3. The SPR sensor showed a linearity towards ZEA in range of 1.0 – 10.0 ng/L with a detection limit (LOD) of 0.33 ng/L. Thus, the developed sensor's high repeatability, stability, reproducibility and selectivity provided reliable ZEA determination in rice grain samples, ensuring safe food consumption.

Rapid and label-free screening of SARS-CoV-2 virus in the infected human nasopharyngeal swab samples using UiO-66-modified SPR chip

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) virus has become a dangerous human pathogen and caused severe illness that can lead to death. Yet, the standard practical diagnostic tools for detecting the SARS-CoV-2 virus require multi-step assay, including extraction and labeling steps. Thus, a simple and accurate detection tool is incredibly desirable to support on-site screening, preventing its spread. In this work, we developed a portable surface plasmon resonance (SPR) sensor chip modified with metal–organic frameworks (MOF) UiO-66 that serves as an immobilization matrix of single-chain variable fragment (scFv) receptors. Large surface area and good adsorption of UiO-66/scFv-modified surface lead to an improvement of binding capacity towards the protein target of the SARS-CoV-2 receptor binding domain (RBD). We further successfully demonstrated the use of this portable SPR to detect the SARS-CoV-2 virus from patients' nasopharyngeal swab samples. Interestingly, the SPR sensors can directly distinguish the positive and negative patients within 15 minutes on 23 samples, simultaneously, without the need for labeling, and the results are in line with the gold standard PCR tests. In addition, the detection limit of the sensors is 10.085 × 105 virus/mL, which follows the standard of practical screening tools. Therefore, these UiO-66 modified SPR chip sensors offer a rapid, label-free, and low-cost detection of the SARS-CoV-2 virus that can be potentially developed for other infectious diseases.

Investigating membrane-binding properties of lipoxygenases using surface plasmon resonance

Lipoxygenases (LOXs) catalyze the oxidation of polyunsaturated fatty acids and synthesize oxylipin products that drive important cellular signaling processes in plants and animals. While there has been indirect evidence presented for the interaction of mammalian LOXs with membranes, a quantitative study of the molecular details of LOX-membrane interactions is lacking. Here, we mimicked biological membranes using surface plasmon resonance (SPR) sensor chips derivatized with 2-D planar lipophilic anchors (2D LP) to capture liposomes of varying phospholipid compositions that self-assemble into lipid bilayers on the SPR chip. The sensor chip surfaces were then used to investigate the membrane-binding properties of model LOX enzymes. SPR binding assays displayed reproducible and stable liposome capture to the sensor chip surface that allowed for the detailed characterization of LOX-membrane interactions. Our studies demonstrate a calcium-dependence for the membrane binding activities of coral 8R-LOX and human 15-LOX-2. Furthermore, our data confirm the importance of key membrane insertion loop residues in each of these LOX enzymes for membrane binding activity. Experiments utilizing model plant and human LOXs reveal differences in membrane-binding specificities. Our study establishes and validates a robust SPR-based platform using 2D LP sensor chips that allows for the detailed study of LOX-membrane interactions under different experimental conditions, including altered membrane compositions. Collectively, this investigation improves our overall understanding of LOX-membrane interaction properties, and our SPR-based approach holds potential for future use in the development of LOX-based therapeutics.

Ultrasensitive Screening of Endocrine-Disrupting Chemicals Using a Surface Plasmon Resonance Biosensor with Polarization-Compensated Laser Heterodyne Feedback.

Developing an ultrasensitive and reliable device for continuous monitoring of various endocrine-disrupting chemicals (EDCs) is in high demand, yet it remains a significant challenge. Traditional label-free surface plasmon resonance (SPR) sensing relies on the interaction of the surface plasmon wave and the sensing liquid via intensity modulation, endowed with simple structure and easy-to-miniaturization, however suffering from inferior sensitivity and stability. Here, we propose a novel optical structure in which the frequency-shifted light of different polarization returned to the laser cavity to stimulate laser heterodyne feedback interferometry (LHFI), hence amplifying the reflectivity change caused by the refractive index (RI) variations on the gold-coated SPR chip surface, and the s-polarized light could be further used as a reference to compensate for the noise of the LHFI-amplified SPR system, resulting in nearly three orders of magnitude enhancement of the RI sensing resolution (5.9 × 10-8 RIU) compared to the original SPR system (2.0 × 10-5 RIU). To further boost intense signal enhancement, custom-designed gold nanorods (AuNRs), which were optimized by the finite-difference time-domain (FDTD) simulation, were used to generate localized surface plasmon resonance (LSPR). By exploiting the estrogen receptor as the recognition material, estrogenic active chemicals were detected with a 17β-estradiol/L detection limit of 0.004 ng, which is nearly 180-fold lower than that of the system without introducing AuNRs. The developed SPR biosensor is expected to be capable of screening various EDCs with universality by using several nuclear receptors, such as the androgen receptor and thyroid receptor, and will substantially accelerate the assessment of global EDCs.

An Ultrasensitive and Universal Surface Plasmonic Biosensor for Detection of Micropollutants in Aquatic Environments.

Simple yet ultrasensitive and accurate quantification of a variety of analytical targets by virtue of a universal sensing device holds promise to revolutionize environmental monitoring, medical diagnostics, and food safety. Here, we propose a novel optical surface plasmon resonance (SPR) system in which the frequency-shifted light of different polarizations returned the laser cavity to stimulate laser heterodyne feedback interferometry (LHFI), hence amplifying the reflectivity change caused by the refractive index (RI) variations on the gold-coated SPR chip surface. In addition, the s-polarized light was further used as the reference to compensate the noise of the LHFI-amplified SPR system, resulting in nearly 3 orders of magnitude enhancement of RI resolution (5.9 × 10-8 RIU) over the original SPR system (2.0 × 10-5 RIU). By exploiting nucleic acids, antibodies, and receptors as recognition materials, a variety of micropollutants were detected with ultralow detection limits, ranging from a toxic metal ion (Hg2+, 70 ng/L) to a group of commonly occurring biotoxin (microcystins, 3.9 ng microcystin-LR/L) and a class of environmental endocrine disruptors (estrogens, 0.7 ng 17β-estradiol/L). This sensing platform exhibits several distinct characteristics, including dual improvement of sensitivity and stability and common-path optical construction without needing optical alignment, demonstrating a promising avenue toward environmental monitoring.

MoS2-Nanoflower and Nanodiamond Co-Engineered Surface Plasmon Resonance for Biosensing

Surface plasmon resonance (SPR) based sensors play an important role in the biological and medical fields, and improving the sensitivity is a goal that has always been pursued. In this paper, a sensitivity enhancement scheme jointly employing MoS2 nanoflower (MNF) and nanodiamond (ND) to co-engineer the plasmonic surface was proposed and demonstrated. The scheme could be easily implemented via physically depositing MNF and ND overlayers on the gold surface of an SPR chip, and the overlayer could be flexibly adjusted by controlling the deposition times, thus approaching the optimal performance. The bulk RI sensitivity was enhanced from 9682 to 12,219 nm/RIU under the optimal condition that successively deposited MNF and ND 1 and 2 times. The proposed scheme was proved in an IgG immunoassay, where the sensitivity was twice enhanced compared to the traditional bare gold surface. Characterization and simulation results revealed that the improvement arose from the enhanced sensing field and increased antibody loading via the deposited MNF and ND overlayer. At the same time, the versatile surface property of NDs allowed a specifically-functionalized sensor using the standard method compatible with a gold surface. Besides, the application for pseudorabies virus detection in serum solution was also demonstrated.

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

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

Simultaneous measurement of the refractive index and thickness of graphene oxide/gold multilayered structure for potential in dopamine sensing using surface plasmon resonance spectroscopy

Thin films have infinite potential uses in optics and other fields. They must be well suited to meet the requirements of its specific application in terms of thickness, optical properties, morphology and other characteristics. Herein, surface plasmon resonance (SPR) technique was employed to accurately determine the thickness and analyze the optical characteristics of graphene oxide/gold (GO/Au) multilayered structure in contact with the neurotransmitter dopamine (DA). Based on the theoretical fitting of the experimentally recorded SPR dips, n and k values of GO layer were 1.4400 and 0.0250, respectively, prior to DA injection. By increasing DA concentrations, SPR experimental curves were shifted to higher angles continuously. DA Binding to SPR chip which was confirmed by AFM and FTIR analysis has increased both n and thickness of GO film while decreased k. These results proved sensitivity enhancement of the modified chip towards DA and highlighted the technique's appropriate and sufficient potential to measure thickness and refractive index variations in real-time when 100 fM of DA was detected with sensitivity of 12.402°/RIU.

Biosensor-based active ingredient recognition system for screening TNF-α inhibitors from lotus leaves.

Erhuangquzhi granules (EQG) have been clinically proven to be effective in nonalcoholic steatohepatitis (NASH) treatment. However, the active components and molecular mechanisms remain unknown. This study aimed to screen active components targeting tumor necrosis factor α (TNF-α) in EQG for the treatment of NASH by a surface plasmon resonance (SPR) biosensor-based active ingredient recognition system (SPR-AIRS). The amine-coupling method was used to immobilize recombinant TNF-α protein on an SPR chip, the specificity of the TNF-α-immobilized chip was validated, and nine medicinal herbs in EQG were prescreened. Nuciferine (NF), lirinidine (ID), and O-nornuciferine (NNF) from lotus leaves were found and identified as TNF-α ligands by UPLC‒MS/MS, and the affinity constants of NF, ID, and NNF to TNF-α were determined by SPR experiments (Kd = 61.19, 31.02, and 20.71µM, respectively). NF, ID, and NNF inhibited TNF-α-induced apoptosis in L929 cells, the levels of secreted IL-6 and IL-1β were reduced, and the phosphorylation of IKKβ and IκB was inhibited in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. In conclusion, a class of new active small-molecule TNF-α inhibitors was discovered, which also provides a valuable reference for the material basis and mechanism of EQG action in NASH treatment.

The revelation of glucose adsorption mechanisms on hierarchical metal-organic frameworks using a surface plasmon resonance sensor.

The gold layer on the surface plasmon resonance (SPR) sensor chip cannot detect small molecules, such as glucose without the use of specific receptors. Metal-organic frameworks (MOFs) are useful in biosensing technologies for capturing and co-localizing enzymes and receptors with the target biomolecule. In many previous studies, the properties of the MOFs were often ignored, with these studies focusing on the selection of appropriate receptors. To take advantage of the unique properties of MOFs in biosensors, one must also consider the technique and transducer used because these aspects will strongly influence the detection mechanism. In this work, we have investigated for the first time, the applications of hierarchical metal-BDC (M-BDC) MOFs for glucose detection using the SPR technique without the use of specific receptors. The underlying interactions and adsorption mechanisms were analyzed using adsorption isotherm and kinetic models. The sensing measurements show that the SPR chips functionalized with M-BDC MOFs exhibit higher sensitivity and lower limit of detection (LOD). Specifically, the sensitivity follows the order of Zr-BDC > Cu-BDC > Mn-BDC > Ni-BDC > bare Au SPR chips with the LOD in the order of Zr-BDC < Mn-BDC < Ni-BDC < Cu-BDC < bare Au SPR chips. The selectivity test results reveal that Zr-BDC exhibits a decent selectivity to glucose in the presence of other interfering compounds, such as ascorbic acid, uric acid, maltose, and urea. These results demonstrate the promising potential of MOFs for SPR biosensing.

Influence of bovine and human serum albumin on the binding kinetics of biomolecular interactions.

Bovine serum albumin (BSA) containing buffers are the standard blocking buffer in biosensing, yet human serum is the intended application for most clinical sensors. However, the effect of human serum albumin (HSA) on binding assays remains underexplored. A simple and well-studied assay (human IgG/goat anti-human IgG) was investigated with a surface plasmon resonance (SPR) sensor to address this fundamental question in sensing. Calibrations were performed with buffers containing various concentrations of bovine or human serum albumin, as well as full and diluted bovine or IgG-depleted human serum. It was found that HSA or human serum, but not BSA or bovine serum, significantly affected the SPR shift and binding constants of the assay. Interestingly, large differences were also observed depending on whether the animal or human antibody was immobilized on the SPR chip for detection, highlighting that matrix protein/analyte/receptor interactions play a significant role in the response. We find that the interaction of soluble HSA with human IgG interferes with the recognition region, affecting the binding constant, and thus results obtained in BSA are not necessarily applicable to clinical samples or in vivo conditions. We also clearly demonstrate why a minimum dilution of 1 : 10 is often required in SPR assays to remove most background effects. Taken together, these results show that: (1) BSA does not affect the binding constant between antibodies and thus serves its purpose well when only surface blocking is intended, (2) HSA is an adequate surrogate for human serum in assay optimization, and (3) blocking buffers should be prepared with HSA in the optimization steps of assays to be translated to human blood or serum.

Evaluating the Use of Surface Plasmon Resonance-Based Sensing for Colorectal Mucosa Cancer Detection

This paper presents an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in silico</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in vitro</i> study concerning the application of a trapezoidal prism-based surface plasmon resonance chip to detect colorectal cancer by analyzing the mucosa tissue. The sensor is a multilayered structure and works in the wavelength interrogation mode. Performance parameters related to the metallic film characteristics, such as thickness and type of metal were determined. For the analyzed noble metals, the silver film of 40 nm has the highest sensitivity of 6,454.12 nm/RIU, and the 60 nm-thick presents the best values for full width at half maximum and χ parameter (20.20 nm and 286.63 RIU <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">–1</sup> ). The palladium nanolayer deposition enhanced the sensitivity by 10.81% for copper film and peaks at 6,497.04 nm/RIU for the silver film. The palladium nanolayer also provokes deeper dips in the reflectance spectrum. Tissue phantoms were used to study the sensor response to solid surrounding medium to show the feasibility and the correctness of the proposed methodology.

Development of a Plasmonic Sensor for a Chemotherapeutic Agent Cabazitaxel.

Drug dosage is a crucial subject in both human and animal treatment. Administering less drug dosage may prevent treatment or make it less effective, and high drug dosage may cause a heightened risk of adverse effects, or in some cases, cost a patient's life. Also, even when the dosage is administered carefully, metabolic differences may cause different effects on different patients. Because of these considerations, monitoring drug dosage in the body is a critical and significant requirement in the health industry. Within the scope of this study, a reusable surface plasmon resonance (SPR) chip with fast response, high selectivity, and no pretreatment is produced for the chemotherapeutic agent cabazitaxel. A cabazitaxel-imprinted nanofilm was synthesized on the sensor chip surface and characterized by atomic force microscopy, ellipsometry, and contact angle measurements. Standard cabazitaxel solution and an artificial plasma sample were used for the kinetic analysis. Docetaxel, methylprednisolone, and dexamethasone were analyzed for their selectivity experiment. In addition, the repeatability and storage durability of the sensor were also evaluated. As a result of the adsorption studies, the limit of detection and limit of quantitation values were found to be 0.012 and 0.036 μg/mL, respectively. High-performance liquid chromatography analysis was used to validate the response of the cabazitaxel-imprinted sensor.

2D-TMDC-enhanced condensed phase cavity ring-down spectroscopy coupled with surface plasmon resonance for investigation on water isotopologues

We report a novel scheme for sensitivity-enhanced liquid phase cavity ring-down spectroscopy (CRDS) exploiting the two-dimensional transition metal dichalcogenides (2D-TMDCs) based surface plasmon resonance (SPR). We investigated the performance of the proposed sensing scheme by monitoring water isotopologues i.e. D2O (heavy water) and H2O on the SPR chip utilizing a simulation-based characteristics transfer matrix method. The cavity-enhanced SPR coupled with 2D-TMDCs is employed to detect D2O from distilled (DI) water with good time response. This proposed approach exhibited minimum sensitivity up to 448 ns/RIU with 4-layers of molybdenum disulfide (MoS2) and maximum sensitivity up to​ 604 ns/RIU with 4-layers of tungsten diselenide (WSe2). Moreover, dependence of cavity-finesse and chip-sensitivity on the 2D-nanomaterials suggests that SPR-CRDS is a new-strategy for the applications of plasmonic chemical sensing in the condensed phase with absorbance of the order of 10−11.