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MicroRNAs (miRNAs) are potentially useful biomarkers for the evaluation of cancers and chemical toxicity. However, simply and easily operated detection techniques are increasingly needed to enable their use in the biomedical and environmental fields. In this study, we investigated sequence-specific miRNA detections by surface plasmon resonance (SPR) and electrochemical (EC) imaging measurements on SPR-EC chips possessing a Au electrode array modified with probe DNAs and by employing a miRNA-detection-selective signal amplification method. MiRNAs were sequence-specifically detected by SPR and EC imaging measurements on a single chip. SPR signals were enhanced by a combination process employing the sequencespecific hybridization of miRNAs with the probe DNA, the extension reaction of polyadenine [poly(A)] tails on the 3’ end of the miRNAs by poly(A) polymerase, the binding of T30-Au nanoparticles (AuNPs) to the poly(A) tails, and the reduction reaction of Ag+ catalyzed on the AuNPs, depositing a gray precipitate on the surface. The oxidation reaction of the accumulated Ag precipitation additionally provides EC signal amplification. This process considerably and sequence-specifically amplifies the SPR and EC signals. This setup constitutes a simple and feasible signal amplification method for the on-site detection of miRNA biomarkers. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance (SPR) is a powerful tool for determining molecular interactions quantitatively. SPR imaging (SPRi) further improves the throughput of SPR technology and provides the spatially resolved capability for observing the molecular interaction dynamics in detail. SPRi is becoming more and more popular in biological and chemical sensing and imaging. However, SPRi suffers from low spatial resolution due to the imperfect optical components and delocalized features of propagating surface plasmonic waves along the surface. Diverse kinds of approaches have been developed to improve the spatial resolution of SPRi, which have enormously impelled the development of the methodology and further extended its possible applications. In this minireview, we introduce the mechanisms for building a high-spatial-resolution SPRi system and present its experimental schemes from prism-coupled SPRi and SPR microscopy (SPRM) to surface plasmonic scattering microscopy (SPSM); summarize its exciting applications, including molecular interaction analysis, molecular imaging and profiling, tracking of single entities, and analysis of single cells; and discuss its challenges in recent decade as well as the promising future. [ABSTRACT FROM AUTHOR]

Although evolution dynamic investigation onto electrochemically generated bubbles on electrode surfaces is crucial for releasing "bubble blocking" effects, traditional "top view" or "side view" methods make spatiotemporal interfacial revolutions difficult to achieve, which are critical for a deeper understanding and better electrode design. In this study, a novel method utilizing surface plasmon resonance (SPR) is proposed to probe bubble interfacial dynamics. By monitoring reflectivity changes and utilizing differential imaging, real‐time fluctuations in the contact area can be accurately visualized. The investigation onto bubble growth events on both aerophilic and aerophobic surfaces reveals that they occur in very distinct patterns. Due to the "necking effect", the reflectivity of aerophilic electrodes rushed to its highest value and remained or gradually decreased, followed by a sudden drop due to bubble disengagement. While the aerophobic ones increased to the bubble release threshold after a downward parabola function, then dropped abruptly without plateau. This in situ imaging technique provides a feasible tool for bubble disengagement dynamic investigations on electrode surface. Based on current observations, it is revealed that changing the wettability of electrodes causes substantial changes in bubble evolution dynamics. [ABSTRACT FROM AUTHOR]

A new biosensor based on the "surface plasmon resonance imaging (SPRi)" detection technique for the quantification of "fibroblast growth factor 23 (FGF23)" has been developed. FGF23 is mainly produced in bone tissues as a phosphaturic hormone that forms a trimeric complex with "fibroblast growth factor receptor 1 (FGFR1)" and αKlotho upon secretion. FGF23 stimulates phosphate excretion and inhibits the formation of active vitamin D in the kidneys. FGF23 has been shown to play a role in bone carcinogenesis and metastasis. The newly developed method, based on the array SPRi biosensor, was validated—the precision, accuracy, and selectivity were acceptable, and yielded less than ±10% recovery. The rectilinear response of the biosensor ranges from 1 to 75 pg/mL. The limit of detection was 0.033 pg/mL, and the limit of quantification was 0.107 pg/mL. The biosensor was used to determine FGF23 concentrations in the blood plasma of healthy subjects and patients with "clear cell" renal cell carcinoma (ccRCC). The obtained results were compared with those measured through an "enzyme-linked immunosorbent assay (ELISA)". The determined Pearson correlation coefficients were 0.994 and 0.989, demonstrating that the newly developed biosensor can be used as a competitive method for the ELISA. [ABSTRACT FROM AUTHOR]

The early-stage diagnosis and monitoring of disease evolution is still one of the most challenging tasks in the field of cancer research. Several research have been driven toward the discovery of new cancer biomarkers as well as to the development of biosensors able to detect these biomarkers with high specificity and sensitivity. Many types of cancer have been detected at an advanced stage and, in particular, epithelial ovarian cancer (EOC) has a high incidence of diagnosis in the metastatic stage. This cancer is considered as the most aggressive type of gynecological cancer with a 5-year survival and until now, no specific biomarkers have been identified. Nevertheless, some studies have indicated that mesothelin, a protein overexpressed by tumour cells in the ovary, interacts with the CA-125 biomarker present in the blood system accelerating the metastatic process. Therefore, the simultaneous presence of CA-125 and mesothelin in the blood during the evolution of EOC could be used to diagnose this disease before the metastasis. Therefore, with this motivation, this work aimed at the development of a biosensor capable of simultaneously detecting mesothelin and CA-125 at low concentrations. A biosensor based on the surface plasmon resonance imaging (SPRi) technique was developed and gold nanoparticles (AuNPs) were used in order to enhance the sensitivity. The study analysed successive injections of the biomarkers CA-125 and mesothelin, both in solution (analytical range of 9–120 nM). The limits of detection were obtained for CA-125 and mesothelin, being of 3.03 nM and 13.62 nM, respectively. The biosensor detected mesothelin at a concentration close to the cutoff point for EOC (3 nM) and was able to detect the biomarker CA-125 at 9 nM. Furthermore, the biosensor interacted preferentially and simultaneously with the biomarkers CA-125 and mesothelin incubated in fetal bovine serum. Finally, the use of AuNPs increased the sensor signal for CA-125 detection compared to its direct detection and showed greater selectivity for both biomarkers. Therefore, the biosensor has important characteristics that allow testing with real samples. In a future project, it could be applied in the research of diagnosis and prognosis of EOC.

A low ratio of polymerization is a major problem in resin-based composites. In this paper, the plasmonic effect of gold-covered silica nanoparticles on the physicochemical and mechanical properties of bisphenol A diglycidyl dimethacrylate (Bis-GMA), triethylene glycol dimethacrylate (TEGDMA) and urethane dimethacrylate (UDMA) green light-photopolymerizable dental resin was investigated at an intensity of 1.4 mW/cm2 for 40 s. Transmission electron microscopy (TEM) showed silica of about 350 nm covered with 12–15 nm gold nanoparticles (Au NPs) at 100% nominal coverage. Five different concentrations of bare and patchy silica particles were used; in the latter composite, the calculated Au wt% were 0.0052 wt%, 0.0104 wt%, 0.0208 wt%, 0.04160 wt%, and 0.0823 wt%. The plasmon peak of patchy silica-filled nanocomposite overlapped with the absorption of Irgacure 784 photoinitiator and green LED light emission peak. The effect of plasmon-enhanced polymerization achieved with green light illumination was analyzed using diametral tensile strength (DTS), differential scanning calorimetry (DSC), surface plasmon resonance imaging (SPRi), and degree of conversion (DC) based on Raman spectroscopy. The values of the Au NP with 0.0208 wt% was found to be maximum in all the measured data. Based on our result, it can be concluded that the application of patchy silica particles in dental resin can improve the polymerization ratio and the mechanical parameters of the composite. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Chongqing University of Technology (Natural Science) is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Surface plasmon resonance (SPR) is a powerful tool for determining molecular interactions quantitatively. SPR imaging (SPRi) further improves the throughput of SPR technology and provides the spatially resolved capability for observing the molecular interaction dynamics in detail. SPRi is becoming more and more popular in biological and chemical sensing and imaging. However, SPRi suffers from low spatial resolution due to the imperfect optical components and delocalized features of propagating surface plasmonic waves along the surface. Diverse kinds of approaches have been developed to improve the spatial resolution of SPRi, which have enormously impelled the development of the methodology and further extended its possible applications. In this minireview, we introduce the mechanisms for building a high-spatial-resolution SPRi system and present its experimental schemes from prism-coupled SPRi and SPR microscopy (SPRM) to surface plasmonic scattering microscopy (SPSM); summarize its exciting applications, including molecular interaction analysis, molecular imaging and profiling, tracking of single entities, and analysis of single cells; and discuss its challenges in recent decade as well as the promising future.

The inflammatory, reparative and regenerative mechanisms activated in ischemic stroke patients immediately after the event cooperate in the response to injury, in the restoration of functions and in brain remodeling even weeks after the event and can be sustained by the rehabilitation treatment. Nonetheless, patients' response to treatments is difficult to predict because of the lack of specific measurable markers of recovery, which could be complementary to clinical scales in the evaluation of patients. Considering that Extracellular Vesicles (EVs) are carriers of multiple molecules involved in the response to stroke injury, in the present study, we have identified a panel of EV-associated molecules that (i) confirm the crucial involvement of EVs in the processes that follow ischemic stroke, (ii) could possibly profile ischemic stroke patients at the beginning of the rehabilitation program, (iii) could be used in predicting patients' response to treatment. By means of a multiplexing Surface Plasmon Resonance imaging biosensor, subacute ischemic stroke patients were proven to have increased expression of vascular endothelial growth factor receptor 2 (VEGFR2) and translocator protein (TSPO) on the surface of small EVs in blood. Besides, microglia EVs and endothelial EVs were shown to be significantly involved in the intercellular communications that occur more than 10 days after ischemic stroke, thus being potential tools for the profiling of patients in the subacute phase after ischemic stroke and in the prediction of their recovery. [ABSTRACT FROM AUTHOR]

We investigated sequence-specific and simultaneous microRNA (miRNA) detections by surface plasmon resonance (SPR) imaging measurements on SPR chips possessing an Au spot array modified with probe DNAs based on a miRNA-detection-selective SPR signal amplification method. MiRNAs were detected with the detection limit of the attomole level by SPR imaging measurements for different miRNA concentrations on a single chip. SPR signals were enhanced based on a combination process of sequence-specific hybridization of the miRNA to the probe DNAs, extension reaction of polyadenine (poly(A)) tails by poly(A) polymerase, binding of a ternary complex of T30-biotin/horseradish peroxidase (HRP)-biotin/streptavidin to the poly(A) tails, and the oxidation reaction of tetramethylbenzidine (TMB) on the HRP by providing a blue precipitate on the surface. This process sequence-specifically and dramatically amplified the SPR signals. This is a simple, cost-effective, and feasible signal amplification method based on the organic compound TMB instead of metal nanoparticles.

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 (koff). 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. [ABSTRACT FROM AUTHOR]

A new biosensor based on the “surface plasmon resonance imaging (SPRi)” detection technique for the quantification of “fibroblast growth factor 23 (FGF23)” has been developed. FGF23 is mainly produced in bone tissues as a phosphaturic hormone that forms a trimeric complex with “fibroblast growth factor receptor 1 (FGFR1)” and αKlotho upon secretion. FGF23 stimulates phosphate excretion and inhibits the formation of active vitamin D in the kidneys. FGF23 has been shown to play a role in bone carcinogenesis and metastasis. The newly developed method, based on the array SPRi biosensor, was validated—the precision, accuracy, and selectivity were acceptable, and yielded less than ±10% recovery. The rectilinear response of the biosensor ranges from 1 to 75 pg/mL. The limit of detection was 0.033 pg/mL, and the limit of quantification was 0.107 pg/mL. The biosensor was used to determine FGF23 concentrations in the blood plasma of healthy subjects and patients with “clear cell” renal cell carcinoma (ccRCC). The obtained results were compared with those measured through an “enzyme-linked immunosorbent assay (ELISA)”. The determined Pearson correlation coefficients were 0.994 and 0.989, demonstrating that the newly developed biosensor can be used as a competitive method for the ELISA.

The initial microprocess of a major cariogenic bacterium Streptococcus mutans forming biofilm at a single-cell level via sucrose-dependent adhesion has not been observed because the cells' high moisture content caused measurement challenges. To develop a high-sensitivity biosensor chip and a real-time, label-free method to observe bioactive molecule interactions with single cells from oral biofilms. We made the chips of immobilized bacteria by micronano-processing. A surface plasmon resonance imaging (SPRI) system was used to detect and record the association and dissociation microprocess of S. mutans with sucrose/dextran solutions of various concentrations, and the calculus model was adopted to treat the data. At the location of S. mutans, a unique 'comet-tail' SPRI signal was observed. The binding patterns of S. mutans differed between individual cells exposed to the same solution as well as between sucrose and dextran. The different cells exhibited different affinities with dissociation constants for sucrose being 5.697 × 10−3 to 3.689 M and for dextran 1.235 × 10−3 to 1.282 M, indicating cell-to-cell heterogeneity. Our SPRI detection method is effective in investigating microbial binding, initial biofilm formation, and oral microecology. It offers new possibilities for studying oral microorganism characteristics and development of oral diseases. [ABSTRACT FROM AUTHOR]

The initial microprocess of a major cariogenic bacterium Streptococcus mutans forming biofilm at a single-cell level via sucrose-dependent adhesion has not been observed because the cells’ high moisture content caused measurement challenges. To develop a high-sensitivity biosensor chip and a real-time, label-free method to observe bioactive molecule interactions with single cells from oral biofilms. We made the chips of immobilized bacteria by micronano-processing. A surface plasmon resonance imaging (SPRI) system was used to detect and record the association and dissociation microprocess of S. mutans with sucrose/dextran solutions of various concentrations, and the calculus model was adopted to treat the data. At the location of S. mutans, a unique ‘comet-tail’ SPRI signal was observed. The binding patterns of S. mutans differed between individual cells exposed to the same solution as well as between sucrose and dextran. The different cells exhibited different affinities with dissociation constants for sucrose being 5.697 × 10−3 to 3.689 M and for dextran 1.235 × 10−3 to 1.282 M, indicating cell-to-cell heterogeneity. Our SPRI detection method is effective in investigating microbial binding, initial biofilm formation, and oral microecology. It offers new possibilities for studying oral microorganism characteristics and development of oral diseases.

Copyright of Chinese Journal of Liquid Crystal & Displays is the property of Chinese Journal of Liquid Crystal & Displays and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The inflammatory, reparative and regenerative mechanisms activated in ischemic stroke patients immediately after the event cooperate in the response to injury, in the restoration of functions and in brain remodeling even weeks after the event and can be sustained by the rehabilitation treatment. Nonetheless, patients’ response to treatments is difficult to predict because of the lack of specific measurable markers of recovery, which could be complementary to clinical scales in the evaluation of patients. Considering that Extracellular Vesicles (EVs) are carriers of multiple molecules involved in the response to stroke injury, in the present study, we have identified a panel of EV-associated molecules that (i) confirm the crucial involvement of EVs in the processes that follow ischemic stroke, (ii) could possibly profile ischemic stroke patients at the beginning of the rehabilitation program, (iii) could be used in predicting patients’ response to treatment. By means of a multiplexing Surface Plasmon Resonance imaging biosensor, subacute ischemic stroke patients were proven to have increased expression of vascular endothelial growth factor receptor 2 (VEGFR2) and translocator protein (TSPO) on the surface of small EVs in blood. Besides, microglia EVs and endothelial EVs were shown to be significantly involved in the intercellular communications that occur more than 10 days after ischemic stroke, thus being potential tools for the profiling of patients in the subacute phase after ischemic stroke and in the prediction of their recovery.

In the context of bacteriophage (phage) therapy, there is an urgent need for a method permitting multiplexed, parallel phage susceptibility testing (PST) prior to the formulation of personalized phage cocktails for administration to patients suffering from antimicrobial-resistant bacterial infections. Methods based on surface plasmon resonance imaging (SPRi) and phase imaging were demonstrated as candidates for very rapid (<2 h) PST in the broth phase. Biosensing layers composed of arrays of phages 44AHJD, P68, and gh-1 were covalently immobilized on the surface of an SPRi prism and exposed to liquid culture of either Pseudomonas putida or methicillin-resistant Staphylococcus aureus (i.e., either the phages' host or non-host bacteria). Monitoring of reflectivity reveals susceptibility of the challenge bacteria to the immobilized phage strains. Investigation of phase imaging of lytic replication of gh-1 demonstrates PST at the single-cell scale, without requiring phage immobilization. SPRi sensorgrams show that on-target regions increase in reflectivity more slowly, stabilizing later and to a lower level compared to off-target regions. Phage susceptibility can be revealed in as little as 30 min in both the SPRi and phase imaging methods. [ABSTRACT FROM AUTHOR]

Molecular dynamics characteristics have important significance in studying the interaction between biomolecules, such as drug screening, environmental monitoring and evaluation of virus infectivity. In this work, a simulation method based on step function is proposed to study the molecular binding and dissociation processes, which is further coupled with surface plasmon wave evanescent field. A complete simulation model is established from biomolecular reaction to surface plasmon resonance (SPR) optical detection, which is consistent with the experimental process. Furthermore, experimental verification studies were carried out on human serum albumin (HSA), a marker of the urinary protein disease. The effects of microchannel size, liquid flow rate, molecular concentration, complex samples and other conditions on the molecular dynamics binding characteristics were studied under the conditions of antibody fixation and antigen–antibody binding reaction. Optimized parameters are obtained such as microchannel size and liquid flow rate, which can save reaction reagents reduce the experimental process and improve the experimental detection accuracy. Therefore, the established simulation and experimental methods include a complete process from biological information to optical information, which is expected to be a powerful tool for molecular interaction analysis in the future. [ABSTRACT FROM AUTHOR]

SPRi protein arrays for rapid, label-free immunodetection offer an attractive approach for high throughput biosensing and analysis of molecular interactions. However, their routine use for quantitative analysis requires adequate reproducibility and homogeneity of receptor assemblies manufactured ex-situ using microdispensing techniques. There is also an emerging need to develop versatile and non-destructive methods for the determination of protein surface density for quality control of the immobilization process. Here, we report on a simple, one-step method of surface proteins visualization by their reversible, non-specific staining with anionic dyes: Ponceau S (PS), Amido Black (AB) or Coomassie Brilliant Blue G (CBB-G). Using rabbit IgG antibody and transferrin as model receptors, we demonstrate the possibility of protein surface density determination in a broad range up to ∼ 3 ng∙mm−2 (for a 2D monolayer) and up to at least 12.5 ng∙mm−2 (for a 3D hydrogel-coated substrate). The ranges of dynamic response for the developed methods cover the typical surface densities required for biosensing and studies of the binding kinetics. It was demonstrated that each of the investigated dyes manifests advantages in specified applications. While CBB-G shows the highest sensitivity of SPRi response, AB requires the gentlest labeling conditions, and PS shows the highest association rate and ease of washing out, even from protein layers of high density. The feasibility of the developed method for the quality control of SPRi microarray was confirmed. The advantages of the new, dye-based, non-specific labeling method over immunolabeling in terms of simplicity of implementation and versatility have also been highlighted. [Display omitted] • A new method for quality control of protein receptor layers using SPRi was developed. • Ponceau S, Amido Black and Coomassie G were selected as non-specific protein dyes. • Developed protocols were validated for rabbit IgG and transferrin as model receptors. • Correlations between receptor surface densities and SPRi responses to dye were shown. • Dye-based method was employed for protein mapping on ex-situ spotted SPRi microarrays. [ABSTRACT FROM AUTHOR]

A surface plasmon resonance imaging (SPRI)-based biosensor is demonstrated for the detection of both hydrogen peroxide (H 2 O 2) and glucose. The H 2 O 2 to be detected acts as an oxidant and etch the silver film. This process gradually effects on resonance condition and consequently the reflected light intensity at a fixed angle. The etching rate of the silver film shows a clear relation with the H 2 O 2 concentration. Therefore, monitoring the reflected light intensity progressively changing over a few minutes, enables accurate detection of H 2 O 2 concentrations ranging from 0 to 200 μM (within physiological range of 0.25–50 μM), with a remarkable limit of detection (LOD) as low as 40 nM. In this regard, the behavior of the surface plasmon resonance (SPR) dip in response to the reduction of the silver film thickness is predicted by Winspall simulation software. These simulation results are in good agreement with the experimental results. Moreover, the proposed method can be applied to determine glucose concentrations ranging from 0 to 10 mM, encompassing the physiological range of 3–8 mM. This is achieved by observing the generated H 2 O 2 through the enzymatic oxidation reaction between glucose and glucose oxidase (Gox). The sensor demonstrates remarkable sensitivity and selectivity, with a detection limit as low as 175 μM for glucose concentration. Furthermore, accurate measurement of glucose concentration in an actual human serum sample is achievable with the proposed sensor, using the standard addition method. The suggested glucose sensor shows promising prospects for use in routine glucose testing, employing a label-free, real-time, and multiplex detection approach.© 2017 Elsevier Inc. All rights reserved. [Display omitted] • Dual Detection : SPRI biosensor detects both H2O2 and glucose. • H2O2 Sensing : Silver film etching by H2O2 alters light intensity, enabling detection down to 40 nM. • Simulation Validation : Winspall software confirms SPR dip behavior, aligning with experimental data. • Glucose Detection : Enzymatic oxidation detects glucose concentrations from 0 to 10 mM with a 175 μM detection limit. • Real-world Application : Biosensor accurately measures glucose in human serum, promising routine testing with label-free, real-time detection. [ABSTRACT FROM AUTHOR]

Multiple sclerosis (MS) is the most common autoimmune disease observed in young adults and is known to be exceptionally difficult to diagnose accurately. Current diagnostic methods are considered unreliable and inefficient, and they typically lack the needed specificity that allows for routine monitoring of disease progression. In this work, we report a surface plasmon resonance imaging (SPRi) method in combination with carbohydrate microarrays for the detection of multiple sclerosis biomarkers in undiluted serum. A working range of 1–100 ng/mL was demonstrated with the limit of detection (LODs) below 7 ng/mL. The microarrays utilized in this work were coated with perfluorodecyltrichlorosilane (PFDTS) to interact strongly with the hydrophobic tails of the ganglioside antigens, allowing for desirable antigenic display in a manner mimicking a myelin sheath. Machine learning (ML) algorithms were applied to the carbohydrate array/SPRi data analysis to understand and characterize the cross reactivities observed between the antibodies. Both endpoint results and SPRi sensorgrams were analyzed with statistical models for the evaluation of binding events that include kinetic and steady state components. In addition, K-nearest neighbor (kNN) and neural net (nnet) were utilized to examine specific and cross-reactive binding, yielding higher accuracy than what traditional methods can achieve. The combination of ML models and microarray data provides a comprehensive understanding of complex interactions and could be used to differentiate and identify closely behaving biomarkers in a clinical setting.

[Display omitted] • Obovatol's role as α-glucosidase (α-Glu) and α-amylase (α-Amy) inhibitor was assessed. • Synthesis of ten obovatol analogous for α-Glu and α-Amy inhibition. • Compounds 1 , 11 , 22 , 26 and 27 were effective inhibitors and were tested for cytotoxicity. • Interaction with the enzyme was studied by CD analysis, SPR imaging and molecular docking studies. • Obovatol-based neolignans are promising structures for developing novel hypoglycemic drugs. Diabetes mellitus is a metabolic disease characterized by hyperglycemia, which can be counteracted by the inhibition of α-glucosidase (α-Glu) and α-amylase (α-Amy), enzymes responsible for the hydrolysis of carbohydrates. In recent decades, many natural compounds and their bioinspired analogues have been studied as α-Glu and α-Amy inhibitors. However, no studies have been devoted to the evaluation of α-Glu and α-Amy inhibition by the neolignan obovatol (1). In this work, we report the synthesis of 1 and a library of new analogues. The synthesis of these compounds was achieved by implementing methodologies based on: phenol allylation, Claisen/Cope rearrangements, methylation, Ullmann coupling, demethylation, phenol oxidation and Michael-type addition. Obovatol (1) and ten analogues were evaluated for their in vitro inhibitory activity towards α-Glu and α-Amy. Our investigation highlighted that the naturally occurring 1 and four neolignan analogues (11 , 22 , 26 and 27) were more effective inhibitors than the hypoglycemic drug acarbose (α-Amy: 34.6 µM; α-Glu: 248.3 µM) with IC 5O value of 6.2–23.6 µM toward α-Amy and 39.8–124.6 µM toward α-Glu. Docking investigations validated the inhibition outcomes, highlighting optimal compatibility between synthesized neolignans and both the enzymes. Concurrently circular dichroism spectroscopy detected the conformational changes in α-Glu induced by its interaction with the studied neolignans. Detailed studies through fluorescence measurements and kinetics of α-Glu and α-Amy inhibition also indicated that 1 , 11 , 22 , 26 and 27 have the greatest affinity for α-Glu and 1 , 11 and 27 for α-Amy. Surface plasmon resonance imaging (SPRI) measurements confirmed that among the compounds studied, the neolignan 27 has the greater affinity for both enzymes, thus corroborating the results obtained by kinetics and fluorescence quenching. Finally, in vitro cytotoxicity of the investigated compounds was tested on human colon cancer cell line (HCT-116). All these results demonstrate that these obovatol-based neolignan analogues constitute promising candidates in the pursuit of developing novel hypoglycemic drugs. [ABSTRACT FROM AUTHOR]

Differential sensing of proteins based on cross-reactive arrays and pattern recognition is a promising technique for the detection and identification of proteins. In this study, a rational biomimetic strategy has been used to prepare sensing materials capable of discriminating structurally similar proteins, such as deletion and point mutants of a cytokine, by mimicking the biological properties of heparan sulfate (HS). Using the self-assembly of two disaccharides, lactose and sulfated lactose at various ratios on the surface of a chip, an array of combinatorial cross-reactive receptors has been prepared. Coupling with surface plasmon resonance imaging (SPRi), the obtained cross-reactive array is very efficient for protein sensing. It is able to detect HS binding proteins (HSbps) such as IFNγ at nanomolar concentrations. Moreover, such a system is capable of discriminating between IFNγ and its mutants with good selectivity. [ABSTRACT FROM AUTHOR]

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 (koff). 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.

In the context of bacteriophage (phage) therapy, there is an urgent need for a method permitting multiplexed, parallel phage susceptibility testing (PST) prior to the formulation of personalized phage cocktails for administration to patients suffering from antimicrobial-resistant bacterial infections. Methods based on surface plasmon resonance imaging (SPRi) and phase imaging were demonstrated as candidates for very rapid (Pseudomonas putida or methicillin-resistant Staphylococcus aureus (i.e., either the phages’ host or non-host bacteria). Monitoring of reflectivity reveals susceptibility of the challenge bacteria to the immobilized phage strains. Investigation of phase imaging of lytic replication of gh-1 demonstrates PST at the single-cell scale, without requiring phage immobilization. SPRi sensorgrams show that on-target regions increase in reflectivity more slowly, stabilizing later and to a lower level compared to off-target regions. Phage susceptibility can be revealed in as little as 30 min in both the SPRi and phase imaging methods.

Extracellular vesicles (EVs) have great potential as biomarkers since their composition and concentration in biofluids are disease state dependent and their cargo can contain disease-related information. Large tumor-derived EVs (tdEVs, >1 μm) in blood from cancer patients are associated with poor outcome, and changes in their number can be used to monitor therapy effectiveness. Whereas, small tumor-derived EVs (<1 μm) are likely to outnumber their larger counterparts, thereby offering better statistical significance, identification and quantification of small tdEVs are more challenging. In the blood of cancer patients, a subpopulation of EVs originate from tumor cells, but these EVs are outnumbered by non-EV particles and EVs from other origin. In the Dutch NWO Perspectief Cancer-ID program, we developed and evaluated detection and characterization techniques to distinguish EVs from non-EV particles and other EVs. Despite low signal amplitudes, we identified characteristics of these small tdEVs that may enable the enumeration of small tdEVs and extract relevant information. The insights obtained from Cancer-ID can help to explore the full potential of tdEVs in the clinic. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs), considered as therapeutic targets and biomarkers, play important roles in biological processes. Herein, an enzyme-free surface plasmon resonance imaging (SPRi) biosensing method has been developed for miRNA detection based on catalytic hairpin assembly and spherical nucleic acid. The hairpin H1 tethered on the surface of the sensor chip is unfolded by miRNA, and then the hybridized miRNA is released through the displacement of the hairpin H2 for the successive hybridization and assembly process. The emerging DNA fragments on the sensor chip surface after hairpins assembly are further used to hybridize with spherical nucleic acid, inducing a remarkably amplified SPR signal. This biosensing method is highly sensitive to miRNA with a detection limit of 53.7 fM and a linear range of 4 orders of magnitude. Moreover, the biosensor demonstrates good specificity and has the ability to distinguish members of homologous miRNA family even with single base differences. Thus, the SPRi biosensing method may hold a great promise for further application in early clinical diagnosis. Schematic illustration of an enzyme-free SPRi biosensor was developed for highly sensitive and specific detection of microRNA. Image 1 • A simple and enzyme-free surface plasmon resonance imaging (SPRi) biosensor was developed for microRNA detection. • The excellent signal amplification efficiency was achieved by catalytic hairpin assembly and spherical nucleic acid. • The designed SPRi biosensor showed wide detection range of 4 orders magnitude and low limit of detection of 53.7 fM. • The method could distinguish members of homologous microRNA families, even with single base differences. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance imaging (SPRi) by enabling label‐free, real time assessment of biomolecular interactions in multiplexed manner is one of the methods of choice for high throughput characterization of large pools of DNA aptamer candidates following in vitro selection. Moreover, with major advances in in situ amplification methods SPRi became also a viable detection platform for aptamer microarrays. In case of aptamer microarrays, commonly prepared by microspotting, the direct assessment of the surface density of aptamer probes, which is essential for both kinetic and sensing measurements is not possible. Therefore, here we introduce a methodology for simple, one‐step determination of surface densities of thiol labelled aptamer monolayers microspotted on gold SPRi chips. Based on this methodology we investigated in detail the effect of the surface density of aptamers on target binding through two aptamer‐target systems, i. e. human immunoglobulin E (hIgE) and six histidine tag 6xHis‐tag. We found that the surface density of the aptamers is indeed critical and shows a sharp maximum in terms of target binding efficiency, which is largely determined by the size of the target. The optimal aptamer surface densities determined, the immobilization chemistry (shared by many detection platforms, e. g., electrochemical, surface acoustic) and the trends identified may be used for rapid rational optimization of aptamer‐target assays. [ABSTRACT FROM AUTHOR]

Bladder cancer (BCa) is the ninth most common cancer in the world and its early detection is crucial for successful therapy. Unfortunately, there are no satisfactory tools to detect BCa at early stages and BCa's confirmation muscle-invasive. The search for a suitable biomarker is therefore necessary and aromatase is a potential candidate. The purpose of the current study was to determine if aromatase serves as a biomarker of BCa. A Surface Plasmon Resonance Imaging biosensor was applied for the quantification and determination of aromatase. A total of 3 µl blood plasma was used for a single measurement. The results revealed that the aromatase concentration in the plasma of patients with BCa (n=78) ranged from 17.41–57.44 ng/ml. The range determined in healthy donors (n=18) was 2.59–7.74 ng/ml. Additionally, it was revealed that muscle invasive BCa samples exhibited elevated, statistically significant (P=0.01) average aromatase concentrations in blood plasma (38.64 ng/ml) when compared with non-muscle invasive samples (29.83 ng/ml). The results demonstrated that plasma aromatase may serve as an excellent bimarker of BCa with 100% sensitivity, 100% selectivity and an area under the curve value of the reciever operating characteristic curve equal to 1.0. Furthermore, the marker differenciated between muscle-invasive and non muscle-invasive BCa with a sensitivity of 60% and a specificity of 81%. In conclusion, aromatase may serve a role in bladder tumorigenesis. [ABSTRACT FROM AUTHOR]

Comparative study for non-specific adsorption of cell lysate and serum on recently developed biosensor surfaces is reported. Different surface chemistries including, polyethylene glycol (PEG), α-cyclodextrin (CD), hydrogel dextran and surface initiated polymerization (SIP) based gold surfaces were taken into account for this study. Various techniques including, surface plasmon resonance imaging (SPRi) and matrix-assisted laser desorption ionization tandem time-of-flight mass spectrometry (MALDI−TOF/TOF MS) technique to evaluate the surfaces with Fourier transform infrared spectroscopy (FTIR) for the confirmation of surface fabrication were used. A high non-specific adsorption response of cell lysate and serum was observed on these so-called non-fouling surfaces. The obtained results from this comparative study provided some hope to explore SIP and dextran surface as a universal platform for biosensor applications. SIP produced best result and showed high sensitivity and minimum non-specific adsorption. We believe that this comparative study will surely help the researchers to further upgrade these surfaces and especially SIP to make it more universal for biosensor microarray applications including biomarker discovery in high throughput format. [ABSTRACT FROM AUTHOR]

Fast detection of bacteria in samples presumed to be un-contaminated, such as blood, is of great importance. Indeed, rapid diagnosis allows the set-up of appropriate antibiotic treatment. Besides clinical issues, there are many other domains, such as food processing or drug manufacturing, where the strict absence of any bacteria has to be assessed. Because the bacterial load found in most contaminated samples is often below the limit of detection for currently validated assays, a preliminary enrichment step is required to allow bacterial multiplication before proceeding to the analysis step, whatever it might be – cultural, immunological or molecular methods. In this study, we describe the use of a biosensor for single-step bacteria detection. The whole analysis is performed in less than 20 h, during the growth phase of the micro-organisms, using an array of antimicrobial peptides (AMPs) coupled with a surface plasmon resonance imager (SPRI). A wide range of bacterial strains are assayed, showing differentiated affinity patterns with the immobilized peptides, which are confirmed by multivariate analysis. This work establishes the evidence that antimicrobial peptides, mostly used so far in the antibiotic drug industry, are suited for the wide-spectrum detection of unknown bacteria in samples, even at very low initial loads. Moreover, the small set of AMPs that were assayed provided a specific affinity profile for each pathogen, as confirmed by multivariate analyses. Furthermore, this work opens up the possibility of applying this method in more complex and relevant samples such as foodstuff, urine or blood. • An antimicrobial peptide micro-array dedicated to bacteria detection is presented. • The same antimicrobial peptide set enables the detection of 5 pathogens. • The one-step detection of low bacterial loads is achieved in less than 20 h. • Label-free assays are completed without requisite sample enrichment. • 6 different antimicrobial peptides enabled the pathogenic strain clustering. Image 1 [ABSTRACT FROM AUTHOR]

Overexpression of human epidermal growth factor receptor-2 (HER2) is an important prognostic indicator for clinical diagnosis, as it results in more invasive cancer cells and lower survival rates. In this study, we developed a novel immunosensor based on surface plasmon resonance imaging (SPRi) modified with nanobody 2 (NB2) to detect the HER2 expression of various cancer cells. Firstly, we established a multi-channel intensity interrogation SPRi system with a refractive index resolution (RIR) of 1 × 10−6 RIU. Then, we fabricated the immunosensor by immobilizing NB2 nanobody on the sensor chip through affinity-based orientation. The NB2 exhibited high specificity for HER2 extracellular domain, enabling specific capture of HER2-positive cancer cells. The results revealed that the sensor could detect the HER2 expression of various living cancer cells by directly injecting cell suspensions. Compared with flow cytometry, SPRi system could obtain similar HER2 expression results with better performance, such as faster response time (<30 min), smaller sample volume (<200 μL), and lower cell concentration (105 cells/mL). The most important of all is that researchers do not need to take complex fluorescent labeling pretreatment of cell samples. Therefore, such immunosensors may offer great potential for rapid personalized treatment planning and enhanced patient outcomes. [Display omitted] • A novel label-free and rapid detection method was developed for HER2-positive cancer diagnosis using SPRi modified with nanobody. • The system enabled accurate discrimination between HER2-positive and HER2-negative cell lines within 30 min. • Low cell sample volumes (<200 μL) and concentrations (105 cells/mL) were needed. [ABSTRACT FROM AUTHOR]

Fixation and permeabilization of cells and tissues are essential processes in biological techniques like immunofluorescence and immunohistochemistry for cell biology studies. In typical procedures, the biological samples are treated by paraformaldehyde and Triton X-100 to achieve cellular fixation and permeabilization, respectively, prior to the incubation with specific antibodies. While it is well-known that the integrity of cell membrane has been broken during these processes, quantitative studies on the loss of cellular mass density and the enhancement of molecular accessibility at single cell level are still rare. In this study, we employed the surface plasmon resonance (SPR) imaging technique to monitor the mass density change of single cells during sequential fixation and permeabilization processes. We further utilize the osmotic responses of single cells to sugar molecules as an indicator to evaluate the integrity of cell membranes. It was found that, while fixation initially destructed the integrity of cell membranes and increased the permeability of intra- and extra-cellular molecules, it was permeabilization process that substantially induced significant loss in cellular mass density.

α-Cyclopiazonic acid (CPA) is a tremorgenic mycotoxin produced by Aspergillus and Penicillium fungal species, commonly found on agricultural commodities or fermented food products. A sensitive and rapid imaging surface plasmon resonance (iSPR) assay was developed to detect CPA in maize and cheese by combining an indirect competitive immunoassay and signal amplification based upon a secondary antibody (Ab2) conjugated with gold nanoparticles. Matrix-matched calibration curves were used to determine CPA content in maize and cheese samples. Recoveries, at two spiking levels in maize and cheese, were 89 to 126%, with standard deviations of repeatability (RSDr) of less than 16%. The limits of detection were 17 and 6 μg/kg in maize and cheese, respectively. To separate the CPA-contaminated samples from uncontaminated samples, a cutoff validation level of 40 μg/kg was introduced. The assay was applied to samples of naturally contaminated maize and was compared with competitive inhibition enzyme-linked immunosorbent assay (CI-ELISA). This is the first report to detect CPA using an immuno-biosensor iSPR format. [ABSTRACT FROM AUTHOR]

Glycopolymers mimicking GM1 gangliosides were synthesized by incorporating multiple types of carbohydrates into the polymer backbone. The glycopolymers were immobilized onto gold surfaces, and the interactions with the cholera toxin B subunit (CTB) were analyzed using surface plasmon resonance imaging. The glycopolymer containing both galactose and neuraminic acid showed enhanced recognition of CTB. The interaction was enhanced mainly because of an improvement in the dissociation process by the binding of the neuraminic acid group in the GM1 binding pocket. This cooperativity of galactose and neuraminic acid was achieved by incorporation into the same flexible polymer backbone, and the importance of the close placement of galactose and neuraminic acid groups was revealed. These results will be valuable in medical fields and also for the development of biofunctional materials. Carbohydrates constructing GM1 oligosaccharide were assumed as "carbohydrate modules", and glycopolymers were synthesized by reconstructing the carbohydrates as polymeric mimic. The interaction with cholera toxin B subunit (CTB) was analyzed using surface plasmon resonance imaging. It was revealed the glycopolymer with Gal and Neu5Ac modules exhibits enhanced interaction with CTB by cooperativity of the two carbohydrates. [ABSTRACT FROM AUTHOR]

Highlights • We report the development of an SPRi-based hemagglutinin quantitative assay. • The assay enables vaccine potency evaluation and virus particles quantification. • It presents higher reproducibility (<3%) and greater range (0.03–20 µg/ml) than SRID. • SPRi-based assay offers good correlation with total viral particles counting. • We used SPRi-based assay to monitor influenza production kinetics in cell culture. Abstract Influenza vaccine manufacturers lack tools, whatever the involved production bioprocess (egg or cell-based), to precisely and accurately evaluate vaccine antigen content from samples. Indeed, the gold standard single-radial immunodiffusion (SRID) assay, which remains the only validated assay for the evaluation of influenza vaccine potency, is criticized by the scientific community and regulatory agencies since a decade for its high variability, lack of flexibility and low sensitivity. We hereby report an imaging surface plasmon resonance (SPRi) assay for the quantification of both inactivated vaccine influenza antigens and viral particles derived from egg- and cell-based production samples, respectively. The assay, based on fetuin-hemagglutinin interactions, presents higher reproducibility (<3%) and a greater analytical range (0.03–20 µg/mL) than SRID for bulk monovalent and trivalent vaccine and its limit of detection was evaluated to be 100 times lower than the SRID's one. Finally, viral particles production through cell culture-based bioprocess was also successfully monitored using our SPRi-based assay and a clear correlation was found between the biosensor response and total virus particle content. [ABSTRACT FROM AUTHOR]

Abstract In terms of hybridization assays surface plasmon resonance imaging (SPRi) offers high throughput, label-free and real-time monitoring of the binding kinetics. This requires DNA microarrays on bare or modified gold SPRi chips, which are generally premade by an off-line microspotting procedure. Therefore, the surface density of the immobilized probes is not known although it is an essential quality control parameter, especially, when it can vary in a broad range as in case of self-assembled thiol-labeled DNAs on gold surface. Here we show that the small molecular weight ruthenium(III) hexamine complex (RuHex) introduced earlier for electrochemical quantitation of DNA coverage on gold electrodes can be used also in SPRi to assess the surface density of DNA probes in DNA microarrays. A single injection of RuHex solution allows the simultaneous visualization and quantification of the surface density of DNA probes (ranging in this study from 4 × 1011 to 1.7 × 1013 molecules cm−2) on all spots of a microarray made by microspotting thiol labeled short DNA probes both in prehybridized and single-stranded form on a gold SPRi chip. The methodology was applied to determine the effect of the surface density of DNA probes on the hybridization efficiency and kinetics of complementary microRNAs, using hsa-miR-208a-3p as model. Single mismatch duplexes were found to be more effectively destabilized than fully complementary duplexes by steric hindrance at large surface densities of the DNA probes, which offers an effective mean to increase single mismatch selectivity. Graphical abstract Image 1 Highlights • RuHex efficiently reveals immobilized DNA spots on DNA microarrays by SPRi. • RuHex enables multiplexed quantitative assessment of DNA surface concentration by SPRi. • The method enables convenient optimization of DNA arrays for hybridization assays. • DNA surface concentration is key to adjust the optimal selectivity and hybridization efficiency. [ABSTRACT FROM AUTHOR]

Abstract Nowadays, monitoring of volatile organic compounds (VOCs) is very important in various domains. In this work, we aimed to develop sensitive olfactory biosensors using odorant binding proteins (OBPs) as sensing materials. Three rat OBP3 derivatives with customized binding properties were designed and immobilized on the same chip for the detection of VOCs in solution by surface plasmon resonance imaging (SPRi). We demonstrated that the proteins kept their binding properties after the immobilization under optimized conditions. The obtained olfactory biosensors exhibited very low limits of detection in both concentration (200 pM of β-ionone) and in molecular weight of VOCs (100 g/mol for hexanal). Such a performance obtained with SPRi in solution is especially remarkable. We hypothesized that the binding of VOCs to the active sites of OBPs induced a local conformational change in the proteins. This change would give rise to a variation of refractive index, to which SPRi is extremely sensitive. In addition, the olfactory biosensors showed a high selectivity especially at relatively low VOC concentrations. With optimized regeneration procedures, they also showed very good repeatability not only from measurement to measurement but also from chip to chip with a lifespan up to almost two months. These olfactory biosensors are particularly interesting for trace detection of VOCs in solution. Highlights • Custom-made odorant binding proteins (OBPs) are used for olfactory biosensor development. • SPRi is efficient for the detection of volatile organic compounds in solution. • A local conformational change in OBPs has most likely amplified the optical signal. • The olfactory biosensors are highly sensitive and selective at low concentrations. [ABSTRACT FROM AUTHOR]

Prion diseases are transmissible neurodegenerative disorders of humans and animals, which are characterized by the aggregation of abnormal prion protein (PrPSc) in the central nervous system. Although several small compounds that bind to normal PrP (PrPC) have been shown to inhibit structural conversion of the protein, an effective therapy for human prion disease remains to be established. In this study, we screened 1200 existing drugs approved by the US Food and Drug Administration (FDA) for anti-prion activity using surface plasmon resonance imaging (SPRi). Of these drugs, 31 showed strong binding activity to recombinant human PrP, and three of these reduced the accumulation of PrPSc in prion-infected cells. One of the active compounds, alprenolol hydrochloride, which is used clinically as a β-adrenergic blocker for hypertension, also reduced the accumulation of PrPSc in the brains of prion-infected mice at the middle stage of the disease when the drug was administered orally with their daily water from the day after infection. Docking simulation analysis suggested that alprenolol hydrochloride fitted into the hotspot within mouse PrPC, which is known as the most fragile structure within the protein. These findings provide evidence that SPRi is useful in identifying effective drug candidates for neurodegenerative diseases caused by abnormal protein aggregation, such as prion diseases. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance imaging (SPRi) is a powerful tool for label-free, real-time and high-throughput immunoassay, but its sensitivity needs essential improvement. It has been recently reported that the sensitivity of angular-interrogation surface plasmon resonance (SPR) could be efficiently enhanced on single-layer graphene-coated gold chip. The usefulness of this method however remains unclear for reflectivity-based SPRi platform. Herein for the first time we demonstrate that the graphene coating-enabled intrinsic sensitivity enhancement is applicable to high-throughput SPRi and the enhancement factor is further quantitatively evaluated. High-quality single-layer graphene is transferred in a site-controllable manner to cover half of spots on the SPRi gold array chip. With anti-zearalenone (ZEN) antibody as a model target and polydopamine (PDA) thin film as a reactive layer for probe immobilization, the SPRi detection signals on two types of sensing spots are quantitatively compared on a single chip and the enhancement factor is evaluated. It is unambiguously disclosed that on the reflectivity-based SPRi platform, single-layer graphene coating results in a ca. 40% enhancement on the detection signal (reflectivity increase, ΔR). This work unveils the compelling SPRi sensitivity enhancement of graphene coating and may facilitate its broad practical applications. [ABSTRACT FROM AUTHOR]

This study investigates the local variation of concentration and selective evaporation flux affected by the droplet-to-droplet distance during the evaporation of multiple-binary mixture droplets (M-BMDs). Surface plasmon resonance imaging (SPRi) is used to measure the local liquid concentration of the binary mixture droplets and to analyze the spatial distributions of liquid concentration with the estimated local changes of surface tension during evaporation. In addition, we conduct three-dimensional numerical simulations to predict the ethanol vapor distributions and the local ethanol evaporation flux for single- and multiple-binary mixture droplets. It was found that the total evaporation time of M-BMDs is delayed due to vapor accumulation in the region adjacent to the neighboring droplets for M-BMDs, which significantly reduces the local evaporation flux. Also, the local liquid concentration of M-BMDs was found to vary, showing a lower ethanol concentration far away from the adjacent region due to vapor shielding and selective evaporation. Moreover, the scaled lifetime, which is the ratio of evaporation time between multiple droplets and a single droplet, shows good agreement with the previously reported experiments and theoretical models. • Local vapor accumulation and selective evaporation are analyzed for the evaporating multiple-binary mixture droplets. • Surface plasmon resonance imaging is used to measure the local change of concentration during evaporation directly. • The vapor shielding effect becomes weakened with the increase of the droplet-to-droplet distance. • Vapor accumulation causes the non-uniform evaporation flux between binary mixture droplets. • Numerical simulations predict the local evaporation flux of ethanol and water. [ABSTRACT FROM AUTHOR]

Ionizing radiations induce clustered damage sites known to be severely challenging for the cell's repair machinery. In the present study, we have grafted on a biochip four synthetic oligonucleotide duplexes containing either a single 8-oxoguanine, a single 2'-deoxyribose abasic site or two different clustered damages containing these two lesions on opposite strands. Using a SPR imaging-based DNA array, we qualitatively observed the hierarchy of lesion processing by the base excision repair (BER) enzyme Fpg (Formamidopyrimidine (fapy)-DNA glycosylase). We could notably show that Fpg can convert a cluster of lesions into a potentially lethal double strand break (DSB) and demonstrate that SPR imaging is suitable to investigate the incision steps occurring during the repair process.