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Extracellular vesicles (EVs) have shown great potential as biomarkers since they reflect the physio-pathological status of the producing cell. In the context of cytotoxicity, it has been found that exposing cells to toxicants leads to changes in protein expression and the cargo of the EVs they produce. Here, we studied large extracellular vesicles (lEVs) derived from human microvascular endothelial cells (HMEC-1) to detect the modifications induced by cell exposure to benzo[a]pyrene (B[a]P). We used a custom CaF2-based biochip which allowed hyphenated techniques of investigation: surface plasmon resonance imaging (SPRi) to monitor the adsorption of objects, atomic force microscopy (AFM) to characterise EVs' size and morphology, and Raman spectroscopy to detect molecular modifications. Results obtained on EVs by Raman microscopy and tip-enhanced Raman spectroscopy (TERS) showed significant differences induced by B[a]P in the high wavenumber region of Raman spectra (2800 to 3000 cm−1), corresponding mainly to lipid modifications. Two types of spectra were detected in the control sample. A support vector machine (SVM) model was trained on the pre-processed spectral data to differentiate between EVs from cells exposed or not to B[a]P at the spectrum level; this model could achieve a sensitivity of 88% and a specificity of 99.5%. Thus, this experimental setup facilitated the distinction between EVs originating from two cell culture conditions and enabled the discrimination of EV subsets within one cell culture condition. [ABSTRACT FROM AUTHOR]

Early detection of ovarian cancer (OC) is crucial for effective management and treatment, as well as reducing mortality rates. However, the current diagnostic methods for OC are time-consuming and have low accuracy. Surface plasmon resonance (SPR) biosensors offer a promising alternative to conventional techniques, as they enable rapid and less invasive screening of various circulating indicators. These biosensors are widely used for biomolecular interaction analysis and detecting tumor markers, and they are currently being investigated as a rapid diagnostic tool for early-stage cancer detection. Our main focus is on the fundamental concepts and performance characteristics of SPR biosensors. We also discuss the latest advancements in SPR biosensors that enhance their sensitivity and enable high-throughput quantification of OC biomarkers, including CA125, HE4, CEA, and CA19-9. Finally, we address the future challenges that need to be overcome to advance SPR biosensors from research to clinical applications. The ultimate goal is to facilitate the translation of SPR biosensors into routine clinical practice for the early detection and management of OC. [ABSTRACT FROM AUTHOR]

Based on the surface plasmon resonance imaging (SPRi) instrument, we established a new method of analyzing morphine in urine by processing a calibration curve. According to an inhibition immunoassay, gradient concentration of morphine and morphine-BSA fixed on the chip competitively combine with morphine antibody on the chip. Given the three mathematical models, the data of SPRi signals generated from SPRi with morphine was processed to obtain the calibration curve. Ultrafiltration was used to pretreat blank urine samples with adding morphine, and then investigated the advantages and disadvantages of each model. With a limit detection of 6.57 ng·mL−1, the method and mathematical models can provide robust support for SPRi sensors used in further environmental detection, such as the epidemiological study of sewage.

MicroRNA-21 is a potential cancer biomarker that is highly expressed in many cancer cells. Therefore, it is important to perform highly sensitive detection of miRNA-21. In this study, we designed a surface plasmon resonance imaging (SPRi) sensor based on an AuNPs/Ti3C2 composite for real-time and highly sensitive detection of miRNA-21. The fixation of the capture polyA-DNA probes was completed by the freezing method, which improved the detection efficiency. DNA−AuNPs/Ti3C2 conjugates were added to amplify the SPRi signal. The signal amplification combines the large specific surface area of Ti3C2 and the electronic coupling between the local surface plasmon resonance (LSPR) of AuNPs and the plasmon wave on the surface of the Au chip, thereby enhancing the SPRi response signal. Using this sensing strategy, the detection limit for miRNA-21 can reach 6.13 fM, with a wide dynamic range between 10 fM and 10 nM. In addition, the sensor has excellent selectivity for miRNA-21 and miRNAs with similar sequences, and receives minimal interference when applied to complex matrices. Based on these results, we believe that this study provides a simple and highly sensitive method for miRNA detection, which has great potential for the quantitative detection of miRNA in biomedical research and early clinical diagnosis. [ABSTRACT FROM AUTHOR]

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative viral pathogen in the coronavirus disease 2019 (COVID-19) pandemic, which prompted an immediate global response to the development of vaccines and antiviral therapeutics. Drug repurposing in antiviral therapeutics allows for the rapid advancement of existing clinical candidates and therapies into human clinical trials to be tested as COVID-19 therapies. Screening method for drug repurposing are required to prepare the next emerging infectious diseases. In the present study, surface plasmon resonance imaging (SPRi) technique was used to find drug repositioning candidates by taking SARS-CoV2 as an example. Preventing viral entry is an effective antiviral treatment strategy used early during symptom onset. SARS-CoV-2 enters angiotensin-converting enzyme 2 (ACE2)-expressing cells when the receptor-binding domain of the spike protein on the surface of SARS-CoV-2 binds to ACE2, followed by cleavage at two cut sites by transmembrane protease, serine 2 (TMPRSS2). Therefore, a molecule capable of inhibiting the protease activity of TMPRSS2 could be a valuable antiviral therapy. We evaluated whether it was possible to detect specific binding by measuring interactions of drugs and TMPRSS2. In a result, ulinastatin bound with recombinant TMPRSS2 immobilized on biochips pH-dependently. These results suggested that SPRi can be useful technique to discover drug repositioning candidates without in vitro assay, which contributes to the rapid screening. [ABSTRACT FROM AUTHOR]

Intensity interrogation-based surface plasmon resonance imaging (ISPRi) sensing has a simple schematic design and is the most widely used surface plasmon resonance technology at present. In this study, we report the successful development of a novel high-sensitivity ISPRi biosensor and its application for apoptosis detection in cancer cells. By optimizing the excitation wavelength and excitation angle, we achieved a refractive index resolution (RIR) of 5.20 × 10−6 RIU. Importantly, the biosensor has been tested and validated for high-throughput and label-free detection of activated caspase-3 with its specific inhibitor Z-DEVD-FMK in apoptotic cells. Therefore, this study describes a novel molecular imaging system to monitor apoptosis in cancers for disease diagnosis and/or evaluation of therapeutic efficacy of anti-cancer drugs. [ABSTRACT FROM AUTHOR]

MicroRNA-21 is a potential cancer biomarker that is highly expressed in many cancer cells. Therefore, it is important to perform highly sensitive detection of miRNA-21. In this study, we designed a surface plasmon resonance imaging (SPRi) sensor based on an AuNPs/Ti3C2 composite for real-time and highly sensitive detection of miRNA-21. The fixation of the capture polyA-DNA probes was completed by the freezing method, which improved the detection efficiency. DNA−AuNPs/Ti3C2 conjugates were added to amplify the SPRi signal. The signal amplification combines the large specific surface area of Ti3C2 and the electronic coupling between the local surface plasmon resonance (LSPR) of AuNPs and the plasmon wave on the surface of the Au chip, thereby enhancing the SPRi response signal. Using this sensing strategy, the detection limit for miRNA-21 can reach 6.13 fM, with a wide dynamic range between 10 fM and 10 nM. In addition, the sensor has excellent selectivity for miRNA-21 and miRNAs with similar sequences, and receives minimal interference when applied to complex matrices. Based on these results, we believe that this study provides a simple and highly sensitive method for miRNA detection, which has great potential for the quantitative detection of miRNA in biomedical research and early clinical diagnosis.

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.

Intensity interrogation-based surface plasmon resonance imaging (ISPRi) sensing has a simple schematic design and is the most widely used surface plasmon resonance technology at present. In this study, we report the successful development of a novel high-sensitivity ISPRi biosensor and its application for apoptosis detection in cancer cells. By optimizing the excitation wavelength and excitation angle, we achieved a refractive index resolution (RIR) of 5.20 × 10−6 RIU. Importantly, the biosensor has been tested and validated for high-throughput and label-free detection of activated caspase-3 with its specific inhibitor Z-DEVD-FMK in apoptotic cells. Therefore, this study describes a novel molecular imaging system to monitor apoptosis in cancers for disease diagnosis and/or evaluation of therapeutic efficacy of anti-cancer drugs.

Cell-based Surface Plasmon Resonance imaging (SPRi) with anti-endoglin VHH antibodies microarray on a gold-covered biochip was used to characterize the binding to endoglin expressed on the surface membrane of SC cells. SPRi showed the specific capture of SC cells by the immobilized anti-endoglin VHHs, but not of THP-1 cells that do not express endoglin on their plasmatic membrane. The SPRi reflectivity shifts with SC cells bound by anti-endoglin VHHs ranged from 3.59 to 5.54% (average 4.66 ± 1.18%) and with THP-1 cells from 2.23 to 3.05% (average 2.62 ± 1.32% (p

Rapid detection of microorganisms is a major challenge in the medical and industrial sectors. In a pharmaceutical laboratory, contamination of medical products may lead to severe health risks for patients, such as sepsis. In the specific case of advanced therapy medicinal products, contamination must be detected as early as possible to avoid late production stop and unnecessary costs. Unfortunately, the conventional methods used to detect microorganisms are based on time-consuming and labor-intensive approaches. Therefore, it is important to find new tools to detect microorganisms in a shorter time frame. This review sums up the current methods and represents the evolution in techniques for microorganism detection. First, there is a focus on promising ligands, such as aptamers and antimicrobial peptides, cheaper to produce and with a broader spectrum of detection. Then, we describe methods achieving low limits of detection, thanks to Raman spectroscopy or precise handling of samples through microfluids devices. The last part is dedicated to techniques in real-time, such as surface plasmon resonance, preventing the risk of contamination. Detection of pathogens in complex biological fluids remains a scientific challenge, and this review points toward important areas for future research. [ABSTRACT FROM AUTHOR]

The work reports the combination of basic digital image processing (DIP) techniques and statistical segmentation strategy (SDS) to improve surface plasmon resonance curve (SPRc) and SPR imaging (SPRi) sensors' performance. The SPR image is used for sensing and monitoring biological events in the so-called SPR imaging process. In the traditional SPR process based on the attenuated total reflection (ATR) method, the image is used to create the SPR curve, and the curve features tracking is employed on sensing applications. The SPR curve features are enhanced after the pixels of the SPR image have been processed with low-complexity filters in the spatial domain (brightness, contrast, threshold, and morphological). The bootstrap was used as a statistical processing approach, selecting lines and columns from the image that was less affected by imperfections and noises in the image detector, and consequently reducing the SPR sensor instrumentation disturbances. Experimental tests with reversible binding water-mixture were performed, and both image and statistical processing were reported. The combination of DIP and SDS approaches improves the extraction of the curve features, increasing the performance in terms of resonance position sensitivity to 81%. [ABSTRACT FROM AUTHOR]

One known bis-indole alkaloid-voacamine was isolated from Voacanga africana Stapf and Surface Plasmon Resonance imaging (SPRi) exprement showed that this alkaloid could be combine with Protein Tyrosine Phosphatase1B (PTP1B). Then the PTP1B activity inhibition experiment display that the compound showed an outstanding promoting activity to PTP1B. [ABSTRACT FROM AUTHOR]

[Display omitted] • The prevalence of cancer is a major public health issue, and traditional diagnostic methods are plagued by shortcomings such as invasiveness and limited sensitivity and specificity. • SPR is a promising label-free and real-time detection method with high sensitivity, LOD, and reproducibility in detecting cancer biomarkers. • The detection of breast, colorectal, lung, and prostate cancer has been explored by SPR Biosensor. • Using aptamers, antibodies and nanoparticles, SPR biosensors are being exploited to enhance sensitivity and throughput. • However, limitations remain in the clinical utility of SPR biosensors, technological advancements such as LSPR and SPRi have been explored to overcome these limitations. Cancer is a leading cause of mortality and morbidity globally, with an estimated 10 million cancer-related fatalities and 19 million new cases in 2020 alone. Despite remarkable advancements in cancer diagnosis and treatment, cancer continues to pose a significant public health challenge. Early and accurate identification is a critical approach for substantially minimizing the risk of mortality and thereby improving prognosis. Traditional methods of diagnosis include physical examination, medical history assessment, and imaging, and frequently necessitate biopsy for verification. However, in recent years, the field has witnessed growing enthusiasm for liquid biopsy and biomarker detection due to their minimally invasive nature, presenting an attractive alternative to traditional biopsy methods. These techniques offer the potential to diagnose, predict, and monitor disease status, contributing to a paradigm shift in cancer diagnostics. The SPR biosensing approach testifies to a great potential for quantifying cancer biomarkers and its implementations go beyond the limits of this review. It is a promising tool, providing great analytical information concerning elevated sensitivity, rapid response, limit of detection, and reproducibility using its label-free and real-time method. This review highlights how SPR can be exploited in the field of cancer including breast, lung, colorectal, and prostate cancer, paving its way for diagnostics. It can be considered a novel technique replacing all the conventional methods for protein quantification (e.g., Western blotting, ELISA, etc.). Furtherance in the study of SPR biosensors is carried out by the use of aptamers, antibodies, and nanoparticles improving its sensitivity and throughput. However, the utility of SPR biosensors is still not yet close to healthcare applications on a large scale and is yet to be worked on and explored. Continuous and significant initiatives are persistently underway to overcome fundamental constraints, and various technological developments like LSPR and SPRi are coming to the forefront. The recent advancement in the SPR biosensing approach may indeed be a better alternative than the present-day screening methods, providing comprehensive information on the structure–function relationships and biomolecular interactions. [ABSTRACT FROM AUTHOR]

Complexity of sample preparation decelerate the development of sample-in-answer-out devices for point-of-need nucleic acid amplification testing. Here, we present the consolidation of alkaline poly(ethylene) glycol-based lysis and solid-phase extraction for rapid and simple sample preparation compatible with direct on-bead amplification. Simultaneous cell lysis and binding of DNA were achieved using an optimised reagent comprising 15% PEG8000, 0.5 M NaCl, and 3.5 mM KOH. This was combined with direct, on-bead amplification using 1.5 μg beads per 20 μL PCR reaction mix. The novel single reagent, 5-min method improved the detection limit by 10 and 100-fold compared with commercial DNA extraction kits and the original alkaline PEG lysis method, respectively. The sensitivity can be further enhanced by one amplification cycle with an ethanol wash or by extending the incubation to 10 min before collecting the magnetic particles. Both methods successfully detected a single copy of Escherichia coli DNA. In biological fluids (saliva, sweat, and urine), the 5-min method was delayed by about one cycle compared to the 15-min method. The proposed methods are attractive for incorporation in the workflow for point-of-need testing of biological samples by providing a practical and chemical method for simple alternative DNA sample preparation. [Display omitted] • First report of dual-purpose reagent for one-step lysis and extraction of DNA. • ASAP reagent is compatible with direct, on bead amplification. • ASAP method provides 10 to 100-fold enhancement in sensitivity. • ASAP method minimizes manual handling and equipment needs. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the affinity of a bis-indole alkaloid - voacamine from Voacanga Africana Stapf for IL-2Ra - and its immunosuppressive effect on concanavalin A-induced T cell proliferation and lipopolysaccharide -induced B cell proliferation in vitro. Methods: Surface plasmon resonance imaging (SPRi) was used to screen the target protein of voacamine, while CCK-8 kit was used to evaluate cytotoxicity. Mitogen-induced proliferation assay was carried out to assess the inhibitory effect of voacamine on Con A-induced T cell proliferation and LPSinduced B cell proliferation. The binding characteristics of voacamine were investigated using a binding model with IL-2Ra constructed based on molecular docking simulation. Results: Voacamine had a high-affinity for IL-2Ra with an equilibrium dissociation constant (KD) of 1.85×10-8 M. Cytotoxicity data showed that voacamine did not exhibit cytotoxicity at concentrations lower than 0.32 µM. However, it exerted significant immunosuppressive effect on B cells at a lower concentration, but had no influence on proliferation of T cells. Autodock results indicate that voacamine has a good interaction with the enzyme active site. Conclusion: Voacamine and its analogues exert influence on the immune system. [ABSTRACT FROM AUTHOR]

Functional amyloids are commonly produced by many microorganisms and their biological functions are numerous. Staphylococcus aureus can secrete a group of peptides named phenol-soluble modulins (PSMs) in their biofilm extracellular matrix. PSMs have been found inside biofilms both in their soluble form and assembled into amyloid structures. Yet, the actual biological function of these amyloids has been highly debated. Here, we assessed the ability of PSMs to form amyloids in contact with different abiotic surfaces to unravel a potential unknown bioadhesive and/or biofilm stabilization function. We combined surface plasmon resonance imaging, fluorescence aggregation kinetics, and FTIR spectroscopy in order to evaluate the PSM adsorption as well as amyloid formation properties in the presence of various surface chemistries. Overall, PSMs adsorb even on low-binding surfaces, making them highly adaptable adsorbants in the context of bioadhesion. Moreover, the PSM aggregation potential to form amyloid aggregates is not impacted by the presence of the surface chemistries tested. This versatility regarding adsorption and amyloid formation may imply a possible role of PSMs in biofilm adhesion and/or structure integrity. • Phenol-soluble modulins can adsorb on highly different surface chemistries. • This adsorption versatility makes PSMs potential bioadhesion markers. • The amyloid formation of PSMs seems independent of surface chemistry. • A biological function for amyloid PSMs remains elusive. [ABSTRACT FROM AUTHOR]

In this paper we propose an easy way to detect the glycated form of human serum albumin which is biomarker for several diseases such as diabetes and Alzheimer. The detection platform is a label free impedimetric immunosensor, in which we used a monoclonal human serum albumin antibody as a bioreceptor and electrochemical impedance as a transducing method. The antibody was deposited onto a gold surface by simple physisorption technique. Bovine serum albumin was used as a blocking agent for non-specific binding interactions. Cyclic voltammetry and electrochemical impedance spectroscopy were used for the characterization of each layer. Human serum albumin was glycated at different levels with several concentrations of glucose ranging from 0 mM to 500 mM representing physiological, pathological (diabetic albumin) and suprapathological concentration of glucose. Through the calibration curves, we could clearly distinguish between two different areas related to physiological and pathological albumin glycation levels. The immunosensor displayed a linear range from 7.49% to 15.79% of glycated albumin to total albumin with a good sensitivity. Surface plasmon resonance imaging was also used to characterize the developed immunosensor. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance imaging (SPRi) is a label-free, non-invasion detection method that allows real-time analysis for biomolecular interactions with high sensitivity and high throughput. Cellular analysis and detection is significant in many research areas, including healthcare, food safety, environmental and agricultural monitoring, as well as for the application of SPRi. This review summarizes the utilization of SPRi for cellular analysis and detection in the last decade and illustrates the boundless potential of the SPRi technique in these fields. [ABSTRACT FROM AUTHOR]

A gold-silver alloy film based spectral surface plasmon resonance imaging (SPRi) sensor has been prepared for in-situ quantitative detection of biochemical analytes at the sensor surface. This novel sensor has lower detection cost yet higher sensitivity relative to the conventional counterpart with a gold film. Using the laboratory-made multifunctional SPR sensing platform, both the resonant color images and the resonant spectra for the Au-Ag alloy film were measured at different incident angles. The quantitative relationship between the resonant wavelength and the average hue of corresponding resonant color image was established. With this relationship the most hue-sensitive spectral range was determined. After setting the initial resonant wavelength in the hue-sensitive spectral range, the refractive-index sensitivity of the Au-Ag alloy film based SPRi sensor was measured as Δhue/Δnc = 29,879/RIU, being 8 times higher than that obtained with the gold-film SPRi sensor. The immunodetection of benzo(a)pyrene (BaP) in water was fulfilled using the Au-Ag alloy film based SPRi sensor. The average hue of the SPR color image linearly increases with increasing the BaP concentration up to C = 0.5 μg/L and the slope is Δhue/ΔC = 132.2/(μg/L). The sensor is responsive to a change of BaP concentration as low as ΔC = 0.01 μg/L.

Listeria monocytogenes is one of the major foodborne pathogen found in a large set of foodstuff. With the aim of decreasing listeriosis occurrence, the early detection of this pathogen in food products is of tremendous interest. So far, the reference method and all the alternative methods require a pre-enrichment step lasting 24 h to several days. Then, an aliquot of the enriched sample is collected and characterized according different methods including genetic analysis, or beads immuno-agglutination. With the aim of significantly decreasing the overall processing time, we propose an approach involving the detection of alive bacteria during their growing phase via the use of an immuno-chip SPR imaging process. Listeria specific antibodies were also produced and chemically grafted on the biochip before being selected for their ability to distinguish different Listeria strains. Finally, this approach allows the detection of a very low number of L. monocytogenes present in foodstuff. [ABSTRACT FROM AUTHOR]

Abciximab (Abci) and eptifibatide (Epti) are antiaggregate drugs which may reduce thrombotic complications inacute coronary syndromes. The aim of this work was the investigation of the interaction between the phospholipid-GPIIb/IIIa glycoprotein complex and Abci or Epti, and the influence of these drugs on the phospholipid ratio in the plateletmembrane. The interaction between the phospholipid-GPIIb/IIIa glycoprotein complex and antiaggregate drugs were investigatedusing the Surface Plasmon Resonance Imaging technique (SPRI). Phospholipids phosphatidylinositol (PI), phosphatidylserine(PS), phosphatidylethanolamine (PE), phosphatidylcholine (PC) and sphingomyelin (SM) were first immobilizedonto the gold chip surface. The phospholipid ratio in the platelet membrane was determined by the HPLC. Only PI,PS, PE and PC were determined. Human platelets treated 'in vitro' with Abci or Epti exhibit changes in the phospholipidratio in the platelet membrane. The ratio of PS decreases and PC rises. The SPRI distinctly shows interactions between phospholipidsand glycoprotein GPIIb/IIIa, and between the phospholipid-glycoprotein GPIIb/IIIa complex and Abci or Epti.The interaction between phospholipids and glycoprotein GPIIb/IIIa is growing in the sequence: PI<

Timely and accurate mapping of paddy rice cultivation is needed for maintaining sustainable rice production, ensuring food security, and monitoring water usage. Synthetic Aperture Radar (SAR) remote sensing plays an important role in the continuous monitoring and mapping of rice cultivation in cloudy regions since it is not affected by weather conditions. To date, most SAR imagery-based rice mapping methods rely on prior knowledge (e.g., the planting date) and empirical thresholds for specific regions, which limits their applications in large spatial scales. To tackle this limitation, this study proposed a new SAR-based Paddy Rice Index (SPRI) to quantify the probability of land patches planted paddy rice. SPRI fully uses unique features of paddy rice during the transplanting-vegetative period in the Sentinel-1 VH backscatter time series. With the assistance of cloud-free Sentinel-2 images, SPRI can be calculated for each cropland object with adaptive parameters. Then, SPRI values of cropland objects can be converted to paddy rice maps using the binary-classification threshold. The proposed SPRI method was tested at five sites with diverse climate conditions, landscape complexity and cropping systems. Results show that the SPRI was able to produce an accurate classification map with an overall accuracy of over 88% and an F1 score of over 0.86 at all sites. Compared with the existing SAR-based rice mapping methods, our method performed much better in heterogeneous agricultural areas where rice is mosaiced with other crops. As SPRI does not need any prior knowledge, reference samples and many predefined parameters, it has high flexibility and applicability to support paddy rice mapping in large areas, especially for cloudy regions where optical remote sensing data is often not available. • A SAR-based Paddy Rice Index (SPRI) was proposed. • SPRI uses unique features of paddy rice during the transplanting-vegetative period. • SPRI quantifies the probability of paddy fields in cropland patches. • SPRI can balance omission and commission error over different sites. • SPRI mitigates the site difference using regional adaptive parameters. [ABSTRACT FROM AUTHOR]

ABSTRACT: Biomarker measurements are essential for the early diagnosis of complex diseases. However, many current biomarker assays lack sensitivity and multiplexing capacity, work in a narrow detection range and importantly lack real time quality control opportunities, which hampers clinical translation. In this paper, we demonstrate a toolbox to kinetically characterize a biomarker measurement assay using Surface Plasmon Resonance imaging (SPRi) with ample opportunities for real time quality control by exploiting quantitative descriptions of the various biomolecular interactions. We show an accurate prediction of SPRi measurements at both low and high concentrations of various analytes with deviations <5% between actual measurements and predicted measurement. The biphasic binding sites model was accurate for fitting the experimental curves and enables optimal detection of heterophilic antibodies, cross-reactivity, spotting irregularities and/or other confounders. The toolbox can also be used to create a (simulated) calibration curve, enabling calibration-free measurements with good recovery, it allows for easy assay optimizations, and could help bridge the gap to bring new biomarker assays to the clinic. [Display omitted] • Kinetic characterization of SPR interactions allow for extensive quality control. • SPRi cascade measurements can be predicted with deviations <5%. • Optimal detection of cross-reactivity, spotting irregularities and other confounders. • Simulated calibration curve enables calibration-free quantification. • Simulating assay conditions enables signal and assay time optimization. [ABSTRACT FROM AUTHOR]

The purpose of this paper is shows some design parameters of a series resonant inverter (SRI) half-bridge configuration applied in lamps, this circuit is novel compared with the inverter resonant in series-parallel circuit (SPRI), in actuality the resonant inverters SPRI are very used to supply the power needed in fluorescent lamps, . In order to analyze the behavior and efficiency, is implemented a circuit SRI to supply the energy needed in a 32 W fluorescent lamp. The final results show a better efficiency with the proposed circuit compared to a classical SPRI. [ABSTRACT FROM AUTHOR]

Professor Marco Mascini was an internationally acknowledged scientist, teacher of generations of chemists. He passed away on May 12 2015 at the age of 75. During his scientific carrier he made outstanding and innovative contributions to analytical chemistry, especially in the interdisciplinary field of sensors and biosensors. This paper presents an overview of Prof. Mascini's scientific interests and accomplishments in his career that testify the pivotal role of this scientist in the modern analytical chemistry. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance imaging (SPRi) is a label-free detection method that offers a suitable and reliable platform for the real time monitoring of biomolecular interactions. In the work reported here, SPRi was used to evaluate the affinity and specificity of three different aptamers selected against the Lup an 1 anaphylactic allergen β-conglutin (β-conglutin binding aptamers I and II (β-CBA I and β-CBA II)), as well as an 11-mer truncated version of β-CBA I. Thiol modified aptamers were immobilised on a gold substrate through a self-assembling process and the use of different blocking strategies to prevent non-specific binding were evaluated. Dissociation constants of 20, 13 and 1 nM were determined for β-CBA I, β-CBA II and the 11-mer truncated aptamer, respectively. The three aptamers were then studied in various different sandwich formats and the β-CBA I/11-mer and β-CBA II were observed to bind to different aptatopes on the target protein. Each of the aptamers were then used either as surface immobilised aptamer, or as reporter aptamer, and added with the protein target β-conglutin in either a sequential of simultaneous manner, and the changes in SPR signal monitored. The preferred approach for formation of a sandwich aptacomplex was with immobilised β-CBA II, followed by addition of pre-incubated β-conglutin and 11-mer, whilst addition of the 11-mer following addition of the β-conglutin, resulted in displacement of the bound target. The ability to provide parallel qualitative and quantitative detection establishes SPRi as a powerful tool for the study of immobilised aptamer–target interactions. [ABSTRACT FROM AUTHOR]

In the present report, we are making the proof of concept of cell small populations (from 1 to 100 cells) spotting, culture and secretion detection on a gold surface. In order to keep the cells in a hydrated environment during the robotized micropipetting and to address different cell lines on a single chip, a biocompatible alginate polymer was used. This approach enables the encapsulation of the cell in a very small volume (30 nL), directly on the substrate and permits a precise control of the number of cells in each alginate bead. After 24 h of culture, the adherent cells are ready for surface plasmon resonance imaging (SPRi) experimentation. To enable the detection of secreted proteins, various antibodies are immobilized in an organized manner on a SPRi sensor and permitted the multiplex detection of different proteins secreted by the different cultured cell lines. Evidence of the real-time detection will be presented for Prostate Specific Antigen (PSA) and β-2-microglobulin (B2M) secreted by prostate cancer cells following induction by dihydrotestosterone (DHT). Different kinetics for the two secreted proteins were then demonstrated and precisely determined using the chip. [ABSTRACT FROM AUTHOR]

Adenovirus infection, which is a waterborne viral disease, is one of the most prevelant causes of human morbidity in the world. Thus, methods for rapid detection of this infectious virus in the environment are urgently needed for public health protection. In this study, we developed a rapid, real-time, sensitive, and label-free SPRi-based biosensor for rapid, sensitive and highly selective detection of adenoviruses. The sensing protocol consists of mixing the sample containing adenovirus with a predetermined concentration of adenovirus antibody. The mixture was filtered to remove the free antibodies from the sample. A secondary antibody, which was specific to the adenovirus antibody, was immobilized onto the SPRi chip surface covalently and the filtrate was flowed over the sensor surface. When the free adenovirus antibodies bound to the surface-immobilized secondary antibodies, we observed this binding via changes in reflectivity. In this approach, a higher amount of adenoviruses resulted in fewer free adenovirus antibodies and thus smaller reflectivity changes. A dose–response curve was generated, and the linear detection range was determined to be from 10 PFU/mL to 5000 PFU/mL with an R 2 value greater than 0.9. The results also showed that the developed biosensing system had a high specificity towards adenovirus (less than 20% signal change when tested in a sample matrix containing rotavirus and lentivirus). [ABSTRACT FROM AUTHOR]

Surface plasmon resonance imaging (SPRi) is most frequently used for the label-free measurement of biomolecular interactions. Here we explore the potential of SPRi to measure antibody production of individual hybridoma cells. As a model system, cells from a hybridoma, producing monoclonal antibodies recognizing epithelial cell adhesion molecule (EpCAM), were used. Recombinant human EpCAM protein was immobilized on an SPR sensor and hybridoma cells were introduced into an IBIS MX96 SPR imager and the SPRi response was followed for 10 h. SPRi responses were detected on the spots of the sensor only where ligands of the produced antibody were present. By measuring the SPRi signals on individual cells the antibody production of the individual cells was measured and production rates were calculated. For 53 single EpCAM hybridoma cells the production ranged from 0.16 to 11.95 pg (mean 2.96 pg per cell, SD 2.51) over a period of 10 h. Antibody excretion per cell per hour ranged from 0.02 to 1.19 pg (mean 0.30, SD 0.25). Here we demonstrate for the first time that antibody production of individual cells can be measured and quantified by SPRi, opening a new avenue for measuring excretion products of individual cells. [ABSTRACT FROM AUTHOR]

Peptides ligands with high affinity and high specificity towards specific targets is catching a good deal of interests in biomedical field. Traditional peptide screening procedure involves selection, sequencing and characterization and each step is time-consuming and labor-intensive. The combination between different analytical methods could provide an integrated plan for efficient peptide screening. We report herein a label-free detection microarray system to facilitate the whole one-bead-one-compound (OBOC) peptide screening process. A microwell array chip with two identical units can trap the candidate peptide beads in one-well-one-bead manner. Peptides on beads were photo-released in situ in the well and partly transferred to two identical chips for Surface Plasmon Resonance imaging (SPRi), and peptide left in the bi-unit microwell array chip was remain for in situ single bead sequencing by matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS). Using the bi-unit imprinted chip system, affinity peptides towards AD protein were efficiently screened out both qualitatively and quantitatively from 10 4 candidates. The method provides a universal solution for high efficiency and high throughput ligands screening. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance imaging (SPRi) has emerged as a versatile biosensor to detect a wide range of biomolecular interactions with divergent potential applications. However, the use of this advanced-level technology for stem cell lysate study is still not much explored. Cell lysates are significant biological analytes used for disease diagnostics and proteomic studies, but their complex nature limits their use as an analyte for SPRi biosensors. Here, we review the problems associated with the use of SPRi for stem cell lysate study and examine the role of surface chemistry, running buffer, and blocking solution in order to minimize nonspecific adsorption (NSA). We detect the expression of Oct4, Sox2, Nanog, Rex1, and Lin28 biomarkers present in mouse embryonic stem cell (mESC) lysate against their corresponding antibodies immobilized on the sensor surface with reduced NSA. The current study shows that the conjunction of SPRi and microarray can be used as a label-free, high-throughput, and rapid technique for detection of biomarkers and their relative abundance in stem cell lysate study. [ABSTRACT FROM AUTHOR]

Here the feasibility is demonstrated that by combining Surface Plasmon Resonance Imaging (SPRi) and self-sorting microwell technology product secretion of individual cells can be monitored. Additionally isolation of the selected cells can be performed by punching the cells from the microwells using coordinates of the positions of microwells obtained with SPRi. Cells of interest can be retrieved sterile from the microwell array for further cultivation. [ABSTRACT FROM AUTHOR]

In the present report, we are making the proof of concept of cell small populations (from 1 to 100 cells) spotting, culture and secretion detection on a gold surface. In order to keep the cells in a hydrated environment during the robotized micropipetting and to address different cell lines on a single chip, a biocompatible alginate polymer was used. This approach enables the encapsulation of the cell in a very small volume (30 nL), directly on the substrate and permits a precise control of the number of cells in each alginate bead. After 24 h of culture, the adherent cells are ready for surface plasmon resonance imaging (SPRi) experimentation. To enable the detection of secreted proteins, various antibodies are immobilized in an organized manner on a SPRi sensor and permitted the multiplex detection of different proteins secreted by the different cultured cell lines. Evidence of the real-time detection will be presented for Prostate Specific Antigen (PSA) and β-2-microglobulin (B2M) secreted by prostate cancer cells following induction by dihydrotestosterone (DHT). Different kinetics for the two secreted proteins were then demonstrated and precisely determined using the chip.

Lectin microarrays have emerged as a novel platform for glycan analysis during recent years. Here, we have combined surface plasmon resonance imaging (SPRi) with the lectin microarray for rapid and label-free profiling of stem cells. In this direction, 40 lectins from seven different glyco-binding motifs and three different cell lines—mouse embryonic stem cells (mESCs), mouse-induced pluripotent stem cells (miPSCs), and mouse embryonic fibroblast stem cells (MEFs)—were used. Pluripotent mouse stem cells were clearly distinguished from non-pluripotent stem cells. Eight lectins—DBA, MAL, PHA_E, PHA_L, EEL, AAL, PNA, and SNA—generated maximal value to define pluripotency of mouse stem cells in our experiments. The discriminant function based on lectin reactivities was highly accurate for the determination of stem cell pluripotency. These results suggested that glycomic analysis of stem cells leads to a novel comprehensive approach for quality control in cell-based therapy and regenerative medicine. [ABSTRACT FROM AUTHOR]

Echinomycin, a member of the quinoxaline family of antibiotics, is known to be a small-molecule inhibitor of hypoxia inducible factor–1 (HIF-1) DNA binding activity. Recently, it has been shown to suppress mammalian target of rapamycin (mTOR) signaling and growth in leukemia cell lines. In this study, we investigated whether echinomycin interacts with the FKBP12 protein. Molecular docking was used, and the predicted binding energy was −10.61 kcal/mol. Moreover, surface plasmon resonance imaging and fluorescence quenching techniques were used to validate this interaction. Echinomycin binds to FKBP12 with a strong binding affinity comparable with rapamycin. Furthermore, the echinomycin-FKBP12 complex has been shown to affect calcineurin activity when tested in a calcineurin phosphatase inhibition assay. All of these studies have shown that echinomycin may have a double impact on HIF signaling by direct inhibition and through mTOR. [ABSTRACT FROM PUBLISHER]

Surface Plasmon Resonance Imaging (SPRi) and the Quartz Crystal Microbalance (QCM) technique were used to characterize the interactions between fibronectin and a specific monoclonal antibody against fibronectin. These techniques were used to investigate the formation of successive layers of the biosensor and how they affect the biosensor's response. The analytical response of both detectors to fibronectin concentration is linear in the range 5–100 ng/mL. The changes in mass on the surface of a quartz crystal covered with a layer of gold during biosensor formation were investigated with a QCM. The equilibrium constant was determined to be K C = 1.22∙108 dm3/mol and the dissociation constant to be K D = 8.20 ∙ 10−9 mol/dm3. • The equilibrium constant and the dissociation constant of the fibronectin-antibody complex were determined. • QCM and SPRi were used during the research. • The formation of successive layers of the biosensor was investigated by means of QCM. • WinSpall version 3.02 was used to determine the SPR curves. [ABSTRACT FROM AUTHOR]

Abstract: Microarrays of peptide and recombinant protein libraries are routinely used for high-throughput studies of protein–protein interactions and enzymatic activities. Imaging mass spectrometry (IMS) is currently applied as a method to localize analytes on thin tissue sections and other surfaces. Here, we have applied IMS as a label-free means to analyze protein–peptide interactions in a microarray-based phosphatase assay. This IMS strategy visualizes the entire microarray in one composite image by collecting a predefined raster of matrix-assisted laser desorption/ionization time-of-flight (MALDI–TOF) mass spectrometry spectra over the surface of the chip. Examining the bacterial tyrosine phosphatase YopH, we used IMS as a label-free means to visualize enzyme binding and activity with a microarrayed phosphopeptide library printed on chips coated with either gold or indium–tin oxide. Furthermore, we demonstrate that microarray-based IMS can be coupled with surface plasmon resonance imaging to add kinetic analyses to measured binding interactions. The method described here is within the capabilities of many modern MALDI–TOF instruments and has general utility for the label-free analysis of microarray assays. [Copyright &y& Elsevier]

Abstract: Objective: To determine the concentrations of cathepsins B, D and G in proliferative eutopic endometrium of patients with and without endometriosis, by use of the surface plasmon resonance imaging (SPRI) technique. Study design: A total of 55 patients were recruited in the study: 31 patients with endometriosis (stages I–IV) and 24 controls. Endometrial samples were obtained in the first phase of the menstrual cycle from regularly menstruating premenopausal women, prior to laparoscopy, by the use of aspiration biopsy. Endometriosis was appropriately classified according to the Revised American Fertility Society classification and confirmed by histopathology in every case. The SPRI technique was used to determine the concentration of cathepsins B, D and G. To compare the two groups for quantitative data, Mann–Whitney–Wilcoxon's test was used due to the non-normal distribution of the tested variables and normality of distribution was assessed using Shapiro–Wilk W test. Results: The concentration of the three examined cathepsins was higher in the proliferative eutopic endometrium of patients with endometriosis, especially in advanced stages, e.g. III and IV, when compared to healthy individuals. Corresponding median values were, for cathepsin B: [7.93pmol/mg (min–max 2.82–15.71) vs 1.2pmol/mg (min–max 0.7–15.49) p =0.0014], for cathepsin D: [1.86pmol/mg (min–max 0.51–5.4) vs 1.03pmol/mg (min–max 0.4–2.72) p =0.00041] and for cathepsin G: [0.6pmol/mg (min–max 0.33–2.51) vs 0.3pmol/mg (min–max 0.16–1.29) p =0.00051]. Conclusions: Increased concentrations of cathepsins B, D and G in the proliferative eutopic endometrium may play a role in the implantation of endometrial tissue outside the uterine cavity. [Copyright &y& Elsevier]

The electrografting of aryl-diazonium was proven to be an efficient way to immobilize antibodies, oligonucleotides and enzymes onto conductive supports. Biomolecules chemically functionalized with aniline derivates or diazotated derivates could be used to build complex architectures acting as sensing layers for biosensors, biochips or others bioelectronic devices. Additionally, the use of SPR offers new opportunities to characterize the grafted surfaces as well as to develop label-free assays. Here, we give an overview of our group achievements in the field during the last 7 years. We highlight the applications of these functionalized surfaces in multiparametric sandwich assays, in the label free detection and imaging of macromolecular interactions by SPRi and in the immobilization of dehydrogenase via its cofactor. [ABSTRACT FROM AUTHOR]

In this work, we present a method to produce micro and nanostructured surfaces containing bioadhesive features embedded in an antifouling matrix. These surfaces are fabricated by combining plasma polymerization and electron beam lithography. This combination allows the fabrication of structured surfaces in just two steps and without the use of solvents. ToF-SIMS analysis demonstrates that the e-beam treatment induces a chemical change at the surface depending upon the radiation dose employed. In particular, a decrease of peaks characteristic of the PEO-like fragments (e.g. CH3O+, C3H7O+, C3H5O2+) and a correspondent increase of hydrocarbon moieties such as C2H3+ and C3H3+ is observed in the irradiated zones. These results are supported by XPS analysis that indicate a slight reduction of the intensity of the C-O component in the C1s core level spectrum after irradiation similar to that observed in UV-treated PEO-like films. Experiments with proteins show a preferential adhesion of the biomolecules to the irradiated zone indicating the good potential of this technique for the development of nanostructured biosensing platforms. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Podoplanin (PDP) is a small transmembrane protein and widely present in various specialized cells throughout the human body. It is a specific marker for identification of lymphatic vessel and a candidate marker for cancer stem cells in squamous cell carcinoma of the lung. We report on method for the highly selective determination of PDP by using a surface plasmon resonance imaging (SPRI) that exploits the highly selective interaction between PDP and anti-human PDP monoclonal antibody (IgG). The sensor has a dynamic range between 0.25 and 1.0 ng mL, and a detection limit of 15 pg mL. It was applied to the determination of PDP in blood plasma and tissue homogenates from paired normal and lung tumor tissue. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]