Design and fabrication of a low-cost wireless camera imaging system for centrifugal microfluidics

Centrifugal microfluidic devices offer a robust method for low-volume fluid handling by combining low-cost instrumentation with highly integrated automation. Crucial to the efficacy of Lab-on-a-Disc (LoaD) device operation is the selection of robust valving technology, the design of on-disc fluidic structures, and accurate control of disc spin-speeds (centrifugal force) during operation. The design and refinement of fluidic and valving structures is often guided by inspecting disc operation using high-speed camera systems. This approach involves synchronising image acquisition with disc rotation to visualise liquid flow through a series of images often presented in a video format. Depending on the decisions taken, such systems can cost from €4,000 upwards. This paper outlines the development of a low-cost centrifugal test-stand with an integrated imaging system using a generic wireless camera to record videos directly to a smartphone device. This imaging system can be fabricated using only 3D printers and a low-cost CNC milling machine from widely available materials for approximately €350. High-fidelity imaging of the entire disc for flow visualisation and the recording of real-time colour intensity measurements are facilitated by this standalone device. A vibration analysis study has been performed to determine the rotational velocity range at which the system can be safely operated. Furthermore, the efficacy of the imaging system has been demonstrated by performing real-time colour intensity measurements of dyed water dilutions.

Antibody Purification Using Affinity Chromatography

Antibodies are an integral part of many biological assays and biotherapeutics. However, the sources from which antibodies are derived frequently contain other contaminants which may interfere with assays or cause adverse reactions if administered in vivo. Therefore, a means of isolating these antibodies from their source at high levels of purity is critical. Affinity chromatography is currently one of the most widely applied methods for the purification of antibodies. This method relies on specific and reversible, interactions between antibody structures, or recombinant tags fused to these structures, and ligands immobilized on solid support matrices, generally within a column. Herein, common chromatographic methods applied to antibody purification are described. These include the purification of IgG, and its recombinant forms, through protein A, protein G and immobilized metal affinity chromatography.

A one-step reverse transcription recombinase polymerase amplification assay for lateral flow-based visual detection of PVY

Potato virus Y (PVY) is an abundant and damaging virus which reduces crop yield and marketability. Accurate detection of this economically important virus both in-field and in seed potato is considered essential in the control of PVY spread. Current detection methods are focused on immunodetection and PCR-based methods, however, identification of PVY through isothermal amplification is a promising avenue for developing accessible, on-site diagnostics with quick turnaround times. In this work, a rapid recombinase polymerase amplification assay was developed which could readily amplify PVY nucleic acids with good sensitivity and specificity. Additionally, this assay was shown to be capable of amplification directly from RNA in a one-step amplification process, without the need for prior reverse transcription. The assay was coupled with lateral flow technology to provide a rapid visual confirmation of amplification. This nucleic-acid lateral flow immunoassay could feasibly be employed in-field, or at any location where testing is required, to aid in the detection and control of PVY.

Generation, selection and modification of anti-cardiac troponin I antibodies with high specificity and affinity

Current diagnosis of acute myocardial infarction involves quantification of circulating cTn levels. This work endeavoured to generate and enhance recombinant antibody fragments targeting various epitopes on the N- and C-terminals of the cTnI molecule, thereby facilitating highly sensitive detection of the troponin molecule. From this approach, two anti-cTnI scFv antibodies were successfully selected using either phage display or structural reformatting of full length anti-cTnI IgG. Their antibody binding affinity was further optimised via chain shuffling and/or site directed mutagenesis, resulting in scFv with heightened sensitivity when compared to the wild-type scFv. If used in conjunction with existing anti-mid fragment cTnI antibodies, these N- and C- terminal-targeting scFvs show high potential for the enhancement of current cTnI detection assays by limiting the effects from cTnI degradation or troponin complex formation.

Advances in point-of-care testing for cardiovascular diseases

Point-of-care testing (POCT) is a specific format of diagnostic testing that is conducted without accompanying infrastructure or sophisticated instrumentation. Traditionally, such rapid sample-to-answer assays provide inferior analytical performances to their laboratory counterparts when measuring cardiac biomarkers. Hence, their potentially broad applicability is somewhat bound by their inability to detect clinically relevant concentrations of cardiac troponin (cTn) in the early stages of myocardial injury. However, the continuous refinement of biorecognition elements, the optimization of detection techniques, and the fabrication of tailored fluid handling systems to manage the sensing process has stimulated the production of commercial assays that can support accelerated diagnostic pathways. This review will present the latest commercial POC assays and examine their impact on clinical decision-making. The individual elements that constitute POC assays will be explored, with an emphasis on aspects that contribute to economically feasible and highly sensitive assays. Furthermore, the prospect of POCT imparting a greater influence on early interventions for medium to high-risk individuals and the potential to re-shape the paradigm of cardiovascular risk assessments will be discussed.

The role of antibody-based troponin detection in cardiovascular disease: A critical assessment

Cardiovascular disease has remained the world's biggest killer for 30 years. To aid in the diagnosis and prognosis of patients suffering cardiovascular-related disease accurate detection methods are essential. For over 20 years, the cardiac-specific troponins, I (cTnI) and T (cTnT), have acted as sensitive and specific biomarkers to assist in the diagnosis of various types of heart diseases. Various cardiovascular complications were commonly detected in patients with COVID-19, where cTn elevation is detectable, which suggested potential great prognostic value of cTn in COVID-19-infected patients. Detection of these biomarkers circulating in the bloodstream is generally facilitated by immunoassays employing cTnI- and/or cTnT-specific antibodies. While several anti-troponin assays are commercially available, there are still obstacles to overcome to achieve optimal troponin detection. Such obstacles include the proteolytic degradation of N and C terminals on cTnI, epitope occlusion of troponin binding-sites by the cTnI/cTnT complex, cross reactivity of antibodies with skeletal troponins or assay interference caused by human anti-species antibodies. Therefore, further research into multi-antibody based platforms, multi-epitope targeting and rigorous validation of immunoassays is required to ensure accurate measurements. Moreover, with combination and modification of various latest technical (e.g. microfluidics), antibody-based troponin detection systems can be more specific, sensitive and rapid which could be incorporated into portable biosensor systems to be used at point-of care.

Antibody stability: A key to performance - Analysis, influences and improvement

An antibody's stability greatly influences its performance (i.e. its specificity and affinity). Thus, stability is a major issue for researchers and manufacturers, especially with the increasing use of antibodies in therapeutics, diagnostics and rapid analytical platforms. Here we review antibody stability under five headings: (i) measurement techniques; (ii) stability issues in expression and production (expression, proteolysis, aggregation); (iii) effects of antibody format and engineering on stability and (iv) formulation, drying and storage conditions. We consider more than 100 sources, including patents, and conclude with (v) recommendations to promote antibody stability.

Evaluation of Molecularly Imprinted Polymers for Point-of-Care Testing for Cardiovascular Disease

Molecular imprinting is a rapidly growing area of interest involving the synthesis of artificial recognition elements that enable the separation of analyte from a sample matrix and its determination. Traditionally, this approach can be successfully applied to small analyte (<1.5 kDa) separation/ extraction, but, more recently it is finding utility in biomimetic sensors. These sensors consist of a recognition element and a transducer similar to their biosensor counterparts, however, the fundamental distinction is that biomimetic sensors employ an artificial recognition element. Molecularly imprinted polymers (MIPs) employed as the recognition elements in biomimetic sensors contain binding sites complementary in shape and functionality to their target analyte. Despite the growing interest in molecularly imprinting techniques, the commercial adoption of this technology is yet to be widely realised for blood sample analysis. This review aims to assess the applicability of this technology for the point-of-care testing (POCT) of cardiovascular disease-related biomarkers. More specifically, molecular imprinting is critically evaluated with respect to the detection of cardiac biomarkers indicative of acute coronary syndrome (ACS), such as the cardiac troponins (cTns). The challenges associated with the synthesis of MIPs for protein detection are outlined, in addition to enhancement techniques that ultimately improve the analytical performance of biomimetic sensors. The mechanism of detection employed to convert the analyte concentration into a measurable signal in biomimetic sensors will be discussed. Furthermore, the analytical performance of these sensors will be compared with biosensors and their potential implementation within clinical settings will be considered. In addition, the most suitable application of these sensors for cardiovascular assessment will be presented.

Point-of-Care Compatibility of Ultra-Sensitive Detection Techniques for the Cardiac Biomarker Troponin I-Challenges and Potential Value

Cardiac biomarkers are frequently measured to provide guidance on the well-being of a patient in relation to cardiac health with many assays having been developed and widely utilised in clinical assessment. Effectively treating and managing cardiovascular disease (CVD) relies on swiftly responding to signs of cardiac symptoms, thus providing a basis for enhanced patient management and an overall better health outcome. Ultra-sensitive cardiac biomarker detection techniques play a pivotal role in improving the diagnostic capacity of an assay and thus enabling a better-informed decision. However, currently, the typical approach taken within healthcare depends on centralised laboratories performing analysis of cardiac biomarkers, thus restricting the roll-out of rapid diagnostics. Point-of-care testing (POCT) involves conducting the diagnostic test in the presence of the patient, with a short turnaround time, requiring small sample volumes without compromising the sensitivity of the assay. This technology is ideal for combatting CVD, thus the formulation of ultra-sensitive assays and the design of biosensors will be critically evaluated, focusing on the feasibility of these techniques for point-of-care (POC) integration. Moreover, there are several key factors, which in combination, contribute to the development of ultra-sensitive techniques, namely the incorporation of nanomaterials for sensitivity enhancement and manipulation of labelling methods. This review will explore the latest developments in cardiac biomarker detection, primarily focusing on the detection of cardiac troponin I (cTnI). Highly sensitive detection of cTnI is of paramount importance regarding the rapid rule-in/rule-out of acute myocardial infarction (AMI). Thus the challenges encountered during cTnI measurements are outlined in detail to assist in demonstrating the drawbacks of current commercial assays and the obstructions to standardisation. Furthermore, the added benefits of introducing multi-biomarker panels are reviewed, several key biomarkers are evaluated and the analytical benefits provided by multimarkers-based methods are highlighted.

An Innovative Portable Biosensor System for the Rapid Detection of Freshwater Cyanobacterial Algal Bloom Toxins

Harmful algal blooms in freshwater systems are increasingly common and present threats to drinking water systems, recreational waters, and ecosystems. A highly innovative simple to use, portable biosensor system (MBio) for the rapid and simultaneous detection of multiple cyanobacterial toxins in freshwater is demonstrated. The system utilizes a novel planar waveguide optical sensor that delivers quantitative fluorescent competitive immunoassay results in a disposable cartridge. Data are presented for the world's first duplex microcystin (MC)/cylindrospermopsin (CYN) assay cartridge using a combination of fluorophore-conjugated monoclonal antibodies as detector molecules. The on-cartridge detection limits of 20% inhibitory concentration (IC₂₀) was 0.4 μg/L for MC and 0.7 μg/L for CYN. MC assay coverage of eight important MC congeners was demonstrated. Validation using 45 natural lake water samples from Colorado and Lake Erie showed quantitative correlation with commercially available laboratory-based enzyme linked immunosorbent assays. A novel cell lysis module was demonstrated using cyanobacteria cultures. Results show equivalent or better performance than the gold-standard but more tedious 3× freeze-thaw method, with >90% cell lysis for laboratory cultures. The MBio system holds promise as a versatile tool for multiplexed field-based cyanotoxin detection, with future analyte expansion including saxitoxin, anatoxin-a, and marine biotoxins.

Measurement of the IgM and IgG Autoantibody Immune Responses in Human Serum has High Predictive Value for the Presence of Colorectal Cancer

INTRODUCTION

Colorectal cancer is a major public health issue, with incidences continuing to rise owing to the growing and aging world population. Current screening strategies for colorectal cancer diagnosis suffer from various limitations, including invasiveness and poor uptake. Consequently, there is an unmet clinical need for a minimally invasive, sensitive, and specific method for detecting the presence of colorectal cancer and pre-malignant lesions.

PATIENTS AND METHODS

An indirect enzyme-linked immunosorbent assay was used to measure the primary (IgM) and secondary (IgG) adaptive humoral immune responses to a panel of previously identified cancer antigens in the sera of normal and adenoma samples, and sera from patients with colorectal cancer.

RESULTS

An optimal panel of 7 biomarkers capable of identifying patients with colorectal cancer as distinct from both normal and adenoma samples is identified. The cumulative sensitivity and specificity of the assay are 70.8% and 86.5%, respectively. The positive and negative predictive values of the cohort are 77.3% and 82.1%. This assay was not able to accurately discriminate between normal and adenoma samples. Patients whose serum was positive for the presence of anti-ICLN IgM autoantibodies had a significantly poorer 5-year survival than patients whose serum was negative (P = .004).

CONCLUSION

This study describes a novel minimally invasive enzyme-linked immunosorbent assay-based method, capable of identifying patients with colorectal cancer as distinct from both normal and adenoma samples. Patients are likely to be far more amenable to a blood-based test such as the one described herein, rather than a fecal-based test, likely leading to increased patient uptake.

Enhancement and Analysis of Human Antiaflatoxin B1 (AFB1) scFv Antibody-Ligand Interaction Using Chain Shuffling

A human antiaflatoxin B1 (AFB1) scFv antibody (yAFB1-c3), selected from a naı̈ve human phage-displayed scFv library, was used as a template for improving and analysis of antibody-ligand interactions using the chain-shuffling technique. The variable-heavy and variable-light (VH/VL)-shuffled library was constructed from the VH of 25 preselected clones recombined with the VL of yAFB1-c3 and vice versa. Affinity selection from these libraries demonstrated that the VH domain played an important role in the binding of scFv to free AFB1. Therefore, in the next step, VH-shuffled scFv library was constructed from variable-heavy (VH) chain repertoires, amplified from the naı̈ve library, recombined with the variable-light (VL) chain of the clone yAFB1-c3. This library was then used to select a specific scFv antibody against soluble AFB1 by a standard biopanning method. Three clones that showed improved binding properties were isolated. Amino acid sequence analysis indicated that the improved clones have amino acid mutations in framework 1 (FR1) and the complementarity determining region (CDR1) of the VH chain. One clone, designated sAFH-3e3, showed 7.5-fold improvement in sensitivity over the original scFv clone and was selected for molecular binding studies with AFB1. Homology modeling and molecular docking were used to compare the binding of this and the original clones. The results confirmed that VH is more important than VL for AFB1 binding.

Developments in Point-of-Care Diagnostic Technology for Cancer Detection

Cancer is the cause of death for one in seven individuals worldwide. It is widely acknowledged that screening and early diagnosis are of vital importance for improving the likelihood of recovery. However, given the costly, time-consuming, and invasive nature of the many methods currently in use, patients often do not take advantage of the services available to them. Consequently, many researchers are exploring the possibility of developing fast, reliable, and non-invasive diagnostic tools that can be used directly or by local physicians at the point-of-care. Herein, we look at the use of established biomarkers in cancer therapy and investigate emerging biomarkers exhibiting future potential. The incorporation of these biomarkers into point-of-care devices could potentially reduce the strain currently experienced by screening programs in hospitals and healthcare systems. Results derived from point-of-care tests should be accurate, sensitive, and generated rapidly to assist in the selection of the best course of treatment for optimal patient care. Essentially, point-of-care diagnostics should enhance the well-being of patients and lead to a reduction in cancer-related deaths.

Stromal TRIM28-associated signaling pathway modulation within the colorectal cancer microenvironment

BACKGROUND

Stromal gene expression patterns predict patient outcomes in colorectal cancer. TRIM28 is a transcriptional co-repressor that regulates an abundance of genes through the KRAB domain family of transcription factors. We have previously shown that stromal expression of TRIM28 is a marker of disease relapse and poor survival in colorectal cancer. Here, we perform differential epithelium-stroma proteomic network analyses to characterize signaling pathways associated with TRIM28 within the tumor microenvironment.

METHODS

Reverse phase protein arrays were generated from laser capture micro-dissected carcinoma and stromal cells from fresh frozen colorectal cancer tissues. Phosphorylation and total protein levels were measured for 30 cancer-related signaling pathway endpoints. Strength and direction of associations between signaling endpoints were identified using Spearman's rank-order correlation analysis and compared to TRIM28 levels. Expression status of TRIM28 in tumor epithelium and stromal fibroblasts was assessed using IHC in formalin fixed tissue and the epithelium to stroma protein expression ratio method.

RESULTS

We found distinct proteomic networks in the epithelial and stromal compartments which were linked to expression levels of TRIM28. Low levels of TRIM28 in tumor stroma (high epithelium: stroma ratio) were found in 10 out of 19 cases. Upon proteomic network analyses, these stromal high ratio cases revealed moderate signaling pathway similarity exemplified by 76 significant Spearman correlations (ρ ≥ 0.75, p ≤ 0.01). Furthermore, low levels of stromal TRIM28 correlated with elevated MDM2 levels in tumor epithelium (p = 0.01) and COX-2 levels in tumor stroma (p = 0.002). Low TRIM28 epithelium to stroma ratios were associated with elevated levels of caspases 3 and 7 in stroma (p = 0.041 and p = 0.036) and an increased signaling pathway similarity in stromal cells with 81 significant Spearman correlations (ρ ≥ 0.75, p ≤ 0.01).

CONCLUSIONS

By dissecting TRIM28-associated pathways in stromal fibroblasts and epithelial tumor cells, we performed comprehensive proteomic analyses of molecular networks within the tumor microenvironment. We found modulation of several signaling pathways associated with TRIM28, which may be attributed to the pleiotropic properties of TRIM28 through its translational suppression of the family of KRAB domain transcription factors in tumor stromal compartments.

Measuring Antibody-Antigen Binding Kinetics Using Surface Plasmon Resonance

Surface plasmon resonance (SPR) is now widely embraced as a technology for monitoring a diverse range of protein-protein interactions and is considered almost de rigueur for characterizing antibody-antigen interactions. The technique obviates the need to label either of the interacting species, and the binding event is visualized in real time. Thus, it is ideally suited for screening crude, unpurified antibody samples that dominate early candidate panels following antibody selection campaigns. SPR returns not only concentration and affinity data but when used correctly can resolve the discrete component kinetic parameters (association and dissociation rate constants) of the affinity interaction. Herein, we outline some SPR-based generic antibody screening configurations and methodologies in the context of expediting data-rich ranking of candidate antibody panels and ensuring that antibodies with the optimal kinetic binding characteristics are reliably identified.

Direct immunoassays and their performance – theoretical modelling of the effects of antibody orientation and associated kinetics

Mathematical and computational modelling are used to quantify immunoassay signals for various immobilized antibody orientations, antigen sizes and kinetic parameters, in order to determine optimal surface coverage.

Full-length antibodies versus single-chain antibody fragments for a selective impedimetric lectin-based glycoprofiling of prostate specific antigen

The main aim of the research was to design a functional impedimetric biosensor able to glycoprofile prostate specific antigen (PSA), a biomarker for prostate cancer (PCa), with high specificity using lectins as glycan recognising proteins. Traditionally, full-length antibody is immobilised on the biosensor interface for specific capture of PSA with subsequent glycoprofiling of PSA by addition of lectins. Since full-length antibodies contain glycans in the Fc domain, particular attention has to be paid to suppress direct binding of lectins to immobilised full-length antibodies, which would compromise accurate glycoprofiling. This issue is addressed here using a recombinant single-chain antibody fragments (scAb), which do not contain any carbohydrate moiety. Surface plasmon resonance was applied to prove negligible interaction of lectins with immobilised scAb fragments, while substantial binding of lectins to full length antibodies was observed. Eight different biosensor designs were tested for their ability to detect PSA. The biosensor device based on scAb fragments covalently immobilised on the gold electrode surface, patterned by a mixed SAM using standard amine coupling chemistry, proved to be the most sensitive. The scAb fragment-based biosensor exhibited sensitivity of 15.9 ± 0.8% decade^-1 (R² = 0.991 with an average RSD of 4.9%), while the full antibody-based biosensor offered sensitivity towards PSA of 4.2 ± 0.1% decade^-1 (R² = 0.999 with an average RSD of 4.8%). Moreover, the selectivity of the scAb-based biosensor was tested using a kallikrein 2 protein, a protein structurally similar to PSA, and the results indicated high selectivity for PSA detection.

Strategies for overcoming challenges for decentralised diagnostics in resource-limited and catastrophe settings

INTRODUCTION

Globally, both communicable and non-communicable diseases pose a serious threat to populations in developed as well as developing countries. Access to reliable diagnostic testing along with qualified health practitioners is severely limited in low resource and very remote areas and following natural catastrophes. Areas covered: This paper provides an overview of the challenges involved and suggests strategies to address them. The emergence of more robust, user-friendly, cost-effective and 'sample-to-result' point-of-care (POC) tools, along with the proliferation of mobile technologies, may provide a practical approach in addressing some of the challenges. Expert commentary: The successful implementation of POC testing requires the availability of versatile diagnostic technologies, improved platforms and back-up infrastructure, successful leveraging of human resources through training and, finally, engagement/coordination of associated stakeholders, including public health agencies, diagnostics companies, healthcare practitioners and local rural authorities.

Purification of Antibodies Using Affinity Chromatography

Affinity chromatography permits the isolation of a target analyte from a complex mixture and can be utilized to purify proteins, carbohydrates, drugs, haptens, or any analyte of interest once an affinity pair is available. It involves the exploitation of specific interactions between a binding affinity pair, such as those between an antibody and its associated antigen, or between any ligand and its associated binding receptor/protein. With the discovery of protein A in 1970, and, subsequently protein G and L, immuno-affinity chromatography has grown in popularity and is now the standard methodology for the purification of antibodies which may be implemented for a selection of different applications such as immunodiagnostics. This chapter is designed to inform the researcher about the basic techniques involved in the affinity chromatography-based purification of monoclonal, polyclonal, and recombinant antibodies. Examples are provided for the use of protein A and G. In addition, tables are provided that allow the reader to select the most appropriate protein for use in the isolation of their antibody.

Immunoaffinity Chromatography: Concepts and Applications

Antibody-based separation methods, such as immunoaffinity chromatography (IAC), are powerful purification and isolation techniques. Antibodies isolated using these techniques have proven highly efficient in applications ranging from clinical diagnostics to environmental monitoring. Immunoaffinity chromatography is an efficient antibody separation method which exploits the binding efficiency of a ligand to an antibody. Essential to the successful design of any IAC platform is the optimization of critical experimental parameters such as (a) the biological affinity pair, (b) the matrix support, (c) the immobilization coupling chemistry, and (d) the effective elution conditions. These elements and the practicalities of their use are discussed in detail in this review. At the core of all IAC platforms is the high affinity interactions between antibodies and their related ligands; hence, this review entails a brief introduction to the generation of antibodies for use in immunoaffinity chromatography and also provides specific examples of their potential applications.

Measuring Protein-Protein Interactions Using Biacore

The use of optical biosensors for studying macromolecular interactions is gaining increasing popularity. In one study, 1514 papers that involved the application of biosensor data were identified for the year 2009 alone (Rich and Myszka, J Mol Recognit 24:892-914, 2011), the sheer volume and variety of which present a daunting task for the burgeoning biosensor user to accumulate and decipher. This chapter is designed to provide the reader with the tools necessary to prepare, design, and efficiently execute a kinetic experiment on Biacore. It is written to guide the Biacore user through basic theory, system maintenance, and assay setup while also offering some practical tips that we find useful for Biacore-based studies. Many kinetic-based screening assays require rigorous sample preparation and purification prior to analysis. To highlight these procedures, this protocol describes the kinetic characterization of single chain Fv (scFv) antibody fragments from crude bacterial lysates using an antibody affinity capture approach. Even though we specifically describe the capture of HA-tagged scFv antibody fragments to an anti-HA tag monoclonal antibody-immobilized surface prior to kinetic analysis, the same methodologies are universally applicable and can be used for practically any affinity pair and most Biacore systems.

Recombinant antibody fragment production

Recombinant antibodies are now very important in both therapeutics and diagnostics and offer significant advantages over conventional antibodies. The generation of a single-chain variable antibody fragment (scFv) (a common and important recombinant antibody format) is used to demonstrate the construction of a recombinant antibody library. An immunotube-based two-day panning approach, using Escherichia coli as an expression system, is utilised for antibody screening. The methods used for antibody selection and purification using immobilised metal affinity chromatography (IMAC) are described.

Eosinophil peroxidase activates cells by HER2 receptor engagement and β1-integrin clustering with downstream MAPK cell signaling

Eosinophils account for 1–3% of peripheral blood leukocytes and accumulate at sites of allergic inflammation, where they play a pathogenic role. Studies have shown that treatment with mepolizumab (an anti-IL-5 monoclonal antibody) is beneficial to patients with severe eosinophilic asthma, however, the mechanism of precisely how eosinophils mediate these pathogenic effects is uncertain. Eosinophils contain several cationic granule proteins, including Eosinophil Peroxidase (EPO). The main significance of this work is the discovery of EPO as a novel ligand for the HER2 receptor. Following HER2 activation, EPO induces activation of FAK and subsequent activation of β1-integrin, via inside-out signaling. This complex results in downstream activation of ERK1/2 and a sustained up regulation of both MUC4 and the HER2 receptor. These data identify a receptor for one of the eosinophil granule proteins and demonstrate a potential explanation of the proliferative effects of eosinophils.

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Eosinophil peroxidase (EPO) is confirmed as a ligand for the HER2 receptor.

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EPO activation of HER2 leads to activation of FAK, ERK and β1 integrin.

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EPO induces a sustained upregulation of MUC4 and HER2.

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Possible mechanism for the proliferative effects of eosinophils is uncovered.

Comparison of Enzyme-Linked Immunosorbent Assay, Surface Plasmon Resonance and Biolayer Interferometry for Screening of Deoxynivalenol in Wheat and Wheat Dust

A sample preparation method was developed for the screening of deoxynivalenol (DON) in wheat and wheat dust. Extraction was carried out with water and was successful due to the polar character of DON. For detection, an enzyme-linked immunosorbent assay (ELISA) was compared to the sensor-based techniques of surface plasmon resonance (SPR) and biolayer interferometry (BLI) in terms of sensitivity, affinity and matrix effect. The matrix effects from wheat and wheat dust using SPR were too high to further use this screenings method. The preferred ELISA and BLI methods were validated according to the criteria established in Commission Regulation 519/2014/EC and Commission Decision 2002/657/EC. A small survey was executed on 16 wheat lots and their corresponding dust samples using the validated ELISA method. A linear correlation (r = 0.889) was found for the DON concentration in dust versus the DON concentration in wheat (LOD wheat: 233 μg/kg, LOD wheat dust: 458 μg/kg).

Galectin-1 and Galectin-3 Constitute Novel-Binding Partners for Factor VIII

OBJECTIVE

Recent studies have demonstrated that galectin-1 (Gal-1) and galectin-3 (Gal-3) can bind von Willebrand factor and directly modulate von Willebrand factor-dependent early thrombus formation in vivo. Because the glycans expressed on human factor VIII (FVIII) are similar to those of von Willebrand factor, we investigated whether galectins might also bind and modulate the activity of FVIII.

APPROACH AND RESULTS

Immunosorbant assays and surface plasmon resonance analysis confirmed that Gal-1 and Gal-3 bound purified FVIII with high affinity. Exoglycosidase removal of FVIII N-linked glycans significantly reduced binding to both Gal-1 and Gal-3. Moreover, combined removal of both the N- and O-glycans of FVIII further attenuated Gal-3 binding. Notably, specific digestion of FVIII high-mannose glycans at N239 and N2118 significantly impaired FVIII affinity for Gal-1. Importantly Gal-1, but not Gal-3, bound to free FVIII in the plasma milieu, and significantly inhibited FVIII functional activity. Interestingly, commercial recombinant FVIII (rFVIII) concentrates are manufactured in different cell lines and differ in their glycosylation profiles. Although the biological mechanism has not been defined, recent studies in previously untreated patients with severe hemophilia A reported significant differences in inhibitor development associated with different rFVIII products. Interestingly, Gal-1 and Gal-3 both displayed enhanced affinity for BHK-rFVIII compared with CHO-rFVIII. Furthermore, binding of Gal-1 and Gal-3 to BDD-FVIII was markedly reduced compared with full-length rFVIII.

CONCLUSIONS

We have identified Gal-1 and Gal-3 as novel-binding partners for human FVIII and demonstrated that Gal-1 binding can influence the procoagulant activity of FVIII.

Referencing cross-reactivity of detection antibodies for protein array experiments

Protein arrays are frequently used to profile antibody repertoires in humans and animals. High-throughput protein array characterisation of complex antibody repertoires necessitates the use of extensively validated secondary detection antibodies. This article details the validation of an affinity-isolated anti-chicken IgY antibody produced in rabbit and a goat anti-rabbit IgG antibody conjugated with alkaline phosphatase using protein arrays consisting of 7,390 distinct human proteins. Probing protein arrays with secondary antibodies in absence of chicken serum revealed non-specific binding to 61 distinct human proteins. Despite the identified non-specific binding, the tested antibodies are well suited for use in protein array experiments as the cross-reactive binding partners can be readily excluded from further analysis. The evident cross-reactivity of the tested secondary detection antibodies points towards the necessity of platform-specific antibody characterisation studies for all secondary immunoreagents. Furthermore, secondary antibody characterisation using protein arrays enables the generation of reference lists of cross-reactive proteins, which can be then marked as potential false positives in follow-up experiments. Providing such cross-reactivity reference lists accessible to the wider research community may help to interpret data generated with the same antibodies in applications not only related to protein arrays such as immunoprecipitation, Western blots or other immunoassays.

Differential internalin A levels in biofilms of Listeria monocytogenes grown on different surfaces and nutrient conditions

Listeria monoctyogenes is a foodborne pathogen containing the surface protein, internalin A (InlA). The expression of this protein permits the invasion of L. monocytogenes into intestinal epithelial cells expressing the receptor E-cadherin, thus crossing the intestinal barrier and resulting in listerosis. The main aim of this work was to investigate InlA levels in different L. monocytogenes strains in both planktonic and sessile states using an anti-InlA antibody. Biofilms were grown in high and low nutrient environments on glass, stainless steel and polytetrafluoroethylene (PTFE). This study demonstrated that InlA levels varied greatly between strains and serotypes of L. monocytogenes. However, the serotypes 1/2a, 1/2b and 4b, associated with the largest number of outbreaks of listerosis consistently showed the highest InlA levels, regardless of nutrient content or planktonic or sessile state. Differences in InlA levels were also observed in biofilms grown on different surfaces such as glass, stainless steel and PTFE, with a significant reduction in InlA levels observed in biofilms on PTFE. Interestingly, although a large number of the total cells observed in biofilms formed in tap-water were non-cultivable, the virulence factor, InlA, was expressed at levels between 78 and 85%, thus indicating that these cells may still be virulent. A greater understanding of the factors that affect the levels of InlA on the surface of L. monocytogenes, is essential in the appreciation of the role of InlA in the persistence of biofilms containing L. monocytogenes and their potential to cause food borne disease.

Detection of prostate specific antigen based on electrocatalytic platinum nanoparticles conjugated to a recombinant scFv antibody

Highly sensitive and label free detection of prostate specific antigen (PSA) still remains a challenge in prostate cancer diagnosis. In this paper, we propose a sensitive electrochemical immunosensor based on electrocatalytic platinum nanoparticles conjugated to a recombinant scFv antibody. Gold disc electrodes functionalised with a l-Cysteine (Cys) self-assembled monolayer (SAM) were used to covalently bind PSA specific monoclonal antibody (anti-PSA) using N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide (EDC/NHS) chemistry. Immunosensing was completed using sandwich-type immunoreaction of the PSA-antigen (1-30 ng/mL) between anti-PSA immobilized on the l-Cys modified electrode using label free electrochemical impedance (EIS) technique. Furthermore, highly specific in-house generated scFv fragments as receptor proteins were utilised for one step site-directed immobilisation on the surface of platinum nanoparticles (PtNPs). To improve the sensitivity of the immunoassay, these scFV labelled electrocatalytic PtNPs were then used for covalent hybridisation to the PSA modified electrode and then applied in a hybridisation assay to determine the concentration of the PSA by measuring the faradaic current associated with reduction of peroxide in solution. Semi-log plots of the PSA concentration vs. faradaic current are linear from 1 to 30 ng/mL and pM concentrations can be detected without the need for molecular, e.g., PCR or NASBA, amplification.

Production of functional human vitamin A transporter/RBP receptor (STRA6) for structure determination

STRA6 is a plasma membrane protein that mediates the transport of vitamin A, or retinol, from plasma retinol binding protein (RBP) into the cell. Mutations in human STRA6 are associated with Matthew-Wood syndrome, which is characterized by severe developmental defects. Despite the obvious importance of this protein to human health, little is known about its structure and mechanism of action. To overcome the difficulties frequently encountered with the production of membrane proteins for structural determination, STRA6 has been expressed in Pichia pastoris as a fusion to green fluorescent protein (GFP), a strategy which has been a critical first step in solving the crystal structures of several membrane proteins. STRA6-GFP was correctly targeted to the cell surface where it bound RBP. Here we report the large-scale expression, purification and characterisation of STRA6-GFP. One litre of culture, corresponding to 175 g cells, yielded about 1.5 mg of pure protein. The interaction between purified STRA6 and its ligand RBP was studied by surface plasmon resonance-based binding analysis. The interaction between STRA6 and RBP was not retinol-dependent and the binding data were consistent with a transient interaction of 1 mole RBP/mole STRA6.

Controlling colloidal stability of silica nanoparticles during bioconjugation reactions with proteins and improving their longer-term stability, handling and storage

Robust protocols for antibody-nanoparticle (Ab-NP) conjugation, and improved method for long-term stability and storage of Ab-NPs using cryoprotectants.

Abstract B55: Molecular characterization of epithelial and stromal crosstalk associated with TRIM28 expression levels in colorectal cancer

Background: TRIM28 is a universal transcriptional co-repressor with pleotropic effects in both normal and tumor cells. We have previously shown that varying TRIM28 levels in epithelial cells and stromal fibroblasts have a prognostic value in colorectal cancer patients. The pathophysiological role of TRIM28 in carcinogenesis may therefore be associated with TRIM28 expression levels and cell type of expression within the tumor microenvironment. In this study we aim to dissect the molecular pathways associated with TRIM28 expression ratios within the tumor microenvironment by isolating individual populations of neoplastic epithelial and stromal cells and investigating their protein signaling networks. Methods: TRIM28 expression was analyzed by immunohistochemistry on FFPE tissue from 19 colorectal cancer patients. TRIM28 staining was evaluated in both epithelial and stromal compartments. IHC scoring of at least 2 units of difference in staining intensity between stromal fibroblasts and epithelial cells was defined as a high TRIM28 expression ratio and a low TRIM28 expression ratio was defined as 1 or 0 units of difference in staining intensity. Reverse-phase protein microarrays (RPMA) were constructed from laser capture micro-dissection (LCM) enriched tumor epithelium and stroma isolated from fresh-frozen tissue of the same patient cohort. The protein signaling networks were measured for 32 downstream signaling endpoints. Spearman rank analysis was used to assess the correlations between individual protein pairs. Correlation coefficient ρ ≥ 0.75 with P ≤ 0.01 was considered significant. Results: Immunohistochemical analysis of the FFPE tissue sections identified 10 TRIM28 high ratio cases and 9 TRIM28 low ratio cases. Proteomic networks were assessed in TRIM28 high and low ratio cases in fresh-frozen tissue using RPMA. Spearman ρ rank correlation analyses for the 32 signaling proteins revealed that 184 highly correlated protein pairs exclusive to the TRIM28 high ratio group, whereas 157 protein pairs were found exclusively in the TRIM28 low ratio group. In addition 191 protein pairs were shared across both TRIM28 high and low ratio groups. The caspases 3 and 7, as well as the cell surface receptor RAGE, were prominent in the high TRIM28 ratio group proteomic network, whereas the Metalloprotease MMP9 and the GTPase Ras-GRF1 were exclusive to the low TRIM28 ratio group. Furthermore we found Survivin and JNK to be prominent in the stromal compartment of the high TRIM28 cases. Conclusions: We characterized molecular pathways associated with TRIM28 expression ratios within the tumor microenvironment. Proteomic analysis revealed distinct protein signaling networks associated with varying TRIM28 expression levels in epithelial and stromal compartments. The study presents a novel way of deciphering molecular crosstalk between the epithelial and stromal compartments within the microenvironment.

Citation Format: Seán Fitzgerald, Virginia Espina, Katherine M. Sheehan, Robert Cummins, Anthony O'Grady, Dermot Kenny, Richard O'Kennedy, Lance Liotta, Elaine W. Kay, Gregor Kijanka. Molecular characterization of epithelial and stromal crosstalk associated with TRIM28 expression levels in colorectal cancer. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr B55. doi:10.1158/1538-7445.CHTME14-B55

The Structure of Natural and Recombinant Antibodies

Immunoglobulins (Ig) isotypes A, D, E, G, and M are glycoproteins which are mainly composed of a "Y"-shaped Ig monomer (~150 kDa), consisting of two light and two heavy chains. Both light and heavy chains contain variable (N-terminal) and constant regions (C-terminal). Each light chain consists of one variable domain and one constant domain, whereas each heavy chain has one variable domain and three constant domains. However, heavy-chain antibodies consisting of only heavy chains and lacking the light chains are found in camelids and cartilaginous fishes. Unlike other immunoglobulins, the heavy chain of avian antibody IgY (~180 kDa) consists of four constant domains. The single-chain variable fragment (scFv; ~25 kDa) of an antibody contains variable regions of antibody heavy and light chains. The fragment antigen-binding (Fab; ~50 kDa) region has the full antibody light chain but the heavy chain is composed of a variable region and one constant domain.

Electrochemiluminescence platform for the detection of C-reactive proteins: application of recombinant antibody technology to cardiac biomarker detection

The stepwise fabrication of the sensor is highlighted, scFv immobilization, binding of pentameric CRP followed by binding of metal labeled scFv fragments.

High CerS5 expression levels associate with reduced patient survival and transition from apoptotic to autophagy signalling pathways in colorectal cancer

Ceramide synthase 5 is involved in the de novo synthesis of ceramide, a sphingolipid involved in cell death and proliferation. In this study, we investigated the role of ceramide synthase 5 in colorectal cancer by examining ceramide synthase 5 expression, clinico-pathological parameters and association with survival/death signalling pathways in cancer. Immunohistochemical analysis of CerS5 was performed on 102 colorectal cancer samples using tissue microarrays constructed from formalin-fixed and paraffin-embedded tissues. We found strong membranous ceramide synthase 5 staining in 57 of 102 (56%) colorectal cancers. A multivariate Cox regression analysis of ceramide synthase 5 expression adjusted for disease stage, differentiation and lymphovascular invasion revealed reduced 5-year overall survival (p = 0.001) and 5-year recurrence-free survival (p = 0.002), with hazard ratios of 4.712 and 4.322, respectively. The effect of ceramide synthase 5 expression on tumourigenic processes was further characterised by reverse phase protein array analysis. Reverse phase protein arrays were generated from laser capture microdissection-enriched carcinoma cells from 19 fresh-frozen colorectal cancer tissues. Measurements of phosphorylation and total levels of signalling proteins involved in apoptosis, autophagy and other cancer-related pathways revealed two distinct signalling networks; weak membranous ceramide synthase 5 intensity was associated with a proteomic network dominated by signalling proteins linked to apoptosis, whereas strong ceramide synthase 5 intensity was associated with a proteomic sub-network mostly composed of proteins linked to autophagy. In conclusion, high ceramide synthase 5 expression was found in colorectal cancer tissue and was associated with poorer patient outcomes. Our findings suggest that this may be mediated by a transition from apoptotic to autophagy signalling pathways in ceramide synthase 5 High expressing tumours, thus implicating ceramide synthase 5 in the progression of colorectal cancer.

A chemical quenching- and physical blocking-based method to minimize process-mediated aggregation of antibody-crosslinked nanoparticles for imaging application

Critical limitation of nanoparticles (NP) is their aggregation after functionalisation and antibody cross-linking. We analysed the cause of this aggregation with respect to functionalities (carboxyls and amines) on the NP surface. We have devised a low cost novel method to reduce such aggregations during protein cross-linking and validated it by probing the platelet surface with platelet surface-specific anti-CD41 antibody conjugated NPs.

Biological and synthetic binders for immunoassay and sensor-based detection: generation and characterisation of an anti-AFB2 single-chain variable fragment (scFv)

Aflatoxins are highly carcinogenic in nature and occur in a variety of food and feed samples. To ensure food is free from aflatoxins and safe for human consumption, methods to detect these toxins are necessary. Both aflatoxin B1 and aflatoxin B2 (AFB2) co-occur in a variety of foods. The present study focuses on the generation of single-chain variable antibody fragments (scFvs) that are highly specific to AFB2. A panel of murine scFvs was isolated from a recombinant AFB2 library that was subjected to biopanning against AFB2-bovine serum albumin. The scFvs (E9 and H12) were found to be highly specific to AFB2, with no cross reactivity for other aflatoxins. The analytical potential of these two scFvs was tested by competitive inhibition ELISA and half maximal inhibitory concentrations (IC50) of 85 and 138 ng/ml, respectively, were shown. The affinity and sensitivity of scFv-E9 was determined by kinetic analysis and surface plasmon resonance (SPR)-based competitive inhibition assay using an AFB2-immobilised sensor chip. An SPR-based inhibition assay with IC50 of 8 ng/ml and LOD of 0.9 ng/ml was developed and subsequently successfully applied for AFB2 detection in spiked almond extracts.

Determination of 20 coccidiostats in milk, duck muscle and non-avian muscle tissue using UHPLC-MS/MS

In this paper, methods were developed to measure coccidiostats in bovine milk, duck muscle and non-avian species. The methods were validated to the maximum levels and MRLs laid down in European Union legislation. A simple sample preparation procedure was developed for the isolation of coccidiostat residues from bovine, ovine, equine, porcine and duck muscle tissue, based on solvent extraction with acetonitrile and concentration. An alternative method had to be developed for milk samples based on the QuEChERS sample preparation approach because of the high water content in this matrix. Milk samples were adjusted to basic pH with sodium hydroxide and extracted by using a slurry of acetonitrile, MgSO4 and NaCl. Purified sample extracts were subsequently analysed by using UHPLC-MS/MS in a 13.2-min chromatographic run. It was found that the use of rapid polarity switching enabled both negatively and positively charged ions to be analysed from a single injection. By using this approach, solvent usage was reduced significantly and sample throughput improved. The method was validated for the analysis of 20 coccidiostats (arprinocid, clopidol, decoquinate, diclazuril, diaveridine, ethopabate, halofuginone, laidlomycin, lasalocid, maduramicin, monensin, narasin, nequinate, nicarbazin, robenidine, salinomycin, semduramicin, toltrazuril, toltrazuril sulphoxide and toltrazuril sulphone) in muscle and milk. The method is quantitative for toltrazurils, but it cannot be used for confirmation because only the precursor ion is monitored. Accuracy values for muscle ranged from 80% to 125%, while CCα ranged from 2.2 µg kg(-1) for clopidol to 122 µg kg(-1) for toltrazuril sulphoxide. Bovine milk accuracy ranged from 84% to 120% for all analytes except maduramicin, semduramicin and salinomycin, for which the values were higher. CCα values achieved ranged from 1.1 µg kg(-1) for arprinocid, nequinate and lasalocid to 27 µg kg(-1) for toltrazuril.

Relationship between epithelial and stromal TRIM28 expression predicts survival in colorectal cancer patients

BACKGROUND AND AIM

TRIM28 is a multi-domain nuclear protein with pleotropic effects in both normal and tumor cells. In this study, TRIM28 expression in epithelial and stromal tumor microenvironment and its prognostic role in colorectal cancer were investigated.

METHODS

Immunohistological staining of TRIM28 was evaluated in tissue microarrays constructed from 137 colorectal cancer patients. The correlations of TRIM28 expression with clinicopathological features and p53 expression were studied. Kaplan-Meier analysis and Cox proportional hazard modeling were used to assess overall survival (OS) and recurrence-free survival (RFS).

RESULTS

Strong epithelial TRIM28 expression was found in 42% of colorectal cancer tissues. TRIM28 expression correlated significantly with p53 expression in matched cases (P=0.0168, Spearman rank test). A high epithelial to stromal TRIM28 expression ratio was associated with shorter OS (P=0.033; log-rank test) and RFS (P=0.043; log-rank test). Multivariate analysis showed that the epithelial to stromal TRIM28 expression ratio was an independent predictor of OS (hazard ratio=2.136; 95% confidence interval 1.015-4.498, P=0.046) and RFS (hazard ratio=2.100; confidence interval 1.052-4.191, P=0.035).

CONCLUSION

A high TRIM28 expression ratio between stromal and epithelial compartments in colorectal cancer tissue is an independent predictor of poor prognosis. The pathophysiological role of TRIM28 in carcinogenesis may be dependent on expression levels and cell type within the tumor microenvironment.

An evaluation of the capability of a biolayer interferometry biosensor to detect low-molecular-weight food contaminants

The safety of our food is an essential requirement of society. One well-recognised threat is that of chemical contamination of our food, where low-molecular-weight compounds such as biotoxins, drug residues and pesticides are present. Low-cost, rapid screening procedures are sought to discriminate the suspect samples from the population, thus selecting only these to be forwarded for confirmatory analysis. Many biosensor assays have been developed as screening tools in food contaminant analysis, but these tend to be electrochemical, fluorescence or surface plasmon resonance based. An alternative approach is the use of biolayer interferometry, which has become established in drug discovery and life science studies but is only now emerging as a potential tool in the analysis of food contaminants. A biolayer interferometry biosensor was assessed using domoic acid as a model compound. Instrument repeatability was tested by simultaneously producing six calibration curves showing replicate repeatability (n = 2) ranging from 0.1 to 6.5 % CV with individual concentration measurements (n = 12) ranging from 4.3 to 9.3 % CV, giving a calibration curve midpoint of 7.5 ng/ml (2.3 % CV (n = 6)). Reproducibility was assessed by producing three calibration curves on different days, giving a midpoint of 7.5 ng/ml (3.4 %CV (n = 3)). It was further shown, using assay development techniques, that the calibration curve midpoint could be adjusted from 10.4 to 1.9 ng/ml by varying assay parameters before the simultaneous construction of three calibration curves in matrix and buffer. Sensitivity of the assay compared favourably with previously published biosensor data for domoic acid.

Centrifugo-pneumatic valving utilizing dissolvable films

In this article we introduce a novel technology that utilizes specialized water dissolvable thin films for valving in centrifugal microfluidic systems. In previous work (William Meathrel and Cathy Moritz, IVD Technologies, 2007), dissolvable films (DFs) have been assembled in laminar flow devices to form efficient sacrificial valves where DFs simply open by direct contact with liquid. Here, we build on the original DF valving scheme to leverage sophisticated, merely rotationally actuated vapour barriers and flow control for enabling comprehensive assay integration with low-complexity instrumentation on "lab-on-a-disc" platforms. The advanced sacrificial valving function is achieved by creating an inverted gas-liquid stack upstream of the DF during priming of the system. At low rotational speeds, a pocket of trapped air prevents a surface-tension stabilized liquid plug from wetting the DF membrane. However, high-speed rotation disrupts the metastable gas/liquid interface to wet the DF and thus opens the valve. By judicious choice of the radial position and geometry of the valve, the burst frequency can be tuned over a wide range of rotational speeds nearly 10 times greater than those attained by common capillary burst valves based on hydrophobic constrictions. The broad range of reproducible burst frequencies of the DF valves bears the potential for full integration and automation of comprehensive, multi-step biochemical assay protocols. In this report we demonstrate DF valving, discuss the biocompatibility of using the films, and show a potential sequential valving system including the on-demand release of on-board stored liquid reagents, fast centrifugal sedimentation and vigorous mixing; thus providing a viable basis for use in lab-on-a-disc platforms for point-of-care diagnostics and other life science applications.

Synthesis and characterization of model silica-gold core-shell nanohybrid systems to demonstrate plasmonic enhancement of fluorescence

In this work, gold-silica plasmonic nanohybrids have been synthesized as model systems which enable tuning of dye fluorescence enhancement/quenching interactions. For each system, a dye-doped silica core is surrounded by a 15 nm spacer region, which in turn is surrounded by gold nanoparticles (GNPs). The GNPs are either covalently conjugated via mercapto silanization to the spacer or encapsulated in a separate external silica shell. The intermediate spacer region can be either dye doped or left undoped to enable quenching and plasmonic enhancement effects respectively. The study indicates that there is a larger enhancement effect when GNPs are encapsulated in the outer shell compared to the system of external conjugation. This is due to the environmental shielding provided by shell encapsulation compared to the exposure of the GNPs to the solvent environment for the externally conjugated system. The fluorescence signal enhancement of the nanohybrid systems was evaluated using a standard HRP-anti-HRP fluorescence based assay platform.