Rapid and sensitive immunomagnetic-electrochemiluminescent detection of p53 antibodies in human serum

One-Stop Serum Assay Identifies COVID-19 Disease Severity and Vaccination Responses

SARS-CoV-2 has caused over 100,000,000 cases and almost 2,500,000 deaths globally. Comprehensive assessment of the multifaceted antiviral Ab response is critical for diagnosis, differentiation of severity, and characterization of long-term immunity, especially as COVID-19 vaccines become available. Severe disease is associated with early, massive plasmablast responses. We developed a multiplex immunoassay from serum/plasma of acutely infected and convalescent COVID-19 patients and prepandemic and postpandemic healthy adults. We measured IgA, IgG, and/or IgM against SARS-CoV-2 nucleocapsid (N), spike domain 1 (S1), S1-receptor binding domain (RBD) and S1-N-terminal domain. For diagnosis, the combined [IgA + IgG + IgM] or IgG levels measured for N, S1, and S1-RBD yielded area under the curve values ≥0.90. Virus-specific Ig levels were higher in patients with severe/critical compared with mild/moderate infections. A strong prozone effect was observed in sera from severe/critical patients-a possible source of underestimated Ab concentrations in previous studies. Mild/moderate patients displayed a slower rise and lower peak in anti-N and anti-S1 IgG levels compared with severe/critical patients, but anti-RBD IgG and neutralization responses reached similar levels at 2-4 mo after symptom onset. Measurement of the Ab responses in sera from 18 COVID-19-vaccinated patients revealed specific responses for the S1-RBD Ag and none against the N protein. This highly sensitive, SARS-CoV-2-specific, multiplex immunoassay measures the magnitude, complexity, and kinetics of the Ab response and can distinguish serum Ab responses from natural SARS-CoV-2 infections (mild or severe) and mRNA COVID-19 vaccines.

Construction of a ternary nano-architecture based graphene oxide sheets, toward electrocatalytic determination of tumor-associated anti-p53 autoantibodies in human serum

Almost 13% of all death in the world is related to cancer. One of the major reasons for failing cancer treatment is the late diagnosis of the tumors. Thus, diagnosis at the early stages could be vital for the treatment. Serum autoantibodies, as tumor markers, are becoming interesting targets due to their medical and biological relevance. Among them, anti-p53 autoantibody in human sera is found to be involved in a variety of cancers. Regarding this issue, a novel and sensitive electrochemical biosensor for detection of anti-p53 autoantibody has been developed. For this purpose, a nanocomposite including thionine (as an electron transfer mediator)/chitosan/nickel hydroxide nanoparticles/electrochemically reduced graphene oxide (Th-CS-Ni(OH)₂NPs-ERGO) as a support platform was fabricated on the surface of glassy carbon electrode via a layer-by-layer manner and characterized through common electrochemical and imaging techniques. Then, p53-antigen was immobilized on the nanocomposite and used in an indirect immunoassay with horseradish peroxidase (HRP)-conjugated secondary antibody and H₂O₂ as the substrate, following the typical Michaelis-Menten kinetics. Under optimized condition, two techniques, including differential Pulse Voltammetry (DPV) and Electrochemical Impedance Spectroscopy (EIS) as a label free technique, applied for the biomarker detection. The linear ranges and LODs were obtained 0.1-500 pg mL^-1 and 0.001 pg mL^-1 using DPV and 5-150 pg mL^-1 and 0.007 pg mL^-1 using EIS, respectively. Furthermore, the proposed biosensor displayed satisfying stability, selectivity, and reproducibility. According to the results, the presented protocol is promising to develop other electrochemical biosensors.

Elevated SARS-CoV-2 Antibodies Distinguish Severe Disease in Early COVID-19 Infection

Background

SARS-CoV-2 has caused over 36,000,000 cases and 1,000,000 deaths globally. Comprehensive assessment of the multifaceted anti-viral antibody response is critical for diagnosis, differentiation of severe disease, and characterization of long-term immunity. Initial observations suggest that severe disease is associated with higher antibody levels and greater B cell/plasmablast responses. A multi-antigen immunoassay to define the complex serological landscape and clinical associations is essential.

Methods

We developed a multiplex immunoassay and evaluated serum/plasma from adults with RT-PCR-confirmed SARS-CoV-2 infections during acute illness (N=52) and convalescence (N=69); and pre-pandemic (N=106) and post-pandemic (N=137) healthy adults. We measured IgA, IgG, and/or IgM against SARS-CoV-2 Nucleocapsid (N), Spike domain 1 (S1), receptor binding domain (S1-RBD) and S1-N-terminal domain (S1-NTD).

Results

To diagnose infection, the combined [IgA+IgG+IgM] or IgG for N, S1, and S1-RBD yielded AUC values -0.90 by ROC curves. From days 6-30 post-symptom onset, the levels of antigen-specific IgG, IgA or [IgA+IgG+IgM] were higher in patients with severe/critical compared to mild/moderate infections. Consistent with excessive concentrations of antibodies, a strong prozone effect was observed in sera from severe/critical patients. Notably, mild/moderate patients displayed a slower rise and lower peak in anti-N and anti-S1 IgG levels compared to severe/critical patients, but anti-RBD IgG and neutralization responses reached similar levels at 2-4 months.

Conclusion

This SARS-CoV-2 multiplex immunoassay measures the magnitude, complexity and kinetics of the antibody response against multiple viral antigens. The IgG and combined-isotype SARS-CoV-2 multiplex assay is highly diagnostic of acute and convalescent disease and may prognosticate severity early in illness.

One Sentence Summary

In contrast to patients with moderate infections, those with severe COVID-19 develop prominent, early antibody responses to S1 and N proteins.

Sliding mode controller-observer pair for p53 pathway

A significant loss of p53 protein, an anti-tumour agent, is observed in early cancerous cells. Induction of small molecules based drug is by far the most prominent technique to revive and maintain wild-type p53 to the desired level. In this study, a sliding mode control (SMC) based robust non-linear technique is presented for the drug design of a control-oriented p53 model. The control input generated by conventional SMC is discontinuous; however, depending on the physical nature of the system, drug infusion needs to be continuous. Therefore, to obtain a smooth control signal, a dynamic SMC (DSMC) is designed. Moreover, the boundedness of the zero-dynamics is also proved. To make the model-based control design possible, the unknown states of the system are estimated using an equivalent control based, reduced-order sliding mode observer. The robustness of the proposed technique is assessed by introducing input disturbance and parametric uncertainty in the system. The effectiveness of the proposed control scheme is witnessed by performing in-silico trials, revealing that the sustained level of p53 can be achieved by controlled drug administration. Moreover, a comparative quantitative analysis shows that both controllers yield similar performance. However, DSMC consumes less control energy.

System-based strategies for p53 recovery

The authors have proposed a systems theory-based novel drug design approach for the p53 pathway. The pathway is taken as a dynamic system represented by ordinary differential equations-based mathematical model. Using control engineering practices, the system analysis and subsequent controller design is performed for the re-activation of wild-type p53. p53 revival is discussed for both modes of operation, i.e. the sustained and oscillatory. To define the problem in control system paradigm, modification in the existing mathematical model is performed to incorporate the effect of Nutlin. Attractor point analysis is carried out to select the suitable domain of attraction. A two-loop negative feedback control strategy is devised to drag the system trajectories to the attractor point and to regulate cellular concentration of Nutlin, respectively. An integrated framework is constituted to incorporate the pharmacokinetic effects of Nutlin in the cancerous cells. Bifurcation analysis is also performed on the p53 model to see the conditions for p53 oscillation.

Non-linear feedback control of the p53 protein-mdm2 inhibitor system using the derivative-free non-linear Kalman filter

It is proven that the model of the p53-mdm2 protein synthesis loop is a differentially flat one and using a diffeomorphism (change of state variables) that is proposed by differential flatness theory it is shown that the protein synthesis model can be transformed into the canonical (Brunovsky) form. This enables the design of a feedback control law that maintains the concentration of the p53 protein at the desirable levels. To estimate the non-measurable elements of the state vector describing the p53-mdm2 system dynamics, the derivative-free non-linear Kalman filter is used. Moreover, to compensate for modelling uncertainties and external disturbances that affect the p53-mdm2 system, the derivative-free non-linear Kalman filter is re-designed as a disturbance observer. The derivative-free non-linear Kalman filter consists of the Kalman filter recursion applied on the linearised equivalent of the protein synthesis model together with an inverse transformation based on differential flatness theory that enables to retrieve estimates for the state variables of the initial non-linear model. The proposed non-linear feedback control and perturbations compensation method for the p53-mdm2 system can result in more efficient chemotherapy schemes where the infusion of medication will be better administered.

Adsorption according to the Langmuir-Freundlich model is the detection mechanism of the antigen p53 for early diagnosis of cancer

Biosensors for early detection of cancer biomarkers normally depend on specific interactions between such biomarkers and immobilized biomolecules in the sensing units. Though these interactions are expected to yield specific, irreversible adsorption, the underlying mechanism appears not to have been studied in detail. In this paper, we show that adsorption explained with the Langmuir-Freundlich model is responsible for detection of the antigen p53 associated with various types of cancers. Irreversible adsorption was proven between anti-p53 antibodies immobilized on the biosensors and the antigen p53, with the adequacy of the Langmuir-Freundlich model being confirmed with three independent experimental methods, viz. polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS), nanogravimetry using a quartz crystal microbalance and electrochemical impedance spectroscopy. The method based on this irreversible adsorption was sufficiently sensitive (limit of detection of 1.4 pg mL(-1)) for early diagnosis of Hodgkin lymphoma, pancreatic and colon carcinomas, and bladder, ovarian and lung cancers, and could distinguish between MCF7 cells containing the antigen p53 from Saos-2 cells that do not contain it.

An Electrochemiluminescence Immunosensor Based on Gold-Magnetic Nanoparticles and Phage Displayed Antibodies

Using the multiple advantages of the ultra-highly sensitive electrochemiluminescence (ECL) technique, Staphylococcus protein A (SPA) functionalized gold-magnetic nanoparticles and phage displayed antibodies, and using gold-magnetic nanoparticles coated with SPA and coupled with a polyclonal antibody (pcAb) as magnetic capturing probes, and Ru(bpy)₃²⁺-labeled phage displayed antibody as a specific luminescence probe, this study reports a new way to detect ricin with a highly sensitive and specific ECL immunosensor and amplify specific detection signals. The linear detection range of the sensor was 0.0001~200 µg/L, and the limit of detection (LOD) was 0.0001 µg/L, which is 2500-fold lower than that of the conventional ELISA technique. The gold-magnetic nanoparticles, SPA and Ru(bpy)₃²⁺-labeled phage displayed antibody displayed different amplifying effects in the ECL immunosensor and can decrease LOD 3-fold, 3-fold and 20-fold, respectively, compared with the ECL immunosensors without one of the three effects. The integrated amplifying effect can decrease the LOD 180-fold. The immunosensor integrates the unique advantages of SPA-coated gold-magnetic nanoparticles that improve the activity of the functionalized capturing probe, and the amplifying effect of the Ru(bpy)₃²⁺-labeled phage displayed antibodies, so it increases specificity, interference-resistance and decreases LOD. It is proven to be well suited for the analysis of trace amounts of ricin in various environmental samples with high recovery ratios and reproducibility.

Au nanoparticle decorated graphene nanosheets for electrochemical immunosensing of p53 antibodies for cancer prognosis

Thiolated self-assembled reduced graphene oxide films were decorated with gold nanoparticles for development of a label-free p53-antibody immunosensor.

Nanomaterials and biomaterials in electrochemical arrays for protein detection

Nanomaterials and biomaterials are important components of new electrochemical arrays designed for sensitive detection of proteins in biological fluids. Such multiplexed protein arrays are predicted to have an important future in personalized medical diagnostics, especially for cancer and heart disease. Sandwich immunoassays for proteins benefit greatly in sensitivity from the use of nanostructured sensor surfaces and multilabeled detection strategies involving nano- or microparticles. In these assays, capture agents such as antibodies or aptamers are attached to sensor surfaces in the array. Target proteins with large binding constants for the affinity agents are captured from liquid samples with high efficiency, either on the sensors or on magnetic bioconjugate particles decorated with many copies of labels and antibodies. After target proteins are captured on the sensor surfaces, the labels are detected by electrochemical techniques. This feature article begins with an overview of the recent history of nanoparticles in electrochemical protein sensors, then moves on to specific examples from our own laboratories. We discuss fabrication of nanostructured sensors and arrays with the aim of multiplexed detection as well as reusability. Following this, we describe systems that integrate particle-based protein sensing with microfluidics for multiplexed protein detection. We end with predictions on the diagnostic future of protein detection.

Detection of electrochemiluminescence from floating metal platelets in suspension

We present a generation of electrochemiluminescence (ECL) signal, based on square shaped gold electrodes with a size of 50 μm positioned inside a fused silica capillary. The ECL was generated using electric pulses with duration in the range from 100 ms to 5 s and an electrical field strength from 300 V cm(-1) to 500 V cm(-1). We have demonstrated that the electrochemical reaction with detectable optical output can be produced using freely moving and thus disposable electrodes.

Electrochemical immunosensors for detection of cancer protein biomarkers

Bioanalytical methods have experienced unprecedented growth in recent years, driven in large part by the need for faster, more sensitive, more portable ("point of care") systems to detect protein biomarkers for clinical diagnosis. Electrochemical detection strategies, used in conjunction with immunosensors, offer advantages because they are fast, simple, and low cost. Recent developments in electrochemical immunosensors have significantly improved the sensitivity needed to detect low concentrations of biomarkers present in early stages of cancer. Moreover, the coupling of electrochemical devices with nanomaterials, such as gold nanoparticles, carbon nanotubes, magnetic particles, and quantum dots, offers multiplexing capability for simultaneous measurements of multiple cancer biomarkers. This review will discuss recent advances in the development of electrochemical immunosensors for the next generation of cancer diagnostics, with an emphasis on opportunities for further improvement in cancer diagnostics and treatment monitoring. Details will be given for strategies to increase sensitivity through multilabel amplification, coupled with high densities of capture molecules on sensor surfaces. Such sensors are capable of detecting a wide range of protein quantities, from nanogram to femtogram (depending on the protein biomarkers of interest), in a single sample.

Detection of Prorocentrum minimum (Pavillard) Schiller with an electrochemiluminescence-molecular probe assay

The occurrence of harmful algal blooms (HABs) caused by Prorocentrum minimum (Pavillard) Schiller is a crucial subject in the study of HABs. An electrochemiluminescence-molecular probe assay (ECL-MP) was developed to qualitatively and quantitatively detect P. minimum. It was based on the sandwich hybridization integrated with a nuclease protection assay (NPA-SH) and improved by electrochemiluminescence (ECL). An ECL analyzer was established in this study, and it was shown that this analyzer was stable and highly sensitive, with a detection range of 0.4 pmol to 4 nmol Ru(bpy)(3)Cl(2)·6H(2)O under optimal reaction conditions of 1.0 V, 1.0 mA, 1.5 mol·L(-1) TPrA, and pH 7.4. The optimal amount of magnetic beads for separation of labeled NPA probes in a 20-μL hybridization mixture was 4 μg. The ECL counts per second was linear with the number of P. minimum cells in a range of 6.25 × 10(2) to 4 × 10(4), and there was no significant difference between ECL-MP and microscopy, with a 95% confidence level (t test) when individual, mixed cultures and field samples were treated. This study provides a convenient method for fast and accurate detection of P. minimum in the marine environment.

Cancer prognostics by direct detection of p53-antibodies on gold surfaces by impedance measurements

The identification and measurement of biomarkers is critical to a broad range of methods that diagnose and monitor many diseases. Serum auto-antibodies are rapidly becoming interesting targets because of their biological and medical relevance. This paper describes a highly sensitive, label-free approach for the detection of p53-antibodies, a prognostic indicator in ovarian cancer as well as a biomarker in the early stages of other cancers. This approach uses impedance measurements on gold microelectrodes to measure antibody concentrations at the picomolar level in undiluted serum samples. The biosensor shows high selectivity as a result of the optimization of the epitopes responsible for the detection of p53-antibodies and was validated by several techniques including microcontact printing, self-assembled-monolayer desorption ionization (SAMDI) mass spectrometry, and adhesion pull-off force by atomic force microscopy (AFM). This transduction method will lead to fast and accurate diagnostic tools for the early detection of cancer and other diseases.

Ultrasensitive aptamer-based bio bar code immunomagnetic separation and electrochemiluminescence method for the detection of protein

An ultrasensitive aptamer-based bio bar code immunomagnetic separation and electrochemiluminescence (IM-ECL) method for the detection of protein is developed. The target protein is captured by biotin-labeled aptamer (biotin probe) and [Ru(bpy)(3)](2+) (TBR)-Au bio bar code-labeled aptamer (ECL nanoprobe), to form a double aptamer-protein sandwich complex. The complex is then immobilized on the streptavidin microbeads through biotin-streptavidin linkage and detected by ECL assay. The ECL signal of the target protein is amplified by the TBR-bio bar code DNAs. As an example, platelet-derived growth factor B-chain homodimer (PDGF-BB) was detected by the method. Experimental results show that the detection limit of the assay is 1 pM of PDGF-BB. A calibration curve with a linearity range from 1 pM to 10 nM is established, thus, make quantitative analysis possible. The method has been used to detect PDGF-BB in fetal calf serum with minimum background interference. Due to the wide availability of aptamer for numerous proteins, this aptamer-based bio bar code IM-ECL method holds great promise in protein detection.

SERS-based nanobiosensing for ultrasensitive detection of the p53 tumor suppressor

BACKGROUND

One of the main challenges in biomedicine is improvement of detection sensitivity to achieve tumor marker recognition at a very low concentration when the disease is not significantly advanced. A pivotal role in cancer defense is played by the p53 tumor suppressor, therefore its detection with high sensitivity may contribute considerably to early diagnosis of cancer. In this work, we present a new analytical method based on surface-enhanced Raman spectroscopy which could significantly increase the sensitivity of traditional bioaffinity techniques. p53 molecules were anchored to gold nanoparticles by means of the bifunctional linker 4-aminothiophenol (4-ATP). The characteristic vibrational bands of the p53-4-ATP nanoparticle system were then used to identify the p53 molecules when they were captured by a recognition substrate comprising a monolayer of azurin in molecules possessing significant affinity for this tumor suppressor. The Raman signal enhancement achieved by 4-ATP-mediated crosslinking of p53 to 50 nm gold nanoparticles enabled detect of this protein at a concentration down to 5 × 10⁻¹³ M.

Sensitive and isothermal electrochemiluminescence gene-sensing of Listeria monocytogenes with hyperbranching rolling circle amplification technology

Listeria monocytogenes (L. monocytogenes) is one of the most problematic human pathogens, as it is mainly transmitted through the food chain and cause listeriosis. Thus, specific and sensitive detection of L. monocytogenes is required to ensure food safety. In this study, we proposed a method using hyperbranching rolling circle amplification (HRCA) combined with magnetic beads based electrochemiluminescence (ECL) to offer an isothermal, highly sensitive and specific assay for the detection of L. monocytogenes. At first, a linear padlock probe was designed to target a specific sequence in the hly gene which is specific to L. monocytogenes and then ligated by Taq DNA ligase. After ligation and digestion, further amplification by HRCA with a biotiny labeled primer and a tris (bipyridine) ruthenium (TBR) labeled primer was performed. The resulting HRCA products were then captured onto streptavidin-coated paramagnetic beads and were analyzed by magnetic beads based ECL platform to confirm the presence of targets. Through this approach, as low as 10 aM synthetic hly gene targets and about 0.0002 ng/μl of genomic DNA from L. monocytogenes can be detected, the ability to detect at such ultratrace levels could be attributed to the powerful amplification of HRCA and the high sensitivity of current magnetic bead based ECL detection platform.

Magnetic beads based rolling circle amplification-electrochemiluminescence assay for highly sensitive detection of point mutation

The identification of point mutations is particularly essential in the fields of medical diagnosis and prognosis of many pathogenic and genetic diseases. In this study, an rolling circle amplification (RCA) based electrochemiluminescence (ECL) assay for highly sensitive point mutation detection was developed. In the assay, an allele-discriminating padlock probe was designed for targeting the sequence in the p53 oncogene locus. A circular template generated by enzymatic ligation upon the recognition of a point mutation (CGT to CAT) on the oncogene could be amplified isothermally by Phi 29 DNA polymerase. The elongated products, containing hundreds of copies of the circular DNA template sequence, were hybridized with Ru(bpy)(3)(2+) (TBR)-tagged probes and then captured onto streptavidin-coated paramagnetic beads. The resulting products were analyzed by magnetic bead based ECL platform. As low as 2 amol of mutated strands was detected by this assay, which could be attributed to the high amplification efficiency of Phi 29 DNA polymerase and current magnetic bead based ECL detection platform. In addition, the positive mutation detection was achieved with a wild-type to mutant ratio of 10000:1, due to the high fidelity of DNA ligase in differentiating mismatched bases at the ligation site. It is demonstrated that this proposed method provides a highly sensitive and specific approach for point mutation detection.

PCR-free detection of genetically modified organisms using magnetic capture technology and fluorescence cross-correlation spectroscopy

The safety of genetically modified organisms (GMOs) has attracted much attention recently. Polymerase chain reaction (PCR) amplification is a common method used in the identification of GMOs. However, a major disadvantage of PCR is the potential amplification of non-target DNA, causing false-positive identification. Thus, there remains a need for a simple, reliable and ultrasensitive method to identify and quantify GMO in crops. This report is to introduce a magnetic bead-based PCR-free method for rapid detection of GMOs using dual-color fluorescence cross-correlation spectroscopy (FCCS). The cauliflower mosaic virus 35S (CaMV35S) promoter commonly used in transgenic products was targeted. CaMV35S target was captured by a biotin-labeled nucleic acid probe and then purified using streptavidin-coated magnetic beads through biotin-streptavidin linkage. The purified target DNA fragment was hybridized with two nucleic acid probes labeled respectively by Rhodamine Green and Cy5 dyes. Finally, FCCS was used to detect and quantify the target DNA fragment through simultaneously detecting the fluorescence emissions from the two dyes. In our study, GMOs in genetically engineered soybeans and tomatoes were detected, using the magnetic bead-based PCR-free FCCS method. A detection limit of 50 pM GMOs target was achieved and PCR-free detection of GMOs from 5 microg genomic DNA with magnetic capture technology was accomplished. Also, the accuracy of GMO determination by the FCCS method is verified by spectrophotometry at 260 nm using PCR amplified target DNA fragment from GM tomato. The new method is rapid and effective as demonstrated in our experiments and can be easily extended to high-throughput and automatic screening format. We believe that the new magnetic bead-assisted FCCS detection technique will be a useful tool for PCR-free GMOs identification and other specific nucleic acids.

Nano-ELISA for highly sensitive protein detection

Highly sensitive protein detection method based on nanoparticles and enzyme-linked immunosorbent assays (ELISAs), named Nano-ELISA, was introduced. In this method, the micro-magnetic beads were modified with monoclonal antibody of the target protein p53. Gold nanoparticles (AuNPs) were modified with another monoclonal detector antibody and Horseradish peroxidase (HRP, for signal amplification). The presence of target protein p53 causes the formation of the sandwich structures (magnetic beads-target protein-AuNP probes) through the interaction between the antibodies and the antigen p53. The HRP at the surface of AuNPs catalytically oxidize the substrate and generate optical signals that reflected the quantity of the target protein. Down to 5 pg mL(-1) of protein was detected in less than 2 h with this method. The detection sensitivity of p53 classic ELISA kit is 0.125 ng mL(-1). This method is as simple as ELISA and has higher sensitivity than ELISA, which can potentially be exploited in clinic. This method can be used to detect protein markers of tumors, nervous system or other diseases for early diagnostics.

Competitive electrochemiluminescence wash and no-wash immunoassays for detection of serum antibodies to smooth Brucella strains

Brucellosis is a bacterial zoonotic disease of major global importance. Natural hosts for Brucella species include animals of economic significance, such as cattle and small ruminants. Controlling brucellosis in natural hosts by high-throughput serological testing followed by the slaughter of seropositive animals helps to prevent disease transmission. This study aimed to convert an existing competitive enzyme-linked immunosorbent assay (cELISA), used for the serodiagnosis of brucellosis in ruminants, to two electrochemiluminescence (ECL) immunoassays on the Meso Scale Discovery (MSD) platform. The first assay employed a conventional plate washing step as part of the protocol. The second was a no-wash assay, made possible by the proximity-based nature of ECL signal generation by the MSD platform. Both ECL wash and no-wash assays closely matched the parent cELISA for diagnostic sensitivity and specificity. The results also demonstrated that both ECL assays met World Organization for Animal Health (OIE) standards, as defined by results for the OIE standard serum (OIEELISA(SP)SS). This report is the first to describe an ECL assay incorporating lipopolysaccharide, an ECL assay for serodiagnosis of a bacterial infectious disease, a separation-free (no-wash) ECL assay for the detection of serum antibodies, and the use of the MSD platform for serodiagnosis. The simple conversion of the cELISA to the MSD platform suggests that many other serodiagnostic tests could readily be converted. Furthermore, the alignment of these results with the multiplex capability of the MSD platform offers the potential of no-wash multiplex assays to screen for several diseases.

Multiplex immunoassay for serological diagnosis of Mycobacterium bovis infection in cattle

Efforts to develop a better diagnostic assay for bovine tuberculosis have shown that the sensitivity and specificity of an assay can be improved by the use of two or more antigens. As reported here, we developed a multiplex chemiluminescent immunoassay that can simultaneously detect antibody activity to 25 antigens in a single well in a 96-well plate array format. The chemiluminescent signal is captured with a digital imaging system and analyzed with a macro program that tracks each serum for its pattern of antibody activity for Mycobacterium bovis antigens. The comparison of sera from 522 infected and 1,489 uninfected animals showed that a sensitivity of 93.1% and a specificity of 98.4% can be achieved with a combination of antigens. The assay system is rapid and can be automated for use in a centralized laboratory.

Development of magnetic particle-based chemiluminescence enzyme immunoassay for the detection of 17beta-estradiol in environmental water

In the present work, a simple, fast, and highly sensitive chemiluminescence enzyme immunoassay for 17beta-estradiol (E2) in environmental water samples was developed, using magnetic particles (MPs) labeled with secondary antibody as both the immobilization matrix and the separation tools. The specific anti-E2 polyclonal antibody (PcAb) was produced against a conjugate of estradiol-bovine serum albumin. The specificity of the anti-E2 antibody was studied. The results showed that the antibody did not cross-react with the structurally related endocrine-disrupting compounds, including estrone, ethinyl E2, estriol, E2-17-glucuronide, E2-3-sulfate-17-glucuronide, androstenedione, and dihydrotestosterone. The water samples were pretreated with solid-phase extraction using C18 cartridges for the removal of matrix effects. Several physicochemical parameters including the dilution ratios of E2-6-horseradish peroxidase conjugate and anti-E2 PcAb, immunoreaction time, volume of chemiluminescent substrate and MPs, chemiluminescence reaction time, and pH of assay solution were studied and optimized. At optimal experimental conditions, it was found that the proposed method exhibited high performance with detection limit of 2.0 pg/mL, linear range of 20-1,200 pg/mL, and total assay time of 45 min. Both inter- and intra-assay coefficient of variation were less than 10%. The average recoveries of three different spiked concentration samples ranged from 86.3% to 108%. The method was successfully applied to the determination of E2 in river, waste, and tap water, and showed a good correlation with the commercially available radioimmunoassay kit.

A highly sensitive particle agglutination assay for the detection of P53 autoantibodies in patients with lung cancer

BACKGROUND

Numerous assays have been described for the detection of p53 autoantibodies. These assays are highly specific with low sensitivity. In this report, the authors describe a highly sensitive and simple particle agglutination immunoassay using superparamagnetic particles for capturing p5 autoantibodies, p53 protein, and p53 protein-antibody complexes from large volumes of serum samples (2 mL).

METHODS

Superparamagnetic particles were coated with different peptides spanning the entire p53 protein. These particles were incubated with serum samples from healthy blood donors (n=180), from patients without malignancies (n=27), and from patients with various forms of lung cancer (n=166). The particles were washed and placed into the reaction chamber of a gel card. After centrifugation, agglutination results were read visually. Positive reactions were defined by a layer of particles on top of the gel or agglutinated particles dispersed through the gel matrix.

RESULTS

Depending on the peptide used, p53 autoantibodies were detected in from 17.5% to 35% of the investigated patients with lung cancer. By using a commercially available enzyme-linked immunoadsorbent assay (ELISA) kit, p53 autoantibodies were detected in only 3% of those patients. P53 protein and p53 protein-antibody complexes were not detected in patients with lung cancer (n=20).

CONCLUSIONS

The newly developed assay was easy to perform and had sensitivity superior to that of the currently available p53 ELISAs.

An improved electrochemiluminescence polymerase chain reaction method for highly sensitive detection of plant viruses

Recently, we have reported an electrochemiluminescence polymerase chain reaction (ECL-PCR) method for detection of genetically modified organisms. The ECL-PCR method was further improved in the current study by introducing a multi-purpose nucleic acid sequence that was specific to the tris(bipyridine) ruthenium (TBR) labeled probe, into the 5' terminal of the primers. The method was applied to detect plant viruses. Conserved sequence of the plant viruses was amplified by PCR. The product was hybridized with a biotin labeled probe and a TBR labeled probe. The hybridization product was separated by streptavidin-coated magnetic beads, and detected by measuring the ECL signals of the TBR labeled. Under the optimized conditions, the experiment results show that the detection limit is 50 fmol of PCR products, and the signal-to-noise ratio is in excess of 14.6. The method was used to detect banana streak virus, banana bunchy top virus, and papaya leaf curl virus. The experiment results show that this method could reliably identity viruses infected plant samples. The improved ECL-PCR approach has higher sensitivity and lower cost than previous approach. It can effectively detect the plant viruses with simplicity, stability, and high sensitivity.

Chemiluminescent optical fiber immunosensor for detection of autoantibodies to ovarian and breast cancer-associated antigens

We report herein the development of an optical fiber based chemiluminescent immunosensor for detection of the native autoimmune response to GIPC-1, a PDZ containing protein involved in regulation of G-protein signaling. The recombinant protein GIPC-1 was expressed in bacteria, purified, refolded and conjugated to the tip of an optical fiber. A human monoclonal 27.B1 IgM isolated from a breast cancer patient, which targets the GIPC-1 protein, was used for calibration of the immunosensor and was detected down to a concentration of 30 pg/ml. We determined that the fiber-optic immunosensor had a detection limit 50 times lower than chemiluminescent ELISA, and approximately 500 times lower than colorimetric ELISA. In addition, sera from 11 ovarian cancer patients, 22 breast cancer patients and asymptomatic controls were tested for the presence of IgM anti-GIPC-1 autoantibodies in their serum using the two methods. The immunosensor assay detected 54% and 77% GIPC-1 positive sera within ovarian and breast cancer patients, respectively, as compared to chemiluminescent ELISA, which only detected 18% and 27%, respectively. We envision that this immunosensor may serve as a diagnostic tool for screening women for ovarian and breast cancer at an early stage, thus increasing their chance of survival.

Titration of serum p53 antibodies in patients with gastric cancer: a single-institute study of 40 patients

BACKGROUND

Alterations of the p53 tumor suppressor gene are the most commonly observed genetic abnormalities in many different types of human malignancies. The accumulation of mutant p53 often leads to the production of p53 antibody (p53-Ab) in the sera of patients with various cancers. To evaluate the clinical implications of serum p53-Abs in patients with gastric cancer, we compared p53-Abs with conventional tumor markers such as carcinoembryonic antigen (CEA) and carbohydrate antigen (CA)19-9.

METHODS

Serum samples were obtained preoperatively from 40 patients with histologically confirmed gastric adenocarcinoma, including 28 (70%) patients in stage Ia. The serum p53-Abs were assessed by enzyme-linked immunosorbent assay, using a new version of a highly specific, quantitative p53-Abs Kit (MESACUP Kit II).

RESULTS

p53-Abs were detected in 6 (15%) of 40 patients with gastric cancer, including 3 patients with early gastric cancer. Seven (17.5%) of the 40 patients were positive for CEA in serum. However, none of 7 patients with high CEA levels were positive for p53-Abs. No significant correlation of p53-Abs with patient age, sex, pathological parameters, tumor markers such as CEA and CA19-9, or poor survival (P = 0.116) was observed.

CONCLUSION

Although we employed the latest version of the p53-Abs Kit, the sensitivity of serum p53-Ab in gastric cancer patients was relatively low. No correlation was found between the presence of p53-Ab and the staging of cancer or survival. However, serum p53-Ab was detectable in patients with gastric cancer even in the early stages of disease. In addition, it may be independent of CEA and CA19-9.

A method to quantitatively detect H-ras point mutation based on electrochemiluminescence

Conventional methods for point mutation detection are usually multi-stage, laborious, and need to use radioactive isotopes or other hazardous materials, and the assay results are often semi-quantitative. In this work, a protocol for quantitative detection of H-ras point mutation was developed. Electrochemiluminescence (ECL) assay was coupled with restriction endonuclease digestion directly from PCR products. Only the wild-type amplicon containing the endonuclease's recognition site can be cut off, and thus cannot be detected by ECL assay. Using the PCR-ECL method, 30 bladder cancer samples were analyzed for possible point mutation at codon 12 of H-ras oncogene. The results show that the detection limit for H-ras amplicon is 100 fmol and the linear range is more than three orders of magnitude. The point mutation was found in 14 (46.7%) out of 30 bladder cancer samples. The experiment results demonstrate that the PCR-ECL method is a feasible quantitative approach for point mutation detection due to its safety, high sensitivity, and simplicity.