Antibody Probes Research Articles

Mouse-to-mouse variation in maturation heterogeneity of smooth muscle cells.

Smooth muscle cell (SMC) heterogeneity plays an important role in vascular remodeling, a life-threatening hallmark of many vascular diseases. However, the characterization of SMCs at the single-cell level is stymied by drawbacks of contemporary single-cell protein measurements, including antibody probe cross-reactivity, chemical fixation artifacts, limited isoform-specific probes, low multiplexing and difficulty sampling cells with irregular morphologies. To scrutinize healthy vessels for subpopulations of SMCs with proliferative-like phenotypes, we developed a high-specificity, multiplexed single-cell immunoblotting cytometry tool for unfixed, uncultured primary cells. We applied our assay to demonstrate maturation stage profiling of aortic SMCs freshly isolated from individual mice. After ensuring unbiased sampling of SMCs (80-120 μm in length), we performed single-SMC electrophoretic protein separations, which resolve protein signal from off-target antibody binding, and immunoblotted for differentiation markers α-SMA, CNN-1 and SMMHC (targets ranging from 34 kDa to 227 kDa). We identified a subpopulation of immature-like SMCs, supporting the recently-established mechanism that only a subset of SMCs is responsible for vascular remodeling. Furthermore, the low sample requirements of our assay enable single-mouse resolution studies, which minimizes animal sacrifice and experimental costs while reporting animal-to-animal phenotypic variation, essential for achieving reproducibility and surmounting the drawbacks of pooling primary cells from different animals.

Antigen-responsive fluorescent antibody probes generated by selective N-terminal modification of IgGs.

Novel fluorescent antibody probes, which show antigen-dependent fluorescence responses, were developed by selective N-terminal fluorescent labeling of IgG monoclonal antibodies using a reductive alkylation. Several kinds of IgG against tag peptides and small molecules were successfully utilized to detect antigens in a rapid and quantitative manner.

Secreted Tumor Antigens - Immune Biomarkers for Diagnosis and Therapy.

With the advent of immunotherapies for cancer, there is growing interest in the identification of tumor antigens. Tumor antigens are self-molecules altered through e.g. genetic mutations (neoantigens), protein truncation, protein misfolding, or abnormal posttranslational modifications. To induce an immune response, tumor antigens need to be secreted into the tumor environment and presented to the immune system in the draining lymph nodes, resulting in the generation of tumor-specific effector cells and antibodies. Cytotoxic T cells are thought to be responsible for killing of tumor cells, and several recent studies have used MS, combined with exome/transcriptome sequencing and bioinformatics, to identify their cognate peptide ligands on tumor MHC class I molecules. Circulating (serum) antibodies have been more widely used to identify tumor antigens in a range of human cancers, using 2D Western blots, immunoaffinity, and microarray technologies. More specific antibody probes have been generated by harvesting antibodies directly from antibody-secreting cells through in vitro cultures of lymph node cells (antibody-secreting cells probes) or B-cell immortalization. Further identification and characterization of tumor antigens is likely to have important implications for cancer diagnostic and biomarker discovery, immune profiling, and the development of cancer vaccines and targeted immunotherapies.

Molecular Imaging of P-glycoprotein in Chemoresistant Tumors Using a Dual-Modality PET/Fluorescence Probe.

Overexpression of P-glycoprotein (Pgp) has been considered a primary cause for multidrug resistance in a variety of cancers for three decades. However, clinical translation of Pgp targeted therapeutics has been hindered by lack of patient preselection based on the Pgp presence in tumors. We aim to develop a molecularly targeted probe for imaging tumoral Pgp in vivo with positron emission tomography (PET) and fluorescence, and to provide a tool for preselecting the patients with tumoral Pgp expression. Thus, a Pgp monoclonal antibody 15D3 was chemically modified with IRDye800 (IR800) and DOTA chelator. The specificity of the antibody conjugates DOTA-Pab-IR800 was verified in Pgp-expressing 3T3-MDR1 and control 3T3 cells. After radiolabeling with 64Cu, the probe was applied in small animal PET imaging of Pgp in a mouse xenograft model of NCI/ADR-Res cells, which are chemoresistant through overexpression of Pgp. Quantification analysis of the PET images demonstrated that the tumor uptake of the radioactive probe was 9.9 ± 1.4, 12.1 ± 1.2, and 10.5 ± 1.0%ID/g at 4, 24, and 48 h post injection. The tumor-to-muscle ratio was 20.9 at 48 h post injection based on biodistribution studies. Fluorescence imaging was performed following PET experiments, and it demonstrated excellent tumor accumulation of this dual-modality probe in the NCI/ADR-Res tumors. Further, an image-guided surgery was successfully performed using the fluorescence modality of the probe, demonstrating potential utility of this probe in image-guided surgical removal of Pgp-positive drug resistant tumors in the patients. In conclusion, this study clearly demonstrated that the Pgp-targeted antibody probe, 64Cu-DOTA-Pab-IR800, could provide a promising diagnosis tool for detection of Pgp-expressing tumors in vivo.

A novel label-free electrochemical immunosensor based on aldehyde-terminated ionic liquid

In this paper, aldehyde-terminated ionic liquid was synthesized and used to fabricate a novel label-free electrochemical immunosensor for the determination of hepatitis B surface antigen. This sensor was formed from a gold electrode which was modified with a composite film containing the aldehyde-functionalized ionic liquid incorporated into nafion and anti-hepatitis B surface antigen antibody probes. Aldehyde-functionalized ionic liquid was used not only as a substrate for antibody immobilization, but also as a good material with high electrical conductivity, which greatly simplified the process of sensor fabrication. The proposed sensor exhibited a good performance in a linear range from 0.05 to 15ngmL−1 with a detection limit of 20pgmL−1 (S/N=3) and provided a novel strategy for clinical detection due to satisfying stability, selectivity and reproducibility.

Abstract 216: Tracking expression, post-translational modifications and interactions of EGF signalling proteins in A431 cells with antibody microarrays

Abstract Elucidation of epidermal growth factor (EGF) signalling pathways in cancer cells has helped to define the mechanisms for their neoplastic transformation and potential drug targets for therapeutic intervention. Antibody microarrays are promising tools to evaluate alterations in the levels and phosphorylation status of hundreds of proteins of interest with only microgram amounts of crude cell and tissue lysate protein. However, interpretations of the results from traditional antibody microarray approaches have been hampered by the problems associated with sample preparation and protein detection, even when reliable antibodies are deployed in these arrays. The Kinex™ KAM-900P antibody microarray permitted semi-quantitative measurements of the expressions, post-translational modifications and interactions of proteins with 100 µg or less of lysate proteins. These microarrays utilize approximately 878 different pan- and phosphosite-specific antibodies for tracking protein kinases, phosphatases and other low abundance regulatory proteins. Multiple detection protocols were developed with the KAM-900P slides to enable high depth profiling of protein levels, phosphorylation and protein-protein interactions in A431 cells in response to EGF treatment. One method (KAM) involved the capture of in vitro biotin-labeled proteins, followed by their detection with a secondary dye-labeled anti-biotin antibody. False positive signals from associated proteins in complexes with the targets were reduced by chemical cleavage with NTCB prior to their capture on the array, and this also produced more uniformity of the dye signals for protein targets despite vast differences in their sizes. Transient changes in protein phosphorylation in EGF treated cells that were typically lost when processed by conventional methods were better preserved by chemical cleavage right at time of sample homogenization. Biotin-labeling and subsequent detection of the protein on the array with a dye-labeled secondary antibody further reduced non-specific background signals, allowed for a greater dynamic range of detection, and enhanced discrimination of subtle changes. In conjunction with other detection protocols, such as the usage of dye-labeled reporter antibodies for generic protein-tyrosine phosphorylation in sandwich antibody microarrays (SAM format) or generic protein phosphorylation with nanoparticles such as pAMIGO (PAM format), it is also feasible to monitor changes in general post-translational modifications of target proteins or their specific association with other adapter, scaffolding and chaperone proteins of interest for which antibody probes are available. Citation Format: Lambert Yue, Steven Pelech. Tracking expression, post-translational modifications and interactions of EGF signalling proteins in A431 cells with antibody microarrays [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 216. doi:10.1158/1538-7445.AM2017-216

Naked Eye Detection of Salmonella typhimurium Using Scanometric Antibody Probe

Salmonella is one of the most common foodborne pathogens, and Salmonella outbreaks are mostly associated with the intake of contaminated food or drink. Therefore, the rapid and sensitive on-site detection of Salmonella is very important. We report a naked eye detection method for Salmonella typhimurium using scanometric antibody probe. The antibody-attached glass substrate was treated with Salmonella typhimurium and the scanometric antibody probe was applied. After Ag enhancement of the probe, Salmonella typhimurium could be detected with the naked eye. The scanometric antibody probe was prepared by simply mixing Au nanoparticles, gold binding peptide-protein G, and antibody against Salmonella typhimurium. This probe can act as a signal enhancer and thus allows for an extremely simple, rapid, and efficient analysis of Salmonella typhimurium by the naked eye. We detected Salmonella typhimurium at a low concentration of 103 CFU/ml and clearly distinguished this bacterium from other foodborne pathogens. Furthermore, we successfully detected Salmonella typhimurium in milk, suggesting that this method can be useful in real-life samples. Because the scanometric antibody probe can be expanded to various types of antibodies, this naked eye detection method could be employed for the detection of various types of pathogens.

A Microfluidic Chip for Detecting Cholangiocarcinoma Cells in Human Bile

Cholangiocarcinoma (CCA), a biliary tract malignancy, accounts for 20% of all liver cancers. There are several existing methods for diagnosis of CCA, though they are generally expensive, laborious, and suffer from low detection rates. Herein we first developed a means of partially purifying human bile for consequent injection into a microfluidic chip. Then, the novel microfluidic system, which featured 1) a cell capture module, 2) an immunofluorescence (IF) staining module featuring two CCA-specific biomarkers, and 3) an optical detection module for visualization of antibody probes bound to these CCA marker proteins, was used to detect bile duct cancer cells within partially purified bile samples. As a proof of concept, CCA cells were successfully captured and identified from CCA cell cultures, blood samples inoculated with CCA cells, and clinical bile specimens. In 7.5 ml of bile, this system could detect >2, 0, and 1 positive cells in advanced stage patients, healthy patients, and chemotherapy-treated patients, respectively. In conclusion, our microfluidic system could be a promising tool for detection of cancer cells in bile, even at the earliest stages of CCA when cancer cells are at low densities relative to the total population of epithelial cells.

Doubly Caged Linker for AND‐Type Fluorogenic Construction of Protein/Antibody Bioconjugates and In Situ Quantification

AbstractIn situ quantification of the conjugation efficiency of azide‐terminated synthetic polymers/imaging probes and thiol‐functionalized antibodies/proteins/peptides was enabled by a doubly caged profluorescent and heterodifunctional core molecule C1 as a self‐sorting bridging unit. Orthogonal dual “click” coupling of C1 with azide‐ and thiol‐functionalized precursors led to highly fluorescent bioconjugates, whereas single‐click products remained essentially nonfluorescent. Integration with FRET processes was also possible. For the construction of antibody–probe conjugates from an anti‐carcinoembryonic antigen and a quinone‐caged profluorescent naphthalimide derivative, the dual “click” coupling process with C1 was monitored on the basis of the emission turn‐on of C1, whereas prominent changes in FRET ratios occurred for antibody–imaging‐probe conjugates when specifically triggered by quinone oxidoreductase (NQO1), which is overexpressed in various types of cancer cells.

Flashbody: A Next Generation Fluobody with Fluorescence Intensity Enhanced by Antigen Binding.

Fluorescent probes are valuable tools for visualizing the spatiotemporal dynamics of molecules in living cells. Here we developed a genetically encoded antibody probe with antigen-dependent fluorescence intensity called "Flashbody". We first created a fusion of EGFP to the single chain variable region fragment (scFv) of antibody against seven amino acids of the bone Gla protein C-terminus (BGPC7) called BGP Fluobody, which successfully showed the intracellular localization of BGPC7-tagged protein. To generate BGP Flashbody, circularly permuted GFP was inserted in between two variable region fragments, and the linkers were optimized, resulting in fluorescence intensity increase of 300% upon binding with BGPC7 in a dose-dependent manner. Live-cell imaging using BGP Flashbody showed that BGPC7 fused with cell penetrating peptide was able to enter through the plasma membrane by forming a nucleation zone, while it penetrated the nuclear membrane with different mechanism. The construction of Flashbody will be possible for a range of antibody fragments and opens up new possibilities for visualizing a myriad of molecules of interest.

Gold Nanostar Enhanced Surface Plasmon Resonance Detection of an Antibiotic at Attomolar Concentrations via an Aptamer-Antibody Sandwich Assay.

A new sandwich assay for tetracycline (TC) involving a DNA aptamer and antibody pair is demonstrated in conjunction with gold nanostar (GNS) enhanced surface plasmon resonance (SPR) to achieve detection in the low attomolar range. GNS particles were covalently functionalized with the antibody probe (antiTC) and integrated into a surface sandwich assay in conjunction with a SPR gold chip modified with the TC-specific aptamer. After it was demonstrated that both affinity probes can bind simultaneously to TC, optimization of the assay was performed using either antiTC only or GNS-antiTC conjugates to interact with aptamer/TC complexes present on the chip surface. Target concentrations as low as 10 aM could be detected using GNS-antiTC's, which was >103 times greater in performance than when using antiTC only. In addition, good selectivity was achieved with respect to other tetracycline derivative antibiotics, such as oxytetracycline (OTC) and chlortetracycline (CTC), both which are structurally similar to TC. As a demonstration of trace antibiotic analysis in environmental samples, the GNS enhanced sandwich assay was applied to analyze TC added to aliquots of local river water and the results validated by comparing to conventional high-performance liquid chromatography (HPLC) analysis.

Post-Translational Tubulin Modifications in Human Astrocyte Cultures.

The cytoskeletal protein tubulin plays an integral role in the functional specialization of many cell types. In the central nervous system, post-translational modifications and the expression of specific tubulin isotypes in neurons have been analyzed in greater detail than in their astrocytic counterparts. In this study, we characterized post-translational specifications of tubulin in human astrocytes using the normal human astrocyte (NHA; Lonza) commercial cell line of fetal origin. Immunocytochemical techniques were implemented in conjunction with confocal microscopy to image class III β-tubulin (βIII-tubulin), acetylated tubulin, and polyglutamylated tubulin using fluorescent antibody probes. Fluorescent probe intensity differences and colocalization were quantitatively assessed with the 'EBImage' package for the statistical programming language R. Colocalization analysis revealed that, although both acetylated tubulin and polyglutamylated tubulin showed a high degree of correlation with βIII-tubulin, the correlation with acetylated tubulin was stronger. Quantification and statistical analysis of fluorescence intensity demonstrated that the fluorescence probe intensity ratio for acetylated tubulin/βIII-tubulin was greater than the ratio for polyglutamylated tubulin/βIII-tubulin. The open source GEODATA set GSE819950, comprising RNA sequencing data for the NHA cell line, was mined for the expression of enzymes responsible for tubulin modifications. Our analysis uncovered greater expression at the mRNA level for enzymes reported to function in acetylation and deacetylation as compared to enzymes implicated in glutamylation and deglutamylation. Taken together, the results represent a step toward unraveling the tubulin isotypic expression profile and post-translational modification patterns in astrocytes during human brain development.

Elimination of aflatoxin B1 in vegetable oil based on immuno-magnetosomes probes from a novel magnetotactic bacterium

Here, a magnetotactic bacterium (MTB) existing in freshwaters was acclimated and mass propagations for producing natural magnetosomes with diameter about 15 nm at ordinary ambient. It was found that the magnetosomes which are mainly composed of iron oxide and iron sulfide hold pretty well magnetic features. Furthermore, the developed magnetosomes-AFB1 antibody immunomagentic probes through chemical bonding AFB1 polyclonal antibody onto the natural magnetosomes maintain 28 fold capability on collection of AFB1 toxin in vegetable oil compared to conventional Fe3O4 magnetic nanoparticle-AFB1 antibody probes. Recovery ratio up to 93.7% from commercial vegetable oil with artificial AFB1 contamination during 15 min collection were demonstrated. Through circular dichroism (CD) spectral measurements, the mechanism of magnetosomes probe was interpreted for proposing the practical way with high-performance on controlling the aflatoxins contamination in liquid foods basing on immunomagentic separation technique.

An electrode-separated piezoelectric immunosensor array with signal enhancement based on enzyme catalytic deposition of palladium nanoparticles and electroless deposition nickel-phosphorus

A differential piezoelectric immunosensor array was reported with signal enhancement based on the biometallization of palladium nanoparticles (Pd NPs) and successive electroless deposition Ni-P layer. In this strategy, the primary antibody probes were immobilized on the aminated quartz surface in an electrode-separated piezoelectric sensor (ESPS). After bounding with the corresponding antigen and alkaline phosphatase (ALP) conjugated second antibody, the ALP in the sandwich-type immunocomplex can catalyze the substrate of p-aminophenyl phosphate to generate p-aminophenol, which reduces Pd(II) in solution to Pd NPs onto the quartz surface. A successive signal amplification was performed by Pd NPs- promoted catalytic electroless deposition of Ni-P layer. A differential measurement mode was employed to eliminate the influence of non-mass effects, including the changes in conductivity, viscosity, density and temperature of the solution, as well as the baselines draft of piezoelectric sensors. The responses of the differential ESPS in fundamental frequency, third and fifth overtones were compared. The proposed method was applied to the determination of human IgG with a detection limit of 1pg/mL. Compared with biometallization of Pd NPs, the sensitivity is enhanced further by three orders of magnitude due to high activation energy in Ni-P deposition reaction and low baseline draft in differential measurement mode.

A PCR-free point-of-care capacitive immunoassay for influenza A virus

This article describes a highly sensitive and specific capacitive immunosensor for rapid, low cost and simple-to-use detection of virus particles from clinical swab samples. An inhomogeneous AC electric field is applied on sensor electrodes. This induces positive dielectrophoresis that attracts virus particles to the sensor electrodes. As a result, rapid and sensitive detection of influenza A virus is accomplished without the need for nucleotide isolation and amplification. The same AC signal is used to detect the binding of virus particle to the sensor surface immobilized with the antibody probe. The assay is highly suitable for point-of-care use. When testing clinical swab samples, the response of samples at various dilutions is analyzed, and an optimal dilution is found and used for subsequent blind tests of clinical swab samples. Analytical experiments on standard influenza virus sample demonstrate a limit of detection of 0.25 pg⋅mL−1. Other figures of merit include (a) an assay time of 30 seconds; (b) a diagnostic sensitivity of 90%; and (c) a specificity of 70%. Blind tests are conducted for a panel of twenty nasal swab samples, and the results are in good agreement with those by using the commercial reverse transcription polymerase chain reaction.

Subcellular western blotting of single cells

Although immunoassays are the de facto standard for determining subcellular protein localization in individual cells, antibody probe cross-reactivity and fixation artifacts remain confounding factors. To enhance selectivity while providing single-cell resolution, we introduce a subcellular western blotting technique capable of separately assaying proteins in the 14 pL cytoplasm and 2 pL nucleus of individual cells. To confer precision fluidic control, we describe a passive multilayer microdevice that leverages the rapid transport times afforded by miniaturization. After isolating single cells in microwells, we apply single-cell differential detergent fractionation to lyse and western blot the cytoplasmic lysate, whereas the nucleus remains intact in the microwell. Subsequently, we lyse the intact nucleus and western blot the nuclear lysate. To index each protein analysis to the originating subcellular compartment, we utilize bi-directional electrophoresis, a multidimensional separation that assays the lysate from each compartment in a distinct region of the separation axis. Single-cell bi-directional electrophoresis eliminates the need for semi-subjective image segmentation algorithms required in immunocytochemistry. The subcellular, single-cell western blot is demonstrated for six targets per cell, and successfully localizes spliceosome-associated proteins solubilized from large protein and RNA complexes, even for closely sized proteins (a 7 kDa difference). Measurement of NF-κB translocation dynamics in unfixed cells at 15-min intervals demonstrates reduced technical variance compared with immunofluorescence. This chemical cytometry assay directly measures the nucleocytoplasmic protein distribution in individual unfixed cells, thus providing insight into protein signaling in heterogeneous cell populations.

Photoacoustic and Fluorescence Imaging of Cutaneous Squamous Cell Carcinoma in Living Subjects Using a Probe Targeting Integrin \u03b1v\u03b26

Cutaneous squamous cell carcinoma (cSCC) is the second most common non-melanoma skin cancer worldwide. Today, cSCC is diagnosed by visual inspection followed by invasive skin biopsy. There is a need to develop non-invasive diagnostic tools to achieve early and accurate detection. Photoacoustic imaging (PAI) possesses high ultrasonic resolution and strong optical contrast at new depths (<1–5 cm). Together with exogenous contrast agents, PAI has found promising use in various tumors in living subjects. The expression of integrin αvβ6 is significantly up-regulated in cSCC. We fabricated an anti-integrin αvβ6 antibody and labeled it with indocyanine green (ICG) to form an ICG-αvβ6 antibody. The results showed that the ICG-αvβ6 antibody probe could be used to detect cSCC with high specificity (3-fold over the control by PAI) and deep penetration (approximately 1 cm) by PAI. This suggests that the ICG-αvβ6 antibody is a promising probe targeting the integrin αvβ6 for detection of cSCC tumors by PAI and fluorescence imaging. It may find clinical application in the early diagnosis of cSCC as well as in intraoperative navigation.

Sequential Immunofluorescent Light Microscopy and Electron Microscopy of Recombination Nodules During Meiotic Prophase I.

Immunolocalization using either fluorescence for light microscopy (LM) or gold particles for electron microscopy (EM) has become a common tool to pinpoint proteins involved in recombination during meiotic prophase. Each method has its advantages and disadvantages. For example, LM immunofluorescence is comparatively easier and higher throughput compared to immunogold EM localization. In addition, immunofluorescence has the advantages that a faint signal can often be enhanced by longer exposure times and colocalization using two (or more) probes with different absorbance and emission spectra is straightforward. However, immunofluorescence is not useful if the object of interest does not label with an antibody probe and is below the resolution of the LM. In comparison, immunogold EM localization is higher resolution than immunofluorescent LM localization, and individual nuclear structures, such as recombination nodules, can be identified by EM regardless of whether they are labeled or not. However, immunogold localization has other disadvantages including comparatively low signal-to-noise ratios, more difficult colocalization using gold particles of different sizes, and the inability to evaluate labeling efficiency before examining the sample using EM (a more expensive and time-consuming technique than LM). Here we describe a method that takes advantage of the good points of both immunofluorescent LM and EM to analyze two classes of late recombination nodules (RNs), only one of which labels with antibodies to MLH1 protein, a marker of crossovers. The method can be used readily with other antibodies to analyze early recombination nodules or other prophase I structures.

Antibody-Conjugated Single Quantum Dot Tracking of Membrane Neurotransmitter Transporters in Primary Neuronal Cultures.

Single particle tracking (SPT) experiments have provided the scientific community with invaluable single-molecule information about the dynamic regulation of individual receptors, transporters, kinases, lipids, and molecular motors. SPT is an alternative to ensemble averaging approaches, where heterogeneous modes of motion might be lost. Quantum dots (QDs) are excellent probes for SPT experiments due to their photostability, high brightness, and size-dependent, narrow emission spectra. In a typical QD-based SPT experiment, QDs are bound to the target of interest and imaged for seconds to minutes via fluorescence video microscopy. Single QD spots in individual frames are then linked to form trajectories that are analyzed to determine their mean square displacement, diffusion coefficient, confinement index, and instantaneous velocity. This chapter describes a generalizable protocol for the single particle tracking of membrane neurotransmitter transporters on cell membranes with either unmodified extracellular antibody probes and secondary antibody-conjugated quantum dots or biotinylated extracellular antibody probes and streptavidin-conjugated quantum dots in primary neuronal cultures. The neuronal cell culture, the biotinylation protocol and the quantum dot labeling procedures, as well as basic data analysis are discussed.

An advanced conjugation strategy for the preparation of quantum dot-antibody immunoprobes

An advanced site-specific conjugation strategy for the preparation of quantum dot-based antibody probes applicable in various immunoassays from fluorescence to electrochemical biosensors is described.