Double chip protein arrays using recombinant single-chain Fv antibody fragments

Quantification of Low Copy Number Proteins in Single Cells

We have developed an ultrasensitive and highly selective method to quantify low copy number intracellular proteins in a single cell using a low-cost laser-induced fluorescence (LIF) detector and a BV605 fluorescent probe. Active caspase3 proteins in cells were labeled by corresponding antibody-BV605 fluorescent binding, and a cell was injected into a 20 cm × 50 μm i.d. capillary column, followed by in situ lysis and capillary electrophoresis (CE)-LIF analysis. About seven active caspase3 protein molecules in a detection volume of 91 pL could be detected. In our method, cross-bounding proteins other than active caspase3 could be separated and distinguished by differences of retention time. By using Si photodiode assembly as a fluorescent detector instead of PMT, the dynamic range of the LIF is over 4 orders of magnitude. In this experiment, we found that the number of active caspase3 molecules in 98 single Jurkat cells were from 629 to 12171, reflecting significant heterogeneity among the cells although they were from the same batch. For extended application, it could also be applied to quantify other types of low copy number proteins in a single cell as long as the corresponding antibodies are provided. This high-sensitive method could also be a promising tool for earlier cancer diagnosis and related disease pathway research which is relevant to low copy number proteins. In addition, this low-cost system could also be easily expanded to an array system for high-throughput quantitation of low copy proteins in single cells.

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.

Predicting the rupture probabilities of molecular bonds in series

An assembly of two receptor ligand bonds in series will typically break at the weaker complex upon application of an external force. The rupture site depends highly on the binding potentials of both bonds and on the loading rate of the applied force. A model is presented that allows simulations of force-induced rupture of bonds in series at a given force and loading rate based on the natural dissociation rates kR0,S0 and the potential width DeltaxR,S of the reference and sample bonds. The model is especially useful for the analysis of differential force assay experiments. This is illustrated by experiments on molecular force balances consisting of two 30-bp oligonucleotide duplexes where kR0,S0 and DeltaxR,S have been determined for different single nucleotide mismatches. Furthermore, prediction of the rupture site of two bonds in series is demonstrated for DNA duplexes in combination with streptavidin/biotin and anti-digoxigenin/digoxigenin, respectively.

Oriented Immobilization of Antibodies with GST-Fused Multiple Fc-Specific B-Domains on a Gold Surface

We have constructed a novel platform for the oriented buildup of immunoglobulins on a gold surface for a surface plasmon resonance imaging microarray. To this end, genetically engineered glutathione S-transferase proteins bearing one, two, and three Fc-specific B-domains in protein G from Streptococci (GST-GB1, -GB2, and -GB3, respectively) were produced. In order to tether these GST-GBx proteins specifically, a novel glutathione-derivatized ligand (LA-GSH) was also synthesized from a biaminated tri(ethylene glycol) backbone. Each end of the backbone was further functionalized with a maleimide group for a glutathione modification and a lipoic acid for surface immobilization. The glutathione ligand demonstrated a negligible nonspecific protein adsorption toward other spectator proteins while showing a strong specific association toward GST-GBx proteins. This Fc-specific surface exhibited at least a 2-fold enhancement in the immunoglobulin density (from human and mouse) with its antigen capture capability totally conserved compared to a covalently tethered GBx proteins. A single antibody tethered on the GST-GB3 is estimated to capture two antigens (enhanced green fluorescent protein), and this antigen capture ratio seems to be the most efficient value ever observed.

Antibody microarrays: current status and key technological advances

Antibody-based microarrays are among the novel classes of rapidly evolving proteomic technologies that holds great promise in biomedicine. Miniaturized microarrays (< 1 cm2) can be printed with thousands of individual antibodies carrying the desired specificities, and with biological sample (e.g., an entire proteome) added, virtually any specifically bound analytes can be detected. While consuming only minute amounts (< microL scale) of reagents, ultra- sensitive assays (zeptomol range) can readily be performed in a highly multiplexed manner. The microarray patterns generated can then be transformed into proteomic maps, or detailed molecular fingerprints, revealing the composition of the proteome. Thus, protein expression profiling and global proteome analysis using this tool will offer new opportunities for drug target and biomarker discovery, disease diagnostics, and insights into disease biology. Adopting the antibody microarray technology platform, several biomedical applications, ranging from focused assays to proteome-scale analysis will be rapidly emerging in the coming years. This review will discuss the current status of the antibody microarray technology focusing on recent technological advances and key issues in the process of evolving the methodology into a high-performing proteomic research tool.

A cancer protein microarray platform using antibody fragments and its clinical applications

Antibody microarrays have shown great potential for measurement of either a spectrum of target proteins in proteomics or disease-associated antigens in molecular diagnostics. Despite its importance, the applications of antibody microarrays are still limited by a variety of fundamental problems. Among them, cross-reactivity significantly limits the multiplexing ability in parallel sandwich immunoassays. As a result, it is very important to design new capture probes in order to incorporate a universal label into the assay configuration. In this report, an antibody fragments (F(ab')2) microarray platform for serum tumor markers was developed. Each antigen was detected at different concentrations to assemble its calibration curve, and combinations of different markers were tested to examine the specificity of simultaneous detection based on the F(ab')2 microarrays. Diagnostics of serum samples with this cancer antibody microarray platform and immunoradiometric assays (IRMA) were also performed. Wide range calibration curves (0-1280 U mL(-1)) were obtained for each tumor marker. Comparative studies demonstrated that such F(ab')2 microarrays exhibited both moderately improved sensitivity and better specificity than full-sized monoclonal antibody microarrays. It is also demonstrated that this microarray platform is quantitative, highly specific and reasonably sensitive. More importantly, clinical applications of our F(ab')2 microarray platform for upwards of 100 patient serum samples clearly show its potential in cancer diagnostics.

Multiplexed protein measurement: technologies and applications of protein and antibody arrays

The ability to measure the abundance of many proteins precisely and simultaneously in experimental samples is an important, recent advance for static and dynamic, as well as descriptive and predictive, biological research. The value of multiplexed protein measurement is being established in applications such as comprehensive proteomic surveys, studies of protein networks and pathways, validation of genomic discoveries and clinical biomarker development. As standards do not yet exist that bridge all of these applications, the current recommended best practice for validation of results is to approach study design in an iterative process and to integrate data from several measurement technologies. This review describes current and emerging multiplexed protein measurement technologies and their applications, and discusses the remaining challenges in this field.