Application of an antibody biochip for p53 detection and cancer diagnosis

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.

Multiplexed measurement of serum antibodies using an array biosensor

The array biosensor provides the capability for simultaneously measuring titers of antibody against multiple antigens. Human antibodies against four different targets, tetanus toxin, diphtheria toxin, staphylococcal enterotoxin B (SEB) and hepatitis B, were measured simultaneously in sera from eight different donors in a single assay and titers were determined. The assays could measure amounts of bound antibody as low as approximately 100 fg. Each individual serum exhibited a different pattern of reactivity against the four target antigens. Applications of this biosensor capability include monitoring for exposure to pathogens and for efficacy of vaccination.

Towards fast and inexpensive molecular diagnostic: the case of TP53

BACKGROUND

Much research suggests that TP53 mutations have prognostic importance and sometimes are a significant factor in clinical oncology. A considerable effort has been made to develop fast and inexpensive methods for TP53 mutations detection.

METHODS

On the basis of describing the role of TP53 as tumor suppressor gene and TP53 mutation spectrum, the authors discuss conventional methods and new technologies for TP53 mutations detection. This discussion is supported by more recent publications in the field of both molecular genetics and analysis technologies.

RESULTS

Biosensors and gene chips are of considerable recent interest, due to their tremendous promise for obtaining sequence-specific information in a faster, simpler and cheaper manner compared to traditional methods.

CONCLUSIONS

New methods such as biosensors and gene chips appear promising as analytical methods of detecting mutations.

Advances in recombinant antibody microarrays

Antibody microarrays, one emerging class of proteomic technologies, have broad applications in proteome analysis, disease diagnostics and quantitative analysis. Compared to DNA microarrays, protein targets have significantly more complex interactions with their ligands such as antibodies. To introduce antibody microarrays for clinical diagnostics and thus to complement or replace conventional immunoassays, several new developments are addressed. We discuss different microarray surfaces, immobilization techniques, detection systems and advantages and disadvantages of antibody microarrays compared to standard clinical techniques. Currently, the probes with highest specificity, well-characterized binding properties, and the possibility of large-scale production using display libraries are recombinant antibodies.

The design of a novel complementary metal oxide semiconductor detection system for biochemical luminescence

We designed a complementary metal oxide semiconductor (CMOS) chip with accompanied accessories as a system for the detections and quantifications of biochemical luminescence. This is the first of such instruments that has been reported. The semiconductor chip was manufactured through a 0.25 microm CMOS standard process. A current mirror was designed in integrated circuit (IC) to amplify the signal current that was induced by chemiluminescence. Horseradish peroxidase (HRP)-luminol-H2O2 system was used as an example to constitute a useful platform for coupling to chemiluminescence reactions which produce H2O2. Glucose-glucose oxidase (GOD) reaction was coupled with HRP-luminol-H2O2 reaction to demonstrate the ability of the novel CMOS base instrument for quantifying the biological luminescence of a variety of valuable clinical assays. Our results illustrated that the combination of the specifically designed CMOS IC and commercially available electronic devices established a simple and useful bioanalytical tool.

Implication of mitochondrial involvement in apoptotic activity of fragile histidine triad gene: Application of synchronous luminescence spectroscopy

The fragile histidine triad (FHIT) tumor suppressor gene incorporates the common human chromosomal fragile site at 3p14.2. The structure and expression of the FHIT gene are frequently altered in many cancers. The tumor suppressor activity of the FHIT gene has been previously demonstrated as potentially involving apoptotic induction. Here, mitochondria are implicated as being involved in the apoptotic activity of the FHIT gene. A number of morphological and biochemical events, including the disruption of the inner mitochondrial transmembrane potential (Delta Psi(m)) and the release of apoptogenic cytochrome c protein into the cytoplasm, are characteristic features of the apoptotic program. The proapoptotic activity of the FHIT gene is studied by investigating the loss of Delta Psi(m) in mitochondria and translocation of cytochrome c. Synchronous luminescence (SL) spectroscopy is applied to measure mitochondrial incorporation of rhodamine 123 for direct analysis of alterations in the mitochondrial Delta Psi(m). The SL methodology is based on synchronous excitation in which the excitation and emission wavelengths are scanned simultaneously while a constant wavelength interval is maintained between the excitation and emission monochromators. An enhanced collapse of Delta Psi(m) in apoptotically induced FHIT expressing cells compared to FHIT negative cells is observed. The loss of Delta Psi(m) is greatly restricted in the presence of the apoptotic inhibitor, cyclosporin A. Cytoplasmic translocation of cytochrome c in the FHIT expressing cells as an early event in apoptosis is also demonstrated. It is concluded that Fhit protein expression maintained apoptotic function by altering the Delta Psi(m) and by enhancing cytochrome c efflux from the mitochondria.

Microfluidic enzyme immunosensors with immobilised protein A and G using chemiluminescence detection

Affinity proteins were covalently immobilised on silicon microchips with overall dimensions of 13.1 x 3.2 mm, comprising 42 porous flow channels of 235 microm depth and 25 microm width, and used to develop microfluidic immunosensors based on horseradish peroxidase (HRP), catalysing the chemiluminescent oxidation of luminol/p-iodophenol (PIP). Different hydrophilic polymers with long flexible chains (polyethylenimine (PEI), dextran (DEX), polyvinyl alcohol, aminodextran) and 3-aminopropyltriethoxysilane (APTS) were employed for modification of the silica surfaces followed by attachment of protein A or G. The resulting immunosensors were compared in an affinity capture assay format, where the competition between the labelled antigen and the analyte for antibody-binding sites took place in the bulk of the solution. The formed immunocomplexes were then trapped by the microchip affinity capture support and the amount of bound tracer was monitored by injection of luminol, PIP and H2O2. All immunosensors were capable of detecting atrazine at the sub-microg l(-1) level. The most sensitive assays were obtained with PEI and DEX polymer modified supports and immobilised protein G, with limits of detection of 0.006 and 0.010 microg l(-1), and IC50 values of 0.096 and 0.130 microg l(-1), respectively. The protein G based immunosensors were regenerated with 0.4 M glycine-HCl buffer pH 2.2, with no loss of activity observed for a storage and operating period of over 8 months. To estimate the applicability of the immunosensors to the analysis of real samples, PEI and DEX based protein G microchips were used to detect atrazine in surface water and fruit juice, spiked with known amounts of the atrazine, giving recovery values of 87-102 and 88-124% at atrazine fortification levels of 0.5-3 and 80-240 microg l(-1), respectively.

Isolation of antigens and antibodies by affinity chromatography

Antibody-antigen binding constants are commonly strong enough for an effective affinity purification of antibodies (by immobilized antigens) or antigens (by immobilized antibodies) to work out a straightforward purification method. A drawback is that antibodies are large protein molecules and subject to denaturation under conditions required for the elution from the complex. Structures of antigens can vary but usually antigens are also equally subject to similar problems. The lability of the components can sometimes make the procedure sophisticated, but usually in all cases it is possible to find a satisfactory approach. In certain cases, specific interactions of the Fc part of antibodies are more facile to exploit for their purification.

A novel microgravimetric DNA sensor with high sensitivity

A novel method using an amplifier with a cantilever and gold nanoparticles successfully to extend the length of the target for the specific and high sensitive detection of DNA was reported. When the size of gold nanoparticle is 50 nm, a sensitivity of 10(-15)M for the single base mutation detection has been achieved.