Biomedical subjects

Israel Biran

Publications and source records attributed to Israel Biran.

8 recordsLinked to original sources

PubMed2005

Individual cell migration analysis using fiber-optic bundles.

In this paper we describe a novel optical fiber-based technology for analyzing cell migration. Cells were labeled with a membrane-bound fluorescent dye and distributed onto a polished optical fiber bundle. When a cell passes over one of the individual fibers in the bundle, the membrane-bound dye causes a large intensity increase, which stays for a given "residence time" until the cell departs from the fiber. Residence time increases significantly upon exposure to an antimigratory drug, indicating a decrease in cell migration. This approach provides a simple migration assay and does not require sophisticated tracking software. By using optical fiber bundles containing smaller individual fibers with higher spatial resolution, this approach was employed to develop a migration assay based on subcellular imaging. The subcellular imaging platform allows for rapid analysis of migratory potential, reducing experimental time from several hours in a standard assay to 5 min using this technology.

Cell Movement↗

PubMed2004

Monitoring aromatic hydrocarbons by whole cell electrochemical biosensors.

In this article, we describe a bacterial whole cell electrochemical biosensors system that can be used for monitoring aromatic hydrocarbons. These bacterial biosensors are based on fusions of a promoter that is sensitive to aromatic compounds (the promoter region of the xylS gene and the xylR gene coding for the transcriptional regulator of the xyl operon) to reporter genes that can be monitored electrochemically at real-time and on-line. The xylS promoter was fused upstream of two promoterless genes coding the lacZ gene and phoA. These constructs reacted specifically to aromatic compounds but not to nonaromatic compounds, and we could detect, within minutes, micromolar concentrations of different aromatic hydrocarbons such as xylene and toluene. The use of two different reporter genes allows the future construction of a multianalyte detection system for simultaneous monitoring of several pollutants. These whole cell biosensors are potentially useful for on-line and in situ detection of aromatic compounds and as early warning systems of environmental hazards.

Alkaline Phosphatase↗

PubMed2004

Simultaneously monitoring gene expression kinetics and genetic noise in single cells by optical well arrays.

An optical fiber based well array platform was used for simultaneous, dynamic gene expression monitoring from hundreds of individual live Escherichia coli cells carrying promoter-fluorescent reporter gene fusions. High information content about gene expression kinetics and cell-to-cell gene expression variability can be collected from a single experiment. These data are invaluable for investigating gene regulation and gene networks as well as for systems biology applications.

Escherichia coli↗

PubMed2004

Living bacterial cell array for genotoxin monitoring.

A biosensor composed of a high-density living bacterial cell array was fabricated by inserting bacteria into a microwell array formed on one end of an imaging fiber bundle. The size of each microwell allows only one cell to occupy each well. In this biosensor, E. coli cells carrying a recA::gfp fusion were used as sensing components for genotoxin detection. Each fiber in the array has its own light pathway, enabling thousands of individual cell responses to be monitored simultaneously with both spatial and temporal resolution. The biosensor was capable of performing cell-based functional sensing of a genotoxin with high sensitivity and short incubation times (1 ng/mL mitomycin C after 90 min). Dose-response curves for several genotoxins were obtained. The biosensors demonstrated an active sensing lifetime of more than 6 h and a shelf lifetime of two weeks.

Bacteria↗

PubMed2003

Optical imaging fiber-based live bacterial cell array biosensor.

A live cell array biosensor was fabricated by immobilizing bacterial cells on the face of an optical imaging fiber containing a high-density array of microwells. Each microwell accommodates a single bacterium that was genetically engineered to respond to a specific analyte. A genetically modified Escherichia coli strain, containing the lacZ reporter gene fused to the heavy metal-responsive gene promoter zntA, was used to fabricate a mercury biosensor. A plasmid carrying the gene coding for the enhanced cyan fluorescent protein (ECFP) was also introduced into this sensing strain to identify the cell locations in the array. Single cell lacZ expression was measured when the array was exposed to mercury and a response to 100nM Hg(2+) could be detected after a 1-h incubation time. The optical imaging fiber-based single bacterial cell array is a flexible and sensitive biosensor platform that can be used to monitor the expression of different reporter genes and accommodate a variety of sensing strains.

Adenosine Triphosphatases↗

PubMed2003

On-line and in situ biosensors for monitoring environmental pollution.

Efficient tools for on-line and in situ monitoring of environmental pollutants are required to provide early warning systems. In addition, such tools can contribute important information on the progress of various remediation treatments. One of the recently developed monitoring technologies involves the use of whole-cell biosensors. Such biosensors could be constructed to detect general toxicity or specific toxicity caused by one or more pollutants. Currently, a large spectrum of microbial biosensors have been developed that enable the monitoring of pollutants by measuring light, fluorescence, color or electric current. Electrochemical monitoring is of special interest for in situ measurements as it can be performed using simple, compact and mobile equipment and is easily adaptable for on-line measurements. Here we survey the potential application of electrochemical biosensors in monitoring of general toxicity as well as hydrocarbons and heavy metals.

Bacteria↗

PubMed2002

Optical imaging fiber-based single live cell arrays: a high-density cell assay platform.

A high-density, ordered array containing thousands of microwells is fabricated on an optical imaging fiber. Each individually addressable microwell is used to accommodate a single living cell. A charged coupled device (CCD) detector is employed to monitor and spatially resolve the fluorescence signals obtained from each individual cell, allowing simultaneous monitoring of cellular responses of all the cells in the array using reporter genes (lacZ, EGFP, ECFP, DsRed) or fluorescent indicators. Yeast and bacteria cell arrays were fabricated and used to perform multiplexed cell assays with resolution at the single-cell level. Monitoring gene expression in single yeast cells carrying a two-hybrid system was used to detect in vivo protein-protein interactions. The single-cell array technology provides a new platform for monitoring the unique multiple responses of large populations of individual cells from different strains or cell lines. The rich data acquired by the cell array has the potential to be employed as a new tool for cell biology research as well as to improve cell-based high-throughput screening (HTS) applications, such as the validation of new disease-associated cellular targets and the early-stage evaluation of potential drug candidates.

Escherichia coli↗

PubMed1999

On-line monitoring of gene expression.

Gene expression in cultures of Escherichia coli has been determined in situ and on-line by the use of an electrochemical sensor. Intact bacteria were used to monitor the induction of the lacZ gene; the onset of stationary phase was also monitored, using a reporter gene fused to the RpoS-dependent promoter of the osmY gene. The technique described can in principle be used to determine the activity of any promoter, with a variety of reporter genes. This technology is non-intrusive, allows real-time monitoring of gene expression, and will be useful in the study of growth regulation and development.

Biosensing Techniques↗