Fluorescence imaging and engineered biosensors: functional and activity-based sensing using high content screening

Analysis of cellular events using CellCard™ System in cell-based high-content multiplexed assays

High-content screening technologies utilize assays that monitor and quantify multiple cellular events. These assays are typically performed on a single cell type with automated microscopy and image analysis. However, in order to better understand the selectivity of a compound across multiple cell lines, these types of assay must be run serially, which is time consuming. The CellCard System developed by Vitra Bioscience enables multiple cell types to be assayed within a single microtiter well, thereby enabling the simultaneous determination of cellular responses across ten cell types. This multiplexed approach could address the demand for assay capacity, increase the quality of the biologic data, reduce timelines, and improve cost-effectiveness in hit identification and lead evaluation. The authors have carried out an in-depth evaluation of this technology platform using ten cancer cell lines and a library of compounds that affect cellular growth through different mechanisms. Multiple assays were used to investigate the compound effects on membrane integrity, cell cycle progression and apoptosis. In this technology review, the authors discuss personal experience with assay validation, data analysis, results such as cell type-specific compound effects, and the potential application of the CellCard System in drug discovery.

PTP1B-dependent insulin receptor phosphorylation/residency in the endocytic recycling compartment of CHO-IR cells

Insulin binds to the alpha subunit of the insulin receptor (IR) on the cell surface. The insulin-IR complex is subsequently internalized and trafficked within the cell. Endocytosed receptors, devoid of insulin, recycle back to the plasma membrane through the endocytic recycling compartment (ERC). Using a high content screening system, we investigate the intracellular trafficking of the IR and its phosphorylation state, within the ERC, in response to protein tyrosine phosphatase-1B (PTP1B) inhibition. Insulin stimulates, in a time- and dose-dependent manner, the accumulation of phosphorylated IR (pY(1158,1162,1163 IR) in the ERC of CHO-IR cells. Treatment of CHO-IR cells with PTP1B-specific inhibitors or siRNA leads to dose-dependent increases in IR residency and phosphorylation within the ERC. The results also demonstrate that PTP1B redistributes within CHO-IR cells upon insulin challenge. The established system will allow for efficient screening of candidate inhibitors for the modulation of PTP1B activity.

Organotypic cultures as tools for functional screening in the CNS

A major challenge for the pharmaceutical industry is the development of relevant model systems in which knowledge gained from high-throughput, genomic and proteomic approaches can be integrated to study function. Animal models are still the main choice for such studies but over the past few years powerful new in vitro systems have begun to emerge as useful tools to study function. Organotypic cultures made from slices of explanted tissue represent a complex multi-cellular in vitro environment with the potential to assess biological function and are uniquely placed to act as an important link between high-throughput approaches and animal models.

Cellular imaging in drug discovery

Traditional screening paradigms often focus on single targets. To facilitate drug discovery in the more complex physiological environment of a cell or organism, powerful cellular imaging systems have been developed. The emergence of these detection technologies allows the quantitative analysis of cellular events and visualization of relevant cellular phenotypes. Cellular imaging facilitates the integration of complex biology into the screening process, and addresses both high-content and high-throughput needs. This review describes how cellular imaging technologies contribute to the drug discovery process.

Assembly of multicellular constructs and microarrays of cells using magnetic nanowires

An approach is described for controlling the spatial organization of mammalian cells using ferromagnetic nanowires in conjunction with patterned micromagnet arrays. The nanowires are fabricated by electrodeposition in nanoporous templates, which allows for precise control of their size and magnetic properties. The high aspect ratio and large remanent magnetization of the nanowires enable suspensions of cells bound to Ni nanowires to be controlled with low magnetic fields. This was used to produce one- and two-dimensional field-tuned patterning of suspended 3T3 mouse fibroblasts. Self-assembled one-dimensional chains of cells were obtained through manipulation of the wires' dipolar interactions. Ordered patterns of individual cells in two dimensions were formed through trapping onto magnetic microarrays of ellipsoidal permalloy micromagnets. Cell chains were formed on the arrays by varying the spacing between the micromagnets or the strength of fluid flow over the arrays. The positioning of cells on the array was further controlled by varying the direction of an external magnetic field. These results demonstrate the possibility of using magnetic nanowires to organize cells.

Exploring biology with small organic molecules

Small organic molecules have proven to be invaluable tools for investigating biological systems, but there is still much to learn from their use. To discover and to use more effectively new chemical tools to understand biology, strategies are needed that allow us to systematically explore 'biological-activity space'. Such strategies involve analysing both protein binding of, and phenotypic responses to, small organic molecules. The mapping of biological-activity space using small molecules is akin to mapping the stars--uncharted territory is explored using a system of coordinates that describes where each new feature lies.

Designing screens: how to make your hits a hit

The basic goal of small-molecule screening is the identification of chemically 'interesting' starting points for elaboration towards a drug. A number of innovative approaches for pursuing this goal have evolved, and the right approach is dictated by the target class being pursued and the capabilities of the organization involved. A recent trend in high-throughput screening has been to place less emphasis on the number of data points that can be produced, and to focus instead on the quality of the data obtained. Several computational and technological advances have aided in the selection of compounds for screening and widened the variety of assay formats available for screening. The effect on the efficiency of the screening process is discussed.

Tissue engineering and reparative medicine

Reparative medicine is a critical frontier in biomedical and clinical research. The National Institutes of Health Bioengineering Consortium (BECON) convened a symposium titled "Reparative Medicine: Growing Tissues and Organs," which was held on June 25 and 26, 2001 in Bethesda, Maryland. The relevant realms of cells, molecular signaling, extracellular matrix, engineering design principles, vascular assembly, bioreactors, storage and translation, and host remodeling and the immune response that are essential to tissue engineering were discussed. This overview of the scientific program summarizes the plenary talks, extended poster presentations and breakout session reports with an emphasis on scientific and technical hurdles that must be overcome to achieve the promise of restoring, replacing, or enhancing tissue and organ function that tissue engineering offers.