Gene Array technology has allowed for the study of gene binding by creating thousands of potential binding sites on a single device. A limitation of the current technology is that the effects of the gene and the gene-derived proteins cannot be studied in situ the same way, thousand site cell arrays are not readily available. We propose a new device structure to study the effects of gene modification on cells. This new array technology uses electroporation to target specific areas within a cell culture for transfection of genes. Electroporation arrays will allow high throughput analysis of gene effects on a given cell's response to a stress or a genes ability to restore normal cell function in disease modeling cells. Fluorescent imaging of dye labeled indicator molecules or cell viability will provide results indicating the most effective genes. The electroporation array consists of a microelectronic circuit, ancillary electronics, protecting electrode surface for cell culturing and a perfusion system for gene or drug delivery. The advantages of the current device are that there are 3200 sites for electroporation, all or any subsets of the electrodes can be activated. The cells are held in place by the electrode material. This technology could also be applied to high throughput screening of cell impermeant drugs.
Dean Scribner, Mark Humayun, Brian Justus, Charles Merritt, Richard Klein, J. Grant Howard, Martin Peckerar, F. Keith Perkins, Lee Johnson, W Bassett, P Skeath, J Weiland, Eugene de Juan, James Finch, Roger Graham, Walter Trautfield, Scott Taylor
An important new area of biomedical engineering is the development of neural prosthesis particularly in the area of cochlear and retinal devices. An intraocular retinal prosthesis test device is currently under development at NRL/JHU. The microelectronic device has an image format of 80 x 40 unit cells interfaced to the retinal surface via an array of microwires in a glass matrix. The system architecture and technology development issues are discussed as well as the topic of biocompatibility. This test device will enable acute human experiments in an operating room environment to demonstrate a massively parallel interface between retinal tissue and a microelectronic array.
Stroke has been shown to cause exitotoxic injury, two of its manifestations being cellular and mitochondrial swelling. In vitro models of stroke attempt to reproduce the effects of stroke by treating brain tissue with excitotoxins or hypotonic solutions. To further resolve the mechanism of stroke injury, we have designed a dual-angle scatter imaging (DASI) system sensitive to particle size. The DASI system has been used with a hippocampal slice preparation to contrast cellular swelling, induced by hypotonicity, and combined cellular and mitochondrial swelling caused by excitotoxicity. We found that both hypotonic end excitotoxic treatments caused changes in light scatter. However, only excitotoxic treatment caused a significant change in DASI.
Currently, methods for the detection of brain edema in patients or laboratory experiments are invasive or inconvenient for continuous monitoring. We have performed experiments on two models of brain edema to determine the validity of differential near infrared spectroscopy (NIR) as a real-time, low cost and noninvasive method of monitoring brain edema. As a chemical in-vitro model, we prepared serial dilutions of Liposyn III, a fat emulsion, to simulate varying degrees of brain water content. NIR light at two wavelengths (703 nm and 957 nm) was used to assess water content of Liposyn solutions. We demonstrated a strong relation between wavelength specific light interactance and water content, for (n equals 4) serial dilutions from 97.6% to 80.0% water, R2 equals 0.985 plus or minus 0.017. Secondly an in vitro brain tissue model was developed to test the NIR method against wet-to-dry water content measurements. A total brain water content range of from 83.5 to 67.6 water was investigated (n equals 4). Using 695 nm and 957 nm NIR light, a correlation between NIR interactance and brain water content was again obtained, R2 equals 0.957 plus or minus 0.027. Our preliminary results suggest differential NIR spectroscopy may serve as an accurate and useful technique for monitoring surface brain edema in clinical and laboratory settings.
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