Assay Development
The use of microporous polymer membranes in immunoassays
    Microporous membranes have proven to be highly successful surfaces for the development of simple, rapid immunoassay delivery systems. Membranes made of nitrocellulose, currently the material of choice, can be produced with a wide range of pore sizes and treated with surfactant to optimize their performance. These membranes help create sensitive, stable, and reproducible assays. Since the first demonstration in 1979 that proteins could be transferred to microporous nitrocellulose...
Pace picks up for fetal genetic test from maternal blood
With estimates of millions of dollars in profits looming, several companies say they are close to hatching a simple maternal blood test to determine the genetic health of an unborn baby. But experts in the field warn that those on-the-brink announcements have been going on for some time now, and that the problem of harvesting substantial quantities of fetal cells from the mother's blood has yet to be solved. "Most tests I am seeing are very cumbersome," says John Stone, PhD, a...
Scientists debate means, efficacy of osteoporosis assays
Metra Biosystems, Inc. (Mountain View, CA), is banking on a big demand for finding bone problems among aging baby boomers. It has FDA clearance to market its Pyrilinks-D urinary assay, which it is promoting as a detector of bone loss. The technology relies on the measurement of levels of free deoxypyridinoline cross-links. Another urine test to detect skeletal deficiency, Osteomark, hit the U.S. medical market last spring and has been making inroads ever since, despite a strategic partnership...
Equimolar PSA assays
    The lack of specificity of PSA assays for prostate cancer can cause unnecessary anxiety for the patient with benign prostatic hyperplasia (BPH) and even prompt unnecessary surgery. New assays that detect only the enzymatically active form of this hormone promise greater specificity and less variability. ince 1981, the number of reported prostate cancer cases in the United States has increased by 50%, and the number of related deaths by 40%. Approximately 200,000 cases are reported...
Microspheres, part 2
    Note: This is the second part of a two part article. If you have not already done so, you might want to read part one of this article first. Once scientists have chosen, characterized, and cleaned the microspheres for a test or assay based on information in part 1 of this article, they must attach ligand to them and include them in a test or assay. Before attaching protein, the scientist must determine the microspheres' surface capacity for it. One gram of 1-µm polystyrene...
Microspheres, part 1
    Many diagnostic tests and assays use submicron-size uniform latex particles, or microspheres, as substrates or supports for immunologically based reactions. These range from the original "latex" agglutination tests to more recent particle-capture assays, particle immunoassays, the newest dyed-particle sandwich tests, and solid-phase assays using silica or magnetic microspheres. Before microspheres can be used in any test or assay, they must be prepared for binding and...