Johns Hopkins chemists have discovered a new way to sabotage DNA's ability to reproduce, a finding that could eventually lead to the development of new anti-cancer drugs and therapies. The method
A team of scientists led by Dr. Kuniya Abe from the RIKEN BioResource Center in Japan has performed one of the most comprehensive genome-wide experimental analyses of sense-antisense transcrip
The University of Sheffield has received a ?2.6m grant to create some of the world's first embryonic stem cell lines that can be used for medicinal purposes.The announcement will be made at a p
Dr Paul de Souza and scientists at the Roslin Institute have successfully created human cells without using animal products.In the past there has been concern that the animal products used in
Scientists have discovered a single mutation that is responsible for a number of blood disorders, reporting their findings in this week's issue of The Lancet.Myeloproliferative disorders for
Genetically modified (GM) plants are to be used to grow vaccines for use in the worldwide fight against HIV, tuberculosis, diabetes and rabies thanks to a grant of 12 million euros from the EU's Sixth Fr
When bacteria invade the body, a molecule called CD14 binds to substances liberated from the bacteria and initiates the cellular defense mechanisms. In a report published in the Journal of Biological Chemistry, scientists in Korea announced their eluci
Injections of adult stem cells into damaged heart tissue significantly improved heart function in patients with severe congestive heart failure, according to results of the first prospective randomized trial of the experimental therapy presented today at t
Date: Tuesday, 21-Nov-2006
Saving the life of a poisoning victim is often a matter of minutes. It is best when the emergency doctor can perform a reliable diagnosis on the spot to determine which poison or what type of drug overdose a patient is suffering from. Complicated laboratory analyses and a complex apparatus are out of place in the emergency room.A team at the University of Illinois in Urbana has now laid the foundation for a new generation of rapid diagnostic tests that are as easy to handle as a pregnancy test: just dunk them in the sample and see if a colored band appears. These test strips are as reliable as laboratory methods. As a prototype, the researchers led by Yi Lu developed a test strip for the detection of cocaine in biological samples such as saliva, urine, and blood serum.
"Our method is based on tiny gold spheres and aptamers," reports Lu. Aptamers are single-stranded nucleic acid molecules that bind to certain target molecules with the same strength and specificity as antibodies. From a large number of DNA strands with random sequences (a library), it is basically possible to find a suitable aptamer for almost every target molecule. Says Lu: "The broad practical application of aptamers has thus far not realized its promise in practical diagnostics because the corresponding tests could not be made sufficiently user-friendly for the average user, who has not had laboratory training."
The new test strips for cocaine are different. When the end of the strip is dipped into a sample, the liquid travels along the strip to reach a zone with small gold-aptamer clumps. The trick lies in the special structure of these clumps: they are aggregates of nanoscopic gold spheres coupled to short DNA strands, some containing the biomolecule biotin. The DNA sequences are complementary to two regions of the cocaine-specific DNA aptamer. The aptamers bind to these strands, linking the gold spheres into larger aggregates. When the cocaine-containing liquid reaches these aggregates, the cocaine molecule instantly binds to the aptamers and removes them from the network; the aggregates fall apart into individual gold spheres. These free spheres are red. When the liquid travels further along the strip, it reaches a membrane. While the larger gold aggregates are stopped by the membrane, the red gold spheres are small enough to pass through it. They end up stuck to a narrow strip of streptavidin, a biomolecule that grabs onto the biotin on the gold surface like a hook onto an eye. The gold spheres get concentrated on the narrow strip and become visible as a distinct red stripe on the test strip.
"Our method is universal," stresses Lu. "Based on this principle, we should be able to develop rapid tests for the emergency diagnosis of a large number of drugs and poisons, as well as physiological molecules. The same method is also applicable to environmental monitoring."
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