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Ultrasensitive Blood Tests

Gold nanoparticles illuminate faint traces of disease
August 21, 2012

Source: “Plasmonic Nanosensors with Inverse Sensitivity by Means of Enzyme-Guided Crystal Growth”

Small signs: Nanoscale gold stars, shown here through transmission electron microscopy, get tinged with silver in the presence of a protein related to prostate cancer.

Molly M. Stevens et al.

Nature Materials 11: 604–607

Results: A biosensor can detect prostate-specific antigen (PSA), one of the proteins that signal occurrences of prostate cancer, at concentrations of 20 molecules per milliliter of blood. This makes the sensor at least 10 times as sensitive as existing PSA tests.

Why it matters: Diseases can be easier to treat when discovered early, but it’s difficult to measure low concentrations of proteins in body fluids. In the new test, the signal gets bigger as the concentration gets smaller, making it easier to detect very low levels of the telltale protein. The researchers believe that the technique could be adapted to help doctors detect a wide array of disease markers at early stages.

Methods: The researchers modify gold nanoparticles and enzymes with antibodies that are known to bind to PSA. They add these assemblies, along with silver ions, to a sample of blood plasma. If PSA is present, the antibodies bind to it, which triggers chemical reactions that cause the silver ions to form silver metal. At low concentrations of PSA, the metal forms thin films on the gold nanoparticles, which causes a change in color that’s easy to detect.

Next steps: The researchers are looking to commercialize their work. That will require more tests to confirm the accuracy of the approach. They are also planning to use the same mechanism to detect other conditions, such as HIV infection.

Cocaine Buzz Kill

A treatment that blocks the effects of the drug could one day fight addiction

Source: “AAVrh.10-Mediated Expression of an Anti-Cocaine Antibody Mediates Persistent Passive Immunization That Suppresses Cocaine-Induced Behavior”

Ronald Crystal et al.

Human Gene Therapy 23(5): 451–459

Results: A vaccine-like treatment blocks the effects of cocaine by preventing it from crossing the blood-brain barrier. The treatment lasts for at least six months in mice.

Why it matters: There is no pharmacological treatment for cocaine addiction. Because the experimental treatment works like a vaccine, it could help break the pattern of repeated relapses by blocking the pleasurable effects of the drug over long periods of time.

Methods: Researchers had previously shown that antibodies can tightly interlock with cocaine molecules and thus prevent them from crossing into the brain. But in those experiments, the antibodies broke down within two weeks. In the new work, researchers in New York and California engineered a virus to produce the antibody continuously. A single injection of the virus was enough to block cocaine’s effects in a lasting way.

Next steps: The researchers will have to continue testing the safety of the treatment in animals before beginning human trials. If successful, the method might prove effective against heroin, nicotine, and other addictive small molecules.

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