Monique
May24-04, 07:20 AM
Injectable Medibots: Programmable DNA could diagnose and treat cancer - Science News Online (http://www.sciencenews.org/articles/20040501/fob1.asp)
To detect changes in gene activity, the researchers designed their computer to have three components. The first consists of short strands of DNA, called transition molecules, that bind to a segment of the messenger RNA that each cancer gene produces. For their experiments, the scientists synthesized those segments and put various amounts of them into test tubes to simulate the presence or absence of cancer.
The second component is a computation module made up of a long DNA strand. It contains a series of nodes, each of which participates in a logic operation that determines a diagnosis from the RNA in the test tube. Each operation relies on a series of reactions in which the transition molecules direct an enzyme to cut the module in one place or another. This long DNA strand also harbors the computer's third component, a therapeutic fragment of DNA that binds to and suppresses the activity of a disease-causing gene.
In a positive diagnosis of malignancy, the computer's transition molecules detect changes in the activity of all four of a cancer's genes. When the molecules determine that all four genes have abnormal activities, the enzyme cuts the computation module so that it releases the drug.
However, even if the activity of only one of the four genes is normal, the diagnosis is "not cancerous." In these cases, the enzyme cuts off a different strand of the computer's DNA, which neutralizes the drug. If the computer releases the drug by accident, a separate component keeps the system in check by simultaneously releasing the drug suppressor.
The researchers describe their computer in an upcoming Nature.
[continued] (http://www.sciencenews.org/articles/20040501/fob1.asp)
To detect changes in gene activity, the researchers designed their computer to have three components. The first consists of short strands of DNA, called transition molecules, that bind to a segment of the messenger RNA that each cancer gene produces. For their experiments, the scientists synthesized those segments and put various amounts of them into test tubes to simulate the presence or absence of cancer.
The second component is a computation module made up of a long DNA strand. It contains a series of nodes, each of which participates in a logic operation that determines a diagnosis from the RNA in the test tube. Each operation relies on a series of reactions in which the transition molecules direct an enzyme to cut the module in one place or another. This long DNA strand also harbors the computer's third component, a therapeutic fragment of DNA that binds to and suppresses the activity of a disease-causing gene.
In a positive diagnosis of malignancy, the computer's transition molecules detect changes in the activity of all four of a cancer's genes. When the molecules determine that all four genes have abnormal activities, the enzyme cuts the computation module so that it releases the drug.
However, even if the activity of only one of the four genes is normal, the diagnosis is "not cancerous." In these cases, the enzyme cuts off a different strand of the computer's DNA, which neutralizes the drug. If the computer releases the drug by accident, a separate component keeps the system in check by simultaneously releasing the drug suppressor.
The researchers describe their computer in an upcoming Nature.
[continued] (http://www.sciencenews.org/articles/20040501/fob1.asp)