For those still concerned about anthrax: Soon you can be paranoid for half the price!
Researchers in UCSB’s Materials Dept. have found a new one-step test for DNA, which could identify pathogens, genetic disorders and cancerous cells more quickly and efficiently than is currently possible with conventional methods. The new one-step method is also cheaper and faster than traditional DNA testing. It has the potential to cut health care costs in the United States and, according to the researchers, could even be made cheaply enough to provide care to patients in developing countries.
Most current tests for diseases center on the body’s immune response. The reaction of the body is used to determine what is causing the problem. Recent advances in genetics may make such methods of testing obsolete.
“What’s happening with the human genome project and in laboratories all over the world is that people are discovering specific sequences of DNA and the things we can do with them are expanding every day,” said Dr. Alan Heeger, a materials researcher who worked on the project.
Diagnosing an illness increasingly involves testing for the DNA of the disease-causing pathogen. Genetic disorders also involve DNA testing because the illness results from the failure of a person’s DNA to code for specific proteins – smudges in the genetic blueprint, so to speak. Diagnosing genetic disorders requires finding the faulty portion of DNA.
Cancer is also a genetic disorder, but not a hereditary one. Cancer develops when the genes that control the pace of cell division are damaged by external influences like smoking, UV rays or excessive hot dog consumption. Cells begin to multiply out of control. They also lose their specialization – a cancerous liver cell no longer works for the liver. These clumps of unspecialized cells become foreign masses interfering with the body’s normal function.
Genetic tests can be devised for any of these types of disorders, so long as researchers know the genetic code of the pathogen or the person’s faulty DNA. Currently however, a genetic test requires several steps. The section of DNA to be tested must first be copied repeatedly by a process known as polymerase chain reaction or PCR. Only when the DNA is present in these large quantities can scientists run additional tests to identify it.
Graduate student Brent Gaylord along with Drs. Guillermo Bazan and Heeger developed the new one-step method of DNA testing. The method involves a series of specialized molecules, which are added to a liquid test sample.
The first of these molecules is called a conjugated polymer. A polymer is a long chain of small repeating molecules, which constitute one long chainlike molecule. The polymers used for genetic testing are fluorescent – they take one color of light and change it to another. Fluorescent dyes are often used in scientific experiments as indicators, and understandably so. Fluorescent colors are attention-getters because they require relatively little light to make their presence known. Example: Someone wearing a fluorescent crossing guard uniform is highly visible, even if they are only illuminated by a streetlight.
The conjugated polymers used by the researchers change blue light to green light and are particularly good indicators because of their large size. The enormous chainlike molecules can collect large quantities of light. Unfortunately, they don’t dissolve in water – a property necessary for almost any indicator used in medical lab experiments. It was discovered recently that the molecules could be made to dissolve in water by grafting positively charged chains of molecules onto the side of the main polymer-chain.
To test for DNA, these polymers are used in conjunction with another type of molecule known as peptide nucleic acid or PNA. PNA molecules are manufactured chains of molecules that pair with individual strands of DNA. The PNA molecules must be complementary to the section of DNA they are expected to pair with. PNA molecules can be designed to pair with specific parts of cancer genes, pathogen DNA, or genes associated with genetic disorders. A researcher can order a PNA molecule specific for cystic fibrosis or tuberculosis or breast cancer. The PNA molecules have no electrical charge, but the DNA molecules to which they pair have a negative charge.
In the new genetic test, a small fluorescent molecule (not the conjugated polymer) is attached to the PNA molecule. This small fluorescent molecule emits blue light. The PNA molecules are added to a test sample and given time to pair off with their target DNA sequences – if those sequences are there. Afterward, the conjugated polymers are added to the solution. Since the conjugated polymers are positively charged and the DNA-PNA pairs are negatively charged, the two are attracted to one another and will find each other in the solution. When they do, the conjugated polymers change the blue light from the PNA to green light and the sample turns green. If there is no target DNA in the solution, the sample will remain blue because the conjugated polymers and the PNA molecules never find one another.
A test for nearly any disease could become as simple as, “Is it green or is it blue?”
The researchers have applied through the University of California for patents on the new tests.
“We clearly would like to commercialize it. We have secured the intellectual property with the University of California and we are doing research into what kinds of applications would be marketable,” Bazan said.
The patent is currently provisional and will be finalized in one year. Gaylord said the researchers will attempt to find as many applications for the test as possible within that year. He is currently working on his Ph.D.
“It’s a very exciting experiment for me. Part of the beauty of research at UCSB is that it’s interdisciplinary – especially the Materials Dept. We’re dealing with biology, chemistry and engineering, so we get to do something a little bit different every day.”