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Aptamer Science News
APTAMERS TERMED "SMART-BOMBS"
March 2011 - Professor Wei Duan, Director of the Deakin Medical School's Nanomedicine Program, explained that the inability to target the root of the cancer means the cancer is almost impossible to kill, which is why survival rates for cancer victims remain poor overall. An important development in cancer treatment has been sited as being accomplished by medical researchers in Australia and India using a "chemical missile" (an RNA aptamer) against epithelial cell adhesion molecule (EpCAM). Dr. Duan explained, aptamers can be chemically synthesized free from cell culture-derived contaminants and can be manufactured in large amounts at relatively low cost.
"Despite technological and medical advances, the survival rates for many cancers remain poor, due partly to the inability to detect cancer early and then provide targeted treatment." Dr Duan said, "Current cancer treatments destroy the cells that form the bulk of the tumor, but are largely ineffective against the root of the cancer, the cancer stem cells. This suggests that in order to provide a cure for cancer we must accurately detect and eliminate the cancer stem cells." Professor Duan says the 'bomb' will likely come in the form of a fat particle "that can carry anti-cancer drugs or diagnostic imaging agents directly to the cancer stem cells, creating the ultimate medical smart bomb."
ATOMIC FORCES USED TO TEST TENSILE STRENGTH VARIATIONS IN APTAMERS
The Max Planck Institute for Polymer Research in Mainz, Germany has recently used an atomic force microscope to test the tensile strength of aptamers to determine how the target may relate to an aptamer's binding strength. Rüdiger Berger of the Institute for Polymer Research explains, "For example, with a defined force you can pull the aptamer without tearing it and examine how the properties of the molecule-aptamer bond changes", he continues. "The target molecule could also be changed so that it forms, for example, only two hydrogen bridge bonds with the aptamer pocket instead of three. This makes is possible to understand which bonds between the target molecule and the aptamer are significant"
PEOPLE GET PROBED USING APTAMERS
Investigators at the University of Florida and the H. Lee Moffitt Cancer Center and Research Institute in Tampa, Fla., describe their use of "DNA aptamers as molecular probes for colorectal cancer study," which they propose may also help researchers identify biomarkers associated with the disease. The team used cell-SELEX and two colorectal cancer cell lines to select a "panel of target-specific aptamers." Using flow cytometry and confocal microscopy, the team confirmed the molecules' high affinity and selectivity. The study observed a 78 percent increase in mortality for men with acute coronary syndrome, as compared with affected women, concluding that "these findings could illuminate potential mechanisms of sex differences in cardiovascular disease outcomes."
NEW DNA SENSOR ALLOWS PERSONAL GLUCOSE MONITORS TO QUANTITATIVELY MEASURE WIDE RANGE OF ANALYTES Researchers have developed a prototype platform for detecting and quantifying nonglucose targets such as recreational drugs, disease-related and other biological markers, or toxic substances in blood or serum samples. The technique developed by researchers at the University of Illinois at Urbana-Champaign is based on invertase-conjugated functional DNA sensors that are immobilized on magnetic beads. The approach converts target detection by the DNA sensor into an easily readable glucose concentration, which is directly proportional to the amount of target present in the original sample. Uses of the approach include detecting cocaine, interferon, adenosine, and uranium. They admit that the technique will need simplifying and automating for widespread use, as it currently requires two steps. However, they don't foresee this as a major issue, "just as glucose meters have been developed from complicated devices into pocket-sized meters over 30 years of progress," they point out. The wide success of PGMs is largely because of their portable size, low cost, reliable quantitative results, and simple operation. Various methods have been developed to quantitatively detect other targets of interest using simple instruments, but most of these devices have not been able to match the PGM in terms of wide availability to the public.
RESEARCHERS DEVELOP SPECTRUM OF FLUORESCENT TAGS FOR MONITORING RNA PRODUCTION AND MOVEMENT Scientists have developed the means to tag RNA with fluorophores that allows the nucleic acid molecules to be tracked as they travel through living cells. The Cornell University team claims their technique has generated a wide range of RNA-fluorophore complexes that glow in colors across the visible spectrum. The development of RNA sequences with GFP-like properties that exhibit fluorescence when bound to small molecule fluorophores has proven difficult due to issues associated with ensuring that fluorescence only occurs when the fluorophore is bound to RNA, the researchers note. Antibodies and aptamers capable of eliciting the fluorescence of conditionally fluorescent dyes have been reported, but most conditional fluorophores can also be activated nonspecifically or have other undesirable properties such as cytotoxicity.
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