Hypersensitive microparticles for cancer diagnosis
microRNAs (miRNAs) discovered about 10 years ago work as "switches" that prevent the ribosome from synthesizing a protein encoded in a strictly defined gene. In cancer cells, the functioning of these small molecules can get out of control, which contributes to the rapid growth of tumors.
Researchers at the Massachusetts Institute of Technology, working under the guidance of Professor Patrick Doyle, have proposed a method for detecting abnormal miRNAs in the blood of cancer patients. Their development can form the basis of a simple method for the diagnosis and monitoring of malignant diseases.
The method consists in introducing a set of microparticles from a hydrogel, the length of which does not exceed 200 microns. Each of the particles marked with a "barcode" selectively binds to a certain type of miRNA, and not only samples of purified RNA can be used for analysis, but also simply blood plasma. Reading the labels on the particles bound to miRNA allows you to determine the presence of a cancerous tumor and its type (each type of malignant tumor is characterized by a certain composition of miRNA).
Existing methods for detecting miRNAs require a long and complex isolation of these molecules from blood or a tissue sample, so the possibility of using blood plasma (only 25 microliters are needed for its analysis) greatly simplifies and reduces the cost of the task. This possibility appeared due to the fact that the particles developed by Doyle's group consist of hydrophilic polymer chains that readily bind to nucleic acids. Millions of identical DNA fragments complementary to certain miRNA sequences are attached to each of the microparticles created by scientists. If such miRNAs are present in the blood sample, they bind to the corresponding DNA strands.
In addition, short sequences of nucleotides are embedded in these sensory DNA, binding to a fluorescent label added later. A specially designed microfluidic scanner allows you to quickly measure the level of fluorescence and determine the amount of miRNA present in the blood. It also recognizes the chemical "barcode" of each particle, thus determining the type of detected miRNA. The whole process takes less than three hours.
The new method is 100 times more sensitive and much more accurate than the existing ones. miRNAs are involved in the development of many other diseases, including HIV, Alzheimer's disease, diabetes and diseases of the cardiovascular system. In addition, it allows you to detect any miRNAs not only in plasma, but also in other biological fluids. Therefore, in the future, the scope of the new method is not limited to oncology. Professor Doyle and his former student Daniel Pregibon have already received a license for the new technology and are planning to develop systems for commercial use, the release of which will be handled by the company Firefly Bioworks founded by them.
The article by Patrick S. Doyle, and Stephen C. Chapin Ultrasensitive Multiplexed microRNA Quantification on Encoded Gel Microparticles Using Rolling Circle Amplification is published in the preliminary on-line version of the journal Analytical Chemistry.
Evgeniya Ryabtseva
Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of the Massachusetts Institute of Technology: Ultrasensitive particles offer a new way to find cancer.
01.09.2011