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Posted: October 30, 2006
Detecting rare microRNAs with gold nanoparticles
(Nanowerk News) Over the past three years, numerous studies have shown that short pieces of single-stranded RNA, known as microRNAs, play a central role in the development of at least some cancers. Now, cancer researchers have a nanoparticle-based tool for more quickly and accurately detecting the presence of specific microRNAs, a development that could lead to new diagnostic tests for cancer.
The assay relies on the ability of commercially available, DNA-like molecules known as locked nucleic acids to bind with incredible strength to microRNAs. The investigators first create an array of locked nucleic acids immobilized onto a solid substrate. They then add the microRNAs-containing sample to this array and allow hybridization to take place between the locked nucleic acids and any microRNAs.
Next, the investigators use an enzyme known as poly(A) polymerase to add a long tail of adenine (A) to the end of any bound microRNAs molecules. Finally, they add gold nanoparticles coated with strands of thymine (T) – thymine and adenine are complementary nucleic acid, so the poly(T) strands bind strongly to any poly(A) tails extended from microRNAs. The attached gold nanoparticles are easily detected and quantified using surface plasmon resonance imaging.
To demonstrate the utility of this assay, the investigators used it to detect three specific microRNAs in total RNA samples from mouse liver. The assay was able to detect microRNA concentrations as low as 20 femtomolar. The investigators are now creating a larger array capable of profiling all microRNAs in biological samples.