Scientists have used a new method based on dissolution of gold nanoparticles to identify miRNAs involved in progression of breast cancer.
miRNAs and Breast Cancer
Breast cancer is among the most prevalent forms of cancer worldwide which affects more than 12% of female population. Early diagnosis of cancer could lead to more efficient treatment and prolonged patient survival. Dysregulated micro RNAs (miRNAs), including miR-155, play a key role in apoptosis, angiogenesis and metastasis of breast tumors. Over-expression of miR-155 can make cancer cells resistant to chemotherapeutic agents. Expression pattern of these miRNAs are being used as a tool to identify different forms of breast cancer.
miRNA detection method
Traditional miRNA detection methods including qRT-PCR, next-generation sequencing (NGS) and microarray have their own strengths and weaknesses. Thus, a faster and cheaper method that does not require special equipment could be very valuable. Today, gold nanoparticles (AuNPs)-based localized surface plasmon resonance (LSPR) as an optical sensor is being employed in various fields including disease diagnosis. This is due to its advantages such as sensitivity, simplicity, rapidity, being label-free, low-cost instrument and requirement of low sample volume. Among numerous metal NPs, AuNPs and silver NPs have a unique LSPR feature. When these nanoparticles receive the radiation, they absorb one part of the photon and scatter the other part. Optical spectroscopy is the simplest technique to detect the LSPR on metal nanoparticles. However, scientists from Tehran University of Medical Sciences have recently used this mechanism to detect miRNAs.
miRNA detection via gold nanoparticles
In order to detect miRNAs in cells, researchers used electron charging and discharging of Au cation via electron transfer from semiconductor CdTe QDs to AuNPs at 560 nm under UV light irradiation. They performed this step in the absence of miRNA. This procedure produced hot electrons on the plasmonic AuNPs which then attached to hydronium ion in water. Expression level of miR155 was analyzed by measuring LSPR bands.
Then, researchers added different concentrations of miR155 to the solution containing single strand DNA probe. Specific miRNAs, including miR-155, are hybridized to these single stranded DNAs and form heteroduplexes. After addition of QDs and AuNPs, scientists measured LSPR bands
The results showed that there was a difference between miR155 expression in HEK 293(normal cells) and MCF-7 (tumor cells) using this new method. Before AuNPs addition, QDs emission intensity was less in tumor cell lines compared to normal cell lines. After addition of AuNPs to the solution containing DNA/miR-155 duplex and QDs, the results indicated a difference in expression of miR-155 between normal and tumor cell lines. Moreover, these results were in agreement with qRT-PCR results.
This study provides a new valuable method to detect miRNAs expression level in different cells with high accuracy.