Ultra-Sensitive Detection of Breast Cancer Biomarkers Using Time-Resolved FRET and Quantum Dots

Breast cancer is defined as a malignant neoplasm that occurs at or around the breast issue area. This disease affected 25,000 women last year in Canada and claimed the lives of 5,000 women. These numbers represent 26% and 14% of all new breast cancer and deaths, respectively, for Canadian women in 2015. These numbers do not tell us the amount of lives that were affected due to the disease, which can go into the hundred thousands. Here we develop a multiplexed microfluidics chip that accurately detects miR-195 and let-7a in human serum samples. MicroRNAs (miRNA) are small non-coding messenger RNA that are derived from messenger RNA. These small robust RNAs are looked at as precursors to many different diseases including breast cancer. Both miR-195 and let-7a have been shown to increases in concentration in human serum samples during cancer and decrease in concentration within tumor cells during cancer. To effectively measure miRNA concentration in blood with minimally invasive techniques, the developed microfluidics chip detects the miRNA levels from human blood using time resolved-förster resonance energy transfer. The detection mechanism uses a DNA zipper that binds the miRNA with an 8 base pair (bp) DNA supporter sequence and a complementary DNA sequence. When the supporter, complementary and miRNA sequences bind together a terbium-cryptate molecule excites a quantum-dot (710 nm for let-7a and 655 nm for miR-195) and the fluorescence is measured. Detection limits of the miRNAs are 10 picomolar, with a dynamic range of 10 nM to 0.1 nM when measured with microfluidics chips.