When illuminated, a single gold nanoparticle appears green (top left), while a pair of gold nanoparticles bound to an mRNA splice variant, or dimer, appears reddish (top right). The graph shows how monomers and dimers scatter light differently.
Purdue researchers developed a new method for detecting and quantifying cancer levels in a living cell, focusing on breast cancer gene-segment quantification. Current cancer-detecting methods involve samples of hundreds, if not thousands, of cells that do not offer details of how genes tied to cancer are expressed in a single-cell.
Professor of Agricultural and Biological Engineering, Joseph Irudayaraj, and his then research assistant, Kyuwan Lee, discovered the procedure, which uses gold nanoparticles with tails of synthetic DNA complimentary to BRCA1 mRNA splice variants. The variants are fragments of genetic material removed from mRNA when formed.
The number of BRCA1 mRNA splice variants in a cell can change current methods because it indicates whether the gene is under-expressed—indicating breast cancer. BRCA1 (BRCA1 is a tumor suppressor gene that can form a cancerous cell) indicates the presence and stage of breast cancer, while splice variants can determine what will happen to a cell and how proteins are expressed. Errors in splicing have been linked to disease.
In the new procedure, the gold nanoparticles attach to either end of mRNA splice variants to form structures known as “dimers” after being injected into the cell. Dimers look unique in the presence of light, so the number of dimers can be measured by illuminating the cell with light. The number of dimers equals the number of BRCA1 mRNA variants in a cell, thus detecting potential cancerous cells.
Spectroscopy and colorimetric images were used to quantify the dimers. Spectroscopy measures the way light disperses when it encounters an object. Colorimetric imaging, on the other hand, simply causes a reddish dot to appear on dimers and a green dot to appear on gold particles. The researchers would like to speed up the entire process, which takes about 30 minutes, so that it can be used for tissue biopsies.
Numerous potential benefits of the procedure include the ability to detect and gauge how aggressive cancer is in a single cell, while at the same time creating an individualized treatment. It also could increase the understanding of cell biology, eventually leading to genetic profiling and diagnosis based on a single cell. In addition, it offers the possibility of gaining greater insight into cellular complexes, pharmacogenomics, genetic diagnosis, and gene therapies. The research is published in the April 20 edition of Nature Nanotechnology.