Gold nanorods identify metastatic tumor cells

Using a series of gold nanorods, each with its own characteristic optical signature, researchers at Purdue University have developed a method for rapidly assaying the cellular composition of breast tumors.

This assay technique could provide oncologists with a more accurate assessment of the metastatic potential of an individual's cancer.

One important finding to come out of cancer research laboratories over the past few years is that tumors comprise many types of cells and that only a small proportion—the cancer stem cells—are responsible for the unlimited growth potential of a malignant tumor. Based on these findings, researchers have since identified a variety of cell surface markers on different types of breast cancer cells that may be predictive of a tumor's ability to metastasize.

Reporting its work in the journal Nano Letters, a team of investigators led by Joseph Irudayaraj, Ph.D., developed a new technique for making biocompatible gold nanorods of various sizes to which they could then attach antibodies. Gold nanorods interact with light to produce plasmons, a wave-like motion of electrons on the surface of the nanorods. Depending on the ratio of a nanorod's length to its diameter, these plasmons trigger light emission at a specific frequency that is easily detected using surface plasmon resonance spectroscopy.

To each nanorod of a given length and diameter, the researchers attached an antibody that recognizes one specific cancer cell surface marker. The researchers also prepared a gold nanorod-antibody construct that recognizes a biomarker found on all cell surfaces to serve as an internal reference control that would enable them to calculate relative amounts of the various tumor markers on a given cancer cell.

Using a panel of three different antibody-labeled gold nanorods, the investigators were able to characterize breast tumors according to their cellular composition and correlate their findings to the metastatic potential of each given cell type. These results were validated using flow cytometry, the standard, but laborious, technique used to classify cells according to surface markers. The researchers note that they could have monitored as many as 15 different antibody-nanorod constructs simultaneously.

This work is detailed in the paper "Identity profiling of cell surface markers by multiplex gold nanorod probes." Investigators from Indiana University School of Medicine and the Walther Cancer Institute also participated in this study. An abstract of this paper is available through PubMed. View abstract.