Statistics indicate that complete removal, or resection, of a tumor is the single most important predictor of patient survival for those with solid tumors.
So, unsurprisingly, the first thing most patients want to know after surgery is whether the surgeon got everything. A new hand-held device called the SpectroPen could help surgeons provide a more definite and desirable answer by allowing them to see the edges of tumors in human patients in real time during surgery.
The SpectroPen combines a near-infrared laser and a detector to observe fluorescent dyes as well as scattered light from tiny gold particles that have been designed to stick to tumor cells. These particles consist of polymer-coated gold, coupled to a reporter dye and an antibody that sticks to the molecules on the outsides of the tumor cells. Through an effect called surface-enhanced Raman scattering, the gold in the particle greatly amplifies the signal from the reporter dye, allowing the researchers to detect tumors smaller than one millimeter grafted into rodents. The SpectroPen is connected by a fiber optic cable to a spectrometer that can record the fluorescence and Raman signals.
The researchers used the SpectroPen to detect the dye indocyanine green, an FDA approved dye that had been infused intravenously into mice with implanted human breast cancer cells. Because of the leaky blood vessels and membranes surrounding tumors, the dye accumulates at a higher rate in tumor cells resulting in the SpectroPen’s signal from the tumor being ten times higher than from normal tissue.
As the cancer cells implanted in the mice had a gene from fireflies added, the tumors glowed after the mice were given a solution of “luciferin” – a light-emitting biological pigment that causes bioluminescence. This allowed the scientists to check that the outline of the tumor seen through the SpectroPen matched the glow.