Biomedical engineers are developing a hand-held device called a SpectroPen that could help surgeons see the edges of tumours in human patients in real time during surgery. Statistics indicate that complete removal, or resection, is the single most important predictor of patient survival for most solid tumours. This work has been reported in Analytical Chemistry (doi: 10.1021/ac102058k).
The SpectroPen can be used to detect fluorescent dyes, and also, by surface-enhanced Raman scattering (SERS), scattered light from minute gold particles. It is connected by a fibre optic cable to a spectrometer. NIR light is sent down one cable and scattered light or fluorescence returns down the other.
The particles consist of polymer-coated gold, coupled to a reporter dye and an antibody for the tumour cells. Through SERS, the gold in the particle greatly amplifies the signal from the reporter dye. The authors have been able to show that the particles can detect tumours smaller than 1 mm grafted into rodents.
"This technology could allow a surgeon to directly visualize where the tumours are, in real time. In addition, a post-surgery scan could check tumour margins," said Shuming Nie, of Georgia Tech and Emory University. "A major challenge is to completely remove the tumour as well as identify lymph nodes that may be involved."In the Analytical Chemistry paper, the researchers used the pen to detect the dye indocyanine green, infused intravenously into mice with implanted human breast cancer cells. The dye accumulates at a higher rate in tumour cells because of the leaky blood vessels and membranes surrounding tumours. The SpectroPen’s signal from the tumour is ten times higher than from normal tissue.