Few people truly appreciate the stones it takes to be a neurosurgeon and take a knife to a person’s brain. Removing cancerous tissue and maximizing the preservation of healthy tissue is no simple task, but Carnegie Mellon researchers hope their glowing nanoparticles will help surgeons know what to cut and what to leave behind.
Researchers at Carnegie Mellon University (CMU), in Pittsburgh, are using fluorescent nanoparticles to image tumor tissue during biopsies and surgeries. The imaging technique, which is being tested in rodents, could be particularly useful for precisely spotting tumors during surgeries to remove glioblastomas, one of the most common and aggressive forms of brain cancer. On average, patients survive less than a year after their diagnosis with this deadly form of brain cancer, in part because of the difficulty of surgically removing the entire tumor.
Led by CMU chemist Marcel Bruchez and Steven Toms, director of neurosurgery at the Geisinger Clinic, in Danville, PA, the researchers took crisp fluorescent images of brain tumors, called gliomas, in rats. The rats had been injected with nanoparticles that emit infrared light when they are excited by visible light. The infrared rays made by the nanoparticles can be picked up by a small camera and viewed by surgeons. These quantum dots have a core made of cadmium and telluride, surrounded by a zinc-sulfide shell, which is in turn surrounded by a protective polymer coating.
“This particular type of tumor is poorly distinguishable,” says Bruchez. And when removing brain tumors, surgeons can’t cut wide margins, or patients might lose brain function.
Bruchez wants to build an imaging system that’s compatible with standard operating procedures. Outfitting an operating room for infrared imaging of tumors would involve adding an infrared digital camera and installing filters on the lights to eliminate ambient infrared light, ensuring that the only infrared light in the room comes from quantum dots. The quantum dots can be tuned to emit visible light, which would eliminate the need for the imaging system, but doctors would have to turn off the lights to see the glow from tumors, then turn them back on and readjust their eyes to continue with surgery.
Bruchez and Toms are also developing biopsy needles with optical imaging systems. Brain-tumor biopsies are normally time consuming and hit or miss. “You go where you believe the tumor to be, take out a sample, send it to the pathology lab, and wait in the operating room for the results,” says Bruchez. If the surgeons missed the tumor, they have to take another sample and wait for the results again. If a patient were first injected with tumor-seeking quantum dots that could be detected by the biopsy needle, the process might be that much easier.