Johns Hopkins engineers have created a new optical tool that could improve cancer imaging. Their approach, called SPECTRA, uses tiny nanoprobes that light up when they attach to aggressive cancer cells, helping clinicians distinguish between localized cancers and those that are metastatic.
“Our findings show that SPECTRA has huge potential for cancer detection and imaging,” says team leader Ishan Barman, professor of mechanical engineering. “We’re giving clinicians a more powerful tool that can find cancer cells earlier and more precisely than ever before.”
The research appeared in Advanced Functional Materials.
SPECTRA leverages a first-of-its-kind combination: Raman spectroscopy—which uses the scattering of laser light to provide detailed information about molecular vibrations—and DNA origami, which involves folding DNA into specific shapes. The researchers used the folded DNA as a scaffold to create precisely arranged plasmonic nanoparticles: Raman reporters (molecules that produce a strong signal when analyzed using Raman spectroscopy) and cancer-targeting DNA sequences. Then they tested these nanoprobes on cancer cells.
They found that SPECTRA effectively and consistently bound to metastatic prostate cancer cells and even differentiated between those and nonmetastatic cells— unlike CT or MRI scans, which can indicate the presence of a tumor but not the specific molecular signatures that can alert physicians to current or impending metastasis.
The researchers also identified a Raman reporter that results in an active and distinct signal in a range that made it stand out against the background of normal tissue, helping clinicians more precisely locate disease.
“It’s a smart design that gives high enhancement to the Raman signal, and it’s uniform,” says team member Swati Tanwar, a mechanical engineering postdoctoral fellow. “It can distinguish aggressive cancer cells from nonaggressive based on the intensity of the signal. In a tumor, if 10% of the cells are aggressive and 90% are nonaggressive, the 10% will light up and give a very high signal.”
Tanwar explains that each strand of DNA in the origami scaffold has a unique sequence and occupies a specific position in the folded origami nanostructure. This meticulous arrangement facilitated the creation of the multifunctional SPECTRA nanoprobe.
“Raman spectroscopy is a molecular fingerprinting tool,” adds team member Lintong Wu, a mechanical engineering PhD student. “Molecules can look similar at a distance, but using Raman spectroscopy, [we can] show different peaks and signals throughout the entire spectrum.”