Synthesizing Graphene Quantum Dots into Bioimaging Probes

Researchers are exploiting the nontoxic, fluorescent capabilities of quantum dots to enhance medical imaging.

Kristopher Sturgis

A group of researchers from San Jose State University (SJSU) believe graphene quantum dots could be the next big step in bioimaging technology.

While working on their masters in biomedical engineering, Aneshkumar Tilwani and Hildegarde Bell teamed up to explore the potentials of small crystals of graphene with a diameter of less than 50 nanometers--something known as graphene quantum dots (GQD). Bell initially found a few articles detailing the synthesis of silicon quantum dots, and theorized that through a similar synthesis process, the same could be done with graphene. Upon their first batch of synthesized GQDs, they noticed a distinct trait in the tiny crystals.

"Our first initial batch exhibited fluorescence under a UV lamp," Bell said. "The results of PL testing showed luminescence using excitation in a range of wavelengths."

More specifically the dots showcased a transition of photoluminescence from blue to green as a result of this excitation in the UV and visible wavelength ranges. They also found that GQDs are soluble in a variety of organic liquids including water, and unlike other semiconductor-derived quantum dots, GQDs have shown to be nontoxic in cultured cells and in animal studies. A fact that makes them suited for applications in bioimaging and biosensing technologies.

"This could potentially manifest into an injectable dye as a contrast agent to image blood vessels without the need for ionizing radiation to penetrate through tissue," Tilwani says. "It could be used in localized imaging devices, such as mammography, and could be another tool in medical imaging."

Given all of its potentials, keeping up with the latest in graphene advances is becoming almost a weekly endeavor. Just a few weeks ago, researchers from the University of Illinois at Urbana-Champaign discovered a new method to forming 3-D shapes from 2-D sheets of graphene, an approach that they hope will lead to new integrated systems of microelectromechanical systems with hybrid devices and flexible electronics.

While graphene's superior conductivity traits are well known, some of the photoluminescent properties that Tilwani and Bell discovered in the GQDs could lead to advances in bioimaging technologies, including the possibility of tumor imaging and cancer detection.

"We believe the technology can be enhanced by targeting the GQDs," Tilwani says. "For example, targeted imaging can have applications in cancer detection, and the GQDs could even be modified into a drug for photodynamic therapy which can be used to kill cancer cells.

The team--which also includes Jose Alvarez, a biomedical engineering student at SJSU, and Folarin Eorgbogbo, PhD and assistant professor at SJSU--believes the technology could also make its way into wearables, as it can be used to create biocompatible electric circuits that can enhance electronics and more.

"We see this project developing into some type of biosensor application that uses GQDs in the circuitry," Tilwani said. Although we think our technology could be used to potentially image tumor cells as well, there is a lot of work to be done our end to achieve these feats."

While many challenges still lie ahead, the group remains determined to explore every possible avenue that the technology unlocks, in an effort to maximize the efficiency and effectiveness of GQDs. They even hope to identify several wearable device technologies that GQDs could be easily adapted into, as they try to evolve the technology into as many forms as possible to enhance the world around us.

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