Quantum dots applied to lung cancer cells (right) successfully destroyed up to 80 percent of them.Quantum dots applied to lung cancer cells (right) successfully destroyed up to 80 percent of them.New research shows that nanoparticles derived from tea leaves inhibit the growth of lung cancer cells, destroying up to 80 percent of them. The discovery came as a surprise for a team testing a new, alternative method of producing quantum dots — a nanoparticle type that has shown promise for applications ranging from solar cells to tumor imaging and cancer treatment.

Because they are so small (less than 10 nanometers), quantum dots are able to penetrate the nanopores of cancer cells themselves. “The dots actively inhibited the growth of the lung cancer cells,” said Dr. Sudhagar Pitchaimuthu of Swansea University, lead researcher on the project. “We hadn't been expecting this.”

Lung cancer survival rates are generally lower than for other cancers. According to Cancer Research, the five-year survival rate for lung cancer is less than 10 percent.

Chemical production of quantum dots is complicated and expensive, and also has toxic side effects. The new research leverages tea leaf extract as a non-toxic, plant-based production method. Mixing the extract with cadmium sulphate (CdSO4) and sodium sulphide (Na2S) and allowing the solution to incubate causes quantum dots to form.

The research also confirmed a previous study on using tea leaves as a simpler, cheaper and less toxic method of quantum dot production, compared to using chemicals. Tea leaves, for their part, contain a wide variety of compounds, including polyphenols, amino acids, vitamins and antioxidants.

According to Pitchaimuthu, next steps for research include scaling up on the operation in the hopes of creating a “quantum dot factory” that will allow a fuller exploration of quantum dot uses. "We want to investigate the role of tea leaf extract in cancer cell imaging, and the interface between quantum dots and the cancer cell," he said. Another potential application, he noted, is in anti-microbial paint used in operating theatres, or in sun creams.

The research appears in the April 2018 edition of Applied Nano Materials.