Graphene Quantum Dots Developed As Metal-Free Nanozymes Show Potential for Chemodynamic Cancer Therapy

Nanotechnology is a new scientific technique that provides novel therapies for treating malignant diseases.

(Photo: Wikimedia Commons/ U.S. Department of Energy)

Breakthrough in Cancer Treatment

Nanozymes, or nanomaterial-based artificial enzymes, have demonstrated promising potential as therapeutic agents for treating cancer. However, a crucial challenge in their application is the potential for off-target side effects due to metal toxicity.

At the Chinese Academy of Sciences, experts used graphene quantum dots (GQDs) to develop metal-free nanozymes for chemodynamic therapy (CDT). The result of their study is discussed in "Graphene quantum dots as metal-free nanozymes for chemodynamic therapy of cancer."

Graphene quantum dots represent an innovative and cost-effective means of addressing the toxicity of metal-based enzymes in tumor hemodynamic therapy. Made from red blood cell membranes, the obtained GQDs effectively treat tumors with few side effects. They also have the advantages of being metal-free and demonstrating excellent peroxidase-like biocatalysis.

However, these graphene sheet fragments have limited catalytic activity, hindering their clinical application, especially under challenging catalytic conditions. To enhance the performance of GQD-based nanocatalytic adjuvant, Professor Wang Hui from the Hefei Institutes of Physical Science (HFIPS) led the research team in rationally designing graphene quantum dots using a diatomic doping strategy.

Nitrogen and phosphorus introduced into graphene quantum dots have a synergistic electron effect that can generate highly localized states near the Fermi level. This enables efficient enzymatic activity compared to single heteroatom doping.

After obtaining graphene quantum dots from erythrocyte membranes, the researchers discovered impressive peroxidase-mimicking activity. They concluded that graphene quantum dots are highly effective in inducing apoptosis and cancer cell ferroptosis in vitro. The tumors are also selectively targeted with an inhibition rate as high as 77.71% for intravenous injection and 93.22% for intratumoral injection.

The researchers are confident that developing a drug-free, target-specific, and biologically benign nanozyme can pave the way for potent biocatalysis for safe cancer treatment.

Potential of Graphene Quantum Dots in Medicine

Graphene quantum dots refer to particles made of a few layers of graphene smaller than 100 nanometers. These zero-dimensional nanomaterials have gained wide attention for theranostic applications.

As graphene sheet fragments, GQDs demonstrate exceptional properties like stable photoluminescence, low toxicity, chemical stability, and pronounced quantum confinement effect. Additionally, they offer signal-to-noise ratio, high hydrophilicity, and imaging depth. Because of these characteristics, graphene quantum dots are considered a new material for biological, optoelectronics, and environmental applications.

Graphene quantum dots demonstrate potential uses in optoelectronic, biological, and energy-related fields. Recently, experts have found that graphene quantum dots are also beneficial for photodynamic therapy. This is made possible by generating singlet oxygen upon irradiation.

As a novel class of fluorescent carbon materials, they were found to have several applications against cancer, ranging from identifying biomolecular changes in cells to tissue imaging and tumorigenesis. Detecting abnormally dividing cells before they become invasive can improve cancer patients' survival rates. Additionally, graphene quantum dots can be combined with metal nanoparticles to develop multimodal imaging platforms.