The Next Steps for Graphene Quantum Dots in Cancer Diagnostics

A paper available as a pre-proof in the journal Materials Today Communications has reviewed different synthesis methods of graphene quantum dots (GQDs) as well as their optical properties and applications against cancer.

The Next Steps for Graphene Quantum Dots in Cancer Diagnostics

Study: Graphene quantum dots: synthesis, optical properties and navigational applications against cancer. Image Credit: CI Photos/Shutterstock.com

Significance of Graphene Quantum Dots

GQDs are referred to as zero-dimensional carbon-based nanomaterials that have gained wide attention for theranostic applications owing to their chemical inertness, high hydrophilicity, non-toxicity, and ultra-small size. Additionally, GQDs offer high luminescence stability, imaging depth, and signal-to-noise ratio, and their optoelectronic properties can be modulated for edge group functionalization and heteroatom doping.

GQD Synthesis Methods

Bottom-up and top-down methods are the two main approaches used for the synthesis of GQDs. The selection of a specific synthesis method depends on the process yield, production scale, and product properties.

Top-Down Approaches

The top-down synthesis approach involves the exfoliation of carbon materials such as graphite into single- or multi-layered graphene sheets and then breaking up the sheets in both dimensions through microwave, electrochemical scissoring, solvothermal, and oxidation treatments to obtain GQDs with intended particle properties. The π-conjugation in the synthesized GQDs is restored through an in situ re-aromatization process.

Oxidation Treatment

In oxidation treatment, the breakup of carbon-carbon (C-C) bonds in carbon materials is achieved using strong oxidizing agents such as sulfuric acid (H2SO4) under aggressive experimental conditions. The method exploits the multiplicity of structural defects that are formed at the basal plane of the graphene sheets during exfoliation.

Solvothermal Treatment

Solvothermal treatment primarily involves solvent-assisted breakup of carbon materials under high pressure and temperature. For biomedical applications, water is used as the green dispersion medium, and the process is referred to as hydrothermal treatment.

In hydrothermal treatment, pre-oxidized graphene sheets are exposed to overheated steam under pressure, which restores the carbon lattice aromatic structures by minimizing the defects in surface oxygen. 

Electrochemical Scissoring

In electrochemical scissoring, GQDs are obtained by cleaving the graphite electrode under high redox voltage in a normal electrochemical set-up. The electrodes typically used in this method include carbon paste electrodes synthesized by packing method and petroleum coke–based electrodes made by calcination.

Microwave Irradiation Treatment

The method is an attractive option for GQD synthesis owing to its uniform dielectric heating ability. A microwave with an atmospheric reflux device is employed to perform the method at an ultra-fast speed without adversely impacting the product characteristics and yield.

Bottom-up Approaches

Thermodynamically driven GQD preparation processes are considered more suitable than the defect-mediated fragmentation of graphene sheets. The bottom-up QD fabrication approach can address the limitations of top-down strategy and help in obtaining GQDs with specific structures and morphology through chemical reactions.

The approach employs eco-friendly and low-cost small organic molecules such as glucose for the GQD synthesis that is performed through the step-wise reduction of pre-synthesized polycyclic aromatic hydrocarbons or condensation of solubilized precursors.

Carbonization

Carbonization can be performed through hydrothermal treatment, microwave exposure, and pyrolysis under reduced pressure. GQDs were successfully synthesized through the pyrolysis of synthetic and natural molecules.

Cage-Opening

In this method, fullerenes, which are mainly zero-dimensional caged structures composed of 70 (C70), 60 (C60), or more carbon atoms, are packed into fused pentagons and hexagons to synthesize a diverse range of graphene materials. Although the materials remain stable at room temperature, they undergo fragmentation due to annealing at temperatures above 700 °C. 

Green Synthesis Methods

In green synthesis, the input materials are obtained from organic materials such as vegetable wastes, which renders the method less hazardous to the environment and cost-effective.

The graphene sheets are synthesized following bottom-up approaches and then the synthesized sheets are fragmented to GQDs using top-down approaches.

Optical Properties of GQDs

In GQDs, the optical transition can cover the near-infrared (NIR) and ultraviolet (UV)-Visible regions of the solar spectrum, and their absorption spectrum displays a weak and a strong peak due to n–π* and π–π* transitions, respectively. The photoluminescence (PL) varies based on the de-localized π electron density at the surface defects and basal plane.

Additionally, the optical properties of GQDs can be improved by doping them with heteroatoms such as sulfur and nitrogen.

An advanced photothermal-photodynamic platform developed by combining the singlet oxygen generation ability of porphyrin derivatives and optical properties of GQDs can translocate to cytosolic targets in presence of targeting moieties, leading to improved therapeutic outcomes.

Applications of GQDs Against Cancer

GQDs are used in several applications against cancer, ranging from the identification of biomolecular changes in cells to tumorigenesis and tissue imaging. The detection of abnormally dividing cells in a pre-invasive state can potentially improve the survival rate of cancer patients. Multimodal imaging platforms can be developed by combining metal nanoparticles with GQDs.

Targeted imaging of tumor mass is necessary for timely diagnosis of the condition. GQDs employed in conjunction with magnetic resonance imaging (MRI) can provide a high spatial resolution of the target tumor mass. Additionally, cancer-specific biomarkers can be detected rapidly in a cost-efficient manner using GQDs as electro-chemiluminescence (ECL) or chemiluminescence (CL) reagent. Moreover, studies demonstrated that GQDs rapidly excrete from the host body after they were administered through subcutaneous, intramuscular, or intravenous injections.

Overall, this study reviewed different GQD synthesis methods, optical properties, as well as applications in the context of cancer diagnosis. However, more research is required to further assess the GQD synthesis methods in terms of consistency and throughput.

Reference

Tiwari, S., Bahadur, P., Shukla, R. et al.(2022) Graphene quantum dots: synthesis, optical properties and navigational applications against cancer. Materials Today Communications. https://www.sciencedirect.com/science/article/pii/S2352492822002306?via%3Dihub

Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.

Samudrapom Dam

Written by

Samudrapom Dam

Samudrapom Dam is a freelance scientific and business writer based in Kolkata, India. He has been writing articles related to business and scientific topics for more than one and a half years. He has extensive experience in writing about advanced technologies, information technology, machinery, metals and metal products, clean technologies, finance and banking, automotive, household products, and the aerospace industry. He is passionate about the latest developments in advanced technologies, the ways these developments can be implemented in a real-world situation, and how these developments can positively impact common people.

Citations

Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Dam, Samudrapom. (2022, March 10). The Next Steps for Graphene Quantum Dots in Cancer Diagnostics. AZoNano. Retrieved on July 02, 2022 from https://www.azonano.com/news.aspx?newsID=38803.

  • MLA

    Dam, Samudrapom. "The Next Steps for Graphene Quantum Dots in Cancer Diagnostics". AZoNano. 02 July 2022. <https://www.azonano.com/news.aspx?newsID=38803>.

  • Chicago

    Dam, Samudrapom. "The Next Steps for Graphene Quantum Dots in Cancer Diagnostics". AZoNano. https://www.azonano.com/news.aspx?newsID=38803. (accessed July 02, 2022).

  • Harvard

    Dam, Samudrapom. 2022. The Next Steps for Graphene Quantum Dots in Cancer Diagnostics. AZoNano, viewed 02 July 2022, https://www.azonano.com/news.aspx?newsID=38803.

Tell Us What You Think

Do you have a review, update or anything you would like to add to this news story?

Leave your feedback
Your comment type
Submit