Multifunctional Properties of Gold Nanoparticles and Their Role as Radiosensitisers
Gold nanoparticles (AuNPs) have gained considerable attention in cancer research due to their exceptional physical and chemical properties. Among their various applications, their role as radiosensitisers—agents that increase the sensitivity of cancer cells to radiation—stands out as particularly encouraging. This review discusses the multifunctional properties of AuNPs and their potential to revolutionise radiation therapy by enhancing its precision and effectiveness.
Properties of Gold Nanoparticles
Optical Features
One of the most striking features of gold nanoparticles is their ability to interact with light through a phenomenon called localised surface plasmon resonance (LSPR). This property enables AuNPs to absorb and scatter light efficiently, making them ideal for diagnostic imaging and therapeutic purposes (Huang et al., 2016). These optical characteristics also make AuNPs valuable for tracking their accumulation within tumours.
Biocompatibility and Stability
Gold is a biologically inert material, meaning it does not react adversely with the human body. This makes AuNPs safe for biomedical applications. Additionally, the surface of gold nanoparticles can be easily modified with molecules such as antibodies or peptides, improving their specificity for targeting cancer cells (Kim et al., 2017).
High Atomic Number
Gold’s high atomic number (Z = 79) makes it particularly effective at interacting with X-rays. When exposed to radiation, gold nanoparticles amplify the local energy deposition within tumour tissues, which is critical for their role as radiosensitisers (Hainfeld et al., 2004).
Functionalisation Potential
The surface of AuNPs can be engineered to carry drugs, imaging agents, or ligands that target specific cancer markers. This multifunctionality allows them to integrate seamlessly into various therapeutic strategies, including combined radiation and chemotherapy (Huang et al., 2016).
Gold Nanoparticles as Radiosensitisers
Mechanism of Action
Gold nanoparticles enhance the effects of ionising radiation by generating electrons and reactive oxygen species (ROS) when exposed to X-rays. These ROS and electrons cause extensive DNA damage, leading to increased tumour cell death. By amplifying the local radiation dose, AuNPs make radiation therapy more effective (Hainfeld et al., 2004).
Targeting Tumours with Precision
Through surface modifications, AuNPs can be functionalised with ligands like antibodies or peptides that bind specifically to cancer cells. This ensures that the nanoparticles concentrate in tumour tissues while sparing healthy cells. The enhanced permeability and retention (EPR) effect, where nanoparticles naturally accumulate in tumour tissues due to their leaky blood vessels, further supports their targeting capability (Kim et al., 2017).
Advantages of Gold Nanoparticles in Radiation Therapy
Boosting Radiation Efficacy
Gold nanoparticles amplify the energy deposition from ionising radiation, increasing tumour cell destruction without requiring higher radiation doses. This reduces side effects on healthy tissues, making the treatment safer and more precise (Hainfeld et al., 2004).
Multifunctional Cancer Therapy
AuNPs are not limited to radiosensitisation. They can also be combined with other therapies, such as chemotherapy or photothermal therapy. For example, functionalised AuNPs can carry anticancer drugs directly to the tumour site and release them upon activation by light or radiation, creating a synergistic therapeutic effect (Huang et al., 2016).
Challenges and the Path Ahead
Biodistribution and Safety
Although gold is generally considered safe, ensuring that AuNPs are efficiently cleared from the body remains a key challenge. Prolonged retention could lead to toxicity. Researchers are working on biodegradable nanoparticle designs to address this issue (Kim et al., 2017).
Penetration Depth of Radiation
While AuNPs are highly effective at amplifying radiation effects, their success depends on the depth of the tumour. Surface-level or moderately deep tumours are more accessible, but treating deeply located tumours remains a challenge. Techniques such as advanced radiation delivery systems are being explored to overcome this limitation (Hainfeld et al., 2004).
Cost and Scalability
Producing AuNPs at a scale and cost suitable for widespread clinical use is another obstacle. Current research focuses on optimising manufacturing processes to make AuNP-based therapies more affordable without compromising their quality or effectiveness (Huang et al., 2016).
Conclusion
Gold nanoparticles have great potential to improve cancer treatments, especially in making radiation therapy more effective. They help target tumours more precisely, reduce damage to healthy tissues, and can also be used in imaging and drug delivery. These features make them a valuable tool for treating cancer in a more focused and less harmful way.
Despite this promise, there are challenges, such as ensuring they are safe for long-term use, improving their ability to treat deeper tumours, and reducing production costs. Continued research is working to solve these issues. With further development, gold nanoparticles could become a reliable and widely used option in cancer therapy, offering better results and fewer side effects for patients.
References
Hainfeld, J. F., Slatkin, D. N., & Smilowitz, H. M. (2004) ‘The use of gold nanoparticles to enhance radiotherapy in mice’, Physics in Medicine & Biology, 49(18), pp. N309–N315.
Huang, X., Jain, P. K., El-Sayed, I. H., & El-Sayed, M. A. (2016) ‘Gold nanoparticles: Interesting optical properties and recent applications in cancer diagnostics and therapy’, Journal of Nanomaterials, 2016, Article ID 5497136. Available at: https://doi.org/10.1155/2016/5497136.
Kim, J., Chhour, P., Hsu, J., Litt, H. I., Ferrari, V. A., Popovtzer, R., & Cormode, D. P. (2017) ‘Gold nanoparticles in imaging and therapy’, Quantitative Imaging in Medicine and Surgery, 7(3), pp. 297–307. Available at: https://doi.org/10.21037/qims.2017.06.03.