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Nanomedicine, where nanotechnology and medicine intersect, is a vastly growing field as researchers are finding more and more nanomaterials and functionalized nanomaterials (typically with organic molecules) that are biocompatible with the body.
Within this field, there are a large number of application areas, one of which is nanoparticle-based therapies that can destroy cancerous tumors. Out of all the different cancer treatments, the brain is perhaps one of the most challenging, but researchers are now finding nanotechnology-based therapies that can be used to treat brain tumors.
Because of the sensitive nature of the brain compared to other organs, treating brain tumors is a tricky task, and patients have one of the worst rates of survival among cancer patients. In many cases, patients are only expected to live up to 14 months after the initial diagnosis.
One of the main reasons why brain cancer patients have a poor prognosis is because the traditional chemotherapy treatments used to destroy cancers struggle to pass through the blood-brain barrier, meaning that they do not reach the tumor in a sufficient concentration to be effective (and in many cases, not at all).
This also introduces secondary issues in that the chemotherapy drugs then circulate the body, and these harsh drugs can cause damage to the rest of the body if they cannot target the intended tumor. One of the main solutions in recent years has been to use nanoparticles, as there has been some success with getting nanoparticles across the blood-brain barrier. This has meant that nanoparticles, as nanocarriers, have now become a more effective treatment for brain tumors than many traditional chemotherapy treatments.
Academic Developments in Nanoparticle Delivery
There have been a number of ways to attempt to deliver nanoparticles to the brain. For example, in 2018, researchers from Imperial College London managed to functionalize gold nanoparticles with DNA on the surface, and ultrasonic waves (low energy waves) were used to open the blood-brain barrier so that the nanoparticles could pass through. This was achieved by creating acoustic microbubbles that vibrated the blood, causing the blood-brain barrier to open temporarily.
While this research was more concerned with finding ways of opening the blood-brain barrier than therapies per se, the ability to open the blood-brain barrier is important, as it is one of the key barriers to developing new therapies. The functionalized nanoparticles used in this research could be used to transport therapeutic payloads that can destroy brain tumors.
Research in the area is about finding the balance between biocompatibility and active properties, and for nanoparticles, these properties are often related to how the nanoparticles are functionalized on their surface.
Researchers from the UK and Singapore looked at different surfactants that could be added to the surface of nanoparticles and found that those with polyethylene glycol were up taken more easily across the blood-brain barrier than other surfactant molecules.
Again, finding more ways to cross the blood-brain barrier is an important piece of the puzzle for academic research, as there are known payloads that can be carried by nanoparticles to brain tumors, and getting them there has been the issue. Work of this manner is important as it finds ways to pass through the blood-brain barrier without the need for an external stimulus to be applied.One of the most recent pieces of research was carried out in China in 2020. The researchers functionalized quantum dots with multiple paired α-carboxyl and amino groups so that the nanoparticle mimicked the structure of a large amino acid.
This meant that the nanoparticle was recognized by a receptor molecule known as LAT 1, which is present on both tumors and the blood-brain barrier, but not on most healthy organs. This gave the quantum dot nanoparticles the ability to penetrate the blood-brain barrier without an external stimulus (as they give off the impression that they are nutrients) and attach to the tumor.
The clinical application of these specific molecules is a long way off yet, but the research has shown that future treatments might have more success if they design the nanoparticles to target the LAT 1 receptors found on the blood-brain barrier.
Commercial Developments in Treating Brain Tumors with Nanoparticles
It is not just the academic world where nanoparticles are being used to treat brain tumors; they are available commercially and are being used to treat patients with brain tumors. Magforce is a company based in Germany that uses a ferrofluid composed of superparamagnetic iron oxide nanoparticles to kill cancer cells.
Unlike many other nanoparticle cancer treatments, the iron oxide nanoparticles do not act as nanocarriers. Instead, they generate localized heat, which kills the cancer cells. There have been a number of academic developments that work in a similar manner, but Magforce is one of the first companies to produce and use them commercially.
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This treatment can be used for a range of tumors. It is not specific to brain tumors, but there have been results in using these nanoparticles to tackle brain tumors in a clinical setting.
The way this treatment works is that the magnetic nanoparticles localize near the tumor and are then exposed to an applied magnetic field. The magnetic field changes the polarity of the nanoparticles by up to 100,000 times per second, which generates localized heat. This heat is used to kill the cancerous cells and, over time, the tumor.
Future Outlook for Treating Brain Tumors
The use of nanoparticles offers many more possibilities than conventional chemotherapy treatments for treating brain tumors. The future of using nanotechnology to combat brain tumors looks promising, as there are now both academic and commercial developments being made that will hopefully ensure that people with brain tumors have a better chance of survival.
The research into treating brain tumors is still relatively novel, so it is likely that more effective treatments will emerge that will bring the survival rates up for brain cancer patients.
References and Further Reading
Lewis, B. (2018) Improving our understanding of a new method to deliver drugs to the brain. [Online] Imperial College London. Available at: http://www.imperial.ac.uk/news/187329/improving-understanding-method-deliver-drugs-brain/ (Accessed on 6 May 2020).
Nanowerk (2020) Nanoparticles offer large potential for brain cancer treatment. [Online] Available at: https://www.nanowerk.com/nanotechnology-news2/newsid=54906.php (Accessed on 6 May 2020).
Magforce. The NanoTherm® therapy.
Alexiou C. et al. (2019) Functionalized Superparamagnetic Iron Oxide Nanoparticles (SPIONs) as Platform for the Targeted Multimodal Tumor Therapy. Frontiers in Oncology, DOI: 10.3389/fonc.2019.00059
Wang C-W. et al. (2019) Development of Nanoparticles for Drug Delivery to Brain Tumor: The Effect of Surface Materials on Penetration Into Brain Tissue. Journal of Pharmaeutical Sciences, DOI: 10.1016/j.xphs.2018.12.002
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