Remember a time when we studied about the photoelectric effect in a physics class, where half of the students used to doze off? It was a time in life when most of us didn’t pay attention to the nitty-gritty of physics, partly because some of us thought that most of the physics will have no application in the careers we wanted to pursue in the future. But in today’s world when the boundaries between the sciences have dwindled and wisps of each discipline have intermingled to give rise to new prospects, this thought has become an unintelligent way of thinking.
We have all heard about radiation therapy, a process that uses physics, working on the principles of biology to defeat human’s common enemy, cancer. Since the use of radiation in cancer therapy began in the late 19th century we can forthrightly say that we have come a long way. But there is a persisting obstacle in this technology. Radiation therapy that uses X-rays needs oxygen to produce reactive oxygen (responsible for damaging the cancer cell’s DNA). The center of most tumors do not have enough oxygen due to lack of angiogenesis which makes the tumors almost impossible to harm entirely simply by the use of X-rays.
To remedy this setback, scientists at Japan’s Kyoto University have researched on using the photoelectric effect to damage the DNA more directly than the current methods in use. This photoelectric effect employs the method of using X rays to remove electrons from the inner K shell of the atoms of elements with high Z (elements such as Gold, Iodine, Gadolinium, etc). The researchers Tamanoi, Kotaro Matsumoto, and colleagues, took inspiration from their previous quests of solving the same issue using gadolinium-loaded nanoparticles to target cancer cells, this time, created porous iodine-carrying organosilica nanoparticles(IPO).
Their technique uses the phenomenon of enhanced permeability and retention effect (EPR EFFECT) in cancer cells to target them preferentially. Iodine being cheaper and having the ability to release electrons at a lower energy level poses itself as a better and more sustainable nanoparticle than the nanoparticles that use gadolinium or other high Z elements. The study was conducted in vivo, using tumor spheroids, which are 3-D tumor masses. Usage of this tumor spheroid-based assay made the diffusion of nanomaterials and X-ray penetration more representative of the in-vivo conditions than typical cancer cell assays, therefore, making its results more accurate and viable.
The results of these experiments were promising as they suggested that the IPO's were successful in inducing apoptosis and causing dramatic destruction (as stated by the authors of the research paper) in the tumor spheroids. The study suggested that the IPO caused double-stranded DNA breaks upon the introduction of X-rays which in turn caused complete apoptosis (cell death) of the tumor spheroids within three days of incubation with IPO. The best results were seen when the spheroids were irradiated with 33.2 keV of monochromatic X-ray.
The researchers are currently contemplating a way to incorporate the IPO's directly into the DNA and hope to achieve a more substantial result by increasing their efficacy. They are also looking forward to testing these nanoparticles on Xenografts and mouse models to gain more clarity on their effects on cancerous tumors and their cytotoxicity.
SciTech Daily article:
Higashi, Y., Matsumoto, K., Saitoh, H. et al. Iodine containing porous organosilica nanoparticles trigger tumor spheroids destruction upon monochromatic X-ray irradiation: DNA breaks and K-edge energy X-ray. Sci Rep11, 14192 (2021).