Radiation and gold nanoparticles working together for the image-guided radiotherapy

What is the image-guided radiotherapy (IGR)?

The combination of medical imaging and radiotherapy constitutes an important research field, for the group “NCM” of UTINAM Institute (Université de Franche Comté, Besançon, France). Our studies aims at rendering radiotherapy more specific by concentrating the dose deposition of the radiation in the tumour while sparing the healthy tissues. For achieving this goal, multifunctional gold nanoparticles are in the heart of our research activities since these nanoparticles exhibit a great potential for radiosensitization and medical imaging. Their presence in the tumor will increase the deleterious effect of the radiation in order to specifically eradicate the cancerous cells. The cells appear therefore more sensitive to the therapeutic radiation. Indeed the preferential absorption of the ionizing radiation (X- or γ-rays) by the gold nanoparticles will produce a shower of highly reactive radicals which will seriously alter the tumor. Owing to the combination of medical imaging and therapy, the most opportune moment (high content of nanoparticles in tumour and low content in healthy tissues) can be determined for activating the therapeutic effect of gold nanoparticles. In other words, the radiotherapy is guided by imaging. The treatment by radiotherapy was based on MRT (Microbeam Radiation Therapy). MRT is a non-conventional irradiation technique performed at the ESRF (European Synchrotron Radiation Facility, Grenoble, France). The therapeutic radiation is constituted by an array of parallel microbeams.

A schematic illustration showing how nanoparticles or other cancer drugs might be used to treat cancer.

A schematic illustration showing how nanoparticles or other cancer drugs might be used to treat cancer.

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Light meets Gold

During the last decade oncological diseases have spread enormously. According to the statistics of World Health Organization, cancer takes second place in the list of leading lethal diseases. The first place goes to cardiovascular diseases. Only in 2008 more than 7.6 million people died from cancer worldwide. In order to improve survival factors, early diagnostics and effective therapy is a necessity.

Fluorescence imaging is a sensitive and quantitative method that is widely used for observing cells and cell processes in vivo, also for noninvasive tissue imaging, which is a promising tool for cancer diagnostics. Unfortunately, the sensitivity of fluorescence imaging is limited due to characteristics of fluorescent agents applied. In biological studies most commonly used fluorophores are organic dyes and semiconductor quantum dots. Currently another type of imaging agents has been shown to have a particularly great promise in bioimaging – fluorescent gold nanoclusters. Being composed of non-toxic elements and having surface that could be easily modified with antibodies, biomarkers or functional molecules, they also possess properties such as high fluorescence yield and good biocompatibility.

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