Gold Nanoparticles by Laser Ablation for X-Ray Imaging and Protontherapy Improvements

Gold nanoparticles, 5-20 nm in diameter, were generated with a pulsed Nd: YAG laser at 1010 W/cm2 at solution concentrations ranging between 1-100 mg/ml. The incremental X-ray contrast imaging using gold nanoparticles was investigated and measured. The study was performed with the aim to enhance the massive absorption coefficient of X-ray radiation in the tumor for medical image quality and to improve traditional X-ray radiotherapy or proton therapy. A simulation of proton therapy improvement was conducted using a human ocular melanoma model, placed 3 cm behind the eye lens, and testing 60 MeV protons. Calculations suggest that the local injection of a solution containing Au-NPs may increase the proton energy released in the tumor above 50%, with the dose in the surrounding tissues leading to an increased probability of tissue healing. A discussion on recent patents in the ambit of the preparation and use of Au nanoparticles in medical imaging and therapy is presented.

Au nanoparticles were characterized using optical absorbance, X-ray fluorescence, SEM, and TEM microscopies. Biocompatible nanoparticle solutions were injected intravenously into tail veins of mice followed by X-ray imaging using 20-45 keV photons to evaluate the uptake and the clearance by different organs of the nanoparticles.

Diagnostic X-ray images of mice in which the Au-NPs were injected showed high spatial resolution contrast of different organs having high up-take. A calculation of the dose released by X-rays, electrons and protons to the tumor site demonstrates that an increment of the order of 50% can be obtained using adapt solution concentration.

The use of Au-NPs in biocompatible solutions injected in living organism permits their blood transport up to different organs. The NPs can be employed as contrast medium to enhance the medical image resolution and to prepare the cancer tissues to be exposed to ionization radiations in order to enhance the dose released to the tumor cells. This effect permits to reduce the total dose given to the patient and to increase the dose released to the tumor cells with respect to healthy ones.