Synthesis of silver nanoparticles for X-ray dosimetry

FACUNDO MATTEA; JOSÉ VEDELAGO; CESAR GOMEZ; MIRIAM C. STRUMIA; MAURO VALENTE

Budva

Conferencia; Fifth International Conference on Radiation and Applications in Various Fields of Research (RAD 2017); 2017

The use of nanoparticles in radiotherapy and radiodiagnostic has been widely studied in the past decade, their interactions with photons at different energies give place to the combined diagnosis and therapy (theranostics) and they could even be modified to carry specific drugs or for a better biotoxicity in human organisms. Dosimetric techniques can also take advantage of the beneficial properties of inorganic nanoparticles and their combination with typical dosimetric techniques could be used as a preliminary step for their later inclusion in radiagnostics or radiotherapy treatments. One of the main limitations in the use of inorganic nanoparticles is their colloidal instability, which is typically minimized by using stabilizing agents, such as biopolymers or surfactants to prevent their aggregation and improving at the same time the biocompatibility. This work presents a method to synthesize, purify and characterize silver nanoparticles in a gelatin matrix for dosimetry applications. Porcine skin gelatin was used as stabilizing agent and as a reactive in the thermal reduction of silver nitrate, to provide compatibility with typical gel dosimetry systems. The effect of synthesis variables like temperature, reaction time, and relative concentrations was studied to obtain products with different mean sizes and distributions. The obtained nanoparticles were characterized by different analytical techniques such as TEM, SEM, UV-Vis and gravimetric techniques in order to evaluate their distribution characteristics and the reaction yield. These nanoparticles were used as X-ray fluorescent agents within tissue equivalent materials with low energy X-ray beams at different concentrations and depths within a water equivalent phantom with the aim of assessing their performance as X-ray fluorescent agents useful for nanoparticle detection and/or localization. Finally, the nanoparticles were used in gel dosimeters to quantify the dose enhancement factor, paying special attention to the dose recorded by these materials irradiated with beams of energies below and above the excitation edge of silver. Both applications, as X-ray fluorescent agents in aqueous solutions and as dose enhancers in dosimetric systems were compared to MC simulations with similar setups. The results indicated that nanoparticles with mean sizes ranging from 2 to 20 nm, with a lognormal distribution were obtained by means of the proposed production process. Both the mean size, and standard deviations of the distributions were mainly dependent on the gelatin concentration and temperature. The overall yield of the synthesis was around 61% w/w, and a thorough purification method was applied to obtain a pure product. The X-ray fluorescence of these nanoparticles in aqueous solutions was successfully detected with concentrations as low as 0.005 mol/L and depths within a water-equivalent phantom from 1 mm to 15 mm.