Study of aminosalicilic acid derivatives as innovative $Fe^{3+}$ chelating agents in Fricke gel dosimetry.

This work concerns the optimization of the Polyvinyl alcohol (PVA) hydrogel matrix used in the Fricke gel (FG) dosimetry with the aim to reduce the spatial and temporal instability of the dosimeter induced by the $Fe^{3+}$ ions diffusion and, consequently, to reduce the distance between such promising system and its application in clinical scenario. The research aims to propose new $Fe^{3+}$ ligands with a simple chemical structure that allows the covalent functionalization of the PVA matrix with few steps and with high yield, in order to block the ions diffusion. Among other, 4-aminosalicilic acid (4-ASA) and 5-aminosalicilic acid (5-asa) derivatives are selected as chelating agents since they are able to form iron complexes which show a broad light absorbance band at 517 and $548 {nm}$, respectively, whose intensity is linearly proportional to the adsorbed dose. A complete characterization of the new matrix is provided in terms of strength of formulation, in particular physical-chemical properties, dosimetric properties and stability over the time. Preliminary results have shown that 4-ASA is effectively a promising compound for improving FG dosimetry.