Synthesis and characterization of hydroxyapatite modified with (9r)-9-hydroxystearic acid

(9R)-9-hydroxystearic acid (9R-HSA) has been proven to have antitumoral activity because it is shown to inhibit histone deacetylase 1, an enzyme which activates DNA replication, and the (R)-enantiomer has been shown to be more active than the (S)-enantiomer both in vitro and by molecular docking. Hydroxyapatite is the main mineral component of bone and teeth and has been used for over 20 years in prostheses and their coating because it is biocompatible and bioactive. The goal of incorporating 9R-HSA into hydroxyapatite is to have a material that combines the bioactivity of HA with the antitumoral properties of 9R-HSA. In this work, 9R-HSA and its potassium salt were synthesized and the latter was also incorporated into hydroxyapatite. The content of (R)-9-hydroxystearate ion incorporated into the apatitic structure was shown to be a function of its concentration in solution and can reach values higher than 8.5%. (9R)-9-hydroxystearic acid modified hydroxyapatite was extensively characterized to determine the effect of the incorporation of the organic molecule. This incorporation does not significantly alter the unit cell but reduces the size of both the crystals as well as the coherent domains, mainly along the a-axis of hydroxyapatite. This is believed to be due to the coordination of the negatively charged carboxylate group to the calcium ions which are more exposed on the (100) face of the crystal, therefore limiting the growth mainly in this direction. Further analyses showed that the material becomes hydrophobic and more negatively charged with the addition of 9R-HSA but both of these properties reach a plateau at less than 5% wt of 9R-HSA.

Pulse shape studies of neutral particles with a liquid scintillator

The hadrontherapy exploits beams of charged particles against deep cancers. These ions have a depth-dose profile in which there is a little release of energy at the beginning of their path, whereas there is a sharp maximum, the Bragg Peak, near its end path. However, if heavy ions are used, the fragmentation of the projectile can happen and the fragments can release some dose outside the treatment volume beyond the Bragg peak. The fragmentation process takes place also when the Galactic Cosmic Rays at high energy hit the spaceship during space missions. In both cases some neutrons can be produced and if they interact with the absorbing materials nuclei some secondary particles are generated which can release energy. For this reason, studies about the cross section measurements of the fragments generated during the collisions of heavy ions against the tissues nuclei are very important. In this context, the FragmentatiOn Of Target (FOOT) experiment was born, and aims at measuring the differential and double differential fragmentation cross sections for different kinetic energies relevant to hadrontherapy and space radioprotection with high accuracy. Since during fragmentation processes also neutrons are produced, tests of a neutron detection system are ongoing. In particular, recently a neutron detector made up of a liquid organic scintillator, BC-501A with neutrons/gammas discrimination capability was studied, and it represents the core of this thesis. More in details, an analysis of the data collected at the GSI laboratory, in Darmstadt, Germany, is effectuated which consists in discriminating neutral and charged particles and then to separate neutrons from gammas. From this analysis, a preliminary energy-differential reaction cross-section for the production of neutrons in the 16O + (C_2H_4)_(n) and 16O + C reactions was estimated.