Demetris Zamboulis

Polyhedral iron oxide core–shell nanoparticles in a biodegradable polymeric matrix: preparation, characterization and application in magnetic particle hyperthermia and drug delivery

Polyhedral magnetic iron oxide nanocrystals with multiple facets have been embedded in biocompatible and biodegradable polymeric matrices in order to study their structural, magnetic features and alternating-current (AC) magnetic heating efficiency. The encapsulation of iron oxide nanoparticles into a polymer matrix was confirmed by transmission electron microscopy and further corroborated by high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). HAADF-STEM tomography proved that the iron oxide nanocrystals consist of well-defined polyhedral structures with multiple facets. The magnetic features were found to be in good agreement with the structural and morphological features and are maintained even after encapsulation. Furthermore, the magnetic nanoparticles inside these matrices may be considered as good candidates for biomedical applications in hyperthermia treatments because of their high heating capacity exhibited under an alternating magnetic field. The anticancer Taxol drug was encapsulated in these nanoparticles and its physical state and release rate at 37 and 42 °C was studied.

Effect of some current antioxidants on the thermo-oxidative stability of poly(ethylene terephthalate)

Abstract Four current commercial antioxidants (Naugard 445, Ethanox 330, Irganox 1098 and a blend of Irganox 1098 and 1019) were added during synthesis of poly(ethylene terephthalate) in order to test their thermo-oxidative stability and eventually to obtain more thermostable products during synthesis and processing. Their stabilization effect was evaluated by DSC analysis in nitrogen and air, using as criteria the stabilization coefficient and the induction period of oxidation. At low concentrations (0·03% and 0·10%), under the conditions used, better results were obtained with Naugard 445 and Ethanox 330, while at higher concentrations (0·5% and 1·0%) Irganox 1098 and the blend of Irganox 1098 and 1019 were better than the others.

Antioxidants for poly(ethylene terephthalate)

Polymers undergo oxidation reactions when heated in air. Heating of the polymer takes place at any stage of the life of the polymer, e.g. during polymerization, processing or end use of the ready product. Oxidation results in chain scission, branching, crosslinking or formation of oxygen-containing functional groups and leads to deterioration of physical properties and discoloration of the polymer. Antioxidants are added at low concentrations during production or processing of polymers to minimize the adverse effects of thermo-oxidation. Now that recycling of post-consumer polymers is of increasing importance, the use of antioxidants is a good way to avoid deterioration of physical properties and discoloration of the polymer during reprocessing.