Nanoscale insights on hypoxia radiosensitization with ion beams

Tumors with a nonuniform oxygen distribution show also an inhomogeneous radiosensitivity. In particular, the hypoxic regions results to be more radioresistant, limiting the efficacy of radiotherapy. It has been observed that high linear energy transfer, LET, radiation can counteract this effect to a certain extent, suggesting ion beam therapy as one of the most promising strategies to treat hypoxic tumors. On the nanoscale, the oxygen effect is assumed to be related to the indirect action of radiation. Several theories exist that aim to provide an explanation of the nature of this effect and its LET dependence, on the radiation chemistry. However, a mechanistic description is still missing and little is known about the indirect action and the chemical processes taking place along an ion track. In this work, the Monte Carlo particle track structure code TRAX has been extended to the pre-chemical and chemical stage of the radiation effect and is now able to simulate the chemical evolution of the most important products of water radiolysis under different irradiation conditions and target oxygenation levels. The validity of the model has been verified by comparing the calculated time and LET-dependent yields of the different radiolytic species to experimental data and other simulation approaches. As an example of the application of the newly implemented TRAX-CHEM code, a study on the dose enhancement effect and radical enhancement effect of gold nanoparticles has been performed under varying irradiation conditions and oxygenation levels. This will contribute to the basic understanding of still unsolved mechanisms for nanoparticle sensitization

Nanofibers - production, properties and functional applications

With the rapid development of nanoscience and nanotechnology over the last decades, great progress has been made not only in the preparation and characterization of nanomaterials, but also in their functional applications. As an important one-dimensional nanomaterial, nanofibers have extremely high specific surface area because of their small diameters, and nanofiber membranes are highly porous with excellent pore interconnectivity. These unique characteristics plus the functionalities from the materials themselves impart nanofibers with a number of novel properties for applications in areas as various as biomedical engineering, wound healing, drug delivery and release control, catalyst and enzyme carriers, filtration, environment protection, composite reinforcement, sensors, optics, energy harvest and storage , and many others. More and more emphasis has recently been placed on large-scale nanofiber production, the key technology to the wide usages of nanofibers in practice. Tremendous efforts have been made on producing nanofibers from special materials. Concerns have been raised to the safety issue of nanofibrous materials. This book is a compilation of contributions made by experts who specialize in their chosen field. It is grouped into three sections composed of twenty-one chapters, providing an up-to-date coverage of nanofiber preparation, properties and functional applications. I am deeply appreciative of all the authors and have no doubt that their contribution will be a useful resource of anyone associated with the discipline of nanofibers