MEDICAL APPLICATIONS OF PARTICLE-INDUCED X-RAY EMISSION

Abstract

We report two medical applications of particle-induced X-ray emission (PIXE) as described below (1) Observation of biological events: The kinetics of trace elements during the initiation of radiation-induced apoptosis (RIA) was observed using a micro-PIXE and PIXE. RIA is a process in which irradiated cells commit suicide; it results in the removal of severely damaged and harmful cells. During RIA, cytochrome c is released from the mitochondria and reaches the nucleus, where it activates a Ca- or Mg-dependent endonuclease. We examined this phenomenon by using a micro-PIXE and PIXE. A high concentration of Fe was detected in the stroma of cells in the early apoptotic phase. We also observed accumulation of large amounts of Ca and Mg in the nucleus.(2) Development of liquid-core microcapsules for novel cancer chemoradiotherapy: Currently, we are developing liquid-core (containing an anticancer drug) microcapsules that release their core content upon irradiation. These microcapsules will localize the anticancer drug within the irradiated field. The outer shell of these microcapsules is prepared from alginate and hyaluronic acid and polymerized by Fe, while the anticancer drug Paraplatin®(carboplatin) containing Pt is the liquid core. The micro-PIXE revealed that these microcapsules released their core content after irradiation, and the amount of carboplatin released was measured by PIXE. More than 83.1% ± 8.3% of the microcapsules were ruptured, and the amount of carboplatin released was more than 81.2% ± 2.3%. Thus, the combination of radiotherapy and chemotherapy showed improved antitumor effects and a decrease in adverse effects because of drug localization.