Preparation and evaluation of 188Re sulfide colloidal nanoparticles loaded biodegradable poly (L‐lactic acid) microspheres for radioembolization therapy

Radioembolization with radioactive microspheres has been an effective method for the treatment of liver lesions. The aim of this study was to prepare carrier‐free 188Re loaded poly (L‐lactic acid) (PLLA) microspheres through 188Re sulfide colloidal nanoparticles (188Re‐SC nanoparticles). The formation of 188Re‐SC nanoparticles was confirmed by ultraviolet‐visible spectrophotometry. The labeling yield of 188Re‐SC nanoparticles was verified using the RTLC method. Effects of synthesis parameters on morphology and size of prepared 188Re‐sulfide colloidal‐PLLA microspheres (188Re‐SC‐PLLA microspheres) were studied by scanning electron microscopy. In vitro stability of 188Re‐SC‐PLLA microspheres was investigated in normal saline at room temperature and in human serum at 37°C. In vivo distribution studies and gamma camera imaging were performed in healthy BALB/c mice. The microspheres could be prepared with sizes between 13 and 48 μm (modal value 29 μm) and radiolabeling efficiency >99%. After incubation, the microspheres were found stable in vitro up to 72 hours. The biodistribution after intravenous injection in healthy BALB/c mice showed high accumulation in lung as a first capture pathway organ for microsphere followed by great retention over 48 hours for these microspheres. These data show that 188Re‐SC‐PLLA microspheres are suitable candidate for clinical studies.