Preparation and evaluation of ¹⁸⁸ Re sulfide colloidal nanoparticles loaded biodegradable poly (L-lactic acid)...

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 ¹⁸⁸ Re loaded poly (L-lactic acid) (PLLA) microspheres through ¹⁸⁸ Re sulfide colloidal nanoparticles (¹⁸⁸ Re-SC nanoparticles). The formation of ¹⁸⁸ Re-SC nanoparticles was confirmed by ultraviolet-visible spectrophotometry. The labeling yield of ¹⁸⁸ Re-SC nanoparticles was verified using the RTLC method. Effects of synthesis parameters on morphology and size of prepared ¹⁸⁸ Re-sulfide colloidal-PLLA microspheres (¹⁸⁸ Re-SC-PLLA microspheres) were studied by scanning electron microscopy. In vitro stability of ¹⁸⁸ Re-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 ¹⁸⁸ Re-SC-PLLA microspheres are suitable candidate for clinical studies.