Evaluation of (99m)Tc labelled poly lactic acid microspheres for diagnostic radioembolization

ERGÜN E., Ercan M., Selek H., Kaş H., Ruacan Ş., Ünsal I., ...More

Journal of Microencapsulation, vol.17, no.4, pp.509-518, 2000 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 17 Issue: 4
  • Publication Date: 2000
  • Doi Number: 10.1080/026520400405750
  • Journal Name: Journal of Microencapsulation
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.509-518
  • Keywords: (99m)Tc-poly lactic acid, Radioembolization
  • Hacettepe University Affiliated: Yes


Radioembolization is used in diagnostic imaging of the lungs and for radioembolization therapy of hepatic tumours. Presently, (99m)Tc labelled macroaggregates or microspheres of human serum albumin (HAM) are used for this purpose. Poly lactic acid (PLA) is biodegradable, like HAM, and, unlike HAM, is not a blood product. The aim of the present study was to evaluate the uptake and biodegradation of PLA microspheres in lungs. PLA (MW = 48,720 Da) microspheres of 1.0-100 μm (mean = 39.5 μm) in diameter were prepared by solvent evaporation from methylene chloride. They were labelled with (99m)Tc by stannous chloride reduction at pH 3, with an efficiency of 98% and a stability of 96% at 24 h. For biodistribution studies, 15 mice were i.v. injected with 20 μCi (99m)Tc-PLA microspheres in 0.1 ml and sacrified at 15 min, 1, 3, 6 and 24 h (three at each time point). All the organs were removed, weighed and counted against a standard prepared from 1/100 dilution of the injected radioactivity. Some mice were similarly injected and sacrified at 30 min, 15 and 30 days. The lungs were removed and frozen, and 10 μm sections were obtained, stained with haemotoxylin and eosin and examined under a light microscope. Five rabbits were i.v. injected with 1 mCi of (99m)Tc-PLA microspheres. Scintigrams were obtained at various intervals up to 24 h. In mice, the lung uptake was significant at 30 min-1 h post-injection. In rabbits, the lungs were the only organs visualized up to 24 h. Microscopic examination of tissue sections demonstrated slow biodegradation of PLA particles. In conclusion; (1) The high lung uptake obtained in mice and rabbits indicates the suitability of PLA microspheres for lung imaging, and (2) although the slow biodegradation rate might be a disadvantage in patients with lung disorders in diagnostic studies, it may be an advantage in therapeutic applications with radionuclides which have long physical half lives.