A route to high radioactivity 3H-labelled PLA polymers

✍ Scribed by Isabelle Dos Santos; Jean-Louis Morgat; Michel Vert

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 149 KB
• Volume: 48
• Category: Article
• ISSN: 0959-8103
• DOI: 10.1002/(sici)1097-0126(199904)48:4<283::aid-pi123>3.0.co;2-v

✦ Synopsis

In the üeld of degradable and biodegradable polymers, monitoring the fate of degradation products in complex living systems such as an animal body or the environment, is going to be a major task with the development of forth-coming regulations. For this, radiolabelling is a powerful tool, provided that no undesired radioactive leachables lead to artifactual observations. Therefore, a method to synthesize highly radioactive polylactide polymers has been investigated. isotope 1 1H Ç 1 3H exchange was achieved on L-and DL-lactides using tritium gas and as catalyst. Radioactive Pd/CaCO 3 lactides with speciüc activities ranging up to 111-148 GBq mmol-1 (3-4 Ci mmol-1) were obtained. With these lactides, PLA50, PLA96 and PLA100

were synthesized with speciüc (M 1 w = 25 000-60 000) radioactivities in the range 29.6-44.4 MBq mg-1 (0.8-1.2 mCi mg-1). It was shown that no more than 0.45% of volatile radioactive compounds were formed within a typical polymer, namely PLA50, which was allowed to stand in air at 4ÄC for 200 days. PLA50 tablets and thin ülms were allowed to degrade hydrolytically in an iso-osmolar pH 7.4 phosphate buþ er solution at 37ÄC for several weeks. The appearance of radioactive leachables in the aqueous medium agreed well with the heterogeneous degradation mechanism previously proposed to account for the behaviour of large-size cold PLA polymers in vitro and in vivo. Data are discussed with respect to the use of radioactive PLA as tracers in the animal body and in model compost.