Abstract
To investigate the mechanical and physical properties of, and the histological reaction to, as-polymerized poly(96L/4D-lactide) (PLA96), a degradation study was performed in vitro and in rats. The PLA96 studied had a molecular weight (Mw) of 1.5×106 g/mole. Test samples were implanted subcutaneously in the back of rats or put in phosphate-buffer. The mechanical and physical properties of PLA96 showed major changes during the first 3 weeks of degradation. Tensile strength (δb), impact strength and Mw decreased rapidly. The heat of fusion (ΔHm), a measure for crystallinity, increased whereas the melting temperature (Tm) remained almost constant. The mechanical properties were lost completely after 7 weeks of degradation. After 55 weeks, both water absorption and mass loss had reached approximately 30%, and Mw had decreased to 15×103 g/mole. ΔHm had slightly increased further but Tm remained unchanged. The measurements during degradation in vitro did not show significant (p>0.05) differences from the measurements during degradation in vivo. The histological reaction to PLA96 could be characterized as a mild foreign body reaction without signs of inflammation.
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