Degradation of poly-L-lactide. Part 2: increased temperature accelerated degradation

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Orthopaedic Engineering

Background:

• Poly-L-lactide (PLLA) is a key bioresorbable polymer used in orthopaedic devices.
• PLLA degradation via hydrolysis takes over five years in vivo.
• Accelerated degradation studies are needed to predict long-term performance.

Purpose of the Study:

• To evaluate the accelerated degradation of PLLA at elevated temperatures (50°C and 70°C).
• To compare degradation mechanisms at accelerated rates versus physiological conditions.
• To develop degradation models and assess the impact of temperature on PLLA properties.

Main Methods:

• PLLA pellets compression molded into tensile test specimens.
• Sterilization using ethylene oxide gas (EtO).
• Degradation in phosphate-buffered solution (PBS) at 50°C and 70°C, with analysis at intervals.

Main Results:

• Degradation mechanisms at 50°C and 70°C were similar to those at 37°C (in vitro and in vivo).
• Degradation models showed mass loss, melting temperature, and Tg dependence on molecular weight.
• Elevated temperatures accelerate PLLA degradation but may introduce testing limitations.

Conclusions:

• Increased temperature is effective for accelerating PLLA degradation studies.
• Concerns exist regarding testing PLLA above its glass transition temperature (Tg).
• The significance of autocatalysis at higher temperatures requires further investigation.