PROTEC

Supercritical Carbon Dioxide Processing Technology for Biodegradable Polymers Targeting Medical Applications

The Protec project aimed to develop an innovative 'supercritical fluid' processing technology that enabled the production of biodegradable/bioabsorbable polymers ensuring consistent and well defined mechanical properties, chemical composition, porosity and degradation profile.

This technological advance was realised through addressing the scientific and technological gap between fundamental academic research and industry and through further developing advanced process control methodologies. The processing technology developed within the project has been designed to enable efficient integration with existing extrusion and injection moulding machines.

The key project objectives were:

• The processing of porous biodegradable polymers that retain the physical and mechanical properties of the compact material (Trexel Microcellular technology).
• To achieve significant reductions in processing degradation for thermal and shear sensitive polymers.
• To establish the fundamental relationship between injection moulding variables/ parameters and the final part properties (surface and interior properties of the material) and to establish the parameters that lead to process control.
• To achieve process control of material biodegradation profile.
• To achieve industrial application with consistent and reliable process control.
• To establish the limitations of material design due to the degradation that occurs during sterilisation, and to identify sterilisation best practice.

Organisational Information

Budget: €2.1M
Funding: €1.4M
Start Date: June 2005
Finish Date: November 2008
Duration (in months): 42
Lead Partner (Co-ordinator): University of Birmingham, UK

Participants

Results – What happened next?

Initially, the project identified a series of biodegradable polymer implants that could benefit from the addition of supercritical CO2 during processing.

The applications identified were:

• Tissue scaffolds
• Suture anchors or screws
• Drug depot systems

A specification was drawn up, and developments undertaken in integrated materials, and process development and characterisation.

Several candidate materials, including some based on polylactide were synthesised and characterised. In an iterative process, the most promising materials were selected for further testing, which included:

• Degradation studies
• Biological testing
• Sterilisation investigations using irradiation
• The relationship between the bulk and supercritical CO2
• Porosity formation and stability in the polymer
• Mechanical property studies

Scale-up of the process has seen the production of parts for the three candidate applications using supercritical CO2 and extrusion, injection moulding and batch processing routes. The complex interactions in the polymer/CO2 systems have been investigated to establish the parameters necessary for process control.

The final demonstrator product chosen for testing was a biodegradable rod of the type used for internal fixation in extremity fractures and osteotomies. A range of these rods have been produced in medical grade PLA, and have undergone a series of rigorous test protocols including sterilisation, biocompatibility and biodegradation.

Protec offers the medical technology sector a highly efficient supercritical fluid processing technology that will not only confer advantageous properties to their products – such as increased biocompatibility – but will also reduce costs, both in terms of the materials and energy consumed. This will in turn benefit the health and environment of citizens throughout the EU.

Project website: www.euprotec.eu