Invibio's PEEK-OPTIMA Polymer Rivals Commercially Pure Titanium for in vitro Performance

Invibio®, a leading provider of biomaterial solutions to the medical device market, today released data from an in vitro study conducted in conjunction with the University of Connecticut Health Center, Department of Orthopedic Surgery. The study observed the cellular response of human primary osteoblasts to Invibio's PEEK-OPTIMA® polymer compared with grade 1 commercially pure titanium (cpTi). The findings were presented today in a poster session at the Society for Biomaterials annual meeting.

The research indicates that the in vitro performance of unfilled PEEK-OPTIMA polymer and carbon fiber-reinforced (CFR) PEEK-OPTIMA compound measured against common indicators of cytocompatibility (such as adhesion, growth and differentiation) is comparable to that of grade 1 cpTi, which is commonly used as a first choice material for dental implants.

Furthermore, the study shows some similarities with findings for other biomaterials in that different cell responses can occur depending on the composition, roughness and other topographical features of the material generated during common manufacturing techniques (such as polishing, injection molding or machining).

The study, using a well developed in vitro model published by researchers at the University of Connecticut, observed differentiated bone cells and mineralization upon the PEEK-OPTIMA surfaces which was comparable to the titanium controls.

This latest observation, along with the growing number of published findings using the polymer, suggests that PEEK-OPTIMA may lend itself to osseointegration - the direct connection between bone and implant surface. The versatile polymer is currently used for a wide range of medical device applications either alone or as a vehicle for additional surface enhancements, such as coatings.

"PEEK-OPTIMA polymer is being examined and adopted as an alternative to titanium in the development of implantable medical devices because of its exceptional biocompatibility, physical, mechanical and imaging properties," said Lynne Todd, technical director of Invibio. "This research suggests that the cellular interaction at the tissue-material interface of PEEK-OPTIMA polymer could be comparable to that of titanium for certain applications. As PEEK-OPTIMA's usage becomes more widespread, further knowledge will be gained regarding its role in osseo, fibrous-osseous and bio-integration."

Material and Methods

Implantable grade unfilled PEEK-OPTIMA polymer and CFR PEEK-OPTIMA compound were prepared as disks with the surface presented to the cells being either injection molded or machined. As a control reference comparison, commercially pure grade 1 titanium disks with either roughened (cpTi unpolished) or polished (cpTi polished) surfaces were also presented to the bone cells.

Human primary osteoblasts (HOBs) were seeded onto sample disks at a density of 1 x 10(4) cells/cm(2). Cellular adhesion was measured after four hours and proliferation at 48 hours by (3H)-thymidine incorporation. To assess osteogenic activity and differentiation, alkaline phosphatase (ALP) was measured at 72 hours and mineralization after three weeks total culture time.

Results

All test biomaterials demonstrated HOB adhesion at four hours. The cpTi showed no significant difference between surface types. Smoother injection molded PEEK-OPTIMA surfaces demonstrated no significant difference in adhesion when compared to cpTi. Proliferation at 48 hours was significantly greater (p=0.01) on the injection molded unfilled PEEK-OPTIMA compared to all other test materials. The type of surface on titanium (polished or unpolished) or CFR PEEK-OPTIMA (injection molded or machined) did not have a significant effect on the proliferation.

ALP activity at 72 hours was greatest on injection molded unfilled PEEK-OPTIMA and polished titanium, with no significant difference between them. The surface finish within each material tested had some significant effect on the ALP activity measured.

For mineralization, there was no significant difference between the best performing cpTi (unpolished), injection molded CFR PEEK-OPTIMA or either surface type of the unfilled PEEK-OPTIMA. These biomaterials demonstrated significantly higher calcium content than the polished cpTi or machined CFR surfaces after a total of three weeks culture.

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