Crystallinity and lateral crystallite size of different UHMW PE materials

Alendronate Release from UHMWPE-Based Biomaterials in Relation to Particle Size of the GUR Powder for Manufacturing

Ultra-high molecular weight polyethylene (UHMWPE) is widely used in endoprosthetics and has been the subject of countless studies. This project investigates the dependence of alendronate (AL) release on the molecular weight of the UHMWPE used (GUR1020 and GUR1050). A 0.5 wt% AL was added to the UHMWPE during the production of the moldings. In addition to the 14-day release tests, biocompatibility tests such as live dead assay, cell proliferation assay (WST) and Lactate dehydrogenase test (LDH) with MG-63 cells as well as a tensile test according to DIN EN ISO 527 were carried out. The released AL concentration was determined by HPLC. A continuous release of the AL was observed over the entire period of 2 weeks. In addition, a correlation between molar mass and AL release was demonstrated. The GUR1020 showed a release four times higher than the GUR1050. Both materials have no negative influence on the proliferation of MG-63 cells. This was also confirmed in the live/dead assay by the increase in cell count. No cytotoxicity was detected in the LDH test. The addition of 0.5 wt% AL increased the elongation at break for GUR1020 by 23% and for GUR1050 by 49%. It was demonstrated that the choice of UHMWPE has an influence on the release of AL. The particle size in particular has a strong influence on the release behavior.

Morphology of chemically crosslinked ultrahigh molecular weight polyethylene

Morphological characterization of chemically crosslinked ultrahigh molecular weight polyethylene was performed by differential scanning calorimetry and scanning electron microscopy. The lamellar thickness of nascent UHMWPE inferred from DSC endotherms showed a very broad distribution, which was reduced significantly after melting and recrystallizing in DSC. Peroxide crosslinking further reduced the lamellar thickness distribution compared to uncrosslinked samples. After gamma-irradiation, a slowly cooled peroxide-free sample showed a greater increase in lamellar thickness distribution. Examination of the morphology of freeze-fractured surfaces by SEM showed that a slowly cooled peroxide-free UHMWPE exhibited a rougher fracture while chemically crosslinked samples showed a smoother fracture. After compression molding at 300 degrees C for 2 h, the grain boundaries between particles disappeared for all UHMWPE samples, indicating a complete fusion of the original flakes.