Evaluation of the thermal properties of PLLA/HA and PLLA/45S5 composites for application in bioabsorbable interference screws

Replacement of metals with bioabsorbable polymers has shown promising results for fabrication of biomedical implants. But polymers themselves have some restrictions such as inability in osteoconduction and integration with surrounding tissue, induce foreign body reactions, reducing of pH by degradation products which can results in unwanted inflammatory reactions in related place, and weak mechanical properties in compare to metallic types. In order to alleviate these problems using of polymeric composites including bioactive particles is taken into consideration. In the present work 45S5 bioactive glass and hydroxyl apatite (HA) ceramic particles were used for fabrication of poly(L-Lactic acid) (PLLA) composite screws. Microstructure and thermal properties of produced samples were evaluated by differential thermal analysis (DTA), thermogravimetry (TG), scanning electron microscopy (SEM) and particle size analysis (PSA). Also for evaluation of osteogenic activity of produced samples, alkaline phosphatase (ALP) and Alizarin Red Staining assays were carried out and cytotoxicity was conducted through MTT assay. In compare to PLLA screws, PLLA/HA and PLLA/45S5 composites showed more and less thermal stability respectively. The results of cell analysis assays showed no cytotoxicity and both composites revealed proper osteogenesis potentials.