聚乳酸屬於可降解型之生醫高分子材料，在生物力學、生物可降解性以及生物相容性等方面都具有良好的性質，其中的可降解性更能避免需二次開刀取出植入材的痛苦。然而，因聚乳酸有降解速率緩慢、生物活性不佳以及骨誘導性不足的缺點，這些都是聚乳酸作為骨組織工程應用上待克服的問題。因此，本研究設計以純鎂與磷酸鈣粉末作為添加相，藉此加速整體複合材料的降解速率，同時也利用鎂與磷酸鈣降解後釋放的離子效應，提升複合材料的生物活性與骨誘導性，並進一步探討其機械性質與生物特性。
本研究選用聚乳酸、純鎂粉末以及磷酸鈣粉末形成三相複合之可降解型生醫材料，藉由不同比例的粉體添加來探討其對於複合材料性質之影響，並透過拉伸試驗、衝擊試驗與硬度試驗評估材料機械性質。為了解其生物降解特性，以生理食鹽水及模擬人工體液進行浸泡試驗並測量pH值，最後透過細胞毒性試驗檢視複合材料的生物相容性。
根據試驗結果，有粉體添加的複合材料之拉伸強度與衝擊強度均下降，延性僅存在於少部份的添加配比；而各添配條件之楊氏係數均符合人骨範圍，能避免因應力遮蔽效應所產生之傷害；硬度方面則因粉末分散強化效應而有些微提升。綜合以上機械性質與應用研究目的考量，以PLA10M10C (10wt.% Mg, 10wt.% Ca3(PO4)2)之表現最佳。
在生物降解試驗中，添加純鎂與磷酸鈣粉末會使整體複合材料加速降解，並形成多孔性的表面形貌，生成具有生物相容性之單鈣磷酸、三鈣磷酸以及磷酸鈣鎂等鹽類，能有助於骨組織的癒合與新生。在降解試驗的綜合性評估下，仍以PLA10M10C之表現最佳。生物相容性試驗則顯示，本研究所聚焦之四組材料 (PLA, PLA20M, PLA20C, PLA10M10C)均屬於0級細胞毒性 (No cytotoxic)，表示對組織細胞不會產生毒性反應，符合生物安全性之評估。根據本研究系統，可提供新型可降解生醫複合材料PLA10M10C於骨科植入材應用參考。

Polylactic acid is a biodegradable polymer with good properties in biomechanics, biodegradability and biocompatibility. However, it has disadvantages of slow degradation rate, poor bioactivity and insufficient osteoconductivity, which are problems need to be solved in the application of bone tissue engineering. Therefore, this study try to design a three-phase biomedical composite which composed of polylactic acid, magnesium and calcium phosphate. The effect of the composite with different proportions of powder addition was investigated by mechanical tests, degradation test and biocompatibility tests.
The results show that additional powder will decrease the tensile and impact properties of the composite, but Young’s modulus are all within the range of human bone which can avoid the stress shielding effect. Hardness is slightly increase by the effect of dispersion strengthening of powder.
In addition, the degradation rate and biological properties are both enhanced by magnesium and calcium phosphate. The degradation products such as monocalcium phosphate, tricalcium phosphate and calcium magnesium phosphate are all biocompatible salts and have the ability to promote bone tissue healing and renew. Also, the biocompatibility tests show that the composites have no cytotoxicity and the surfaces are good environments for cells to spread and proliferate.
All in all, under the comprehensive evaluation, PLA10M10C (Mg 10wt.%, Ca3(PO4)2 10wt.%) is the most suitable biodegradable composite for orthopedic implants in this study.

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