在生醫骨植體的演進過程中，由於金屬鈦與其合金擁有最符合骨科植體要求的生物相容性、機械性質及抗腐蝕性質等等，使其成為最適合的材料系統。然而，骨材本身的彈性模數亦扮演了相當重要的角色，骨材與人骨之間的彈性模數若差距過大則易導致骨質鬆脫與骨質再吸收等現象(應力遮蔽效應)，像是cp-Ti (~105 GPa) 及Ti-6Al-4V (~112 GPa) 與人骨的彈性模數(~30 GPa) 仍有一段差距，所以為了避免應力遮蔽效應的產生，β相穩定因子(鈮、鉭、鋯)用來參雜鈦金屬(Ti-28Nb-11Ta-8Zr, TNTZ)以降低鈦合金骨材的彈性係數以達到仿骨又不失去生物相容性的特性，並對體液的抗腐蝕性也因此增強了許多。此外，為了模擬骨細胞外基質的奈米孔洞結構，陽極氧化表面改質技術被用來製成高附著性、化學穩定性及粗糙性的非晶奈米孔洞氧化層。再者，為了避免手術過程中及術後的細菌感染，我們合成銀奈米粒子並將其附著於奈米孔洞氧化層上以利手術成功及加速術後傷口癒合。
首先，我們量測TNTZ的機械性質:彈性模數 (49 GPa)、衝擊強度 (129 J/cm2)、降伏強度 (338 MPa) 及拉伸強度 (422 MPa)。接著藉由X-ray光電質譜儀 (XPS)及掃描式電子顯微鏡 (SEM)進行奈米孔洞表面改質之TNTZ及銀奈米粒子的表面成分及形貌分析。再者我們利用電位極化法檢測TNTZ以及陽極氧化之TNTZ的抗腐蝕性，將其與商用純鈦之抗腐蝕性做比較。最後，訂性的抑菌環及定量的細菌生長曲線觀察被用來檢測載有銀奈米粒子的奈米孔洞TNTZ氧化層能夠抑菌的效率及時間，分別測試綠膿桿菌(P. aeruginosa)以及抗藥性金黃色葡萄球菌(MRSA)，抑制效果分別為24 h及12 h。體外骨母細胞培養則被用來觀察細胞增生及生存能力，證實表面改質之TNTZ能夠促進細胞生長。因此，TNTZ合金在生醫領域上是個具有發展潛力的植體。

Titanium and Ti-based alloys are widely applied in the orthopedic implants due to their qualified biocompatibility, mechanical properties, corrosion resistance and so on. However, the elastic modulus of commercial pure Ti (cp-Ti, ~105 GPa) and Ti-6Al-4V (Ti64, ~112 GPa) are still far larger than that of real bone (4-40 GPa), which easily causes stress-shielding effect and subsequently leads to the bone or implant failure. To avoid this problem, Ti-28Nb-11Ta-8Zr alloy (TNTZ) with a low elastic modulus (49 GPa) is utilized in this study to meet the bone-mimetic condition with improved biocompatibility and corrosion resistance in the environment of simulated body fluid, Hank’s solution. Additionally, to mimic bone extracellular matrix (ECM), the nano-sized porous structure for sturdy cell interlocks was carried out by anodic oxidation (AO). The as-prepared amorphous nanoporous oxides exhibit the characteristics of highly adhesive coatings, chemical inertness and rough surface morphology to serve as the study platform. Concerning with infection issues before and after the surgery, we also proposed an antibacterial agent, Ag nanoparticles (AgNPs), incorporated into the cavities of oxide coatings to assist in surgery success and rapid healing rate.
Firstly, the mechanical properties of TNTZ were evaluated by measuring Young’s modulus, impact strength, yield and tensile strength. Subsequently, material characteristics of Nanoporous TNTZ oxide coatings (NPTNTZO) with AgNPs were analyzed, including surface morphologies by scanning electron microscopy (SEM) and chemical compositions by X-ray photoelectron spectroscopy (XPS). Thirdly, potentiodynamic polarization method was conducted to test corrosion resistance of TNTZ and AO TNTZ coatings, compared with that of cp-Ti. Finally, in-vitro bacteria tests were practiced to observe the antimicrobial efficacy of as-prepared NPTNTZO/ AgNPs and in-vitro cell tests were utilized to determine the cell viability and proliferation.
Experimental results indicated that TNTZ possesses lower elastic modulus (49 GPa) than cp-Ti and T64 implants and it still remains high impact strength, yield strength and tensile strength compared with other commonly used bone metals, like stainless steels. Besides, TNTZ and its oxide coatings also improve corrosion resistance compared with titanium and titania coatings. In aspect of surface modification through anodization, different applied voltages can lead to different pore diameters. During the osteoblast culture, size effect is obvious that smaller diameter (<30 nm) is beneficial for cell proliferation and larger diameter (>70 nm) gives the opposite results. Here we chose 65 nm nanopores as reservoir to store AgNPs to precede in-vitro bacteria tests and osteoblast culture, which still maintained certain degrees of cell proliferation and viability (MTT assay and Live/Dead Staining). As for antibacterial tests, qualitative Kirby-Bauer test, inhibited zone observation, reveals that NPTNTZO/ AgNPs effectively inactivate both gram-negative bacteria strains (Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa)) and gram-positive bacteria (Staphylococcus aereus (S. aereus) and Methicillin-resistant Staphylococcus aureus (MRSA)). Quantitative test of antibacterial efficiency was presented by growth curve of P. aeruginosa and MRSA. The efficiency at least reaches 24h and 12h respectively in such a strict environment (high volume of bacteria solution).
The final MTT assay and Live/Dead Staining show that silver-containing samples (NPTNTZO/ AgNPs) have little cytotoxicity on osteoblast culture under 2.5 mM silver concentration. This study successfully investigates the comprehensive evaluations of material characteristics, in vitro antibacterial tests and cellular activities on the bases of β-Ti-28Nb-11Ta-8Zr bone implant.

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