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The biocompatibility of the tantalum and tantalum oxide films synthesized by pulse metal vacuum arc source deposition
NIM B Beam Interactions with Materials & Atoms
Nuclear Instruments and Methods in Physics Research B 242 (2006) 30–32 www.elsevier.com/locate/nimb
The biocompatibility of the tantalum and tantalum oxide films synthesized by pulse metal vacuum arc source deposition Y.X. Leng
a,b
, J.Y. Chen a, P. Yang a, H. Sun a, J. Wang a, N. Huang
a,b,*
a
b
School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, China Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China Available online 12 September 2005
Abstract The surface modification technique is extensively employed to improve and control biocompatibility for blood and cell attachment. In this paper, tantalum thin films were synthesized by pulsed metal vacuum arc source deposition, the tantalum oxide films were fabricated by tantalum films heated at 700 °C for 1 h in air. The films were characterized using X-ray diffraction (XRD). In vitro investigations of cultured human umbilical vein endothelial cells (HUVEC) on Ta, tantalum oxide films, 316L stainless steel and CP-Ti revealed that the growth and proliferation behavior of endothelial cells on the sample surfaces varied significantly. The adherence, growth, shape and proliferation of endothelial cells on tantalum and tantalum oxide films were much better than 316L stainless steel and CP-Ti. The Ta and tantalum oxide films shown to fulfill the requirements necessary for the application as a blood-contacting device (such as stent) coating. Ó 2005 Elsevier B.V. All rights reserved. PACS: 87.17; 81.15.EF Keywords: Tantalum; Tantalum oxide; Pulse metal vacuum arc source deposition; Human umbilical vein endothelial cells
1. Introduction Tantalum metal is known to be excellent in fracture toughness and workability. It also has better biocompatibility. Ta has already been used to make stents for endovascular surgery and may constitute a good alternative to the other materials because of its higher corrosion resistance and radio-opacity property, which may facilitate the follow-up of stent catheterization [1–5]. The tantalum metal surface existed a natural oxides (tantalum oxide), which play a key effect on biocompatibility of the tantalum metal [6]. In order to increase pitting corrosion resistance, Macionczyk et al. [7] synthesized a sandwich layer of tantalum and tantalum oxide on AISI 316L stainless, using a PVD * Corresponding author. Address: School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, China. Tel./fax: +86 28 87600625. E-mail address: [email protected] (N. Huang).
0168-583X/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2005.08.002
sputter process. While biocompatibility is obtained by tantalum oxide the ductility is achieved by the tantalum interface which at the same time ensures continued film adhesion, even after plastic deformation of the steel substrate. The blood compatibility of tantalum film is similar with low-temperature isotropic pyrolytic carbon (LTIC) that is currently the most widely accepted biomedical material for artificial heart valves [8]. This means it has better blood compatibility. 316L stainless and titanium have been popularly used to make stents. But lifelong persistence of these inorganic biomaterials within the arteries may contribute to restenosis. One factor in restenosis is vascular smooth muscle cell proliferation, which might be triggered by the stent-induced trauma to the vessel wall. And it is believed that covering the surface of the blood contacting materials (such as vascular stents and artificial heart valve) with endothelial cells (ECs) would increase the blood compatibility of the blood contacting materials. If the stent can be covered with ECs in vascular at few days, the re-endo-
Ta(820)
β-Ta2O5(-527)
Si β-Ta2O5(0411)
200
β-Ta2O5(174)
300
31
β-Ta2O5(-158) β-Ta2O5(215)
β-Ta2O5(040)
400
β-Ta2O5(046)
500
Intensity (Arb.)
thelialization and the vascular healing process are complete. The restenosis of the vascular is difficult to occur. So the new stent need to be fabricated, on which the human endothelial cells can adhere and proliferate. The surface modification technique is extensively employed to improve and control biocompatibility for blood and cell attachment. In order to improve the ECs adhere and proliferate on the 316L and Ti stents, tantalum thin films are synthesized by pulsed metal vacuum arc source deposition, the tantalum oxide films were fabricated by tantalum films heated at 700 °C for 1 h in air. We report the new investigation and results of an attempt to grow monolayers of human umbilical vein endothelial cells (HUVEC) without protein precoating on Ta and Ta–O film surface fabricated by plasma immersion ion implantation and deposition, heat oxidation.
β-Ta2O5(200) (006)
Y.X. Leng et al. / Nucl. Instr. and Meth. in Phys. Res. B 242 (2006) 30–32
Ta-O
100 Ta
Ta
0 20
30
40
50
60
70
80
90
2θ
2. Experimental Tantalum films were prepared on (1 0 0) silicon wafers using a plasma immersion ion implantation and deposition (PIII–D) system [9]. A Ta cathode, 14 mm in diameter, was mounted on the metal vacuum arc plasma source. Triggered by high-frequency voltages, Ta plasma was generated from the metal arc source and diffused into the deposition chamber. The detail deposition technical parameter of Ta metal arc source is similar with Ti that is detail in [9]. The as-deposited Ta films were oxide in air atmosphere at 700 °C for 60 min to synthesize tantalum oxide films. The structure of the films was characterized using X-ray diffraction (XRD, XÕPert Pro MPD). The biological behavior of endothelial cells on the tantalum, tantalum oxide films, 316L stainless steel and CP-Ti were studied by in vitro HUVEC culture investigation. The 316L stainless steel and CP-Ti were control sample. The HUVEC culture experimental detail was described in [10]. All the samples were subject to autoclaving at 120 °C for 1 h before seeding the endothelial cells. Sterilized samples were placed in the wells of a 6-well culture plate. The above complete medium 199 was seeded onto these samples surface at a drop of 1 ml. All EC incubations were at 37 °C in a humidified atmosphere containing 95% air and 5% CO2 for 24 h. The samples were subsequently rinsed with a 0.9% NaCl solution to remove weakly adherent endothelial cells. The adhered EC were fixed in 2% and 5% glutaraldehyde solution at room temperature for 2 and 12 h, respectively, then dehydrated and critical point-dried [11]. The specimens were then coated with a gold layer 10–20 nm thick and were examined by scanning electron microscopy to investigate morphology, accumulation and deformation of adherent endothelial cells. Twenty fields were chosen at random to obtain good statistics of the morphology. 3. Results The microstructure of the Ta and tantalum oxide films were showed as Fig. 1. It shows that the full width at
Fig. 1. The XRD patterns of the as-deposited tantalum film and tantalum oxide film synthesized by heat oxidation.
half-maximum (FWHM) of diffraction peaks in as-deposited Ta samples are quite wide and indicative of small grains. This means that the as-deposited Ta films were crystal and small grains when the films deposited at ambient temperature (<50 °C). Similar results were got in [12], in which the titanium dioxide were synthesized by pulse metal vacuum arc source deposition deposited at ambient temperature and the grain size less than 100 nm. The asdeposited Ta films were heated at 600 °C for 1 h in air to synthesize tantalum oxide films. The microstructure of tantalum oxide films also were showed as Fig. 1. It showed that the full width at half-maximum (FWHM) of diffraction peaks in heat oxidation Ta–O samples are thin than as-deposited Ta films. This means the grain size of b-Ta2O5 was bigger than the as-deposited Ta films. The SEM morphology and growth behavior of the adhered endothelial cells on the tantalum, tantalum oxide films, 316L stainless steel and CP-Ti are displayed in Fig. 2, which is from the random SEM field. After incubation in complete medium 199 for 24 h, the endothelial cell is of different biological behavior onto different surface. The endothelial cells on as-deposited Ta films and b-Ta2O5 form a perfect single layer, keep the natural original shape and display the typical cobblestone pattern, as seen in Fig. 2(a) and (b). In contrast, the endothelial cells on 316L and CP-Ti deformed, seldom cover the surface as shown in Fig. 2(c) and (d). A higher cell density on tantalum and tantalum oxide films as compared to CP-Ti and 316L was also observed. The results unequivocally indicate that the endothelial cells are significantly amicable with the Ta and tantalum oxide films materials. It further implies that Ta and tantalum oxide film is of good endothelialization property.
32
Y.X. Leng et al. / Nucl. Instr. and Meth. in Phys. Res. B 242 (2006) 30–32
Fig. 2. The SEM morphology of the adherent endothelial cells of the (a) tantalum oxide film, (b) Ta film, (c) 316L and (d) Ti (24 h).
4. Conclusions
References
Comparing with 316L and CP-Ti, the tantalum and tantalum oxide films synthesized by PIII–D and heat oxidation was presented in this paper giving a remarkable difference of the behavior of EC culture. The Ta and tantalum oxide films shown to fulfill the requirements necessary for the application as a blood-contacting device (such as stent) coating. According to our study, the tantalum and tantalum oxide films are helpful for seeding endothelial cells and can be used as a functional surface for the adherence and growth of EC. The promising in vitro results need conformation by in vivo studies. In conclusion, the present study indicates that the most interesting tested inorganic films surface for endothelial cells in terms of adhesion, viability and growth.
[1] H. Matsuno, A. Yokoyama, F. Watari, et al., Biomaterials 22 (2001) 1253. [2] R.A. Silva, M. Walls, B. Rondot, et al., J. Mater. Sci.: Mater. Med. 13 (2002) 495. [3] M. Unverdorben, A. Spielberger, M. Schywalsky, et al., Cardiovasc. Intervent. Radiol. 25 (2002) 127. [4] E.-P. Strecker, I. Boos, G. Schmid, D. Go¨ttmann, S. Vetter, Eur. Radiol. 10 (2000) 1144. [5] C.M.J.M. Pypen, H. Plenk Jr., M.F. Ebel, R. Svagera, J. Wernisch, J. Mater. Sci.: Mater. Med. 8 (1997) 781. [6] H. Zitter, H. Plenk Jr., J. Biomed. Mater. Res. 21 (1987) 881. [7] F. Macionczyk, B. Gerold, R. Thull, Surf. Coat. Technol. 142–144 (2001) 1084. [8] Y.X. Leng, H. Sun, P. Yang, J.Y. Chen, J. Wang, G.J. Wan, N. Huang, X.B. Tian, L.P. Wang, P.K. Chu, Thin Solid Films 398–399 (2001) 471. [9] Y.X. Leng, N. Huang, P. Yang, J.Y. Chen, H. Sun, J. Wang, G.J. Wan, Y. Leng, P.K. Chu, Thin Solid Films 420–421 (2002) 408. [10] J.Y. Chen, G.J. Wan, Y.X. Leng, P. Yang, H. Sun, J. Wang, N. Huang, Surf. Coat. Technol. 186 (2004) 270. [11] J.Y. Chen, Y.X. Leng, X.B. Tian, L.P. Wang, N. Huang, P.K. Chu, P. Yang, Biomaterials 23 (12) (2002) 2545. [12] Y.X. Leng, J.Y. Chen, H. Sun, P. Yang, G.J. Wan, J. Wang, N. Huang, Surf. Coat. Technol. 176 (2004) 141.
Acknowledgement This work was supported by National Natural Science Foundation of China Project No. 30400109#, 30300087# and NSFC-RGC30318006#.
Nuclear Instruments and Methods in Physics Research B 242 (2006) 30–32 www.elsevier.com/locate/nimb
The biocompatibility of the tantalum and tantalum oxide films synthesized by pulse metal vacuum arc source deposition Y.X. Leng
a,b
, J.Y. Chen a, P. Yang a, H. Sun a, J. Wang a, N. Huang
a,b,*
a
b
School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, China Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China Available online 12 September 2005
Abstract The surface modification technique is extensively employed to improve and control biocompatibility for blood and cell attachment. In this paper, tantalum thin films were synthesized by pulsed metal vacuum arc source deposition, the tantalum oxide films were fabricated by tantalum films heated at 700 °C for 1 h in air. The films were characterized using X-ray diffraction (XRD). In vitro investigations of cultured human umbilical vein endothelial cells (HUVEC) on Ta, tantalum oxide films, 316L stainless steel and CP-Ti revealed that the growth and proliferation behavior of endothelial cells on the sample surfaces varied significantly. The adherence, growth, shape and proliferation of endothelial cells on tantalum and tantalum oxide films were much better than 316L stainless steel and CP-Ti. The Ta and tantalum oxide films shown to fulfill the requirements necessary for the application as a blood-contacting device (such as stent) coating. Ó 2005 Elsevier B.V. All rights reserved. PACS: 87.17; 81.15.EF Keywords: Tantalum; Tantalum oxide; Pulse metal vacuum arc source deposition; Human umbilical vein endothelial cells
1. Introduction Tantalum metal is known to be excellent in fracture toughness and workability. It also has better biocompatibility. Ta has already been used to make stents for endovascular surgery and may constitute a good alternative to the other materials because of its higher corrosion resistance and radio-opacity property, which may facilitate the follow-up of stent catheterization [1–5]. The tantalum metal surface existed a natural oxides (tantalum oxide), which play a key effect on biocompatibility of the tantalum metal [6]. In order to increase pitting corrosion resistance, Macionczyk et al. [7] synthesized a sandwich layer of tantalum and tantalum oxide on AISI 316L stainless, using a PVD * Corresponding author. Address: School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, China. Tel./fax: +86 28 87600625. E-mail address: [email protected] (N. Huang).
0168-583X/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2005.08.002
sputter process. While biocompatibility is obtained by tantalum oxide the ductility is achieved by the tantalum interface which at the same time ensures continued film adhesion, even after plastic deformation of the steel substrate. The blood compatibility of tantalum film is similar with low-temperature isotropic pyrolytic carbon (LTIC) that is currently the most widely accepted biomedical material for artificial heart valves [8]. This means it has better blood compatibility. 316L stainless and titanium have been popularly used to make stents. But lifelong persistence of these inorganic biomaterials within the arteries may contribute to restenosis. One factor in restenosis is vascular smooth muscle cell proliferation, which might be triggered by the stent-induced trauma to the vessel wall. And it is believed that covering the surface of the blood contacting materials (such as vascular stents and artificial heart valve) with endothelial cells (ECs) would increase the blood compatibility of the blood contacting materials. If the stent can be covered with ECs in vascular at few days, the re-endo-
Ta(820)
β-Ta2O5(-527)
Si β-Ta2O5(0411)
200
β-Ta2O5(174)
300
31
β-Ta2O5(-158) β-Ta2O5(215)
β-Ta2O5(040)
400
β-Ta2O5(046)
500
Intensity (Arb.)
thelialization and the vascular healing process are complete. The restenosis of the vascular is difficult to occur. So the new stent need to be fabricated, on which the human endothelial cells can adhere and proliferate. The surface modification technique is extensively employed to improve and control biocompatibility for blood and cell attachment. In order to improve the ECs adhere and proliferate on the 316L and Ti stents, tantalum thin films are synthesized by pulsed metal vacuum arc source deposition, the tantalum oxide films were fabricated by tantalum films heated at 700 °C for 1 h in air. We report the new investigation and results of an attempt to grow monolayers of human umbilical vein endothelial cells (HUVEC) without protein precoating on Ta and Ta–O film surface fabricated by plasma immersion ion implantation and deposition, heat oxidation.
β-Ta2O5(200) (006)
Y.X. Leng et al. / Nucl. Instr. and Meth. in Phys. Res. B 242 (2006) 30–32
Ta-O
100 Ta
Ta
0 20
30
40
50
60
70
80
90
2θ
2. Experimental Tantalum films were prepared on (1 0 0) silicon wafers using a plasma immersion ion implantation and deposition (PIII–D) system [9]. A Ta cathode, 14 mm in diameter, was mounted on the metal vacuum arc plasma source. Triggered by high-frequency voltages, Ta plasma was generated from the metal arc source and diffused into the deposition chamber. The detail deposition technical parameter of Ta metal arc source is similar with Ti that is detail in [9]. The as-deposited Ta films were oxide in air atmosphere at 700 °C for 60 min to synthesize tantalum oxide films. The structure of the films was characterized using X-ray diffraction (XRD, XÕPert Pro MPD). The biological behavior of endothelial cells on the tantalum, tantalum oxide films, 316L stainless steel and CP-Ti were studied by in vitro HUVEC culture investigation. The 316L stainless steel and CP-Ti were control sample. The HUVEC culture experimental detail was described in [10]. All the samples were subject to autoclaving at 120 °C for 1 h before seeding the endothelial cells. Sterilized samples were placed in the wells of a 6-well culture plate. The above complete medium 199 was seeded onto these samples surface at a drop of 1 ml. All EC incubations were at 37 °C in a humidified atmosphere containing 95% air and 5% CO2 for 24 h. The samples were subsequently rinsed with a 0.9% NaCl solution to remove weakly adherent endothelial cells. The adhered EC were fixed in 2% and 5% glutaraldehyde solution at room temperature for 2 and 12 h, respectively, then dehydrated and critical point-dried [11]. The specimens were then coated with a gold layer 10–20 nm thick and were examined by scanning electron microscopy to investigate morphology, accumulation and deformation of adherent endothelial cells. Twenty fields were chosen at random to obtain good statistics of the morphology. 3. Results The microstructure of the Ta and tantalum oxide films were showed as Fig. 1. It shows that the full width at
Fig. 1. The XRD patterns of the as-deposited tantalum film and tantalum oxide film synthesized by heat oxidation.
half-maximum (FWHM) of diffraction peaks in as-deposited Ta samples are quite wide and indicative of small grains. This means that the as-deposited Ta films were crystal and small grains when the films deposited at ambient temperature (<50 °C). Similar results were got in [12], in which the titanium dioxide were synthesized by pulse metal vacuum arc source deposition deposited at ambient temperature and the grain size less than 100 nm. The asdeposited Ta films were heated at 600 °C for 1 h in air to synthesize tantalum oxide films. The microstructure of tantalum oxide films also were showed as Fig. 1. It showed that the full width at half-maximum (FWHM) of diffraction peaks in heat oxidation Ta–O samples are thin than as-deposited Ta films. This means the grain size of b-Ta2O5 was bigger than the as-deposited Ta films. The SEM morphology and growth behavior of the adhered endothelial cells on the tantalum, tantalum oxide films, 316L stainless steel and CP-Ti are displayed in Fig. 2, which is from the random SEM field. After incubation in complete medium 199 for 24 h, the endothelial cell is of different biological behavior onto different surface. The endothelial cells on as-deposited Ta films and b-Ta2O5 form a perfect single layer, keep the natural original shape and display the typical cobblestone pattern, as seen in Fig. 2(a) and (b). In contrast, the endothelial cells on 316L and CP-Ti deformed, seldom cover the surface as shown in Fig. 2(c) and (d). A higher cell density on tantalum and tantalum oxide films as compared to CP-Ti and 316L was also observed. The results unequivocally indicate that the endothelial cells are significantly amicable with the Ta and tantalum oxide films materials. It further implies that Ta and tantalum oxide film is of good endothelialization property.
32
Y.X. Leng et al. / Nucl. Instr. and Meth. in Phys. Res. B 242 (2006) 30–32
Fig. 2. The SEM morphology of the adherent endothelial cells of the (a) tantalum oxide film, (b) Ta film, (c) 316L and (d) Ti (24 h).
4. Conclusions
References
Comparing with 316L and CP-Ti, the tantalum and tantalum oxide films synthesized by PIII–D and heat oxidation was presented in this paper giving a remarkable difference of the behavior of EC culture. The Ta and tantalum oxide films shown to fulfill the requirements necessary for the application as a blood-contacting device (such as stent) coating. According to our study, the tantalum and tantalum oxide films are helpful for seeding endothelial cells and can be used as a functional surface for the adherence and growth of EC. The promising in vitro results need conformation by in vivo studies. In conclusion, the present study indicates that the most interesting tested inorganic films surface for endothelial cells in terms of adhesion, viability and growth.
[1] H. Matsuno, A. Yokoyama, F. Watari, et al., Biomaterials 22 (2001) 1253. [2] R.A. Silva, M. Walls, B. Rondot, et al., J. Mater. Sci.: Mater. Med. 13 (2002) 495. [3] M. Unverdorben, A. Spielberger, M. Schywalsky, et al., Cardiovasc. Intervent. Radiol. 25 (2002) 127. [4] E.-P. Strecker, I. Boos, G. Schmid, D. Go¨ttmann, S. Vetter, Eur. Radiol. 10 (2000) 1144. [5] C.M.J.M. Pypen, H. Plenk Jr., M.F. Ebel, R. Svagera, J. Wernisch, J. Mater. Sci.: Mater. Med. 8 (1997) 781. [6] H. Zitter, H. Plenk Jr., J. Biomed. Mater. Res. 21 (1987) 881. [7] F. Macionczyk, B. Gerold, R. Thull, Surf. Coat. Technol. 142–144 (2001) 1084. [8] Y.X. Leng, H. Sun, P. Yang, J.Y. Chen, J. Wang, G.J. Wan, N. Huang, X.B. Tian, L.P. Wang, P.K. Chu, Thin Solid Films 398–399 (2001) 471. [9] Y.X. Leng, N. Huang, P. Yang, J.Y. Chen, H. Sun, J. Wang, G.J. Wan, Y. Leng, P.K. Chu, Thin Solid Films 420–421 (2002) 408. [10] J.Y. Chen, G.J. Wan, Y.X. Leng, P. Yang, H. Sun, J. Wang, N. Huang, Surf. Coat. Technol. 186 (2004) 270. [11] J.Y. Chen, Y.X. Leng, X.B. Tian, L.P. Wang, N. Huang, P.K. Chu, P. Yang, Biomaterials 23 (12) (2002) 2545. [12] Y.X. Leng, J.Y. Chen, H. Sun, P. Yang, G.J. Wan, J. Wang, N. Huang, Surf. Coat. Technol. 176 (2004) 141.
Acknowledgement This work was supported by National Natural Science Foundation of China Project No. 30400109#, 30300087# and NSFC-RGC30318006#.