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Amir Abbas Zadpoor - One of the best experts on this subject based on the ideXlab platform.

  • Osteostatin-Coated Porous Titanium Can Improve Early Bone Regeneration of Cortical Bone Defects in Rats
    Tissue Engineering Part A, 2015
    Co-Authors: Johan Van Der Stok, Angela P. Bastidas Coral, Enrique Gómez-Barrena, Y. C. Chai, Saber Amin Yavari, Daniel Lozano, Amir Abbas Zadpoor, Pedro Esbrit, Jan A N Verhaar, Jan Schrooten, Holger Jahr, Harrie Weinans
    Abstract:

    A promising bone graft substitute is Porous Titanium. Porous Titanium, produced by selective laser melting (SLM), can be made as a completely open Porous and load-bearing scaffold that facilitates bone regeneration through osteoconduction. In this study, the bone regenerative capacity of Porous Titanium is improved with a coating of osteostatin, an osteoinductive peptide that consists of the 107-111 domain of the parathyroid hormone (PTH)-related protein (PTHrP), and the effects of this osteostatin coating on bone regeneration were evaluated in vitro and in vivo. SLM-produced Porous Titanium received an alkali-acid-heat treatment and was coated with osteostatin through soaking in a 100 nM solution for 24 h or left uncoated. Osteostatin-coated scaffolds contained ∼0.1 μg peptide/g Titanium, and in vitro 81% was released within 24 h. Human periosteum-derived osteoprogenitor cells cultured on osteostatin-coated scaffolds did not induce significant changes in osteogenic (alkaline phosphatase [ALP], collagen type 1 [Col1], osteocalcin [OCN], runt-related transcription factor 2 [Runx2]), or angiogenic (vascular endothelial growth factor [VEGF]) gene expression; however, it resulted in an upregulation of osteoprotegerin (OPG) gene expression after 24 h and a lower receptor activator of nuclear factor kappa-B ligand (RankL):OPG mRNA ratio. In vivo, osteostatin-coated, Porous Titanium implants increased bone regeneration in critical-sized cortical bone defects (p=0.005). Bone regeneration proceeded until 12 weeks, and femurs grafted with osteostatin-coated implants and uncoated implants recovered, respectively, 66% and 53% of the original femur torque strength (97±31 and 77±53 N·mm, not significant). In conclusion, the osteostatin coating improved bone regeneration of Porous Titanium. This effect was initiated after a short burst release and might be related to the observed in vitro upregulation of OPG gene expression by osteostatin in osteoprogenitor cells. Long-term beneficial effects of osteostatin-coated, Porous Titanium implants on bone regeneration or mechanical strength were not established here and may require optimization of the pace and dose of osteostatin release.

  • effects of bio functionalizing surface treatments on the mechanical behavior of open Porous Titanium biomaterials
    Journal of The Mechanical Behavior of Biomedical Materials, 2014
    Co-Authors: Amin S Yavari, A.c. Riemslag, J Van Der Stok, Harrie Weinans, Ruben Wauthle, S M Ahmadi, Jan Schrooten, M. Janssen, Amir Abbas Zadpoor
    Abstract:

    Abstract Bio-functionalizing surface treatments are often applied for improving the bioactivity of biomaterials that are based on otherwise bioinert Titanium alloys. When applied on highly Porous Titanium alloy structures intended for orthopedic bone regeneration purposes, such surface treatments could significantly change the static and fatigue properties of these structures and, thus, affect the application of the biomaterial as bone substitute. Therefore, the interplay between biofunctionalizing surface treatments and mechanical behavior needs to be controlled. In this paper, we studied the effects of two bio-functionalizing surface treatments, namely alkali–acid heat treatment (AlAcH) and acid–alkali (AcAl), on the static and fatigue properties of three different highly Porous Titanium alloy implants manufactured using selective laser melting. It was found that AlAcH treatment results in minimal mass loss. The static and fatigue properties of AlAcH specimens were therefore not much different from as-manufactured (AsM) specimens. In contrast, AcAl resulted in substantial mass loss and also in significantly less static and fatigue properties particularly for Porous structures with the highest porosity. The ratio of the static mechanical properties of AcAl specimens to that of AsM specimen was in the range of 1.5–6. The fatigue lives of AcAl specimens were much more severely affected by the applied surface treatments with fatigue lives up to 23 times smaller than that of AsM specimens particularly for the Porous structures with the highest porosity. In conclusion, the fatigue properties of surface treated Porous Titanium are dependent not only on the type of applied surface treatment but also on the porosity of the biomaterial.

  • bone regeneration performance of surface treated Porous Titanium
    Biomaterials, 2014
    Co-Authors: Saber Amin Yavari, Y. C. Chai, Johan Van Der Stok, Harrie Weinans, Ruben Wauthle, Jan Schrooten, Zeinab Tahmasebi Birgani, Pamela Habibovic, Michiel Mulier, Amir Abbas Zadpoor
    Abstract:

    The large surface area of highly Porous Titanium structures produced by additive manufacturing can be modified using biofunctionalizing surface treatments to improve the bone regeneration performance of these otherwise bioinert biomaterials. In this longitudinal study, we applied and compared three types of biofunctionalizing surface treatments, namely acid-alkali (AcAl), alkali-acid-heat treatment (AlAcH), and anodizing-heat treatment (AnH). The effects of treatments on apatite forming ability, cell attachment, cell proliferation, osteogenic gene expression, bone regeneration, biomechanical stability, and bone-biomaterial contact were evaluated using apatite forming ability test, cell culture assays, and animal experiments. It was found that AcAl and AnH work through completely different routes. While AcAl improved the apatite forming ability of as-manufactured (AsM) specimens, it did not have any positive effect on cell attachment, cell proliferation, and osteogenic gene expression. In contrast, AnH did not improve the apatite forming ability of AsM specimens but showed significantly better cell attachment, cell proliferation, and expression of osteogenic markers. The performance of AlAcH in terms of apatite forming ability and cell response was in between both extremes of AnH and AsM. AcAl resulted in significantly larger volumes of newly formed bone within the pores of the scaffold as compared to AnH. Interestingly, larger volumes of regenerated bone did not translate into improved biomechanical stability as AnH exhibited significantly better biomechanical stability as compared to AcAl suggesting that the beneficial effects of cell-nanotopography modulations somehow surpassed the benefits of improved apatite forming ability. In conclusion, the applied surface treatments have considerable effects on apatite forming ability, cell attachment, cell proliferation, and bone ingrowth of the studied biomaterials. The relationship between these properties and the bone-implant biomechanics is, however, not trivial.

  • crystal structure and nanotopographical features on the surface of heat treated and anodized Porous Titanium biomaterials produced using selective laser melting
    Applied Surface Science, 2014
    Co-Authors: Amin S Yavari, Harrie Weinans, Ruben Wauthle, Jan Schrooten, A J Bottger, Amir Abbas Zadpoor
    Abstract:

    Abstract Porous Titanium biomaterials manufactured using additive manufacturing techniques such as selective laser melting are considered promising materials for orthopedic applications where the biomaterial needs to mimic the properties of bone. Despite their appropriate mechanical properties and the ample pore space they provide for bone ingrowth and osseointegration, Porous Titanium structures have an intrinsically bioinert surface and need to be subjected to surface bio-functionalizing procedures to enhance their in vivo performance. In this study, we used a specific anodizing process to build a hierarchical oxide layer on the surface of Porous Titanium structures made by selective laser melting of Ti6Al4V ELI powder. The hierarchical structure included both nanotopographical features (nanotubes) and micro-features (micropits). After anodizing, the biomaterial was heat treated in Argon at different temperatures ranging between 400 and 600 °C for either 1 or 2 h to improve its bioactivity. The effects of applied heat treatment on the crystal structure of TiO2 nanotubes and the nanotopographical features of the surface were studied using scanning electron microscopy and X-ray diffraction. It was shown that the transition from the initial crystal structure, i.e. anatase, to rutile occurs between 500 and 600 °C and that after 2 h of heat treatment at 600 °C the crystal structure is predominantly rutile. The nanotopographical features of the surface were found to be largely unchanged for heat treatments carried out at 500 °C or below, whereas they were partially or largely disrupted after heat treatment at 600 °C. The possible implications of these findings for the bioactivity of Porous Titanium structures are discussed.

  • selective laser melting produced Porous Titanium scaffolds regenerate bone in critical size cortical bone defects
    Journal of Orthopaedic Research, 2013
    Co-Authors: Johan Van Der Stok, Jan A N Verhaar, Holger Jahr, Olav P Van Der Jagt, Saber Amin Yavari, Mirthe F P De Haas, J H Waarsing, Esther M M Van Lieshout, P Patka, Amir Abbas Zadpoor
    Abstract:

    Porous Titanium scaffolds have good mechanical properties that make them an interesting bone substitute material for large bone defects. These scaffolds can be produced with selective laser melting, which has the advantage of tailoring the structure's architecture. Reducing the strut size reduces the stiffness of the structure and may have a positive effect on bone formation. Two scaffolds with struts of 120-µm (Titanium-120) or 230-µm (Titanium-230) were studied in a load-bearing critical femoral bone defect in rats. The defect was stabilized with an internal plate and treated with Titanium-120, Titanium-230, or left empty. In vivo micro-CT scans at 4, 8, and 12 weeks showed more bone in the defects treated with scaffolds. Finally, 18.4 ± 7.1 mm3 (Titanium-120, p = 0.015) and 18.7 ± 8.0 mm3 (Titanium-230, p = 0.012) of bone was formed in those defects, significantly more than in the empty defects (5.8 ± 5.1 mm3). Bending tests on the excised femurs after 12 weeks showed that the fusion strength reached 62% (Titanium-120) and 45% (Titanium-230) of the intact contralateral femurs, but there was no significant difference between the two scaffolds. This study showed that in addition to adequate mechanical support, Porous Titanium scaffolds facilitate bone formation, which results in high mechanical integrity of the treated large bone defects. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 792–799, 2013

Harrie Weinans - One of the best experts on this subject based on the ideXlab platform.

  • Osteostatin-Coated Porous Titanium Can Improve Early Bone Regeneration of Cortical Bone Defects in Rats
    Tissue Engineering Part A, 2015
    Co-Authors: Johan Van Der Stok, Angela P. Bastidas Coral, Enrique Gómez-Barrena, Y. C. Chai, Saber Amin Yavari, Daniel Lozano, Amir Abbas Zadpoor, Pedro Esbrit, Jan A N Verhaar, Jan Schrooten, Holger Jahr, Harrie Weinans
    Abstract:

    A promising bone graft substitute is Porous Titanium. Porous Titanium, produced by selective laser melting (SLM), can be made as a completely open Porous and load-bearing scaffold that facilitates bone regeneration through osteoconduction. In this study, the bone regenerative capacity of Porous Titanium is improved with a coating of osteostatin, an osteoinductive peptide that consists of the 107-111 domain of the parathyroid hormone (PTH)-related protein (PTHrP), and the effects of this osteostatin coating on bone regeneration were evaluated in vitro and in vivo. SLM-produced Porous Titanium received an alkali-acid-heat treatment and was coated with osteostatin through soaking in a 100 nM solution for 24 h or left uncoated. Osteostatin-coated scaffolds contained ∼0.1 μg peptide/g Titanium, and in vitro 81% was released within 24 h. Human periosteum-derived osteoprogenitor cells cultured on osteostatin-coated scaffolds did not induce significant changes in osteogenic (alkaline phosphatase [ALP], collagen type 1 [Col1], osteocalcin [OCN], runt-related transcription factor 2 [Runx2]), or angiogenic (vascular endothelial growth factor [VEGF]) gene expression; however, it resulted in an upregulation of osteoprotegerin (OPG) gene expression after 24 h and a lower receptor activator of nuclear factor kappa-B ligand (RankL):OPG mRNA ratio. In vivo, osteostatin-coated, Porous Titanium implants increased bone regeneration in critical-sized cortical bone defects (p=0.005). Bone regeneration proceeded until 12 weeks, and femurs grafted with osteostatin-coated implants and uncoated implants recovered, respectively, 66% and 53% of the original femur torque strength (97±31 and 77±53 N·mm, not significant). In conclusion, the osteostatin coating improved bone regeneration of Porous Titanium. This effect was initiated after a short burst release and might be related to the observed in vitro upregulation of OPG gene expression by osteostatin in osteoprogenitor cells. Long-term beneficial effects of osteostatin-coated, Porous Titanium implants on bone regeneration or mechanical strength were not established here and may require optimization of the pace and dose of osteostatin release.

  • effects of bio functionalizing surface treatments on the mechanical behavior of open Porous Titanium biomaterials
    Journal of The Mechanical Behavior of Biomedical Materials, 2014
    Co-Authors: Amin S Yavari, A.c. Riemslag, J Van Der Stok, Harrie Weinans, Ruben Wauthle, S M Ahmadi, Jan Schrooten, M. Janssen, Amir Abbas Zadpoor
    Abstract:

    Abstract Bio-functionalizing surface treatments are often applied for improving the bioactivity of biomaterials that are based on otherwise bioinert Titanium alloys. When applied on highly Porous Titanium alloy structures intended for orthopedic bone regeneration purposes, such surface treatments could significantly change the static and fatigue properties of these structures and, thus, affect the application of the biomaterial as bone substitute. Therefore, the interplay between biofunctionalizing surface treatments and mechanical behavior needs to be controlled. In this paper, we studied the effects of two bio-functionalizing surface treatments, namely alkali–acid heat treatment (AlAcH) and acid–alkali (AcAl), on the static and fatigue properties of three different highly Porous Titanium alloy implants manufactured using selective laser melting. It was found that AlAcH treatment results in minimal mass loss. The static and fatigue properties of AlAcH specimens were therefore not much different from as-manufactured (AsM) specimens. In contrast, AcAl resulted in substantial mass loss and also in significantly less static and fatigue properties particularly for Porous structures with the highest porosity. The ratio of the static mechanical properties of AcAl specimens to that of AsM specimen was in the range of 1.5–6. The fatigue lives of AcAl specimens were much more severely affected by the applied surface treatments with fatigue lives up to 23 times smaller than that of AsM specimens particularly for the Porous structures with the highest porosity. In conclusion, the fatigue properties of surface treated Porous Titanium are dependent not only on the type of applied surface treatment but also on the porosity of the biomaterial.

  • bone regeneration performance of surface treated Porous Titanium
    Biomaterials, 2014
    Co-Authors: Saber Amin Yavari, Y. C. Chai, Johan Van Der Stok, Harrie Weinans, Ruben Wauthle, Jan Schrooten, Zeinab Tahmasebi Birgani, Pamela Habibovic, Michiel Mulier, Amir Abbas Zadpoor
    Abstract:

    The large surface area of highly Porous Titanium structures produced by additive manufacturing can be modified using biofunctionalizing surface treatments to improve the bone regeneration performance of these otherwise bioinert biomaterials. In this longitudinal study, we applied and compared three types of biofunctionalizing surface treatments, namely acid-alkali (AcAl), alkali-acid-heat treatment (AlAcH), and anodizing-heat treatment (AnH). The effects of treatments on apatite forming ability, cell attachment, cell proliferation, osteogenic gene expression, bone regeneration, biomechanical stability, and bone-biomaterial contact were evaluated using apatite forming ability test, cell culture assays, and animal experiments. It was found that AcAl and AnH work through completely different routes. While AcAl improved the apatite forming ability of as-manufactured (AsM) specimens, it did not have any positive effect on cell attachment, cell proliferation, and osteogenic gene expression. In contrast, AnH did not improve the apatite forming ability of AsM specimens but showed significantly better cell attachment, cell proliferation, and expression of osteogenic markers. The performance of AlAcH in terms of apatite forming ability and cell response was in between both extremes of AnH and AsM. AcAl resulted in significantly larger volumes of newly formed bone within the pores of the scaffold as compared to AnH. Interestingly, larger volumes of regenerated bone did not translate into improved biomechanical stability as AnH exhibited significantly better biomechanical stability as compared to AcAl suggesting that the beneficial effects of cell-nanotopography modulations somehow surpassed the benefits of improved apatite forming ability. In conclusion, the applied surface treatments have considerable effects on apatite forming ability, cell attachment, cell proliferation, and bone ingrowth of the studied biomaterials. The relationship between these properties and the bone-implant biomechanics is, however, not trivial.

  • crystal structure and nanotopographical features on the surface of heat treated and anodized Porous Titanium biomaterials produced using selective laser melting
    Applied Surface Science, 2014
    Co-Authors: Amin S Yavari, Harrie Weinans, Ruben Wauthle, Jan Schrooten, A J Bottger, Amir Abbas Zadpoor
    Abstract:

    Abstract Porous Titanium biomaterials manufactured using additive manufacturing techniques such as selective laser melting are considered promising materials for orthopedic applications where the biomaterial needs to mimic the properties of bone. Despite their appropriate mechanical properties and the ample pore space they provide for bone ingrowth and osseointegration, Porous Titanium structures have an intrinsically bioinert surface and need to be subjected to surface bio-functionalizing procedures to enhance their in vivo performance. In this study, we used a specific anodizing process to build a hierarchical oxide layer on the surface of Porous Titanium structures made by selective laser melting of Ti6Al4V ELI powder. The hierarchical structure included both nanotopographical features (nanotubes) and micro-features (micropits). After anodizing, the biomaterial was heat treated in Argon at different temperatures ranging between 400 and 600 °C for either 1 or 2 h to improve its bioactivity. The effects of applied heat treatment on the crystal structure of TiO2 nanotubes and the nanotopographical features of the surface were studied using scanning electron microscopy and X-ray diffraction. It was shown that the transition from the initial crystal structure, i.e. anatase, to rutile occurs between 500 and 600 °C and that after 2 h of heat treatment at 600 °C the crystal structure is predominantly rutile. The nanotopographical features of the surface were found to be largely unchanged for heat treatments carried out at 500 °C or below, whereas they were partially or largely disrupted after heat treatment at 600 °C. The possible implications of these findings for the bioactivity of Porous Titanium structures are discussed.

Xingdong Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Bionic design and 3D printing of Porous Titanium alloy scaffolds for bone tissue repair
    Composites Part B-engineering, 2019
    Co-Authors: Li Zhao, Xuan Pei, Jianxun Sun, Yujiang Fan, Changchun Zhou, Cheng Hu, Fei Xing, Lihua Jiang, Xingdong Zhang
    Abstract:

    Abstract Bone defect and osteoporosis are common in clinic which are seriously harmful for public health. Bionic bone tissue engineering scaffolds are very important for bone tissue repair and reconstruction. In this study, different bionic bone tissue engineering scaffolds were constructed by computer-aided design and fabricated by selected laser melting. Novel Porous structures were designed by using parameterization modeling. The accurate models with key characteristics such as porosity and the mechanical property of scaffolds were studied. Compared with the designed model, the error of the selective laser melting (SLM) printed scaffold porosity was less than 2.73%. The mechanical properties of the prepared scaffold can be calculated by finite element analysis of 3D models, and the mechanical properties of the 3D printed samples were consistent with the model design. Through the design, manufacture, characterization and evaluation of the scaffold Porous structures, the parametric modeling of Porous Titanium bone tissue engineering scaffold with good mechanical and biological properties was realized. Optimized design and precisely manufactured implants are very important for bone tissue repair and reconstruction.

  • an improved polymeric sponge replication method for biomedical Porous Titanium scaffolds
    Materials Science and Engineering: C, 2017
    Co-Authors: Chunli Wang, Zhanwen Xiao, Hongjie Chen, Xiangdong Zhu, Kai Zhang, Xingdong Zhang
    Abstract:

    Biomedical Porous Titanium (Ti) scaffolds were fabricated by an improved polymeric sponge replication method. The unique formulations and distinct processing techniques, i.e. a mixture of water and ethanol as solvent, multiple coatings with different viscosities of the Ti slurries and centrifugation for removing the extra slurries were used in the present study. The optimized Porous Ti scaffolds had uniform Porous structure and completely interconnected macropores (~365.1μm). In addition, two different sizes of micropores (~45.4 and ~6.2μm) were also formed in the skeleton of the scaffold. The addition of ethanol to the Ti slurry increased the compressive strength of the scaffold by improving the compactness of the skeleton. A compressive strength of 83.6±4.0MPa was achieved for a Porous Ti scaffold with a porosity of 66.4±1.8%. Our cellular study also revealed that the scaffolds could support the growth and proliferation of mesenchymal stem cells (MSCs).

  • fabrication of Porous Titanium scaffolds by stack sintering of microPorous Titanium spheres produced with centrifugal granulation technology
    Materials Science and Engineering: C, 2014
    Co-Authors: Hongjie Chen, Yujiang Fan, Chunli Wang, Xiangdong Zhu, Kai Zhang, Xingdong Zhang
    Abstract:

    Abstract Microporosity plays a key role in bioactivity and osteoinductivity of a biomaterial scaffold. A simple new approach to fabricating load-bearing Porous Titanium (Ti) scaffolds with uniform Porous structure, highly controllable pore size and excellent biocompatibility was developed in the present study. This method was based on stack sintering of microPorous Ti spheres produced with centrifugal granulation of commercial Ti powders. Macropores (180.0–341.8 μm) and micropores (6.1–11.8 μm) of the scaffolds were dependent on the sizes of the Ti spheres and the Ti powders, respectively. The compressive strength of the scaffolds (83.4–108.9 MPa) was high enough for the repair of load-bearing bone defects. Besides, the abundant micropores occurred on the rough and convex surface of the Ti spheres in the scaffolds were more favorable for adsorption of serum proteins, and thus promoted the growth of mesenchymal stem cells (MSCs).

  • osteoinduction of Porous Titanium a comparative study between acid alkali and chemical thermal treatments
    Journal of Biomedical Materials Research Part B, 2010
    Co-Authors: Chaoyong Zhao, Kailu Liang, Jietao Ding, Zhou Xiang, Xingdong Zhang
    Abstract:

    In this study, a slurry foaming method was developed to fabricate Porous Titanium, and two different surface treatments were applied to investigate their effects on the osteoinduction of the implants. Three types of implants, that was Porous Titanium with no treatment, with chemical-thermal treatment (CTPT), and with acid-alkali treatment (AAPT), were implanted in the dorsal muscles of adult dogs for 3 and 5 months. After implantation for 3 months, new bone was only found in the inner pores of AAPT by histological analysis and field emission scanning electron microscopy observation. After implantation for 5 months, new bone was also found in CTPT, but it was absent in AAPT. This study not only confirmed that Porous Titanium with appropriate surface treatments could possess osteoinduction but also showed that its osteoinductive potential was tightly related to the surface treatment. As a simpler method, acid-alkali treatment could endow Porous Titanium with faster osteoinduction, and AAPT might have potential in clinical application. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010.

  • Porous Titanium coating with sub-micro structure from anodic oxidation
    2010 3rd International Nanoelectronics Conference (INEC), 2010
    Co-Authors: Qingshan Fu, Zhanwen Xiao, Xingdong Zhang
    Abstract:

    How to improve the bioactivity of Titanium is always the key factor in the application of Titanium artificial implants. Among kinds of means to reinforce its bioactivity, deposition of bioactive layers on Titanium substrates and anodic oxidation are two common and powerful means. In this study, we combined the two methods to construct a more bioactive Titanium surface. Plasma spraying processed for macro pores formation on the Titanium substrates and followed by anodic oxidation to prepare a layer of Porous sub-micro Titanium oxidation. The bioactivity of the samples was evaluated in vitro by soaking in simulated body fluid (SBF) solution. The results revealed that Porous Titanium coatings with anodic oxidation showed a sub-micro pore structure and showed better bioactivity.

Jan Schrooten - One of the best experts on this subject based on the ideXlab platform.

  • Osteostatin-Coated Porous Titanium Can Improve Early Bone Regeneration of Cortical Bone Defects in Rats
    Tissue Engineering Part A, 2015
    Co-Authors: Johan Van Der Stok, Angela P. Bastidas Coral, Enrique Gómez-Barrena, Y. C. Chai, Saber Amin Yavari, Daniel Lozano, Amir Abbas Zadpoor, Pedro Esbrit, Jan A N Verhaar, Jan Schrooten, Holger Jahr, Harrie Weinans
    Abstract:

    A promising bone graft substitute is Porous Titanium. Porous Titanium, produced by selective laser melting (SLM), can be made as a completely open Porous and load-bearing scaffold that facilitates bone regeneration through osteoconduction. In this study, the bone regenerative capacity of Porous Titanium is improved with a coating of osteostatin, an osteoinductive peptide that consists of the 107-111 domain of the parathyroid hormone (PTH)-related protein (PTHrP), and the effects of this osteostatin coating on bone regeneration were evaluated in vitro and in vivo. SLM-produced Porous Titanium received an alkali-acid-heat treatment and was coated with osteostatin through soaking in a 100 nM solution for 24 h or left uncoated. Osteostatin-coated scaffolds contained ∼0.1 μg peptide/g Titanium, and in vitro 81% was released within 24 h. Human periosteum-derived osteoprogenitor cells cultured on osteostatin-coated scaffolds did not induce significant changes in osteogenic (alkaline phosphatase [ALP], collagen type 1 [Col1], osteocalcin [OCN], runt-related transcription factor 2 [Runx2]), or angiogenic (vascular endothelial growth factor [VEGF]) gene expression; however, it resulted in an upregulation of osteoprotegerin (OPG) gene expression after 24 h and a lower receptor activator of nuclear factor kappa-B ligand (RankL):OPG mRNA ratio. In vivo, osteostatin-coated, Porous Titanium implants increased bone regeneration in critical-sized cortical bone defects (p=0.005). Bone regeneration proceeded until 12 weeks, and femurs grafted with osteostatin-coated implants and uncoated implants recovered, respectively, 66% and 53% of the original femur torque strength (97±31 and 77±53 N·mm, not significant). In conclusion, the osteostatin coating improved bone regeneration of Porous Titanium. This effect was initiated after a short burst release and might be related to the observed in vitro upregulation of OPG gene expression by osteostatin in osteoprogenitor cells. Long-term beneficial effects of osteostatin-coated, Porous Titanium implants on bone regeneration or mechanical strength were not established here and may require optimization of the pace and dose of osteostatin release.

  • effects of bio functionalizing surface treatments on the mechanical behavior of open Porous Titanium biomaterials
    Journal of The Mechanical Behavior of Biomedical Materials, 2014
    Co-Authors: Amin S Yavari, A.c. Riemslag, J Van Der Stok, Harrie Weinans, Ruben Wauthle, S M Ahmadi, Jan Schrooten, M. Janssen, Amir Abbas Zadpoor
    Abstract:

    Abstract Bio-functionalizing surface treatments are often applied for improving the bioactivity of biomaterials that are based on otherwise bioinert Titanium alloys. When applied on highly Porous Titanium alloy structures intended for orthopedic bone regeneration purposes, such surface treatments could significantly change the static and fatigue properties of these structures and, thus, affect the application of the biomaterial as bone substitute. Therefore, the interplay between biofunctionalizing surface treatments and mechanical behavior needs to be controlled. In this paper, we studied the effects of two bio-functionalizing surface treatments, namely alkali–acid heat treatment (AlAcH) and acid–alkali (AcAl), on the static and fatigue properties of three different highly Porous Titanium alloy implants manufactured using selective laser melting. It was found that AlAcH treatment results in minimal mass loss. The static and fatigue properties of AlAcH specimens were therefore not much different from as-manufactured (AsM) specimens. In contrast, AcAl resulted in substantial mass loss and also in significantly less static and fatigue properties particularly for Porous structures with the highest porosity. The ratio of the static mechanical properties of AcAl specimens to that of AsM specimen was in the range of 1.5–6. The fatigue lives of AcAl specimens were much more severely affected by the applied surface treatments with fatigue lives up to 23 times smaller than that of AsM specimens particularly for the Porous structures with the highest porosity. In conclusion, the fatigue properties of surface treated Porous Titanium are dependent not only on the type of applied surface treatment but also on the porosity of the biomaterial.

  • bone regeneration performance of surface treated Porous Titanium
    Biomaterials, 2014
    Co-Authors: Saber Amin Yavari, Y. C. Chai, Johan Van Der Stok, Harrie Weinans, Ruben Wauthle, Jan Schrooten, Zeinab Tahmasebi Birgani, Pamela Habibovic, Michiel Mulier, Amir Abbas Zadpoor
    Abstract:

    The large surface area of highly Porous Titanium structures produced by additive manufacturing can be modified using biofunctionalizing surface treatments to improve the bone regeneration performance of these otherwise bioinert biomaterials. In this longitudinal study, we applied and compared three types of biofunctionalizing surface treatments, namely acid-alkali (AcAl), alkali-acid-heat treatment (AlAcH), and anodizing-heat treatment (AnH). The effects of treatments on apatite forming ability, cell attachment, cell proliferation, osteogenic gene expression, bone regeneration, biomechanical stability, and bone-biomaterial contact were evaluated using apatite forming ability test, cell culture assays, and animal experiments. It was found that AcAl and AnH work through completely different routes. While AcAl improved the apatite forming ability of as-manufactured (AsM) specimens, it did not have any positive effect on cell attachment, cell proliferation, and osteogenic gene expression. In contrast, AnH did not improve the apatite forming ability of AsM specimens but showed significantly better cell attachment, cell proliferation, and expression of osteogenic markers. The performance of AlAcH in terms of apatite forming ability and cell response was in between both extremes of AnH and AsM. AcAl resulted in significantly larger volumes of newly formed bone within the pores of the scaffold as compared to AnH. Interestingly, larger volumes of regenerated bone did not translate into improved biomechanical stability as AnH exhibited significantly better biomechanical stability as compared to AcAl suggesting that the beneficial effects of cell-nanotopography modulations somehow surpassed the benefits of improved apatite forming ability. In conclusion, the applied surface treatments have considerable effects on apatite forming ability, cell attachment, cell proliferation, and bone ingrowth of the studied biomaterials. The relationship between these properties and the bone-implant biomechanics is, however, not trivial.

  • crystal structure and nanotopographical features on the surface of heat treated and anodized Porous Titanium biomaterials produced using selective laser melting
    Applied Surface Science, 2014
    Co-Authors: Amin S Yavari, Harrie Weinans, Ruben Wauthle, Jan Schrooten, A J Bottger, Amir Abbas Zadpoor
    Abstract:

    Abstract Porous Titanium biomaterials manufactured using additive manufacturing techniques such as selective laser melting are considered promising materials for orthopedic applications where the biomaterial needs to mimic the properties of bone. Despite their appropriate mechanical properties and the ample pore space they provide for bone ingrowth and osseointegration, Porous Titanium structures have an intrinsically bioinert surface and need to be subjected to surface bio-functionalizing procedures to enhance their in vivo performance. In this study, we used a specific anodizing process to build a hierarchical oxide layer on the surface of Porous Titanium structures made by selective laser melting of Ti6Al4V ELI powder. The hierarchical structure included both nanotopographical features (nanotubes) and micro-features (micropits). After anodizing, the biomaterial was heat treated in Argon at different temperatures ranging between 400 and 600 °C for either 1 or 2 h to improve its bioactivity. The effects of applied heat treatment on the crystal structure of TiO2 nanotubes and the nanotopographical features of the surface were studied using scanning electron microscopy and X-ray diffraction. It was shown that the transition from the initial crystal structure, i.e. anatase, to rutile occurs between 500 and 600 °C and that after 2 h of heat treatment at 600 °C the crystal structure is predominantly rutile. The nanotopographical features of the surface were found to be largely unchanged for heat treatments carried out at 500 °C or below, whereas they were partially or largely disrupted after heat treatment at 600 °C. The possible implications of these findings for the bioactivity of Porous Titanium structures are discussed.

Amin S Yavari - One of the best experts on this subject based on the ideXlab platform.

  • effects of bio functionalizing surface treatments on the mechanical behavior of open Porous Titanium biomaterials
    Journal of The Mechanical Behavior of Biomedical Materials, 2014
    Co-Authors: Amin S Yavari, A.c. Riemslag, J Van Der Stok, Harrie Weinans, Ruben Wauthle, S M Ahmadi, Jan Schrooten, M. Janssen, Amir Abbas Zadpoor
    Abstract:

    Abstract Bio-functionalizing surface treatments are often applied for improving the bioactivity of biomaterials that are based on otherwise bioinert Titanium alloys. When applied on highly Porous Titanium alloy structures intended for orthopedic bone regeneration purposes, such surface treatments could significantly change the static and fatigue properties of these structures and, thus, affect the application of the biomaterial as bone substitute. Therefore, the interplay between biofunctionalizing surface treatments and mechanical behavior needs to be controlled. In this paper, we studied the effects of two bio-functionalizing surface treatments, namely alkali–acid heat treatment (AlAcH) and acid–alkali (AcAl), on the static and fatigue properties of three different highly Porous Titanium alloy implants manufactured using selective laser melting. It was found that AlAcH treatment results in minimal mass loss. The static and fatigue properties of AlAcH specimens were therefore not much different from as-manufactured (AsM) specimens. In contrast, AcAl resulted in substantial mass loss and also in significantly less static and fatigue properties particularly for Porous structures with the highest porosity. The ratio of the static mechanical properties of AcAl specimens to that of AsM specimen was in the range of 1.5–6. The fatigue lives of AcAl specimens were much more severely affected by the applied surface treatments with fatigue lives up to 23 times smaller than that of AsM specimens particularly for the Porous structures with the highest porosity. In conclusion, the fatigue properties of surface treated Porous Titanium are dependent not only on the type of applied surface treatment but also on the porosity of the biomaterial.

  • crystal structure and nanotopographical features on the surface of heat treated and anodized Porous Titanium biomaterials produced using selective laser melting
    Applied Surface Science, 2014
    Co-Authors: Amin S Yavari, Harrie Weinans, Ruben Wauthle, Jan Schrooten, A J Bottger, Amir Abbas Zadpoor
    Abstract:

    Abstract Porous Titanium biomaterials manufactured using additive manufacturing techniques such as selective laser melting are considered promising materials for orthopedic applications where the biomaterial needs to mimic the properties of bone. Despite their appropriate mechanical properties and the ample pore space they provide for bone ingrowth and osseointegration, Porous Titanium structures have an intrinsically bioinert surface and need to be subjected to surface bio-functionalizing procedures to enhance their in vivo performance. In this study, we used a specific anodizing process to build a hierarchical oxide layer on the surface of Porous Titanium structures made by selective laser melting of Ti6Al4V ELI powder. The hierarchical structure included both nanotopographical features (nanotubes) and micro-features (micropits). After anodizing, the biomaterial was heat treated in Argon at different temperatures ranging between 400 and 600 °C for either 1 or 2 h to improve its bioactivity. The effects of applied heat treatment on the crystal structure of TiO2 nanotubes and the nanotopographical features of the surface were studied using scanning electron microscopy and X-ray diffraction. It was shown that the transition from the initial crystal structure, i.e. anatase, to rutile occurs between 500 and 600 °C and that after 2 h of heat treatment at 600 °C the crystal structure is predominantly rutile. The nanotopographical features of the surface were found to be largely unchanged for heat treatments carried out at 500 °C or below, whereas they were partially or largely disrupted after heat treatment at 600 °C. The possible implications of these findings for the bioactivity of Porous Titanium structures are discussed.

  • selective laser melting produced Porous Titanium scaffolds regenerate bone in critical size cortical bone defects
    Surgery and Traumatology, 2013
    Co-Authors: J Van Destok, Jan A N Verhaar, Amin S Yavari, Holger Jahr, J H Waarsing, P Patka, O P Van Dejagt, M F P Dehaas, E M M Vanlieshout, Amir Abbas Zadpoor
    Abstract:

    textabstractPorous Titanium scaffolds have good mechanical properties that make them an interesting bone substitute material for large bone defects. These scaffolds can be produced with selective laser melting, which has the advantage of tailoring the structure's architecture. Reducing the strut size reduces the stiffness of the structure and may have a positive effect on bone formation. Two scaffolds with struts of 120-μm (Titanium-120) or 230-μm (Titanium-230) were studied in a load-bearing critical femoral bone defect in rats. The defect was stabilized with an internal plate and treated with Titanium-120, Titanium-230, or left empty. In vivo micro-CT scans at 4, 8, and 12 weeks showed more bone in the defects treated with scaffolds. Finally, 18.4 ± 7.1 mm3(Titanium-120, p = 0.015) and 18.7 ± 8.0 mm3(Titanium-230, p = 0.012) of bone was formed in those defects, significantly more than in the empty defects (5.8 ± 5.1 mm3). Bending tests on the excised femurs after 12 weeks showed that the fusion strength reached 62% (Titanium-120) and 45% (Titanium-230) of the intact contralateral femurs, but there was no significant difference between the two scaffolds. This study showed that in addition to adequate mechanical support, Porous Titanium scaffolds facilitate bone formation, which results in high mechanical integrity of the treated large bone defects. Copyright