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Wang Z, Lee WJ, Koh BTH, Hong M, Wang W, Lim PN, Feng J, Park LS, Kim M, Thian ES. Functional regeneration of tendons using scaffolds with physical anisotropy engineered via microarchitectural manipulation. Sci Adv 2018; 4:eaat4537. [PMID: 30345353 PMCID: PMC6195336 DOI: 10.1126/sciadv.aat4537] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 09/07/2018] [Indexed: 05/22/2023]
Abstract
Structural and hierarchical anisotropy underlies the structure-function relationship of most living tissues. Attempts to exploit the interplay between cells and their immediate environment have rarely featured macroscale, three-dimensional constructs required for clinical applications. Furthermore, compromises to biomechanical robustness during fabrication often limit the scaffold's relevance in translational medicine. We report a polymeric three-dimensional scaffold with tendon-like mechanical properties and controlled anisotropic microstructures. The scaffold was composed of two distinct portions, which enabled high porosity while retaining tendon-like mechanical properties. When tenocytes were cultured in vitro on the scaffold, phenotypic markers of tenogenesis such as type-I collagen, decorin, and tenascin were significantly expressed over nonanisotropic controls. Moreover, highly aligned intracellular cytoskeletal network and high nuclear alignment efficiencies were observed, suggesting that microstructural anisotropy might play the epigenetic role of mechanotransduction. When implanted in an in vivo micropig model, a neotissue that formed over the scaffold resembled native tendon tissue in composition and structure.
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Affiliation(s)
- Z. Wang
- Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117 576, Singapore
- College of Materials Science and Engineering, Hunan University, Changsha 410082, P.R. China
| | - W. J. Lee
- Prestige BioResearch Pte Ltd, 15 Tech Park Crescent, Singapore 638117, Singapore
- College of Veterinary Medicine, Kyungpook National University, Daegu 41566, Republic of Korea
| | - B. T. H. Koh
- Department of Orthopaedic Surgery, National University of Singapore, 5 Lower Kent Ridge Road, Singapore 119 074, Singapore
| | - M. Hong
- Department of Electrical and Computer Engineering, National University of Singapore, 2 Engineering Drive 3, Singapore 117576, Singapore
| | - W. Wang
- Department of Orthopaedic Surgery, National University of Singapore, 5 Lower Kent Ridge Road, Singapore 119 074, Singapore
| | - P. N. Lim
- Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117 576, Singapore
| | - J. Feng
- Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117 576, Singapore
| | - L. S. Park
- Prestige BioResearch Pte Ltd, 15 Tech Park Crescent, Singapore 638117, Singapore
| | - M. Kim
- Prestige BioResearch Pte Ltd, 15 Tech Park Crescent, Singapore 638117, Singapore
| | - E. S. Thian
- Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117 576, Singapore
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Lim PN, Chang L, Tay BY, Guneta V, Choong C, Ho B, Thian ES. Proposed mechanism of antibacterial action of chemically modified apatite for reduced bone infection. ACS Appl Mater Interfaces 2014; 6:17082-17092. [PMID: 25198775 DOI: 10.1021/am504716g] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Surface-bound silver ions were demonstrated to be responsible for the antibacterial action of silver, silicon-containing hydroxyapatite (Ag,Si-HA). X-ray photoelectron spectroscopy, transmission electron microscopy, and induced coupled plasma spectroscopy results suggested that silver ions in the crystal structure diffused toward the crystal surface of Ag,Si-HA, and interacted with adherent Staphylococcus aureus bacteria, thus damaging the cell wall and inducing leakage of potassium ions. All these steps constitute the mechanism of antibacterial action for Ag,Si-HA. Consequently, Ag,Si-HA gave rise to a 7-log reduction of the adherent bacteria as compared to HA and Si-HA at 168 h. Silicon in Ag,Si-HA helped to mitigate the reduced effect of bone differentiation in Ag-HA as shown in the alkaline phosphatase, type I collagen and osteocalcin results, promoting enhanced biological response, without compromising the antibacterial property. On the whole, Ag,Si-HA containing an optimized content of 0.5 wt % silver and 0.7 wt % silicon provides antibacterial properties and enhanced biological response.
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Affiliation(s)
- P N Lim
- Department of Mechanical Engineering, National University of Singapore , 9 Engineering Drive 1, Singapore 117 576, Singapore
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Thian ES, Konishi T, Kawanobe Y, Lim PN, Choong C, Ho B, Aizawa M. Zinc-substituted hydroxyapatite: a biomaterial with enhanced bioactivity and antibacterial properties. J Mater Sci Mater Med 2013; 24:437-445. [PMID: 23160913 DOI: 10.1007/s10856-012-4817-x] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2012] [Accepted: 11/08/2012] [Indexed: 05/28/2023]
Abstract
Hydroxyapatite (HA) is a synthetic biomaterial and has been found to promote new bone formation when implanted in a bone defect site. However, its use is often limited due to its slow osteointegration rate and low antibacterial activity, particularly where HA has to be used for long term biomedical applications. This work will describe the synthesis and detailed characterization of zinc-substituted HA (ZnHA) as an alternative biomaterial to HA. ZnHA containing 1.6 wt% Zn was synthesized via a co-precipitation reaction between calcium hydroxide, orthophosphoric acid and zinc nitrate hexahydrate. Single-phase ZnHA particles with a rod-like morphology measuring ~50 nm in length and ~15 nm in width, were obtained and characterized using transmission electron microscopy and X-ray diffraction. The substitution of Zn into HA resulted in a decrease in both the a- and c-axes of the unit cell parameters, thereby causing the HA crystal structure to alter. In vitro cell culture work showed that ZnHA possessed enhanced bioactivity since an increase in the growth of human adipose-derived mesenchymal stem cells along with the bone cell differentiation markers, were observed. In addition, antibacterial work demonstrated that ZnHA exhibited antimicrobial capability since there was a significant decrease in the number of viable Staphylococcus aureus bacteria after in contact with ZnHA.
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Affiliation(s)
- E S Thian
- Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117 576, Singapore.
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Thian ES, Huang J, Ahmad Z, Edirisinghe MJ, Jayasinghe SN, Ireland DC, Brooks RA, Rushton N, Best SM, Bonfield W. Influence of nanohydroxyapatite patterns deposited by electrohydrodynamic spraying on osteoblast response. J Biomed Mater Res A 2008; 85:188-94. [PMID: 17688271 DOI: 10.1002/jbm.a.31564] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Electrohydrodynamic spraying has been used to produce patterns of line width up to 100 microm in size on glass discs, using nanohydroxyapatite (nHA). A human osteoblast (HOB)-like cell model was then used to study the interaction between the HOB cells and nHA patterns in vitro. Growth of the cells was significantly increased (p < 0.05) on the nHA surfaces. In addition, HOBs attached and spread well, secreting extracellular matrix. It was found that a confluent, aligned cell layer was achieved on nHA patterns by day 9. Immunofluorescent staining indicated that these cells showed elongated nuclei, enhanced adhesion (vinculin adhesion plaques) and a well-aligned cytoskeleton (actin stress fibres). This work suggests that this type of spraying may provide a route for the production of nanoscale features on implants for biomedical applications.
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Affiliation(s)
- E S Thian
- Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, UK.
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Thian ES, Ahmad Z, Huang J, Edirisinghe MJ, Jayasinghe SN, Ireland DC, Brooks RA, Rushton N, Bonfield W, Best SM. Bioactivity of Nanoapatite Produced by Electrohydrodynamic Atomization. ACTA ACUST UNITED AC 2007. [DOI: 10.1166/jbns.2007.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Thian ES, Huang J, Best SM, Barber ZH, Bonfield W. Silicon-substituted hydroxyapatite thin films: Effect of annealing temperature on coating stability and bioactivity. J Biomed Mater Res A 2006; 78:121-8. [PMID: 16604532 DOI: 10.1002/jbm.a.30730] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The effect of annealing temperature on the physicochemical and biological characteristics of magnetron cosputtered silicon-substituted hydroxyapatite (SiHA) thin coatings was studied. Annealing is required to transform as-sputtered amorphous films into crystalline coatings. A nanocrystalline, single-phase apatite structure was achieved for coatings heated to 600 or 700 degrees C and, with increasing annealing temperature, the crystallite size increased. Small crystallites were found to be more soluble in the physiological environment but, at the same time, were able to induce early formation of a new apatite layer. A human osteoblast-like (HOB) cell model was used to evaluate the performance of these annealed SiHA coatings. HOB cells attached and grew well on coatings and, after 42 days in culture, a mineralization process was observed to be taking place, with evidence of calcium phosphate minerals throughout the extracellular matrix. Our findings indicated that an annealing temperature of 600 degrees C is sufficient to achieve crystalline SiHA coatings and exhibiting good chemical stability and bioactivity.
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Affiliation(s)
- E S Thian
- Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ, UK.
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Thian ES, Huang J, Best SM, Barber ZH, Bonfield W. Novel silicon-doped hydroxyapatite (Si-HA) for biomedical coatings: Anin vitro study using acellular simulated body fluid. J Biomed Mater Res B Appl Biomater 2006; 76:326-33. [PMID: 16080174 DOI: 10.1002/jbm.b.30368] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Magnetron co-sputtering was used to produce silicon-doped hydroxyapatite (Si-HA) as coatings intended for potential applications such as orthopedic and dental implants. It was found that the crystallinity of the as-sputtered coatings increased after annealing, resulting in a nanocrystalline apatite structure. Subsequently, the bioactivity of the coatings was evaluated in an acellular simulated body fluid (SBF). Physicochemical evaluation demonstrated that a carbonate-containing apatite layer, which is essential for bonding at the bone/implant interface, was formed on the coating surfaces after immersion in SBF between 4 and 7 days. The annealed coatings exhibited enhanced bioactivity and chemical stability under physiological conditions, as compared with the as-sputtered coatings. It is proposed that the rate at which the carbonate-containing apatite layer forms is dependent on the scale factor of the structure. A nanocrystalline structure can provide a higher number of nucleation sites for the formation of apatite crystallites, leading to a more rapid precipitation of carbonate-containing apatite layer. This work shows that Si-HA coatings offer considerable potential for applications in hard tissue replacement, owing to their ability to form a carbonate-containing apatite layer rapidly.
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Affiliation(s)
- E S Thian
- Cambridge Centre for Medical Materials, Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, United Kingdom.
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Thian ES, Huang J, Best SM, Barber ZH, Bonfield W. Magnetron co-sputtered silicon-containing hydroxyapatite thin films—an in vitro study. Biomaterials 2005; 26:2947-56. [PMID: 15603789 DOI: 10.1016/j.biomaterials.2004.07.058] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2004] [Accepted: 07/30/2004] [Indexed: 11/17/2022]
Abstract
The use of silicon-substituted hydroxyapatite (Si-HA) as a biomaterial has been reported recently. In vivo testing has shown that Si-HA promotes early bonding of the bone/implant interface. In order to extend its usage to major load-bearing applications such as artificial hip replacement implants, it has been proposed that the material could be used in the form of a coating on implant surfaces. This paper reports a preliminary study of the biocompatibility of magnetron co-sputtered silicon-containing hydroxyapatite (Si-HA) coatings on a metallic substrate. Magnetron co-sputtered Si-HA films of thickness 600 nm with a Si content of approximately 0.8 wt% were produced on titanium substrates. X-ray diffraction analysis showed that the as-deposited Si-HA films were either amorphous or made up of very small crystals. The crystallinity of Si-HA films was increased after post-deposition heat treatment at 700 degrees C for 3 h, and the principal peaks were attributable to HA. The formation of nano-scale silicon-calcium phosphate precipitates was noted on the heat-treated films. In vitro cell culture has demonstrated that human osteoblast-like cells attached and grew well on all films, with the highest cell growth and signs of mineralisation observed on the heat-treated Si-HA films. In addition, many focal contacts were produced on the films and the cells had well-defined actin cytoskeletal organisation. This work shows that as-deposited and heat-treated Si-HA films have excellent bioactivity and are good candidates when rapid bone apposition is required. Furthermore, heat-treated Si-HA films have improved biostability compared to as-deposited films under physiological conditions.
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Affiliation(s)
- E S Thian
- Department of Materials Science and Metallurgy, Cambridge Centre for Medical Materials, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, UK.
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Thian ES, Huang J, Best SM, Barber ZH, Bonfield W. A new way of incorporating silicon in hydroxyapatite (Si-HA) as thin films. J Mater Sci Mater Med 2005; 16:411-5. [PMID: 15875250 DOI: 10.1007/s10856-005-6980-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2004] [Accepted: 11/01/2004] [Indexed: 05/02/2023]
Abstract
Bioactive silicon-containing hydroxyapatite (Si-HA) thin films that can be used as coatings for bone tissue replacement have been developed. A magnetron co-sputtering technique was used to deposit Si-HA films up to 700 nm thick on titanium substrates, with a silicon level up to 1.2 wt%. X-ray diffraction demonstrated that annealing transformed the as-deposited Si-HA films which were amorphous, into a crystalline HA structure. A human osteoblast-like (HOB) cell model was used to determine the biocompatibility of these films. HOB cells were seen to attach and grow well on the Si-HA films, and the metabolic activity of HOB cells on these films was observed to increase with culture time. Furthermore, mineralisation of the cell layers was observed after 8 weeks of culture. Based on the present findings, Si-HA of different film compositions demonstrate bioactive properties in-vitro, and indicate the potential as biocoatings for a wide variety of medical implants including load-bearing applications such as the femoral stem of hip replacement implants.
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Affiliation(s)
- E S Thian
- Cambridge Centre for Medical Materials, Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB2 3QZ, UK.
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Abstract
This article reports the morphology and mechanical properties of sintered powder injection molded Ti-6Al-4V/HA parts in a simulated physiological environment. Sintered Ti-6Al-4V/HA parts were immersed in a simulated body fluid (SBF) with ion concentrations that were comparable to those of human blood plasma for a total period of 12 weeks. At intervals of 2 weeks, the immersed Ti-6Al-4V/HA parts were analyzed with the use of scanning electron microscopy (SEM), X-ray diffractometry (XRD), and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Mechanical properties such as flexural strength, flexural modulus, compressive strength, and compressive modulus were also evaluated. Results showed that complete dissolution of the more soluble phases such as tricalcium phosphate (TCP), tetracalcium phosphate (TTCP), and calcium oxide (CaO) were found after 2 weeks of immersion in SBF. ICP analysis showed that high calcium concentration release of around 200 ppm was observed in the SBF solution after 2-4 weeks of immersion, indicating that dissolution has taken place. Next, a gradual decrease in calcium concentration release in the SBF solution was observed after immersion for 4-6 weeks, with increasing amounts of calcium phosphate precipitates being observed on the Ti-6Al-4V/HA surface. Mechanical properties such as strength and modulus were found to deteriorate during 2-4 weeks of immersion, followed by gradual increment as the immersion period increased. This study also showed that parts sintered at 1150 C exhibited faster dissolution and precipitation rates than parts sintered at 1050 C in a physiological environment.
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Affiliation(s)
- E S Thian
- School of Mechanical and Production Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798
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Abstract
Taguchi method with an L9 orthogonal array was employed to investigate the sintered properties of Ti-6Al-4V/HA tensile bars produced by powder injection molding. The effects of sintering factors at the 90% significance level: sintering temperature (1050 degrees C, 1100 degrees C and 1150 degrees C), heating rate (5 degrees C/min, 7.5 degrees C/min and 10 degrees C/min), holding time (30, 45 and 60 min) and cooling rate (5 degrees C/min, 20 degrees C/min and 40 degrees C/min) were investigated. Results showed that sintering temperature, heating rate and cooling rate have significant effects on sintered properties, whereas the influence of holding time was insignificant. It was found that a sintering temperature of 1100 degrees C, a heating rate of 7.5 degrees C/min and a cooling rate of 5 degrees C/min increased the relative density, Vicker's microhardness, flexural strength and flexural modulus. However, a further increment of sintering temperature to 1150 degrees C did not show any discernable improvement in the relative density and Vicker's microhardness, but there was a slight increase of 0.6% and 0.9% in the flexural strength and flexural modulus, respectively. Mechanically strong Ti-6Al-4V/HA parts with an open porosity of around 50% were developed.
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Affiliation(s)
- E S Thian
- School of Mechanical and Production Engineering, Nanyang Technological University, Singapore, Singapore
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Abstract
Hydroxyapatite-coated titanium alloy composite powders (Ti-6Al-4V/HA) was produced by a ceramic slurry approach. The aim was to evaluate the stability of the coating when subjected to a physiological medium simulated body fluid (SBF). Three consolidation conditions (700 degrees C for 5 h, 700 degrees C for 8 h and 700 degrees C for 11 h) were used in the production of the Ti-6Al-4V/HA composite powders. Results showed that biodissolution followed by apatite precipitation had taken place after soaking in SBF. In addition, it was found that consolidation at 700 degrees C for 5 h resulted in a weak mechanical locking of calcium phosphate on the Ti-6Al-4V surfaces; and the formation of small crystallites, which would increase the dissolution rate.
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Affiliation(s)
- E S Thian
- School of Mechanical and Production Engineering, Nanyang Technological University, Singapore, Singapore
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