Load-bearing Bone Repair Research Articles

Evaluation of polyetheretherketone composites modified by calcium silicate and carbon nanotubes for bone regeneration: mechanical properties, biomineralization and induction of osteoblasts.

Desired orthopedic implant materials must have a good biological activity and possess appropriate mechanical property that correspond to those of human bone. Although polyetheretherketone (PEEK) has displayed a promising application prospect in musculoskeletal and dentistry reconstruction thanks to its non-biodegradability and good biocompatibility in the body, the poor osseointegration and insufficient mechanical strength have significantly limited its application in the repair of load-bearing bones and surgical operations. In this study, carbon nanotubes (CNT)/calcium silicate (CS)/polyetheretherketone ternary composites were fabricated for the first time. The addition of CS was mainly aimed at improving biological activities and surface hydrophilicity, but it inevitably compromised the mechanical strength of PEEK. CNT can reinforce the composites even when brittle CS was introduced and further upgraded the biocompatibility of PEEK. The CNT/CS/PEEK composites exhibited higher mechanical strengths in tensile and bending tests, 64% and 90% higher than those of brittle CS/PEEK binary composites. Besides, after incorporation of CNT and CS into PEEK, the hydrophilicity, surface roughness and ability to induce apatite-layer deposition were significantly enhanced. More importantly, the adhesion, proliferation, and osteogenic differentiation of mouse embryo osteoblasts were effectively promoted on CNT/CS/PEEK composites. In contrast to PEEK, these composites exhibited a more satisfactory biocompatibility and osteoinductive activity. Overall, these results demonstrate that ternary CNT/CS/PEEK composites have the potential to serve as a feasible substitute to conventional metal alloys in musculoskeletal regeneration and orthopedic implantation.

Fabrication and in vitro evaluation of Ca11B2Si4O22 ceramic for bone tissue engineering

• For the first time, a novel Ca 11 B 2 Si 4 O 22 powder was prepared by a sol-gel method. • In vitro experimental results indicated that the Ca 11 B 2 Si 4 O 22 ceramic enhanced osteogenic differentiation of mBMSCs. • Ca 11 B 2 Si 4 O 22 ceramics had good mechanical property. Calcium borosilicates are bioactive materials. This work synthesized a novel Ca 11 B 2 Si 4 O 22 powder by a sol-gel method. Besides, Ca 11 B 2 Si 4 O 22 ceramic was prepared via the dry-pressure molding and high temperature sintering. XRD analysis results revealed that the high-purity Ca 11 B 2 Si 4 O 22 crystalline powder was successfully prepared. Meanwhile, the compressive strength of the Ca 11 B 2 Si 4 O 22 ceramic reached to 290 MPa. More interestingly, the Ca 11 B 2 Si 4 O 22 ceramic exhibited excellent apatite-forming ability in simulated body fluid and osteogenic activity in vitro . These results indicated that the novel Ca 11 B 2 Si 4 O 22 ceramic holds great potential for load-bearing bone repair.

Calcium Silicate Whiskers-Enforced Poly(Ether-Ether-Ketone) Composites with Improved Mechanical Properties and Biological Activities for Bearing Bone Reconstruction.

Poly (ether-ether-ketone) (PEEK) displays promising potential application in bone tissue repair and orthopedic surgery due to its good biocompatibility and chemical stability. However, the bio-inertness and poor mechanical strength of PEEK greatly limit its application in load-bearing bones. In this study, calcium silicate whiskers (CSws) are synthesized and then compounded with PEEK to fabricate the PEEK/CSw composites with excellent mechanical properties, biological activity. Compared with PEEK, the PEEK/CSw composites exhibited higher hydrophilicity and ability to deposit hydroxyapatite on the surface. CSws are evenly dispersed in the PEEK matrix at 10wt% content and the mechanical strength of the PEEK/CSw composite is ≈96.9±2.4MPa, 136.3±2.4MPa, and 266.0±3.2MPa, corresponding to tensile strength, compressive strength, and bending strength, respectively, which is 20%, 18%, and 52% higher than that of pure PEEK. The composites improve the adhesion, proliferation, and osteogenic differentiation of BMSCs. Furthermore, PEEK/CSw composite remarkably improves bone formation and osteointegration, which has higher bone repair capacity than PEEK. These results demonstrate that the PEEK/CSw scaffolds display superior abilities to integrate with the host bone and promising potential in the field of load bearing bone repair.

Surface configuration of microarc oxidized Ti with regionally loaded chitosan hydrogel containing ciprofloxacin for improving biological performance.

The bacterial colonization and poor osseointegration of Ti implants significantly compromise their applications in load-bearing bone repair and replacement. To endorse the Ti with both excellent bioactivity and antibacterial ability, we developed a microarc oxidation coating that was modified uniformly by hydroxyapatite (HA) nanodots arrays and loaded regionally with chitosan hydrogel containing ciprofloxacin. The bonding between the HA nanodots covered coating and the chitosan hydrogel is further enhanced via silanization and chemical grafting of glutaraldehyde. Benefiting from the regionally loaded structure of the chitosan hydrogel, the chitosan hydrogel unloaded area can promote the cell adhesion and proliferation with excellent bioactivity, though relatively low OD value of cck8 has been observed at the beginning of the cell culturing. Whereas, the OD value of cck8 rises with the prolongation of the cell culturing time due to the degradation of the regionally loaded chitosan hydrogel. With the help of the laden ciprofloxacin in chitosan hydrogels, the sample effectively sterilizes the bacterial with a bacteriostatic ring. Therefore, regional loading of chitosan hydrogel containing ciprofloxacin on the modified microarc oxidation coating is a good approach to endorse Ti with both excellent bioactivity and antibacterial ability.

Synthesis and properties of high performance biobased liquid crystal copolyesters toward load-bearing bone repair application

In order to acquire satisfactory load-bearing bone substitute, a series of high performance biobased liquid crystal copolyesters derived from 4-hydroxybenzoic acid (HBA), phloretic acid (HPPA), vanillic acid (VA) and lactic acid (LA) were designed and prepared via “one-pot” melt polymerization method in this work. The structure and properties of the copolyesters were fully investigated by experimental measurements and molecular simulation. The copolyesters showed relative low melting temperatures (176–229 °C) and controllable crystallinity (15.3–36.5%), due to the increased molecular chain mobility caused by LA units and the multi-component copolymerization effect. Broad temperature range of nematic liquid crystal phase, good thermal stability as well as shear shinning and viscous melt flow behavior were observed for the copolyesters, indicating they had excellent melt processing ability. As compared with polyetheretherketone (PEEK) materials, the copolyesters exhibited better mechanical properties and hydrophilicity, which of the tensile strength and water contact angle were in range of 95 to 175 MPa and 72.5 to 84.8°, respectively, ascribing to the combination effect of its liquid crystal nature and chemical structure. In addition, the cytotoxicity test showed the copolyesters have good biocompatibility. It is shown that the unique combination of potential biodegradability, excellent mechanical properties, hydrophilicity and biocompatibility of the copolyesters make them prospective and suitable for application in load-bearing bone repair area.

Comparison of surface properties, cell behaviors, bone regeneration and osseointegration between nano tantalum/PEEK composite and nano silicon nitride/PEEK composite

Both tantalum (Ta) and silicon nitride (SN) exhibit osteogenic bioactivity and antibacterial property. In addition, as a biomaterial for bone repair, polyetheretherketone (PEEK) has outstanding biocompatibility and mechanical performances while it is biologically inert. In this study, by blending PEEK with Ta and SN nanoparticles, respectively, Ta/PEEK composite (TPC) and SN/PEEK composite (SPC) were fabricated for load-bearing bone repair. The surface roughness, hydrophilicity and surface energy of TPC containing Ta nanoparticles were higher than SPC containing SN nanoparticles and PEEK. In addition, TPC with Ta nanoparticles exhibited low antibacterial property while SPC with SN nanoparticles showed high bacterial property. Moreover, the MC3T3-E1 cells responses (e.g. proliferation and differentiation) to TPC was the highest while PEEK was the lowest in vitro. Furthermore, new bone formation and osseointegration for TPC was the highest while PEEK was the lowest in vivo. In conclusion, compared with PEEK, addition of Ta and SN nanoparticles into PEEK fabricated bioactive composites of TPC and SPC with optimized surface property, which played crucial roles in inducing cellular response/bone regeneration. Although the osteogenic activity of SPC was lower than TPC, SPC exhibited osteogenic activity and good antibacterial property, which could prevent infection from bacterial. Therefore, SPC would have better potential for bone substitute.

Preparation of high-strength β-CaSiO3 bioceramic with B2O3 and SiO2 sintering additives

Calcium silicate (CS) bioceramic is a promising candidate in bone tissue engineering due to its excellent bioactivity and biodegradability. However, the deficient mechanical properties make it challengeable in hard bone tissue replacement. In this work, high-strength β-CS bioceramics were prepared with low melting-point B2O3–SiO2 sintering additives using liquid phase sintering mechanism via a versatile milling-pressing-pressureless sintering route. The results showed that the addition of B2O3–SiO2 could significantly promote densification and induce the in-situ growth of β-CS rod-like grains. β-CS ceramics with 5 wt% addition of B2O3/SiO2 with mass ratio of 92.5:7.5 sintered at 1000 °C for 2 h exhibited a relatively high flexural strength of 228.14 MPa, increased by 340% compared to that of pure β-CS ceramic (52.08 MPa) prepared under the same conditions. The elevated strength fully qualified the strength requirement of cortical bone (135–193 MPa), indicating β-CS ceramic reinforced with B2O3–SiO2 additives had great potential in load-bearing bone repair.

Design of novel organic-inorganic composite bone cements with high compressive strength, in vitro bioactivity and cytocompatibility.

In this work, novel bioactive organic-inorganic composite bone cements consisting of tricalcium silicate (C3 S), sodium alginate (SA), and calcium sulfate hemihydrate (CS) were successfully fabricated for the first time via a special method designing material composition and internal structure simultaneously, which was intended to enhance mechanical performance by combining progressive hydration process of C3 S with distinctive gelation capacity of SA and further improve degradability and self-setting properties with the addition of CS. Depending on the synergistic combination of hydration and gelation, the C3 S/SA/CS composite cements (45/45/10 wt %) obtained extremely higher compressive strength up to 92.41 MPa as compared with each single component. The reinforcing mechanisms involving interfacial interaction and interior microstructure were proposed to explain this enhancement phenomenon. Additionally, the final setting time could be reduced from 68 min to 21 min with the increasing CS content. The composite cements possessed good apatite mineralization ability in simulated body fluid solution and moderate degradation rate in phosphate buffer solution. What's more, the composite cements exhibited excellent cytocompatibility and increased proliferation of rat bone-marrow stem cells. This study could provide guidelines for the preparation of bioactive composite cements with enhanced mechanical performance, which may be suitable for load-bearing bone repair. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2365-2377, 2019.

Enhanced Osseointegration of Hierarchically Structured Ti Implant with Electrically Bioactive SnO2-TiO2 Bilayered Surface.

The poor osseointegration of Ti implant significantly compromise its application in load-bearing bone repair and replacement. Electrically bioactive coating inspirited from heterojunction on Ti implant can benefit osseointegration but cannot avoid the stress shielding effect between bone and implant. To resolve this conflict, hierarchically structured Ti implant with electrically bioactive SnO2-TiO2 bilayered surface has been developed to enhance osseointegration. Benefiting from the electric cue offered by the built-in electrical field of SnO2-TiO2 heterojunction and the topographic cue provided by the hierarchical surface structure to bone regeneration, the osteoblastic function of basic multicellular units around the implant is significantly improved. Because the individual TiO2 or SnO2 coating with uniform surface exhibits no electrical bioactivity, the effects of electric and topographic cues to osseointegration have been decoupled via the analysis of in vivo performance for the placed Ti implant with different surfaces. The developed Ti implant shows significantly improved osseointegration with excellent bone-implant contact, improved mineralization of extracellular matrix, and increased push-out force. These results suggest that the synergistic strategy of combing electrical bioactivity with hierarchical surface structure provides a new platform for developing advanced endosseous implants.

Damage mechanisms in bioactive glass matrix composites under uniaxial compression.

The damage and crack resistance improvement of bioactive glass is of prime importance, particularly when applied to the repair of load-bearing bones. The present contribution is focused on the prediction of damage mechanisms and crack resistance under uniaxial compression of bioactive glass matrix composites reinforced with a particulate phase. In order to characterize the effects of voids and particles on the damage mechanisms and the macro-response, a two-step homogenization is performed by considering the two phases existing at two different scales: micro/meso through the homogenization of the porous matrix and then meso/macro through the periodic micro-field approach. The damage in the bioactive glass matrix is computed via an anisotropic stress-based damage model, implemented into a finite element program. Failure resulting of excessive damage accumulation in the bioactive glass matrix is predicted by a critical damage criterion combined with a vanishing element technique. The implication of particles in the toughening mechanism as well as the damage and crack resistance improvement in this class of porous biomaterials is highlighted via a parametric study using the proposed numerical model.

Carbon Fibre Reinforced Nano-HA/PA46 Ternary Biocomposite: Mechanical Properties and Cytocompatibility

A novel ternary composite of carbon fiber, nano-hydroxyapatite and polyamide46 (CF/HA/PA46) was prepared by extrusion method. The mechanical properties were characterized and preliminary cell responses were investigated to explore the feasibility of load-bearing bone repair. The results showed that the bending strength and tensile strength were 159-222 MPa and 117-199 MPa, respectively, when the CF content was in the range of 5%-20%. The tensile modulus was 7.7-10.8 GPa. The MG-63 cells with an osteogenic phenotype were well adhered and spread on the CF/HA/PA46 surface. Compared to the HA/PA46 control, the addition of CF into HA/PA46 manifest improved the toughness and had little negative effects on MG-63 cells. The obtained ternary composite has potential as load-bearing bone repair.

Carboxylated Agarose (CA)-Silk Fibroin (SF) Dual Confluent Matrices Containing Oriented Hydroxyapatite (HA) Crystals: Biomimetic Organic/Inorganic Composites for Tibia Repair.

By in situ combining the dual cross-linking matrices of the carboxylated agarose (CA) and the silk fibroin (SF) with the hydroxyapatite (HA) crystals, the CA-SF/HA composites with optimal physicochemical and biological properties were obtained, which were designed to meet the clinical needs of load-bearing bone repair. With the synergistic modulation of the dual organic matrices, the HA nanoparticles presented sheet and rod morphologies due to the preferred orientation, which successfully simulated the biomineralization in nature. The chemical reactivity of the native agarose (NA) was significantly enhanced via carboxylation, and the CA exhibited higher thermal stability than the NA. In the presence of SF, the composites showed optimal mechanical properties that could meet the standard of bone repair. The degradation of the composites in the presence of CA and SF was significantly delayed such that the degradation rate of the implant could satisfy the growth rate of the newly formed bone tissue. The in vitro tests confirmed that the CA-SF/HA composite scaffolds enabled the MG63 cells to proliferate and differentiate well, and the CA/HA composite presented greater capability of promoting the cell behaviors than the NA/HA composite. After 24 days of implantation, newly formed bone was observed at the tibia defect site and around the implant. Extensive osteogenesis was presented in the rats treated with the CA-SF/HA composites. In general, the CA-SF/HA composites prepared in this work had the great potential to be applied for repairing large bone defects.

3D printing magnesium-doped wollastonite/β-TCP bioceramics scaffolds with high strength and adjustable degradation

Mechanical strength of bioceramic scaffolds is a problem to treat the load bearing bone defects. We developed the Mg-doping wollastonite (CSi-Mg)-based scaffolds with high strength via 3D printing technology. The effect of pore size, β-tricalcium phosphate (β-TCP) content (x%), and heating schedule on the strength of scaffolds were investigated systematically. Incorporation of β-TCP could readily adjust the sintering properties of the CSi-Mg scaffolds and the scaffolds with high (20–30%) and low (10–20%) β-TCP possess much high strength (80–100MPa or 120–140MPa) after undergoing one- or two-step sintering. Meanwhile, the CSi-Mg/TCPx (x=10, 20) with medium-pore (∼320μm) had over 100MPa in compression and ∼52% in porosity. In particular, the composite scaffolds maintained appreciable strength (over 50MPa) after immersion in Tris buffer for a long time stage (6 weeks). These findings demonstrate that the CSi-Mg/TCPx scaffolds are promising for treating some challengeable bone defects, especially for load-bearing bone repair.

Mechanics, degradability, bioactivity, in vitro, and in vivo biocompatibility evaluation of poly(amino acid)/hydroxyapatite/calcium sulfate composite for potential load-bearing bone repair.

A ternary composite of poly(amino acid), hydroxyapatite, and calcium sulfate (PAA/HA/CS) was prepared using in situ melting polycondensation method and evaluated in terms of mechanical strengths, in vitro degradability, bioactivity, as well as in vitro and in vivo biocompatibility. The results showed that the ternary composite exhibited a compressive strength of 147 MPa, a bending strength of 121 MPa, a tensile strength of 122 MPa, and a tensile modulus of 4.6 GPa. After immersion in simulated body fluid, the compressive strength of the composite decreased from 147 to 98 MPa for six weeks and the bending strength decreased from 121 to 75 MPa for eight weeks, and both of them kept stable in the following soaking period. The composite could be slowly degraded with 7.27 wt% loss of initial weight after soaking in phosphate buffered solution for three weeks when started to keep stable weight in the following days. The composite was soaked in simulated body fluid solution and the hydroxyapatite layer, as flower-like granules, formed on the surface of the composite samples, showing good bioactivity. Moreover, it was found that the composite could promote proliferation of MG-63 cells, and the cells with normal phenotype extended and spread well on the composite surface. The implantation of the composite into the ulna of sheep confirmed that the composite was biocompatible and osteoconductive in vivo, and offered the PAA/HA/CS composite promising material for load-bearing bone substitutes for clinical application.

Silk as a biocohesive sacrificial binder in the fabrication of hydroxyapatite load bearing scaffolds

Limitations of current clinical methods for bone repair continue to fuel the demand for a high strength, bioactive bone replacement material. Recent attempts to produce porous scaffolds for bone regeneration have been limited by the intrinsic weakness associated with high porosity materials. In this study, ceramic scaffold fabrication techniques for potential use in load-bearing bone repairs have been developed using naturally derived silk from Bombyx mori. Silk was first employed for ceramic grain consolidation during green body formation, and later as a sacrificial polymer to impart porosity during sintering. These techniques allowed preparation of hydroxyapatite (HA) scaffolds that exhibited a wide range of mechanical and porosity profiles, with some displaying unusually high compressive strength up to 152.4 ± 9.1 MPa. Results showed that the scaffolds exhibited a wide range of compressive strengths and moduli (8.7 ± 2.7 MPa to 152.4 ± 9.1 MPa and 0.3 ± 0.1 GPa to 8.6 ± 0.3 GPa) with total porosities of up to 62.9 ± 2.7% depending on the parameters used for fabrication. Moreover, HA-silk scaffolds could be molded into large, complex shapes, and further machined post-sinter to generate specific three-dimensional geometries. Scaffolds supported bone marrow-derived mesenchymal stem cell attachment and proliferation, with no signs of cytotoxicity. Therefore, silk-fabricated HA scaffolds show promise for load bearing bone repair and regeneration needs.

Synthesis and characterization of CaP/Col composite scaffolds for load-bearing bone tissue engineering

Porous calcium phosphate (CaP) ceramics are widely used in bone tissue engineering due to their excellent biological properties. However, the inherent brittleness of CaP ceramics has restricted their applications in the repair of load-bearing bones. This study aimed to improve the mechanical strength of CaP-based scaffolds by compositing CaP with collagen (Col). In this study, the influences of CaP porous structure, collagen content and cross-linking method on scaffolds mechanical strength were investigated. The morphologies of the composites were characterized by scanning electron microscope, and the mechanical properties of the scaffolds were assessed by dynamic mechanical analysis. The biocompatibility of the scaffolds was evaluated by culturing human bone marrow mesenchymal stem cells (MSCs) in vitro. The results show that the mechanical properties of scaffolds can be significantly improved by optimizing composite processes. Furthermore, remarkable viability and proliferation of MSCs on scaffolds was observed, which demonstrated good biocompatibility of the scaffolds. These results suggest that CaP/Col composite can be a promising scaffold for repair of load-bearing bones.

In vitro antimicrobial activity of vancomycin-eluting bioresorbable β-TCP-polylactic acid nanocomposite material for load-bearing bone repair

Release of antimicrobial agents from bone healing devices can dramatically reduce the risk of implant-associated infection. Here we report the fabrication and antimicrobial activity of a multifunctional load-bearing bioresorbable material that can provide mechanical support to the healing bone all while slowly releasing an antibiotic drug. Dense beta-tricalcium phosphate (β-TCP)-40vol% polylactic acid (PLA) nanocomposite containing 1wt% vancomycin (VH) was high pressure consolidated at 2.5GPa, at room temperature, or at 120°C. Over the course of 5weeks in TRIS solution, the β-TCP-PLA-VH nanocomposite released approximately 90% of its drug load. Specimens consolidated at 120°C had the highest initial mechanical properties and maintained 85% of their compressive strength and 30% of their bending strength after 5weeks release. In vitro growth inhibition study showed significant antimicrobial efficacy of VH-impregnated β-TCP-PLA against methicillin-resistant Staphylococcus aureus when exposed to both high (2×10(5)CFU/mL) and very high (1×10(8)CFU/mL) bacterial concentrations. After 1week, total eradication of the microorganisms was achieved. The results suggest that the developed high-strength antibiotic-eluting β-TCP-PLA nanocomposite can be a promising material for orthopedic surgical devices.

Bone substitute biomedical material of multi-(amino acid) copolymer: in vitro degradation and biocompatibility

Degradable polymers with good mechanical strength as bone repair biomaterials have been paid more attention in biomedical application. In this study, a multi-(amino acid) copolymer consisting of 6-aminocaproic acid and five natural amino acids was prepared by a reaction of acid-catalyzed condensation. The results revealed that the copolymer could be slowly degradable in Tris-HCl solution, and lost its initial weight of 31.9 wt% after immersion for 12 weeks, and the changes of pH value of Tris-HCl solution were in range from 6.9 to 7.4 during soaking. The compressive strength of the copolymer decreased from 107 to 68 MPa after immersion for 12 weeks. The proliferation and differentiation of MG-63 cells on the copolymer significantly increased with time, and the cells with normal phenotype extended and spread well on the copolymer surfaces. When the copolymer was implanted in muscle and bone defects of femoral cortex of dogs for 12 weeks, the histological evaluation confirmed that the copolymer exhibited excellent biocompatibility and more effective osteogenesis in vivo. When implanted into cortical bone defects of dogs, the copolymer could be combined directly with the natural bone without fibrous capsule tissue between implants and host bone. The results indicated that the multi-(amino acid) copolymer with sufficient strength, good biocompatibility and osteoconductivity had clinical potential for load-bearing bone repair or substitution.

Freeze extrusion fabrication of 13–93 bioactive glass scaffolds for bone repair

A solid freeform fabrication technique, freeze extrusion fabrication (FEF), was investigated for the creation of three-dimensional bioactive glass (13-93) scaffolds with pre-designed porosity and pore architecture. An aqueous mixture of bioactive glass particles and polymeric additives with a paste-like consistency was extruded through a narrow nozzle, and deposited layer-by-layer in a cold environment according to a computer-aided design (CAD) file. Following sublimation of the ice in a freeze dryer, the construct was heated according to a controlled schedule to burn out the polymeric additives (below ~500°C), and to densify the glass phase at higher temperature (1 h at 700°C). The sintered scaffolds had a grid-like microstructure of interconnected pores, with a porosity of ~50%, pore width of ~300 μm, and dense glass filaments (struts) with a diameter or width of ~300 μm. The scaffolds showed an elastic response during mechanical testing in compression, with an average compressive strength of 140 MPa and an elastic modulus of 5-6 GPa, comparable to the values for human cortical bone. These bioactive glass scaffolds created by the FEF method could have potential application in the repair of load-bearing bones.

Nano-Hydroxyapatite/Polymer Composite Scaffold for Bone Tissue Engineering

Nano-hydroxyapatite/polyamide66 (n-HA/PA66) composite scaffolds are prepared using phase separation and phase separation in combination with particle leaching, and both the composite powder and paste are used as starting materials. The composite is characterized by IR and XRD. The micro-architecture of the scaffolds is observed by SEM, and the mechanisms that the formation of the porous structure follows have been investigated preliminarily. The results show that scaffold prepared by phase separation in combination with particle leaching method using composite powder as starting material possesses controllable porosity and interconnectivity, as well as good mechanical strength comparable to human cancellous bone, suitable for being the tissue-engineered scaffold for load-bearing bone repair. Furthermore, scaffold made by phase separation using composite paste as starting material exhibits an anisotropy both in morphology and mechanical properties, which indicates the potential of guiding cell seeding, distribution and new tissue formation in preferential direction.