β-TCP scaffold coated with PCL as biodegradable materials for dental applications

Requirements for an ideal scaffold include biocompatibility, biodegradability, mechanical strength and sufficient porosity and pore dimensions. Beta tricalcium phosphate (β-TCP) has competent biocompatibility and biodegradability, but has low mechanical strength because of its porous structure. Polycaprolactone (PCL) is a biodegradable polymer with elastic characteristics and good biocompatibility. In this study, β-TCP/PCL composites were prepared in different ratio and their morphology, phase content, mechanical properties, biodegradation and biocompatibility were investigated. After coating, surfaces of β-TCP scaffolds were covered with the PCL while some of the pores were partially clogged. The compression and bending strength of β-TCP scaffolds were significantly enhanced by PCL coating. The degradation rate of the scaffold in Tris buffer was reduced with higher content of the PCL coating. MTT and ALP assays showed that the osteoblast cells could proliferate and differentiate on PCL coated scaffolds as well as on bare β-TCP scaffolds. Based on the comprehensive analysis achieved in this study, it is concluded that the β-TCP/PCL composite scaffold fabricated with 40% β-TCP and 5% PCL exhibits optimum properties suitable for dental applications.     

Preparation and in vitro degradation of novel bioactive polylactide/wollastonite scaffolds

Composite scaffolds for applications in bone engineering from poly(D,L ‐lactide) (PDLLA) incorporated with different proportional bioactive wollastonite powders were prepared through a salt‐leaching method, using NH₄HCO₃ as porogen. The pore structures and morphology of the scaffolds were determined by scanning electron microscopy (SEM). The bioactivity of composite materials was evaluated by examining its ability to initiate the formation of hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂)(HAp) on its surface when immersed in simulated body fluids (SBF). The in vitro degradation behaviors of these scaffolds were systematically monitored at varying time periods of 1, 2, 4, 6, 8, 11, 14, 17, 20, 24, and 28 weeks postimmersion in SBF at 37°C. FT‐IR, XPS, XRD, and SEM measurements revealed that hydroxyapatite commenced to form on the surface of the scaffolds after 7 days of immersion in SBF. The measurements of weight loss, pH, and molecular weight of the samples indicated that PDLLA/wollastonite composite scaffolds degraded slower than the pure PDLLA scaffolds do. Addition of wollastonite enhanced the mechanical property of the composite scaffolds. The in vitro osteoblast culture experiment confirmed the biocompatibility of the scaffold for the growth of osteo‐blasts. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009.     

Fabrication and properties of 3D printed zirconia scaffold coated with calcium silicate/hydroxyapatite

The scaffold of bone repair needs a variety of material combinations to meet its intended performance; a typical single material such as zirconia has excellent mechanical properties, while hydroxyapatite and calcium silicate are bioactive materials with different degradation rates. In this paper, porous zirconia scaffolds were fabricated using 3D printing technology. The surface of the scaffold was coated by dipping with different contents of calcium silicate and hydroxyapatite to improve the biological activity and mechanical properties. Mechanical tests show that the coating material can effectively fill the pores of the porous scaffold, increasing its compressive strength by an average of 55%. The simulated body fluid (SBF) test showed that the higher calcium silicate in the coating increased the degradation rate. Cell experiments showed that the coated scaffolds exhibited good cytocompatibility and were beneficial to the proliferation and differentiation of cells. In conclusion, coated scaffolds have potential applications in the field of bone repair.     

Porous hydroxyapatite scaffolds produced by the combination of the gel-casting and freeze drying techniques

A technique combining gel-casting and freeze drying methods is introduced to prepare porous hydroxyapatite scaffolds which allow for better control of the scaffold microstructure and have improved mechanical properties. A monomeric system which is known to be a suitable gelling agent for setting ceramic suspensions into dense forms was selected to produce ceramic foams. Different concentrations of sodium lauryl sulphate solution were added into the hydroxyapatite gel suspension as a pore former. The effect of the solid content on the mechanical properties of the scaffold was also investigated. Rapid freezing with liquid nitrogen was performed according to the freeze drying technique and the porous structure and morphology of the scaffolds were analyzed by scanning electron microscopy. The mechanical properties of the hydroxyapatite scaffolds were determined by testing compressive strength using a universal testing machine. The prepared scaffolds were characterized by well-defined pore connectivity along with directional, uniform and completely open porosity. The maximum compressive strength of about 17?MPa obtained from the suspension consisted of 50% solid content with 20% concentration of sodium lauryl sulphate solution. The results show that sodium lauryl sulphate solution plays a significant role in changing the pore structure of hydroxyapaite scaffolds in systems having high solid content.     

Porous Hydroxyapatite Scaffolds Coated With Bioactive Apatite–Wollastonite Glass–Ceramics

The objective of this study was to fabricate porous hydroxyapatite (HA) scaffolds coated with bioactive A/W glass–ceramics and to examine their mechanical and biological properties. Firstly, the HA scaffolds were prepared by the polymeric sponge replication method, and then A/W glasses were coated on the surface of the struts. All of the scaffolds had a highly porous structure with well-interconnected pores. It was observed that the bioactive glass coating markedly increased the strength of the HA scaffolds. This enhancement was attributed to the formation of a dense and strong coating layer on the weak HA struts. The in vitro bioactivities of the scaffolds were markedly improved by the coatings. When the coated scaffolds were soaked in a simulated body fluid (SBF), the bone-like apatite crystals were well mineralized on their surfaces. Osteoblast-like cells (MC3T3) adhered, spread, and grew well on the porous scaffolds. The cells placed on the glass-coated HA scaffold showed a higher proliferation rate and alkaline phosphatase (ALP) activity than those on the pure HA scaffold. These results demonstrate that the bioactive glass coating is effective in improving the strength and bioactivity of the porous HA scaffolds.     

Synthesis,characterization and in-vitro behavior of natural chitosan-hydroxyapatite-diopside nanocomposite scaffold for bone tissue engineering

Composite materials based on a combination of biodegradable polymers and bioactive ceramics, including chitosan and hydroxyapatite are discussed as suitable materials for scaffold fabrication. Diopside is a member of bioactive silicates; it is a good choice for hard tissue engineering because of its biocompatibility with host tissue and high mechanical strength. Chitosan and hydroxyapatite were extracted from shrimp shell and bovine bone, respectively and diopside nanoparticles were prepared by the sol-gel method. The present study reports on a chitosan composite which was reinforced by hydroxyapatite and diopside; the scaffolds were fabricated by the freeze-drying method. The so-produced chitosan-hydroxyapatite-diopside (CS-HA-DP) scaffolds were further cross-linked using tripolyphosphate (TPP) to achieve enhanced mechanical strength. The ratios of the ceramic components in composites were 5-58-37, 10-55-35, and 15-52-33 (diopside-hydroxyapatite-chitosan, w/w %). The physicochemical properties of scaffolds were investigated using Fourier-transform infrared spectrometry (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) techniques. The effect of scaffolds composition on bioactivity and biodegradability were studied well. To investigate mechanical properties of samples, compression test was done. Results showed that the composite scaffold with 5% DP has the highest mechanical strength. The porosity of composites dropped from 92% to 76% by increasing the amount of DP. Cytocompatibility of the scaffolds was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, alkaline phosphatase (ALP) activity, and cell attachment studies using human osteoblast cells. Results demonstrated no sign of toxicity and cells were found to be attached to the pore walls within the scaffolds; moreover, results illustrated that the developed composite scaffolds could be a potential candidate for tissue engineering.     

可注射nHA/PU复合多孔骨修复支架制备及表征

兼具良好孔隙率和原位任意塑形固化的可注射复合多孔骨修复材料在临床不规则骨缺损的治疗方面显示出巨大的优势。本研究通过优化双组分设计,以水为发泡剂制备可注射纳米羟基磷灰石/聚氨酯（nHA/PU）复合多孔支架。利用扫描电子显微镜（SEM）、傅里叶变换红外光谱（FTIR）、X射线衍射（XRD）、力学测试及Gillmore针测试等手段对制备的支架进行结构形貌、化学组成、力学性能和固化时间表征。结果表明,本研究制备的可注射nHA/PU复合多孔支架孔隙率高、孔隙贯通性好,孔径分布在100~700μm,适宜细胞和组织向孔内生长;添加20% nHA显著提高了PU支架的力学强度,但降低了支架的孔隙率;可注射支架在8h固化,适宜临床操作。本研究制备的可注射nHA/PU复合多孔支架在不规则骨缺损修复领域具有较大的应用潜力。     

Compressive strength and biomineralisation improvement by water glass coating on porous calcium phosphate scaffolds

Calcium phosphate (Ca–P) based scaffolds were found to be a favourable alternative for orthopaedic applications because of their similar chemical composition to natural bone. In this study, porous triphasic Ca–P scaffolds containing macropores (∽200?μm) interconnected with micropores (∽20?μm) were fabricated using an extrusion method. The hydroxyapatite/tricalcium phosphate ratio of the porous scaffolds was varied using different ratios of starting materials while keeping the Ca/P ratio fixed (1.5). A water glass coating on the porous Ca–P scaffolds increased the compressive strength by 45% without significantly decreasing the porosity of the H100D50 scaffold. The maximum compressive strength, ～15?MPa, was achieved on the H100D50 scaffold. The ability for apatite formation in simulated body fluid was amplified by the water glass coating on the sintered Ca–P scaffolds. Therefore, a water glass coating can be used to enhance the mechanical properties as well as the biomineralisation of the porous ceramic scaffolds.     

Preparation and in vitro assessment of economic bio-scaffolds modified with wollastonite (CaSiO3)

Porous bioceramic scaffolds are the preferred option for substituting spongy bone. Therefore, this study evaluates the use of carbonate associated with apatite rocks at Hamadat mines (referred to as calcite) as a source of low-cost bioactive material useful for biomedical applications. In this study, the depositional environment and mineralogical, and petrographic behavior of such depositions were studied. Furthermore, the possibility of producing highly porous, low-cost bioceramic scaffolds using the freeze-drying technique was demonstrated. The bioactivity of the produced scaffolds was enhanced by adding different ratios of wollastonite (25, 50 and 75 wt %) to the scaffold’s batches. However, the scaffolds were coated with ZnCl₂ to enhance their antimicrobial susceptibility. The physical and mechanical properties as well as the phase composition and microstructure of the prepared scaffolds were investigated. The X-ray diffraction results revealed the formation of pure phase of α-wollastonite after 3 h of sintering at 1200 °C. To estimate the scaffolds’ biodegradability, the pH and the weight change were measured. The results were confirmed using the inductively coupled plasma measurements for the scaffolds deposited in a simulated body fluid (SBF) solution for 28 days. Results showed that the scaffolds had excellent bioactivity, which was demonstrated by the appearance of apatite particles on their surface after being immersed in the SBF. The antimicrobial activity test revealed that Zn²⁺, NPs and CaSiO₃ had positive effects due to their oxidative stress process. Zn²⁺, Ca²⁺, and Si⁴⁺ cations can be adsorbed on bacterial surface membranes, interacting with the respiratory microbial enzymes, inhibiting their actions, and damaging the cell, thereby causing the bacterial cell decomposition.     

Preparation and characterization of aliphatic polyurethane and hydroxyapatite composite scaffold

Novel porous composite scaffolds for tissue engineering were prepared from aliphatic biodegradable polyurethane (PU) elastomer and hydroxyapatite (HA). It was found that the aliphatic PU was possible to load up to 50 wt % HA. The morphology and properties of the scaffolds were characterized by scanning electron microscope, X‐ray diffraction, infrared absorption spectra, mechanical testing, dynamic mechanical analysis, and in vitro degradation measurement. The results indicated that the HA/PU scaffolds had an interconnected porous structure with a pore size mainly ranging from 300 to 900 μm, and 50–200 μm micropores existed on the pores' walls. The average pore size of macropores and micropores are 510 and 100 μm, respectively. The compressive strength of the composite scaffolds showed higher enhancement with increasing HA content. In addition, the polymer matrix was completely composed of aliphatic component and exhibited progressive mass loss in vitro degradation, and the degradation rate depended on the HA content in PU matrix. The porous HA/PU composite may have a good prospect to be used as scaffold for tissue engineering. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of ZnO reinforcement on the compressive properties,in vitro bioactivity,biodegradability and cytocompatibility of bone scaffold developed from bovine bone-derived HAp and PMMA

In this study, the effect of zinc oxide (ZnO) incorporation on the properties of Hydroxyapatite (HAp)/Poly(methyl methacrylate) (PMMA)/ZnO based composite bone scaffold is investigated. HAp is derived from calcination of bovine bone bio-waste and ZnO is synthesized by direct precipitation technique. Porous scaffolds are developed by gas foaming process using ammonium bicarbonate as the foaming agent and adding ZnO nanoparticles (NPs) at 2.5, 5, 7.5 and 10% (w/w) respectively. Incorporation of ZnO up to 5% (w/w) is found to significantly enhance the porosity, compressive strength, thermal stability and swelling properties of the developed scaffolds. In-vitro bioactivity and biodegradability assessment using simulated body fluid (SBF) show improved results of 5% ZnO loaded scaffolds. Furthermore, the composite scaffold show enhanced cytocompatibility during the in vitro cytotoxicity test performed using XTT assay. A comprehensive study on the scaffold properties shows that 5% ZnO composite scaffold exhibits the best-optimized properties suitable for bone tissue engineering applications.     

Novel Layered Hydroxyapatite/Tri‐Calcium Phosphate–Zirconia Scaffold Composite with High Bending Strength for Load‐Bearing Bone Implant Application

The integration of biological and mechanical requirements remains a challenge in developing porous hydroxyapatite (HA) and tri‐calcium phosphate (TCP) scaffolds for load‐bearing bone implant application. With the newly developed slip‐deposition and coating‐substrate co‐sintering technique, a strong layered HA/TCP‐zirconia scaffold composite structure was successfully fabricated. The bending strength (321 MPa) of this composite can match upper strength limit of the natural compact bone. The HA‐based scaffold coating has multiple scale porous structures with pore size ranging 1–10 and 20–50 μm. The zirconia‐based substrate is also porous with submicropores. Focus ion beam micrographs show most of the micropores in the coating are interconnected. Microindentation and primarily adhesive strength tests demonstrate that the scaffold coating strongly bonds with the zirconia based substrate. In vitro cell culture study indicates that the coatings have no cytotoxicity. It is evident that the strong layered HA–zirconia scaffold composite offers new implant options for bone repairs requiring immediate load bearing capacity.     

Effect of PCL concentration on PCL/CaSiO3 porous composite scaffolds for bone engineering

Porous polycaprolactone (PCL)-coated calcium silicate (CaSiO₃) composite scaffolds were successfully prepared by 3D gel-printing (3DGP) and vacuum impregnation technology in this study. The effect of different PCL concentration on porous CaSiO₃ scaffolds prepared by 3DGP technology was studied. The composition and morphological characteristics of PCL/CaSiO₃ scaffolds were tested by using fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS) analysis. PCL coating amount on the scaffolds surface was calculated by thermogravimetric analysis (TGA). Compressive strength was tested by a universal testing machine, and degradability was tested by immersing the scaffolds in a simulated body fluid (SBF). The results show that PCL coating thickness increased from 7.29 μm to 12.2 μm, and the compressive strength of the corresponding composite scaffolds increased from 17.15 MPa to 24.12 MPa following with PCL concentration increasing from 7.5% to 12.5%. When the porous composite scaffolds were immersed in SBF for 28 days, the degradation ratio was 1.06% (CaSiO₃), 1.63% (CaSiO₃-7.5PCL), 1.81% (CaSiO₃-10PCL) and 1.55% (CaSiO₃-12.5PCL), respectively. It is obviously that PCL/CaSiO₃ composite scaffolds, which are suitable for bone growth in bone repair engineering, are beneficial to improve the mechanical properties and biodegradability of pure CaSiO₃ scaffolds.     

In Situ Crosslinking of Highly Porous Chitosan Scaffolds for Bone Regeneration: Production Parameters and In Vitro Characterization

Various methods of chitosan scaffold production are reported in the literature so far. Here, in situ crosslinking with glutaraldehyde is reported for the first time. It combines pore formation and chitosan crosslinking in a single step. This combination allows incorporation of fragile molecules into 3D porous chitosan scaffolds produced by simple and gentle lyophilization. In this study, parameters of in situ crosslinking of porous chitosan scaffold formation as well as their effect on degradation and bioactivity of the scaffolds are examined. The scaffolds are characterized in the context of their prospective application as bone substitute material. The addition of calcium phosphate phases (hydroxyapatite, brushite) to the macroporous chitosan scaffolds allows manipulation of the bioactivity that is investigated by incubation in simulated body fluid (SBF). The bioactivity is significantly influenced by the modus of changing the fluid (static, daily‐, and twice‐a‐week change). Scaffolds are morphologically characterized by means of scanning electron microscopy, and the mechanical stability is tested after incubation in SBF and phosphate‐buffered saline.     

3D Composite scaffolds using strontium containing bioactive glasses

In this study, it was aimed to fabricate and characterize three-dimensional composite scaffolds derived from Sr-doped bioactive glass for bone tissue engineering applications. The scaffolds were fabricated by using polymer foam replication technique and coated with gelatin to be able to improve the properties of them. The porous scaffolds were successfully synthesized using optimized process parameters. Both coated and uncoated scaffolds favored precipitation of calcium phosphate layer when they were soaked in simulated body fluid (SBF). Gelatin coating improved the mechanical properties of the scaffold and also it did not change the bioactive behavior of the scaffold. It was observed that there was a good pore interconnectivity maintained in the scaffold microstructure. Results indicated that scaffolds can deliver controlled doses of strontium toward the SBF medium. That is the determinant for bone tissue regeneration, as far as strontium is known to positively act on bone remodeling.     

Synthesis,Characterization and <Emphasis Type="Italic">in-vitro</Emphasis> Study of Chitosan/Gelatin/Calcium Phosphate Hybrid Scaffolds Fabricated Via Ion Diffusion Mechanism for Bone Tissue Engineering

In this study, biomimetic scaffolds were designed to investigate calcium phosphate formation via a double diffusion mechanism within a gelatin/chitosan hydrogel in biological pH and temperature. Three types of samples with initial percentages of chitosan (20, 30 and 40 wt. %) were prepared. Diffusion of calcium and phosphate ions through the hydrogel formed a precipitation layer. Samples were freeze dried to form porous scaffolds and soaked in glutaraldehyde to increase their mechanical properties. X-ray diffraction (XRD), Fourier transform infra-red (FTIR) spectroscopy and scanning electron microscopy (SEM) were employed to investigate the microstructure and to characterize the prepared scaffolds. Analysis of precipitation indicated the presence of brushite and hydroxyapatite. The amorphous calcium phosphate phase converted into crystalline hydroxyapatite after immersion in simulated body fluid which mimics the formation of hydroxyapatite in the human body. FTIR results suggested the presence of structural hydroxyl and phosphate bonds in the structure of the prepared scaffolds which could be due to the formation of hydroxyapatite. With increasing amount of chitosan in the composite scaffold, the water up-take ability was increased from 380 to 660 %, yield strength and Young’s modulus slightly decreased and the crystalinity of the precipitated phase increased. Mechanical properties obtained from the samples were in the range of cancellous bone. MTT assay results and alkaline phosphatase activity showed prepared scaffolds had proper biocompatibility.     

Effects of microwave sintering on the properties of porous hydroxyapatite scaffolds

Microwave sintering was used to process porous hydroxyapatite scaffolds fabricated by the extrusion deposition technique. The effects of microwave sintering on the microstructure, phase composition, degradation, compressive strength and biological properties of the scaffolds were investigated. After rapid sintering, scaffolds with controlled structure, high densification and fine grains were obtained. A significant increase in mechanical strength was observed relative to conventional sintering. The scaffolds (55–60% porosity) microwave sintered at 1200 °C for 30 min exhibited the highest average compressive strength (45.57 MPa). The degradation was determined by immersing the scaffolds in physiological saline and monitoring the Ca²⁺concentration. The results indicated that the microwave-sintered scaffolds possessed higher solubility than conventionally sintered scaffolds, as it released more Ca²⁺ at the same temperature. Furthermore, an in vitro MC3T3-E1 cell culturing study showed significant cell adhesion, distribution, and proliferation in the microwave-sintered scaffolds. These results confirm that microwave sintering has a positive effect on the properties of porous hydroxyapatite scaffolds for bone tissue engineering applications.     

Physical and mechanical properties of a poly-3-hydroxybutyrate-coated nanocrystalline hydroxyapatite scaffold for bone tissue engineering

A major challenge for tissue engineers is the design of scaffolds with appropriate physical and mechanical properties. The present research discusses the formation of ceramic scaffolding in tissue engineering. Hydroxyapatite (HAp) powder was made from bovine bone by thermal treatment at 900?°C; 40, 50 and 60%wt porous HAp was then produced using the polyurethane sponge replication method. Scaffolds were coated with poly-3-hydroxybutyrate (P3HB) for 30?s and 1?min in order to increase the scaffold??s mechanical properties. XRD, SEM and FT-IR were used to study phase structure, morphology and agent groups, respectively. In XRD and FT-IR data, established hydrogen bands between polymer and ceramic matrix confirm that the scaffold is formed as a composite. The scaffold obtained with 50%wt HAp and a 30?s coating was 90% porous, with an average diameter of 100?C400???m, and demonstrated a compressive strength and modulus of 1.46 and 21.27?MPa, respectively. Based on these results, this scaffold is optimised for the aforementioned properties and can be utilised in bone tissue engineering.     

Three​-dimensional porous poly(ε-caprolactone)/beta-tricalcium phosphate microsphere-aggregated scaffold for bone tissue engineering

In this study, porous scaffolds made of polycaprolactone (PCL)/β-tricalcium phosphate (BTCP) biocomposite were fabricated for bone tissue engineering (BTE) applications. The microsphere-aggregated scaffolds were prepared with various BTCP concentrations (10wt%, 20wt%, 50wt%) by the freeze-drying method. The porosity of obtained microsphere-aggregated scaffolds with various pore sizes was 80–85%, where this value was about 70% for the PCL/BTCP (50) sample with no microsphere formation. The results indicated that adding BTCP has enhanced mechanical strength, and the mineralization of PCL/BTCP composite scaffolds has been increased compared to the pure PCL scaffolds in simulated body fluid (SBF). The adhesion and proliferation of mouse bone marrow mesenchymal stem cells (mMSCs) seeded onto PCL/BTCP scaffolds were enhanced compared to the PCL. In addition, in terms of differentiation, the incorporation of BTCP led to increasing the mineral deposition and alkaline phosphatase activity of mMSCs. The synergistic effect of using microsphere-aggregated scaffolds along with BTCP as a reinforcing agent in PCL biocomposite showed that these porous biocomposite scaffolds have the potential application in BTE.     

Indirect casting of patient-specific tricalcium phosphate zirconia scaffolds for bone tissue regeneration using rapid prototyping methodology

Bio-composite scaffolds were fabricated by impregnating 10, 20, 30, 40 and 50% ZrO₂ content with the β-TCP matrix to heal load bearing large size bone defects. The composite scaffolds were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and mechanical testing. The in vitro degradation of scaffolds was calculated by immersing the samples in phosphate buffer saline for a period of 21 days. Biocompatibility was evaluated by XTT assay using human Osteosarcoma cell line (MG-63). Results include scaffold surface morphology, overall porosity, phase transformation, bonding, compressive strength, biodegradability and cytotoxicity with an increase in ZrO₂ percentages. The conclusions proved that β-TCP scaffold with 30% ZrO₂ content exhibits the best-required properties for the application in the field of bone tissue regeneration.