Development and in vitro characterisation of novel bioresorbable and bioactive composite materials based on polylactide foams and Bioglass for tissue engineering applications

Bioactive and bioresorbable composite materials were fabricated using macroporous poly(DL-lactide) (PDLLA) foams coated with and impregnated by bioactive glass (Bioglass) particles. Stable and homogeneous Bioglass coatings on the surface of PDLLA foams as well as infiltration of Bioglass particles throughout the porous network were achieved using a slurry-dipping technique in conjunction with pre-treatment of the foams in ethanol. The quality of the bioactive glass coatings was reproducible in terms of thickness and microstructure. Additionally, electrophoretic deposition was investigated as an alternative method for the fabrication of PDLLA foam/Bioglass composite materials. In vitro studies in simulated body fluid (SBF) were performed to study the formation of hydroxyapatite (HA) on the surface of PDLLA/Bioglass composites. SEM analysis showed that the HA layer thickness rapidly increased with increasing time in SBF. The high bioactivity of the PDLLA foam/Bioglass composites indicates the potential of the materials for use as bioactive, resorbable scaffolds in bone tissue engineering.     

PDLLA/Bioglass composites for soft-tissue and hard-tissue engineering: an in vitro cell biology assessment

The aim of this study was to examine the effect of increased content of 45S5 Bioglass (0-40 wt%) in poly(dl-lactic acid) (PDLLA) porous foams on the behaviour of MG-63 (human osteosarcoma cell line) and A549 cells (human lung carcinoma cell line). The ability of these cell lines to grow on bioactive composites was quantitatively investigated in order to assess the potentiality for their use in hard and soft-tissue engineering. Two hours after cell seeding, an increase of cell adhesion according to the increased content of Bioglass((R)) present in the foams for both cell types was observed. Cell proliferation studies performed over a period of 4 weeks showed a better aptitude of the A549 cells to proliferate on PDLLA foams containing 5 wt% Bioglass when compared to the proliferation on foams with 40 wt% Bioglass. A lower proliferation rate was obtained for cells on pure PDLLA. Scanning electron microscopy analysis showed for both cell types the presence of cells inside the porous structure of the foams. These results confirmed the biocompatibility of PDLLA/Bioglass composite foams and the positive effect of Bioglass on MG-63 cell behaviour and also showed for the first time the possibility for human lung epithelial type II cells to adhere and proliferate on these porous scaffolds. In addition, we describe a positive effect of 45S5 Bioglass on A549 cell behaviour in a dose-dependent manner, indicating the potential of using PDLLA/Bioglass composites with an optimal concentration of 45S5 Bioglass not only in bone tissue engineering but also in lung tissue engineering.     

Preparation,characterization, and in vitro degradation of bioresorbable and bioactive composites based on Bioglass-filled polylactide foams

Highly porous poly(D,L-lactide)/Bioglass composites scaffolds were prepared by thermally induced phase separation process of polymer solutions and subsequent solvent sublimation. A series of composite foams with different polymer/Bioglass weight ratios was prepared to study the influence of Bioglass content on the foam characteristics such as porous structure, density, and pore volume. The pore volume was decreased from 9.5 to 5.7 cm(3)/g when the Bioglass content was increased up to 40 wt %, but the overall pore morphology was not affected very much by changing the polymer/glass composition ratio. The composites foams were then incubated in phosphate-buffered saline at 37 degrees C to study the in vitro degradation of the polymer and to detect hydroxyapatite (HA) formation as an indication of their bioactivity. The addition of Bioglass to polymer foams increased the water absorption and weight loss as compared with pure polymer foams. However, the polymer molecular weight, determined by size exclusion chromatography, was found to decrease more rapidly and to a larger extent in absence of Bioglass. This delayed degradation rate in the composite foams was probably caused by the dissolution of alkaline ions from the Bioglass, resulting in a buffering effect of the incubation medium. After incubation for 7 days, HA was detected by X-ray diffractometry and Raman spectroscopy and confirmed by environmental scanning electron microscopy and energy-dispersive X-ray analysis. The porous composites developed here are promising materials for bone regeneration applications because the formation of HA on the surface of the pore walls should provide good environment for the adhesion and proliferation of osteoblasts and osteoprogenitor cells.     

Three-dimensional culture of annulus fibrosus cells within PDLLA/Bioglass composite foam scaffolds: assessment of cell attachment, proliferation and extracellular matrix production

The objective of the present study was to assess cell attachment, proliferation and extracellular matrix (ECM) production by bovine annulus fibrosus (BAF) cells cultured in vitro in PDLLA/Bioglass composite foams. PDLLA foams incorporated with different percentages (0, 5 and 30wt%) of Bioglass particles were prepared by thermally induced phase separation (TIPS) process and characterized by scanning electron microscopy (SEM). BAF cell morphology and attachment within the PDLLA/Bioglass foams were analysed using SEM. An assessment of cell proliferation was conducted using the WST-1 assay. The amount of sulphated glycosaminoglycans (sGAG) were quantified using the 1,9-dimethylmethylene blue (DMMB) assay after 4 weeks in culture. Furthermore, the amount of collagen synthesis was determined using a hydroxyproline assay, and the presence of collagen types I and II was investigated using Western blotting. Our results reveal that PDLLA/Bioglass foam scaffolds can provide an appropriate microenvironment for BAF cell culture which enhances cell proliferation and promotes the production of sGAG, collagen type I and collagen type II. These findings provide preliminary evidence for the use of PDLLA/Bioglass composite scaffolds as cell-carrier materials for future treatments of intervertebral discs with damaged AF regions.     

Cell viability, proliferation and extracellular matrix production of human annulus fibrosus cells cultured within PDLLA/Bioglass composite foam scaffolds in vitro

The objective of this study was to assess cell viability, attachment, morphology, proliferation, and collagen and sulphated glycosaminoglycan (s-GAG) production by human annulus fibrosus (HAF) cells cultured in vitro in poly(d,l-lactide) (PDLLA)/Bioglass composite foams. PDLLA foams with different percentages (0, 5 and 30wt.%) of Bioglass particles were prepared by thermally induced phase separation (TIPS) and characterized by scanning electron microscopy (SEM). HAF cell viability in the PDLLA/Bioglass foam was analysed using Live/Dead staining. HAF cell attachment was observed using SEM. An assessment of cell proliferation was conducted using the WST-1 assay. The level of s-GAG and collagen produced by HAF cells was quantified using the 1,9-dimethylmethylene blue (DMMB) assay and Sircoltrade mark assay after 4 weeks of culture. The presence of collagen types I and II within the PDLLA/Bioglass composite foams was analysed using immunohistochemistry. Live/dead staining showed that many viable HAF cells were present on the top surface of the foams as well as penetrating into the internal pore structure, suggesting that the PDLLA/Bioglass composite materials are non-toxic and that the presence of Bioglass particles within PDLLA scaffolds does not inhibit HAF cell growth. The SEM observations revealed that more clusters of HAF cells were attached to the pore walls of both the PDLLA/5BG foam and the PDLLA/30BG foam when compared with the PDLLA/0BG foam. WST-1 assay performed over a period of 4 weeks showed an increased tendency of HAF cells to proliferate within both the PDLLA/5BG foam and the PDLLA/30BG foam when compared with both the tissue culture plastic control and the PDLLA/0BG foam, indicating the presence of Bioglass in the foam has a positive effect on HAF cell proliferation. Sircoltrade mark and DMMB assays showed that HAF cells cultured within the PDLLA/30BG foam had a greater ability to deposit collagen and proteoglycan when compared with the control and the PDLLA/0BG foam after 4 weeks in culture, suggesting that the increase of Bioglass content may induce microenvironmental changes which promote the production of extracellular matrix containing abundant collagen and s-GAG. The immunohistochemical analysis of collagen production demonstrated that collagen produced in all cultures was predominantly of type I. These findings provide preliminary evidence for the use of PDLLA/Bioglass composite as cell-carrier materials for future treatments of the intervertebral disc with damaged AF region.     

聚DL-乳酸/磷酸盐复合多孔支架材料的制备及降解性能

采用溶液浇铸 -颗粒滤除法制备了聚 DL-乳酸 (PDL L A) ,聚 DL-乳酸 /羟基磷灰石 (PDL L A/ 2 0 wt%HA)、及聚 DL-乳酸 / β-磷酸三钙 (PDL L A/ 2 0 wt% β- TCP)复合多孔支架材料。研究了支架材料在体外降解中压缩强度、分子量、质量及水解液的 p H值变化规律。结果显示 :复合多孔支架中 HA和 β- TCP均匀分布在 PDL L A基质中 ,复合支架的孔隙率可达 84 % ,磷酸盐微粒的加入对多孔支架的孔隙率有一定的影响 ,但可提高多孔支架的压缩强度 ,并可中和 PDL L A降解所产生的酸性 ,延缓 PDL L A的降解速度。两者相比 ,HA的作用更为明显     

Study of the connectivity properties of Bioglass -filled polylactide foam scaffolds by image analysis and impedance spectroscopy

The porous structure of two series of poly(D,L-lactide)/Bioglass composite foams prepared by thermal-induced phase separation was investigated by image analysis and impedance spectroscopy. Polymer solutions of either low or high molecular weight containing different concentrations (up to 50 wt.%) of Bioglass particles of mean particle size d < 5 microm were studied. The morphology of both macro- and micropores was studied by scanning electron microscopy and image analysis of both neat and composite foams (containing 10-50 wt.% Bioglass). The pore connectivity of both neat polymer and composite foams was characterized by impedance spectroscopy in relation with their transport properties. The influence of the foam composition (i.e., polymer molecular weight and concentration of Bioglass on pore microstructure was studied using these non-destructive methods. It was found that addition of Bioglass particles has a pronounced effect on pore orientation, leading to increasing loss of order of pore structure, especially for low-molecular weight PDLLA foams.     

Three-dimensional macroporous calcium phosphate bioceramics with nested chitosan sponges for load-bearing bone implants

Three-dimensional macroporous calcium phosphate bioceramics embedded with porous chitosan sponges were synthesized to produce composite scaffolds with high mechanical strength and a large surface/volume ratio for load-bearing bone repairing and substitutes. The macroporous calcium phosphate bioceramics with pore diameters of 300 microm to 600 microm were developed using a porogen burnout technique, and the chitosan sponges were formed inside the pores of the bioceramics by first introducing chiosan solution into the pores followed by a freeze-drying process. Our scanning electron microscopy results showed that the pore size of chitosan sponges formed inside the macroporous structure of bioceramics was approximately 100 microm, a structure favorable for bone tissue in-growth. The compressive modulus and yield stress of the composite scaffolds were both greatly improved in comparison with that of HA/beta-TCP scaffolds. The simulated body fluid (SBF) and cell culture experiments were conducted to assess the bioactivity and biocompatibility of the scaffolds. In the SBF tests, a layer of randomly oriented needle-like apatite crystals formed on the scaffold surface after sample immersion in SBF, which suggested that the composite material has good bioactivity. The cell culture experiments showed that MG63 osteoblast cells attached to the composite scaffolds, proliferated on the scaffold surface, and migrated onto the pore walls, indicating good cell biocompatibility of the scaffold. The cell differentiation on the composite scaffolds was evaluated by alkaline phosphatase (ALP) assay. Compared with the control in tissue culture dishes, the cells had almost the same ALP activity on the composite scaffolds during the first 11 days of culture.     

Bioactive and mechanically strong Bioglass-poly(D,L-lactic acid) composite coatings on surgical sutures

New coating processes have been investigated for degradable (Vicryl) and nondegradable (Mersilk) sutures with the aim to develop Bioglass coated polymer fibers for wound healing and tissue engineering scaffold applications. First, the aqueous phase of a Bioglass particle slurry was replaced with a poly(D,L-lactic acid) (PDLLA) polymer dissolved in solvent dimethyle carbonate (DMC) to act as third phase. SEM observations indicated that this alteration significantly improved the homogeneity of the coatings. Second, a new coating strategy involving two steps was developed: the sutures were first coated with a Bioglass-PDLLA composite film followed by a second PDLLA coating. This two-step process of coating has addressed the problem of poor adherence of Bioglass particles on suture surfaces. The coated sutures were knotted to determine qualitatively the mechanical integrity of the coatings. The results indicated that adhesion strength of coatings obtained by the two-step method was remarkably enhanced. A comparative assessment of the bioactivity of one-step and two-step produced coatings was carried out in vitro using acellular simulated body fluid (SBF) for up to 28 days. Coatings produced by the two-step process were found to have similar bioactivity as the one-step produced coatings. The novel Bioglass/PDLLA/Vicryl and Bioglass/PDLLA/Mersilk composite sutures are promising bioactive materials for wound healing and tissue engineering applications.     

Porous poly(alpha-hydroxyacid)/Bioglass composite scaffolds for bone tissue engineering. I: Preparation and in vitro characterisation

Highly porous composites scaffolds of poly-D,L-lactide (PDLLA) and poly(lactide-co-glycolide) (PLGA) containing different amounts (10, 25 and 50 wt%) of bioactive glass (45S5 Bioglass)were prepared by thermally induced solid-liquid phase separation (TIPS) and subsequent solvent sublimation. The addition of increasing amounts of Bioglass into the polymer foams decreased the pore volume. Conversely, the mechanical properties of the polymer materials were improved. The composites were incubated in phosphate buffer saline at 37 degrees C to study the in vitro degradation of the polymer by measurement of water absorption, weight loss as well as changes in the average molecular weight of the polymer and in the pH of the incubation medium as a function of the incubation time. The addition of Bioglass to polymer foams increased the water absorption and weight loss compared to neat polymer foams. However, the polymer molecular weight, determined by size exclusion chromatography, was found to decrease more rapidly and to a larger extent in absence of Bioglass. The presence of the bioactive filler was therefore found to delay the degradation rate of the polymer as compared to the neat polymer foams. Formation of hydroxyapatite on the surface of composites, as an indication of their bioactivity, was recorded by EDXA, X-ray diffractometry and confirmed by Raman spectroscopy.     

聚DL-乳酸/羟基磷灰石复合材料修复长骨缺损的实验研究

目的 :评价羟基磷灰石 (HA)复合聚DL 乳酸 (PDLLA )制备的材料体内成骨能力。方法 :将PDLLA和PDLLA/HA( 2 0wt % )材料采用盐结晶颗粒沥滤法制成三维多孔材料 ,45例 1cm兔桡骨去骨膜缺损分为三组 ,分别植入 2种材料和作空白对照 ,术后 2 ,4,8,12周行X线、组织学及扫描电镜观察骨生成状况 ,8、12周行生物力学测试 (三点折弯强度 )。结果 :泡沫状PDLLA/HA ( 2 0wt % )材料比纯PDLLA成骨更好 (P <0 .0 5 ) ,实验组与对照组相比差异有显著性 (P <0 .0 5 )。结论 :PDLLA具有良好的生物相容性 ,制成多孔状具有较好的骨传导性能 ,HA( 2 0wt % )的加入促进了多孔PDLLA的骨传导能力 ,提高了骨生成的质量。PDLLA/HA( 2 0wt % )复合材料是一种有临床应用前景的骨移植材料。     

Poly(D,L-lactic acid) coated 45S5 Bioglass-based scaffolds: processing and characterization

A comparative investigation has been carried out on the mechanical properties and bioactivity of Bioglass-based foams, before and after applying a poly(D,L-lactic acid) (PDLLA) coating layer on the foam struts. It was found that the bioactivity of foams upon immersion in simulated body fluid (SBF) was maintained in the PDLLA-coated foams; however, the transformation kinetics in SBF of the crystalline phase (Na(2)Ca(2)Si(3)O(9)) in the foam struts to an amorphous calcium phosphate phase was retarded by PDLLA coating. The compressive and three-point bending strengths of the Bioglass-based foams were slightly improved by the PDLLA-coating, and the work-of-fracture of the foams was considerably enhanced, as indicated by stress-strain curves. Immersion in SBF for 4 weeks led to a large decrease of the mechanical strength of as-sintered foams decreased (from 0.3 to 0.03 MPa), because of the transformation of the crystalline phase to an amorphous calcium phosphate. On the other hand, the mechanical strength was well-maintained in PDLLA-coated foams after immersion in SBF for 8 weeks. This behavior was attributed to the in-situ formation of a nanocomposite PDLLA/calcium phosphate film on the strut surfaces upon immersion in SBF.     

Preparation,in vitro degradability,cytotoxicity, and in vivo biocompatibility of porous hydroxyapatite whisker-reinforced poly(L-lactide) biocomposite scaffolds

Biodegradable and bioactive scaffolds with interconnected macroporous structures, suitable biodegradability, adequate mechanical property, and excellent biocompatibility have drawn increasing attention in bone tissue engineering. Hence, in this work, porous hydroxyapatite whisker-reinforced poly(L-lactide) (HA-w/PLLA) composite scaffolds with different ratios of HA and PLLA were successfully developed through compression molding and particle leaching. The microstructure, in vitro mineralization, cytocompatibility, hemocompatibility, and in vivo biocompatibility of the porous HA-w/PLLA were investigated for the first time. The SEM results revealed that these HA-w/PLLA scaffolds possessed interconnected pore structures. Compared with porous HA powder-reinforced PLLA (HA-p/PLLA) scaffolds, HA-w/PLLA scaffolds exhibited better mechanical property and in vitro bioactivity, as more formation of bone-like apatite layers were induced on these scaffolds after mineralization in SBF. Importantly, in vitro cytotoxicity displayed that porous HA-w/PLLA scaffold with HA/PLLA ratio of 1:1 (HA-w₁/PLLA₁) produced no deleterious effect on human mesenchymal stem cells (hMSCs), and cells performed elevated cell proliferation, indicating a good cytocompatibility. Simultaneously, well-behaved hemocompatibility and favorable in vivo biocompatibility determined from acute toxicity test and histological evaluation were also found in the porous HA-w₁/PLLA₁ scaffold. These findings may provide new prospects for utilizing the porous HA whisker-based biodegradable scaffolds in bone repair, replacement, and augmentation applications.     

Collagen release kinetics of surface functionalized 45S5 Bioglass-based porous scaffolds

A highly interconnected porous scaffold made from 45S5 Bioglass was fabricated by the polymer replica technique and surface functionalized for protein immobilization. Subsequently rat-tail collagen type I was immobilized on the scaffolds. The protein and ion release rates were determined by UV-vis spectroscopy and ion chromatography, respectively, and the impact on hydroxyapatite (HA) formation on the scaffolds upon immersion in SBF was evaluated. It was discovered that the surface functionalization enhanced the stability of the collagen attachment and stability against the increment of pH in a biological environment, resulting in similar collagen release kinetics in solutions of different pH values. Without the surface modification, collagen release was considerably expedited by the increment of pH in a surrounding solution. It was also found that the collagen immobilization does not effect the formation of carbonated HA on the scaffold surface. The stable collagen attachment to the functionalized scaffold makes this approach potentially suitable for improving cell attachment and thus for enhancing the application potential of the scaffold in tissue engineering.     

In vitro studies of annulus fibrosus disc cell attachment, differentiation and matrix production on PDLLA/45S5 Bioglass composite films

The aim of this study was to investigate the potential of using PDLLA/45S5 (PDLLA--poly(D,L-lactide)) Bioglass composite films for the culture of annulus fibrosus (AF) cells in vitro with a view to a tissue engineering application. PDLLA films incorporated with different percentages (0, 5 and 30 (wt%)) of Bioglass particles were prepared by solvent casting and characterized by scanning electron microscopy (SEM), water contact angle and white-light interferometry. Bovine AF cell morphology and attachment were analysed using SEM. Cytoskeletal organization was determined by actin labelling with FITC-phalloidin using fluorescence microscopy. The amount of sulphated glycosaminoglycan (sGAG) and collagen produced by AF cells were quantified using the 1,9-dimethylmethylene blue (DMMB) and Sircol assays after 4 weeks in culture. Composite films of PDLLA filled with Bioglass are an appropriate substrate for annulus cells and these films promote the production of an extracellular matrix (ECM) containing abundant sGAGs and collagen. These findings provide a basis for the understanding of the production of ECM molecules by cells cultured on 2D PDLLA/45S5 Bioglass composite films. The results will provide new insights into the design and development of composites containing Bioglass and resorbable polymers as scaffolds for intervertebral disc tissue repair.     

Accelerated bonelike apatite growth on porous polymer/ceramic composite scaffolds in vitro

Although biodegradable polymer/ceramic composite scaffolds can overcome the limitations of conventional ceramic bone substitutes, the osteogenic potential of these scaffolds needs to be further enhanced for efficient bone tissue engineering. In this study, bonelike apatite was efficiently coated onto the scaffold surface by using polymer/ceramic composite scaffolds instead of polymer scaffolds and by using an accelerated biomimetic process to enhance the osteogenic potential of the scaffold. The creation of bonelike, apatite-coated polymer scaffold was achieved by incubating the scaffolds in simulated body fluid (SBF). The apatite growth on porous poly(D,L-lactic-co-glycolic acid)/nanohydroxyapatite (PLGA/ HA) composite scaffolds was significantly faster than on porous PLGA scaffolds. In addition, the distribution of coated apatite was more uniform on PLGA/HA scaffolds than on PLGA scaffolds. After a 5-day incubation period, the mass of apatite coated onto PLGA/HA scaffolds incubated in 5 x SBF was 2.3-fold higher than PLGA/HA scaffolds incubated in 1 x SBF. Furthermore, when the scaffolds were incubated in 5 x SBF for 5 days, the mass of apatite coated onto PLGA/HA scaffolds was 4.5-fold higher than PLGA scaffolds. These results indicate that the biomimetic apatite coating can be accelerated by using a polymer/ceramic composite scaffold and concentrated SBF. When seeded with osteoblasts, the apatite-coated PLGA/HA scaffolds exhibited significantly higher cell growth, alkaline phosphatase activity, and mineralization in vitro compared to the apatite-coated PLGA scaffolds. Therefore, the apatite-coated PLGA/HA scaffolds may provide enhanced osteogenic potential when used as scaffold for bone tissue engineering.     

In vivo evaluation of a porous hydroxyapatite/poly-DL-lactide composite for use as a bone substitute

We investigated the biocompatibility, osteoconductivity, and biodegradability of a porous composite of hydroxyapatite (HA) and poly-DL-lactide (PDLLA) implanted into rabbit femoral condyles and compared it with porous HA. Six weeks after implantation, the HA/PDLLA was covered with bone and contacted the bone directly. The amount of newly formed bone in the pores was similar in both materials during the examined period. The newly formed bone in the HA/PDLLA tended to increase over 26 weeks, but that in the HA did not show a significant increase after 12 weeks. By 26 weeks, remodeling of the newly formed bone in the pores was seen and bone marrow tissue was found in the pores of the HA/PDLLA. The porous HA/PDLLA was resorbed much faster than the porous HA. Porous HA/PDLLA was resorbed continuously through bone formation and remodeling. Conversely, porous HA was scarcely resorbed throughout the period. HA/PDLLA is thought to be degraded almost completely after about 1 year, and in this study, porous HA/PDLLA showed excellent osteoconductivity and faster resorption than HA. Therefore, HA/PDLLA might be a desirable material for bone substitutes.     

In vitro and in vivo analysis of macroporous biodegradable poly(D,L-lactide-co-glycolide) scaffolds containing bioactive glass

Recent studies have demonstrated the angiogenic potential of 45S5 Bioglass. However, it is not known whether the angiogenic properties of Bioglass remain when the bioactive glass particles are incorporated into polymer composites. The objectives of the current study were to investigate the angiogenic properties of 45S5 Bioglass particles incorporated into biodegradable polymer composites. In vitro studies demonstrated that fibroblasts cultured on discs consisting of specific quantities of Bioglass particles mixed into poly(D,L-lactide-co-glycolide) secreted significantly increased quantities of vascular endothelial growth factor. The optimal quantity of Bioglass particles determined from the in vitro experiments was incorporated into three-dimensional macroporous poly(D,L-lactide-co-glycolide) foam scaffolds. The foam scaffolds were fabricated using either compression molding or thermally induced phase separation processes. The foams were implanted subcutaneously into mice for periods of up to 6 weeks. Histological assessment was used to determine the area of granulation tissue around the foams, and the number of blood vessels within the granulation tissue was counted. The presence of Bioglass particles in the foams produced a sustained increase in the area of granulation tissue surrounding the foams. The number of blood vessels surrounding the neat foams was reduced after 2 weeks of implantation; however, compression-molded foams containing Bioglass after 4 and 6 weeks of implantation had significantly more blood vessels surrounding the foams compared with foams containing no Bioglass at the same time points. These results indicate that composite polymer foam scaffolds containing Bioglass particles retain granulation tissue and blood vessels surrounding the implanted foams. The use of this polymer composite for tissue engineering scaffolds might provide a novel approach for ensuring adequate vascular supply to the implanted device.     

Novel porous hydroxyapatite prepared by combining H2O2 foaming with PU sponge and modified with PLGA and bioactive glass

Porous hydroxyapatite (HA) scaffolds have been intensively studied and developed for bone tissue engineering, but their mechanical properties remain to be improved. The aim of this study is to prepare HA-based composite scaffolds that have a unique macroporous structure and special struts of a polymer/ceramic interpenetrating composite and a bioactive coating. A novel combination of a polyurethane (PU) foam method and a hydrogen peroxide (H(2)O( 2)) foaming method is used to fabricate the macroporous HA scaffolds. Micropores are present in the resulting porous HA ceramics after the unusual sintering of a common calcium phosphate cement and are infiltrated with the poly(D,L-lactic-co-glycolic acid) (PLGA) polymer. The internal surfaces of the macropores are further coated with a PLGA-bioactive glass composite coating. The porous composite scaffolds are characterized in terms of microstructure, mechanical properties, and bioactivity. It is found that the HA scaffolds fabricated by the combined method show high porosities of 61-65% and proper macropore sizes of 200-600 microm. The PLGA infiltration improved the compressive strengths of the scaffolds from 1.5-1.8 to 4.0-5.8 MPa. Furthermore, the bioactive glass-PLGA coating rendered a good bioactivity to the composites, evidenced by the formation of an apatite layer on the sample surfaces immersed in the simulated body fluid (SBF) for 5 days. The porous HA-based composites obtained from this study have suitable porous structures, proper mechanical properties, and a high bioactivity, and thus finds potential application as scaffolds for bone tissue engineering.     

Preparation and characterization of collagen-hydroxyapatite composite used for bone tissue engineering scaffold

In this study, highly porous collagen-HA scaffolds were prepared by solid-liquid phase separation method. Microstructure of the composites was characterized by SEM, TEM and XRD. The results show that collagen-HA scaffolds are porous with three-dimension interconnected fiber microstructure, pore sizes are 50-150 microm, and HA particles are dispersed evenly among collagen fiber. Compared with pure collagen, the mechanical property of collagen-HA composite improves significantly. To gain further insight into cell growth throughout 3D scaffolds, the cell proliferation and attachment on the scaffold in vitro was investigated. The collagen-HA composite has good biocompatibility, and adding HA does not affect the histocompatibility of the scaffold materials. The porous collagen-HA composite is suitable as scaffold used for bone tissue engineering.