Effect of carbonate substitution on the ultrastructural characteristics of hydroxyapatite implants

Carbonate ion substitution has been shown to be beneficial for increasing the amount of in vivoosseointegration to hydroxyapatite (HA). Nevertheless, mechanisms by which carbonate ions increase in vivo bioactivity are not fully understood. Sintered granules of HA and carbonate-substituted hydroxyapatite (CHA) were implanted for 6 and 12 weeks in an ovine model. Samples containing the bone-implant interface were prepared for transmission electron microscopy (TEM) and TEM was used to compare the in vivo reactivity of sintered granules of HA and CHA.The current findings demonstrated that CHA (1.2 and 2.05 wt.%) is more soluble than pure HA in vivo. More dissolution was observed from the CHA, at the bone-implant interface and within the implant, when compared to pure HA. A less crystalline phase was formed between the 2.05 wt.% CHA and bone at 12 weeks in vivo. Bone surrounding both the pure HA and 1.2 wt.% CHA was relatively disorganised at 12 weeks. In comparison, bone surrounding the 2.05 wt.% CHA was considerably more organised and in many regions collagen fibrils were present. Despite increased quality of bone surrounding 2.05 wt.% CHA, compared to 1.2 wt.% CHA, the amount of dissolution from both materials was similar.     

Preliminary<Emphasis Type="Italic">in vitro</Emphasis> and<Emphasis Type="Italic">in vivo</Emphasis> characterizations of a sol-gel derived bioactive glass-ceramic system

This study investigates quantitatively and qualitatively the sol-gel derived bioactive glass-ceramic system (BGS)—apatite-wollastonite (AW) type granules in the size range of 0.5–1 mm, as an effective graft material for bone augmentation and restoration. Scanning electron micrographs (SEM) of the sintered granules revealed the rough material surface with micropores in the range 10–30 μm. X-ray diffraction (XRD) pattern of the granules revealed the presence of crystalline phases of the hydroxyapatite and wollastonite, and the functional groups of the silicate and phosphates were identified by Fourier transform infrared spectroscopy (FT-IR). Thein vitro cell culture studies with L929 mouse fibroblast cell line showed very few cells adhered on the BGS disc after 24 h. This could be due to the highly reactive surface of the disc concomitant with the crystallization but not due to the cytotoxicity of the material, since the cellular viability (MTT assay) with the material was 80‰ Cytotoxicity and cytocompatibility studies proved that the material was non-toxic and biocompatible. After 12 weeks of implantation of the BGS granules in the tibia bone of New Zealand white rabbits, the granules were found to be well osteointegrated, as observed in the radiographs. Angiogram with barium sulphate and Indian ink after 12 weeks showed the presence of microcapillaries in the vicinity of the implant site implicating high vascularity. Gross observation of the implant site did not show any inflammation or necrosis. SEM of the implanted site after 24 weeks revealed good osteointegration of the material with the newly formed bone and host bone. New bone was also observed within the material, which was degrading. Histological evaluation of the bone healing with the BGS granules in the tibial defect at all time intervals was without inflammation or fibrous tissue encapsulation. After 2 weeks the new bone was observed as a trabeculae network around the granules, and by 6 weeks the defect was completely closed with immature woven bone. By 12 weeks mature woven bone was observed, and new immature woven bone was seen within the cracks of the granules. After 24 weeks the defect was completely healed with lamellar bone and the size of the granules decreased. Histomorphometrically the area percentage of new bone formed was 67.77% after 12 weeks and 63.37% after 24 weeks. Less bone formation after 24 weeks was due to an increased implant surface area contributed by the material degradation and active bone remodeling. The osteostimulative and osteoconductive potential of the BGS granules was established by tetracycline labelling of the mineralizing areas by 2 and 6 weeks. This sol-gel derived BGS granules proved to be bioactive and resorbable which in turn encouraged active bone formation.     

<Emphasis Type="Italic">In vivo</Emphasis> assessment of hydroxyapatite and silicate-substituted hydroxyapatite granules using an ovine defect model

Phase pure hydroxyapatite (HA) and two silicate-substituted hydroxyapatites (0.8 and 1.5 wt% Si, or 2.6 and 4.9 wt% SiO₄) were prepared by aqueous precipitation methods. The filter-cakes of HA and silicate-substituted hydroxyapatite (SiHA) compositions were processed into granules 1.0–2.0 mm in diameter and sintered at 1200°C for 2 h. The sintered granules underwent full structural characterisation, prior to assessment in an ovine defect model by implantation for a period of 6 and 12 weeks. The results indicate that HA and SiHA implants were well accepted by the host tissue, with no evidence of inflammation. New bone formation was observed directly on the surfaces and in the spaces between the granular implants. Quantitative histomorphometry as determined by the percentage of bone ingrowth and bone coverage for both SiHA implant compositions was significantly greater than that for phase pure HA. These findings indicate that the in vivo bioactivity of hydroxyapatite was significantly improved by the incorporation of silicate ions into the HA structure, making SiHA ceramics attractive alternatives to conventional HA materials for use as bone graft substitute ceramics.     

Histological aspects in bone regeneration of an association with porous hydroxyapatite and bone marrow cells

The osteogenic potential of an association of two kinds of hydroxyapatite (HA) porous ceramics with autologous bone marrow cells cultured with or without dexamethasone (10^-8M) addition in the culture medium and non-cultured rabbit marrow stromal stem cells (MSCs) was tested after 4 weeks of implantation in the dorsal muscles of spine in rabbit. A significantly higher number of rabbits with implants containing bone tissue inside pores were obtained with 10⁷ cells ml^-1 cultured treated with Dex. In the HA porous ceramic using naphtalen as porogen agent, the bone recolonization remains only at the periphery of implants and in the second row of pores, while in the HA porous ceramic using polymethacrylate (PMMA) microbeads as porogen agent, the bone recolonization is observed in the depth of implants. In the PMMA HA group, the Kru¨skal–Wallis variance analysis between the rabbits is significantly different with the percentage of number of occupied pores and occupied pores with bone tissue is different (p < 0.05).     

Osteogenesis of freeze-dried cancellous bone allograft loaded with autologous marrow-derived mesenchymal cells

In this work, we explored the osteogenic potential of freeze-dried cancellous bone allograft loaded with autologous mesenchymal stem cells (MSCs). Human MSCs were isolated, purified and identified. Flow cytometry revealed that the isolated and enriched cells were 90–97% homogeneous and were negative for reactivity to antigens CD34 and CD45 but positive for reactivity to antigen CD44. The expressions of transformation growth factor-β1 (TGFβ1) and basic fibroblast growth factor (bFGF) were detected as positive in freeze-dried cancellous bone allograft using the immunohistochemistry method. The expression of Alkaline Phosphatase (AKP) and Type I collagen mRNA in MSCs, co-cultured in supernatant of allograft, showed a stronger positive than that in hydroxyapatite (HA). After 1 day of incubation, MSCs grew in both surface and inner pores of bone allograft blocks observed by electron microscopy scan. The composites of allograft loaded with MSCs or HA loaded with MSCs were implanted in nude mice subcutaneously. Osteoid and fluorescence labeling were observed in the allograft by the 4th and 6th weeks, respectively, but not at any time in the HA. This study suggests that the freeze-dried cancellous bone allograft would be an ideal choice for the delivery of mesenchymal stem cells for bone tissue engineering applications.     

Bone ingrowth behaviour of hydroxyapatite-coated,polyethylene-intruded and uncoated,sandblasted pure titanium implants in an infected implantation site: an experimental study in miniature pigs

We studied the dynamics of bone tissue ingrowth into the pores of hydroxyapatite-coated (plasma-spraying technique) and uncoated wire meshes of pure Ti in an infected implantation site. Samples of the test materials were implanted into the femora of 15 adult Göttingen minipigs. Just before implantation they were contaminated with Staphylococcus aureus. The pigs were killed after 4, 8, 12 or 24 weeks. Undecalcified ground sections of bone tissue were prepared and stained with toluidine blue for comparative histological evaluation. The hydroxyapatite-coated implants already demonstrated advanced new bone formation after 4 weeks. By 12 weeks most of the implant pores were filled with newly formed bone although all samples showed macro- as well as microscopic signs of persistent infection. Comparable reactions of the uncoated implants could be observed only after 24 weeks. Signs of degradation of the hydroxyapatite coating were seen in contact with soft tissue. This was more extensive in the infected than in the uninfected site. The results and possible clinical consequences are discussed.     

Mechanical and histological evaluations of cobalt-chromium alloy and hydroxyapatite plasma-sprayed coatings in bone

This study evaluated the mechanical and histological behavior of cobalt-chromium (CoCr) alloy and hydroxyapatite (HA) plasma-sprayed coatings in canine cortical bone after 6 and 12 weeks of implantation, using CoCr alloy as the substrate. the substrate was bond-coated with microtextured CoCr alloy coating to ensure adherence between the substrate and top coats. A macrotextured CoCr alloy top coat with surface roughness R _a=34.25±5.50 m was produced to create suitable pores ranging from 25 m to 200 m for bone ingrowth. For HA top coat, a relatively smooth surface (R _a=15.14±3.21 m) was prepared for bone apposition. Shear testing of bone/implant interfaces showed that the CoCr alloy top coat exhibited significantly lower (p<0.01) mean shear strength than the HA top coat at each time interval. The maximum shear strength was 10.88±0.38 MPa for HA-coated implants 12 weeks post-implantation. After histological evaluations, substantial differences in the extent of new bone formation and the types of implant/bone contact were found between two kinds of implants. Direct bone-to-HA coating contact was consistently observed, while a layer of fibrous tissue intervening at the bone-CoCr alloy coating interface was found. Occasionally, partial dissolution of HA coating was seen after 12 weeks of implantation. The results of this study suggested that plasma-sprayed macrotextured CoCr coatings may not be an effective alternative for biological fixation.     

Influence of the porosity of hydroxyapatite ceramics on in vitro and in vivo bone formation by cultured rat bone marrow stromal cells

The in vitro and in vivo osteoblastic differentiation of rat bone marrow stromal cells (MSCs) was assessed on hydroxyapatite disks with 3 different porosities: 30%, 50%, and 70% (HA30, HA50, and HA70, respectively). MSCs obtained by 10-day culture of fresh bone marrow cells were subcultured for 2 weeks on 3 kinds of porous HA disks in the presence and absence of dexamethasone (Dex). After 2 weeks of subculture, alkaline phosphatase (ALP) activity and osteocalcin production of MSCs/HA composites with Dex were higher than those without, and increased with increasing porosity. The resultant bone tissue grafts “cultured-bone/HA constructs” were implanted subcutaneously into the backs of syngeneic rats, and harvested 1, 2, and 4 weeks after implantation. At 1 week, only cultured-bone/HA70 constructs exhibited expanded bone formation. At 2 and 4 weeks, active osteoblasts and progressive bone formation were observed morphologically in both cultured-bone/HA50 and HA70 constructs. At 4 weeks, bone tissue was observed even in cultured-bone/HA30 constructs. ALP activity and osteocalcin production also increased with increasing porosity and time after implantation. In this in vivo model, different scaffold porosity with similar crystal morphology of the apatite phase demonstrated marked differences in ability to support osteogenesis by implanted rat MSCs.     

Enhancement of bone ingrowth in a titanium fiber mesh implant by rhBMP-2 and hyaluronic acid

The present study was designed to evaluate the efficacy of high molecular weight hyaluronic acid (HA) used as a carrier of recombinant human bone morphogenetic protein-2 (rhBMP-2) adsorbed to a titanium fiber mesh implant (TFMI) in vivo. The quantity of HA in the TFMI rapidly decreased during the initial 3-day period after implantation. BMP particles were trapped by the meshwork of HA as observed by scanning electron microscopy (SEM). TFMIs containing LF-6, HA, rhBMP-2, or HA combined with rhBMP-2 were implanted on the cranium of rats. Analysis of digitized SEM images of samples obtained six weeks post-implantation was performed to determine the area occupied by new bone. The area fraction of Ca relative to that of the pores of TFMI in the HA group was larger than that in the Ti group (p<0.05). The area fraction of Ca in both the BMP and HA+BMP groups was larger than that in both the Ti and HA groups (p<0.01), and that in the HA+BMP group was larger than that in the BMP group (p<0.05). It is suggested that HA is not only an effective carrier of BMP, but also it may have a positive effect on the generation of new bone in the TFMI. © 2001 Kluwer Academic Publishers     

Bone tissue formation in sheep muscles induced by a biphasic calcium phosphate ceramic and fibrin glue composite

Some biomaterials are able to induce ectopic bone formation in muscles of large animals. The osteoinductive potential of macro- micro-porous biphasic calcium phosphate (MBCP) ceramic granules with fibrin glue was evaluated by intramuscular implantation for 6 months in six adult female sheep. The MBCP granules were 1–2 mm in size and were composed of hydroxyapatite (HA) and beta-tricalcium phosphate (β-TCP) in a 60/40 ratio. The fibrin glue was composed of fibrinogen, thrombin and other biological factors. After 6 months of implantation in the dorsal muscles of sheep, the explants were rigid. Histology, back-scattered electron microscopy and micro-computed tomography of the implants indicated that approximately 12% of mineralized bone had formed in between the MBCP granules. The ectopic bone appeared well-mineralized with mature osteocytes and Haversian structures. In addition, the number and thickness of bone trabeculae formed in between the MBCP particles were similar to those measured in trabecular bone in sheep. The overall results therefore confirmed the formation of well-mineralized ectopic bone tissue after intramuscular implantation of MBCP/fibrin glue composites. These bone substitutes exhibiting osteoinductive properties could be used for the reconstruction of large bone defects.     

Chitosan-Based Nanocomposite Scaffolds for Tissue Engineering Applications

This article reports the fabrication of three-dimensional porous chitosan and hydroxyapatite (HA)/chitosan composite scaffolds by the thermally induced phase separation (TIPS) technique, for bone tissue engineering. Different amounts of HA nanoparticles (10%, 20%, and 30% g/g) were added to the chitosan solution to produce HA/chitosan composite scaffolds of varying compositions. The morphology and pore structure of the scaffolds vis-à-vis composition were characterized using scanning electron microscopy (SEM) and an energy dispersive X-ray (EDX). Both pure chitosan and HA/chitosan composite scaffolds were highly porous and had interconnected pores. The pore sizes ranged from several micrometers to a few hundred micrometers. The HA nanoparticles were well dispersed and physically coexisted with chitosan in the composite scaffolds. However, some agglomeration of HA nanoparticles was observed on the surface of pore walls when a relatively large amount of HA was used. The composite 3D scaffolds are very promising for use in bone tissue engineering application.     

Evaluation of hydroxyapatite powder coated with collagen as an injectable bone substitute: microscopic study in rabbit

New percutaneous bone filling techniques are beginning to be used by radiologists in bone tumour treatment because they are less agressive than surgery. The possibility of fostering the production of new bone using an injection method by catheter has prompted us to make pure hydroxyapatite (HA) coated with collagen (coll). The aim of this study was to assess three kinds of beads of 100–200 m size by an injectable method in the distal part of femurs in rabbit. Three implanted groups were divided randomly: HA + COLL. group (n: 19); COLL. group (n: 10); HA group (n: 9). At intervals of 2, 4 and 8 weeks after surgery, bone ingrowth was evaluated on low magnification microradiographs (×6.3) by an image analysing computer. This study has shown that bone formation induced by collagen in its isolated form is not as good as when associated with HA granules. At 4 weeks, a significant difference was observed between the three groups, with the lowest bone formation in the COLL. group. However, the amount of bone formation was small and needs to be improved.     

Fabrication of transparent hydroxyapatite and application to bone marrow derived cell/hydroxyapatite interaction observation in-vivo

Transparent hydroxyapatite (HA), 99.6% relative density, was prepared by hot isostatic pressing. Optical transmittance of 1 mm thick HA was greater than 60% at 700 nm. Twenty transparent HA plates (10×7×1 mm) were implanted into the medullary cavities of two dogs' femora. At 1 and 2 weeks after implantation the bone marrow derived cells that adhered to the HA surfaces were histochemically examined by light microscopy and scanning electron microscopy. Four types of enzymatic reactions were employed to identify cell types. Alkaline phosphatase was used as a marker for osteoblasts, acid phosphatase and tartrate-resistant acid phosphatase as a marker for osteoclasts and non-specific esterase as a marker for macrophages. Cells adhered to the HA surfaces were a mixed population of osteoblasts, osteoclasts and macrophages. By 2 weeks, the number of osteoblasts increased and formed a bone-like matrix. A small number of osteoclasts formed resorption lacunae on the HA after 2 weeks. By utilizing the transparency of the HA, whole-view of bone matrix formation by osteoblasts and simultaneous resorption of HA by osteoclasts was observed simply and dynamically by light microscopy.     

Microporosity enhances bioactivity of synthetic bone graft substitutes

This paper describes an investigation into the influence of microporosity on early osseointegration and final bone volume within porous hydroxyapatite (HA) bone graft substitutes (BGS). Four paired grades of BGS were studied, two (HA70-1 and HA70-2) with a nominal total porosity of 70% and two (HA80-1 and HA80-2) with a total-porosity of 80%. Within each of the total-porosity paired grades the nominal volume fraction of microporosity within the HA struts was varied such that the strut porosity of HA70-1 and HA80-1 was 10% while the strut-porosity of HA70-2 and HA80-2 was 20%. Cylindrical specimens, 4.5 mm diameter × 6.5 mm length, were implanted in the femoral condyle of 6 month New Zealand White rabbits and retrieved for histological, histomorphometric, and mechanical analysis at 1, 3, 12 and 24 weeks. Histological observations demonstrated variation in the degree of capillary penetration at 1 week and bone morphology within scaffolds 3–24 weeks. Moreover, histomorphometry demonstrated a significant increase in bone volume within 20% strut-porosity scaffolds at 3 weeks and that the mineral apposition rate within these scaffolds over the 1–2 week period was significantly higher. However, an elevated level of bone volume was only maintained at 24 weeks in HA80-2 and there was no significant difference in bone volume at either 12 or 24 weeks for 70% total-porosity scaffolds. The results of mechanical testing suggested that this disparity in behaviour between 70 and 80% total-porosity scaffolds may have reflected variations in scaffold mechanics and the degree of reinforcement conferred to the bone-BGS composite once fully integrated. Together these results indicate that manipulation of the levels of microporosity within a BGS can be used to accelerate osseointegration and elevate the equilibrium volume of bone.     

Bioglass® Coatings on Biodegradable Poly(3‐hydroxybutyrate) (P3HB) Meshes for Tissue Engineering Scaffolds

Osteoconduction and non‐toxic bioresorbability can be achieved by combining Bioglass® particles and Poly (3‐hydroxybutyrate) (P3HB) fibre meshes in novel composites for tissue engineering scaffolds. Bioglass® coatings readily induce hydroxyapatite (HA) formation on fibre surfaces in vitro, while biodegradable P3HB yields non toxic degradation products. In the present investigation, P3HB meshes were used, which were generated by means of an embroidery technology on the basis of yarns with 12 and 24 filaments with diameters of ～ 30 μm. Bioglass® particles of average particle size < 5 μm were used to produce coatings on P3HB meshes by slurry dipping. By varying the concentration of Bioglass® particles in aqueous slurry, coating thickness and homogeneity could be controlled. Optimally coated meshes were incubated in simulated body fluid (SBF) for 3, 7, 14, and 21 days to detect formation of HA, as a qualitative assessment of bioactivity. Scanning electron microscopy (SEM) observations coupled with X‐ray diffraction analyses revealed the presence of HA crystals on mesh surfaces following 3 days of incubation in SBF. The amount of HA crystals was shown to increase with incubation time in SBF. Minimal polymer degradation was seen after 21 days in SBF, suggesting a suitable time frame for tissue replacement. The novel Bioglass® /P3HB composite meshes developed here are potential materials for bone tissue engineering scaffold applications.     

Hydroxyapatite coating by dipping method,and bone bonding strength

Hydroxyapatite (HA) was coated onto titanium rods by a dip coating method using HA sol. The HA sols were prepared by dispersing HA crystals less than 100 nm length in distilled water or physiological salt solution using an ultrasonic homogenizer. The surface of the HA coating was homogeneous as determined by scanning electron microscopy (SEM). After implantation of uncoated and HA dip coated titanium rods in dog femurs, new bone formation was observed only around the coated material. The bone bonding strength to HA coated rods was 1.0, 1.5, 2.0 and 2.5 Mpa after 1,2,3 and 4 weeks implantation, respectively, as determined by pull-out testing. These values were over twice that of the uncoated titanium rods at 1–4 weeks after implantation. The dip coated titanium exhibited superior biocompatibility to the uncoated implant and may be of great value for bone repacement applications.This paper was accepted for publication after the 1995 Conference of the European Society of Biomaterials, Oporto, Portugal, 10–13 September.     

Preparation of irregular mesoporous hydroxyapatite

An irregular mesoporous hydroxyapatite (meso-HA), Ca₁₀(PO₄)₆(OH)₂, is successfully prepared from Ca(NO₃)₂·4H₂O and NH₄H₂PO₄ using surfactant cetyltrimethyl ammonium bromide (CTAB) as template. Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) results reveal that the positive head of CTAB is assembled on the surface precipitated HA and much NH₄⁺ is enclosed in precipitated HA before calcination. Field scanning electron microscope (FSEM) reveals that there exist many interconnected pores throughout the HA reticular skeleton. Nitrogen adsorption–desorption experiment exhibits a mesoporous material type IV curve, and pore size distribution calculated from the desorption branch of the isotherms based on Barrett–Joyner–Halenda (BJH) model shows that most pores throughout the HA reticular skeleton are sized at about 40 nm, but the pores are not uniform on the whole, owning to decomposition of the “organic” CTAB templating structures and ammonium salt enclosed in the precipitated HA. The specific surface area of irregular meso-HA is calculated to be 37.6 m²/g according to the Brunauer–Emmett–Teller (BET) equation. Moreover, after polylactic acid/meso-HA (PLA/meso-HA) composites degraded 12 weeks in normal saline at 37 °C, the interconnected pores throughout the HA skeleton were enlarged and sized in micron degree, which resemble trabecular bone structure very much.     

Osteogenic effect of hyaluronic acid sodium salt in the pores of a hydroxyapatite scaffold

According to previous reports, a large volume of bone marrow cells (1 × 10⁷ cells/ml) is required for bone regeneration in the pores of a scaffold in vivo. We theorized that immersion of a porous hydroxyapatite (HA) scaffold in hyaluronic acid solution would facilitate bone formation in the scaffold at 1 × 10⁶ cells/ml density of bone marrow cells. The cells were respectively seeded into pores of the cylindrical HA scaffolds with a hollow center after immersion in hyaluronic acid solution or in culture medium. The scaffolds were implanted in the dorsal subcutis of rats for 4 weeks. Thereafter, serially sectioned paraffin specimens were made and observed histologically. Bone formation was observed in many pores of HA scaffold by immersion in hyaluronic acid solution. However, there were no or less pores with new bone formation in the scaffold by immersion in culture medium. The cells were cultured with and without hyaluronic acid in vitro. There was no significant difference in bone formation in vitro with and without hyaluronic acid. The results of this study suggest that hyaluronic acid binds to the cells on the wall of three-dimensional structure and effectively promotes new bone formation.     

Free form fabricated features on CoCr implants with and without hydroxyapatite coating in vivo: a comparative study of bone contact and bone growth induction

The current study evaluates the in vivo response to free form fabricated cobalt chromium (CoCr) implants with and without hydroxyapatite (HA) plasma sprayed coatings. The free form fabrication method allowed for integration of complicated pyramidal surface structures on the cylindrical implant. Implants were press fit into the tibial metaphysis of nine New Zealand white rabbits. Animals were sacrificed and implants were removed and embedded. Histological analysis, histomorphometry and electron microscopy studies were performed. Focused ion beam was used to prepare thin sections for high-resolution transmission electron microscopy examination. The fabricated features allowed for effective bone in-growth and firm fixation after 6 weeks. Transmission electron microscopy investigations revealed intimate bone-implant integration at the nanometre scale for the HA coated samples. In addition, histomorphometry revealed a significantly higher bone contact on HA coated implants compared to native CoCr implants. It is concluded that free form fabrication in combination with HA coating improves the early fixation in bone under experimental conditions.     

Preparation and characterization of bioactive collagen/wollastonite composite scaffolds

A novel biodegradable collagen/wollastonite composite was prepared as three-dimensional scaffolds by freeze-drying method. Scanning electron microscope (SEM) micrographs of scaffolds showed a continuous structure of interconnected pores, and pore size was about 100 m. The tensile strength of the scaffolds was improved by incorporation of wollastonite and the in vitro bioactivity of the scaffolds was evaluated by examining the hydroxyapatite (HA) deposition on their surface in simulated body fluid (SBF). After soaking in SBF for 7 days, collagen reconstituted to fibers and HA nodules formed on collagen fibers. The result suggests that the incorporation of wollastonite could improve the mechanical strength and the in vitro bioactivity of the composite. The scaffolds could be a potential biomaterial for bone tissue engineering.