Processing and properties of porous poly(L-lactide)/bioactive glass composites

Porous poly(L-lactide)/bioactive glass (PLLA/BG) composites were prepared by phase separation of polymer solutions containing bioactive glass particles (average particle size: 1.5 microm). The composite microstructures consist of a porous PLLA matrix with glass particles distributed homogeneously throughout. Large pores (>100 microm) are present in a network of smaller (<10 microm) interconnected pores. The porous microstructure of the composites was not significantly influenced by glass content (9 or 29 vol%), but silane pretreatment of the glass resulted in better glass incorporation in the matrix. Mechanical tests showed that an increase in glass content increased the elastic modulus of the composites, but decreased their tensile strength and break strain. Silane pretreatment enhanced the increase in modulus and prevented the decrease in tensile strength with increasing glass content. Composites soaked in simulated body fluid (SBF) at body temperature formed bone-like apatite inside and on their surfaces. The silane pretreatment of glass particles delayed the in vitro apatite formation. This bone-like apatite formation demonstrates the composites' potential for integration with bone.     

Development of bioactive and biodegradable chitosan-based injectable systems containing bioactive glass nanoparticles

There is increasing interest in the development of new tissue engineering strategies to deliver cells and bioactive agents encapsulated in a biodegradable matrix through minimally invasive procedures. The present work proposes to combine chitosan-beta-glycerophosphate salt formulations with bioactive glass nanoparticles in order to conceive novel injectable thermo-responsive hydrogels for orthopaedic reconstructive and regenerative medicine applications. The initial rheological properties and the gelation points of the developed organic-inorganic in situ thermosetting systems were revealed to be adequate for intracorporal injection. In vitro bioactivity tests, using incubation protocols in simulated body fluid (SBF), allowed the observation of bone-like apatite formation in the hydrogel formulations containing bioactive nanoparticles. The density of the apatite formed increased with increasing bioactive glass content and soaking time in SBF. These results indicate that the stimuli-responsive hydrogels could potentially be used as temporary injectable scaffolds in bone tissue engineering applications.     

Plasma-sprayed calcium phosphate particles with high bioactivity and their use in bioactive scaffolds

Highly crystalline feedstock hydroxyapatite (HA) particles with irregular shapes were spheroidized by plasma spraying them onto the surface of ice blocks or into water. The spherical Ca-P particles thus produced contained various amounts of the amorphous phase which were controlled by the stand-off distance between the spray nozzle and the surface of ice blocks or waiter. The smooth surface morphology without cracks of spherical Ca-P particles indicated that there were very low thermal stresses in these particles. Plasma-sprayed Ca-P particles were highly bioactive due to their amorphous component and hence quickly induced the formation of bone-like apatite on their surfaces after they were immersed in an acellular simulated body fluid at 36.5 C. Bone-like apatite nucleated on dissolved surface (due to the amorphous phase) of individual Ca-P particles and grew to coalesce between neighboring Ca-P particles thus forming an integrated apatite plate. Bioactive and biodegradable composite scaffolds were produced by incorporating plasma-spray ed Ca-P particles into a degradable polymer. In vitro experiments showed that plasma-sprayed Ca-P particles enhanced the formation of bone-like apatite on the pore surface of Ca-P/PLLA composite scaffolds.     

Fabrication, characterization, and in vitro degradation of composite scaffolds based on PHBV and bioactive glass

Composite scaffolds of polyhydroxybutyrate-polyhydroxyvalerate (PHBV) with sol-gel-derived bioactive glass (BG, 58S) are fabricated by compression molding, thermal processing, and salt particulate leaching method. Structure and mechanical properties of the scaffolds are determined. The bioactivity of the composites is evaluated by soaking the scaffolds in a simulated body fluid (SBF), and the formation of the apatite layer on the scaffolds is determined by scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS). The results show that the PHBV/BG composites are bioactive as they induce the formation of apatite on the composite scaffolds after soaking in SBF for 3 days. In addition, the measurements of the water contact angles suggest that incorporation of BG into PHBV can improve the hydrophilicity of the composites and the enhancement is dependent on the BG content. Furthermore, the degradation assessment of the scaffolds is performed in phosphate-buffered saline (PBS) solution at 37 C. Weight loss and water absorption of the scaffolds, pH of the incubation media, and molecular weight measurements of the PHBV in the scaffolds are used to monitor the degradation of the scaffolds during a nine-week incubation in PBS. It has been found that the incorporation of bioactive glass into the PHBV delayed the degradation of PHBV in the composite scaffolds for the period investigated. The present results show not only a useful method to prepare composite scaffolds with improved properties but also a way of adjusting the in vitro degradation behavior of composite scaffolds by tailoring the content of bioactive glass.     

A mesoporous bioactive glass/polycaprolactone composite scaffold and its bioactivity behavior

Composite scaffolds of mesoporous bioactive glass (MBG)/polycaprolactone (PCL) and conventional bioactive glass (BG)/PCL were fabricated by a solvent casting-particulate leaching method, and the structure and properties of the composite scaffolds were characterized. The measurements of the water contact angles suggest that the incorporation of either MBG or BG into PCL can improve the hydrophilicity of the composites, and the former is more effective than the later. The bioactivity of the composite scaffold is evaluated by soaking the scaffolds in a simulated body fluid (SBF) and the results show that the MBG/PCL composite scaffolds can induce a dense and continuous layer of apatite after soaking in SBF for 3 weeks, as compared with the scattered and discrete apatite particles on the BG/PCL composite scaffolds. Such improvements (improvements of the hydrophilicity and apatite forming ability) should be helpful for the extensive applications of PCL scaffold in tissue engineering.     

Bioactive glass ceramics: properties and applications

Heat treatment of an MgO-CaO-SiO2-P2O5 glass gave a glass ceramic containing crystalline apatite (Ca10(PO4)6O,F2] and beta-wollastonite (CaO,SiO2) in an MgO-CaO-SiO2 glassy matrix. It showed bioactivity and a fairly high mechanical strength which decreased only slowly, even under load-bearing conditions in the body. It is used clinically as artificial vertebrae, iliac bones, etc. The bioactivity of this glass ceramic was attributed to apatite formation on its surface in the body. Dissolution of calcium and silicate ions from the glass ceramic was considered to play an important role in forming the surface apatite layer. It was shown that some new kinds of bioactive materials can be developed from CaO,SiO2-based glasses. Ceramics, metals and organic polymers coated with bone-like apatite were obtained when such materials were placed in the vicinity of a CaO,SiO2-based glass in a simulated body fluid. A bioactive bone cement which was hardened within 4 min and bonded to living bone, forming an apatite, was obtained by mixing a CaO,SiO2-based glass powder with a neutral ammonium phosphate solution. Its compressive strength reached 80 MPa comparable to that of poly(methyl methacrylate) within 3 d. A bioactive and ferromagnetic glass ceramic containing crystalline magnetite (Fe3O4) in a matrix of CaO,SiO2-based glassy and crystalline phases was obtained by a heat treatment of a Fe2O3-CaO.SiO2-B2O3-P2O5 glass. This glass ceramic was shown to be useful as thermoseeds for hyperthermia treatment of cancer.     

Biomimetic nanofibrous gelatin/apatite composite scaffolds for bone tissue engineering

Mimicking certain features (e.g. nanoscale topography and biological cues) of natural extracellular matrix (ECM) is advantageous for the successful regeneration of damaged tissue. In this study, nanofibrous gelatin/apatite (NF-gelatin/apatite) composite scaffolds have been fabricated to mimic both the physical architecture and chemical composition of natural bone ECM. A thermally induced phase separation (TIPS) technique was developed to prepare nanofibrous gelatin (NF-gelatin) matrix. The NF-gelatin matrix mimicked natural collagen fibers and had an average fiber diameter of about 150 nm. By integrating the TIPS method with porogen leaching, three-dimensional NF-gelatin scaffolds with well-defined macropores were fabricated. In comparison to Gelfoam^® (a commercial gelatin foam) with similar pore size and porosity, the NF-gelatin scaffolds exhibited a much higher surface area and mechanical strength. The surface area and compressive modulus of NF-gelatin scaffolds were more than 700 times and 10 times higher than that of Gelfoam^®, respectively. The NF-gelatin scaffolds also showed excellent biocompatibility and mechanical stability. To further enhance pre-osteoblast cell differentiation as well as improving mechanical strength, bone-like apatite particles (<2 μm) were incorporated onto the surface of NF-gelatin scaffolds via a simulated body fluid (SBF) incubation process. The NF-gelatin/apatite scaffolds 5 days after SBF treatment showed significantly higher mechanical strength than NF-gelatin scaffolds 5 days after SBF treatment. Furthermore, the incorporated apatite in the NF-gelatin/apatite composite scaffold enhanced the osteogenic differentiation. The expression of BSP and OCN in the osteoblast–(NF-gelatin/apatite composite) constructs was about 5 times and 2 times higher than in the osteoblast–(NF-gelatin) constructs 4 weeks after cell culture. The biomimetic NF-gelatin/apatite scaffolds are, therefore, excellent for bone tissue engineering.     

A comparative study of mesoporous glass/silk and non-mesoporous glass/silk scaffolds: physiochemistry and in vivo osteogenesis

Mesoporous bioactive glass (MBG) is a new class of biomaterials with a well-ordered nanochannel structure, whose in vitro bioactivity is far superior than that of non-mesoporous bioactive glass (BG); the material's in vivo osteogenic properties are, however, yet to be assessed. Porous silk scaffolds have been used for bone tissue engineering, but this material's osteoconductivity is far from optimal. The aims of this study were to incorporate MBG into silk scaffolds in order to improve their osteoconductivity and then to compare the effect of MBG and BG on the in vivo osteogenesis of silk scaffolds. MBG/silk and BG/silk scaffolds with a highly porous structure were prepared by a freeze-drying method. The mechanical strength, in vitro apatite mineralization, silicon ion release and pH stability of the composite scaffolds were assessed. The scaffolds were implanted into calvarial defects in SCID mice and the degree of in vivo osteogenesis was evaluated by microcomputed tomography (μCT), hematoxylin and eosin (H&E) and immunohistochemistry (type I collagen) analyses. The results showed that MBG/silk scaffolds have better physiochemical properties (mechanical strength, in vitro apatite mineralization, Si ion release and pH stability) compared to BG/silk scaffolds. MBG and BG both improved the in vivo osteogenesis of silk scaffolds. μCT and H&E analyses showed that MBG/silk scaffolds induced a slightly higher rate of new bone formation in the defects than did BG/silk scaffolds and immunohistochemical analysis showed greater synthesis of type I collagen in MBG/silk scaffolds compared to BG/silk scaffolds.     

Novel bioactive materials with different mechanical properties

Some ceramics, such as Bioglass, sintered hydroxyapatite, and glass-ceramic A-W, spontaneously bond to living bone. They are called bioactive materials and are already clinically used as important bone substitutes. However, compared with human cortical bone, they have lower fracture toughness and higher elastic moduli. Therefore, it is desirable to develop bioactive materials with improved mechanical properties. All the bioactive materials mentioned above form a bone-like apatite layer on their surfaces in the living body, and bond to bone through this apatite layer. The formation of bone-like apatite on artificial material is induced by functional groups, such as Si-OH, Ti-OH, Zr-OH, Nb-OH, Ta-OH, -COOH, and PO(4)H(2). These groups have specific structures revealing negatively charge, and induce apatite formation via formations of an amorphous calcium compound, e.g., calcium silicate, calcium titanate, and amorphous calcium phosphate. These fundamental findings provide methods for preparing new bioactive materials with different mechanical properties. Tough bioactive materials can be prepared by the chemical treatment of metals and ceramics that have high fracture toughness, e.g., by the NaOH and heat treatments of titanium metal, titanium alloys, and tantalum metal, and by H(3)PO(4) treatment of tetragonal zirconia. Soft bioactive materials can be synthesized by the sol-gel process, in which the bioactive silica or titania is polymerized with a flexible polymer, such as polydimethylsiloxane or polytetramethyloxide, at the molecular level to form an inorganic-organic nano-hybrid. The biomimetic process has been used to deposit nano-sized bone-like apatite on fine polymer fibers, which were textured into a three-dimensional knit framework. This strategy is expected to ultimately lead to bioactive composites that have a bone-like structure and, hence, bone-like mechanical properties.     

The effect of oxygen plasma pretreatment and incubation in modified simulated body fluids on the formation of bone-like apatite on poly(lactide-co-glycolide) (70/30)

In this study, biodegradable poly(lactide-co-glycolide) (PLGA) (70/30) films and scaffolds were first treated with oxygen plasma and then incubated in a modified simulated body fluid 1.5SBF0 to prepare a bone-like apatite layer. The formation of the apatite and its influence on osteoblast-like cells growth were investigated. It was found that the bone-like apatite formability of PLGA(70/30) was enhanced by plasma pretreatment. The changes of surface chemistry and surface topography induced by oxygen plasma treatment were both effective for apatite formation. The apatite formability increased with increasing plasma-treating time. Under a treating condition of 20 W for 30 min, oxygen plasma treatment could penetrate into the inner scaffold. After 6 days incubation, the apatite formed in plasma-treated scaffold was better distributed than in untreated scaffold, and the weight and mechanical strength of the plasma-treated scaffold were both enhanced. Compared with PLGA(70/30), the apatite layer formed on oxygen plasma-treated PLGA(70/30) surface enhanced adhesion and proliferation of OCT-1 osteoblast-like cell, but had no significant effect on cell's ALP activity at day 7. A prolonged investigation is being in process to further verify the bone-like apatite effects on osteogenic differentiation.     

Bioabsorbable scaffolds for guided bone regeneration and generation

Several different bioabsorbable scaffolds designed and manufactured for guided bone regeneration and generation have been developed. In order to enhance the bioactivity and potential osteoconductivity of the scaffolds, different bioabsorbable polymers, composites of polymer and bioactive glass, and textured surface structures of the manufactured devices and composites were investigated in in vitro studies and experimental animal models. Solid, self-reinforced polyglycolide (SR-PGA) rods and self-reinforced poly L-lactide (SR-PLLA) rods were successfully used as scaffolds for bone formation in muscle by free tibial periosteal grafts in animal experiments. In an experimental maxillary cleft model, a bioabsorbable composite membrane of epsilon-caprolactone and L-lactic acid 50/50 copolymer (PCL/LLA) film and mesh and poly 96L,4D-lactide (PLA96) mesh were found to be suitable materials for guiding bone regeneration in the cleft defect area. The idea of solid layer and porous layer combined together was also transferred to stiff composite of poly 70L,30DL-lactide (PLA70) plate and PLA96 mesh which structure is introduced. The osteoconductivity of several different biodegradable composites of polymers and bioactive glass (BG) was shown by apatite formation in vitro. Three composites studied were self-reinforced composite of PLA70 and bioactive glass (SR-(PLA70 + BG)), SR-PLA70 plate coated with BG spheres, and Polyactive with BG.     

Beta-CaSiO3/beta-Ca3(PO4)2 composite materials for hard tissue repair: in vitro studies

In this study, a series of beta-CaSiO(3) (CS)/beta-Ca(3)(PO(4))(2) (TCP) composites with different ratios were prepared to produce new bioactive and biodegradable biomaterials for potential bone repair. The mechanical properties of CS-TCP composites increased steadily with the increase of TCP amounts in composites. Formation of bone-like apatite on a range of CS-TCP composites with CS weight percentage ranging from 0 to 100 has been investigated in simulated body fluid (SBF). The presence of bone-like apatite layer on the composite surface after soaking in SBF was demonstrated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and fourier transform infrared reflection spectroscopy (FTIR). The results showed that the apatite formation ability of the CS-TCP composite was enhanced with increasing CS content in the composites. For composites with more than 50% CS contents, the samples were completely covered by a layer of dense bone-like apatite just after 3 days immersion. Dissolution tests in Tris-HCl buffer solution showed obvious differences with different CS contents in composites. The dissolution rate increased with the increase of CS content, which suggested that the solubility of biphasic composites could be tailored by adjusting the initial CS/TCP ratio. In vitro cell experiments showed that higher content of CS phase in composites promoted cell proliferation and differentiation. When the CS amount in the composite increased to 50%, the proliferation rate and ALP activities of osteoblast-like cells showed significant difference compared with pure TCP (p < 0.05). Results of the study suggested that the CS-TCP composites with more than 50% CS content might be promising bone repair materials.     

In vitro bioactivity of akermanite ceramics

In this study, the bone-like apatite-formation ability of akermanite ceramics (Ca2MgSi2O7) in simulated body fluid (SBF) and the effects of ionic products from akermanite dissolution on osteoblasts and mouse fibroblasts (cell line L929) were investigated. In addition, osteoblast morphology and proliferation on the ceramics were evaluated. The results showed that akermanite ceramics possessed bone-like apatite-formation ability comparable with bioactive wollastonite ceramics (CaSiO3) after 20 days of soaking in SBF and the mechanism of bone-like apatite formation on akermanite ceramics is similar to that of wollastonite ceramics. The Ca, Si, and Mg ions from akermanite dissolution at certain ranges of concentration significantly stimulated osteoblast and L929 cell proliferation. Furthermore, osteoblasts spread well on the surface of akermanite ceramics, and proliferated with increasing the culture time. The results showed that akermanite ceramics possess bone-like apatite-formation ability and can release soluble ionic products to stimulate cell proliferation, which indicated good bioactivity.     

Three-dimensional printing of strontium-containing mesoporous bioactive glass scaffolds for bone regeneration

In this study, we fabricated strontium-containing mesoporous bioactive glass (Sr-MBG) scaffolds with controlled architecture and enhanced mechanical strength using a three-dimensional (3-D) printing technique. The study showed that Sr-MBG scaffolds had uniform interconnected macropores and high porosity, and their compressive strength was ∼170 times that of polyurethane foam templated MBG scaffolds. The physicochemical and biological properties of Sr-MBG scaffolds were evaluated by ion dissolution, apatite-forming ability and proliferation, alkaline phosphatase activity, osteogenic expression and extracelluar matrix mineralization of osteoblast-like cells MC3T3-E1. The results showed that Sr-MBG scaffolds exhibited a slower ion dissolution rate and more significant potential to stabilize the pH environment with increasing Sr substitution. Importantly, Sr-MBG scaffolds possessed good apatite-forming ability, and stimulated osteoblast cells’ proliferation and differentiation. Using dexamethasone as a model drug, Sr-MBG scaffolds also showed a sustained drug delivery property for use in local drug delivery therapy, due to their mesoporous structure. Therefore, the 3-D printed Sr-MBG scaffolds combined the advantages of Sr-MBG such as good bone-forming bioactivity, controlled ion release and drug delivery and enhanced mechanical strength, and had potential application in bone regeneration.     

Formation of bone-like apatite on poly(L-lactic acid) fibers by a biomimetic process.

Bone-like apatite coating on poly(L-lactic acid) (PLLA) fibers was formed by immersing the fibers in a modified simulated body fluid (SBF) at 37 degrees C and pH 7.3 after hydrolysis of the fibers in water. The ion concentrations in SBF were nearly 1.5 times of those in the human blood plasma. The apatite was characterized by scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), thin-film X-ray diffraction, and Fourier transform infrared spectroscopy. After 15 days of incubation in SBF, an apatite layer with about 5-6 microm thickness was formed on the surface of the fibers. This apatite had a Ca/P ratio similar to that of natural bone. The mass of apatite coated PLLA fibers increased with extending the incubation time. After 20 days incubation, the fibers increased their mass by 25.8 +/- 2.1%. The apatite coating had no significant effect on the tensile properties of PLLA fibers. In this article, the bone-like apatite coating on three-dimensional PLLA braids was also studied. The motivation for this apatite coating was that it might demonstrate enhanced osteoconductivity in the future studies when they serve as biodegradable scaffolds in tissue engineering.     

多孔磷酸钙陶瓷在动态SBF中类骨磷灰石形成的研究

本实验在模拟体液（SBF）以静止、等于或大于骨骼肌组织内体液正常生理流率（2ml/100ml.min)的流动条件下，研究多孔磷酸钙陶瓷上类骨磷灰石的形成，结果表明，SBF在生理流率（2ml/100ml.min)情况下，材料仅在多孔磷酸钙陶瓷孔隙内部形成类骨磷灰石，静态（0ml/100ml.min)情况下，多孔磷酸钙陶瓷材料表面有类骨磷灰石形成；高于生理流率（10ml/100ml/min)时，表面和断面均无类骨磷灰石形成，但如果增加SBF中的Ca^2 ,HPO4^2-的浓度，则在孔隙内部有类骨磷灰石形成，生理流条件下的结果与多数肌肉内植入磷酸钙陶瓷试验的结果一致。仅在多孔材料内部成骨，这个结果表明，比起通常使用的静态浸泡试验，SBF以生理流率流动的动态体外试验能够更好地模拟类骨 磷灰石生长的体内环境，动态SBF对了解类骨磷灰石形成，进而了解磷酸钙陶瓷在体内诱导成骨机理是十分有用的。     

Three-dimensional printing of hierarchical and tough mesoporous bioactive glass scaffolds with a controllable pore architecture, excellent mechanical strength and mineralization ability

New generation biomaterials for bone regeneration should be highly bioactive, resorbable and mechanically strong. Mesoporous bioactive glass (MBG), a novel bioactive material, has been used to study bone regeneration due to its excellent bioactivity, degradation and drug delivery ability, however, the construction of three-dimensional (3-D) MBG scaffolds (as for other bioactive inorganic scaffolds) for bone regeneration remains a significant challenge due to their inherent brittleness and low strength. In this brief communication we report a new facile method to prepare hierarchical and multifunctional MBG scaffolds with a controllable pore architecture, excellent mechanical strength and mineralization ability for application in bone regeneration by a modified 3-D printing technique using polyvinylalcohol (PVA) as a binder. The method provides a new way to solve commonly existing issues for inorganic scaffold materials, for example, uncontrollable pore architectures, low strength, high brittleness and the requirement for a second sintering at high temperature. The 3-D printed MBG scaffolds obtained possess a high mechanical strength about 200 times that of traditional polyurethane foam templated MBG scaffolds. They have a highly controllable pore architecture, excellent apatite mineralization ability and sustained drug delivery properties. Our study indicates that 3-D printed MBG scaffolds may be an excellent candidate for bone regeneration.     

Bone regeneration in rat calvarial defects implanted with fibrous scaffolds composed of a mixture of silicate and borate bioactive glasses

Previous studies have evaluated the capacity of porous scaffolds composed of a single bioactive glass to regenerate bone. In the present study, scaffolds composed of a mixture of two different bioactive glasses (silicate 13-93 and borate 13-93B3) were created and evaluated for their response to osteogenic MLO-A5 cells in vitro and their capacity to regenerate bone in rat calvarial defects in vivo. The scaffolds, which have similar microstructures (porosity = 58?67%) and contain 0, 25, 50 and 100 wt.% 13-93B3 glass, were fabricated by thermally bonding randomly oriented short fibers. The silicate 13-93 scaffolds showed a better capacity to support cell proliferation and alkaline phosphatase activity than the scaffolds containing borate 13-93B3 fibers. The amount of new bone formed in the defects implanted with the 13-93 scaffolds at 12 weeks was 31%, compared to values of 25, 17 and 20%, respectively, for the scaffolds containing 25, 50 and 100% 13-93B3 glass. The amount of new bone formed in the 13-93 scaffolds was significantly higher than in the scaffolds containing 50 and 100% 13-93B3 glass. While the 13-93 fibers were only partially converted to hydroxyapatite at 12 weeks, the 13-93B3 fibers were fully converted and formed a tubular morphology. Scaffolds composed of an optimized mixture of silicate and borate bioactive glasses could provide the requisite architecture to guide bone regeneration combined with a controllable degradation rate that could be beneficial for bone and tissue healing.     

Calcium phosphate surface treatment of bioactive glass causes a delay in early osteogenic differentiation of adipose stem cells

Human adipose stem cells (ASCs) combined with osteostimulative material provide an attractive approach for clinical bone regeneration. The effect of calcium phosphate (Ca-P) surface treatment of three-dimensional bioactive glass scaffolds on the attachment, proliferation, and osteogenic differentiation of ASCs was studied. Three types of bioactive glass scaffolds (nontreated, thick and thin Ca-P treated) were compared. All scaffold types supported ASC attachment, spreading, and proliferation equally as detected by scanning electron microscopy, fluorescence staining, and DNA measurement. Indices of osteogenic differentiation including the expression of osteopontin and alkaline phosphatase (ALP) were consistently higher in the nontreated and thin Ca-P-treated scaffolds when compared with thick Ca-P-treated scaffolds at 2 weeks. ASCs cultured on nontreated bioactive glass scaffolds showed significantly higher ALP activity when compared with both thin and thick Ca-P-treated scaffolds after 1 week in culture, but these differences equalized between the three scaffolds by the 2-week time point. In conclusion, osteogenic differentiation appears to be delayed on the Ca-P surface-treated scaffolds. This delay is more pronounced with thick Ca-P treatment of the scaffolds.     

Transmission electron microscopic study of interface between bioactive bone cement and bone: comparison of apatite and wollastonite containing glass-ceramic filler with hydroxyapatite and beta-tricalcium phosphate fillers.

We developed a bioactive bone cement that consists of apatite and wollastonite containing glass-ceramic (AW-GC) powder and bisphenol-a-glycidyl methacrylate (Bis-GMA) based resin. In this study, we made three types of cement (designated AWC, HAC, and TCPC) consisting of either AW-GC, hydroxyapatite (HA), or beta-tricalcium phosphate (beta-TCP) powder as the inorganic filler and Bis-GMA based resin as the organic matrix. These cements were implanted into rat tibiae and cured in situ. Specimens were prepared 1, 2, 4, and 8 weeks after the operation and observed using transmission electron microscopy. Each of the bone cements was in direct contact with the bone. In AWC-implanted tibiae, the uncured surface layer of Bis-GMA based resin was completely filled with newly formed bone-like tissue 2 weeks after implantation. The AW-GC particles were surrounded by bone and were in contact with bone through an apatite layer. No intervening soft tissue was seen. In HAC-implanted tibiae, it took 4 weeks for the uncured layer to completely fill with newly formed bonelike tissue. The HA particles were also in contact with bone through an apatite layer. In TCPC-implanted tibiae, it took 8 weeks for the uncured layer to fill with newly formed bone-like tissue. The new bone that formed on the TCPC was not as dense as that on the AWC or HAC, and an intervening apatite layer was not evident. Results indicated that AWC had higher bioactivity than either HAC or TCPC.