Proliferation, differentiation, and calcification of preosteoblast-like MC3T3-E1 cells cultured onto noncrystalline calcium phosphate glass

Vancomycin- and Poly(simvastatin)-Loaded Scaffolds with Time-Dependent Development of Porosity

Biodegradable scaffolds are widely use in drug delivery and tissue engineering applications. The scaffolds can be modified to provide the necessary mechanical support for tissue formation and to deliver one or more drugs to stimulate tissue formation or for the treatment of a specific condition. In the current study, we developed biodegradable scaffolds that have the potential for dual drug delivery. The scaffolds consisted of simvastatin-containing prodrug, poly(simvastatin) entrapped in poly(β-amino ester) (PBAE) porogen particles and vancomycin encapsulated in poly(lactic-co-glycolic acid) (PLGA) microspheres, which were fused together around the PBAE porogens to create a slow-degrading matrix. Upon hydrolysis, poly(simvastatin) releases simvastatin acid, which has angiogenic and osteogenic properties, while the PLGA microspheres release vancomycin as an antibacterial agent. Degradation of PBAE porogens through hydrolysis of ester linkages led to the development of porosity in a controlled manner and led to water penetration that facilitated hydrolysis of PLGA. Higher porogen loading (~60% by weight) gave rise to ~70% interconnected porosity with pore spacing of ~180 μm. This open volume facilitated simvastatin acid release upon hydrolysis and entrapped vancomycin release via diffusion through and degradation of PLGA. During the study, ~162 μg of simvastatin acid and ~18 mg vancomycin were released from the highest porosity scaffolds. Bioactivity studies showed that released simvastatin acid stimulated preosteoblastic activity, indicating that scaffold fabrication did not damage the polymeric prodrug. Regarding mechanical properties, compressive modulus, failure strain, and failure stress decreased with increasing PBAE porogen content. These dual drug releasing scaffolds with controlled development of microarchitecture can be useful in bone tissue engineering applications.

A novel fluorescein-bisphosphonate based diagnostic tool for the detection of hydroxyapatite in both cell and tissue models

A rapid and efficient method for the detection of hydroxyapatite (HAP) has been developed which shows superiority to existing well-established methods. This fluorescein-bisphosphonate probe is highly selective for HAP over other calcium minerals and is capable of detecting lower levels of calcification in cellular models than either hydrochloric acid-based calcium leaching assays or the Alizarin S stain. The probe has been shown to be effective in both in vitro vascular calcification models and in vitro bone calcification models. Moreover we have demonstrated binding of this probe to vascular calcification in rat aorta and to areas of microcalcification, in human vascular tissue, beyond the resolution of computed tomography in human atherosclerotic plaques. Fluorescein-BP is therefore a highly sensitive and specific imaging probe for the detection of vascular calcification, with the potential to improve not only ex vivo assessments of HAP deposition but also the detection of vascular microcalcification in humans.

Egg White Ovotransferrin Shows Osteogenic Activity in Osteoblast Cells

Ovotransferrin, the major protein in egg white, is a member of transferrin family. The objective of this study was to study the effects of ovotransferrin on cell proliferation, differentiation, mineralization and osteoclastogenesis of bone osteoblast cells. Effect of ovotransferrin (concentrations ranging from 1 to 1000 μg/mL) on the proliferation, differentiation, and mineralization of mouse osteoblast cells MC3T3-E1 was determined by 5-bromo-2-deoxyuridine (BrdU) incorporation assay, Western blot, immunofluorescence, and Alizarin-S red staining, respectively. Our results showed that ovotransferrin stimulated cell proliferation (enhanced BrdU incorporation), differentiation (enhanced expression of alkaline phosphatase and type-I collagen), and mineralization (increased calcium deposits) in a dose-dependent manner. Furthermore, ovotransferrin could increase the expression of osteoprotegerin (OPG) while decreasing the expression of receptor activator of nuclear factor kappa-B ligand (RANKL), suggesting its role in inhibition of bone resorption. This study demonstrated for the first time that ovotransferrin might promote bone formation while preventing bone resorption, which might open up a new application of egg white protein ovotransferrin as a functional ingredient in bone health management.

Nanocomposite particles with improved microstructure for 3D culture systems and bone regeneration

Nano-apatite and gelatin-alginate hydrogel microparticles have been prepared by a one-step synthesis combined with electrostatic bead generation, for the reconstruction of bone defects. Based on the analysis of bone composition, architecture and embryonic intramembranous ossification, a bio-inspired fabrication has been developed. Accordingly, the mineral phase has been in situ synthesized, calcifying the hydrogel matrix while the latter was crosslinked, finally generating microparticles that can assemble into a bone defect to ensure interconnected pores. Although nano-apatite-biopolymer composites have been widely investigated, microstructural optimization to provide improved distribution and stability of the mineral is rarely achieved. The optimization of the developed method progressively resulted in two types of formulations (15P and 7.5P), with 15 and 7.5 (wt%) phosphate content in the initial precursor. The osteolytic potential was investigated using differentiated macrophages. A commercially available calcium phosphate bone graft substitute (Eurocer 400) was incorporated into the hydrogel, and the obtained composites were in vitro tested for comparison. The cytocompatibility of the microparticles was studied with mouse osteoblast-like cell line MC3T3-E1. Results indicated the best in vitro performance have been obtained for the sample loaded with 7.5P. Preliminary evaluation of biocompatibility into a critical size (3 mm) defect in rabbits showed that 7.5P nanocomposite is associated with newly formed bone in the proximity of the microparticles, after 28 days.

In vitro and in vivo performance of bioactive Ti6Al4V/TiC/HA implants fabricated by a rapid microwave sintering technique

Failure of the bone-implant interface in a joint prosthesis is a main cause of implant loosening. The introduction of a bioactive substance, hydroxyapatite (HA), to a metallic bone-implant may enhance its fixation on human bone by encouraging direct bone bonding. Ti6Al4V/TiC/HA composites with a reproducible porous structure (porosity of 27% and pore size of 6-89 μm) were successfully fabricated by a rapid microwave sintering technique. This method allows the biocomposites to be fabricated in a short period of time under ambient conditions. Ti6Al4V/TiC/HA composites exhibited a compressive strength of 93 MPa, compressive modulus of 2.9 GPa and microhardness of 556 HV which are close to those of the human cortical bone. The in vitro preosteoblast MC3T3-E1 cells cultured on the Ti6Al4V/TiC/HA composite showed that the composite surface could provide a biocompatible environment for cell adhesion, proliferation and differentiation without any cytotoxic effects. This is among the first attempts to study the in vivo performance of load-bearing Ti6Al4V/TiC and Ti6Al4V/TiC/HA composites in a live rabbit. The results indicated that the Ti6Al4V/TiC/HA composite had a better bone-implant interface compared with the Ti6Al4V/TiC implant. Based on the microstructural features, the mechanical properties, and the in vitro and in vivo test results from this study, the Ti6Al4V/TiC/HA composites have the potential to be employed in load-bearing orthopedic applications.

Gellan gum microgel-reinforced cell-laden gelatin hydrogels

The relatively weak mechanical properties of hydrogels remain a major drawback for their application as load-bearing tissue scaffolds. Previously, we developed cell-laden double-network (DN) hydrogels that were composed of photocrosslinkable gellan gum (GG) and gelatin. Further research into the materials as tissue scaffolds determined that the strength of the DN hydrogels decreased when they were prepared at cell-compatible conditions, and the encapsulated cells in the DN hydrogels did not function as well as they did in gelatin hydrogels. In this work, we developed microgel-reinforced (MR) hydrogels from the same two polymers, which have better mechanical strength and biological properties in comparison to the DN hydrogels. The MR hydrogels were prepared by incorporating stiff GG microgels into soft and ductile gelatin hydrogels. The MR hydrogels prepared at cell-compatible conditions exhibited higher strength than the DN hydrogels and the gelatin hydrogels, the highest strength being 2.8 times that of the gelatin hydrogels. MC3T3-E1 preosteoblasts encapsulated in MR hydrogels exhibited as high metabolic activity as in gelatin hydrogels, which is significantly higher than that in the DN hydrogels. The measurement of alkaline phosphatase (ALP) activity and the amount of mineralization showed that osteogenic behavior of MC3T3-E1 cells was as much facilitated in the MR hydrogels as in the gelatin hydrogels, while it was not as much facilitated in the DN hydrogels. These results suggest that the MR hydrogels could be a better alternative to the DN hydrogels and have great potential as load-bearing tissue scaffolds.

Nano-hydroxyapatite reinforced polyhydroxybutyrate composites: a comprehensive study on the structural and in vitro biological properties

Nanocomposites based on polyhydroxybutyrate (PHB) and hydroxyapatite (HAp) have recently been proposed for application in bone repair and regeneration, but very limited studies have investigated the effect of HAp on the rheological and thermal behavior of PHB. More important, the efficiency of a biomaterial depends greatly on its ability to interact with cells, but little is known about this interaction for this kind of nanocomposite. Hence, this paper dealt with some of the characteristics of solution-casted PHB/HAp nanocomposite films, and tried to explore the effect of HAp nanoparticles on cellular responses. The results showed that both rheological and thermal properties can be tailored by incorporating appropriate amounts of nanoparticles. In vitro studies showed a significant increase in proliferation and differentiation of MC3T3-E1 on nanocomposites compared to the neat polymer. Surface examination indicated that topography and chemistry of surface are important factors influencing cellular processes; while no cell differentiation was found on the neat polymer, nanocomposite with 15 wt.% filler content exhibited a pronounced differentiation resulting from high surface roughness and large amount of exposed HAp. These results suggest that HAp particles play a much more important role in determining the biological performance of PHB than has previously been supposed.

Current views on calcium phosphate osteogenicity and the translation into effective bone regeneration strategies

Calcium phosphate (CaP) has traditionally been used for the repair of bone defects because of its strong resemblance to the inorganic phase of bone matrix. Nowadays, a variety of natural or synthetic CaP-based biomaterials are produced and have been extensively used for dental and orthopaedic applications. This is justified by their biocompatibility, osteoconductivity and osteoinductivity (i.e. the intrinsic material property that initiates de novo bone formation), which are attributed to the chemical composition, surface topography, macro/microporosity and the dissolution kinetics. However, the exact molecular mechanism of action is unknown. This review paper first summarizes the most important aspects of bone biology in relation to CaP and the mechanisms of bone matrix mineralization. This is followed by the research findings on the effects of calcium (Ca²⁺) and phosphate (PO₄³⁻) ions on the migration, proliferation and differentiation of osteoblasts during in vivo bone formation and in vitro culture conditions. Further, the rationale of using CaP for bone regeneration is explained, focusing thereby specifically on the material's osteoinductive properties. Examples of different material forms and production techniques are given, with the emphasis on the state-of-the art in fine-tuning the physicochemical properties of CaP-based biomaterials for improved bone induction and the use of CaP as a delivery system for bone morphogenetic proteins. The use of computational models to simulate the CaP-driven osteogenesis is introduced as part of a bone tissue engineering strategy in order to facilitate the understanding of cell-material interactions and to gain further insight into the design and optimization of CaP-based bone reparative units. Finally, limitations and possible solutions related to current experimental and computational techniques are discussed.

Effects of niobium ions released from calcium phosphate invert glasses containing Nb2O5 on osteoblast-like cell functions

The effects of niobium ions released from 60CaO-30P(2)O(5)-(10-x)Na(2)O-xNb(2)O(5) (mol %, x = 0-10) glasses on MC3T3-E1 cell functions were evaluated by culture tests with two systems; cell culture on glass plates, or in culture media containing glass extracts. Alkaline phosphatase (ALP) activity in the cells cultured on the glass plates containing 3 and 5 mol % of Nb(2)O(5) was significantly higher than that on the Nb(2)O(5)-free glass, although proliferation was not enhanced on all glasses containing Nb(2)O(5). Cells cultured in the medium containing 3 × 10(-7) M niobium ions showed the highest ALP activity in comparison with other Nb-containing media or normal medium, regardless of the presence of osteogenic factors (ascorbic acid, β-glycerophosphate and dexamethasone) in the media. Calcium deposition by the cells cultured in the medium containing 3 × 10(-7) M niobium ions was twice as high as those cultured in medium containing no niobium ions. The effects of niobium ions were thought to depend on ion concentration, and to enhance differentiation and mineralization of osteogenic cells rather than their initial adhesion or proliferation.

Small interfering RNA knocks down the molecular target of alendronate, farnesyl pyrophosphate synthase, in osteoclast and osteoblast cultures

Farnesyl pyrophosphate synthase (FPPS), an enzyme in the mevalonate pathway, is the inhibition target of alendronate, a potent FDA-approved nitrogen-containing bisphosphonate (N-BP) drug, at the molecular level. Alendronate not only inhibits osteoclasts but also has been reported to positively affect osteoblasts. This study assesses the knockdown effects of siRNA targeting FPPS compared with alendronate in both osteoclast and osteoblast cultures. Primary murine bone marrow cell-induced osteoclasts and the preosteoblast MC3T3-E1 cell line were used to assess effects of anti-FPPS siRNA compared with alendronate. Results show that both FPPS mRNA message and protein knockdown in serum-based culture is correlated with reduced osteoclast viability. FPPS siRNA is more potent than 10 μM alendronate, but less potent than 50 μM alendronate on reducing osteoclast viability. Despite FPPS knockdown, no significant changes were observed in osteoblast proliferation. FPPS knockdown promotes osteoblast differentiation significantly but not cell mineral deposition. However, compared with 50 μM alendronate dosing, FPPS siRNA does not exhibit cytotoxic effects on osteoblasts while producing significant effects on ostoblast differentiation. Both siRNA and alendronate at tested concentrations do not have significant effects on cultured osteoblast mineralization. Overall, results indicate that siRNA against FPPS could be useful for selectively inhibiting osteoclast-mediated bone resorption and improving bone mass maintenance by influencing both osteoclasts and osteoblasts in distinct ways.

Osteoconductive effects of calcium phosphate glass cement grafts in rabbit calvarial defects

Calcium phosphate glass (CPG) is well-documented alloplastic bone graft material. The objective of this study was to evaluate the osteoconductive effect of newly developed calcium phosphate glass cement (CPGC) in rabbit calvarial defects. Three circular defects (8 mm diameter) were created on the rabbit calvarium. One defect was filled with biphasic calcium phosphate (BCP group) and one defect was filled with CPGC (CPGC group). The remaining defect was not filled as the control. Histologic and histometric analysis were performed at four and eight weeks following the implantation of materials. One-way ANOVA method was used to evaluated the significance between three groups (p < 0.05). The CPGC group did not show a statistical difference in new bone area compared with the control at all healing periods, but the bone formation rate of CPGC seemed to increase between four and eight weeks. This suggests the bone formation rate of CPGC is initially slow, but increases at a specific time, showing the possibility of greater bone formation with time. The resorption rate of CPGC was greater than BCP. Within the limits of this study, CPGC demonstrated good space maintaining capacity and had an osteoconductive effect, suggesting it could be successfully used to improve bone formation capacity.

Association of collagen with calcium phosphate promoted osteogenic responses of osteoblast-like MG63 cells

In this investigation, the effects of the association of the collagen (COLL) molecules with the calcium phosphate (CaP) film were examined with respect to both the physicochemical properties of the CaP films and the osteoblast responses, such as the adhesion, proliferation, differentiation, and mineralization. The COLL pre-adsorbed CaP film (CaPA) exhibited significant changes in the surface morphology compared to the COLL incorporated CaP film (CaPC). The adhesions of the osteoblast-like MG63 cells were similar on the CaPC or CaPA films. However, the proliferation of the MG63 cells on CaPC was comparable to CaP but considerably different than CaPA. The differentiation of the MG63 cells was greatly improved on CaPC and CaPA compared to CaP and more pronounced on CaPA. The presence of COLL within or on the CaP films significantly modulated the expression of the phenotypic genes, including osteopontin (OPN), alkaline phosphatase (ALP), and the transforming growth factor-β (TGF-β). The expression patterns of these genes elucidated that COLL that was present within or on the CaP film supported the osteoblast proliferation and differentiation. These positive effects were stronger for CaPA than CaPC. The bone-like nodules formed on all of the specimens. However, the mineralization of CaPC and CaPA was significantly higher than CaP, indicating that the association of CaP with COLL promoted the mineral deposition. Therefore, the association of the COLL molecules with the CaP film induced positive effects on the biomineralization. Overall, the incorporation of COLL efficiently enhanced the osteoblast responses of CaP. This system can be utilized in a drug delivery system using calcium phosphate. Although the incorporation effects were slightly higher for the osteoblast responses of CaPA than CaPC, CaPC can be used when the longer drug release times are desirable.

Effect of CaTiO(3)-CaCO(3) prepared by alkoxide method on cell response

In recent years, calcium titanate (CaTiO(3)) and carbon-containing materials have gained much attention in a number of biomedical material researches. To maximize the advantages of both materials, we developed a novel alkoxide method to get "calcium titanate with calcium carbonate" (CaTiO(3)-CaCO(3)). The objective was to evaluate the crystallinity and elemental composition of CaTiO(3)-CaCO(3) prepared by alkoxide method, CaTiO(3)-aC elaborated by modified thermal decomposition method, commercially-prepared CaTiO(3), and the effect of these materials on the bone marrow stromal cell. Hydroxyapatite was used as positive control material. We examined the cellular proliferation, osteoblastic differentiation, and mineralization of KUSA/A1 cells cultured with the materials. The results showed that CaTiO(3)-CaCO(3) and CaTiO(3)-aC contained evidence of calcium carbonate enhancing cell proliferation, osteoblastic differentiation, and mineralization. On the contrary, the commercially-prepared CaTiO(3) revealed absence of calcium carbonate with lower cell response than the other groups. The results indicated that calcium carbonate could play a key role in the cell response of CaTiO(3) material. In conclusion, our findings suggest that CaTiO(3)-CaCO(3) could be considered an important candidate as a biomaterial for medical and dental applications.

The effects of hydroxyapatite/calcium phosphate glass scaffold and its surface modification with bovine serum albumin on 1-wall intrabony defects of beagle dogs: a preliminary study

The purpose of this study was to evaluate the effects of biphasic hydroxyapatite/calcium phosphate glass (HA/CPG) scaffold and its surface modification with bovine serum albumin (BSA) on periodontal regeneration. 1-wall intrabony defects were surgically created on five beagle dogs. HA/CPG scaffolds, with a hydroxyapatite (HA)/calcium phosphate glass (CPG) ratio of 95:5 by weight (%) and surface modification done by 2% bovine serum albumin, were used. The control group received surgical flap operation, and the experimental groups were filled with HA/CPG scaffolds and HA/CPG(BSA) scaffolds. The animals were sacrificed eight weeks after surgery. Histological findings revealed better space maintenance in the experimental groups than the control group, and showed new bone formation intermittently in between the residual material particles. The newly formed bone was mostly woven bone and the residual particles were undergoing resorption. Cementum regeneration was observed with limited root resorption in all the groups. Histometric analysis also revealed greater mean values in new bone formation, cementum regeneration and bone area than the control group in both experimental groups. However, similar findings were presented between HA/CPG and HA/CPG(BSA). The result of the present study revealed the newly fabricated HA/CPG scaffold to have a potential use as a bone substitute material.

Proliferation and differentiation of human osteoblasts within 3D printed poly-lactic-co-glycolic acid scaffolds

Bone repair and regeneration can be enhanced through implantation of biocompatible and biodegradable scaffolds, which serve primarily as osteoconductive moieties. In this study, the mechanical properties and microenviroment of 3D printed poly-lactic-co-glycolic acid (PLGA) scaffolds are examined. Additionally, the proliferation and differentiation of human fetal osteoblasts are evaluated after 3 weeks of in vitro culture on the scaffolds. The results showed that the PLGA scaffolds examined had mechanical properties similar to that of trabecular bone, but was still much weaker compared to cortical bone. In addition to general porosity, the PLGA scaffolds also had micropores within macropore walls. Cultured human osteoblasts could proliferate upon seeding on the PLGA scaffolds. Alkaline phosphatase activity and osteonectin expression of the osteoblasts cultured on the PLGA scaffolds remained stable over three weeks, whilst expression of collagen type I and osteopontin decreased. The alkaline phosphatase activity of osteoblasts cultured on PLGA scaffolds is comparable with that from two commercially-available scaffolds - OPLA and collagen scaffolds (Becton-Dickinson (BD) Inc., Franklin Lakes, NJ, USA). Hence, the results suggested that the PLGA scaffolds examined are conducive for promoting osteogenesis.

Effect of Calcium Phosphate Glass on Proliferation and Differentiation of MG-63 Cells in HA Scaffolds

This study examined the possibility of synthesis of biphasic calcium phosphate by sintering a mixture of hydroxyapatite and calcium phosphate glass. The effect of the concentration of calcium phosphate glass in a mixture on the proliferation and differentiation of MG-63 preosteoblast-like cells in a hydtoxyapatite scaffold was investigated. The addition of 5 wt% of calcium phosphate glass significantly improved the level of attachment, proliferation and differentiation of MG-63 cells onto the hydroxyapatite scaffolds, particularly when the surface was modified with 2% bovine serum albumin (p<0.05). Under these conditions, type I collagen was expressed and the extracellular matrix was formed by 1 week, and the ALP gene was expressed at 4 weeks.

Effect of calcium phosphate glass on bone formation in calvarial defects of Sprague-Dawley rats

The purpose of this study was to investigate the bone regenerative effect of calcium phosphate glass in vivo. We prepared two different sizes of calcium phosphate glass powder using the system CaO-CaF2-P2O5-MgO-ZnO; the particle size of the powders were 400 microm and 40 microm. 8 mm calvarial critical-sized defects were created in 60 male Sprague-Dawley rats. The animals were divided into 3 groups of 20 animals each. Each defect was filled with a constant weight of 0.5 g calcium phosphate glass powder mixed with saline. As controls, the defect was left empty. The rats were sacrificed 2 or 8 weeks after postsurgery, and the results were evaluated using radiodensitometric and histological studies; they were also examined histomorphometrically. When the bigger powders with 400 microm particle were grafted, the defects were nearly completely filled with new-formed bone in a clean healing condition after 8 week. When smaller powders with 40 microm particle were transplanted, new bone formation was even lower than the control group due to a lot of inflammatory cell infiltration. It was concluded that the prepared calcium phosphate glass enhanced the new bone formation in the calvarial defect of Sprague-Dawley rats and it is expected to be a good potential materials for hard tissue regeneration. The particle size of the calcium phosphate was crucial; 400 microm particles promoted new bone formation, while 40 microm particles inhibited it because of severe inflammation.

Does seeding density affectin vitro mineral nodules formation in novel composite scaffolds?

This study investigated the human alveolar osteoblasts (AOs) proliferation and extracellular matrix formation at seeding density of 0.05, 0.1, 0.2, 0.4, and 0.8 million (M) per 3x4x4 mm3 on medical grade polycaprolactone-tricalcium phosphate (mPCL-TCP) scaffolds designed for bone regeneration. Over 80-90% of the initial seeded cells were retained in the scaffolds after 24 h. AOs bridged over pores at density of 0.2M/scaffold and below, but formed cell balls at density of 0.4M/scaffold and above. At seeding density of 0.2M and below, cell proliferation increased with time having DNA content peaked to 1600 ng/scaffold at day 21 and 28, respectively, whereas at 0.4 and 0.8M, the corresponding DNA content decreased to 1600 ng in 28 days. At day 7, higher alkaline phosphatase (ALP) activity and higher osteocalcin (OCN) secretion were detected at 0.2M/scaffold and below. After 28 days, multilayered cell-sheet formation and collagen fibers were observed at all densities. ALP and OCN in matrix and mineral nodules were found mainly at the border of AOs-scaffold construct. These findings demonstrated that the density of 0.2M and below per 3 x 4 x 4 mm(3) scaffold resulted in better cell proliferation and extracellular matrix synthesis, potentially resulting in better mineralized tissue formation.

Osteoblast-like cell attachment to and calcification of novel phosphonate-containing polymeric substrates

In an attempt to interact natural bone and bone cells with biomaterials and to begin to develop modular tissue engineering scaffolds, substrates containing phosphonate groups were identified to mimic mineral-protein and natural polymer-protein interactions. In this study, we investigated poly(vinyl phosphonic acid) copolymer integration with existing materials as a graft-copolymer surface modification. Phosphonate-containing copolymer-modified surfaces were created and shown to have varying phosphate content within different polymeric surfaces. As the phosphonate content in the monomer feed approached 30% vinyl phosphonic acid, increased osteoblast-like cell adhesion (3- to 8-fold increase in adhesion) and proliferation (2- to 10-fold increase in proliferation rate) was observed. Since surfaces modified with 30% vinyl phosphonic acid in the feed exhibited a maximal cell adhesion and proliferation (9.4 x 10(4) cells/cm(2)/day), it was hypothesized that this copolymer composition was optimal for protein-polymer interactions. Osteoblast-like cells formed confluent layers and were able to differentiate on all surfaces that contained vinyl phosphonic acid. Most importantly, cells interacting with these surfaces were able to significantly mineralize the surface. These results suggest that phosphonate-containing polymers can be used to integrate biomaterials with natural bone and could be used for tissue engineering applications.

Bone formation in calvarial defects of Sprague-Dawley rats by transplantation of calcium phosphate glass

The purpose of this study was to investigate the bone-regenerative effect of calcium phosphate glass in vivo. We prepared amorphous calcium phosphate glass powder having a mean particle size of 400 microm in the system CaO-CaF2-P2O5-MgO-ZnO. Calvarial critical-sized defects (8 mm) were created in 60 male Sprague-Dawley rats. The animals were divided into an experimental group and control group of 30 animals each. Each defect was filled with a constant weight of 0.5 g calcium phosphate glass powder mixed with saline. As a control, the defect was left empty. The rats were sacrificed 2, 4, or 8 weeks postsurgery, and the results evaluated using radiodensitometric and histological studies; they were also examined histomorphometrically. When the calcium phosphate glass powders with 400-microm particles were grafted, the defects were nearly completely filled with new-formed bone in a clean healing condition after 8 weeks. It was observed that the prepared calcium phosphate glass enhanced new bone formation in the calvarial defect of Sprague-Dawley rats and could be expected to have potential for use as a hard tissue regeneration material.