Evaluation of Time-Dependent Corrosion Inhibition Rate for f-MWCNT-BCP Composite Coatings on 316L Stainless Steel in Simulated Body Fluid for Orthopedic Implantation

A well-developed-multiwall carbon nanotube (f-MWCNT)/biphasic calcium phosphate (BCP) composites were synthesized using ultrasonication method for orthopedic implantation applications. The formation of composites and its phase was confirmed by using X-ray diffraction. The presence of various functional groups was identified by using Fourier transform infra-red (FT-IR) spectroscopy. The presence of f-MWCNT was confirmed by Raman spectroscopy. High-resolution transmission electron microscopy (HR-TEM) analysis revealed that BCP units were bound by the surface of f-MWCNTs. The synthesized composites were coated on medical grade 316L stainless steel substrates using electro deposition technique. To determine its corrosion resistance characteristics, the developed substrates were exposed to a simulated bodily fluid (SBF) solution for 0, 4, and 7 days. These results strongly suggest that the coated composites can be utilized for bone tissue repair.

Biphasic calcium phosphate recruits Tregs to promote bone regeneration

The use of bone substitute materials is crucial for the healing of large bone defects. Immune response induced by bone substitute materials is essential in bone regeneration. Prior research has mainly concentrated on innate immune cells, such as macrophages. Existing research suggests that T lymphocytes, as adaptive immune cells, play an indispensable role in bone regeneration. However, the mechanisms governing T cell recruitment and specific subsets that are essential for bone regeneration remain unclear. This study demonstrates that CD4+ T cells are indispensable for ectopic osteogenesis by biphasic calcium phosphate (BCP). Subsequently, the recruitment of CD4+ T cells is closely associated with the activation of calcium channels in macrophages by BCP to release chemokines Ccl3 and Ccl17. Finally, these recruited CD4+ T cells are predominantly Tregs, which play a significant role in ectopic osteogenesis by BCP. These findings not only shed light on the immune-regenerative process after bone substitute material implantation but also establish a theoretical basis for developing bone substitute materials for promoting bone tissue regeneration. STATEMENT OF SIGNIFICANCE: Bone substitute material implantation is essential in the healing of large bone defects. Existing research suggests that T lymphocytes are instrumental in bone regeneration. However, the specific mechanisms governing T cell recruitment and specific subsets that are essential for bone regeneration remain unclear. In this study, we demonstrate that activation of calcium channels in macrophages by biphasic calcium phosphate (BCP) causes them to release the chemokines Ccl3 and Ccl17 to recruit CD4+ T cells, predominantly Tregs, which play a crucial role in ectopic osteogenesis by BCP. Our findings provide a theoretical foundation for developing bone substitute material for bone tissue regeneration.

A biphasic calcium phosphate/acylated methacrylate gelatin composite hydrogel promotes osteogenesis and bone repair

PURPOSE/AIM

Bone defects caused by trauma, tumors, congenital malformation, or inflammation are very common in orthopedics. In recent years, mimicking the composition and structure of natural bone tissue has become a hot topic in biomaterial research, with the aim of developing an ideal biomaterial for bone defect transplantation. Here, the feasibility of a biphasic calcium phosphate (BCP)/acylated methacrylate gelatin (GelMA) composite hydrogel to repair bone defects was evaluated in vitro and in rats.

MATERIALS AND METHODS

The biocompatibility of a biphasic calcium phosphate (BCP)/acylated methacrylate gelatin (GelMA) composite hydrogel was evaluated by cytoskeleton staining, live/dead cell staining and cell proliferation assays. The in vitro osteogenic activities of the composite hydrogel were evaluated by alkaline phosphatase and alizarin red staining, as well as osteogenic gene expression analysis at both transcript and protein levels. The in vivo bone repair activities were evaluated using the rat skull defect model.

RESULTS

The BCP/GelMA composite hydrogel displayed excellent biocompatibility and promoted osteogenesis of bone marrow mesenchymal stem cells in vitro. In addition, the BCP/GelMA composite hydrogel markedly promoted new bone formation in the rat skull-defect model.

CONCLUSIONS

BCP/GelMA composite hydrogel may be an effective artificial material for bone tissue engineering.

Combined Application of Dentin Noncollagenous Proteins and Odontogenic Biphasic Calcium Phosphate in Rabbit Maxillary Sinus Lifting

BACKGROUND

Teeth can be used as a raw material for preparing bone substitutes due to their similar chemical composition to bone. The objective of our study was to evaluate the effect of odontogenic biphasic calcium phosphate (BCP) incorporating dentin noncollagenous proteins (DNCPs) on osteogenesis and stability in maxillary sinus augmentation.

METHODS

The composition, structure and morphology of the odontogenic BCP were tested by X-ray powder diffraction (XRD), Brunauer-Emmett-Teller, and scanning electron microscopy methods. The biocompatibility and osteoinduction of DNCPs and materials were examined in vitro and their bone regeneration capacity was verified in vivo.

RESULTS

The results showed that the cells adhered and proliferated well on the DNCP-loaded BCP scaffold. The odontogenic BCP and DNCPs promoted osteogenic differentiation of cells, The new bone formation in the BCP groups and DNCP subgroups was significantly higher than the new bone formation in the control, and the new bone quality was better. The bone regeneration effect of odontogenic BCP was similar to the effect of deproteinized bovine bone mineral, but β-TCP did not maintain the height and volume of bone reconstruction.

CONCLUSION

In conclusion, the combined application of DNCPs and odontogenic BCP is an effective strategy for tissue engineering osteogenesis in the maxillary sinus region. The biomimetic strategy could provide a new approach for patients requiring maxillary sinus lifting.

Use of biphasic calcium phosphate versus demineralized bone matrix: retrospective clinical and CT analysis of posterolateral fusion results

PURPOSE

Bone graft extenders have been developed to prevent donor site morbidity associated with iliac crest bone graft, but few studies compared the efficacy of various substitutes. Our purpose was to determine fusion rate and clinical outcome in patients undergoing lumbar arthrodesis using demineralized bone matrix (DBM) and biphasic calcium phosphate (BCP).

METHODS

Patients with degenerative spondylolisthesis undergoing one-level or two-level arthrodesis of lumbar spine were retrospectively reviewed. Two treatment groups placed either BCP or DBM, in addition to local autograft in lumbar posterolateral space. Three-dimensional CT exam and dynamic flexion-extension radiographs at postoperative 2-year were assessed for posterolateral fusion status and pain scale and Oswestry Disability Index (ODI) for clinical outcome.

RESULTS

Of the 148 patients reviewed (including 23 in one- and 58 patients in two-level in BCP group, and 47 in one- and 20 patients in two-level in DBM group), no significant differences were found in terms of age, sex, BMI, smoking, diabetes, steroids, number of level fused, non-union rate or revision surgery between BCP and DBM groups. Significantly improved pain scale of back and leg and ODI were found in both groups postoperatively without group difference. We found a comparable fusion rate in one-level surgery (100% versus 93.6%) and a superior fusion rate of BCP group in two-level surgery (98.3% versus 80.0%, p = 0.01).

CONCLUSION

Being a bone graft extender without osteoinductive property, with local autograft, BCP is comparable to DBM for one- and superior for two-level fusion. No significant difference was found in clinical outcomes.

Dynamics of the natural genesis of β-TCP/HAp phases in postnatal fishbones towards gold standard biocomposites for bone regeneration

The search for gold-standard materials for bone regeneration is still a challenge in reconstruction surgery. The ratio between hydroxyapatite (HAp) and β-tricalcium phosphate (β-TCP) in biphasic calcium phosphate ceramics (BCPs) is one of the most important factors in osteoinduction promotion and controlled biodegradability, configurating what is currently considered as a possible gold standard material for bone substitution in reconstructive surgery. Exploring the natural genesis of the HAp and β-TCP phases in fishbones during their postnatal growth, this study developed a biphasic bioceramic obtained from the calcination of Nile tilapia (Oreochromis niloticus) bones as a function of their ages. The natural genesis dynamics of the structural evolution of the β-TCP and HAp phases were characterized by physicochemical methods, taking into account of the age of the fish and the material processing conditions. Thermal analysis (TGA / DTA) showed complete removal of the organic matter and transitions associated with the transformation of carbonated hydroxyapatite (CDHA) to HAp and β-TCP phases. After calcination at 900 °C, the material was characterized by: X-ray diffraction (XRD) and refinement by the Rietveld method; Fourier Transform Infrared Spectroscopy with Attenuated Total Reflection (FTIR-ATR); Raman spectroscopy; Scanning Electron Microscopy (SEM) and Flame Atomic Absorption Spectroscopy (FAAS). The analysis allowed identification and quantitative estimate of the variations of the HAp and β-TCP phases in the formation of the BCPs. The results showed that the decrease in β-TCP against the increase in the HAp phases is symmetrical to the dynamics of the natural genesis of these phases, surprisingly maintaining the balanced phase proportion even when bones of young fishes were used. The microstructure analysis confirms the observed transformation. In addition, in vivo tests demonstrated the osteoinductive potential of BCP scaffolds implanted in an ectopic site, and their remarkable regenerative functionality, as bone graft, was demonstrated in alveolar bone after tooth extraction. MTT cytotoxicity assay for BCP samples for MC3T3-E1 pre-osteoblasts and L929 fibroblasts cells showed viability equal or higher than 100%. A logistic empirical model is presented to explain the three stages of HAp natural formation with fish age and it is also compared to the fish size evolution.

Effect of silicon or cerium doping on the anti-inflammatory activity of biphasic calcium phosphate scaffolds for bone regeneration

Biphasic calcium phosphate (BCP) bioceramics composed of hydroxyapatite and β-tricalcium phosphate have attracted considerable attention as ideal bone substitutes for reconstructive surgery, orthopedics, and dentistry, owing to their similar chemical composition to bone mineral and biocompatibility. The addition of trace elements to BCP bioceramics, such as magnesium (Mg), cerium (Ce), and silicon (Si), can alter the physicochemical and biological properties of the resulting materials. To improve the anti-inflammatory activity of a pure BCP scaffold, this study developed a simple wet chemical precipitation and gel-casting method to fabricate microporous BCP scaffolds containing Si or Ce. The BCP scaffolds exhibited interconnected microporous structures with uniform micropores and unequiaxed grains. No changes in the phase composition and microstructure of the scaffolds with the Si or Ce doping were observed. Conversely, Si or Ce doping into the BCP crystal lattice influenced the in vitro biological activity of the scaffolds and the bone-forming ability of the cells cultured on the BCP scaffolds. The results of biological activity assays demonstrated that Ce-BCP promoted cell proliferation and osteogenic differentiation more effectively than the other scaffolds. In particular, Ce-BCP significantly suppressed the expression of bone-active cytokines via the anti-inflammatory and anti-oxidative effects. Therefore, Si- or Ce-doped BCP scaffolds can contribute to providing a new generation of bone graft substitutes.

Systemic and local innate immune responses to surgical co-transplantation of mesenchymal stromal cells and biphasic calcium phosphate for bone regeneration

Bone regeneration from mesenchymal stromal cells (MSC) is attributed to comprehensive immune modulation mediated by the MSC. However, the temporal and spatial regulation of these immune responses has not yet been described. The aim of the present study was to assess the local and systemic innate immune responses to implantation of biphasic calcium phosphate biomaterial (BCP) alone, or with bone marrow derived MSC (BCP+MSC), in critical-sized calvarial bone defects of Lewis rats. Four weeks after implantation, flow cytometry analysis of innate immune cells revealed increased numbers of circulating classical monocyte-macrophages (MM) and decreased non-classical MM in the BCP+MSC group. At week 8, this differential systemic MM response was associated with an increased presence of local tissue anti-inflammatory macrophages expressing CD68 and CD163 markers (M2-like). In the BCP group without MSC, NK cells increased at weeks 1 and 4, and neutrophils increased in circulation at weeks 2 and 8. At week 8, the increase in number of neutrophils in circulation was associated with decreased local tissue neutrophils, in the BCP+MSC group. Gene expression analysis of tissue biopsies from defects implanted with BCP+MSC, in comparison to BCP alone, revealed upregulated expression of early osteogenesis genes along with macrophage differentiation-related genes at weeks 1 and 8 and neutrophil chemotaxis-related genes at week 1. This study is the first to demonstrate that surgical implantation of BCP or BCP+MSC grafts differentially regulate both systemic and local tissue innate immune responses which enhance bone formation. The results provide new insights into immune mechanisms underlying MSC-mediated bone regeneration. STATEMENT OF SIGNIFICANCE: The suitability of biphasic calcium phosphate and mesenchymal stromal cell construct (BCP+MSC) transplantation is evident from their progress in clinical trials for treating challenging maxillofacial bone defects. But less is known about the overall immune response generated by this surgical process and how it later impacts the bone formation. To this end, it is crucial to understand for both clinicians and researchers, the systemic immune response to transplanting MSC in patients for ensuring both the safety and efficacy of cell therapies. In this study, we used rat calvarial bone defect model and showed that both systemic and local innate immunes responses (monocyte-macrophages and neutrophils) are favorably directed towards enhanced bone formation in BCP+MSC implanted defects, as compared to BCP alone.

Fabrication and characterization of a semi-rigid shell barrier system made of polycaprolactone and biphasic calcium phosphate: A novel barrier system for bone regeneration

INTRODUCTION

Nowadays, no barrier membrane serves all purposes of bone augmentation. This study aimed to fabricate a semi-rigid shell barrier system composed of a semi-rigid shell and a covering membrane or a semi-resorbable barrier membrane, based on polycaprolactone (PCL) and biphasic calcium phosphate (BCP) for guided bone regeneration (GBR).

MATERIALS AND METHODS

A shell and a covering membrane were fabricated by a solvent casting technique based on PCL (70) and BCP (30). The experimental groups were a semi-rigid shell, an airdried membrane, a buffered membrane, and a commercial d-PTFE as a control. Physico-chemical, mechanical properties, and in vitro biocompatibility with osteoblasts and fibroblasts cells were evaluated in all groups.

RESULTS

The fabricated materials had rough surfaces with a homogeneous distribution of BCP particles on one side and a smooth surface on the opposite side. The airdried membrane presented a rougher surface on both top and bottom sides (Sq = 605.45 nm, 556.82 nm) than the semi-rigid shell (310.74 nm, 424.56 nm) and the buffered membrane (277.9 nm, 306.98 nm), respectively. The pore sizes of the airdried membrane (25-40 μm) were larger than the semi-rigid shell (5-40 μm) and the buffered membrane (5-25 μm). The porosities of the airdried and buffered membranes (∼40%) were higher than the semi-rigid shell (∼20%) significantly (p < 0.05). All fabricated materials were hydrophilic, with the lowest water contact angle in the semi-rigid shell (54.7° ± 3.06°), then the airdried (61.15° ± 4.76°), and the buffered (75.74° ± 2.8°) respectively. The semi-rigid shell resisted a higher load on compressive force (18.82 ± 2.72 N) than the d-PTFE membrane (4.23 ± 0.5 N). The tensile stress of the buffered membrane (2.544 ± 0.19 MPa) was not different from the d-PTFE (2.908 ± 0.12 MPa) but was higher than the airdried membrane (1.302 ± 0.13 MPa) significantly (P < 0.05). The airdried membrane had reached 100% swelling ability within 1 h, which was significantly faster than the buffered membrane (12 h) and the semi-rigid shell (7 days), and they were slowly degraded by lysozyme at 6 months (airdried: 24.88% ± 0.96%, buffered: 13.67% ± 0.55%, and semi-rigid: 8.62% ± 0.88%). All fabricated membranes showed no toxicity to osteoblast and fibroblast cells.

CONCLUSION

The semi-rigid shell and the covering membranes demonstrated suitable physical and mechanical properties, and biocompatibility, and can be assembled as the novel semi-rigid shell barrier system for bone regeneration.

[Influence of different sintering temperatures on mesoporous structure and ectopic osteogenesis of biphasic calcium phosphate ceramic granule materials]

Objective

To detect the difference in the osteogenesis ability of biphasic calcium phosphate (BCP) ceramic granular materials with different mesoporous diameters prepared at different sintering temperatures through in vivo and in vitro experiments, so as to provide evidence for screening BCP materials with better clinical application parameters.

Methods

Three kinds of BCP (materials 1, 2, 3) were prepared by mixing hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) at a ratio of 8∶2 and sintered at 1 050, 1 150, and 1 250℃ for 3 hours, respectively. The internal porosity and the diameter, volume, and area of the mesopore were measured by Brunauer-Emmett-Teller test (BET); the composition of the material was evaluated by X-ray diffraction (XRD); the microscopic surface morphology of the material was observed by scanning electron microscopy (SEM). The 3rd generation bone marrow mesenchymal stem cells (BMSCs) from Sprague-Dawley rats were co-cultured with the materials 1, 2, and 3 for 7 days in vitro respectively (groups A, B, and C), and the cells adhesion on the materials was observed by SEM and phalloidine staining, respectively. Cell proliferation activity was measured by cell counting kit 8 method. In vivo, 9 muscle bags were made in dorsal muscles of 9 beagles, respectively. The muscle bags were randomly divided into 3 groups (3 per beagle in each group) and materials 1, 2, and 3 were placed into the muscle bags of groups A, B, and C, respectively. After 1, 2, and 3 months of operation, 3 beagles were anesthetized and the samples were stained with HE, Masson, and Safranin, and the bone formation area ratio in the BCP gap was calculated. Real-time fluorescence quantitative PCR (qRT-PCR) was performed to detect the expressions of bone-related genes [including alkaline phosphatase (ALP), osteopontin (OPN), and osteocalcin (OC)].

Results

The BET test showed that with the increase of sintering temperature, the internal porosity of the particles did not change significantly, but the diameter, volume, and area of the mesopores gradually decreased. The XRD detection showed that the XRD waves of HA and β-TCP could be seen in all 3 kinds of materials; SEM showed that there were widely distributed macropores on the surface of 3 kinds of BCPs, and the interpores connected with the others. In vitro, BMSCs adhered and proliferated on the surfaces of 3 kinds of BCPs, and the cell biocompatibility of the materials in groups B and C was better than that in group A. In vivo, obvious osteoid tissue deposition could be observed in the intergranular space of 3 kinds of BCPs from 2 months after implantation. The bone formation area ratio of each group increased with time. The bone formation area ratio in group A was significantly higher than that in groups B and C at 2 and 3 months after implantation, and in group A than in group B at 1 month ( P<0.05). qRT-PCR showed that the expressions of osteogenic related genes peaked at 2 months in group A, and gradually increased with time in groups B and C. The relative expressions of ALP and OPN mRNAs in group A were significantly higher than those in groups B and C at 1 month after implantation, the relative expression of OC mRNA in group A was significantly higher than that in groups B and C at 2 months after operation, the relative expression of ALP mRNA in groups B and C and the relative expression of OPN mRNA in group B were significantly higher than those in group A, all showing significant differences ( P<0.05); there was no significant difference in the relative expression of each gene among the other groups at each time point ( P>0.05).

Conclusion

The mesoporous diameter of BCP decreases with the increase of sintering temperature. Different mesoporous diameters lead to different ectopic osteogenesis of BCP materials. BCP material with mesoporous diameter of 12.57 nm has better osteogenic ability which can activate the osteogenic gene earlier. The mesoporous diameter is expected to be an adjustable index for optimizing the osteogenic capacity of BCP materials.

Influence of different carrier materials on biphasic calcium phosphate induced bone regeneration

OBJECTIVES

Biphasic calcium phosphate (BCP) is a bioceramic material successfully used in alloplastic bone augmentation. Despite many advantages, a disadvantage of BCP seems to be a difficult application and position instability. The aim of this study was to determine how different carrier materials influence BCP-induced quantitative and qualitative bone regeneration.

MATERIALS AND METHODS

A total of 70 critical size defects were set in the frontal bone of 14 domestic pigs (5 each) and filled randomly with either BCP alone (BCP), BCP in combination with nano-hydroxyapatite (BCP + NHA), BCP embedded in native porcine type I/III collagen blocks (BCP + C), autologous bone (AB), or were left empty (ED). Specimens were harvested after 4 and 8 weeks and were evaluated histologically as well as histomorphometrically.

RESULTS

Significantly lowest rate of new bone formation was found in ED (p = < 0.001) and BCP + NHA groups (p = 0.05). After 8 weeks, the highest percentage of new bone formation was observed in the BCP + C group. Fibrous matrix was detected highest in BCP alone. The lowest residual bone substitute material was found in BCP + C after 8 weeks.

CONCLUSIONS

BCP-induced bone regeneration is indeed affected by different carrier types. Surface morphology and bioactive characteristics influence osseointegration and new bone formation in vivo. The combination of type I/III collagen seems most suitable for qualitative and quantitative bone regeneration.

CLINICAL RELEVANCE

Stabilization of granular bone substitutes using type I/III collagen might be an alternative to granulates alone, indicating excellent volume stability, satisfactory plasticity, and easy application.

Influence of biodegradable polymer membrane on new bone formation and biodegradation of biphasic bone substitutes: an animal mandibular defect model study

Purpose

The purpose of this study was to evaluate the influence of biodegradable polycaprolactone membrane on new bone formation and the biodegradation of biphasic alloplastic bone substitutes using animal models.

Materials and methods

In this study, bony defect was formed at the canine mandible of 8 mm in diameter, and the defects were filled with Osteon II. The experimental groups were covered with Osteoguide as barrier membrane, and the control groups were closed without membrane coverage. The proportion of new bone and residual bone graft material was measured histologically and histomorphometrically at postoperative 4 and 8 weeks.

Results

At 4 weeks, the new bone proportion was similar between the groups. The proportion of remaining graft volume was 27.58 ± 6.26 and 20.01 ± 4.68% on control and experimental groups, respectively (P < 0.05). There was no significant difference between the two groups in new bone formation and the amount of residual bone graft material at 8 weeks.

Conclusion

The biopolymer membrane contributes to early biodegradation of biphasic bone substitutes in the jaw defect but it does not affect the bone formation capacity of the bone graft.

Sialic acid-modified chitosan oligosaccharide-based biphasic calcium phosphate promote synergetic bone formation in rheumatoid arthritis therapy

Therapeutic goals for rheumatoid arthritis (RA) consist of inhibiting the inflammatory response and repairing the damaged bone/cartilage. Tissue engineering could achieve both goals, however, it was hindered due to the lack of biologically relevant tissue complexity, limitation in covering the entire polyarthritis lesions and requirement of extra surgical implantation. Integrating nanotechnologies into clinically sized implants represents a major opportunity to overcome these problems. Herein, we designed a sialic acid (SA)-modified chitosan oligosaccharide-based biphasic calcium phosphate (BCP), a biomimetic nanoplatform that could load with methotrexate. We found that SA modification could not only improve the accumulation of the designed organic-inorganic nanoplatform in arthritic paws (34.38% higher than those without SA modification at 48 h), but also cooperate with BCP to exert synergetic mineralization of calcium phosphate, allowing more osteoblasts to attach, proliferate and differentiate. The more differentiated osteoblasts produced 4.46-fold type I collagen and 2.60-fold osteoprotegerin compared to the control group. Besides, the disassembled nanorods released chitosan oligosaccharide-based micelles, revealing a cartilage-protective effect by reducing the loss of glycosaminoglycan. All these improvements contributed to the light inflammatory response and reduced destruction on cartilage/bone. The findings provide a novel strategy for RA therapy via nanometer-scale dimension mimicking the natural tissues.

Effect of TiO2 addition on adhesion and biological behavior of BCP-TiO2 composite films deposited by magnetron sputtering

The present investigation focuses on the deposition of biphasic calcium phosphate (BCP) and titania (TiO₂) composite films on Ti-6Al-4V substrates using radio frequency (RF) magnetron sputtering. Three different compositions such as 100% BCP, 25% TiO₂-75% BCP and 50% TiO₂-50% BCP films were fabricated, and the physical, mechanical and biological behaviors of the films were analyzed. Post deposition, the films were annealed at 700 °C for 2 h to induce the crystallinity and to study its effect on different properties. The wettability was found to be 95°(±3°) for 100% BCP, 73°(±2°) for 25% TiO₂-75% BCP and 35°(±1°) for 50% TiO₂-50% BCP films, indicating improvement in wettability with an increase of TiO₂ weight percent in the composite films. The value of critical load (L_c2) for 100 BCP film improved from 8.7 N to 14.8 N (25 TiO₂-BCP) and >19 N (50 TiO₂-BCP film), indicating improvement in bonding strength with TiO₂ addition. The fetal bovine serum (FBS) adsorption decreased from 7.11 ± 0.25 to 4.42 ± 0.17 μg/cm² with TiO₂ weight percent from 0 to 50%. Cell adhesion and proliferation significantly improved in 100% BCP, 25% TiO₂-75% BCP and 50% TiO₂-50% BCP films as compared to uncoated Ti-6Al-4V. The maximum cell proliferation was found on the surface of 50% TiO₂-50% BCP film (210.1 ± 6.5%) after 6 days of incubation. However, after annealing all the films exhibited less cell adhesion and cytocompatibility presumably due to change in composition. Globular apatite structure was observed on all modified surfaces after 7 days immersion in simulated body fluid (SBF); however, the growth rate was higher for 50 TiO₂-BCP films. All these results revealed that the addition of TiO₂ in BCP film (without annealing) is advantageous for improving the bonding strength as well as the bioactivity of implants, which can be used for long-term dental and orthopedic applications.

Fibrin biopolymer as scaffold candidate to treat bone defects in rats

Background

Bone tissue repair remains a challenge in tissue engineering. Currently, new materials are being applied and often integrated with live cells and biological scaffolds. The fibrin biopolymer (FBP) proposed in this study has hemostatic, sealant, adhesive, scaffolding and drug-delivery properties. The regenerative potential of an association of FBP, biphasic calcium phosphate (BCP) and mesenchymal stem cells (MSCs) was evaluated in defects of rat femurs.

Methods

Adult male Wistar rats were submitted to a 5-mm defect in the femur. This was filled with the following materials and/or associations: BPC; FBP and BCP; FBP and MSCs; and BCP, FBP and MSCs. Bone defect without filling was defined as the control group. Thirty and sixty days after the procedure, animals were euthanatized and subjected to computed tomography, scanning electron microscopy and qualitative and quantitative histological analysis.

Results

It was shown that FBP is a suitable scaffold for bone defects due to the formation of a stable clot that facilitates the handling and optimizes the surgical procedures, allowing also cell adhesion and proliferation. The association between the materials was biocompatible. Progressive deposition of bone matrix was higher in the group treated with FBP and MSCs. Differentiation of mesenchymal stem cells into osteogenic lineage was not necessary to stimulate bone formation.

Conclusions

FBP proved to be an excellent scaffold candidate for bone repair therapies due to application ease and biocompatibility with synthetic calcium-based materials. The satisfactory results obtained by the association of FBP with MSCs may provide a more effective and less costly new approach for bone tissue engineering.

Development of chitosan/gelatin hydrogels incorporation of biphasic calcium phosphate nanoparticles for bone tissue engineering

The chitosan/gelatin hydrogel incorporated with biphasic calcium phosphate nanoparticles (BCP-NPs) as scaffold (CGB) for bone tissue engineering was reported in this article. Such nanocomposite hydrogels were fabricated by using cycled freeze-thawing method, of which physicochemical and biological properties were regulated by adjusting the weight ratio of chitosan/gelatin/BCP-NPs. The needle-like BCP-NPs were dispersed into composites uniformly, and physically cross-linked with chitosan and gelatin, which were identified via Scanning Electron Microscope (SEM) images and Fourier Transform Infrared Spectroscopy (FT-IR) analysis. The porosity, equilibrium swelling ratio, and compressive strength of CGB scaffolds were mainly influenced by the BCP-NPs concentration. In vitro degradation analysis in simulated body fluids (SBF) displayed that CGB scaffolds were degraded up to at least 30 wt% in one month. Also, CCK-8 analysis confirmed that the prepared scaffolds had a good cytocompatibility through in culturing with bone marrow mesenchymal stem cells (BMSCs). Finally, In vivo animal experiments revealed that new bone tissue was observed inside the scaffolds, and gradually increased with increasing months, when implanted CGB scaffolds into large necrotic lesions of rabbit femoral head. The above results suggested that prepared CGB nanocomposites had the potential to be applied in bone tissue engineering.

Eight-week healing of grafted calvarial bone defects with hyperbaric oxygen therapy in rats

Purpose

The purpose of this study was to evaluate the synergistic effect of adjunctive hyperbaric oxygen (HBO) therapy on new bone formation and angiogenesis after 8 weeks of healing.

Methods

Sprague-Dawley rats (n=28) were split into 2 groups according to the application of adjunctive HBO therapy: a group that received HBO therapy (HBO group [n=14]) and another group that did not receive HBO therapy (NHBO group [n=14]). Each group was divided into 2 subgroups according to the type of bone graft material: a biphasic calcium phosphate (BCP) subgroup and an Escherichia coli-derived recombinant human bone morphogenetic protein-2-/epigallocatechin-3-gallate-coated BCP (mBCP) subgroup. Two identical circular defects with a 6-mm diameter were made in the right and left parietal bones of each rat. One defect was grafted with bone graft material (BCP or mBCP). The other defect was not grafted. The HBO group received 2 weeks of adjunctive HBO therapy (1 hour, 5 times a week). The rats were euthanized 8 weeks after surgery. The specimens were prepared for histologic analysis.

Results

New bone (%) was higher in the NHBO-mBCP group than in the NHBO-BCP and control groups (P<0.05). Blood vessel count (%) and vascular endothelial growth factor staining (%) were higher in the HBO-mBCP group than in the NHBO-mBCP group (P<0.05).

Conclusions

HBO therapy did not have a positive influence on bone formation irrespective of the type of bone graft material applied after 8 weeks of healing. HBO therapy had a positive effect on angiogenic activity.

Thermal cycling effect on osteogenic differentiation of MC3T3-E1 cells loaded on 3D-porous Biphasic Calcium Phosphate (BCP) scaffolds for early osteogenesis

The application of heat stress on a defect site during the healing process is a promising technique for early bone regeneration. The primary goal of this study was to investigate the effect of periodic heat shock on bone formation. MC3T3-E1 cells were seeded onto biphasic calcium phosphate (BCP) scaffolds, followed by periodic heating to evaluate osteogenic differentiation. Heat was applied to cells seeded onto scaffolds at 41 °C for 1 h once, twice, and four times a day for seven days and their viability, morphology, and differentiation were analyzed. BCP scaffolds with interconnected porous structures mimic bone biology for cellular studies. MTT and confocal studies have shown that heat shock significantly increased cell proliferation without any toxic effects. Compared to non-heated samples, heat shock enhanced calcium deposition and mineralization, which could be visualized by SEM observation and Alizarin red S staining. Immunostaining images showed the localization of osteogenic proteins ALP and OPN on heat-shocked cells. qRT-PCR analysis revealed the presence of more osteospecific markers, osteopontin (OPN), osteocalcin, collagen type X, and Runx2, in the heat-shocked samples than in the non-heated sample. Periodic heat shock significantly upregulated both heat shock proteins (HSP70 and HSP27) in differentiated MC3T3-E1 cells. The results of this study demonstrated that periodically heat applied especially two times a day was better approach for osteogenic differentiation. Hence, this work provides a define temperature and time schedule for the development of a clinical heating device in future for early bone regeneration during the postsurgical period.

Improvement of the osteogenic potential of ErhBMP-2-/EGCG-coated biphasic calcium phosphate bone substitute: in vitro and in vivo activity

Purpose

The aim of this study was to evaluate the enhancement of osteogenic potential of biphasic calcium phosphate (BCP) bone substitute coated with Escherichia coli-derived recombinant human bone morphogenetic protein-2 (ErhBMP-2) and epigallocatechin-3-gallate (EGCG).

Methods

The cell viability, differentiation, and mineralization of osteoblasts was tested with ErhBMP-2-/EGCG solution. Coated BCP surfaces were also investigated. Standardized, 6-mm diameter defects were created bilaterally on the maxillary sinus of 10 male New Zealand white rabbits. After removal of the bony windows and elevation of sinus membranes, ErhBMP-2-/EGCG-coated BCP was applied on one defect in the test group. BCP was applied on the other defect to form the control group. The animals were sacrificed at 4 or 8 weeks after surgery. Histologic and histometric analyses of the augmented graft and surrounding tissue were performed.

Results

The 4-week and 8-week test groups showed more new bone (%) than the corresponding control groups (P<0.05). The 8-week test group showed more new bone (%) than the 4-week test group (P<0.05).

Conclusions

ErhBMP-2-/EGCG-coated BCP was effective as a bone graft material, showing enhanced osteogenic potential and minimal side effects in a rabbit sinus augmentation model.

Adjunctive hyperbaric oxygen therapy for irradiated rat calvarial defects

Purpose

The aim of this study was to conduct a histologic evaluation of irradiated calvarial defects in rats 4 weeks after applying fibroblast growth factor-2 (FGF-2) with hyaluronan or biphasic calcium phosphate (BCP) block in the presence or absence of adjunctive hyperbaric oxygen (HBO) therapy.

Methods

Twenty rats were divided into HBO and non-HBO (NHBO) groups, each of which was divided into FGF-2 and BCP-block subgroups according to the grafted material. Localized radiation with a single 12-Gy dose was applied to the calvaria of rats to simulate radiotherapy. Four weeks after applying this radiation, 2 symmetrical circular defects with a diameter of 6 mm were created in the parietal bones of each animal. The right-side defect was filled with the materials mentioned above and the left-side defect was not filled (as a control). All defects were covered with a resorbable barrier membrane. During 4 weeks of healing, 1 hour of HBO therapy was applied to the rats in the HBO groups 5 times a week. The rats were then killed, and the calvarial specimens were harvested for radiographic and histologic analyses.

Results

New bone formation was greatest in the FGF-2 subgroup, and improvement was not found in the BCP subgroup. HBO seemed to have a minimal effect on new bone formation. There was tendency for more angiogenesis in the HBO groups than the NHBO groups, but the group with HBO and FGF-2 did not show significantly better outcomes than the HBO-only group or the NHBO group with FGF-2.

Conclusions

HBO exerted beneficial effects on angiogenesis in calvarial defects of irradiated rats over a 4-week healing period, but it appeared to have minimal effects on bone regeneration. FGF-2 seemed to enhance new bone formation and angiogenesis, but its efficacy appeared to be reduced when HBO was applied.

Epithelial cell functionality on electroconductive Fe/Sr co-doped biphasic calcium phosphate

In the perspective of dental restorative applications, co-doped bioceramics have not been explored much. From the clinical perspective, a successful dental implant is expected to interact with peri-prosthetic bones, gingival tissue, and surrounding connective tissues. The interaction of implant and implant coating materials with bone tissue is well studied. However, their interaction with surrounding epithelial components needs scientific validation. In this context, the present study aims at quantitative evaluation of the electrical properties of Fe/Sr co-doped biphasic calcium phosphate (BCP) samples and assessment of their cytocompatibility with epithelial (vero) cells. Sr/Fe co-doped BCPs were prepared by sol-gel synthesis technique, with different dopant concentration. Impact of co-doping on conductivity was assessed and interestingly an increase in conductivity with dopant amount was recorded in different co-doped BCPs. Cellular study showed the significant ( p = 0.01) increase in both cellular viability and functionality with increasing conductivity of samples. Higher epithelial cell adhesion indicates that (Sr/Fe) co-doped BCP would be favorable for faster epithelial sealing and also would reduce the chances of infection. Real-time PCR and immunofluorescence studies indicated that the expression of the epithelial marker (E-cadherin) significantly ( p = 0.01) increased in 10, 30 and 40 mol% co-doped samples in comparison to undoped BCP. In contrast to E-cadherin, fold change of β-catenin remains unchanged amongst the co-doped ceramics, implying the absence of tumorigenic potential of (Sr/Fe) co-doped BCP. In addition, immune-fluorescence signatures for cellular polarity are established from enhanced expression PARD3 protein, which has major relevance for cellular morphogenesis and cell division. Summarizing, the present study establishes the efficacy of Sr/Fe co-doped BCPs as a dental implant coating material and its ability to modulate vero cell functionality.

Cell therapy induced regeneration of severely atrophied mandibular bone in a clinical trial

Background

Autologous grafting, despite some disadvantages, is still considered the gold standard for reconstruction of maxillofacial bone defects. The aim of this study was to evaluate bone regeneration using bone marrow-derived mesenchymal stromal cells (MSCs) in a clinical trial, a less invasive approach than autologous bone grafting. This comprehensive clinical trial included subjects with severe mandibular ridge resorption.

Methods

The study included 11 subjects aged 52–79 years with severe mandibular ridge resorption. Bone marrow cells were aspirated from the posterior iliac crest and plastic adherent cells were expanded in culture medium containing human platelet lysate. The MSCs and biphasic calcium phosphate granules as scaffolds were inserted subperiosteally onto the resorbed alveolar ridge. After 4–6 months of healing, new bone formation was assessed clinically and radiographically, as were safety and feasibility. Bone at the implant site was biopsied for micro-computed topography and histological analyses and dental implants were placed in the newly regenerated bone. Functional outcomes and patient satisfaction were assessed after 12 months.

Results

The bone marrow cells, expanded in vitro and inserted into the defect together with biphasic calcium phosphate granules, induced significant new bone formation. The regenerated bone volume was adequate for dental implant installation. Healing was uneventful, without adverse events. The patients were satisfied with the esthetic and functional outcomes. No side effects were observed.

Conclusions

The results of this comprehensive clinical trial in human subjects confirm that MSCs can successfully induce significant formation of new bone, with no untoward sequelae. Hence, this novel augmentation procedure warrants further investigation and may form the basis of a valid treatment protocol, challenging the current gold standard.

Trial registration

EudraCT, 2012-003139-50. Registered on 21 August 2013. ClinicalTrials.gov, NCT 02751125. Registered on 26 April 2016.

Mechano-tribological properties and in vitro bioactivity of biphasic calcium phosphate coating on Ti-6Al-4V

Biphasic calcium phosphate (BCP) consists of hydroxyapatite (HA) and beta-tricalcium phosphate (β-TCP). BCP is mainly used in artificial tooth and bone implants due to higher protein adsorption and osteoinductivity compared to HA alone. Although, many studies have been investigated on radio frequency (RF) magnetron sputtering of HA on Ti and its alloy, however, limited studies are available on BCP coating by this process and its bioactivity and adhesion behavior. Thus, in order to obtain a better understanding and applications of BCP films, RF magnetron sputtering is used to deposit BCP films on Ti-6Al-4V in the present study. The effect of film thickness on wettability, mechanical properties and in vitro bioactivity at a particular set of sputtering parameters are investigated. BCP film thickness of 400 nm, 700 nm and 1000 nm are obtained when sputtered for 4 h, 6 h and 8 h, respectively. Although the phase compositions are almost same for all films, the surface roughness values varies around 112-153 nm with rise in film thickness. This in turn enhances hydrophilicity in accordance to Wenzel relation as the contact angle decreases from 89.6 ± 2° to 61.2 ± 2°. It is found that the 1000 nm film possess highest micro-hardness and surface scratch resistance. No cracking of film up to scratch load of 2.3 N and no significant delamination up to load of 7.8 N are observed, indicating very good adhesion between BCP films and Ti-6Al-4V substrate. There is a great improvement in wt% apatite layer formation on all films when dipped in simulated body fluid (SBF) for 14 days. Among these, 1000 nm sputtered film results the highest increase in wt% apatite layer from 44.87% to 86.7%. The apatite layer possess small globular as well as elliptical structure are nucleated and grew on all the BCP films. Thus, sputtering of BCP films improves wettability, mechanical properties as well as bioactivity of Ti-6Al-4V, which can be applied for orthopedic implants.

Comparison of the osteogenesis and fusion rates between activin A/BMP-2 chimera (AB204) and rhBMP-2 in a beagle's posterolateral lumbar spine model

BACKGROUND CONTEXT

Activin A/BMP-2 chimera (AB204) could promote bone healing more effectively than recombinant bone morphogenetic protein 2 (rhBMP-2) with much lower dose in a rodent model, but there is no report about the effectiveness of AB204 in a large animal model.

PURPOSE

The purpose of this study was to compare the osteogenesis and fusion rate between AB204 and rhBMP-2 using biphasic calcium phosphate (BCP) as a carrier in a beagle's posterolateral lumbar fusion model.

STUDY DESIGN

This is a randomized control animal study.

METHODS

Seventeen male beagle dogs were included. Bilateral posterolateral fusion was performed at the L1-L2 and L4-L5 levels. Biphasic calcium phosphate (2 cc), rhBMP-2 (50 µg)+BCP (2 cc), or AB204 (50 µg)+BCP (2 cc) were implanted into the intertransverse space randomly. X-ray was performed at 4 and 8 weeks. After 8 weeks, the animals were sacrificed, and new bone formation and fusion rate were evaluated by manual palpation, computed tomography (CT), and undecalcified histology.

RESULTS

The AB204 group showed significantly higher fusion rate (90%) than the rhBMP-2 group (15%) or the Osteon group (6.3%) by manual palpation. On x-ray and CT assessment, fusion rate and the volume of newly formed bone were also significantly higher in AB204 group than other groups. In contrast, more osteolysis was found in rhBMP-2 group (40%) than in AB204 group (10%) on CT study. In histologic results, new bone formation was sufficient between transverse processes in AB204 group, and obvious trabeculation and bone remodeling were observed. But in rhBMP-2 group, new bone formation was less than AB204 group and osteolysis was observed between the intertransverse spaces.

CONCLUSIONS

A low dose of AB204 with BCP as a carrier significantly promotes the fusion rate in a large animal model when compared with the rhBMP-2. These findings demonstrate that AB204 could be an alternative to rhBMP-2 to improve fusion rate.

The use of a biphasic calcium phosphate in a maxillary sinus floor elevation procedure: a clinical, radiological, histological, and histomorphometric evaluation with 9- and 12-month healing times

Background

This study evaluates the clinical, radiological, histological, and histomorphometric aspects of a fully synthetic biphasic calcium phosphate (BCP) (60% hydroxyapatite and 40% ß-tricalcium phosphate), used in a human maxillary sinus floor elevation (MSFE) procedure with 9- and 12-month healing time.

Methods

A unilateral MSFE procedure, using 100% BCP, was performed in two series of five patients with healing times of 9 and 12 months respectively. Clinical and radiological parameters were measured up to 5 years postoperatively. Biopsy retrieval was carried out during dental implants placement. Histology and histomorphometry were performed on 5-μm sections of undecalcified bone biopsies.

Results

The MSFE procedure with BCP showed uneventful healing in all cases. All dental implants appeared to be well osseointegrated after 3 months. Radiological evaluation showed less than 1 mm tissue height loss from MSFE to the 5-year follow-up examination. No signs of inflammation were detected on histological examination. Newly formed mineralized tissue was found cranially from the native bone. The BCP particles were surrounded by connective tissue, osteoid islands, and newly formed bone. Mineralized bone tissue was in intimate contact with the BCP particles. After 12 months, remnants of BCP were still present. The newly formed bone had a trabecular structure. Bone maturation was demonstrated by the presence of lamellar bone. Histomorphometric analysis showed at 9 and 12 months respectively an average vital bone volume/total volume of 35.2 and 28.2%, bone surface/total volume of 4.2 mm²/mm³ and 8.3 mm²/mm³, trabecular thickness of 224.7 and 66.7 μm, osteoid volume/bone volume of 8.8 and 3.4%, osteoid surface/bone surface (OS/BS) of 42.4 and 8.2%, and osteoid thickness of 93.9 and 13.6 μm.

Conclusions

MFSE with BCP resulted in new bone formation within the augmented sinus floor and allowed the osseointegration of dental implants in both groups. From a histological and histomorphometric perspective, a 9-month healing time for this type of BCP may be the optimal time for placement of dental implants.

Calcium supplementation decreases BCP-induced inflammatory processes in blood cells through the NLRP3 inflammasome down-regulation

Interaction of host blood with biomaterials is the first event occurring after implantation in a bone defect. This study aimed at investigating the cellular and molecular consequences arising at the interface between whole blood and biphasic calcium phosphate (BCP) particles. We observed that, due to calcium capture, BCP inhibited blood coagulation, and that this inhibition was reversed by calcium supplementation. Therefore, we studied the impact of calcium supplementation on BCP effects on blood cells. Comparative analysis of BCP and calcium supplemented-BCP (BCP/Ca) effects on blood cells showed that BCP as well as BCP/Ca induced monocyte proliferation, as well as a weak but significant hemolysis. Our data showed for the first time that calcium supplementation of BCP microparticles had anti-inflammatory properties compared to BCP alone that induced an inflammatory response in blood cells. Our results strongly suggest that the anti-inflammatory property of calcium supplemented-BCP results from its down-modulating effect on P2X7R gene expression and its capacity to inhibit ATP/P2X7R interactions, decreasing the NLRP3 inflammasome activation. Considering that monocytes have a vast regenerative potential, and since the excessive inflammation often observed after bone substitutes implantation limits their performance, our results might have great implications in terms of understanding the mechanisms leading to an efficient bone reconstruction.

STATEMENT OF SIGNIFICANCE

Although scaffolds and biomaterials unavoidably come into direct contact with blood during bone defect filling, whole blood-biomaterials interactions have been poorly explored. By studying in 3D the interactions between biphasic calcium phosphate (BCP) in microparticulate form and blood, we showed for the first time that calcium supplementation of BCP microparticles (BCP/Ca) has anti-inflammatory properties compared to BCP-induced inflammation in whole blood cells and provided information related to the molecular mechanisms involved. The present study also showed that BCP, as well as BCP/Ca particles stimulate monocyte proliferation. As monocytes represent a powerful target for regenerative therapies and as an excessive inflammation limits the performance of biomaterials in bone tissue engineering, our results might have great implications to improve bone reconstruction.

The Influences of Different Ratios of Biphasic Calcium Phosphate and Collagen Augmentation on Posterior Lumbar Spinal Fusion in Rat Model

PURPOSE

To determine the influence of different ratios of hydroxyapatite (HA)/beta tricalcium phosphate (β-TCP) and collagen augmentation for posterior lumbar fusion in a rat model.

MATERIALS AND METHODS

We generated a posterior lumbar fusion model in 50 rats and divided it into five groups of equal number as follows; 1) autologous bone graft as group A, 2) 70% HA+30% β-TCP as group B, 3) 70% HA+30% β-TCP+collagen as group C, 4) 30% HA+70% β-TCP as group D, and 5) 30% HA+70% β-TCP+collagen as group E. Rats were euthanized at 12 weeks after surgery and fusion was assessed by manual palpation, quantitative analysis using microCT and histology.

RESULTS

The score of manual palpation was significantly higher in group C than group E (3.1±1.1 vs. 1.8±0.8, p=0.033). However, in terms of microCT analysis, group D showed significantly higher scores than group B (5.5±0.8 vs. 3.1±1.1, p=0.021). According to quantitative volumetric analysis, 30% HA+70% β-TCP groups (group D and E) showed significantly reduced fusion mass at 12 weeks after surgery (123±14.2, 117±46.3 vs. 151±27.3, p=0.008, 0.003, respectively). Collagen augmentation groups revealed superior results in terms of both microCT score and histologic grade.

CONCLUSION

A 7:3 HA/β-TCP ratio with collagen augmentation rather than a 3:7 HA/β-TCP ratio could be a more favorable graft substitute for lumbar spinal fusion. There was positive role of collagen as an adjunct for spinal bone fusion process.

Evaluation of New Biphasic Calcium Phosphate Bone Substitute: Rabbit Femur Defect Model and Preliminary Clinical Results

Autogenous bone grafting, used to repair bone defects, is limited and the donor site can experience complications. Compared to autogenous bone graft, artificial bones have different porosity, which might make them suitable alternatives to bone grafts. Here, two porous biphasic calcium phosphate bone substitutes, namely Bicera™ and Triosite™, are used in an animal study and clinical practice to find a suitable porosity for implantation. Bicera™ and Triosite™ consist of 60 wt% hydroxyapatite and 40 wt% β-tricalcium phosphate, with the porosity of Bicera™ (82%) being higher than that of Triosite™ (70%). In the animal study, the implantation procedure was carried out on twenty-four female New Zealand rabbits. 12 weeks after implantation, the new bones were well infiltrated into the Bicera™ and Triosite™ bone grafts. In the clinical study, patients with comminuted fracture, fracture nonunion, or arthrodesis were included in the study of bone substitution with Bicera™. 27 patients underwent fracture fixation treatment. Bone healing of 22.22% (6/27) of patients happened within 3 months after the surgery, and that of 66.67% (18/27) of patients happened within 6 months. These results reveal that Bicera™ has good incorporation with host bone, and that new bone is able to grow within the porous structure, giving it high potential in the treatment of bone defects.

Biphasic calcium phosphates (BCP) of hydroxyapatite (HA) and tricalcium phosphate (TCP) as bone substitutes: Importance of physicochemical characterizations in biomaterials studies

The data presented in this article are related to the research article entitled “Biphasic calcium phosphates bioceramics (HA/TCP): Concept, physicochemical properties and the impact of standardization of study protocols in biomaterials research” [1]. This article provides in depth study of BCP bone substitutes as valuable option in the field of tissue engineering. However, there are discrepancies in the literature regarding the ideal physicochemical properties of BCP and the ideal balance between different phase compositions for enhanced bone tissue engineering (M. Ebrahimi, M.G. Botelho, S.V. Dorozhkin, 2016; M. Ebrahimi, P. Pripatnanont, S. Suttapreyasri, N. Monmaturapoj, 2014) [1,2]. This is found to be mainly because of improper characterization of BCP bioceramics in basic studies and lack of standard study protocols in in vitro and in vivo research. This data article along with original article provide the basic data required for ideal characterization of BCP and other bioceramics in an attempt to provide basic standardized protocols for future studies.

Effect of BMP2-Platelet-rich Plasma-Biphasic Calcium Phosphate Scaffold on Accelerated Osteogenesis in Mastoid Obliteration

The aim of this study was to evaluate the synergistic effect of platelet-rich plasma (PRP) and recombinant human bone morphogenic protein (BMP)-2 on accelerated osteogenesis of hydroxyapatite/β-tricalcium phosphate mixture and biphasic calcium phosphate (BCP) in mastoid obliteration. To the best of our knowledge, there have been no studies reporting the enhancing effects of BCP, combined with BMP2 and PRP, on osteogenesis in mastoid obliteration. Mastoid obliteration was performed in a control group (BCP only, n=7), a group treated with BMP2 and BCP (experimental group I, n=7), and a group treated with BMP2, PRP and BCP (experimental group II, n=7). The animals were administered fluorescent bone labels for a qualitative evaluation of bone formation; oxytetracycline hydrochloride was administered at 2 weeks, calcein at 4 weeks, and alizarin red at 8 weeks. The animals were sacrificed 12 weeks post-surgery and osteogenesis was evaluated by micro-computed tomography, histological investigation, and histomorphometry. Both experimental groups showed accelerated osteogenesis compared to the control group. However, there were no statistically significant differences between experimental groups I and II. From these results, it can be concluded that BMP2 activated BCP for the enhancement of bone regeneration. However, no synergistic effect of BMP2 and PRP on the osteogenesis of BCP was observed.

Recombinant human bone morphogenetic protein (rhBMP)9 induces osteoblast differentiation when combined with demineralized freeze-dried bone allografts (DFDBAs) or biphasic calcium phosphate (BCP)

OBJECTIVES

Recently, recombinant human bone morphogenetic protein 9 (rhBMP9) has been characterized as one of the most osteogenic growth factors among the 15 human BMPs. The aim of the present study was to investigate the effects of rhBMP9 in comparison to the clinically utilized rhBMP2 on in vitro cell behavior when combined with two bone graft materials including demineralized freeze-dried bone allografts (DFDBAs) and biphasic calcium phosphate (BCP).

MATERIALS AND METHODS

The absorption and release kinetics of rhBMPs from DFDBA and BCP were investigated by ELISA. Moreover, murine bone stromal ST2 cell behavior was investigated on DFDBA or BCP seeded on (1) graft only, (2) rhBMP2 (10 ng/ml), (3) rhBMP2 (100 ng/ml), (4) rhBMP9 (10 ng/ml), and (5) rhBMP9 (100 ng/ml). The effects of rhBMPs on DFDBA and BCP were assessed for cell adhesion, proliferation, and osteoblast differentiation by alkaline phosphatase (ALP) activity, alizarin red staining, and real-time PCR for genes encoding Runx2, ALP, and bone sialoprotein (BSP).

RESULTS

While both BMPs were gradually released from DFDBA and BCP over time, significantly higher adsorption was observed on BCP when compared to DFDBA. Cell attachment and proliferation was higher on BCP with little influence of either rhBMP2/9. Despite rhBMPs having relatively no effect on cell attachment/proliferation, a pronounced and marked effect was observed on osteoblast differentiation for both rhBMP2/9. Interestingly, it was observed that rhBMP9 induced significantly higher ALP activity, alizarin red staining, and messenger RNA (mRNA) levels of ALP and BSP when compared to rhBMP2. Our results also revealed higher differentiation for rhBMP2/9 with BCP when compared to DFDBA most likely as a result of higher growth factor adsorption.

CONCLUSION

While both rhBMP2/9 combined with DFDBA or BCP induced osteoblast differentiation, rhBMP9 induced greater osteoblast differentiation when compared to rhBMP2.

CLINICAL RELEVANCE

rhBMP9 may be a recombinant growth factor with higher potential to induce new bone formation when compared to rhBMP2. Further in vivo studies are necessary to characterize its regenerative potential in various animal models.

Four-week histologic evaluation of grafted calvarial defects with adjunctive hyperbaric oxygen therapy in rats

Purpose

The aim of this study was to characterize the healing in the grafted calvarial defects of rats after adjunctive hyperbaric oxygen therapy.

Methods

Twenty-eight male Sprague-Dawley rats (body weight, 250–300 g) were randomly divided into two treatment groups: with hyperbaric oxygen therapy (HBO; n=14) and without HBO (NHBO; n=14). Each group was further subdivided according to the bone substitute applied: biphasic calcium phosphate (BCP; n=7) and surface-modified BCP (mBCP; n=7). The mBCP comprised BCP coated with Escherichia-coli-derived recombinant human bone morphogenetic protein-2 (ErhBMP-2) and epigallocatechin-3-gallate (EGCG). Two symmetrical circular defects (6-mm diameter) were created in the right and left parietal bones of each animal. One defect was assigned as a control defect and received no bone substitute, while the other defect was filled with either BCP or mBCP. The animals were allowed to heal for 4 weeks, during which those in the HBO group underwent 5 sessions of HBO. At 4 weeks, the animals were sacrificed, and the defects were harvested for histologic and histomorphometric analysis.

Results

Well-maintained space was found in the grafted groups. Woven bone connected to and away from the defect margin was formed. More angiogenesis was found with HBO and EGCG/BMP-2 (P<0.05). None of the defects achieved complete defect closure. Increased new bone formation with HBO or EGCG/BMP-2 was evident in histologic evaluation, but it did not reach statistical significance in histometric analysis. A synergic effect between HBO and EGCG/BMP-2 was not found.

Conclusions

Within the limitations of this study, the present findings indicate that adjunctive HBO and EGCG/BMP-2 could be beneficial for new bone formation in rat calvarial defects.

Late-term healing in an augmented sinus with different ratios of biphasic calcium phosphate: a pilot study using a rabbit sinus model

PURPOSE

The aim of this pilot study was to determine the osteoconductivity and dimensional stability of augmented sinuses using different ratios of biphasic calcium phosphate (BCP) in a rabbit sinus model.

METHODS

Each sinus of New Zealand white rabbits (2.5-3.5 kg) was assigned to one of two groups: BCP with a hydroxyapatite to β-tricalcium phosphate (HA:β-TCP) ratio of 70:30 (group TCP30) and BCP with an HA:β-TCP ratio of 30:70 (group TCP70). After preparing a window in the antral wall of a sinus, the Schneiderian membrane was elevated, and the applicable material was grafted. A fluorochrome calcein green was injected five days before euthanizing the animals at four months post-surgery. The specimens were analyzed histologically, histomorphometrically, and by using micro-computed tomography (micro-CT).

RESULTS

Micro-CT analysis revealed that the total augmented volume and the new bone volume did not differ significantly between the two groups whereas the resorption of materials was greater in the TCP70 group. The trabecular thickness, number, and separation also did not differ significantly between the two groups. Histomorphometrically, the areas of total augmentation, new bone, and residual material, as well as the ratio of new-bone-material contact did not differ significantly between the groups. Histologically, the residual particles were more scattered in the TCP70 group than in the TCP30 group. The fluorescence of the calcein green did not differ notably between the two groups.

CONCLUSIONS

The osteoconductivity and dimensional stability of the two BCPs with different ratios tested in this study were comparable after four months of healing. Therefore, we conclude that both BCPs show promise as a bone substitute for sinus augmentation.

A Clinical Evaluation of Biphasic Calcium Phosphate Alloplast with and without a Flowable Bioabsorbable Guided Tissue Regeneration Barrier in the Treatment of Mandibular Molar Class II Furcation Defects

BACKGROUND

Guided tissue regeneration (GTR) therapy has shown good results in the management of mandibular molar class II furcation defects. Advances in biomaterial sciences have developed alloplastic bone replacement graft materials and bioabsorbable GTR barrier membranes with good biologic response and handling properties. The aim of this study was to compare the attachment gain and the bone fill obtained with an alloplast [biphasic calcium phosphate (BCP) 60% hydroxyapatite (HA) and 40% beta tricalcium phosphate (b-TCP)] with and without a bioabsorbable GTR barrier [flowable poly (DL-lactide) (PLA) dissolved in N-methyl-2-pyrrolidone (NMP)] in the treatment of mandibular molar class II furcation defects.

MATERIALS AND METHODS

A total of 20 class II furcation defects were treated in 16 patients with chronic periodontitis in a comparative study. Ten defects were treated with Camceram(®) (BCP 60% HA and 40% - TCP) bone replacement graft material (group I) and 10 defects with a combination of Camceram® bone replacement graft material with Atrisorb® Freeflow™, bio-absorbable GTR barrier (flowable PLA dissolved in NMP) (group II). At baseline and at 6 months postsurgery, clinical parameters of vertical probing depth (PD) and horizontal probing depth (P-H), clinical attachment level (CAL), gingival recession (GR), and vertical depth of furcation defect (VDF) and horizontal depth of furcation defect (BP-H) were evaluated.

RESULTS

Statistical analysis was done with the Statistical Package for Social Sciences (SPSS) program. Intergroup comparisons made at 6 months postsurgery by unpaired Student's t-test showed mean reduction in PD in group I was 3.10 ± 0.73 mm and in group II was 3.20 ± 1.03 mm (p > 0.05). Mean reduction in P-H in group I was 1.60 ± 0.69 mm and in group II was 1.90 ± 0.73 mm (p > 0.05). Gain in CAL in group I was 2.80 ± 1.03 mm and in group II was 2.90 ± 0.94 mm (p > 0.05). Change in GR in group I was -0.30 ± 0.48 mm and in group II was -0.30 ± 0.48 (p > 0.05). Reduction in VDF in group I was 1.30 ± 0.67 mm and in group II was 1.80 ± 0.63 mm (p ≤ 0.01). Reduction in BP-H in group I was 1.30 ± 0.67 mm and in group II was 1.90 ± 0.73 mm (p ≤ 0.05).

CONCLUSION

It was concluded that the combination technique of BCP alloplast with a flowable bioabsorbable GTR barrier led to better results in regard to defect bone fill as compared with when the BCP alloplast alone was used.

Effect of biphasic calcium phosphate scaffold porosities on odontogenic differentiation of human dental pulp cells

Calcium phosphates (CaP) of different porosities have been widely and successfully used as scaffolds with osteoblast cells for bone tissue regeneration. However, the effects of scaffold porosities on cell viability and differentiation of human dental pulp cells for dentin tissue regeneration are not well known. In this study, biphasic calcium phosphate (BCP) scaffolds of 20/80 hydroxyapatite to beta tricalcium phosphate ratio with a mean pore size of 300 μm were prepared into BCP1, BCP2, BCP3, and BCP4 of 25%, 50%, 65%, and 75% of total porosities, respectively. The extracts of these scaffolds were assessed with regard to cell viability, proliferation, and differentiation of human dental pulp cells. The high alkalinity, and more calcium and phosphate ions release that were exhibited by BCP3 and BCP4 decreased the viability and proliferation of human dental pulp cells as compared to BCP1 and BCP2. BCP2 significantly increased both cell viability and cell proliferation. However, the cells cultured with BCP3 extract revealed high alkaline phosphatase (ALP) activity and high expression of odontoblast related genes, collagen type I alpha 1, dentin matrix protein-1, and dentin sialophosphoprotein as compared to that cultured with BCP1, BCP2, and BCP4 extracts. The results highlight the effect of different scaffold porosities on the cell microenvironment and demonstrate that BCP3 scaffold of 65% porosity can support human dental pulp cells differentiation for dentin tissue regeneration.

Long and short range order structural analysis of In-situ formed biphasic calcium phosphates

BACKGROUND

Biphasic calcium phosphates (BCP) have attracted considerable attention as a bone graft substitute. In this study, BCP were prepared by aqueous co-precipitation and calcination method. The crystal phases of in-situ formed BCP consisting of hydroxyapatite (HAp) and β-tricalcium phosphate (β-TCP) were controlled by the degree of calcium deficiency of precursors. The long and short range order structures of biphasic mixtures was investigated using Rietveld refinement technique and high resolution Raman spectroscopy. The refined structural parameters of in-situ formed BCP confirmed that all the investigated structures have crystallized in the corresponding hexagonal (space group P63/m) and rhombohedral (space group R3c) structures.

RESULTS

The crystal phases, Ca/P molar ratio, and lattice parameters of in-situ formed BCP consisting of HAp and β-TCP were controlled by the degree of calcium deficiency of calcium phosphate precursors. The significant short range order structural change of BCP was determined by Raman analysis.

CONCLUSIONS

The long and short range order structural changes of in-situ formed BCP might be due to the coexistence of β-TCP and HAp crystal phases.

Comparative evaluation of biphasic calcium phosphate and biphasic calcium phosphate collagen composite on osteoconductive potency in rabbit calvarial defect

BACKGROUND

The aim of this study was to determine the osteoconductivity of biphasic calcium phosphate collagen composite (BCPC) in rabbit calvarial defect model by comparing with biphasic calcium phosphate (BCP). Four 8 mm diameter bicortical calvarial defects were made in ten rabbits. Each of the defects was randomly assigned and filled with 1) collagen sponge, 2) BCP, 3) BCPC, and 4) nothing as control. The animals were sacrificed at either 2 weeks (n = 5) or 8 weeks (n = 5) healing period.

RESULTS

All groups showed wedge shaped new bone formation limited to the area of the defect margin at both healing periods. The amounts of new bone and defect closure were similar among all groups. In the control and collagen sponge group, the center of the defect was depressed by surrounding tissues. In contrast, in BCP and BCPC group, the center of the defect did not depressed and the grafted materials maintained the space. And the augmented area was significantly higher in BCP and BCPC group compared to the control and collagen sponge group at both healing periods (p < 0.05).

CONCLUSIONS

The BCPC and BCP demonstrated proper space maintaining capacity and osteoconductive property, suggesting BCPC can be efficiently utilized in various clinical situations.

Effect of different calcium phosphate scaffold ratios on odontogenic differentiation of human dental pulp cells

Calcium phosphate (CaP) scaffolds have been widely and successfully used with osteoblast cells for bone tissue regeneration. However, it is necessary to investigate the effects of these scaffolds on odontoblast cells' proliferation and differentiation for dentin tissue regeneration. In this study, three different hydroxyapatite (HA) to beta tricalcium phosphate (β-TCP) ratios of biphasic calcium phosphate (BCP) scaffolds, BCP20, BCP50, and BCP80, with a mean pore size of 300μm and 65% porosity were prepared from phosphoric acid (H2PO4) and calcium carbonate (CaCO3) sintered at 1000°C for 2h. The extracts of these scaffolds were assessed with regard to cell viability and differentiation of odontoblasts. The high alkalinity, more calcium, and phosphate ions released that were exhibited by BCP20 decreased the viability of human dental pulp cells (HDPCs) as compared to BCP50 and BCP80. However, the cells cultured with BCP20 extract expressed high alkaline phosphatase activity and high expression level of bone sialoprotein (BSP), dental matrix protein-1 (DMP-1), and dentin sialophosphoprotein (DSPP) genes as compared to that cultured with BCP50 and BCP80 extracts. The results highlighted the effect of different scaffold ratios on the cell microenvironment and demonstrated that BCP20 scaffold can support HDPC differentiation for dentin tissue regeneration.

Nanoscale surface characterization of biphasic calcium phosphate, with comparisons to calcium hydroxyapatite and β-tricalcium phosphate bioceramics

OBJECTIVES

It is our aim to understand the mechanisms that make calcium phosphates, such as bioactive calcium hydroxyapatite (HA), and biphasic calcium (BCP) and β-tricalcium (β-TCP) phosphates, desirable for a variety of biological applications, such as the filling of bone defects.

METHODS

Here, we have characterized these materials by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR), time-of-flight secondary ion mass spectroscopy (TOF-SIMS) and laser granulometry.

RESULTS

SEM shows clearly that BCP is a matrix made of macro-organized microstructure, giving insight to the specially chosen composition of the BCP that offers both an adequate scaffold and good porosity for further bone growth. As revealed by laser granulometry, the particles exhibit a homogeneous size distribution, centered at a value somewhat larger than the expected 500 μm. XPS has revealed the presence of adventitious carbon at all sample surfaces, and has shown that Ca/P and O/Ca ratios in the outer layers of all the samples differ significantly from those expected. A peak-by-peak XPS comparison for all samples has revealed that TCP and BCP are distinct from one another in the relative intensities of their oxygen peaks. The PO3(-)/PO2(-) and CaOH+/Ca+ TOF-SIMS intensity ratios were used to distinguish among the samples, and to demonstrate that the OH- fragment, present in all the samples, is not formed during fragmentation but exists at the sample surface, probably as a contaminant.

CONCLUSIONS

This study provides substantial insight into the nanoscale surface properties of BCP, HA and β-TCP. Further research is required to help identify the effect of surfaces of these bioceramics with proteins and several biological fluids.

CLINICAL RELEVANCE

The biological performance of implanted synthetic graft bone biomaterials is strongly influenced by their nanosurface characteristics, the structures and properties of the outer layer of the biomaterial.

Gelation behavior of in situ forming gels based on HPMC and biphasic calcium phosphate nanoparticles

In this study, in situ forming gels are prepared using biphasic calcium phosphate (BCP) as filler and hydroxypropyl methylcellulose (HPMC) as a matrix exhibiting temperature-sensitive behavior. BCP was composed of β-tricalcium phosphate (β-TCP) with plate-like morphology and nano-sized hyadroxyapatite (HAp). Gel permeation chromatography (GPC) and rheological results showed that low molecular weight HPMC had lower gelation temperature. Effects of BCP content and HAp/β-TCP ratio on rheological behavior of the gels were investigated. According to the results, all samples showed a pseudoplastic behavior and their viscosity increased with increasing mineral phase, especially β-tricalcium phosphate. In order to investigate interaction mechanisms between the mineral phase and polymer and also the effects of ion release, particle size, hydrophobisity, and hydrophilisity, hydrophobic and hydrophilic silica with different particle sizes were also utilized. Results showed that factors affecting the hydrophobisity and hydrophilisity of solution may influence the rheological properties.

Biphasic calcium phosphate in periapical surgery

Calcium phosphate ceramics like hydroxyapatite and beta -tricalcium phosphate (beta -TCP) possess mineral composition that closely resembles that of the bone. They can be good bone substitutes due to their excellent biocompatibility. Biphasic calcium phosphate is a bone substitute which is a mixture of hydroxyapatite and beta -tricalcium phosphate in fixed ratios. Studies have demonstrated the osteoconductive potential of this composition. This paper highlights the clinical use of biphasic calcium phosphate as a bone substitute in periapical surgery.