Development of .BETA.-tricalcium Phosphate/Collagen Sponge Composite for Bone Regeneration

Transformable Carbonate Apatite Chains as a Novel Type of Bone Graft

The aging global population is generating an ever-increasing demand for bone regeneration. Various materials, including blocks, granules, and sponges, are developed for bone regeneration. However, blocks require troublesome shaping and exhibit poor bone-defect conformities; granules migrate into the surrounding tissues during and after filling of the defect, causing handling difficulties and complications; and sponges contain polymers that are subject to religious restrictions, lack osteoconductivity, and may cause inflammation and allergies. Herein, carbonate apatite chains that overcome the limitations of conventional materials are presented. Although carbonate apatite granules migrate, causing inflammation and ectopic calcification, the chains remain in the defects without causing any complications. The chains conform to the defect shape and transform into 3D porous structures, resulting in faster bone regeneration than that observed using granules. Thus, these findings indicate that even traditional calcium phosphates materials can be converted to state-of-the-art materials via shape control.

A New Approach to Implant Stability Using a Flexible Synthetic Silicate-Additive Beta-Tricalcium Phosphate-Poly(D,L-lactide-co-caprolactone) Bone Graft: An In Vitro Study

The aim of this study was to evaluate the use of a flexible synthetic polymer bone graft to provide implant stability during implant placement in a dense cortical bone model. In the control group (Group 1), sockets were prepared on polyurethane blocks according to the standard implant socket drilling protocol; both oversizing and deepening were applied in Group 2; and only oversizing was applied in Group 3. In Groups 2 and 3, flexible synthetic polymer bone grafts were placed in the sockets prior to implant placement. The implants were placed at the bone level in all groups. The highest torque value obtained was recorded as the insertion torque. In this study, 75 implant sites were included across three groups. The torque values of the implants in the control group were significantly higher than those of the implants with the oversized and deepened sockets and the oversized-only sockets (p < 0.05; p < 0.01). The torque values of the implants with the oversized and deepened sockets were significantly higher than those of the implants with the oversized-only sockets (p < 0.01). In this study, a flexible synthetic polymer bone graft was shown to be effective in achieving implant stability in the management of implants where there has been a loss of primary stability.

Carbonate apatite versus β-tricalcium phosphate for rat vertical bone augmentation: A comparison of bioresorbable bone substitutes using polytetrafluoroethylene tubes

This study radiologically and histologically compared two bioresorbable bone substitutes with different compositions carbonate apatite (Cytrans® Granules; CGs) and β-tricalcium phosphate (β-TCP) for vertical bone augmentation on a rat skull using a polytetrafluoroethylene (PTFE) tubes. This PTFE tube was placed at the center of the skull, fixed with Super Bond, and augmented with CGs or β-TCP granules. Specimens with surrounding tissue were harvested at 4, 8, and 12 weeks postoperatively, and radiological and histological evaluations were performed. The bone volume to total volume ratio (BV/TV) of the β-TCP-implanted group was markedly higher than that of the CG-implanted group at 4 and 12 weeks postoperatively. Compared to CGs, β-TCP exhibited the ability to form blood vessels into the graft material for a short period after transplantation, as well as an elevated production of collagen into β-TCP granules during the bone formation process.

Functional β-TCP/MnO2 /PCL artificial periosteum promoting osteogenic differentiation of BMSCs by reducing locally reactive oxygen species level

Segmental bone defects caused by trauma, tumor resection or congenital malformations are often reconstructed with autologous, allogeneic bone grafts or artificial bone materials, of which, about 5% ~ 10% will have delayed healing or even nonunion of fractures. The loss of periosteum and excessive accumulation of ROS in fracture site leads to the aging of osteoblasts and the decline of their proliferation and differentiation, thus affecting the fracture healing process. In this study, we prepared a functional modified artificial periosteum β-TCP/MnO2 /PCL(β-TMP) by electrospinning with a function of catalyzing decomposition of H2 O2 . We examined the surface morphology of β-TMP, the concentration of Ca, P and Mn of β-TMP, as well as the diameter distribution range of nanofibers on β-TMP. Through X-ray diffraction patterns and Fourier transform infrared spectra, β-TMP was characterized and its hydrophilicity was tested. The release of Mn2+ and Ca2+ of 0.1 and 0.05% β-TMP in different pH values (7.4 and 5.5) determined by ICP. We also identified that β-TMP could reduce the level of ROS in cells by lowering the level of H2 O2 . 0%, 0.05% and 0.1% β-TMP displayed good cell compatibility, cell adhesion and cellular morphology in the condition with or without H2 O2 . 0.5% β-TMP showed compromised cell compatibility in normal condition, however, the compromised phenotypes could be partially rescued in the present of H2 O2 . Compared with 0%, 0.05% and 0.1% β-TMP displayed higher osteoblastic differentiation with or without H2 O2 in BMSCs as well as in MG-63. In sum, β-TMP helped osteogenesis and promoted repair of bone defects.

The influence of periostin on osteoblastic adhesion and proliferation on collagen matrices - An in vitro study

Purpose:

The purpose of the study was to evaluate the ability of periostin when impregnated onto varied collagen matrices to influence osteoblast cell adhesion, proliferation, and activity.

Materials and Methods:

Saos-2 osteoblast cells were cultured and seeded onto two different collagen matrices as follows: Group A: absorbable collagen sponge (ACS), Group B: ACS impregnated with recombinant human periostin, Group C: nanocrystalline hydroxyapatite collagen (NcHC), and Group D: NcHC impregnated with recombinanant human periostin. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was performed to evaluate cell viability as well as adhesion and proliferation on 2^nd, 5^th, and 7^th day. Osteoblast activity was studied using alkaline phosphatase (ALP) assay for the study groups.

Results:

The periostin-treated absorbable collagen matrices showed a statistically significant increase in the osteoblast adhesion compared to periostin-treated NcHC on days 2, 5, and 7 (P < 0.001). The osteoblast activity as evaluated by ALP assay showed that there is increased activity in the periostin-treated ACS compared to the periostin-treated NcHC.

Conclusion:

From the observations of this study, it is evident that Periostin has a significant role in the modulating cellular response of the osteoblast cells. Further, incorporation of periostin into the ACS has been shown to increase the cell viability, proliferation, and adhesion of osteoblast-like Saos-2 cells.

A Review of Bioactive Glass/Natural Polymer Composites: State of the Art

Collagen, gelatin, silk fibroin, hyaluronic acid, chitosan, alginate, and cellulose are biocompatible and non-cytotoxic, being attractive natural polymers for medical devices for both soft and hard tissues. However, such natural polymers have low bioactivity and poor mechanical properties, which limit their applications. To tackle these drawbacks, collagen, gelatin, silk fibroin, hyaluronic acid, chitosan, alginate, and cellulose can be combined with bioactive glass (BG) nanoparticles and microparticles to produce composites. The incorporation of BGs improves the mechanical properties of the final system as well as its bioactivity and regenerative potential. Indeed, several studies have demonstrated that polymer/BG composites may improve angiogenesis, neo-vascularization, cells adhesion, and proliferation. This review presents the state of the art and future perspectives of collagen, gelatin, silk fibroin, hyaluronic acid, chitosan, alginate, and cellulose matrices combined with BG particles to develop composites such as scaffolds, injectable fillers, membranes, hydrogels, and coatings. Emphasis is devoted to the biological potentialities of these hybrid systems, which look rather promising toward a wide spectrum of applications.

Examination of β-TCP/collagen composite in bone defects without periosteum in dogs: a histological and cast model evaluation

After tooth extraction, the alveolar ridge is absorbed and changes shape. Recently, socket preservation has been proposed to prevent alveolar ridge absorption. However, there are few reports of socket preservation in a model without the periosteum, and alveolar bone regeneration and resorption inhibitory effects in this type of model remain unclear. Therefore, in this study, we conducted socket preservation at the bone defect without the periosteum using a canine model. Ten beagle dogs were extracted. A 5 mm × 7 mm × 4 mm bone defect was created without the periosteum. Defects were filled with beta-tricalcium phosphate (β-TCP)/collagen (Col), β-TCP, collagen, or left intact (Control). The observation periods were 4 and 8 weeks (n = 5 per group). Evaluations were made of the newly formed bone area, residual granular area, horizontal width and vertical dimensional change. The newly formed bone area at 4 weeks after surgery in TCP/Col, Collagen, β-TCP, and Control groups was 21.50%, 17.26%, 18.22%, and 17.47%. Compared to the control group, the TCP/Col group showed a significant difference in bone regeneration and horizontal width. TCP/Col is suggested to be effective for bone regeneration and suppression of alveolar ridge resorption in the bone defect periosteum removal model.

Preparation and Characterization of Nanocomposite Scaffolds (Collagen/β-TCP/SrO) for Bone Tissue Engineering

Background

Nowadays, production of nanocomposite scaffolds based on natural biopolymer, bioceramic, and metal ions is a growing field of research due to the potential for bone tissue engineering applications.

Methods

In this study, a nanocomposite scaffold for bone tissue engineering was successfully prepared using collagen (COL), beta-tricalcium phosphate (β-TCP) and strontium oxide (SrO). A composition of β-TCP (4.9 g) was prepared by doping with SrO (0.05 g). Biocompatible porous nanocomposite scaffolds were prepared by freeze-drying in different formulations [COL, COL/β-TCP (1:2 w/w), and COL/β-TCP-Sr (1:2 w/w)] to be used as a provisional matrix or scaffold for bone tissue engineering. The nanoparticles were characterized by X-ray diffraction, Fourier transforms infrared spectroscopy and energy dispersive spectroscopy. Moreover, the prepared scaffolds were characterized by physicochemical properties, such as porosity, swelling ratio, biodegradation, mechanical properties, and biomineralization.

Results

All the scaffolds had a microporous structure with high porosity (~ 95-99%) and appropriate pore size (100-200 μm). COL/β-TCP-Sr scaffolds had the compressive modulus (213.44 ± 0.47 kPa) higher than that of COL/β-TCP (33.14 ± 1.77 kPa). In vitro cytocompatibility, cell attachment and alkaline phosphatase (ALP) activity studies performed using rat bone marrow mesenchymal stem cells. Addition of β-TCP-Sr to collagen scaffolds increased ALP activity by 1.33-1.79 and 2.92-4.57 folds after 7 and 14 days of culture, respectively.

Conclusion

In summary, it was found that the incorporation of Sr into the collagen-β-TCP scaffolds has a great potential for bone tissue engineering applications.

Effects of three-dimensionally printed polycaprolactone/β-tricalcium phosphate scaffold on osteogenic differentiation of adipose tissue- and bone marrow-derived stem cells

BACKGROUND

Autogenous bone grafts have several limitations including donor-site problems and insufficient bone volume. To address these limitations, research on bone regeneration is being conducted actively. In this study, we investigate the effects of a three-dimensionally (3D) printed polycaprolactone (PCL)/tricalcium phosphate (TCP) scaffold on the osteogenic differentiation potential of adipose tissue-derived stem cells (ADSCs) and bone marrow-derived stem cells (BMSCs).

METHODS

We investigated the extent of osteogenic differentiation on the first and tenth day and fourth week after cell culture. Cytotoxicity of the 3D printed PCL/β-TCP scaffold was evaluated by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay, prior to osteogenic differentiation analysis. ADSCs and BMSCs were divided into three groups: C, only cultured cells; M, cells cultured in the 3D printed PCL/β-TCP scaffold; D, cells cultured in the 3D printed PCL/β-TCP scaffold with a bone differentiation medium. Alkaline phosphatase (ALP) activity assay, von Kossa staining, reverse transcription-polymerase chain reaction (RT-PCR), and Western blotting were performed for comparative analysis.

RESULTS

ALP assay and von Kossa staining revealed that group M had higher levels of osteogenic differentiation compared to group C. RT-PCR showed that gene expression was higher in group M than in group C, indicating that, compared to group C, osteogenic differentiation was more extensive in group M. Expression levels of proteins involved in ossification were higher in group M, as per the Western blotting results.

CONCLUSION

Osteogenic differentiation was increased in mesenchymal stromal cells (MSCs) cultured in the 3D printed PCL/TCP scaffold compared to the control group. Osteogenic differentiation activity of MSCs cultured in the 3D printed PCL/TCP scaffold was lower than that of cells cultured on the scaffold in bone differentiation medium. Collectively, these results indicate that the 3D printed PCL/TCP scaffold promoted osteogenic differentiation of MSCs and may be widely used for bone tissue engineering.

Preparation of flexible bone tissue scaffold utilizing sea urchin test and collagen

Gonads of sea urchin are consumed in Japan and some countries as food and most parts including its tests are discarded as marine wastes. Therefore, utilization of them as functional materials would reduce the waste as well as encourage Japanese fishery. In this study, magnesium containing calcite granules collected from sea urchin tests were hydrothermally phosphatized and the obtained granules were identified as approximately 82% in mass of magnesium containing β-tricalcium phosphate and 18% in mass of nonstoichiometric hydroxyapatite, i.e., a biphasic calcium phosphate, maintaining the original porous network. Shape-controlled scaffolds were fabricated with the obtained biphasic calcium phosphate granules and collagen. The scaffolds showed good open porosity (83.84%) and adequate mechanical properties for handling during cell culture and subsequent operations. The MG-63 cells showed higher proliferation and osteogenic differentiation in comparison to a control material, the collagen sponge with the same size. Furthermore, cell viability assay proved that the scaffolds were not cytotoxic. These results suggest that scaffold prepared using sea urchin test derived calcium phosphate and collagen could be a potential candidate of bone void fillers for non-load bearing defects in bone reconstruction as well as scaffolds for bone tissue engineering.

Osteogenesis for postoperative temporal bone defects using human ear adipose-derived stromal cells and tissue engineering: An animal model study

Mastoidectomy, the removal of infected mastoid bones, is a common surgical procedure for the treatment of chronic otitis media. Persistent and recurrent otorrhea and accumulation of keratin debris following open cavity mastoidectomy are still bothersome issues for both patients and otologists. In this study, we used human ear adipose-derived stromal cells (hEASCs) in combination with polycaprolactone (PCL) scaffolds and osteogenic differentiation medium (ODM) to regenerate temporal bone defects. The hEASCs showed stem cell phenotypes, and these characteristics were maintained up to passage 5. Mastoid bulla and cranial bone defects were induced in Sprague-Dawley rats using AgNO₃ and burr hole drilling, respectively, and the rats were then divided into five groups: (1) control, (2) hEASCs, (3) hEASCs + ODM, (4) hEASCs + PCL scaffolds, and (5) hEASCs + PCL scaffolds + ODM. Osteogenesis was evaluated by micro-computed tomography and histology. Compared with the control group, the groups transplanted with hEASCs and PCL scaffolds had significantly higher bone formation along the periphery of the mastoid bulla area. Moreover, ODM synergistically enhanced bone formation in mastoid bulla defects. Our results suggest that combining hEASCs with PCL scaffolds represents a promising method for anatomical and functional reconstruction of postoperative temporal bone defects following mastoidectomy. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3493-3501, 2017.

Bone regeneration with a collagen model polypeptides/α-tricalcium phosphate sponge in a canine tibia defect model

INTRODUCTION

We evaluated the effects of synthesized collagen model polypeptides consisting of a proline-hydroxyproline-glycine (poly(PHG)) sequence combined with porous alpha-tricalcium phosphate (α-TCP) particles on bone formation in a canine tibia defect model.

MATERIALS AND METHODS

The porous α-TCP particles were mixed with a poly(PHG) solution, and the obtained sponge was then cross-linked and characterized by x-ray diffraction and scanning electron microscopy. Tibia defects were analyzed in 12 healthy beagles using microcomputed tomography and histological evaluation.

RESULTS

At 2 and 4 weeks, the volume density of new bone was higher in the poly(PHG)/α-TCP group than in poly(PHG) alone group (P < 0.05); however, there was no difference at 8 weeks (P > 0.05). Histological evaluation at 4 weeks after implantation revealed that the poly(PHG) had degraded, and newly formed bone was present on the surface of the α-TCP particles. At 8 weeks, continuous cortical bone formation with a Haversian structure covered the top of the bone defects in both groups.

CONCLUSION

This study demonstrates that the composite created using porous α-TCP particles and poly(PHG) is sufficiently adaptable for treating bone defects.

Porous Alpha-Tricalcium Phosphate with Immobilized Basic Fibroblast Growth Factor Enhances Bone Regeneration in a Canine Mandibular Bone Defect Model

The effect of porous alpha-tricalcium phosphate (α-TCP) with immobilized basic fibroblast growth factor (bFGF) on bone regeneration was evaluated in a canine mandibular bone defect model. Identical bone defects were made in the canine mandible; six defects in each animal were filled with porous α-TCP with bFGF bound via heparin (bFGF group), whereas the other was filled with unmodified porous α-TCP (control group). Micro-computed tomography and histological evaluation were performed two, four and eight weeks after implantation. The bone mineral density of the bFGF group was higher than that of the control group at each time point (p < 0.05), and the bone mineral content of the bFGF group was higher than that of the control group at four and eight weeks (p < 0.05). Histological evaluation two weeks after implantation revealed that the porous α-TCP had degraded and bone had formed on the surface of α-TCP particles in the bFGF group. At eight weeks, continuous cortical bone with a Haversian structure covered the top of bone defects in the bFGF group. These findings demonstrate that porous α-TCP with immobilized bFGF can promote bone regeneration.

Novel bioceramic-reinforced hydrogel for alveolar bone regeneration

The osseointegration of dental implants and their consequent long-term success is guaranteed by the presence, in the extraction site, of healthy and sufficient alveolar bone. Bone deficiencies may be the result of extraction traumas, periodontal disease and infection. In these cases, placement of titanium implants is contraindicated until a vertical bone augmentation is obtained. This goal is achieved using bone graft materials, which should simulate extracellular matrix (ECM), in order to promote osteoblast proliferation and fill the void, maintaining the space without collapsing until the new bone is formed. In this work, we design, develop and characterize a novel, moldable chitosan-pectin hydrogel reinforced by biphasic calcium phosphate particles with size in the range of 100-300μm. The polysaccharide nature of the hydrogel mimics the ECM of natural bone, and the ceramic particles promote high osteoblast proliferation, assessed by Scanning Electron Microscopy analysis. Swelling properties allow significant adsorption of water solution (up to 200% of solution content) so that the bone defect space can be filled by the material in an in vivo scenario. The incorporation of ceramic particles makes the material stable at different pH and increases the compressive elastic modulus, toughness and ultimate tensile strength. Furthermore, cell studies with SAOS-2 human osteoblastic cell line show high cell proliferation and adhesion already after 72h, and the presence of ceramic particles increases the expression of alkaline phosphatase activity after 1week. These results suggest a great potential of the developed moldable biomaterials for the regeneration of the alveolar bone.

STATEMENT OF SIGNIFICANCE

The positive fate of a surgical procedure involving the insertion of a titanium screw still depends on the quality and quantity of alveolar bone which is present in the extraction site. Available materials are basically hard scaffold materials with un-predictable behavior in different condition and difficult shaping properties. In this work we developed a novel pectin-chitosan hydrogel reinforced with ceramic particles. Polysaccharides simulate the extracellular matrix of natural bone and the extensive in vitro cells culture study allows to assess that the incorporation of the ceramic particles promote a pro-osteogenic response. Shape control, easy adaption of the extraction site, predictable behavior in different environment condition, swelling properties and an anti-inflammatory response are the significant characteristics of the developed biomaterial.

Mandibular Tissue Engineering: Past, Present, Future

Almost 2 decades ago, the senior author's (M.T.J.) first article was with our mentor, Dr Leonard B. Kaban, a review article titled "Distraction Osteogenesis: Past, Present, Future." In 1998, many thought it would be impossible to have a remotely activated, small, curvilinear distractor that could be placed using endoscopic techniques. Currently, a U.S. patent for a curvilinear automated device and endoscopic techniques for minimally invasive access for jaw reconstruction exist. With minimally invasive access for jaw reconstruction, the burden to decrease donor site morbidity has increased. Distraction osteogenesis (DO) is an in vivo form of tissue engineering. The DO technique eliminates a donor site, is less invasive, requires a shorter operative time than usual procedures, and can be used for multiple reconstruction applications. Tissue engineering could further reduce morbidity and cost and increase treatment availability. The purpose of the present report was to review our experience with tissue engineering of bone: the past, present, and our vision for the future. The present report serves as a tribute to our mentor and acknowledges Dr Kaban for his incessant tutelage, guidance, wisdom, and boundless vision.

Biocompatible 3D Matrix with Antimicrobial Properties

The aim of this study was to develop, characterize and assess the biological activity of a new regenerative 3D matrix with antimicrobial properties, based on collagen (COLL), hydroxyapatite (HAp), β-cyclodextrin (β-CD) and usnic acid (UA). The prepared 3D matrix was characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Microscopy (FT-IRM), Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD). In vitro qualitative and quantitative analyses performed on cultured diploid cells demonstrated that the 3D matrix is biocompatible, allowing the normal development and growth of MG-63 osteoblast-like cells and exhibited an antimicrobial effect, especially on the Staphylococcus aureus strain, explained by the particular higher inhibitory activity of usnic acid (UA) against Gram positive bacterial strains. Our data strongly recommend the obtained 3D matrix to be used as a successful alternative for the fabrication of three dimensional (3D) anti-infective regeneration matrix for bone tissue engineering.

A MSCs-laden polycaprolactone/collagen scaffold for bone tissue regeneration

A mesenchymal stem cell (MSC)-laden scaffold was designed for use in mastoid obliteration.

Collagen/Beta-Tricalcium Phosphate Based Synthetic Bone Grafts via Dehydrothermal Processing

Millions of patients worldwide remain inadequately treated for bone defects related to factors such as disease or trauma. The drawbacks of metallic implant and autograft/allograft use have steered therapeutic approaches towards tissue engineering solutions involving tissue regeneration scaffolds. This study proposes a composite scaffold with properties tailored to address the macro- and microenvironmental conditions deemed necessary for successful regeneration of bone in defect areas. The biodegradable scaffold composed of porous beta-tricalcium phosphate particles and collagen type I fibers is prepared from a mixture of collagen type-I and β-tricalcium phosphate (β-TCP) particles via lyophilization, followed by dehydrothermal (DHT) processing. The effects of both sterilization via gamma radiation and the use of DHT processing to achieve cross-linking were investigated. The impact of the chosen fabrication methods on scaffold microstructure and β-TCP particle-collagen fiber combinations were analyzed using X-ray diffractometry (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and microcomputerized tomography (µ-CT). Electron spinning resonance (ESR) analysis was used to investigate free radicals formation following sterilization. Results revealed that the highly porous (65% porosity at an average of 100 µm pore size), mechanically adequate, and biocompatible scaffolds can be utilized for bone defect repairs.

Effects of proliferation and differentiation of mesenchymal stem cells on compressive mechanical behavior of collagen/β-TCP composite scaffold

The primary aim of this study is to characterize the effects of cell culture on the compressive mechanical behavior of the collagen/β-tricalcium phosphate (TCP) composite scaffold. The composite and pure collagen scaffolds were fabricated by the solid-liquid phase separation technique and the subsequent freeze-drying method. Rat bone marrow mesenchymal stem cells (rMSCs) were then cultured in these scaffolds up to 28 days. Compression test of the scaffolds with rMSCs were conducted periodically. Biological properties such as cell number, alkaline phosphatase (ALP) activity, and gene expressions of osteogenetic bone markers were evaluated during cell culture. The microstructural changes in the scaffolds during cell culture were also examined using a scanning electron microscope. The compressive elastic modulus was then correlated with those of the biological properties and microstructures to understand the mechanism of variational behavior of the macroscopic elastic property. The composite scaffold exhibited higher ALP activity and more active generation of osteoblastic markers than the collagen scaffold, indicating that β-TCP can activate the differentiation of rMSCs into osteoblasts and extracellular matrix (ECM) formation such as type I collagen and the following mineralization. The variational behavior of the compressive modulus of the composite scaffold was affected by both the material degradation and the proliferation of cells and the ECM formation. In the first stage, the modulus of the composite scaffold tended to increase due to cell proliferation and the following formation of network structure. In the second stage, the modulus tended to decrease because the material degradation such as ductile deformation of collagen and decomposition of β-TCP were more effective on the property than the ECM formation. In the third stage, active calcification by formation and growth of mineralized nodules resulted in the recovery of modulus. It is concluded that the introduction of β-TCP powder into the porous collagen matrix is very effective to improve the mechanical and biological properties of collagen scaffold prepared for bone tissue engineering. Furthermore, the compressive modulus of the composite scaffold is strongly affected by the material degradation and the ECM formation by stem cells under in vitro culture condition.

Effect of umbilical cord serum coated 3D PCL/alginate scaffold for mastoid obliteration

OBJECTIVE

Human umbilical cord serum (hUCS) has a lot of growth factors. To date, there are no reports on stimulating effect of hUCS in osteogenesis. The purpose of this study is to evaluate enhancing effect of hUCS in osteogenesis by mastoid obliteration combined with bony scaffold.

MATERIALS AND METHODS

The fabrication procedure for obtaining PCL/alginate/hUCS was performed. The bulla obliteration was done using PCL/alginate/hUCS in the experimental group and PCL in the control group. To assess the early active mineralization of new bone formation, guinea pigs of each group received an intraperitoneal infusion with alizarin red at 6 weeks post-surgery. The animals of each group were sacrificed 8 weeks post-surgery. Ex vivo microCT and histologic observation were performed.

RESULTS

MicroCT finding shows more radiopaque change within the pores in the experimental group compared to the control group. Stereomicroscopic and SEM findings show new bone formation of the pores in the experimental group. However, the pores between strands almost all remained in the control group. Corresponding histological observations for the stimulatory effects of hUCS showed osteogenesis in the pores between the strands compared to the control group.

CONCLUSION

Our data suggest that hUCS coated 3D porous PCL scaffold in mastoid obliteration provides enhanced osteogenesis. Therefore, we suggest that our hUCS coated 3D porous PCL could be used in mastoid obliteration in the future.

APPLICATION OF DENDRIMER/PLASMID hBMP-2 COMPLEXES LOADED INTO β-TCP/COLLAGEN SCAFFOLD IN THE TREATMENT OF FEMORAL DEFECTS IN RATS

Purpose: Plasmid loading into scaffolds to enhance sustained release of growth factors is an important focus of regenerative medicine. The aim of this study was to build gene-activated matrices (GAMs) and examine the bone augmentation properties. Methods: Generation 5 polyamidoamine dendrimers (G5 dPAMAM)/plasmid recombinant human bone morphogenetic protein-2 (rhBMP-2) complexes were immobilized into beta-tricalcium phosphate (β-TCP)/type I collagen porous scaffolds. After cultured with rat mesenchymal stem cells (rMSCs), transfection efficiencies were examined. The secretion of rhBMP-2 and alkaline phosphatase (ALP) were detected to evaluate the osteogenic properties. Scanning electron microscopy (SEM) was used to observe attachment and proliferation. Moreover, we applied these GAMs directly into freshly created segmental bone defects in rat femurs, and their osteogenic efficiencies were evaluated. Results: Released plasmid complexes were transfected into stem cells and were expressed, which caused osteogenic differentiations of rat mesenchymal stem cells (rMSCs). SEM analysis showed excellent cell attachment. Bioactivity of plasmid rhBMP-2 was maintained in vivo, and the X-ray observation, histological analysis and immunohistochemistry (IHC) of bone tissue demonstrated that the bone healing in segmental femoral defects was enhanced by implantation of GAMs. Conclusions: Such biomaterials offer therapeutic opportunities in critical-sized bone defects.

Effect of a β-TCP collagen composite bone substitute on healing of drilled bone voids in the distal femoral condyle of rabbits

In this study, we tested the performance and biocompatibility of a composite of β-tricalcium phosphate (β-TCP) to collagen as a bone void filler (Cerasorb(®) Ortho Foam) in a rabbit distal femoral condyle model. β-TCP is a completely resorbable synthetic calcium phosphate and the addition of a collagen matrix couples the osteoconductive effects of the two components. Furthermore, the malleable properties of the implant material during surgical applications for shape control will be enhanced. A critical size defect of 6 mm in diameter and 10 mm in depth was drilled into each distal femur of the rabbits. One hole was filled with the test substance and the other was left empty for control. After 1, 3, and 6 months the animals were killed and the degree of bone healing analyzed. In total, 18 animals were investigated. When the β-TCP composite was used, histological, histomorphometric, and biomechanical evaluations revealed significantly better bone healing in terms of quantity and quality of the newly formed bone. Moreover, no signs of inflammation were observed in the animals and no allergic or foreign body reaction was noted. This suggests high biocompatibility and osteoconductivity of the investigated material to a bone void in an immune responsive species.

Volumetric bone regenerative efficacy of biphasic calcium phosphate-collagen composite block loaded with rhBMP-2 in vertical bone augmentation model of a rabbit calvarium

Block-type biphasic calcium phosphate (BCP) carriers are more effective at delivering recombinant human bone morphogenetic protein-2 (rhBMP-2) in various clinical situations than are particle-type carriers, due to their potential for highly successful three-dimensional bone regeneration. The aim of this study was to confirm the bone-regenerative capabilities of three-dimensional BCP blocks with a low hydroxyapatite/β-tricalcium phosphate ratio (20/80) combined with collagen (10% wt) as an rhBMP-2 delivery system in a craniofacial vertical bone augmentation model. BCP blocks and BCP-collagen blocks (with average macropore sizes of 296 and 390 μm, respectively) with or without rhBMP-2 were fixed with osteosynthesis screws to the calvarial surface of rabbits. After 8 weeks, histologic and histomorphometric analyses were performed to evaluate the resulting new bone area, augmented area, bone density, and degree of integration. The area of new bone was significantly greater in specimens containing rhBMP-2 than in the control group (p < 0.05). Moreover, the area fractions of newly formed bone within the augmented area and a degree of integration between the regenerative bone and the calvarium were both significantly greater in the BCP-collagen/rhBMP-2 group than in the BCP/rhBMP-2 group (p < 0.05), whereas the two carrier systems exhibited similar rhBMP-2 release profiles, with sustained and linear release. The BCP and BCP/rhBMP-2 blocks exhibited excellent structural integrity, with large fragments of residual ceramic. In conclusion, the BCP-collagen composite block exhibited enhanced osteoinductive potential and could be a good candidate as a carrier of rhBMP-2 due to its characteristics of favorable volumetric stability, ease of handling, and excellent remodeling properties.

Effects on bone regeneration when collagen model polypeptides are combined with various sizes of alpha-tricalcium phosphate particles

We evaluated the effects on bone formation of combining synthesized collagen model polypeptides consisting of a Pro-Hyp-Gly [poly(PHG)] sequence and alpha-tricalcium phosphate (α-TCP) particles with various median sizes (large: 580.8 μm; small: 136.2 μm; or large and small mixed: 499.3 μm) in a skull defect model in mini-pigs. Quantitative image analyses for the volume density (VD) of new bone revealed that the VD in each α-TCP group was significantly higher than that in the poly(PHG) control group, with the mixed group showing the highest VD among all the groups at 4 weeks after implantation. Histological assessments revealed that the small α-TCP particles were almost completely degraded at 8 weeks. At 12 weeks, all sizes of α-TCP particles were completely degraded and remodeling of the lamellar bone was observed. The present findings suggest that particle size may influence the success of bone formation in defects.

Biomedical Applications of Biodegradable Polymers

Utilization of polymers as biomaterials has greatly impacted the advancement of modern medicine. Specifically, polymeric biomaterials that are biodegradable provide the significant advantage of being able to be broken down and removed after they have served their function. Applications are wide ranging with degradable polymers being used clinically as surgical sutures and implants. In order to fit functional demand, materials with desired physical, chemical, biological, biomechanical and degradation properties must be selected. Fortunately, a wide range of natural and synthetic degradable polymers has been investigated for biomedical applications with novel materials constantly being developed to meet new challenges. This review summarizes the most recent advances in the field over the past 4 years, specifically highlighting new and interesting discoveries in tissue engineering and drug delivery applications.

Effect of piperacillin-tazobactam coated β-tricalcium phosphate for mastoid obliteration in otitis media

BACKGROUND AND OBJECTIVE

β-Tricalcium phosphate (TCP) has good biodegradability and osteoconductivity as a scaffold material for bone tissue engineering. Both block and granular forms are available; however, it has been associated with risk of infection and exposure. To this end, the study evaluated the effect of piperacillin-tazobactam coated β-TCPs for mastoid obliteration in otitis media.

MATERIALS AND METHODS

Ten guinea pigs were divided into the experimental (piperacillin-tazobactam coated β-TCP granules, n=5) and control groups (uncoated β-TCP granules, n=5). After mastoid obliteration, transtympanic injection with a saline suspension of lipopolysaccharide established inflammation. The animals were sacrificed 5 weeks later. Tissue sections were stained with hematoxylin and eosin and examined.

RESULTS

Encapsulation and formation of fibrous capsule by foreign material in the bulla were not evident. The histological evaluation did not reveal inflammatory cells and fibrosis in the piperacillin-tazobactam coated β-TCP group. In contrast, the control group showed numerous inflammatory cells around the implanted uncoated β-TCP granules and incomplete new bone formation.

CONCLUSION

β-TCP is an effective carrier material for piperacillin-tazobactam. The use of piperacillin-tazobactam coated β-TCP may be optimal for mastoid obliteration.

New approaches in layer by layer synthesis of collagen/hydroxyapatite composite materials

The aim of this work was to increase our understanding of collagen (COLL)/ hydroxyapatite (HA) composite materials; more specifically, we focused on the study of the influence of the precursorconcentrations over the final content of deposited HA. We found that the increase of the precursor concentrations led to better mineralization (on the basis of the content of deposited mineral phase). Regardless of the precursor concentrations, the content of the deposited amount was found to increase with the increase of the number of deposited layers. Quantification of the mineral phase amount was achieved by gravimetric determination. Based on the determined deposition equation the number of layers can be easily determined in order to obtain composite materials with desired content of mineral phase.

Preparation of injectable 3D-formed beta-tricalcium phosphate bead/alginate composite for bone tissue engineering

A novel, injectable bone tissue engineering material was developed that consisted of beta-tricalcium phosphate (beta-TCP) beads as the solid phase and alginate as the gel phase. To prepare the instantaneously formed composite scaffold, an aqueous calcium chloride solution was dried on the surface of beta-TCP beads and crosslinked with an alginic acid sodium solution, thereby forming stable beta-TCP beads and alginate gel which were injectable via a syringe. This biodegradable composite was a three-dimensional (3D) material that could be used as an injectable scaffold for bone tissue engineering. In particular, the composite with 2.0 wt% alginate concentration exhibited a compressive strength of 69 kPa in dry conditions, which was significantly higher than that exhibited by 1.0 wt%. Furthermore, mesenchymal stem cells (MSC) were 3D-cultured within the composite and then investigated for osteogenic markers. MSC-loaded composite was subjected to scanning electron microscope (SEM) examination and implanted subcutaneously for in vivo experiment. Results showed that the scaffold provided support for osteogenic differentiation. In light of the encouraging results obtained, this novel injectable composite material may be useful for bone tissue engineering.

Synthetic octacalcium phosphate augments bone regeneration correlated with its content in collagen scaffold

Previous studies have shown that synthetic octacalcium phosphate (OCP) facilitates in vitro osteoblastic cell differentiation in an OCP dose-dependent manner and that a complex of OCP and collagen (OCP/collagen) enhances critical-sized rat calvaria defects more than OCP alone. The present study was designed to investigate whether the bone regenerative properties of OCP/collagen are augmented in an OCP dose-dependent manner, thereby establishing a suitable composition of this composite as a bone substitute material. OCP/collagens with a wide range of mixing ratios from 23:77 to 83:17, including the previously examined composition (77:23), were prepared by blending granules of OCP with atelocollagen and molded into a disk as an implant. A critical-sized defect was made in rat calvaria, and each disk was implanted into the defect for 4 or 12 weeks and then examined radiographically, histologically, and histomorphometrically. Mouse bone marrow-derived stromal ST-2 cells were cultured in dishes pre-coated with OCP/collagen or OCP alone with different OCP contents to determine the capacity of cell attachment and proliferation up to 14 days. Histological and radiographic examinations showed that newly formed bone was observed in relation to OCP granules within the collagen matrix. Histomorphometric analysis confirmed that increasing the amount of OCP in collagen matrices resulted in progressive enhancement of bone regeneration and that the ratio 83:17 generated the maximum repair level of approximately 64% of the defect at 12 weeks. OCP/collagen promoted the proliferation and attachment of ST-2 cells more than OCP alone regardless of OCP content. Fourier transform infrared spectroscopy analysis of the coatings after the incubation indicated that OCP tended to convert to apatite regardless of the presence of collagen. The present study demonstrated that the osteoconductive characteristics of OCP/collagen can be displayed in an OCP dose-dependent manner. The results suggest that collagen promotes the proliferation and attachment of host osteoblastic cells on OCP/collagen composite implants.

Bone Regeneration of Canine Skull Using Bone Marrow-Derived Stromal Cells and β-Tricalcium Phosphate

OBJECTIVE

The aim of this study was to regenerate high-quality cranial bone using tissue engineering techniques, with subsequent extension to clinical application. Our previous study with a 3-month observation period indicated that a composite scaffold composed primarily of beta-tricalcium phosphate (TCP) had the potential for cranial bone regeneration. In this study, we investigated whether bone marrow derived stromal cells (BSCs) could promote the regeneration of cranial bone as determined after 3 and 6 months.

STUDY DESIGN

The pilot study was conducted with 14 adult beagle dogs.

MATERIALS AND METHODS

Craniotomy was performed in the same manner used clinically. The bone defect (2 x 2 cm) was created at each canine temporoparietal region. The test animals were divided into three groups. In group I, the bone defect was closed by replacing the original free bone flap without filling the residual gaps. In group II, the gap was filled with a composite scaffold consisting of collagen coated beta-TCP and autologous bone fragments with fibrin glue. In group III, autologous cultured BSCs and the composite scaffold were used to fill the gap. The sites of craniotomy were analyzed with three-dimensional computed tomography and histologic examination 3 and 6 months after the operation.

RESULTS

Bone regeneration was observed in groups II and III, with more extensive formation in group III than in group II. In group I, bone regeneration was not observed.

CONCLUSION

This study showed that BSCs have the potential to promote cranial bone regeneration and confirmed the efficacy of a composite scaffold made of beta-TCP and autologous bone fragments with fibrin glue.

The primacy of octacalcium phosphate collagen composites in bone regeneration

We have engineered a scaffold constructed of synthetic octacalcium phosphate (OCP) and porcine collagen sponge (OCP/Col), and reported that OCP/Col drastically enhanced bone regeneration. In this study, we investigated whether OCP/Col would enhance bone regeneration more than beta-tricalcium phosphate (beta-TCP) collagen composite (beta-TCP/Col) or hydroxyapatite (HA) collagen composite (HA/Col). Discs of OCP/Col, beta-TCP/Col, or HA/Col were implanted into critical-sized defects in rat crania and fixed at 4 or 12 weeks after implantation. The newly formed bone and the remaining granules of implants in the defect were determined by histomorphometrical analysis, and radiographic and histological examinations were performed. Statistical analysis showed that the newly formed bone by the implantation of OCP/Col was significantly more than that of beta-TCP/Col or HA/Col. In contrast, the remaining granules in OCP/Col were significantly lower than those in beta-TCP/Col or HA/Col. Bone regeneration by OCP/Col was based on secured calcified collagen and bone nucleation by OCP, whereas bone regeneration by beta-TCP/Col or HA/Col was initiated by poorly calcified collagen and osteoconductivity by beta-TCP or HA. This study showed that the implantation of OCP/Col in a rat cranial defect enhanced more bone regeneration than beta-TCP/Col and HA/Col.

Comparison of Hydrogels in theIn VivoFormation of Tissue-Engineered Bone Using Mesenchymal Stem Cells and Beta-Tricalcium Phosphate

Availability of grafts and morbidity at the donor site limit autologous transplantation in patients requiring bone reconstruction. A tissue-engineering approach can overcome these limitations by producing bone-like tissue of custom shape and size from isolated cells. Several hydrogels facilitate osteogenesis on porous scaffolds; however, the relative suitability of various hydrogels has not been rigorously assessed. Fibrin glue, alginate, and collagen I hydrogels were mixed with swine bone marrow-derived differentiated mesenchymal stem cells (MSCs), applied to 3-dimensionally printed porous beta-tricalcium phosphate (beta-TCP) scaffolds and implanted subcutaneously in nude mice. Although noninvasive assessment of osteogenesis in 3 dimensions is desirable for monitoring new bone formation in vivo, correlations with traditional histological and mechanical testing need to be established. High-resolution volumetric computed tomography (VCT) scanning, histological examination, biomechanical compression testing, and osteonectin (ON) expression were performed on excised scaffolds after 1, 2, 4, and 6 weeks of subcutaneous implantation in mice. Statistical correlation analyses were performed between radiological density, stiffness, and ON expression. Use of collagen I as a hydrogel carrier produced superior bone formation at 6 weeks, as demonstrated using VCT scanning with densities similar to native bone and the highest compression values. Continued contribution of the seeded MSCs was demonstrated using swine-specific messenger ribonucleic acid probes. Radiological density values correlated closely with the results of histological and biomechanical testing and ON expression. High-resolution VCT is a promising method for monitoring osteogenesis.

Preparation and properties of chitosan/calcium phosphate composites for bone repair

Chitosan/calcium phosphate (CaP) composites composed of bioactive calcium phosphate and flexible chitosan were made by a simple mixing-and-heating method. Phase composition, morphology, and mechanical properties--including in-air and in vitro fatigue behavior - were evaluated. Experimental results showed that the chitosan matrix did not affect the crystalline phase of CaP. However, the content of CaP additive affected the three-point bending strength of the composites. A CaP/ chitosan ratio of 5% by mass to volume in the composite achieved the significantly highest bending strength of 45.7 MPa. Stability of chitosan/CaP hybrid composites was apparently affected by in vitro cyclic loading. Nonetheless, when applied a loading stress of 11.4 MPa, the sample containing the optimal 5 mass/vol% CaP lasted 40 minutes in in vitro fatigue test until failure occurred. It was thus concluded that hybrid biocomposites with initial high strength might be a potential implant candidate for bone defect repair.