Biphasic Calcium Phosphate Particles Research Articles

In vitro characterization of an osteoinductive biphasic calcium phosphate in combination with recombinant BMP2

BackgroundThe repair of alveolar bone defects with growth factors and bone grafting materials has played a pivotal role in modern dentistry. Recombinant human bone morphogenetic protein-2 (rhBMP2), an osteoinductive growth factor capable of cell recruitment and differentiation towards the osteoblast lineage, has been utilized in combination with various biomaterials to further enhance new bone formation. Recently, a group of novel biphasic calcium phosphate (BCP) bone grafting materials have been demonstrated to possess osteoinductive properties by demonstrating signs of ectopic bone formation. The aim of the present study was to study the effects of rhBMP2 in combination with osteoinductive BCP bone grafts on osteoblast cell behaviour.MethodsMC3T3-E1 pre-osteoblasts were seeded on 1) control tissue culture plastic, 2) 10 mg of BCP alone, 3) 100 ng rhBMP2, and 4) 100 ng rhBMP2+ 10 mg of BCP and analyzed for cell recruitment via a Transwell chamber, proliferation via an MTS assay and differentiation as assessed by alkaline phosphatase (ALP) activity, alizarin red staining and real-time PCR for osteoblast differentiation markers including Runx2, collagen1, ALP, and osteocalcin (OCN).ResultsrhBMP2 was able to significantly upregulate cell recruitment whereas the addition of BCP as well as BCP alone had no additional ability to improve osteoblast recruitment. Both BCP and rhBMP2 were able to significantly increase cell proliferation at 3 and 5 days post seeding and cell number was further enhanced when rhBMP2 was combined with BCP. In addition, the combination of rhBMP2 with BCP significantly improved ALP activity at 7 and 14 days post seeding, alizarin red staining at 14 days, and mRNA levels of Runx2, ALP and osteocalcin when compared to cells seeded with rhBMP2 alone or BCP alone.ConclusionsThe results from the present study demonstrate that 1) the osteoinductive potential of BCP bone particles is equally as osteopromotive as rhBMP2 on in vitro osteoblast differentiation and 2) BCP particles in combination with rhBMP2 is able to further increase the osteopromotive differentiation of osteoblasts in vitro when compared to either rhBMP2 alone or BCP alone. Future animal testing is further required to investigate this combination approach on new bone formation.

Osteogenic gene array of osteoblasts cultured on a novel osteoinductive biphasic calcium phosphate bone grafting material.

Recently, novel biphasic calcium phosphate (BCP) scaffolds have emerged as a new class of bone grafts with osteoinductive potential demonstrating the ability to form ectopic bone in extra-skeletal sites. The aim of the present study was to perform an osteogenic gene array to target possible genes responsible for eliciting the changes in cell expression responsible for inducing osteoblast differentiation. Human MG63 osteoblast-like cells were seeded for 24h on tissue culture plastic or osteoinductive BCP particles and analyzed for upregulated genes using an osteogenesis super-array. Osteoblast-related genes including those transcribed during bone mineralization, bone metabolism, cell growth and differentiation, as well as gene products representing extracellular matrix molecules, transcription factors, and cell adhesion molecules were investigated. An upregulation of genes transcribing biglycan (1.7-fold), bone morphogenetic proteins 1, 2, 4, 6, and 7 (1.5-2.1-fold), various collagen isoforms including 1a1, 1a2, 2a1, and 5a1 (1.73-2.72-fold), colony stimulating factor 2 (2.59-fold), fibroblast growth factor receptor 2 (1.79-fold), fibronectin (2.56-fold), integrin alpha 1, 2, and 3 (1.82-2.24-fold), SOX9 (2.75-fold), transforming growth factor beta receptor 2 (1.72-fold), vitamin D (1.89-fold), and vascular endothelial growth factor A and B (2.00, 1.75-fold) were all significantly (p<0.05) increased on BCP particles when compared to control tissue culture plastic. In summary, a number of activated genes were involved in bone formation following osteoblast attachment to BCP particles. The involvement of key chondrogenic genes hints that bone grafts capable of spontaneously inducing ectopic bone formation may implicate endochondral ossification. Further investigations in the triggered pathways involved in the process of ectopic bone formation are necessary to understand the key inductive properties of these novel osteoinductive BCP particles. Novel osteoinductive BCP particles demonstrate a wide range of significant increases over several key molecules implicated in osteogenesis that may be implicated in their ability to form ectopic bone formation.

Evaluation of Different Combinations of Biphasic Calcium Phosphate and Growth Factors for Bone Formation in Calvarial Defects in a Rabbit Model

The aim of the present preclinical study was to investigate the capability of a new formulation of biphasic calcium phosphate (BCP) in achieving new bone formation either by itself or in combination with different concentrations of growth factors. Twenty-four 3-month-old male New Zealand white rabbits (weight range, 2.5 to 3.0 kg) that had been bred exclusively for biomedical research purposes and obtained from a licensed vendor were used. Four calvarial defects were created in each animal, for a total of 96 defects. Each defect received alloplastic BCP (Osteon III, Genoss) that was composed of 60% hydroxyapatite and 40% β-tricalcium phosphate) (porosity, ~80%; macropore size, 200 to 400 μm; crystallinity, 95%) combined with different concentrations of recombinant human platelet-derived growth factor BB (rhPDGF-BB), human recombinant basic fibroblast growth factor-2 (rhFGF-2), or recombinant human bone morphogenetic protein-2 (rhBMP-2). A custom-made polycarbonate tube was fixed to each defect site by applying slight pressure, and a mixture of bone graft and growth factor was implanted into the tubes. Data were collected 2, 4, and 8 weeks after creation of the defects to assess early and late healing. Various amounts of newly formed bone and remnant BCP particles formed inside of the tube throughout the study period. The BCP + 0.5 mg/mL rhBMP-2 group exhibited the most bone formation. At 8 weeks, more new bone formation was noted in the Osteon III + rhBMP-2 combined group than in other groups. The present study results indicate that BCP can be combined with different concentrations of rhBMP-2, rhFGF-2, and rhPDGF-BB to produce new bone formation within a polycarbonate tube in calvarial defects in a rabbit model.

Bone Regeneration Using Bone Morphogenetic Protein-2 and Biphasic Calcium Phosphate With and Without Collagen Membrane in Calvarial Standardized Defects: An In Vivo Microcomputed Tomographic Experiment in Rats.

The aim of this in vivo microcomputed tomographic (μCT) experiment was to assess in real time the efficacy of a combination of recombinant human bone morphogenetic protein-2 (rhBMP-2) and biphasic calcium phosphate (BCP), with and without resorbable collagen membrane (CM), in regeneration of standardized calvarial defects (SCDs) in rats. A total of 30 female Wistar albino rats (n = 10/group) with a mean age and weight of 7.5 months and 275 g, respectively, were used. With the rats under general anesthesia, the calvaria were exposed using full-thickness periosteal flaps and unilateral SCDs of 4.6 mm diameter were created on the left parietal bone. Defects were left untreated (control group) or randomly filled with either BCP soaked in rhBMP-2 and then covered with CM (BMP + BCP + CM group) or BCP soaked in rhBMP-2 alone (BMP + BCP group). In vivo μCT scans were done at baseline and 2, 4, 6, and 8 weeks. Newly formed bone (NFB) and remaining BCP particles were assessed for their volumes (NFBV, BCPV, respectively) and mineral densities (NFBMD, BCPMD, respectively). In vivo μCT results showed scanty amounts of new bone at the peripheries of the defect in the control group. In the other two groups, near complete defect closure was evident at 8 weeks. The mean NFBV after 8 weeks was 4.63 ± 0.96 mm(3), 11.82 ± 1.17 mm(3), and 13.85 ± 1.89 mm(3) for the control, BMP + BCP + CM, and BMP + BCP groups, respectively. After 8 weeks, the mean NFBMD was 0.38 ± 0.03 g/mm(3), 0.24 ± 0.07 g/mm(3), and 0.35 ± 0.03 g/mm(3) for the control, BMP + BCP + CM, and BMP + BCP groups, respectively. After 8 weeks, the mean BCPV and BCPMD values for the BMP + BCP + CM and BMP + BCP groups were 2.73 ± 0.65 mm(3), 0.33 ± 0.08 g/mm(3), 2.49 ± 0.71 mm(3), and 0.28 ± 0.03 g/mm(3), respectively. The present real-time in vivo μCT experiment demonstrated that BMP + BCP, either with or without CM, was effective in promoting bone regeneration within rat SCDs and enabled new bone formation starting as early as 2 weeks.

Custom-Made Computer-Aided-Design/Computer-Aided-Manufacturing Biphasic Calcium-Phosphate Scaffold for Augmentation of an Atrophic Mandibular Anterior Ridge.

This report documents the clinical, radiographic, and histologic outcome of a custom-made computer-aided-design/computer-aided-manufactured (CAD/CAM) scaffold used for the alveolar ridge augmentation of a severely atrophic anterior mandible. Computed tomographic (CT) images of an atrophic anterior mandible were acquired and modified into a 3-dimensional (3D) reconstruction model; this was transferred to a CAD program, where a custom-made scaffold was designed. CAM software generated a set of tool-paths for the manufacture of the scaffold on a computer-numerical-control milling machine into the exact shape of the 3D design. A custom-made scaffold was milled from a synthetic micromacroporous biphasic calcium phosphate (BCP) block. The scaffold closely matched the shape of the defect: this helped to reduce the time for the surgery and contributed to good healing. One year later, newly formed and well-integrated bone was clinically available, and two implants (AnyRidge, MegaGen, Gyeongbuk, South Korea) were placed. The histologic samples retrieved from the implant sites revealed compact mature bone undergoing remodelling, marrow spaces, and newly formed trabecular bone surrounded by residual BCP particles. This study demonstrates that custom-made scaffolds can be fabricated by combining CT scans and CAD/CAM techniques. Further studies on a larger sample of patients are needed to confirm these results.

Preparation and characterization of nano biphasic calcium phosphate/poly-L-lactide composite scaffold

Abstract Nano biphasic calcium phosphate (BCP) particles were synthesized using the sol-gel method. As-prepared BCP particles were combined with poly-L-lactide (PLLA) to fabricate nano-BCP/PLLA composite scaffold through a series of processing steps containing solvent self-diffusion, hot-pressing, and particulate leaching. The composite had a suitable porous structure for bone tissue engineering scaffold. In comparison, micro-BCP/PLLA scaffold was studied as well. Nano-BCP particles were distributed homogeneously in the PLLA matrix, and much more tiny crystallites exposed on the surface of the pore wall. Due to the finer inorganic particle distribution in the PLLA phase and the larger area of the bioactive phase exposed in the pore wall surface, nano-BCP/PLLA scaffold had enhanced compressive strength, good bioactivity, and superior cell viability. A nonstoichiometric apatite layer could be rapidly formed on the surface of nano- BCP/PLLA when soaked in simulated body fluid. The MG-63 cell viability of nano-BCP/PLLA scaffold is significantly higher than that of micro-BCP/PLLA scaffold. Therefore, nano-BCP/PLLA composite may be a suitable alternative for bone tissue engineering scaffold.

Surface modification of porous polycaprolactone/biphasic calcium phosphate scaffolds for bone regeneration in rat calvaria defect.

In this study, polycaprolactone scaffolds fabricated by a salt-leaching process were loaded with biphasic calcium phosphate successfully to improve the osteoconductivity in bone regeneration. The surface of polycaprolactone/biphasic calcium phosphate scaffolds was aminolyzed by 1,6-hexamethylenediamine to introduce amino groups onto the surface, which was verified qualitatively by ninhyrin staining. Collagen was further immobilized on the aminolyzed porous polycaprolactone via N-ethyl-N'-(3-dimethylaminopropy) carbodiimide hydrochloride/hydroxy-2,5-dioxopyrolidine-3-sulfonic acid sodium cross-linking. The pore size of polycaprolactone/biphasic calcium phosphate-collagen scaffolds was 200-300 µm, which was suitable for bone in-growth. The X-ray photoelectron spectroscopy confirmed the coupling of collagen immobilized on the surface of polycaprolactone/biphasic calcium phosphate. In vitro results demonstrated that the spreading and viability of MC3T3-E1 cells were remarkably improved in the polycaprolactone/biphasic calcium phosphate-collagen scaffolds. The in vivo study was carried out by implanting the porous polycaprolactone, polycaprolactone/biphasic calcium phosphate, and polycaprolactone/biphasic calcium phosphate-collagen to the skulls of rats. Although the addition of biphasic calcium phosphate particles in the polycaprolactone scaffolds does not have a strong effect on the new bone formation, the immobilization of collagen on the polycaprolactone/biphasic calcium phosphate scaffolds significantly improved the bone regeneration even though the implantation time was short, 6 weeks. The present results provide more evidence that functionalizing polycaprolactone with biphasic calcium phosphate and collagen may be a feasible way to improve the osteoconduction in bone regeneration.

Microcomputed Tomography and Histologic Analysis of a Maxillary Implant Retrieved 19 Months After Placement and Indirect Sinus Augmentation With Biphasic Calcium Phosphate: A Case Report

Introduction: Implant osseointegration in regenerated bone and the resorptive outcome of graft materials are major clinical concerns.Case Presentation: A 40‐year‐old female patient underwent an indirect maxillary sinus augmentation with biphasic calcium phosphate (BCP) in conjunction with implant placement. Because of implant fracture, the implant and adjacent tissues were excised with a trephine bur 19 months after placement. The biopsy with the implant in place was analyzed by microcomputed tomography (micro‐CT) and histology. Marginal bone loss of the implant was evident, particularly on the fractured side. The graft particles were predominantly integrated in bone. Resorption lacunae were observed in the marginal bone area, but were not observed on the surface of the graft particles. Graft particles without contact to bone were observed coronal to the most coronal level of bone‐to‐implant contact, presumably exfoliated after marginal bone resorption. Of the total peri‐implant volume, 20.5% was residual graft material and 62.5% was bone according to the micro‐CT analysis. The histomorphometry demonstrated 30.4% residual graft material and 46.8% bone of the total peri‐implant area. The percentage of bone‐to‐implant contact was 60.3% when counting the total vertical implant perimeter.Conclusions: The BCP particles were mostly embedded in new bone, and the implant was clinically and histologically osseointegrated. This case report suggests that BCP graft material may not resorb during inflammation, resulting in exfoliation from the grafted compartment.

Poly(trimethylene carbonate) and biphasic calcium phosphate composites for orbital floor reconstruction: a feasibility study in sheep

In the treatment of orbital floor fractures, bone is ideally regenerated. The materials currently used for orbital floor reconstruction do not lead to the regeneration of bone. Our objective was to render polymeric materials based on poly(trimethylene carbonate) (PTMC) osteoinductive, and to evaluate their suitability for use in orbital floor reconstruction. For this purpose, osteoinductive biphasic calcium phosphate (BCP) particles were introduced into a polymeric PTMC matrix. Composite sheets containing 50 wt% BCP particles were prepared. Also laminates with poly(D,L-lactide) (PDLLA) were prepared by compression moulding PDLLA films onto the composite sheets. After sterilisation by gamma irradiation, the sheets were used to reconstruct surgically-created orbital floor defects in sheep. The bone inducing potential of the different implants was assessed upon intramuscular implantation. The performance of the implants in orbital floor reconstruction was assessed by cone beam computed tomography (CBCT). Histological evaluation revealed that in the orbital and intramuscular implantations of BCP containing specimens, bone formation could be seen after 3 and 9 months. Analysis of the CBCT scans showed that the composite PTMC sheets and the laminated composite sheets performed well in orbital floor reconstruction. It is concluded that PTMC/BCP composites and PTMC/BCP composites laminated with PDLLA have osteoinductive properties and seem suitable for use in orbital floor reconstruction.

Synthesis of biphasic calcium phosphate powders by a simple hydrolysis process

An ideal bone grafting material should be compatible with physiological environment, provoke osseous tissue formation and adapt degradation behaviour to new bone tissue growth. Calcium phosphates, a main inorganic constituent of the human hard tissue, are by far the best substitute materials for bone reconstruction because of their excellent bioactivity, biocompatibility and osteoconductivity. In the regime of calcium phosphates, hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , HA) possesses high stability and chemical similarity to the bone minerals. However, its limited solubility, and hence limited dissolution rate, may cause mismatch between implant and newly born tissue. On the contrary, β-tricalcium phosphate (β-Ca 3 (PO 4 ) 2 , β-TCP) undergoes too fast dissolution to form bone bonding. In order to achieve an optimised degradation rate, HA/β-TCP biphasic calcium phosphate (BCP) provides a suitable pathway. The HA/β-TCP ratio in the BCP is critical for desired performance. Unfortunately, the ease of a controllable HA/ β-TCP ratio has not been realised. In this study, we report a simple method to synthesise BCP from a monocalcium phosphate monohydrate (Ca(H 2 PO 4 ) 2 ·H 2 O, MCPM) precursor. Phase identification, microstructural observations and elemental analysis of the as-synthesised BCP particles are conducted by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), environmental scanning electron microscopy (ESEM) and X-ray fluorescence (XRF).

Histological Evaluation of Degradable Guided Bone Regeneration Membranes Prepared from Poly(trimethylene carbonate) and Biphasic Calcium Phosphate Composites

SummaryIn oral and maxillofacial surgery, guided bone regeneration using barrier membranes is an important strategy to treat bone defects. The currently used barrier membranes have important disadvantages. Barrier membranes prepared from resorbable poly(trimethylene carbonate) (PTMC) performed as well as collagen barrier membranes. We hypothesized that composite membranes prepared from surface‐eroding PTMC and osteoinductive biphasic calcium phosphate (BCP) would enhance bone formation even further. Bicortical critical size defects in the mandibular angle of rats were covered on both sides with the membranes. After 2, 4, and 12 weeks the extent of bone formation in the defects and the soft tissue reaction towards the membranes was examined histologically. At 2 and 4 weeks, the formation of new bone was observed in defects covered with PTMC, PTMC‐BCP and Biogide collagen membranes. At 12 weeks, bone defects that were covered with PTMC membranes and control Biogide collagen membranes were fully filled with new formed bone. However, at this time point, defects covered with PTMC‐BCP composite membranes had not led to new bone in the defects. Instead a significant tissue reaction, likely to remaining BCP particles, was observed.

The In Vitro and In Vivo Effects of a Low-Molecular-Weight Fucoidan on the Osteogenic Capacity of Human Adipose-Derived Stromal Cells

Human adipose-derived stromal cells (hASCs) may hold potential for bone tissue engineering. Osteogenic differentiation of these cells is crucial to bone formation. Low-molecular-weight fucoidan (LMWF) is a sulfated polysaccharide that potentiates several growth factors, including pro-angiogenic growth factors. To investigate whether hASC preconditioning with LMWF promoted bone repair, we compared the effects of LMWF and low-molecular-weight heparin on hASC phenotype and osteogenic differentiation. LMWF did not modify the stem-cell phenotype of hASCs but enhanced their osteogenic differentiation (formation of calcium deposits, increased activity and expression of alkaline phosphatase, and increased expression of osteopontin and runt-related transcription factor 2). However, when hASCs were exposed to LMWF before their adhesion to biphasic calcium phosphate particles and implantation in a bone-growth mouse model, no bone formation was apparent after 5 or 8 weeks, probably due to cell death. In conclusion, LMWF may hold promise for enhancing the osteogenic differentiation of hASCs before their implantation. However, concomitant vascularization would be required to enhance bone formation.

Evaluation of a new experimental model to study bone healing after ridge expansion with simultaneous implant placement – a pilot study in minipigs

To evaluate the suitability of a minipig model for the study of bone healing and osseointegration of dental implants following bone splitting and expansion of narrow ridges. In four minipigs, the mandibular premolars and first molars were extracted together with removal of the buccal bone plate. Three months later, ridge splitting and expansion was performed with simultaneous placement of three titanium implants per quadrant. On one side of the mandible, the expanded bone gap between the implants was filled with an alloplastic biphasic calcium phosphate (BCP) material, while the gap on the other side was left unfilled. A barrier membrane was placed in half of the quadrants. After a healing period of 6weeks, the animals were sacrificed for histological evaluation. In all groups, no bone fractures occurred, no implants were lost, all 24 implants were osseointegrated, and the gap created by bone splitting was filled with new bone, irrespective of whether BCP or a barrier membrane was used. Slight exposure of five implants was observed, but did not lead to implant loss. The level of the most coronal bone-to-implant contact varied without being dependent on the use of BCP or a barrier membrane. In all groups, the BCP particles were not present deep in the bone-filled gap. However, BCP particles were seen at the crestal bone margin, where they were partly integrated in the new bone. This new minipig model holds great promise for studying experimental ridge splitting/expansion. However, efforts must be undertaken to reduce implant exposure and buccal bone resorption.

A Prospective, Randomized Controlled Preclinical Trial to Evaluate Different Formulations of Biphasic Calcium Phosphate in Combination With a Hydroxyapatite Collagen Membrane to Reconstruct Deficient Alveolar Ridges

Many patients and clinicians would prefer a synthetic particulate bone replacement graft, but most available alloplastic biomaterials have limited osteogenic potential. An alloplast with increased regenerative capacity would be advantageous for the treatment of localized alveolar ridge defects. This prospective, randomized controlled preclinical trial utilized 6 female foxhounds to analyze the osteogenic impact of different formulations of biphasic calcium phosphate (BCP) in combination with an hydroxyapatite-collagen membrane and their ability to reconstruct deficient alveolar ridges for future implant placement. The grafted sites were allowed to heal 3 months, and then trephine biopsies were obtained to perform light microscopic and histomorphometric analyses. All treated sites healed well with no early membrane exposure or adverse soft tissue responses during the healing period. The grafted sites exhibited greater radiopacity than the surrounding native bone with BCP particles seen as radiopaque granules. The graft particles appeared to be well-integrated and no areas of loose particles were observed. Histologic evaluation demonstrated BCP particles embedded in woven bone with dense connective tissue/marrow space. New bone growth was observed around the graft particles as well as within the structure of the graft particulate. There was intimate contact between the graft particles and newly formed bone, and graft particles were bridged by the newly formed bone in all biopsies from the tested groups. The present study results support the potential of these BCP graft particulates to stimulate new bone formation. Clinical studies are recommended to confirm these preclinical findings.

A Comparison of Three Calcium Phosphate–Based Space Fillers in Sinus Elevation: A Study in Rabbits

Subsinus bone regeneration procedures are reliable and known to be effective with the use of biomaterials alone. Nevertheless, many types of biomaterials are available, and the efficacy of each in terms of bone formation and resorption rate has rarely been compared. This study aimed to compare bone formation, resorption rate, osteoconductivity, and three-dimensional volume changes of three biomaterials often used for alveolar ridge augmentation. Rabbits underwent bilateral sinus elevation using three different types of space fillers: bovine hydroxyapatite (BHA), beta-tricalcium phosphate (β-TCP), or biphasic calcium phosphate (BCP). Animals were sacrificed at 1 week, 5 weeks, and 6 months. Samples were subjected to microcomputed tomography and histologic examination. Qualitative analysis was performed on nondecalcified sections, and quantitative histomorphometric analysis was conducted using scanning electron microscopy. Volume differences in augmented bone were calculated at different time points. All three particulated biomaterials promoted osteogenesis in this particular animal model. At 6 months, biomaterial resorption rates were significantly different across the three groups. The highest resorption rate was found with β-TCP, in which only 6.7% of the baseline particle surface remained. At 6 months, bone was in close contact with the BHA particles, constituting a composite network; in contrast, BCP particles were often surrounded by soft tissue. Within each group, no significant differences in volume were found at the different time points. Despite the limitations of the study, the three studied biomaterials proved to be effective in promoting osteogenesis. High resorption rates and complete replacement of the biomaterials by bone seemed to withstand intrasinusal pressure. Further investigations in humans should consider longer follow-up periods.

Composite Bioceramics/Polymer Electrospun Scaffolds for Regenerative Medicine

The main goal of this study was to succeed in the relevant association of well-known osteoconductive biphasic calcium phosphate (BCP) made of Hydroxyapatite (20% HA) and β-Tricalcium Phosphate (80% β-TCP) crystallographic phases and resorbable poly (L-lactide-co-D,L-lactide)(PLDLLA) 3D matrices synthesized by electrospinning. Two types of mineral particles were obtained, BCP new hollow granules, and classical BCP particles. It appeared that hollow shells/PLDLLA composite 3D matrices allowed higher cell adhesion in vitro, thanks to internal concavities and are promising scaffolds in terms of cell carrying.

Porous Magnesium-Doped Biphasic Calcium Phosphate Ceramics Prepared via Polymeric Sponge Method

Porous magnesium-doped biphasic calcium phosphate (Mg-BCP) scaffolds were prepared through polymeric sponge method by employing sol-gel derived Mg-BCP powders of 5 and 10 mol% Mg concentrations doped. Magnesium-free porous biphasic calcium phosphate (BCP) was also prepared as the reference. Morphological analysis showed that the doping of magnesium caused accelerated crystal growth of BCP particles leading to more progressive particle fusion and densification. All porous samples showed good pore interconnectivity with the macropores of 100–1,000 µ m in average size. Magnesium free porous BCP has 0.39 MPa compressive strength, and it increased with the doped Mg level to 2.17 MPa at 10 mol% Mg doping. This was attributed to the increased density from 1.98 g/cm3 (Mg free porous BCP) to 2.19 g/cm3 (10 mol% porous Mg-BCP) thus reflecting denser porous structure as the consequence of more progressive densification. It can be concluded that magnesium acted as the sintering additive of the fabricated porous calcium phosphates leading to improved mechanical properties.

Effect of strontium-substituted biphasic calcium phosphate on inflammatory mediators production by human monocytes

Calcium phosphate materials are widely used as bone substitutes because of their properties close to those of the mineral phase of bones. Nevertheless, after several months, calcium phosphate-based materials release particles that may be phagocytosed by monocytes, leading to an inflammatory reaction. Strontium is well known to counteract the osteoporosis process, but little is known about its effect on inflammatory processes. The purpose of this work was to study the effect of biphasic calcium phosphate (BCP) particles substituted with strontium on the inflammatory reaction. Human primary monocytes stimulated or not by lipopolysaccharide (LPS) were exposed to BCP particles containing strontium for 6 and 24h. Inflammatory mediators (cytokines and matrix metalloproteinases (MMPs)) production was then quantified by ELISA and zymography. We observed that the presence of strontium had few effects on unstimulated cells, but it decreased the production of pro-inflammatory cytokines and the chemokine interleukin 8 in LPS-stimulated cell-conditioned medium. This work suggests for the first time that strontium may be involved in the control of inflammatory processes following BCP phagocytosis by human monocytes.

The osteoinductive potential of printable, cell‐laden hydrogel‐ceramic composites

Hydrogels used as injectables or in organ printing often lack the appropriate stimuli to direct osteogenic differentiation of embedded multipotent stromal cells (MSCs), resulting in limited bone formation in these matrices. Addition of calcium phosphate (CaP) particles to the printing mixture is hypothesized to overcome this drawback. In this study we have investigated the effect of CaP particles on the osteoinductive potential of cell-laden hydrogel-CaP composite matrices. To this end, apatitic nanoparticles have been included in Matrigel constructs where after the viability of embedded progenitor cells was assessed in vitro. In addition, the osteoinductive potential of cell-laden Matrigel containing apatitic nanoparticles was investigated in vivo and compared with composites containing osteoinductive biphasic calcium phosphate (BCP) microparticles after subcutaneous implantation in immunodeficient mice. Histological and immunohistochemical analysis of the tissue response as well as in vivo bone formation revealed that apatitic nanoparticles were osteoinductive and induced osteoclast activation, but without bone formation. The BCP particles were more effective in inducing elaborate bone formation at the ectopic location.

Inkjet printed antibiotic- and calcium-eluting bioresorbable nanocomposite micropatterns for orthopedic implants

Inkjet printing of antibiotic- and calcium-eluting micropatterns was explored as a novel means of preventing the formation of biofilm colonies and facilitating osteogenic cell development on orthopedic implant surfaces. The micropatterns consisted of a periodic array of ∼50μm circular dots separated by ∼150μm. The composition of the micropatterns was controlled by formulating inks with rifampicin (RFP) and poly(d,l-lactic–co-glycolic) acid (PLGA) dissolved in an organic solvent with ∼100nm biphasic calcium phosphate (BCP) nanoparticles suspended in the solution. During printing RFP and PLGA co-precipitated to form a nanocomposite structure with ∼10–100nm RFP and the BCP particles dispersed in the PLGA matrix. The rate of RFP release was strongly influenced by the RFP loading in the micropattern, particularly on the first day. The RFP-containing micropatterns effectively prevented the formation of Staphylococcus epidermidis biofilm colonies due to their ability to kill bacteria prior to forming colonies on the patterned surfaces. The BCP-containing micropatterns printed on the surface of the alloy TiAl6V4 significantly accelerated osteoblast cell differentiation, as measured by alkaline phosphatase expression and calcium deposition, without compromising cell proliferation.