Carrier For Bone Morphogenetic Protein-2 Research Articles

Enhanced Skull Bone Regeneration by Sustained Release of BMP-2 in Interpenetrating Composite Hydrogels.

Direct administration of bone morphogenetic protein-2 (BMP-2) for bone regeneration could cause various clinical side effects such as osteoclast activation, inflammation, adipogenesis, and bone cyst formation. In this study, thiolated gelatin/poly(ethylene glycol) diacrylate (PEGDA) interpenetrating (IPN) composite hydrogels were developed for guided skull bone regeneration. To promote bone regeneration, either polycation-based coacervates (Coa) or gelatin microparticles (GMPs) were incorporated within IPN gels as BMP-2 carriers. Both BMP-2 loaded Coa and BMP-2 loaded GMPs showed significantly enhanced in vitro alkaline phosphate (ALP) activity of human mesenchymal stem cells (hMSCs) than non-BMP-2 treated control. Moreover, BMP-2 loaded GMPs group exhibited statistically increased ALP activity compared to both bolus BMP-2 administration and BMP-2 loaded Coa group, indicating that our carriers could protect and maintain biological activity of cargo BMP-2. Sustained release kinetics of BMP-2 from IPN composite hydrogels could be controlled by different formulations. For in vivo bone regeneration, various IPN gel formulations (i.e., (1) control, (2) only hydrogel, (3) hydrogel with bolus BMP-2, (4) hydrogel with BMP-2-loaded Coa, and (5) hydrogel with BMP-2-loaded GMPs) were bilaterally implanted into 5 mm-sized rat calvarial defects. After 4 weeks, micro-CT and histological analysis were performed to evaluate new bone formation. Significantly higher scores for bony bridging and union were observed in BMP-2-loaded Coa and BMP-2-loaded GMP groups as compared to other formulations. In addition, rats treated with BMP-2-loaded GMPs showed a significantly higher ratio of bone volume/total volume and lower trabecular separation scores than others. Finally, rats treated with either Coa or GMP groups exhibited a significant increase in bone formation area, as assessed via histomorphometric analysis. Taken together, it could be concluded that Coa and GMPs were effective carriers to maintain the bioactivity of cargo BMP-2 during its sustained release. Consequently, our IPN composite hydrogel system that combines such BMP-2 carriers could effectively promote skull bone regeneration.

Novel In Situ Gelling Hydrogels Loaded with Recombinant Collagen Peptide Microspheres as a Slow-Release System Induce Ectopic Bone Formation.

New solutions for large bone defect repair are needed. Here, in situ gelling slow release systems for bone induction are assessed. Collagen-I based Recombinant Peptide (RCP) microspheres (MSs) are produced and used as a carrier for bone morphogenetic protein 2 (BMP-2). The RCP-MSs are dispersed in three hydrogels: high mannuronate (SLM) alginate, high guluronate (SLG) alginate, and thermoresponsive hyaluronan derivative (HApN). HApN+RCP-MS forms a gel structure at 32 ºC or above, while SLM+RCP-MS and SLG+RCP-MS respond to shear stress displaying thixotropic behavior. Alginate formulations show sustained release of BMP-2, while there is minimal release from HApN. These formulations are injected subcutaneously in rats. SLM+RCP-MS and SLG+RCP-MS loaded with BMP-2 induce ectopic bone formation as revealed by X-ray tomography and histology, whereas HApN+RCP-MS do not. Vascularization occurs within all the formulations studied and is significantly higher in SLG+MS and HApN+RCP-MS than in SLM+RCP-MS. Inflammation (based on macrophage subset staining) decreases over time in both alginate groups, but increases in the HApN+RCP-MS condition. It is shown that a balance between inflammatory cell infiltration, BMP-2 release, and vascularization, achieved in the SLG+RCP-MS alginate condition, is optimal for the induction of de novo bone formation.

Bone morphogenetic protein-2 release profile modulates bone formation in phosphorylated hydrogel.

The optimal release profile of locally delivered bone morphogenetic protein-2 (BMP-2) for safe and effective clinical application is unknown. In this work, the effect of differential BMP-2 release on bone formation was investigated using a novel biomaterial oligo[(polyethylene glycol) fumarate] bis[2-(methacryloyloxy) ethyl] phosphate hydrogel (OPF-BP) containing poly(lactic-co-glycolic acid) microspheres. Three composite implants with the same biomaterial chemistry and structure but different BMP-loading methods were created: BMP-2 encapsulated in microspheres (OPF-BP-Msp), BMP-2 encapsulated in microspheres and adsorbed on the phosphorylated hydrogel (OPF-BP-Cmb), and BMP-2 adsorbed on the phosphorylated hydrogel (OPF-BP-Ads). These composites were compared with the clinically used BMP-2 carrier, Infuse® absorbable collagen sponge (ACS). Differential release profiles of bioactive BMP-2 were achieved by these composites. In a rat subcutaneous implantation model, OPF-BP-Ads and ACS generated a large BMP-2 burst release (>75%), whereas a more sustained release was seen for OPF-BP-Msp and OPF-BP-Cmb (~25% and 50% burst, respectively). OPF-BP-Ads generated significantly more bone than did all other composites, and the bone formation was 12-fold higher than that of the clinically used ACS. Overall, this study clearly shows that BMP-2 burst release generates more subcutaneous bone than do sustained release in OPF-BP-microsphere composites. Furthermore, composites should not only function as a delivery vehicle but also provide a proper framework to achieve appropriate bone formation.

Application of alginate microbeads as a carrier of bone morphogenetic protein-2 for bone regeneration.

Bone morphogenetic protein-2 (BMP-2) is commonly used to enhance bone regeneration. The potential of BMP-2 for bone regeneration varies according to the concentration and release kinetics on the implanted site. Therefore, it is important to determine appropriate carriers of BMP-2. However, no optimal delivery vehicles have been identified. In the present study, we used alginate microbeads as a delivery vehicle for BMP-2. Alginate microbeads can be implanted onto the disease site through surgery or injection. The objective of this study was to evaluate that the osteoinductive properties of BMP-2 are effective in alginate microbeads as a carrier. In this study, the release kinetics of BMP-2 in alginate microbeads was evaluated using an enzyme-linked immunosorbent assay. BMP-2 released from alginate microbeads induced high alkaline phosphatase activity in canine adipose tissue-derived mesenchymal stem cells. Injection of alginate microbeads with BMP-2 into mouse subcutaneous tissue, as well as surgical implantation into the 5-mm circular calvarial defects in rats, was conducted and the results showed extensive new bone formation. In conclusion, alginate microbeads can be utilized as an effective BMP-2 delivery vehicle for use in orthopedic surgery and as an injectable vehicle for a minimally invasive therapy. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 286-294, 2019.

* Demineralized Bone Matrix as a Carrier for Bone Morphogenetic Protein-2: Burst Release Combined with Long-Term Binding and Osteoinductive Activity Evaluated In Vitro and In Vivo.

To allow bone defect regeneration, autologous bone grafting still represents the gold standard. However, autograft harvesting has limitations, including an additional surgery, donor site morbidity, and limited availability. Demineralized bone matrix (DBM) would represent an alternative, yet lacks sufficient osteoinductive properties. Combining DBM with a potent agent, such as bone morphogenetic protein-2 (BMP-2) might be a feasible alternative approach, optimizing an established grafting material with strong osteoinductive properties. A unique mixing device has been developed that enables perioperative handling to reach a homogeneous and standardized paste for bone defect filling. DBM proved in vitro to be a suitable carrier for BMP-2, with a documented release over 56 days at concentrations sufficient to stimulate osteogenic differentiation. At the end of the elution experiment, 56 days, bioactive BMP was still captured within the DBM. Using a sheep drill hole defect model, DBM perioperatively mixed with BMP-2 showed strong osteoinductive properties comparable to those of autologous bone and outnumbering the one of DBM alone or empty defects. Bone defect healing was enabled at diaphyseal and metaphyseal defects and thus BMP-2-doped DBM represented an easy perioperative enriching method and an efficient carrier for BMP-2. With the comparability to the clinical gold standard autologous bone, DBM mixed with BMP-2 might serve as possible alternative grafting material enabling a controlled osteogenic stimulation.

Stepwise verification of bone regeneration using recombinant human bone morphogenetic protein-2 in rat fibula model.

ObjectivesThe purpose of this study was to introduce our three experiments on bone morphogenetic protein (BMP) and its carriers performed using the critical sized segmental defect (CSD) model in rat fibula and to investigate development of animal models and carriers for more effective bone regeneration.Materials and MethodsFor the experiments, 14, 16, and 24 rats with CSDs on both fibulae were used in Experiments 1, 2, and 3, respectively. BMP-2 with absorbable collagen sponge (ACS) (Experiments 1 and 2), autoclaved autogenous bone (AAB) and fibrin glue (FG) (Experiment 3), and xenogenic bone (Experiment 2) were used in the experimental groups. Radiographic and histomorphological evaluations were performed during the follow-up period of each experiment.ResultsSignificant new bone formation was commonly observed in all experimental groups using BMP-2 compared to control and xenograft (porcine bone) groups. Although there was some difference based on BMP carrier, regenerated bone volume was typically reduced by remodeling after initially forming excessive bone.ConclusionBMP-2 demonstrates excellent ability for bone regeneration because of its osteoinductivity, but efficacy can be significantly different depending on its delivery system. ACS and FG showed relatively good bone regeneration capacity, satisfying the essential conditions of localization and release-control when used as BMP carriers. AAB could not provide release-control as a BMP carrier, but its space-maintenance role was remarkable. Carriers and scaffolds that can provide sufficient support to the BMP/carrier complex are necessary for large bone defects, and AAB is thought to be able to act as an effective scaffold. The CSD model of rat fibula is simple and useful for initial estimate of bone regeneration by agents including BMPs.

Treatment of critically sized femoral defects with recombinant BMP-2 delivered by a modified mPEG-PLGA biodegradable thermosensitive hydrogel.

BackgroundReconstruction of a segmental fracture with massive bone loss is still a challenge for orthopaedic surgeons. The aim of our study was to develop a suitable biodegradable thermosensitive hydrogel system as a carrier for bone morphogenetic protein (BMP)-2 delivery in the treatment of critical-sized femoral defects.MethodsA block copolymer composed of monomethoxypoly(ethylene glycol) (mPEG), poly(lactic-co-glycolic acid) (PLGA) and 2, 2’-Bis (2-oxazolin) (Box) was synthesized by ring opening polymerization. The synthesized block copolymer was characterized by 1H-NMR spectroscopy and gel permeation chromatography (GPC). Different biophysical and biochemical properties of the synthesized copolymer, including temperature-induced structure changes, degradation rate, pH changes during hydrolytic degradation, cell toxicity, and the release profile of BMP-2, were also evaluated and/or were compared with those of a well-characterized mPEG-PLGA copolymer. In animal testing, rabbits (n = 36) that received critically sized (10 mm) femoral defects were divided into 6 groups. These experimental groups included an untreated group, autograft, and groups treated with the synthesized copolymer carrying different concentrations of BMP-2 (0, 5, 10, and 20 μg/ml). Bone repair was evaluated using X-ray radiography, histological staining, micro-computed tomography (μCT), biomarker examination and biomechanical testing in a 12-week treatment period.ResultsA new thermosensitive mPEG-PLGA/Box/mPEG-PLGA block copolymer, or named as BOX copolymer, was successfully prepared. Compared to the reported mPEG-PLGA in vitro, the prepared BOX copolymer at the same weight percent concentrations exhibited wider temperature ranges of gelation, slower degradation rates, higher the pH values, as well as less cytotoxicity. Furthermore, the BMP-2 release from BOX hydrogel exhibited a near-linear release profile in vitro. In animal experiments, treatment of critical-sized bony defects with 25 wt% BOX hydrogel carrying BMP-2 effectively promoted fracture healing during the 12-week trial period and higher concentrations of BMP-2 treatment correlated with better bone quality. Most importantly, clinical outcome and bone healing in the BOX-hydrogel group with 20 μg/ml BMP-2 were nearly equivalent to those in the autograft group in a 12-week treatment course.ConclusionThese data support that the use of BOX hydrogel (25 wt%) as a drug delivery system is a promising method in the treatment of large bone defects.

Accelerated bony defect healing by chitosan/silica hybrid membrane with localized bone morphogenetic protein-2 delivery

Therapeutic agents such as growth factors have been widely applied to promote bone regeneration with implantable biomaterials. In this study, a hybrid of chitosan–xerogel membrane was combined with bone morphogenetic protein-2 (BMP-2) for enhancing bone regeneration. The characteristics of the hybrid membrane as a carrier of BMP-2 were compared with that of the pure chitosan membrane, and the effect of combining the hybrid membrane with BMP-2 on its bone healing ability was evaluated using in vitro and in vivo animal tests. The amount of BMP-2 adsorbed on the pure chitosan membrane was less than that on the hybrid membrane and, therefore, the cellular behaviors of the pure chitosan membrane were only slightly improved by the protein treatment. In contrast, the hybrid membrane showed excellent affinity toward BMP-2, and the adsorption of BMP-2 elicited a dramatic improvement in the cellular responses of the hybrid membrane. Moreover, the in vivo study demonstrated that bone regeneration was significantly enhanced when using the hybrid membrane with BMP-2 as compared to the hybrid membrane without BMP-2. These results suggest that the hybrid membrane is very efficient in carrying BMP-2 and accelerates the bone healing process through the successful delivery of BMP-2 and its osteoconductive composition.

Use of salicylic acid polymers and bone morphogenetic protein-2 to promote bone regeneration in rabbit parietal bone defects

The ability of bone defects to heal spontaneously is inversely related to the size of the defect, such that defects larger than a critical size will not heal without additional therapeutic intervention. Typically, large bone defects are filled with autologous bone harvested from another skeletal site, an osteoconductive bone graft material, treated with an osteoinductive factor such as bone morphogenetic protein-2, or by a combination of these approaches. Despite these interventions, unsatisfactory success and complication rates show that alternative treatment methods are needed. Here, we test whether salicylic acid polymers can be used as guided bone regeneration barriers in conjunction with bone morphogenetic protein-2 to treat 1-cm-diameter defects in rabbit parietal bones. Porous, 1-cm round polycaprolactone scaffolds were infused with calcium sulfate–containing bone morphogenetic protein-2 and then capped on one side with salicylic acid polymers. The polymers slowed resorption of calcium sulfate that was used as a carrier for bone morphogenetic protein-2, indicating that bone morphogenetic protein-2 release into the parietal bone defect was extended by the use of the salicylic acid polymer. Microcomputerized tomography and histomorphometric analysis of the parietal bones 8 weeks after implantation showed that the salicylic acid polymer did not impair bone formation in the defect. These observations indicate that salicylic polymers paired with bone morphogenetic protein-2 can be optimized for use in guided bone regeneration to help repair large bone defects.

Comparative study of recombinant human bone morphogenetic protein-2 carriers in rat subcutaneous tissues: Pilot study

The purpose of this study was to evaluate and compare the potential of using various biomaterials as a carrier of rhBMP-2 in the subcutaneous layer of rats. 5 subcutaneous defects were made in each of the dorsal surfaces of 10 rats. Then, the rats were divided into the following groups: Control group: sham-surgery control, Experimental group 1: rhBMP-2/Bio-Oss®, Experimental group 2: rhBMP-2/Collatape®, Experimental group 3: rhBMP-2/nCS. Histological and histometrical analysis were performed after the rats were sacrificed at 2 and 4 weeks. Regardless of the type of carrier, the groups treated with rhBMP-2 showed significantly greater bone formation when compared to the control group. The amount of new bone formation was greater at 4 week than 2 week. Total bone formation (%) at 4 week was the greatest in rhBMP/Bio-Oss® (26.76±10.13) group, followed by rhBMP/Collatape® (20.38±5.27) and rhBMP/nCS (4.34±2.58). Within the limitation of this study, the results showed that Bio-Oss®, Collatape®, nanocalcium sulfate all showed new bone formation when used as a carrier of rhBMP-2 in the subcutaneous layer of rats, indicating potential use as carriers for rhBMP-2.

Immobilization effect of bone morphogenetic protein-2 on collagen membrane via photoreactive gelatin derivatives: Biocompatibility and preservability of osteoinductive activity

To photo-immobilize bone morphogenetic protein-2 (BMP-2), UV light-reactive gelatin (azidophenyl gelatin, Az-gel), which is introduced with an N-(4-azidobenzoyloxy) succinimide-containing an azide group, was prepared as a carrier of BMP-2. Characterization of the photo-reactivity of Az-gel was evaluated by the curing ratio and it was micropatterned using a photomask. The cross-linking ratio and an enzyme-linked immunosorbent assay, enzymelinked immunospecific assay (ELISA)-based BMP-2-release test were used to determine the optimal density of Azgel (1, 3, and 5%) and UV treatment time (10, 30, 60 s) of the BMP-2 carrier in collagen matrix. The results showed that 5% Az-gel with 60 s of UV treatment was the most efficient condition for cross-linking. Cytotoxicity assays using the C2C12 mouse myoblast cell line showed that there were no cytotoxic effects of Az-gel. Alkaline phosphatase activity and calcium ion detection assays to evaluate the osteoinductive activities were conducted in assumed optimal condition of Az-gel (5% and 60 s UV treatment) 14 days post-treatment. In our study, the osteoinductive activities were the highest in cells treated with BMP-2 and the photo-reactive Az-gel carrier compared to BMP-2 alone or untreated control cells in collagen matrix at all time points (3, 7, and 14 days).

A glass polyalkenoate cement carrier for bone morphogenetic proteins.

This work considers a glass polyalkenoate cement (GPC)-based carrier for the effective delivery of bone morphogenetic proteins (BMPs) at an implantation site. A 0.12 CaO-0.04 SrO-0.36 ZnO-0.48 SiO2 based glass and poly(acrylic acid) (PAA, Mw 213,000) were employed for the fabrication of the GPC. The media used for the water source in the GPC reaction was altered to produce a series of GPCs. The GPC liquid media was either 100 % distilled water with additions of albumin at 0, 2, 5 and 8 wt% of the glass content, 100 % formulation buffer (IFB), and 100 % BMP (150 µg rhBMP-2/ml IFB). Rheological properties, compressive strength, ion release profiles and BMP release were evaluated. Working times (Tw) of the formulated GPCs significantly increased with the addition of 2 % albumin and remained constant with further increases in albumin content or IFB solutions. Setting time (Ts) experienced an increase with 2 and 5 % albumin content, but a decrease with 8 % albumin. Changing the liquid source to IFB containing 5 % albumin had no significant effect on Ts compared to the 8 % albumin-containing BT101. Replacing the albumin with IFB/BMP-2 did not significantly affect Tw. However, Ts increased for the BT101_BMP-2 containing GPCs, compared to all other samples. The compressive strength evaluated 1 day post cement mixing was not affected significantly by the incorporation of BMPs, but the ion release did increase from the cements, particularly for Zn and Sr. The GPCs released BMP after the first day, which decreased in content during the following 6 days. This study has proven that BMPs can be immobilized into GPCs and may result in novel materials for clinical applications.

Bone Morphogenetic Proteins: Promising Molecules for Bone Healing, Bioengineering, and Regenerative Medicine.

Bone morphogenetic proteins (BMPs), glycoproteins secreted by some cells, are members of the TGF-β superfamily that have been implicated in a wide variety of roles. Currently, about 20 different BMPs have been identified and grouped into subfamilies, according to similarities with respect to their amino acid sequences. It has been shown that BMPs are secreted growth factors involved in mesenchymal stem cell differentiation, also being reported to control the differentiation of cancer stem cells. BMPs initiate signaling from the cell surface by binding to two different receptors (R: Type I and II). The heterodimeric formation of type I R and II R may occur before or after BMP binding, inducing signal transduction pathways through SMADs. BMPs may also signal through SMAD-independent pathways via mitogen-activated protein kinases (ERK, p38MAPKs, JNK). BMPs may act in an autocrine or paracrine manner, being regulated by specific antagonists, namely: noggin and chordin. Genetic engineering allows the production of large amounts of BMPs for clinical use, and clinical trials have shown the benefits of FDA-approved recombinant human BMPs 2 and 7. Several materials from synthetic to natural sources have been tested as BMP carriers, ranging from hydroxyapatite, and organic polymers to collagen. Bioactive membranes doped with BMPs are promising options, acting to accelerate and enhance osteointegration. The development of smart materials, mainly based on biopolymers and bone-like calcium phosphates, appears to provide an attractive alternative for delivering BMPs in an adequately controlled fashion. BMPs have revealed a promising future for the fields of Bioengineering and Regenerative Medicine. In this chapter, we review and discuss the data on BMP structure, mechanisms of action, and possible clinical applications.

Fibronectin and Craniofacial Surgery

Fibronectin is an essential component of the extracellular matrix. The role of fibronectin in craniofacial surgery has not been previously reviewed. Fibronectin mediates bone differentiation and development of the skull. Studies have shown that normal development of the skull requires a specific pattern of expression around the epithelial-mesenchymal interface of the neurocranium. Fibronectin is also essential in mediating the migration of neural crest cells to form the facial skeleton. The calvaria of patients with Apert and Crouzon syndromes have an abnormally elevated collagen level. However, fibronectin levels are elevated in the former syndrome and decreased in the latter syndrome. The significance of this requires further research. Fibronectin gene expression is increased in port wine-derived fibroblasts in patients with Sturge-Weber syndrome. Normal palatogenesis also requires a specific pattern of expression of fibronectin around the maxillary process as well as the roof of the stomodeum, and several studies have linked the development of cleft lip/palate to an imbalance of fibronectin content of the extracellular matrix. Fibronectin mediates cell-to-cell attachment during repair of calvarial defects; hence, fibronectin has been used as a carrier for bone morphogenetic proteins to treat calvarial defects. Finally, fibronectin is now an essential component in stem cell technology related to craniofacial surgery.

The effects of 3D bioactive glass scaffolds and BMP-2 on bone formation in rat femoral critical size defects and adjacent bones

Reconstruction of critical size defects in the load-bearing area has long been a challenge in orthopaedics. In the past, we have demonstrated the feasibility of using a biodegradable load-sharing scaffold fabricated from poly(propylene fumarate)/tricalcium phosphate (PPF/TCP) loaded with bone morphogenetic protein-2 (BMP-2) to successfully induce healing in those defects. However, there is limited osteoconduction observed with the PPF/TCP scaffold itself. For this reason, 13-93 bioactive glass scaffolds with local BMP-2 delivery were investigated in this study for inducing segmental defect repairs in a load-bearing region. Furthermore, a recent review on BMP-2 revealed greater risks in radiculitis, ectopic bone formation, osteolysis and poor global outcome in association with the use of BMP-2 for spinal fusion. We also evaluated the potential side effects of locally delivered BMP-2 on the structures of adjacent bones. Therefore, cylindrical 13-93 glass scaffolds were fabricated by indirect selective laser sintering with side holes on the cylinder filled with dicalcium phosphate dehydrate as a BMP-2 carrier. The scaffolds were implanted into critical size defects created in rat femurs with and without 10 μg of BMP-2. The x-ray and micro-CT results showed that a bridging callus was found as soon as three weeks and progressed gradually in the BMP group while minimal bone formation was observed in the control group. Degradation of the scaffolds was noted in both groups. Stiffness, peak load and energy to break of the BMP group were all higher than the control group. There was no statistical difference in bone mineral density, bone area and bone mineral content in the tibiae and contralateral femurs of the control and BMP groups. In conclusion, a 13-93 bioactive glass scaffold with local BMP-2 delivery has been demonstrated for its potential application in treating large bone defects.

Bone morphogenetic protein-2 for bone regeneration – Dose reduction through graphene oxide-based delivery

High doses of bone morphogenetic protein-2 (BMP-2) are required for effective bone regeneration. However, these high doses often cause undesirable adverse effects, including bone overgrowth, osteolysis, and activation of the immune response, and raise treatment costs. In an effort to reduce the BMP-2 dose to avoid or diminish side effects, we investigated whether delivery of BMP-2 using graphene oxide (GO) can reduce the BMP-2 dose for bone regeneration. Delivery of BMP-2 using GO flakes suspended in fibrin gels (GO/F) resulted in significantly greater osteogenic differentiation of human bone marrow-derived mesenchymal stem cells in vitro, and at various doses of BMP-2, significantly greater amounts of bone regeneration in mouse calvarial defects occurred than when fibrin gel (F) alone was used. A half-dose of BMP-2 delivered by GO/F resulted in bone regeneration similar to that resulting from a full dose of BMP-2 delivered by F. The enhanced bone regeneration efficacy was likely due, at least in part, to the sustained release, higher structural stability, and higher bioactivity of BMP-2 delivered by GO/F compared to BMP-2 delivered by F. Therefore, GO may be an effective carrier for BMP-2 to reduce the BMP-2 dose and avoid adverse effects.

Acceleration of Bone Regeneration byBMP‐2‐Loaded Collagenated Biphasic Calcium Phosphate in Rabbit Sinus

The objective of this study was to determine the effectiveness of collagenated biphasic calcium phosphate (CBCP) as a carrier for bone morphogenetic protein-2 (BMP-2) at the early stage of healing in rabbit sinus. In 16 rabbits, BMP-2-loaded CBCP was grafted into one sinus (the BMP group) and saline-soaked CBCP was grafted into another sinus (the CTL group). The groups were assigned randomly. After 2 weeks (n = 8) or 4 weeks (n = 8), radiographic and histological analysis was performed. Total augmented volume was significantly larger in the BMP group at both healing periods. Furthermore, new bone volume was significantly greater in the BMP group at 4 weeks. Marked bone formation near the schneiderian membrane was found in the BMP groups at the early healing period. At 4 weeks, evenly distributed new bone was observed in the BMP group, whereas the new bone was sparsely distributed in the central portion in the CTL group. It can be concluded that the addition of BMP-2 to CBCP resulted in a greater initial augmented volume as a result of postoperative swelling, which is replaced by early bone formation, and it was prominent near the Schneiderian membrane.

Facile synthesis, microstructure and BMP-2 delivery of novel silica hollow flowers for enhanced osteoblast differentiation

Abstract Novel silica hollow flowers (1–5 μm) were synthesized using globular apatite flowers as sacrificed template via a sol–gel route and then employed as biocompatible carrier of bone morphogenetic protein-2 (BMP-2) to stimulate osteoblast differentiation. Apatite was bio-mimetically synthesized from a well-known Kokubo’s simulated body fluid (SBF), then coated with silica in a Stober-type silica sol–gel system, and finally dissolved in an acetic solution to yield silica hollow flowers. Analyses of SEM and TEM images show that the resultant silica flowers had a porous and hollow structure due to removal of apatite template by acetic treatment and their shell was constructed by numerous silica nanosheets (∼10 nm in silica shell). A larger specific surface of 890 m 2 /g was obtained for silica hollow flowers compared to silica-coated apatite due to the presence of porous and hollow structure. Silica hollow flowers had no significant toxicity after incubation with osteoblast MC3T3-E1 cells, indicating a good biocompatibility. They favored adsorption and supported a sustained release behavior of BMP-2. The released BMP-2 was biological active and enhanced osteoblast differentiation with higher ALP activity and larger amount of osteocalcin. The present silica hollow flowers are thus applicable to delivery system in tissue generation.

Ectopic Bone Formation after Implantation of Thermoreversible Gelation Polymer as a Carrier of Bone Morphogenetic Protein-2

Ectopic Bone Formation after Implantation of Thermoreversible Gelation Polymer as a Carrier of Bone Morphogenetic Protein-2

Silk Fibroin-Based Complex Particles with Bioactive Encrustation for Bone Morphogenetic Protein 2 Delivery

Application of bone morphogenetic protein 2 (BMP-2) currently faces its challenges, and its efficacy of delivery has to be improved. The proper dosage of the powerful bioactive molecule is still under discussion and needs to be investigated further. In this work, pure silk fibroin particles and particles with calcium carbonate encrustation (complex particles) are designed, developed, and functionalized by BMP-2. These are used to deliver the bioactive molecule to mesenchymal stem cells (MSCs) to induce osteogenic differentiation. Results are compared with those of control groups of BMP-2 carriers under the same condition. Silk fibroin-based particles with size and component variations are prepared by self-assembly, desolvation, and soft template formation to improve BMP-2 loading efficiency. Results show that the particles significantly enhance osteogenic differentiation of MSCs, which is evident in the high ALP enzyme activity as well as the increased level of expression of osteogenic genes. Specifically, the combination of calcium compound and BMP-2 in the silk fibroin-calcium carbonate complex particles synergistically enhances osteogenesis. Release tests and mathematical modeling are applied to describe BMP-2 dissolution profiles, and the release mechanism is based on diffusion and polymer chain relaxation. In summary, the particles show high efficacies of BMP-2 delivery, and introduction of the complex particle can progressively enhance osteogenesis.