rhBMP-2 Delivery Research Articles

A Narrative Review on Recombinant Human Bone Morphogenetic Protein 2: Where Are We Now?

Spinal fusion is a prevalent surgical intervention for degenerative spinal diseases, with increasing demand driven by ageing populations. The coexistence of multiple chronic conditions, termed multimorbidity, often complicates surgical outcomes, making advanced bone grafts crucial for successful fusions. This paper reviews the development, clinical application, and controversies surrounding the use of recombinant human bone morphogenetic protein-2 (rhBMP-2) in spinal fusion surgeries. A comprehensive narrative review was conducted, focusing on literature from January 1980 to January 2024, sourced from PubMed and Google Scholar. Studies included those examining rhBMP-2 specifically in spinal fusion contexts, excluding other bone morphogenetic proteins (BMPs) and non-spinal applications. This review presents an overarching synopsis of rhBMP-2, its development history and clinical efficacy, the emergence of side effects, and evolving patterns of clinical use. As discussed in this review, clinical practice has adjusted usage and dosages to mitigate adverse effects, yet the need for safer delivery mechanisms persists. rhBMP-2 remains a potent osteoinductive agent with comparable fusion success, as measured by radiographic fusion and good clinical outcomes, to autologous grafts but poses unique risks. This review sets out how further research is essential to optimise the delivery of rhBMP-2 to reduce side effects. Enhanced understanding and innovation of spatio-temporal presentation relative to endogenous BMP could significantly improve patient outcomes in spinal fusion surgeries. The review contributes to the growing body of literature on the use of rhBMP-2 in spine surgery and discusses changing patterns of clinical use over time.

Nanoclay-Modified Hyaluronic Acid Microspheres for Bone Induction by Sustained rhBMP-2 Delivery.

Microspheres (MSs) are ideal candidates as biological scaffolds loading with growth factors or cells for bone tissue engineering to repair irregular alveolar bone defects by minimally invasive injection. However, the high initial burst release of growth factor and low cell attachment limit the application of microspheres. The modification of microspheres often needs expensive experiments facility or complex chemical reactions, which is difficult to achieve and may bring other problems. In this study, a sol-grade nanoclay, laponite XLS is used to modify the surface of MSs to enhance its affinity to either positively or negatively charged proteins and cells without changing the interior structure of the MSs. Recombinant human bone morphogenetic protein-2 (rhBMP-2) is used as a representation of growth factor to check the osteoinduction ability of laponite XLS-modified MSs. By modification, the protein sustained release, cell loading, and osteoinduction ability of MSs are improved. Modified by 1% laponite XLS, the MSs can not only promote osteogenic differentiation of MC3T3-E1 cells by themselves, but also enhance the effect of the rhBMP-2 below the effective dose. Collectively, the study provides an easy and viable method to modify the biological behavior of microspheres for bone tissue regeneration.

An engineered periosteum for efficient delivery of rhBMP-2 and mesenchymal progenitor cells during bone regeneration

During bone regeneration, the periosteum acts as a carrier for key regenerative cues, delivering osteochondroprogenitor cells and crucial growth factors to the injured bone. We developed a biocompatible, 3D polycaprolactone (PCL) melt electro-written membrane to act as a mimetic periosteum. Poly (ethyl acrylate) coating of the PCL membrane allowed functionalization, mediated by fibronectin and low dose recombinant human BMP-2 (rhBMP-2) (10-25 μg/ml), resulting in efficient, sustained osteoinduction in vitro. In vivo, rhBMP-2 functionalized mimetic periosteum demonstrated regenerative potential in the treatment of rat critical-size femoral defects with highly efficient healing and functional recovery (80%-93%). Mimetic periosteum has also proven to be efficient for cell delivery, as observed through the migration of transplanted periosteum-derived mesenchymal cells to the bone defect and their survival. Ultimately, mimetic periosteum demonstrated its ability to deliver key stem cells and morphogens to an injured site, exposing a therapeutic and translational potential in vivo when combined with unprecedentedly low rhBMP-2 doses.

Pilot Study on Percutaneous Delivery of Recombinant Human Bone Morphongenetic Protein-2 Augments Fusion in a Nicotine-impaired Rabbit Fusion Model.

A nicotine-impaired spinal fusion rabbit model. To examine whether controlled delivery of morselized absorbable collagen sponge recombinant human bone morphogenetic protein-2 (rhBMP2) in a delayed manner postsurgery would allow for improved bone healing. The current delivery method of rhBMP-2 during surgery causes a burst of rhBMP-2, which is not sustained. Given that bone morphogenetic protein 2 (BMP-2) expression peaks later in the fusion process, there may be the benefit of delivery of rhBMP-2 later in the healing process. Sixteen male 1-year-old rabbits underwent a posterolateral spinal fusion with iliac crest bone graft at L5-L6 while being given nicotine to prevent spinal fusion as previously published. Eight were controls, whereas 8 had morselized rhBMP-2 (4.2 mg) injected at the fusion site at 4 weeks postoperatively. Histologic, radiologic, and palpation examinations were performed at 12 weeks to determine fusion status and the volume of bone formed. Hematoxylin and eosin stains were used for histology. A Student t test was used to compare the computed tomography scan measured volume of bone created between the control cohort (CC) and rhBMP-2 delayed delivery cohort (BMP-DDC). Of the total, 7/8 rabbits in the BMP-DDC and 5/8 rabbits in the CC formed definitive fusion with a positive palpation examination, bridging bone between transverse processes on computed tomography scan, and an x-ray showing fusion. Histologic analysis revealed newly remodeled bone within the BMP-DDC. There was an increased average volume of bone formed within the BMP-DDC versus the CC (22.6 ± 13.1 vs 11.1 ± 3.6 cm 3 , P = 0.04). Our study shows that injectable morselized absorbable collagen sponge/rhBMP-2 can create twice as much bone within a nicotine-impaired rabbit spine fusion model when delivered 4 weeks out from the time of surgery.

Bringing gene therapy to regenerative medicine

Bringing gene therapy to regenerative medicine

BIOMIMETIC HEMATOMA: NOVEL CARRIER DELIVERS EXTREMELY LOW-DOSE RHBMP-2 FOR HIGHLY EFFECTIVE HEALING OF LARGE BONE DEFECTS IN GOATS

Our previous rat study demonstrated an ex vivo-created “Biomimetic Hematoma” (BH) that mimics the intrinsic structural properties of normal fracture hematoma, consistently and efficiently enhanced the healing of large bone defects at extremely low doses of rhBMP-2 (0.33 μg). The aim of this study was to determine if an extremely low dose of rhBMP-2 delivered within BH can efficiently heal large bone defects in goats.Goat 2.5 cm tibial defects were stabilized with circular fixators, and divided into groups (n=2-3): 2.1 mg rhBMP-2 delivered on an absorbable collagen sponge (ACS); 52.5 μg rhBMP-2 delivered within BH; and an empty group. BH was created using autologous blood with a mixture of calcium and thrombin at specific concentrations. Healing was monitored with X-rays. After 8 weeks, femurs were assessed using microCT.Using 2.1 mg on ACS was sufficient to heal 2.5 cm bone defects. Empty defects resulted in a nonunion after 8 weeks. Radiographic evaluation showed earlier and more robust callus formation with 97.5 % (52.5 μg) less of rhBMP-2 delivered within the BH, and all tibias were fully bridged at 3 weeks. The bone mineral density was significantly higher in defects treated with BH than with ACS. Defects in the BH group had smaller amounts of intramedullary and cortical trabeculation compared to the ACS group, indicating advanced remodeling.The results confirm that the delivery of rhBMP-2 within the BH was much more efficient than on an ACS. Not only did the large bone defects heal consistently with a 40x lower dose of rhBMP-2, but the quality of the defect regeneration was also superior in the BH group. These findings should significantly influence how rhBMP-2 is delivered clinically to maximize the regenerative capacity of bone healing while minimizing the dose required, thereby reducing the risk of adverse effects.

Creation and preclinical evaluation of a novel mussel-inspired, biomimetic, bioactive bone graft scaffold: direct comparison with Infuse bone graft using a rat model of spinal fusion.

Infuse bone graft is a widely used osteoinductive adjuvant; however, the simple collagen sponge scaffold used in the implant has minimal inherent osteoinductive properties and poorly controls the delivery of the adsorbed recombinant human bone morphogenetic protein-2 (rhBMP-2). In this study, the authors sought to create a novel bone graft substitute material that overcomes the limitations of Infuse and compare the ability of this material with that of Infuse to facilitate union following spine surgery in a clinically translatable rat model of spinal fusion. The authors created a polydopamine (PDA)-infused, porous, homogeneously dispersed solid mixture of extracellular matrix and calcium phosphates (BioMim-PDA) and then compared the efficacy of this material directly with Infuse in the setting of different concentrations of rhBMP-2 using a rat model of spinal fusion. Sixty male Sprague Dawley rats were randomly assigned to each of six equal groups: 1) collagen + 0.2 µg rhBMP-2/side, 2) BioMim-PDA + 0.2 µg rhBMP-2/side, 3) collagen + 2.0 µg rhBMP-2/side, 4) BioMim-PDA + 2.0 μg rhBMP-2/side, 5) collagen + 20 µg rhBMP-2/side, and 6) BioMim-PDA + 20 µg rhBMP-2/side. All animals underwent posterolateral intertransverse process fusion at L4-5 using the assigned bone graft. Animals were euthanized 8 weeks postoperatively, and their lumbar spines were analyzed via microcomputed tomography (µCT) and histology. Spinal fusion was defined as continuous bridging bone bilaterally across the fusion site evaluated via µCT. The fusion rate was 100% in all groups except group 1 (70%) and group 4 (90%). Use of BioMim-PDA with 0.2 µg rhBMP-2 led to significantly greater results for bone volume (BV), percentage BV, and trabecular number, as well as significantly smaller trabecular separation, compared with the use of the collagen sponge with 2.0 µg rhBMP-2. The same results were observed when the use of BioMim-PDA with 2.0 µg rhBMP-2 was compared with the use of the collagen sponge with 20 µg rhBMP-2. Implantation of rhBMP-2-adsorbed BioMim-PDA scaffolds resulted in BV and bone quality superior to that afforded by treatment with rhBMP-2 concentrations 10-fold higher implanted on a conventional collagen sponge. Using BioMim-PDA (vs a collagen sponge) for rhBMP-2 delivery could significantly lower the amount of rhBMP-2 required for successful bone grafting clinically, improving device safety and decreasing costs.

Spatial Recombinant Human Bone Morphogenetic Protein 2 Delivery from Hydroxyapatite Scaffolds Sustains Bone Regeneration in Rabbit Radius.

Regenerating large bone defects requires a multifaceted approach combining optimal scaffold designs with appropriate growth factor delivery. Supraphysiological doses of recombinant human bone morphogenetic protein 2 (rhBMP2), typically used for the regeneration of large bone defects clinically in conjunction with an acellular collagen sponge (ACS), have resulted in many complications. In this study, we develop a hydroxyapatite/collagen I (HA/Col) scaffold to improve the mechanical properties of the HA scaffolds, while maintaining open connected porosity. Varying rhBMP2 dosages were then delivered from a collagenous periosteal membrane and paired with HA or HA/Col scaffolds to treat critical-sized (15 mm) diaphyseal radial defect in New Zealand white rabbits. The groups examined were ACS +76 μg rhBMP2 (clinically used INFUSE dosage), HA +76 μg rhBMP2, HA +15 μg rhBMP2, HA/Col +15 μg rhBMP2, and HA/Col +15 μg rhBMP2 + bone marrow-derived stromal cells (bMSCs). After 8 weeks of implantation, all regenerated bones were evaluated using microcomputed tomography, histology, histomorphometry, and torsional testing. It was observed that the bone volume regenerated in the HA/Col +15 μg rhBMP2 group was significantly higher than that in the groups with 76 μg rhBMP2. The same scaffold and growth factor combination resulted in the highest bone mineral density of the regenerated bone, and the most bone apposition on the scaffold surface. Both the HA and HA/Col scaffolds paired with 15 μg rhBMP2 had sustained ingrowth of the mineralization front after 2 weeks compared to the groups with 76 μg rhBMP2, which had far greater mineralization in the first 2 weeks after implantation. Complete bridging of the defect site and no significant difference in torsional strength, stiffness, or angle at failure were observed across all groups. No benefit of additional bMSC seeding was observed on any of the quantified metrics, while bone-implant apposition was reduced in the cell-seeded group. This study demonstrated that the controlled spatial delivery of rhBMP2 at the periosteum at significantly lower doses can be used as a strategy to improve bone regeneration around space maintaining scaffolds. Tweet Inside-out or outside-in: growth factors delivered from the outside of porous mineral-collagen scaffolds, maintain strength and regrow bone better in a rabbit study. Twitter handle for senior author (@Guda_Lab) and sponsoring institution (@UTSA) Impact Statement This study provides insights on bone regeneration in the presence of spatially controlled delivery of recombinant human bone morphogenetic protein 2 (rhBMP2) from porous hydroxyapatite scaffolds coated with collagen I films. Using critical-sized defects created in the radial diaphysis of skeletally mature New Zealand White rabbits, microcomputed tomography and histomorphometry indicated significantly higher bone regeneration, bone mineral density, and bone-implant contact, as well as sustained regeneration over longer durations with lower dosage of rhBMP2 delivered periosteally.

Tissue engineered mimetic periosteum for efficient delivery of rhBMP-2

Tissue engineered mimetic periosteum for efficient delivery of rhBMP-2

A combined cell and growth factor delivery for the repair of a critical size tibia defect using biodegradable hydrogel implants.

The ability to repair critical‐sized long‐bone injuries using growth factor and cell delivery was investigated using hydrogel biomaterials. Physiological doses of the recombinant human bone morphogenic protein‐2 (rhBMP2) were delivered in a sustained manner from a biodegradable hydrogel containing peripheral human blood‐derived endothelial progenitor cells (hEPCs). The biodegradable implants made from polyethylene glycol (PEG) and denatured fibrinogen (PEG‐fibrinogen, PF) were loaded with 7.7 μg/ml of rhBMP2 and 2.5 × 106 cells/ml hEPCs. The safety and efficacy of the implant were tested in a rodent model of a critical‐size long‐bone defect. The hydrogel implants were formed ex‐situ and placed into defects in the tibia of athymic nude rats and analyzed for bone repair after 13 weeks following surgery. The hydrogels containing a combination of 7.7 μg/ml of rhBMP2 and 2.5 × 106 cells/ml hEPCs were compared to control hydrogels containing 7.7 μg/ml of rhBMP2 only, 2.5 × 106 cells/ml hEPCs only, or bare hydrogels. Assessments of bone repair include histological analysis, bone formation at the site of implantation using quantitative microCT, and assessment of implant degradation. New bone formation was detected in all treated animals, with the highest amounts found in the treatments that included animals that combined the PF implant with rhBMP2. Moreover, statistically significant increases in the tissue mineral density (TMD), trabecular number and trabecular thickness were observed in defects treated with rhBMP2 compared to non‐rhBMP2 defects. New bone formation was significantly higher in the hEPC‐treated defects compared to bare hydrogel defects, but there were no significant differences in new bone formation, trabecular number, trabecular thickness or TMD at 13 weeks when comparing the rhBMP2 + hEPCs‐treated defects to rhBMP2‐treated defects. The study concludes that the bone regeneration using hydrogel implants containing hEPCs are overshadowed by enhanced osteogenesis associated with sustained delivery of rhBMP2.

Dual-function injectable fibrin gel incorporated with sulfated chitosan nanoparticles for rhBMP-2-induced bone regeneration

Bone fractures commonly occur in the aging patients, and exhibit slow fracture healing rates and high complication rates even with the best treatment strategies available. Additionally, aging patients always suffer from immunosenescence, and thus induce the dysfunction of macrophages to delay the bone repair. Although exogenous bone morphogenetic protein-2 (BMP-2) is verified that can efficiently promote bone regeneration, the supraphysiologic usage is always associated with abnormal heterotopic ossification and inflammatory response. Here, we have developed a dual-function injectable fibrin gel (Fg) with semisynthetic sulfated chitosan (SCS) nanoparticles (NPs) that significantly improves the recombinant human BMP-2 (rhBMP-2)-induced osteogenesis and down-regulates the inflammatory response at the fracture site. The prepared fibrinogen and sulfated chitosan nanoparticles (SCS NPs) efficiently prolong the delivery of rhBMP-2 and decrease the volume of bone callus. Moreover, SCS incorporated Fg regulates the macrophage polarization from pro-inflammatory M1 macrophage to anti-inflammatory M2 macrophage with a significant decrease of inflammatory-related cytokines. Finally, this dual-function injectable gel can also efficiently treat bone fractures well in postmenopausal mice with osteoporosis. Thus, this pro-osteogenic gel offers a translational potential for biomaterial-based bone healing.

RhBMP-2-Loaded PLGA/Titanium Nanotube Delivery System Synergistically Enhances Osseointegration.

Although Ti-based implants have been widely used, osseointegration failure can also be found between implants and the surrounding bone tissue, especially in aged patients or in patients with certain systemic diseases. Therefore, in this research, we establish a sustained rhBMP-2 delivery system on a titanium implant surface, an anodic oxidation TiO2 nanotube layer combined with the PLGA film, to enhance osseointegration. This designed system was characterized as follows: surface topography characterization by SEM and AFM; rhBMP-2 release; and the ability to influence MC3T3 cell adhesion, proliferation, and osteogenic differentiation in vitro. Additionally, we evaluated the ability of this system to generate new bone around implants in rabbit tibias by the histological assay and removal torque test. SEM and AFM showed that PLGA membranes were formed on the surfaces of TiO2 nanotube arrays using 1, 3, and 10% PLGA solutions. The 3% PLGA group showed a perfect sustained release of rhBMP-2, lasting for 28 days. Meanwhile, the 3% PLGA group showed improved cell proliferation and osteogenic mRNA expression levels. In the in vivo experiments, the 3% PLGA group had the ability to promote osteogenesis in experimental animals. The anodized TiO2 nanotube coated with a certain thickness of the PLGA layer was an ideal and suitable rhBMP-2 carrier. This modified surface enhances osseointegration and could be useful in clinical dental implant treatment.

Prognosis of single tooth implants following alveolar ridge preservation with two recombinant human bone morphogenetic protein-2 delivery systems

Background We previously reported similar efficacies of alveolar ridge preservation (ARP) on single extraction socket with two different E. coli derived recombinant human bone morphogenetic protein-2 (rhBMP-2) delivery systems (Cowell BMP, Cowell medi Co, Busan, Korea; β-tricalcium phosphate and hydroxyapatite particle & O-BMP, Osstem Implant Co, Busan, Korea; absorbable collagen sponge). After the trial, we completed implant therapy and observed over an average of 3 years. This follow-up study was performed retrospectively to compare result of implant treatment at the preserved alveolar ridge site.Methods Patients who underwent extraction of single tooth and received ARP with one of two rhBMP-2 delivery systems from October 2015 to October 2016 were enrolled. Twenty-eight patients (Group 1: Cowell BMP 14; Group 2: O-BMP 14) who underwent implant therapy and prosthetic treatment were included in study. Stability and marginal bone loss (MBL) of each implant were collected from medical charts and radiographs, and analyzed. The survival and success rates of implants were calculated.ResultsThe primary implant stability represented by implant stability quotient (ISQ) for Groups 1 and 2 was 69.71 and 72.86, respectively. The secondary implant stability for Groups 1 and 2 was 78.86 and 81.64, respectively. Primary and secondary stabilities were not statistically different (P = 0.316 and 0.185, respectively). MBL at the latest follow-up was 0.014 mm in Group 1 over 33.76 ± 14.31 months and 0.021 mm in Group 2 over 40.20 ± 9.64 months, with no significant difference (P = 0.670). In addition, the success rate of implants was 100% (14/14) in Group 1 and 92.9% (13/14) in Group 2, with survival rate of 100% (14/14) in Group 1 and 92.9% (13/14) in Group 2.ConclusionsWe confirmed good prognosis in both groups as a result of implant therapy after ARP with each of two rhBMP-2 carriers.

Sequential drug delivery of vancomycin and rhBMP-2 via pore-closed PLGA microparticles embedded photo-crosslinked chitosan hydrogel for enhanced osteointegration

As generally accepted, inhibiting the bacterial invasion at initial stage and promoting the behavior of related osteogenesis cells afterwards is crucial to achieve favorable osteointegration after dental implantation. In this study, a novel combined structured hydrogel composed of chitosan and pore-closed poly(lactic-co-glycolic acid) microparticles was prepared and characterized. In vitro and in-vivo studies have identified that this biocompatible material can rapidly release vancomycin at initial 2 days and then sustainedly release recombinant human bone morphogenetic protein-2 for about 12 days, thus respectively accomplish antibacterial and osteogenesis functions. This sequential drug release system can be used as a promising coating material to improve the surface conditions of dental implant to enhance the osteointegration after surgery.

Osteoinductive 3D printed scaffold healed 5\xa0cm segmental bone defects in the ovine metatarsus

Autologous bone grafts are considered the gold standard grafting material for the treatment of nonunion, but in very large bone defects, traditional autograft alone is insufficient to induce repair. Recombinant human bone morphogenetic protein 2 (rhBMP-2) can stimulate bone regeneration and enhance the healing efficacy of bone grafts. The delivery of rhBMP-2 may even enable engineered synthetic scaffolds to be used in place of autologous bone grafts for the treatment of critical size defects, eliminating risks associated with autologous tissue harvest. We here demonstrate that an osteoinductive scaffold, fabricated by combining a 3D printed rigid polymer/ceramic composite scaffold with an rhBMP-2-eluting collagen sponge can treat extremely large-scale segmental defects in a pilot feasibility study using a new sheep metatarsus fracture model stabilized with an intramedullary nail. Bone regeneration after 24 weeks was evaluated by micro-computed tomography, mechanical testing, and histological characterization. Load-bearing cortical bridging was achieved in all animals, with increased bone volume observed in sheep that received osteoinductive scaffolds compared to sheep that received an rhBMP-2-eluting collagen sponge alone.

Human Fresh Fibrin Membrane with Bone Morphogenetic Protein-2 (BMP-2) Induces Bone Formation in the Subcutaneous Tissues of Nude Mice.

Autologous blood-derived fibrin glue with platelets, called the concentrated growth factor (CGF), can be prepared immediately by only the decided centrifuge without the addition of coagulation factors. Collagen materials combined with recombinant human BMP-2 have been commercially available for clinical use. The fresh CGF is auto-clot with wettability and elasticity, while most collagen membranes are derived from the cow or pig. The fresh CGF has wettability and elasticity, while collagen membranes are dry materials without elasticity. The aim of this study was to observe the microstructures of human CGF membrane and evaluate its behavior as a delivery scaffold of rhBMP-2 in the subcutaneous tissues of nude mice. Twenty-four nude mice (5-week-old, male) were used for the assessment of in vivo ectopic bone formation. Mice were received the CGF membrane as the controls and the CGF/rhBMP-2 membrane as the experimental group in the subcutaneous tissues, and harvested at 7, 10, and 14 days after the graft. Harvested samples were evaluated for the histological examination and the histomorphometric measurement was conducted to compare the residue of the CGF, as well as the new bone. Mature fibrin fibers assembled from multiple fibrillary elements and platelets with the rhBMP-2 membrane induced several bony islands and cartilage without residues of CGF at 14 days, while the CGF membrane alone was almost absorbed at 10 days and failed to induce bone formation at 14 days. These results demonstrated that the fresh, human CGF membrane could contribute to a short-term, sticky fibrin matrix for the delivery of rhBMP-2.

Nanostructured Carbonated Hydroxyapatite Associated to rhBMP-2 Improves Bone Repair in Rat Calvaria.

Many biomaterials are used for Bone Morphogenetic Proteins (BMPs) delivery in bone tissue engineering. The BMP carrier system’s primary function is to hold these growth factors at the wound’s site for a prolonged time and provide initial support for cells to attach and elaborate the extracellular matrix for bone regeneration. This study aimed to evaluate the nanostructured carbonated hydroxyapatite microspheres (nCHA) as an rhBMP-2 carrier on rats calvaria. A total of fifteen male Wistar rats were randomly divided into three groups (n = 5): clot (control group), rhBMP-2 associated with collagen membrane (COL/rhBMP-2) or associated with the microspheres (nCHA/rhBMP-2). After 45 days, the calvaria defect samples were evaluated through histological, histomorphometric, and SR-µCT analyses to investigate new-formed bone and connective tissue volume densities. The descriptive histological analysis showed that nCHA/rhBMP-2 improved bone formation compared to other groups. These results were confirmed by histomorphometric and SR-µCT analysis that showed substantially defect area filling with a higher percentage of newly formed (36.24 ± 6.68) bone than those with the COL/rhBMP-2 (0.42 ± 0.40) and Clot (3.84 ± 4.57) (p < 0.05). The results showed that nCHA is an effective carrier for rhBMP-2 encouraging bone healing and an efficient alternative to collagen membrane for rhBMP-2 delivery.

Response Surface Methodology for Statistical Optimization of Chitosan/Alginate Nanoparticles as a Vehicle for Recombinant Human Bone Morphogenetic Protein-2 Delivery.

PurposeIn this study, chitosan/alginate nanoparticles are prospected as a carrier for controlled release of recombinant human bone morphogenetic protein-2 (rhBMP-2).Materials and MethodsThe rhBMP-2-loaded chitosan/alginate nanoparticles (Cs/Alg/B NPs) were prepared using the ionic gelation (IG) method. The current research was conducted to optimize the effective factors for entrapping rhBMP-2 in Cs/Alg NPs using response surface methodology (RSM) and the Box–Behnken design (BBD). The variables were the Cs/Alg molecular weight (Mw) ratios (1–3), pH (4.8–5.5), stirring rates (900–1300 rpm) and the responses included size, ζ-potential, polydispersity index (PDI), loading efficacy (LE), cumulative release (CR), and morphological degradation time (MDE). Then, the morphological properties of optimum formulation were studied for post-characterization. In the next step, the MTT assay for the optimized run was done for 24 and 48 hours.ResultsThe results revealed that the optimum conditions for the mentioned variables were stirring rate=1100 rpm, pH=5.15, and Cs/Alg Mw ratio=1.75 based on numerical optimization. It was shown that the average particle size and loading efficacy at optimum conditions were 253 nm and 67%, respectively. Other responses were as follows: CR=66%, ζ-potential=+35mV, PDI=0.5, and MDT=7 days.ConclusionThe results have suggested that the statistical optimization of rhBMP-2 offers the possibility of preparing Cs/Alg/B NPs with a favorable size, controlled release characteristics, and high loading efficiency. It is expected that the acquired optimum conditions will be useful for efficient rhBMP-2 delivery.

Biodegradable Zwitterion/PLGA Scaffold Enables Robust Healing of Rat Calvarial Defects with Ultralow Dose of rhBMP-2.

Designing smart scaffolds to reduce administration dosage under the premise of functional healing of bone defects to avoid the severe side effects associated with BMP-2 treatments is one of the essential goals in bone tissue engineering. Here, we report a novel biodegradable PLGA/PSBMA composite as the scaffold for bone tissue engineering. The introduction of zwitterionic PSBMA components can alter the intrinsic burst degradation behavior of PLGA and enable a sustained degradation of the scaffold over the time. The PLGA/PSBMA scaffold can sequester rhBMP-2 and enable a sustained release of the sequestered rhBMP-2 with preserved bioactivity. Furthermore, PLGA/PSBMA scaffolds were able to guide robust healing of critical-sized nonunion calvarial defects (5 mm) at an ultralow dose of 400 ng/scaffold, at which level successful healing of critical-sized bone defects has never been reported. These findings indicate the PLGA/PSBMA scaffolds as novel high-efficiency rhBMP-2 delivery vehicles for bone tissue engineering, and the concept of utilizing the material, which is capable of maintaining the bioactivity of the proteins in the preparation of scaffolds, may open a new avenue for the design of smart scaffolds/vehicles for high-efficiency protein/bioactive drug therapies.

Synthesis and Characterization of a Biocomposite Bone Bandage for Controlled Delivery of Bone-Active Drugs in Fracture Nonunions.

Fracture nonunions are common in orthopedics and their treatment often involves multiple surgical interventions. The aim of this study was to fabricate and characterize a gelatin-nano-hydroxyapatite membrane (GM)-based bone bandage for controlled delivery of bio-active molecules; recombinant human bone morphogenic protein-2 (rhBMP-2) and zoledronic acid (ZA) to promote osteoinduction and prevent callus resorption, respectively. In vitro cell-material interaction experiments using MC3T3 cells seeded on the GM indicated good biocompatibility. rhBMP-2-functionalized GM promoted osteogenic differentiation of MC3T3 cells and the rhBMP-2 bio-activity thus remained, as indicated by increased levels of alkaline phosphatase compared to only GM. The GM released a small amount (1.1%) of rhBMP-2 in vitro over a period of 5 weeks, demonstrating a strong interaction of rhBMP-2 with the GM. In the first animal study, the GM specimens loaded with rhBMP-2 or with the combination of rhBMP-2 + ZA were placed in the abdominal muscle pouch of rats. In the GM + rhBMP-2 + ZA group, significantly higher bone volume (21.5 ± 5.9 vs 2.7 ± 1.0 mm3) and area (3.3 ± 2.3 vs 1.0 ± 0.4 mm2) of bone were observed compared to GM + rhBMP-2 after 4 weeks, as indicated by micro-computed tomography and histomorphometry, respectively. Finally, a nonunion model in rats was used to evaluate the efficacy of the GM bandage and bio-active molecules in healing of fracture nonunions. The GM functionalized with rhBMP-2 + ZA led to higher bone formation around the fracture (63.9 ± 19.0 vs 31.8 ± 3.7 mm3) and stronger fracture callus (110.8 ± 46.8 vs 45.6 ± 17.8 N) compared to the empty controls. However, the overall union rate was only marginally improved. The GM alone or combined with ZA did not aid in bone healing in this model. Thus, this study shows that controlled delivery of rhBMP-2 + ZA via the developed GM is a promising approach that could aid in earlier full load bearing in patients with nonunion.