Fabrication and evaluation of a BMP-2/dexamethasone co-loaded gelatin sponge scaffold for rapid bone regeneration

Implantable Dental Barrier Membranes as Regenerative Medicine in Dentistry: A Comprehensive Review

BACKGROUND

Periodontitis and bone loss in the maxillofacial and dental areas pose considerable challenges for both functional and aesthetic outcomes. To date, implantable dental barrier membranes, designed to prevent epithelial migration into defects and create a favorable environment for targeted cells, have garnered significant interest from researchers. Consequently, a variety of materials and fabrication methods have been explored in extensive research on regenerative dental barrier membranes.

METHODS

This review focuses on dental barrier membranes, summarizing the various biomaterials used in membrane manufacturing, fabrication methods, and state-of-the-art applications for dental tissue regeneration. Based on a discussion of the pros and cons of current membrane strategies, future research directions for improved membrane designs are proposed.

RESULTS AND CONCLUSION

To endow dental membranes with various biological properties that accommodate different clinical situations, numerous biomaterials and manufacturing methods have been proposed. These approaches provide theoretical support and hold promise for advancements in dental tissue regeneration.

Cell-permeable bone morphogenetic protein 2 facilitates bone regeneration by promoting osteogenesis

The use of the FDA-approved osteoinductive growth factor BMP2 is widespread for bone regeneration. However, its clinical application has been hindered by limitations in cell permeability and a short half-life in circulation. To address this issue, we have developed a modified version of BMP2, referred to as Cell Permeable (CP)-BMP2, which possesses improved cell permeability. CP-BMP2 incorporates an advanced macromolecular transduction domain (aMTD) to facilitate transfer across the plasma membrane, a solubilization domain, and recombinant human BMP2. Compared to traditional rhBMP2, CP-BMP2 exhibits enhanced cell permeability, solubility, and bioavailability, and activates Smad phosphorylation through binding to BMP receptor 2. The effectiveness of CP-BMP2 was evaluated in three animal studies focusing on bone regeneration. In the initial study, mice and rabbits with critical-size calvarial defects received subcutaneous (SC) injections of CP-BMP2 and rhBMP2 (7.5 mg/kg, 3 injections per week for 8 weeks).Following 8 weeks of administration, CP-BMP2 demonstrated a remarkable 65 % increase in bone formation in mice when compared to both the vehicle and rhBMP2. Moreover, rabbits exhibited faster bone formation, characterized by a filling pattern originating from the center. In a subsequent study involving injured horses, hind limb bones treated with CP-BMP2 exhibited an 85 % higher bone regeneration rate, as evidenced by Micro-CT results, in contrast to horses treated with the vehicle or rhBMP2 (administered at 150 μg/defect, subcutaneously, once a week for 8 weeks, without a scaffold). These results underscore the potential of CP-BMP2 to facilitate rapid and effective healing. No noticeable adverse effects, such as ectopic bone formation, were observed in any of the studies. Overall, our findings demonstrate that CP-BMP2 holds therapeutic potential as a novel and effective osteogenic agent.

Fibrous topology promoted pBMP2-activated matrix on titanium implants boost osseointegration

Titanium (Ti) implants have been extensively used after surgical operations. Its surface bioactivity is of importance to facilitate integration with surrounding bone tissue, and ultimately ensure stability and long-term functionality of the implant. The plasmid DNA-activated matrix (DAM) coating on the surface could benefit osseointegration but is still trapped by poor transfection for further application, especially on the bone marrow mesenchymal stem cells (BMSCs) in vivo practical conditions. Herein, we constructed a DAM on the surface of fibrous-grained titanium (FG Ti) composed of phase-transition lysozyme (P) as adhesive, cationic arginine-rich lipid (RLS) as the transfection agent and plasmid DNA (pDNA) for bone morphology protein 2 (BMP2) expression. The cationic lipid RLS improved up to 30-fold higher transfection than that of commercial reagents (Lipofectamine 2000 and polyethyleneimine) on MSC. And importantly, Ti surface topology not only promotes the DAM to achieve high transfection efficiency (∼75.7% positive cells) on MSC due to the favorable combination but also reserves its contact induction effect for osteoblasts. Upon further exploration, the fibrous topology on FG Ti could boost pDNA uptake for gene transfection, and cell migration in MSC through cytoskeleton remodeling and induce contact guidance for enhanced osteointegration. At the same time, the cationic RLS together with adhesive P were both antibacterial, showing up to 90% inhibition rate against Escherichia coli and Staphylococcus aureus with reduced adherent microorganisms and disrupted bacteria. Finally, the FG Ti-P/pBMP2 implant achieved accelerated bone healing capacities through highly efficient gene delivery, aligned surface topological structure and increased antimicrobial properties in a rat femoral condylar defect model.

Multifunctional modifications of polyetheretherketone implants for bone repair: A comprehensive review

Polyetheretherketone (PEEK) has emerged as a highly promising orthopedic implantation material due to its elastic modulus which is comparable to that of natural bone. This polymer exhibits impressive properties for bone implantation such as corrosion resistance, fatigue resistance, self-lubrication and chemical stability. Significantly, compared to metal-based implants, PEEK implants have mechanical properties that are closer to natural bone, which can mitigate the "stress shielding" effect in bone implantation. Nevertheless, PEEK is incapable of inducing osteogenesis due to its bio-inert molecular structure, thereby hindering the osseointegration process. To optimize the clinical application of PEEK, researchers have been working on promoting its bioactivity and endowing this polymer with beneficial properties, such as antibacterial, anti-inflammatory, anti-tumor, and angiogenesis-promoting capabilities. Considering the significant growth of research on PEEK implants over the past 5 years, this review aims to present a timely update on PEEK's modification methods. By highlighting the latest advancements in PEEK modification, we hope to provide guidance and inspiration for researchers in developing the next generation bone implants and optimizing their clinical applications.

Microenvironment-targeted strategy steers advanced bone regeneration

Treatment of large bone defects represents a great challenge in orthopedic and craniomaxillofacial surgery. Traditional strategies in bone tissue engineering have focused primarily on mimicking the extracellular matrix (ECM) of bone in terms of structure and composition. However, the synergistic effects of other cues from the microenvironment during bone regeneration are often neglected. The bone microenvironment is a sophisticated system that includes physiological (e.g., neighboring cells such as macrophages), chemical (e.g., oxygen, pH), and physical factors (e.g., mechanics, acoustics) that dynamically interact with each other. Microenvironment-targeted strategies are increasingly recognized as crucial for successful bone regeneration and offer promising solutions for advancing bone tissue engineering. This review provides a comprehensive overview of current microenvironment-targeted strategies and challenges for bone regeneration and further outlines prospective directions of the approaches in construction of bone organoids.

Enhanced tissue infiltration and bone regeneration through spatiotemporal delivery of bioactive factors from polyelectrolytes modified biomimetic scaffold

Efficient healing of bone defect is closely associated with the structured and functional characters of tissue engineered scaffolds. However, the development of bone implants with rapid tissue ingrowth and favorable osteoinductive properties remains a challenge. Herein, we fabricated polyelectrolytes modified-biomimetic scaffold with macroporous and nanofibrous structures as well as simultaneous delivery of BMP-2 protein and trace element strontium. The hierarchically structured scaffold incorporated with strontium-substituted hydroxyapatite (SrHA) was coated with polyelectrolyte multilayers of chitosan/gelatin via layer-by-layer assembly technique for BMP-2 immobilization, which endowed the composite scaffold with sequential release of BMP-2 and Sr ions. The integration of SrHA improved the mechanical property of composite scaffold, while the polyelectrolytes modification strongly increased the hydrophilicity and protein binding efficiency. In addition, polyelectrolytes modified-scaffold significantly facilitated cell proliferation in vitro, as well as enhanced tissue infiltration and new microvascular formation in vivo. Furthermore, the dual-factor loaded scaffold significantly enhanced the osteogenic differentiation of bone marrow mesenchymal stem cells. Moreover, both vascularization and new bone formation were significantly increased by the treatment of dual-factor delivery scaffold in the rat calvarial defects model, suggesting a synergistic effect on bone regeneration through spatiotemporal delivery of BMP-2 and Sr ions. Overall, this study demonstrate that the prepared biomimetic scaffold as dual-factor delivery system has great potential for bone regeneration application.

Artificial cilia for soft and stable surface covalent immobilization of bone morphogenetic protein-2

Preservation of growth factor sensitivity and bioactivity (e.g., bone morphogenetic protein-2 (BMP-2)) post-immobilization to tissue engineering scaffolds remains a great challenge. Here, we develop a stable and soft surface modification strategy to address this issue. BMP-2 (a model growth factor) is covalently immobilized onto homogeneous poly (glycidyl methacrylate) (PGMA) polymer brushes which are grafted onto substrate surfaces (Au, quartz glass, silica wafer, or common biomaterials) via surface-initiated atom transfer radical polymerization. This surface modification method multiplies the functionalized interfacial area; it is simple, fast, gentle, and has little effect on the loaded protein owing to the cilia motility. The immobilized BMP-2 (i-BMP-2) on the surface of homogeneous PGMA polymer brushes exhibits excellent bioactivity (⁓87% bioactivity of free BMP-2 in vitro and 20%-50% higher than scaffolds with free BMP-2 in vivo), with conformation and secondary structure well-preserved after covalent immobilization and ethanol sterilization. Moreover, the osteogenic activity of i-BMP-2 on the nanoline pattern (PGMA-poly (N-isopropylacrylamide)) shows ⁓110% bioactivity of free BMP-2. This is superior compared to conventional protein covalent immobilization strategies in terms of both bioactivity preservation and therapeutic efficacy. PGMA polymer brushes can be used to modify surfaces of different tissue-engineered scaffolds, which facilitates in situ immobilization of growth factors, and accelerates repair of a wide range of tissue types.