BMP-2 immobilization by phosphonated UV-curable low-molecular-weight chitosan derivative on the surface of titanium

Effect of the Oxygen Concentration and Temperature on Thermal Decomposition of N2O in an Inert Gas

Nitrous oxide (N₂O) is one of the greenhouse gases that contribute to global warming. But, there are few methods for controlling N₂O directly. It is essential to reduce N₂O to solve environmental problems. In this study, we investigate the O₂ concentration dependence of N₂O decomposition under an argon-based gas mixture in a high-temperature thermal reactor. The gas concentrations are calculated using CHEMKIN. The results confirm that more N₂O is converted to N₂ or NO at lower O₂ concentrations. Therefore, the conversion process is hindered by increasing the O₂ concentration. We propose a modified parameter of N₂O decomposition, and it is employed in the CHEMKIN calculations. With the modified parameter, the experimental results are in a similar tendency to the calculated results.

Strategies to Control or Mimic Growth Factor Activity for Bone, Cartilage, and Osteochondral Tissue Engineering

Growth factors play a critical role in tissue repair and regeneration. However, their clinical success is limited by their low stability, short half-life, and rapid diffusion from the delivery site. Supraphysiological growth factor concentrations are often required to demonstrate efficacy but can lead to adverse reactions, such as inflammatory complications and increased cancer risk. These issues have motivated the development of delivery systems that enable sustained release and controlled presentation of growth factors. This review specifically focuses on bioconjugation strategies to enhance growth factor activity for bone, cartilage, and osteochondral applications. We describe approaches to localize growth factors using noncovalent and covalent methods, bind growth factors via peptides, and mimic growth factor function with mimetic peptide sequences. We also discuss emerging and future directions to control spatiotemporal growth factor delivery to improve functional tissue repair and regeneration.

Osteogenic effectiveness of photo-immobilized bone morphogenetic protein-2 using different azidophenyl-natural polymer carriers in rat calvarial defect model

The osteogenetic potential of photo-immobilized azdiophenyl (Az)-natural polymers as a carrier of bone morphogenetic protein-2 (BMP-2) was assessed in 56 rats randomized to four groups. The control group comprised implanted collagen sheet with BMP-2. In the three experimental groups, the implant comprised collagen sheet with photo-immobilized BMP-2 on Az-gelatin (Az-Gel), Az-O-carboxymethyl chitosan (Az-OMC), or Az‑O‑carboxymethyl low molecular chitosan (Az-LMC). Micro-computed tomography analysis revealed more regenerated bone in Az-Gel at 8weeks. Immunohistochemical analysis at 4weeks revealed that the positively expressed cellular ratio in RUNX2-stained cells was significantly higher in Az-Gel and Az-OMC groups. At 8weeks, only the Az-Gel group showed higher positively expressed cellular ratio compared with the control group. These results demonstrate the superior osteogenetic potential of photo-immobilized BMP-2 using Az-Gel carrier in a rat calvarial defect model compared with control group. Photo-immobilization of BMP-2 using Az-gelatin could be a more effective carrier system of BMP-2 than a chitosan-based carrier system.

Effect of Hydroxyapatite Formation on Titanium Surface with Bone Morphogenetic Protein-2 Loading through Electrochemical Deposition on MG-63 Cells

Calcium phosphate ceramics used in dentistry and orthopedics are some of the most valuable biomaterials, owing to their excellent osteoconduction, osteoinduction, and osseointegration. Osteoconduction and osteoinduction are critical targets for bone regeneration, and osseointegration is essential for any dental implantations. In this study, a hydroxyapatite (HAp) hybrid coating layer with the sequential release of bone morphogenetic protein 2 (BMP-2) was deposited onto an etched titanium substrate by electrochemical deposition. The resulting release of BMP-2 from Ti⁻HAp was assessed by immersing samples in a simulated buffer fluid solution. Through coculture, human osteosarcoma cell proliferation and alkaline phosphatase activity were assessed. The characteristics and effect on cell proliferation of the hybrid coatings were investigated for their functionality through X-ray diffraction (XRD) and cell proliferation assays. Findings revealed that -0.8 V vs. Ag/AgCl (3 M KCl) exhibited the optimal HAp properties and a successfully coated HAp layer. XRD confirmed the crystallinity of the deposited HAp on the titanium surface. Ti-0.8 V Ti⁻HAp co-coating BMP sample exhibited the highest cell proliferation efficiency and was more favorable for cell growth. A successful biocompatible hybrid coating with optimized redox voltage enhanced the osseointegration process. The findings suggest that this technique could have promising clinical applications to enhance the healing times and success rates of dental implantation.

Chitosan as a vehicle for growth factor delivery: Various preparations and their applications in bone tissue regeneration

The replacement of conventional autografts and allografts by bone fragments constructed from alternate materials, cells, and molecules (growth factors, drugs, etc.) is an exciting prospect in the field of bone tissue engineering. Bone morphogenetic protein-2 (BMP-2) is a growth factor that has been extensively studied from this point of view. This review analyzes the relevance of chitosan and its derivatives and composites with various materials such as ceramics, heparin, silica, stem cells, titanium implants, etc., in terms of delivering BMP-2 for the purpose of bone regeneration. Chitosan offers the versatility to be modified into any shapes or sizes including conversion to nanoparticles, microspheres, nanofibers, porous scaffolds, and films. The results presented in this review clearly demonstrate that chitosan-based materials are biocompatible and have the potential to systematically and sustainably release BMP-2 where required. This release results in enhanced cell proliferation levels, enhancement of alkaline phosphatase activity, increased differentiation as well as increased mineralization under in vitro and in vivo conditions. This review also shines a spotlight on the currently developed chitosan-based products that are being used for BMP-2 delivery.