Stabilized Loading of Hyaluronic Acid-Containing Hydrogels into Magnesium-Based Cannulated Screws

Area of Science:

• Biomaterials Science
• Orthopedic Surgery
• Materials Engineering

Background:

• Magnesium (Mg)-based cannulated screws offer absorbable fracture fixation but suffer from rapid corrosion and poor mechanical properties.
• Bone resorption and unfavorable pH are concerns with Mg implants.
• Hyaluronic acid (HA) and polygalacturonic acid (PGA) hydrogels can mitigate Mg corrosion and improve biocompatibility.

Purpose of the Study:

• To develop and evaluate Mg-based cannulated screws incorporating a HA-PGA hydrogel with calcium (Ca) ions for enhanced bone healing and controlled degradation.
• To investigate the effect of Ca ion concentration on hydrogel properties, HA release, and biocompatibility.
• To assess the in vivo performance of the modified screws in a rat femur fracture model.

Main Methods:

• Mg-based cannulated screws were fabricated and coated with HA-PGA hydrogels cross-linked with varying Ca ion concentrations.
• Hydrogel properties, including gelation time, degradation rate, and HA release kinetics, were characterized.
• Cytotoxicity assays using osteocytes were performed.
• In vivo studies involved implanting the screws into rat femurs to evaluate bone formation and implant degradation.

Main Results:

• Ca ions influenced hydrogel gelation and dissolution rates, initially delaying degradation but later increasing HA elution.
• High Ca(NO3)2 concentrations (>0.01 M) and low pH inhibited osteoblast function due to HA elution.
• Optimal Ca concentrations in the HA hydrogel successfully delayed Mg degradation and promoted new bone formation and osteocyte expansion in vivo.

Conclusions:

• Mg-based cannulated screws modified with HA-PGA hydrogels and appropriate Ca ion concentrations represent a promising strategy for orthopedic fracture fixation.
• The developed system effectively delays Mg corrosion, enhances bone regeneration, and demonstrates good biocompatibility.
• Careful control of Ca ion concentration is crucial for optimizing hydrogel performance and biological outcomes.