A Polyphenol–Metal Network of Propyl Gallate Gallium/Hafnium Oxide on Polyimide Fibers for Facilitating Ligament–Bone Healing

Polymer Chemistry Organic Polymeric Materials Chemistry Materials Science Orthopedics Sports Medicine Life Sciences Bioengineering Medicine
polyimide fiber artificial ligament osteogenesis anti-bacteria anti-inflammation ligament–bone healing

Study on Surface Modification of Polyimide Fibers to Promote Ligament-Bone Healing

Academic Background

Anterior Cruciate Ligament (ACL) injury is one of the most common sports injuries worldwide, with approximately 1 in 1,250 people requiring ACL reconstruction surgery each year. Currently, the main methods for ACL reconstruction include autografts and allografts, but these approaches face issues such as immune rejection and donor site complications. Artificial ligaments, especially non-degradable polymer materials, have gradually become an important choice in clinical practice due to their excellent mechanical strength and rapid postoperative recovery. However, existing artificial ligament materials like Polyethylene Terephthalate (PET) lack sufficient bioactivity in bone regeneration, leading to fibrous encapsulation that hinders ligament-bone healing and increases the risk of surgical failure.

Polyimide (PI) is a polymer material with excellent mechanical properties, thermal stability, and biocompatibility, but its bioinert nature limits its application in bone regeneration. Therefore, how to functionalize polyimide fibers to endow them with multiple biological functions such as promoting bone regeneration, anti-inflammatory, and antibacterial properties has become an important research direction in ACL reconstruction.

Paper Source

This paper was jointly completed by a research team from Donghua University, Shanghai Pudong Hospital of Fudan University, the First Affiliated Hospital of Naval Medical University, and other institutions. The first author of the paper is Xie En, and the corresponding authors are Wei Jie and Li Dejian. The study was published online on October 18, 2024, in the journal Advanced Fiber Materials, titled “A Polyphenol–Metal Network of Propyl Gallate Gallium/Hafnium Oxide on Polyimide Fibers for Facilitating Ligament–Bone Healing.”

Research Process

1. Material Preparation and Characterization

The research team first synthesized Hafnium Oxide (HfO2) nanoparticles via the hydrothermal method and utilized the chelation of Propyl Gallate (PG) with Gallium ions (Ga3+) to prepare a PG-Ga/HfO2 composite coating. Subsequently, Polyimide Fibers (PIF) were immersed in this composite coating solution to obtain functionalized PIF fibers (PGPH). The surface morphology, chemical composition, and structure of the materials were characterized using techniques such as Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). The results showed that the surface roughness, hydrophilicity, and surface energy of PGPH fibers were significantly improved, and the PG-Ga/HfO2 coating was uniformly distributed on the fiber surface.

2. In Vitro Cell Experiments

The research team evaluated the effects of PGPH on the adhesion, proliferation, and osteogenic differentiation of Bone Marrow Mesenchymal Stem Cells (BMSCs) through in vitro cell experiments. The results demonstrated that PGPH significantly promoted the adhesion and proliferation of BMSCs and enhanced Alkaline Phosphatase (ALP) activity and calcium nodule formation, indicating excellent osteogenic differentiation capability. Additionally, PGPH significantly inhibited the polarization of M1 macrophages and promoted the polarization of M2 macrophages, thereby reducing the production of pro-inflammatory cytokines and increasing the secretion of anti-inflammatory cytokines, exhibiting good anti-inflammatory effects.

3. In Vitro Antibacterial Experiments

Through in vitro antibacterial experiments, the research team assessed the antibacterial properties of PGPH against Staphylococcus aureus and Escherichia coli. The results showed that PGPH significantly inhibited bacterial growth, with antibacterial rates reaching 94.6% and 96.5%, respectively. Further mechanistic studies revealed that the Ga3+ ions released by PGPH damaged bacterial cell membranes, leading to the leakage of cellular contents, thereby achieving antibacterial effects.

4. In Vivo Animal Experiments

The research team evaluated the anti-infection and ligament-bone healing-promoting effects of PGPH in vivo using a rat bone marrow cavity infection model and a rabbit ACL reconstruction model. The results showed that PGPH significantly inhibited bacterial infection and promoted new bone formation. In the ACL reconstruction model, PGPH significantly increased the Bone Volume Fraction (BV/TV) and Bone Mineral Density (BMD) and enhanced the integration strength at the ligament-bone interface.

Key Findings

  1. Material Characterization: The surface roughness, hydrophilicity, and surface energy of PGPH fibers were significantly improved, and the PG-Ga/HfO2 coating was uniformly distributed on the fiber surface.
  2. In Vitro Cell Experiments: PGPH significantly promoted the adhesion and proliferation of BMSCs, enhanced ALP activity and calcium nodule formation, and promoted the polarization of M2 macrophages.
  3. In Vitro Antibacterial Experiments: The antibacterial rates of PGPH against Staphylococcus aureus and Escherichia coli reached 94.6% and 96.5%, respectively, with the mechanism involving the release of Ga3+ ions damaging bacterial cell membranes.
  4. In Vivo Animal Experiments: PGPH significantly inhibited bacterial infection and promoted new bone formation, improving the integration strength at the ligament-bone interface in ACL reconstruction.

Conclusion

This study successfully developed a multifunctional artificial ligament material, PGPH, by modifying polyimide fibers with a PG-Ga/HfO2 composite coating. PGPH not only significantly improved the surface properties of the material but also promoted osteogenic differentiation, anti-inflammatory, and antibacterial effects through the release of Hf4+ and Ga3+ ions. In vitro and in vivo experiments demonstrated that PGPH exhibits great potential in promoting ligament-bone healing, providing a new solution for ACL reconstruction.

Research Highlights

  1. Multifunctional Coating Design: The PG-Ga/HfO2 composite coating endowed polyimide fibers with excellent osteogenic, anti-inflammatory, and antibacterial properties.
  2. Significant In Vitro and In Vivo Effects: PGPH significantly promoted osteogenic differentiation of BMSCs and M2 macrophage polarization in vitro and significantly inhibited bacterial infection and promoted new bone formation in vivo.
  3. Potential Clinical Application Value: As a novel artificial ligament material, PGPH has the potential to promote ligament-bone healing and is expected to play an important role in ACL reconstruction.

Other Valuable Information

The experimental design of this study is rigorous, with ample data support, providing new insights into the application of polyimide fibers in the biomedical field. Additionally, the research team comprehensively evaluated the biological performance and mechanisms of PGPH through various characterization techniques and experimental methods, laying the foundation for further development and clinical application of this material.