Study on Reduced Graphene Oxide-Mediated Titanium Dioxide Photocatalytic Antibacterial Bone Scaffolds

Academic Background

Bacterial infection is one of the most common complications following the implantation of artificial bone scaffolds during bone defect repair. Bacteria form biofilms on the scaffold surface, releasing acids and enzymes that interfere with bone metabolism, destroy the bone matrix, inhibit cell proliferation, and delay bone healing. To address this issue, researchers have been exploring bone scaffold materials with antibacterial functions. Titanium dioxide (TiO₂), as a metal oxide semiconductor, has been widely studied for its ability to photocatalytically produce reactive oxygen species (ROS). However, the rapid recombination of photogenerated electron-hole pairs in TiO₂ results in low photocatalytic efficiency, limiting its potential in antibacterial applications.

To enhance the antibacterial efficiency of TiO₂, researchers have attempted to extend the lifetime and separation efficiency of photogenerated carriers by altering its crystal structure and surface properties. However, the introduction of metal ions may exert cytotoxic effects on cells, affecting bone defect repair. Reduced graphene oxide (rGO), as a highly conductive material, can effectively promote the separation of photogenerated electron-hole pairs while exhibiting good biocompatibility. Therefore, combining rGO with TiO₂ holds promise for improving its photocatalytic antibacterial performance.

Source of the Paper

This paper was co-authored by Pei Feng, Haifeng Tian, Feng Yang, Shuping Peng, Hao Pan, and Cijun Shuai, affiliated with institutions such as the College of Mechanical and Electrical Engineering, Central South University, Xiangya School of Medicine, Central South University, and Xiangya Stomatological Hospital, Central South University. The paper was published online on January 7, 2025, in the journal Bio-design and Manufacturing, with the DOI 10.1631/bdm.2300372.

Research Process

1. Material Synthesis and Characterization

The study first synthesized TiO₂@rGO composites using a hydrothermal method. The specific steps are as follows: - Step 1: 150 mg of graphene oxide (GO) was ultrasonically dispersed in anhydrous ethanol to form a 3 mg/mL GO ethanol solution. - Step 2: 7 mL of tetrabutyl titanate and 0.8 mL of hydrofluoric acid (HF) were gradually added to the solution, stirred for 10 minutes, and then reacted at 150°C for 24 hours. - Step 3: The reaction product was washed with water, centrifuged (6000 r/min, 10 minutes), and dried (24 hours) to obtain the TiO₂@rGO composite.

The material was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy. The results showed that TiO₂ successfully grew on the surface of rGO, forming a Ti-O-C covalent bond. Electrochemical impedance tests revealed that the impedance of the TiO₂@rGO composite was significantly reduced, and the transient photocurrent intensity increased from 0.05 μA/cm² to 0.5 μA/cm².

2. Preparation of Bone Scaffolds

The TiO₂@rGO composite was introduced into poly-l-lactic acid (PLLA) powder, and bone scaffolds with photocatalytic antibacterial functions were prepared using selective laser sintering (SLS) technology. The specific steps are as follows: - Step 1: TiO₂@rGO powder was ultrasonically dispersed in ethanol and mixed with PLLA powder at a mass ratio of 19:1, followed by magnetic stirring for 3 hours to form a uniformly dispersed solution. - Step 2: The mixed solution was centrifuged (6000 r/min, 8 minutes) and dried to obtain PLLA/TiO₂@rGO (PTG) composite powder. - Step 3: A three-dimensional porous scaffold was prepared using an SLS system. The laser power was set to 1.8 W, the scanning speed was 120 mm/s, and the scaffold was fabricated layer by layer until completion.

3. Photocatalytic Activity and Antibacterial Performance Testing

The photocatalytic activity of the PTG scaffold was evaluated using rhodamine B (RhB) degradation experiments. The results showed that the PTG scaffold significantly degraded RhB under ultraviolet (UV) light irradiation, indicating its ability to produce ROS. Antibacterial experiments demonstrated that the PTG scaffold exhibited excellent antibacterial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Under UV light irradiation, the survival rates of E. coli and S. aureus on the PTG scaffold decreased to 40% and 29%, respectively.

4. Mechanical Properties and Biocompatibility Testing

The mechanical properties of the PTG scaffold were evaluated through tensile and compression tests. The results showed that the tensile strength of the PTG scaffold increased from 474 MPa to 640 MPa, the compressive strength increased from 130 MPa to 230 MPa, and the compressive modulus increased from 14.73 MPa to 18.77 MPa. Cell experiments demonstrated that the PTG scaffold exhibited good biocompatibility, promoting the proliferation and adhesion of human bone marrow mesenchymal stem cells (hBMSCs).

Main Results and Conclusions

1. Successful Synthesis of TiO₂@rGO Composite: The TiO₂@rGO composite was successfully synthesized using a hydrothermal method. The high conductivity of rGO significantly promoted the separation of photogenerated electron-hole pairs in TiO₂, improving photocatalytic efficiency.
2. Photocatalytic Antibacterial Performance of PTG Scaffold: Under UV light irradiation, the PTG scaffold produced a large amount of ROS, significantly degrading RhB and exhibiting excellent antibacterial properties against E. coli and S. aureus.
3. Mechanical Properties and Biocompatibility of PTG Scaffold: The mechanical properties of the PTG scaffold were significantly superior to those of pure PLLA scaffolds, while also demonstrating good biocompatibility and promoting cell proliferation and adhesion.

Research Highlights

1. Innovative Material Design: By combining rGO with TiO₂, the study successfully addressed the issue of rapid recombination of photogenerated electron-hole pairs in TiO₂, significantly enhancing its photocatalytic antibacterial performance.
2. Multifunctional Bone Scaffold: The PTG scaffold not only exhibits excellent photocatalytic antibacterial properties but also possesses superior mechanical properties and biocompatibility, providing a new solution for bone defect repair.
3. Broad Application Prospects: This research offers new insights into the development of antibacterial bone scaffolds, with wide-ranging application prospects, particularly in the treatment of bone infections.

Research Significance and Value

Through innovative material design and preparation methods, this study successfully developed a multifunctional bone scaffold with photocatalytic antibacterial properties. This achievement not only enhances the efficiency of TiO₂ in antibacterial applications but also provides a new solution for bone defect repair, holding significant scientific and practical value. In the future, this technology is expected to find widespread clinical application in the treatment of bone infections.