Electrospinner: Composite Nanofiber Membrane loaded with electret: reshaping the microenvironment and promoting bone repair

Background

Natural bone tissue has piezoelectricity, and maintaining the electrophysiological microenvironment of bone repair is conducive to bone regeneration and remodeling. Electroactive materials implanted in the body can regulate cell behavior and are expected to provide solutions for bone repair. However, traditional electroactive materials have disadvantages such as non-degradability, requiring secondary surgery to remove, risk of infection when connected to an external power source, and difficulty in controlling the size of the electrical stimulation generated in response to mechanical force.

Recently, the research team led by Lin Kaili from the Ninth People's Hospital affiliated to Shanghai Jiao Tong University School of Medicine published a research result entitled "Remodeling Electrophysiological Microenvironment for Promoting Bone Defect Repair via Electret Hybrid Electrospun Fibrous Mat" in Advanced Fiber Materials. They reported a coaxial electrospun PLLA/PCL fiber membrane (EHFM) loaded with electret SiO2. The matrix material is degradable, and the fiber structure simulates the extracellular matrix (ECM) to facilitate cell adhesion. The electret SiO2 in the fiber core layer maintains a stable electrophysiological microenvironment and can effectively repair critical-size skull defects in rats. Its osteogenesis mechanism is related to the electret-activated CaSR and CaM/CaN/NFAT signaling pathways, showing the application value of this material in the field of bone repair.

The main point of this paper

Figure 1a-b shows the electret-loaded SiO2 Nanofiber Membrane constructed by coaxial electrospinning, which has a surface morphology and core-shell structure similar to that of ECM. As can be seen from Figure 1c, after the EHFM was polarized by the electric field, the surface potential of the electret SiO2 group was significantly higher than that of the control group. The surface potential was positively correlated with the electret concentration and tended to be stable after 6 hours. After immersion in PBS, it was detected that each group could maintain a stable surface potential within 28 days. Figure 1d is a COMSOL software simulation of the EHFM potential distribution in bone tissue, indicating that EHFM can maintain a stable surface potential after polarization and has the ability to reshape the electrophysiological microenvironment of bone repair.

Figure 2 shows the results of in vitro experiments. Rat bone marrow mesenchymal stem cells (BMSCs) were cultured on the surface of EHFM to detect cell adhesion, proliferation and osteogenic differentiation. As shown in Figure 2a-c, the cell spreading area on the surface of the electret SiO2 group was large and the proliferation rate was high, indicating that EHFM can promote the adhesion and proliferation of BMSCs. The results of ALP activity detection showed that EHFM can promote the osteogenic differentiation level of stem cells (Figure 2d-e). Among them, 2% SiO2 has a more obvious effect of promoting cell adhesion, proliferation and osteogenic differentiation, and is used as the optimized concentration for subsequent research. The PCR and immunofluorescence staining experiments in Figure 2f-g further verified the in vitro osteogenic differentiation effect of EHFM.

In addition, calcium ion fluorescent probe staining and flow cytometry detection found that the intracellular calcium ion concentration of BMSCs cultured on the surface of EHFM increased significantly (Figure 3a-b). Therefore, the expression changes of proteins related to the calcium ion signaling pathway were detected, as shown in Figure 3c-e, indicating that EHFM upregulated the expression levels of NFAT, CaN, and CaM by activating CaSR, and after adding CaSR inhibitors, the corresponding protein expression and ALP activity levels decreased, indicating that the biological mechanism of EHFM promoting osteogenic differentiation of stem cells is related to the activation of NFAT/CaN/CaM signaling pathway by CaSR, and its possible biological mechanism is shown in Figure 3f.

A critical-size skull defect model was further constructed in rats, and EHFM was filled in layers to repair the skull defect. From the Micro-CT three-dimensional reconstruction, Van Gieson, H&E and sequential fluorescence staining results in Figure 4, it can be seen that EHFM has a significant effect on promoting new bone formation in vivo.

In summary, the overall idea and results of this study are shown in Figure 5. The Nanofiber Membrane loaded with electret SiO2 was constructed by coaxial electrospinning. The surface structure of ECM promoted cell adhesion and growth. The electret SiO2 in the fiber core layer can maintain a stable electrophysiological microenvironment for bone repair, has the potential to promote osteogenic differentiation in vitro, and has an excellent bone repair effect in the critical size skull defect model. Its osteogenic effect is related to the activation of the NFAT/CaN/CaM signaling pathway by CaSR. The new electret Nanofiber Membrane prepared in this study can generate electrical stimulation in situ, which overcomes the shortcomings of traditional electroactive materials that require external power supply and respond to external mechanical force stimulation. The surface potential is controllable and the matrix material is degradable, which provides a useful idea for the design of bone healing biomaterials.

Electrospinning Nanofibers Article Source:

https://link.springer.com/article/10.1007/s42765-024-00457-x