Electrospinner: Preparation of gradient conductive fibers by coaxial wet electrospinning: building a skin-core network structure to improve electromagnetic shielding effectiveness

Background

With the rapid development of electronic and communication technology, the impact of electromagnetic radiation on human life is increasing. Electromagnetic radiation not only interferes with the normal operation of electronic equipment, but also affects people's physical health, and even causes death in severe cases. In order to protect humans from the harm of electromagnetic radiation, it is necessary to develop efficient electromagnetic interference shielding materials. Although traditional metallized fabrics and metal-coated fabrics have excellent electromagnetic shielding performance, they mainly reflect electromagnetic waves, produce secondary pollution, and cause further damage to the surrounding environment. Therefore, it is of great significance to develop shielding fabrics that can effectively absorb electromagnetic energy.

Recently, the Pu Xiong team of the Beijing Institute of Nanoenergy and Systems of the Chinese Academy of Sciences published a research result entitled "Core-Sheath CNT@MXene Fibers Toward Absorption-Dominated Electromagnetic Interference Shielding Fabrics" in Advanced Fiber Materials. This work uses coaxial wet spinning technology to prepare a CNT@MXene fiber with a conductive gradient structure, and its fiber-based fabric achieves electromagnetic shielding performance dominated by absorption. The coaxial fiber has MXene/TPU as the core and CNT/TPU as the skin. By adjusting the content of MXene and CNT, the conductive gradient structure in the fiber is optimized, thereby reducing the reflection of electromagnetic waves on the surface of the fabric, promoting multiple reflections of electromagnetic waves between the skin and the core, effectively absorbing electromagnetic energy, and obtaining electromagnetic shielding performance dominated by absorption (A=0.63). Due to the protective effect of the cortical CNT, the fiber still maintains stable conductive properties under multiple bending, stretching, ultrasonic treatment and high humidity environment conditions. This work shows that conductive gradient structure fibers have great potential in realizing absorption-dominated environmentally friendly electromagnetic shielding fabrics.

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/s42765-024-00452-2