Electrospinning Equipment: Multifunctional Electrospun Fiber Sponge for Hemostasis and Infected Wound Healing

Driven by the development of micro-nano manufacturing technology, electrospinning technology has become an important means of preparing multifunctional fibrous wound dressings due to its unique advantages. However, most of the existing electrospun wound dressings have a two - dimensional structure and cannot mimic the three - dimensional architecture of the natural extracellular matrix, which limits their applications and calls for innovative improvements. Recently, the research teams led by Prof. Jia - Zhuang Xu and Prof. Zhong - Ming Li from the College of Polymer Science and Engineering, Sichuan University, published their latest research findings titled "Multifunctional Electrospun Fiber Sponge for Hemostasis and Infected Wound Healing" in the journal Small. By using an electrospinning machine to conduct humidity - controlled electrospinning technology and combining it with freeze - drying technology, the teams successfully developed a multifunctional electrospun fiber sponge (EFS) for chronic wound healing. Thanks to its unique fluffy structure, EFS exhibits excellent water absorption, hemostatic, antibacterial, and antioxidant properties. This achievement provides a feasible approach for the engineering design of innovative 3D wound dressings, greatly promotes the progress in the field of infected wound management, and is expected to become a powerful candidate for treating infected wounds.

During the preparation process, the team first dissolved polylactic acid (PLA) in a mixed solvent of dichloromethane (DCM) and N,N - dimethylformamide (DMF) to prepare a 12 wt.% PLA solution. Then, they loaded this solution into an electrospinning machine with humidity - controlled electrospinning technology and set the relative humidity at 90% to spin the PLA solution into fibers. During the electrospinning process in the electrospinning machine, the high - humidity atmosphere caused a humidity - induced phase separation in the PLA solution, making the charged jets deposit in a curled shape and stack to form a unique fluffy structure. Finally, the collected fibers were freeze - dried to remove residual solvents and further fix the sponge - like structure of the fibers. The specific preparation process is shown in Figure 1.

During the preparation process, the team found that adjusting the process parameters could significantly improve the material's performance. For example, when the ratio of the mixed solvent of dichloromethane (DCM) and N,N - dimethylformamide (DMF) used to dissolve polylactic acid (PLA) was adjusted to 7:3 and the relative humidity was controlled at 90%, the electrospun fiber sponge (EFS) prepared therefrom exhibited extremely excellent physical properties. Tests showed that the porosity of this EFS was as high as 99.8%, and its volume density was only 2.8 mg/cm³. This gave it outstanding water absorption performance, allowing it to absorb about 5.39 times its own weight in water (see Figure 2e - f). In addition, after 100 compression cycle tests, the compression resilience of EFS could still reach 87.9%, which fully demonstrated its good shape stability, enabling it to maintain its structural integrity in practical applications and effectively exert its functional characteristics.

The team further functionalized EFS. By incorporating the drugs curcumin (CU) and ciprofloxacin hydrochloride (CIP) into the PLA spinning solution, a composite fiber sponge with antibacterial and antioxidant functions (named CC@EFS) was prepared. Experimental results showed that compared with the traditional two - dimensional fiber membrane (CC@EFM), CC@EFS exhibited a more significant drug release effect in in vitro experiments. The cumulative amount of CU released by CC@EFS was much higher than that of CC@EFM within the same time (see Figure 4a). This was mainly due to the high porosity of CC@EFS, which provided sufficient exchange space for drug release. In the antibacterial performance test, the inhibition zone diameter of CC@EFS against Staphylococcus aureus was approximately 10 times that of CC@EFM, and its antibacterial rates against Escherichia coli and Staphylococcus aureus reached 99.7% and 97.8% respectively, which were significantly higher than those of CC@EFM (see Figure 4b, d). In addition, the DPPH radical scavenging rate of CC@EFS reached 92.9%, which was also much higher than that of CC@EFM, indicating its stronger antioxidant capacity (see Figure 4f).

Benefiting from its unique fluffy morphology, both EFS and its drug - loaded version CC@EFS exhibited excellent hemostatic effects in both in vitro and in vivo experiments. In in vitro experiments, the hemoglobin capture rates of EFS and CC@EFS exceeded 20%, while those of the traditional two - dimensional fiber membrane (EFM) and its drug - loaded version (CC@EFM) were less than 13%. In the in vivo hemostasis evaluation using a rat tail amputation model, the blood loss in the CC@EFS group was significantly reduced, further confirming its excellent hemostatic performance (see Figure 5c - f).

In the in vivo infected wound healing evaluation experiment, the team comprehensively tested CC@EFS using a full - thickness rat wound model infected with S. aureus. The results showed that the wounds in the CC@EFS group recovered significantly on day 3 and were almost completely re - epithelialized by day 14. Histological evaluation further revealed the excellent performance of CC@EFS: it had the smallest wound width, the fastest - growing and thickest granulation tissue, and more mature hair follicles were formed on day 14. Immunofluorescence staining analysis showed that the CC@EFS group significantly inhibited the expression of pro - inflammatory cytokines TNF - α and IL - 6 on day 7, effectively shortening the inflammatory phase; and on day 14, it showed the strongest expression of angiogenesis markers CD31 and VEGF, indicating its ability to effectively promote blood vessel regeneration (see Figure 6). These findings fully confirmed the significant advantages of CC@EFS in eliminating pathogenic bacteria, suppressing the inflammatory response, and promoting wound healing.

In this study, the team developed a simple and scalable strategy to prepare a multifunctional electrospun fiber sponge (EFS) by using an electrospinning machine to conduct humidity - controlled electrospinning technology and combining it with freeze - drying solidification. The sponge with optimized processing parameters exhibited excellent water absorption ratio and shape stability. By incorporating CU and CIP, the resulting CC@EFS displayed superior antibacterial and ROS scavenging capability. Additionally, the unique fluffy morphology enhanced hemostasis both in vitro and in vivo. This study provides a novel and highly effective strategy for fabricating sponge dressings with substantial potential for combating wound infections and expediting wound healing.

Article source: https://doi.org/10.1002/smll.202409969