Abstract:

Objective Burn and scald injuries present significant clinical challenges due to extensive tissue fluid exudation, prolonged healing time, and high susceptibility to secondary infection. These wounds also demand dynamic care to accommodate movement and dressing changes. Conventional wound dressings often fail to adequately manage these complex requirements simultaneously. Aerogels, known for their ultra-high porosity, specific surface area, and exceptional fluid absorption and retention capabilities, hold theoretical promise for creating an optimal moist wound healing environment. However, conventional bulk aerogels suffer from inherent mechanical fragility, making them difficult to process and mold into practical forms and resulting in poor mechanical stability during application. These limitations represent critical bottlenecks preventing the effective utilization of aerogels in advanced wound care, particularly for dynamic burn sites. In order to overcome these fundamental limitations of bulk aerogels, a novel approach of the directionally assembling a nanoporous structure into a one-dimensional fiber form was adopted. This strategy aimed to retain the core beneficial properties of aerogels-specifically, ultra-high porosity, high specific surface area, and excellent liquid absorption and water retention capacity, while simultaneously conferring essential flexibility, knittability, and mechanical adaptability necessary for practical wound dressing applications. This shift from bulk to fiber morphology directly addresses the processing, molding, and stability challenges.

Method Focusing on sodium carboxymethyl cellulose (CMC), a biocompatible polysaccharide, an innovative fibrillation strategy was employed, and a flexible composite antibacterial aerogel fiber was successfully constructed by incorporating copper ions (Cu²⁺) into the CMC-based system. A key innovation in the preparation process was the introduction of Cu²⁺ directly into the spinning dope for aerogel fiber formation. This introduction enabled a critical pre-crosslinking effect before the wet-spinning stage. The mechanism involves coordination bonding between the positively charged Cu²⁺ ions and the negatively charged carboxylate groups present on the CMC molecular chains. This Cu²⁺-carboxylate coordination acted as a powerful molecular directing force, inducing the CMC chains to undergo ordered aggregation and achieve a pre-aligned, oriented arrangement prior to fiber solidification.

Results This coordinated pre-crosslinking and alignment process was pivotal in successfully preparing CMC/Cu²⁺ antibacterial aerogel fibers exhibiting a hierarchical porous structure. The resulting material demonstrated a remarkable enhancement in mechanical strength. Tensile strength measurements reached 12.10 MPa, significantly higher than that observed in equivalent fibers prepared without the Cu²⁺-induced pre-crosslinking step. The molding mechanism is therefore primarily attributed to the synergistic effect of the Cu²⁺-CMC coordination occurring before wet-spinning and the optimized molecular arrangement this induces. This synergy constructs a robust ionic bonding pre-crosslinking network within the fiber, substantially increasing the cross-linking density within the CMC/Cu²⁺ composite. The enhanced cross-linking density is the key factor responsible for the significantly improved mechanical properties of the final aerogel fibers, enabling their practical handling and use as a dressing. Beyond mechanical robustness, the CMC/Cu²⁺ aerogel fibers exhibited potent antibacterial activity. Testing against common wound pathogens, Escherichia coli (E.coli) and Staphylococcus aureus (S.aureus), demonstrated a bacterial reduction rate of 99.99% for both strains. The antibacterial mechanism is attributed to the properties of the Cu²⁺ ions integrated within the fiber matrix. Initially, positively charged Cu²⁺ ions are electrostatically attracted to the negatively charged surface of the microbial cell membrane by Coulomb forces. Following this initial binding, copper ions penetrate the bacterial cell membrane. Inside the cell, Cu²⁺ interacts with vital intracellular components, leading to the coagulation of bacterial proteins and the inhibition of essential enzyme synthesis. This multifaceted action results in efficient and broad-spectrum bactericidal efficacy.

Conclusion This study developed a novel preparation strategy for advanced aerogel wound dressings. By directionally assembling nanoporous CMC into a fiber form and leveraging Cu²⁺ coordination for pre-crosslinking and molecular alignment, flexible composite CMC/Cu²⁺ aerogel fibers were created. These fibers retain the desirable fluid management properties of aerogels, such as high porosity, surface area, absorption, and retention, while overcoming the critical drawbacks of traditional bulk aerogels-namely brittleness, poor processability, and inadequate mechanical stability. The material simultaneously provides significant mechanical strength and potent, stable antibacterial action. This approach offers a promising new pathway for the development of effective functional dressings, particularly relevant for improving the management and treatment outcomes of challenging burn and scald wounds.

Key words: aerogel fiber, antibacterial material, wet spinning, sodium carboxymethyl cellulose, copper ion pre-crosslinking process, functional dressing