Abstract:

Objective Cotton spunlace material is an ideal substrate for medical wound dressings due to its softness, skin-friendliness, environmental protection, and low cost. However, the hydrophilicity and porous structure of the cotton fiber assembly may cause granulation tissue to grow inward, resulting in wound adhesion during wound healing. When the dressing material is removed from the wound, this would cause secondary tissue damage and pain, and prolong the healing time. Therefore, this research sets out to investigate the hydrophobic modification of cotton spunlace materials to enhance the anti-adhesive properties.

Method In this study, the hydrophobicity of cotton spunlace material was achieved by a two-step method. The first step was non-thermal plasma etching to form a rough surface structure, and the second step was to spray polydimethylsiloxane (PDMS) to obtain a stable and safe hydrophobic effect. To achieve the best results, orthogonal experiments were conducted to optimize parameters such as plasma discharge time, discharge power and spray line speed. Subsequently, the hydrophobicity, surface morphology, chemical structure, mechanical properties, anti-adhesion and biocompatibility of the optimized material were thoroughly characterized and analyzed.

Results The optimal process for hydrophobic treatment of cotton spunlace materials was determined by means of orthogonal analysis of variance. The results indicated that when the plasma discharge time was 9 minutes, the discharge power was 25 W, and the spray coating line speed was 5 mm/s, the expected effect could be achieved with the material contact angle being 141.1°. Meanwhile, the electron micrographs clearly showed the existence of micro-nano rough structure on the fiber surface of the optimized material, confirming the effectiveness of the plasma etching process.

The presence of Si elements in the treated materials was proved by elemental analysis, and Si—O and Si—C groups were observed in the infrared spectrum. These findings indicated the effective deposition of PDMS on the material surface. Furthermore, the absorption intensity of PDMS functional groups remained unchanged after heat treatment and n-heptane cleanout. It was illustrated that firm and stable covalent bonds were formed between PDMS and material, and PDMS was grafted with cellulose molecular chain.

In terms of mechanical properties, the elongation at break of the material did not change after treatment, but the tensile strength decreased significantly. Additionally, the anti-adhesion test demonstrated that the optimized treatment effectively improved the anti-adhesive properties of the materials. The peeling energy in the machine direction (MD) was measured as (350.0±29.9) J/m², while in the cross direction (CD) it was (363.1±46.9) J/m², which met the requirements of non-adhesive medical dressings. The biocompatibility evaluation confirmed that the hemolysis rate of the material was (4.19±0.56)%, which met the requirements for biomedical materials. On the other hand, the coagulation index of the material was further reduced than that of the cotton hydroentangled material. It still maintained a gradually decreasing trend with the extension of time, which presented an obvious procoagulant effect. In addition, the cell viability of the optimized material was 89.9%, indicating its non-toxicity.

Conclusion In this paper, a novel environmentally-friendly and safe anti-adhesion medical dressing was developed for cotton spunlace material. The method involves generating rough structure on the surface of material by plasma etching, and then constructing low surface energy surface by spray deposition of PDMS. The optimal process parameters, such as discharge time, discharge power, and spray coating speed, were determined by orthogonal optimization experiments. The effectiveness of plasma etching and PDMS covalent grafting on the surface of materials was demonstrated by the microstructure, elemental composition and infrared spectrum analysis. The anti-adhesive tests showed that the optimized material possessed excellent anti-adhesive properties. Furthermore, the optimized material demonstrated favorable biocompatibility. This research provides insights into constructing hydrophobic surfaces on cellulose-based hydroentangled materials and offers innovative design approaches for the fabrication of anti-adhesive medical dressings.

Key words: surface etching, polydimethylsiloxane, cotton spunlace material, hydrophobic modification, anti-adhesion, medical dressing