Abstract:

Objective The traditional antibacterial nonwovens are known for their inferior contact comfort, significant potential toxicity, unsatisfactory protective performance and high preparation cost. In this study, skin-friendly spunlaced cotton was selected as the substrate which were then coated by a mixture of low molecular weight chitosan, covalently crosslinked citric acid and photosensitizers. This material is featured efficient and extensive antimicrobial, green and low pollution, stable effect and superior biosafety.

Method Photodynamic antimicrobial spunlaced cotton fabric was prepared by covalent crosslinking and integration of dyeing and finishing. The chemical structure and photodynamic properties of photodynamic spunlaced cotton were characterized using UV-visible spectrophotometer, Fourier infrared spectrometer and fluorescence spectroscopy. The antimicrobial performance and durability of the photodynamic spunlaced cotton were investigated by antimicrobial experiments under different contact periods.

Results The FT-IR spectra and water solubility test demonstrated the successful synthesis of chitosan guanidinium salt (GCS). The color space parameters and color depth curves confirmed that the color depth curves of the photodynamic spunlaced cotton matched the UV-visible absorption spectra of the corresponding photosensitizers, with color depth values of 3.55 and 4.72 for CHL-GCF(spunlaced cotton loaded with chitosan guanidinium salt and sodium copper chlorophyllin) and RB-GCF(spunlaced cotton loaded with chitosan guanidinium salt and rose bengal), respectively. The above results indicated that the cationic surface modified with chitosan guanidinium salt facilitated the loading of negatively charged photosensitizers. The dyeing rate and loading amount of sodium copper chlorophyllin (CHL) and rose bengal (RB) on the GCF surface were further determined by measuring the absorbance of the dye solution before and after the photosensitiser staining and the washing residual solution. The staining rates of CHL-GCF and RB-GCF reached 95.78% and 96.46%, respectively, and the loading amounts of CHL-GCF and RB-GCF after washing were 18.57 mg/g and 17.24 mg/g, respectively. The anionic photosensitiser and actionized spunlaced cotton relied on electrostatic interactions to achieve relatively excellent upstaining and loading effects under salt-free dyeing. The results demonstrated that the photodynamic spunlaced cotton killed more than 99% of S. aureus in 15 minutes and more than 90% of E. coli in 60 min, as well as less potential toxicity to cells, which met the relevant requirements for biomedical materials. Finally, the breaking elongation property, air permeability, water vapor transmissibility and UV resistance of photodynamic spunlaced cotton were investigated. Compared with NCF, the breaking strength retention rate of GCF, CHL-GCF and RB-GCF was approximately 70%. The air permeability and water vapour transmission rate of the photodynamic spunlaced cotton were reduced to 1 442.92 mm/s and 2 475.8 g/(m²·d), respectively, by approximately 15% in both cases. The UV resistance coefficients reached 32.26±1.15 and 19.78±0.48, respectively, with certain UV blocking ability.

Conclusion The spunlaced cotton with photodynamic microbial inactivation effect was successfully developed by adopting spunlaced cotton as the substrate, modified by covalent cross-linking with chitosan guanidinium salt, and then loaded with the photosensitiser chlorophyll copper sodium salt or rose bengal red by salt-free dyeing method. Under the simulated sunlight conditions, the photodynamic spunlaced cotton eliminated over 99% of S. aureus in 15 min, and over 90% of E. coli in 60 min, exhibiting good efficient inactivation performance and usage durability. According to the relevant standards for testing textile physical properties and biosafety indicators, photodynamic spunlaced cotton met the corresponding performance requirements, indicating outstanding contact comfort and safety.

Key words: spunlaced cotton, photodynamic microbial inactivation, chitosan guanidinium salt, antimicrobial, integration of dyeing and finishing, functional textle