Towards scalable broad-spectrum photodynamic antimicrobial textiles: synergistic effect of Rose Bengal and commercial cationic fixative on polyamide fabrics

The use of photoactive textiles to reduce infection transmission in healthcare facilities and hospitals is not on the market due to the lack of scalable and cost-effective processes to prepare these materials. To address this issue, a new photodynamic antimicrobial fabric of polyamide with Rose Bengal (RB) and a commercial cationic fixative (CF) was prepared with a simple and scalable procedure using a conventional and industrialized process for incorporating dyes into textiles. Both fabrics (with and without CF) produced more than 99% inactivation of Gram-positive and Gram-negative bacteria (Enterococcus faecalis and Escherichia coli, respectively), as well as viruses such as adenovirus rAd5. Nevertheless, it is worth highlighting that the RB fabric with CF achieved 99.9999% inactivation of E. coli and 99.9% inactivation of fungi such as Candida albicans. The study was performed upon typical indoor illumination with visible light (400–700 nm, 11.3 ± 0.2 mW cm⁻²) during periods covering between 30 and 120 min, according to the tested microorganism. Tests performed with textiles to evaluate the persistence of the RB color in them and their capability to photosensitize the inactivation of microorganisms revealed that the CF improves the robustness of the fabric. Furthermore, the photophysical and photodynamic properties of the fabrics were evaluated by direct and indirect methods. In this context, the formation of photoactivable complexes was observed through the association of RB with CF. Moreover, it was established that the remarkable photodynamic efficiency using the fabric with CF is produced through an electron transfer from microorganisms to an excited RB–CF complex (Type I) and singlet oxygen generated from the triplet excited state of free RB (Type II).