Vanillin-based photoactive materials: A sustainable approach to antimicrobial solutions

• Novel antimicrobial material obtained using a polyimine as support for a porphyrin photosensitizer. • The new materials show strong biocidal activity, enhancing with each reuse cycle. • The materials prove regenerable by simply reloading the dye and thermal reshaping. • The study highlights effective biomass waste valorization into multifunctional materials. Bacterial infections result in millions of fatalities each year globally, an issue exacerbated by the alarming rise in antibiotic-resistant pathogens. To combat the spread of these microorganisms, photodynamic inactivation strategies can be employed, which kill microbes by generating reactive oxygen species (ROS) without leading to the development of resistance phenomena. Considering the challenges posed by microbial threats and the need for environmental sustainability, a polyimine matrix named VALPOL (VP) was developed using a lignin waste intermediate, vanillin. This matrix was doped with the photosensitizer (PS) 5,10,15,20-tetrakis(4-methylphenyl)-21H,23H-porphyrin (4MeP) to yield two photoactive materials containing 5 % (VP-5-F) and 10 % w/w (VP-10-F) of PS. The VP-based films underwent comprehensive characterization through FTIR spectrophotometry, DSC analysis, and SEM microscopy. Water absorption capacity, diffusion coefficient, film regeneration, and antimicrobial capabilities were also assessed. Following exposure to a blue LED lamp, the VP-doped matrices demonstrated significant antimicrobial efficacy, achieving up to a 3-Log reduction in Staphylococcus aureus viability. This effect was attributed to the material’s ability to generate singlet oxygen via a photodynamic mechanism. Notably, the photokilling effect was enhanced with the reuse of the films, likely due to the morphological changes observed through SEM. The materials exhibited stability, resistance to operational conditions, and ease of molding, combined with light-activated antimicrobial properties, indicating their potential for diverse applications. This research highlights the promise of photoactive vanillin-based films as antimicrobial materials, aligning with sustainable principles in both the photodynamic disinfection method and the material itself.