Porous protoporphyrin IX-embedded cellulose diacetate electrospun microfibers in antimicrobial photodynamic inactivation

Motivated by the need for self-disinfecting materials that can be used to reduce the surface transmission of harmful microbes to healthy hosts, here we prepared a photodynamic antimicrobial membrane comprised of electrospun cellulose diacetate (CA) microfibers into which the photosensitizer protoporphyrin IX (PpIX) was in situ embedded. The resultant porous PpIX-embedded CA (PpIX/CA) microfibrous membranes were prepared with two different photosensitizer loadings: 5 and 10 wt% PpIX with respect to CA (85 and 170 nmol PpIX/mg membrane, respectively). The singlet oxygen ( 1 O 2 ) generated by the embedded photosensitizer was confirmed by electron paramagnetic resonance spectroscopic studies through generation of the TEMPO radical, and its photooxidation efficiency was further investigated using potassium iodide as a model substrate. Antibacterial photodynamic inactivation studies showed that the PpIX/CA membrane achieved a 99.8% reduction in Gram-positive S . aureus after illumination (Xe lamp, 65 ± 5 mW/cm 2 , λ ≥ 420 nm; 30 min), with a lower level of reduction (86.6%) for Gram-negative E . coli . Potentiation with potassium iodide was found to be an effective way to further enhance the antimicrobial efficacy of the PpIX/CA microfibrous membrane, achieving 99.9999% (6 log units) inactivation of both S . aureus and E . coli in the presence of 25 and 100 mM KI, respectively. These findings indicate that the electrospun CA microfibrous membrane is an ideal matrix for a photosensitizer such as PpIX to be embedded and effectively sensitized upon visible light illumination, and its antimicrobial photodynamic inactivation efficiency could be strongly enhanced with the increased KI addition, showing a promising future for its use in pathogen transmission defensive materials.