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 (O) 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, 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.