Light-activated antibacterial electrospun polyacrylonitrile-graphene quantum dot nanofibrous membranes

Polyacrylonitrile (PAN) nanofibrous membranes incorporating graphene quantum dots (GQD) as photoantibacterial additives were prepared by electrospinning. GQD encapsulation in the composite GQD-PAN membranes proved very stable, with negligible GQD leakage after 1 month immersed in neutral phosphate buffer solutions. A series of GQD-PAN membranes with different GQD content and electrospinning times were prepared to assess the influence of these parameters on the antibacterial activity of the membranes against Escherichia coli under visible light irradiation. Electrospinning time had a pronounced effect on membrane weight/thickness and nanofiber diameter, both parameters increasing with electrospinning time. Membranes with the optimal composition (1% wt. GQD and 1.5 h electrospinning time) showed excellent antibacterial activity against E. coli, with 99.9999% (6 logaritmic units) bacterial inactivation after 24 h illumination with visible light. Different bactericidal reactive oxygen species (ROS) were detected upon illumination of GQD solutions and GQD-PAN membranes, confirming photodynamic inactivation of the bacteria by GQD photosensitization. In terms of ROS production, GQD outperformed well-known photosensitizers crystal violet and toluidine blue O, both with long-established efficiency for photodynamic treatment of drug-resistant bacterial infections.