Photothermally enhanced bactericidal activity by the combined effect of NIR laser and unmodified graphene oxide against Pseudomonas aeruginosa.

The manuscript shows the application of unmodified graphene oxide (GO) as a photothermally susceptible material to trigger antibacterial effects. The synthesis and characterization of unmodified GO easily dispersed in aqueous solutions is also shown. High GO concentrations in the dark and low GO concentrations irradiated with near infrared light (NIR) produced death in nosocomial bacterium (Pseudomonas aeruginosa). It is demonstrated that GO dispersion in the dark produced a dose-dependent increase in the antibacterial action at concentrations up to 120 µg/mL. On the other hand, by using much lower concentrations (c.a. 2 µg/mL) of GO (non toxic in the dark) and irradiating with near-infrared radiation during 15 min, a degree of mortality of 98.49 % was observed. The P. aeruginosa treated with GO and irradiated exhibited DNA fragmentation due to the physical damage of cell membranes. The GO 2 µg/mL dispersions proved favorable, since they do not induce cell death in the dark, whereas the combination with NIR light triggers the damage to the cell membranes. This characteristic is clearly an advantage in comparison with traditional antibacterial nanomaterials (such as nanoparticles), which induce cell killing due to the nanoparticles toxicity per se. Furthermore, this work provides a novel treatment for combating bacterial nosocomial infections without the use of antibiotics, opening a new area of clinical application via simple photothermal therapy.