Fluorophore-Decorated Carbon Nanotubes with Enhanced Photothermal Activity as Antimicrobial Nanomaterials

Alternative approaches to inactivate bacteria through physical damage provide an important solution to problems associated with colonization of material surfaces by antibiotic-resistant bacteria. Here, we present the utilization of carbon nanotubes functionalized with near-infrared (NIR)-absorbing fluorophores as effective photothermal agents that can kill bacteria through laser-activated heat generation. The array of 3,3′-diethylthiatricarbocyanine (DTTC) fluorophores self-assembled on the surface of multiwalled carbon nanotubes (MWNTs) acted as a light-harvesting antenna that increased the NIR light absorption and heat generation capacity of the MWNTs. The MWNT/DTTC nanohybrids generated elevated temperatures reaching 92 °C upon 15 min NIR laser irradiation, resulting in a 77% killing efficiency on Pseudomonas aeruginosa cells in dispersion. When the MWNT/DTTC nanohybrids were embedded into a waterborne polyurethane matrix, the resulting surface coatings presented temperatures reaching 120 °C in only 2 min of laser irradiation, where multiple laser irradiation cycles did not affect the generated temperature elevations. MWNT/DTTC–polyurethane nanocomposite coatings were also demonstrated to kill all P. aeruginosa cells attached to the surface, indicating their strong potential as light-activated antimicrobial and antibiofilm coatings.