Layer-by-layer assembled melanin nanoparticles thin films for photodynamic activity-based disinfection by ultraviolet A irradiation

Hospitalized patients with indwelling catheters face the threat of catheter-associated infections (CAIs), which often lead to high morbidity and mortality rates. Disinfection procedures including metal-based antibacterial coatings and photosensitive nanoparticles are unsatisfactory due to concerns associated with long-term toxicity. This study investigates photodynamic capabilities of natural melanin nanoparticles (MNPs) as a layer-by-layer assembled (LBL-A) MNPs thin film to avoid biofilm formation and reveals the physical-chemical properties of LBL-A MNPs thin film using Scanning Electron Microscopy (SEM), Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy, UV-visible spectroscopy, and ability to generate reactive oxygen species (ROS). Additionally, the biocompatibility of LBL-A MNPs thin films in terms of their cytotoxic effect on fibroblast cells was examined. The highest cellular inactivation rates for E. coli bacteria with 86.7% and S. aureus with 80.5% were achieved when the developed LBL-A MNP thin films were exposed to UV-A irradiation (395-400 nm) for 60 s with a distance of 1 cm. In contrast, The LBL-A MNPs thin film protected fibroblast cells against UV-A irradiation with no significant reduction in cell viability. In this regard, the MNPs-based photodynamic method not only enables the treatment of CAIs within only 60 s of UV-A irradiation, but also eliminates the harmful effects of both UV-C and metal-based nanoparticles in living organisms.