Poliuretanos fotoativos como estratégia de prevenção à resistência bacteriana

Abstract

Quantum carbon dots (CQDs) are amorphous carbon nanoparticles that have specific functionalities, among them, the fluorescence emission at particular wavelengths and the production of singlet oxygen (1O2). However, due to the high solubility in water, it is difficult to coat surfaces with this material. In this context, waterborne polyurethanes (WPU) are attractive as a polymeric support. WPU solubility in aqueous media accelerates the homogeneous distribution of CQDs over the polymer matrix, thus preserving their photoluminescence (FL). In this context, this study consists of the development of photoactive coatings based on CQDs and WPU, capable of being used to prevent the formation of bacterial biofilms. The strategy discussed is because CQDs particles generate 1O2, capable of providing antimicrobial activity to polymeric materials with coating functions. The CQDs synthesized by microwave-assisted pyrolysis, using citric acid and ethylenediamine as carbon and nitrogen sources, showed a spherical morphology with an average size of 10.6 ± 3.1 nm, functional groups containing oxygen and nitrogen on their surface and exhibited photoluminescence at 460 nm with a quantum yield of 63.2% under excitation at 360 nm. Subsequently, these CQDs were incorporated into the WPU synthesis during the phase inversion process. Different spectroscopic and analytical tools such as Fourier transform infrared spectroscopy (FTIR), dynamic-mechanical (DMA), rheological, thermal and mechanical analysis confirmed the structural changes that occurred in the interaction of CQDs with the WPU. The nanocomposites showed greater physical-mechanical stability and thermal stability when compared to pure WPU, due to the interaction of the nanoparticles with the WPU matrix. In addition, the nanocomposites exhibited transparency and high photoluminescence, which confirmed the efficiency of the polymer matrix in protecting the nanoparticles against the extinction of solidstate photoluminescence. Furthermore, the nanocomposites were found to be generators of 1O2 after blue light irradiation and did not show cytotoxicity to BALB/3T3 murine fibroblast cells after 24 h of incubation. The evaluation of antibacterial photodynamic inactivation demonstrated antibacterial efficacy against Pseudomonas aeruginosa (Gram-negative) after illumination, thus validating the great potential of nanomaterials as transparent surface coatings with properties antibacterial photodynamic. [resumo fornecido pelo autor]