Relação estrutura–atividade em compósitos à base de cobre: correlação entre composição e atividade bactericida

Abstract

The phenomenon of antimicrobial resistance drives research into new materials, with copper-based composites showing promise due to their low cost and multiple bactericidal mechanisms of action. This study investigated the correlation between solvothermal synthesis parameters, structural composition, and antimicrobial activity of copper-based materials. A 23 factorial design was used to evaluate the influence of monoethanolamine (MEA) concentration (0.05 and 0.075 M), temperature (120 and 150°C), and reaction time (5 and 20 h). Structural characterization was performed by X-ray diffraction with phase quantification via Rietveld refinement and by HRTEM, while morphology was analyzed by SEM-FEG and optical properties by DRS. Considering the proportional nature of the phases, the data were treated by Compositional Data Analysis, complemented by ANOVA and linear regression. The relative proportions of CuO, Cu2O, and Cu0 varied widely among the experimental conditions, with Cu2O predominating in all tests (>58.8%), while CuO and Cu0 reached maximum values of 34.6% and 33.3%, respectively. ANOVA indicated that the MEA concentration was the main factor associated with phase variation, significantly influencing the formation of CuO and Cu0; for CuO, an interaction effect between MEA and temperature was also observed, while Cu2O showed greater sensitivity to synthesis time. In the case of Cu0, both the MEA concentration and reaction time were found to have an influence. Morphological characterization revealed hierarchical microspheres consisting of nanometric aggregates. HRTEM analysis indicated lattice fringes compatible with the crystallographic planes of Cu2O and CuO, as well as domains attributed to Cu0, confirming the coexistence of the phases identified by XRD. In the biological evaluation, the bactericidal halos ranged from 0 to 2.88 mm and the bacteriostatic halos from 0 to 7.77 mm, the latter being more frequent and extensive. A moderate positive correlation was observed between CuO and bactericidal effect (ρ = 0.48) and a negative correlation with Cu0 (ρ = −0.49). The synthesis routes showed repeatability between independent series, maintaining the majority phase in all tests, and the results indicate an association between compositional variation and biological response in the investigated system.