Compósitos a base de óxido de grafeno/complexo de cobre e seus efeitos antifúngicos

Abstract

Materials with antifungal properties are a major challenge, as most fungi in the form of biofilms are becoming resistant to pharmacological applications, hindering the eradication of these fungal infections. Thus, developing graphene oxide (GO)-based composites emerges as a promising alternative, mainly due to their carrying potential. The scarcity of studies using this nanomaterial with metal complexes aimed at biological actions is still an area to be further explored, as most studies focus on enhancing the intrinsic properties of GO. Thus, the objective of this study is to prepare GO-based composite formulations with tannic acid (TA) and tannic acid-copper II complex (TA-Cu(II)) as active ingredientes acting as planktonic cell biofilms. This study consists of two stages. The first stage involves structural characterization and in vivo testing of AT-Cu(II). The second stage involves the synthesis, structural characterization, and in vitro of GO-TA and GO-TACu(II). Using characterization techniques, it was possible to propose a structural model for TA-Cu(II), with the copper(II) metal ion coordinated to TA via a covalent bond, possessing a distorted pseudo-octahedral geometry with a planar square base and a single copper atom as the metal center, as indicated by copper quantification via ICP-OES (3.10±0.10%), and the presence of acetates participating in the molecular structure, as determined by 1H NMR. For the composites in FTIR, there was a decrease in intensity and the appearance of bands related to the aromatic region, stretching and angular deformations of esters, and the appearance of a new bands 1003 and 947 cm-1 related to Cu-O-C for the composite with copper. In Raman, there was greater disorganization of the GO layers with incorporation of the starting materials, related to slight crystallization in XRD. Decrease in the hydrophilic potential of the composites and the formulation containing the copper complex was stable at both acidic and neutral pH levels. In vitro antifungal assays showed promising results for formulations containing copper, showing that in the presence of the Cu(II) ion, the minimum inhibitory concentration (MIC) was reduced or similar to the TA ligand and GO, which can be reinforced by marked reductions in both biomass and metabolic activity of biofilms acting as antifungal agents. Thus, the results obtained from the composites were promising, with the materials used demonstrating in antifungal activity, allowing for the continuation of the structural characterization of the composites and future preclinical tests targeting on fungal infections.