Preparação e caracterização de filmes de látex de borracha natural contendo própolis vermelha e cobre para aplicações biomédicas

Abstract

Wound healing can be delayed due to resistance and tolerance to several topical antimicrobials that are often used for this purpose. In this context, the development of dressings with materials that have angiogenic and bactericidal properties is desirable, since they make it possible to treat such infections for a long period of time and locally. In this study, natural rubber latex (NRL) films containing red propolis and copper (II) oxide/copper (II) oxide nanoparticles (CuO/CuONPs) were prepared. The films were obtained under different conditions of temperature and time (65 ºC for 24 h, 40 ºC for 24 h, 40 ºC for 12 h with forced air circulation, and at room temperature). Additional surface treatments with plasma, using oxygen, hydrogen and a mixture of both gases, in addition to copper deposition using the magnetron sputtering technique, were also performed. The films were then characterized by the techniques of infrared spectroscopy with Fourier transform and attenuated total reflectance (FTIR-ATR), scanning electron microscopy with field emission (FEG-SEM), energy dispersion spectroscopy (EDS) and X-ray fluorescence (XRF), and by contact angle measurements. The release of copper from the films was evaluated using the inductively coupled plasma optical emission spectrometry (ICP-OES) technique, while antibacterial assays were performed with inoculum of Escherichia coli. In general, the films showed a hydrophilic character, with contact angle values between 22º and 65º; however, in the course of time and due to the aging of the NRL, they become more hydrophobic. In addition, the results obtained from the films that were prepared through the direct incorporation of CuO/CuONPs into the latex indicated the absence of bactericidal activity, since copper reacts with the polymeric matrix, promoting their disintegration over time and, consequently, making it impossible to visualize it by FEG-SEM and EDS. On the other hand, the results inherent to the films prepared by magnetron sputtering revealed that the way of conditioning directly influences the bactericidal activity. The films preserved in a desiccator showed bacteriostatic properties after 10 s of copper deposition, while those that remained under the bench showed less bacteriostatic activity due to the formation of oxides. The analysis using FEG-SEM and EDS techniques demonstrated that the amount of copper on the surface of the samples and the increase in the contact angle are directly linked to the time of copper deposition. The copper release result was 0.16 mg/L, below the standard limit for wastewater release. Finally, the set of all results indicated that NRL/red propolis/copper films can be considered an alternative to traditional wound dressings; however, deeper studies, mainly of a biological nature, such as cytotoxicity and the improvement of the hydrophilicity of the films are still necessary. [resumo fornecido pelo autor]