Scaffolds de PEMA, PMMA e PnBMA: processamento, caracterização e estudo para aplicação em sistemas de drug delivery

Abstract

In this master's project, the study of the interaction of poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA) e poly(n-butyl methacrylate) (PnBMA) polymers with curcumin was performed in two ways: casting film, that have been studied through their physico-chemical properties, and scaffolds processed via the salt leaching technique, that have been studied through curcumin release experiments, Drug Delivery models and morphological properties. It was found that in the first 7 hours the most relevant experimental points of the curcumin release curve are found. Although the Korsmeyer-Peppas model, in principle, presented a good fit for curcumin release curves for long times (> 140hs), for curucmin release experiments up to 7 hours the release kinetics is described by the First Order model. Curcumin release experiment from the scaffolds were performed at 36 °C and at 60 °C, which showed that for the release experiments at 60 °C occur an increase in the curcumin released compared with the release experiments at 36 °C. That increase in the release of curcumin from the scaffold at 60 °C varies depending on the scaffold polymer, with an influence of this polymer α relaxation temperature (Tα) in this effect. In the studies of physico-chemical properties as a function of the concentration of curcumin in solution and films (curucumin+methacrylates blends) were carried out through linear optical absorption (AOL) and photoluminescence (PL) experiments as a function of temperature and excitation energy. It was verified from the AOL and PL experiments the displacement of the spectra: (i) for red for higher concentrations caused by the formation of curcumin aggregates and (ii) for blue for lower concentrations (<10-4M) due to the effects of the solvent on the curcumin molecule, favoring the formation of enol-trans molecules. From the PL measurements as a function of the sample temperature, it was possible to identify the optically active electronic-vibrational modes are correlated to the phenylene rings of the curcumin molecule. Through Arrhenius-type graphs as a function of temperature for PL intensity, we observed that the polymethacrylate/curucumin interaction must be through the side branches of the polymers, probably through hydrogen bonds. It was also obtained, by temperature dependent PL experiment, the Huang-Rhys factors that showed that in general the electron-phonon coupling increases with the increase of curcumin concentration in the films. For the study of the morphological properties of the scaffolds, scanning electron microscopy (SEM) experiments were carried out. From the SEM images obtained it was possible to observe that the scaffolds studied did not undergo major changes in morphology before and after release experiments, regardless of the pH of the medium. This result indicates that the curcuminxi molecules released during the release experiments are those that are adsorbed on the walls of the scaffolds and not those absorbed in the polymeric matrix. Finally, the Dispersive Energy Spectroscopy (EDS) images showed that all the solvent used in the scaffold production process (chloroform) was eliminated after the heat treatment step in the salt leaching synthase route. With all these results obtained, it was possible to obtain an empirical model of how curcumin release occurs from the studied scaffolds.