Preparação e caracterização de complexos polieletrolíticos a base de poli [(2-dimetilamino) etil metacrilato] e sulfato de condroitina

Abstract

This work reports the preparation of a novel polyelectrolyte complex (PEC) between poly [2-(dimethylamino)ethyl methacrylate] (PDMAEMA) and chondroitin sulfate (CS). The PDMAEMA was synthesized by radical polymerization from the monomers in THF and using AIBN as initiator. In order to investigate the best condition for preparing the complexes, a 22 factorial design was used for evaluating the effects of i) pH on preparation; and ii) PDMAEMA solution concentration, on amount of incorporated SC in each prepared complex. The only factor found to be statistically significant was the pH. Samples that gave the highest yields were the PEC2a and PEC3a, which were prepared at pH 1 and PDMAEMA concentrations of 1,9 and 2,5% (w/v), respectively. These complexes were characterized by WAXD, FTIR, TGA, SEM and DLS. The TGA results showed that the PECs have higher water content compared to the adsorbed precursor polymers and that the complexation modifies the crystalline structure of PDMAEMA. The SEM micrographs achieved indicated that the PEC3a sample showed porous and more compact surface than the PEC2a. This result was attributed to the higher proportion of PDMAEMA in PEC3a matrix. The antibacterial activities of the PDMAEMA and PEC3a and PEC2a complexes against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were evaluated. It was found that the polymer as well as the complexes showed no bactericidal activity. This result was associated to the low molar mass of PDMAEMA synthesized in this work. Moreover, by means of DLS measurements, it was found that the PEC2a and PEC3a complexes showed phase transition at pHs 6 and 7, in contradiction with the observed for PDMAEMA that showed such a transition at 52 oC as in aqueous solution at pH = 8. This was associated to the loose of PDMAEMA mobility as complexed with SC. The increase of pH caused a reduction in LCST of the complexes. This relationship was connected to the different ionization processes that can occur in groups of PDMAEMA and SC with the variation of pH. The thermo- and pHsensitive properties show that the PDMAEMA/SC complexes prepared in this work have great potential for applications in the pharmaceutical field. Release studies of SC from PEC3a confirmed this complex to possess specific ability for SC release in the colon. This PEC can release SC only whether in basic medium (pH = 8). In addition, the PEC3a proved to be thermo-responsive by temperature controlling for releasing to occur above or below the LCST. This characteristic may be better exploited in cancer treatment with hyperthermia