Desenvolvimento e estudo da atividade antitumoral in vitro de nanopartículas poliméricas pH-sensíveis conjugadas com transferrina para liberação vetorizada de doxorrubicina

Abstract

Doxorubicin (DOX) is an anthracycline antibiotic widely used in cancer therapy, being effective against a number of tumors. However, its use may promote the development of multidrug resistance on tumor cells beside other adverse effects. Polymeric nanoparticles (NPs) stand out as an alternative to circumvent these limitations. Therefore, this work aimed to develop and evaluate poly(lactic-co-glycolic acid) (PLGA) NPs to vectorized DOX release. The versatility of this system allows the modification of its composition to obtain multifunctional NPs. Thus, the pH-sensitive behavior of the NPs was achieved by the incorporation of a surfactant derived from the amino acid lysine with sodium counterion (77KS), while the chemosensitizer ability was explored by the inclusion of poloxamer (DOX-PLGA-NPs). The transferrin (Tf) protein was conjugated to the NPs surface (Tf-DOX-PLGA-NPs) with the role to actively targeting them to the cancerous cells. The NPs displayed adequate physicochemical characteristics and the Tf conjugation rate was considered satisfactory, being proved by different methods. The characteristics of the NPs suspensions changed over the storage time; therefore, a lyophilized pharmaceutical form was proposed. The NPs promoted a control and pH-dependent in vitro drug release. In the hemolysis studies, performed in different pH values, it was showed the role of the 77KS to obtain pH-sensitive NPs and, consequently, to reach pHresponsiveness membranolytic activity, indicating the possible rupture of endosomes and DOX release in the cytoplasm. Both DOX-loaded and unloaded NPs exhibited great hemocompatibility and did not affect the coagulation system. Compared to DOX-PLGA-NPs and free DOX, the Tf-DOX-PLGA-NPs were more efficient to inhibit the proliferation of both sensitive and resistant cells, showing the synergistic activity of the modifiers 77KS, poloxamer and Tf. Cell uptake studies showed the effectiveness of Tf-modified NPs to internalize into the cells, proving the role of Tf as specific ligand and suggesting the targeted DOX delivery to cancer cell. Moreover, it was verified the higher Tf-DOX-PLGA-NPs intracellular retention, which can be attributed to the poloxamer ability to inhibit the activity of efflux pumps, as a mechanism to overcome MDR effect. The mechanisms underlying the cytotoxic response of the NPs indicated the involvement of the greater number of apoptotic events, accompanied by cell cycle arresting and reactive oxygen species generation, being these mechanisms more expressive for Tf-conjugated NPs. Cell internalization pathway studies revealed that receptormediated endocytosis and strong energy dependence were involved in the cellular uptake process of Tf-DOX-PLGA-NPs. From these results, it can be considered that the functionalization promoted in the polymeric NPs were effective to obtain a targeted DOX delivery system, able to overcome the MDR effect and potentialize its antineoplastic activity.