Sistemas de base nanotecnológica contendo disseleneto de difenila para o tratamento do melanoma e do glioma

Abstract

Cancer is one of the diseases with the highest mortality in Brazil and worldwide. In addition, the conventional therapies present low efficacy and high toxicity. In this context, the diphenyl diselenide [(PhSe)2], an organoselenium compound, has been investigated in view of its promising pharmacological properties, including the anti-tumoral effect. However, such molecule has some physicochemical (lipophilic) and toxicological issues, which limit its clinical application. The development of a nanocapsules formulation could be an interesting approach to overcome such restrictions and potentiates its pharmacological effects. Considering the aforementioned context, the current study aimed to develop a (PhSe)2-loaded poly-Ɛ-caprolactone nanocapsules (NC (PhSe)2) (5 mg/mL) formulation as well as to investigate the potential cytotoxicity against melanoma and glioma cell lines, which are both highly aggressive and prevalent cancers. The formulations were prepared by the interfacial deposition of preformed polymer method. A detailed physicochemical characterization was performed using the following parameters: average particle size, polydispersity index (PDI), zeta potential, pH, compound content, encapsulation efficiency, morphology, thermal behavior (thermogravimetric analysis and differential scanning calorimetry), X-ray diffractrometry and fourier-transform infrared spectroscopy. Stability studies were also carried out using a photodegradation assay and monitoring the formulations over a 30-day storage period. The obtained nanocapsules suspension had suitable physicochemical properties as well as adequate compatibility with the constituents and increased the compound stability. Different in vitro techniques (MTT assay, propidium iodide uptake and nitric oxide content) were applied to investigate the cytotoxic potential of the NC (PhSe)2 against human melanoma cells lines (A375 and SK-Mel-103), rat glioma cells lines (C6) and healthy cells (human red blood cells and keratinocytes and rat astrocytes). Overall, the results demonstrated that the nanoencapsulation provided selective and superior cytotoxic effect against the tumoral cells in comparison to the free compound, which was also toxic to keratinocytes. The NC (PhSe)2 caused an increase in the nitrite content to both SK-Mel-103 and C6 cells, suggesting that the oxide nitric mediated pathways could be associated with the cytotoxic potential of the formulation. Following, in order to develop an alternative adjuvant therapy to melanoma treatment, a hydrogel formulation was developed. A mortar and pestle were used to prepare the hydrogels by thickening the nanocapsules suspension or a solution of free compound, both at a final (PhSe)2 concentration 5mg/g. Such formulations were characterized concerning average particle size, polydispersity index (PDI), pH, compound content, physicochemical stability, spreadability assessment, rheological behavior and cutaneous permeation profile (human skin). Both formulations had compatible characteristics intending cutaneous application and the nano-based hydrogel provided superior permeation of (PhSe)2 to dermis layer in comparison to the free compound formulation. Regarding the toxicological potential of the nanostructured formulation, two different protocols were carried out to better understand such characteristic. The fist protocol evaluated the nanocapsules formulation effect in a Zebra-fish model by assessing many behavioral parameters; the second one was performed using a repeated administration schedule by the intragastric route in male adult Wistar rats (5 mg/Kg – 1 mL/Kg, once a day, during 15 days) in which theplasma biochemical markers of liver and kidney function as well as the oxidative status of different organs (brain, liver and kidney) were evaluated. The exposure of Zebra-fish to NC (PhSe)2 did not trigger behavioral impairments or oxidative stress-related injuries in the samples of rats that received the repeated treatment. Finally, a preclinical model of glioblastoma multiforme was carried out. Male adult Wistar rats received an injection of C6 cells in the right striatum (1 x 106 cells/3 μL) for tumor developing. Five days after glioma implantation the animals were treated with free compound or NC (PhSe)2 for 15 days (1 mg/Kg- 1 mL/Kg/once a day) by the intragastric route. At the end of the experiment, the groups that received the compound, free or nanoencapsulated, had a reduction in tumor size in comparison to the vehicle-treated groups. Therefore, as a conclusion, the results obtained herein showed the great biological potential of nanocapsule formulations containing (PhSe)2 intending selective anti-tumoral effect.