Brazilian red propolis extract free and encapsulated into polymeric nanoparticles against ovarian cancer: formulation, characterisation and biological assays in 2D and 3D models.

Cancer incidence worldwide is alarming and among the cancers that affect women ovarian cancer is the most fatal. Many side effects are associated with conventional therapies and none of them are completely effective, so the development of new treatments is necessary. Brazilian red propolis extract is a natural product with complex composition and great potential for cancer treatment. However, its clinical application is harmed due to unfavourable physicochemical characteristics. To enable its application encapsulation in nanoparticles can be used. OBJECTIVES: The aims of this work were to develop polymeric nanoparticles with Brazilian red propolis extract and compare their action with the free extract against ovarian cancer cells. METHODS: Box Behnken design was used and nanoparticles were characterised using the techniques dynamic light scattering, nanoparticle tracking analysis, transmission electron microscopy, differential scanning calorimetry and encapsulation efficiency. Activity against OVCAR-3 was also tested on 2D and 3D models. KEY FINDINGS: Nanoparticles' sizes were ~200 nm with monomodal size distribution, negative zeta potential, spherical shape and with extract molecularly dispersed. Encapsulation efficiency was above 97% for the biomarkers chosen. Nanoparticles had greater efficacy in comparison with free propolis in OVCAR-3. CONCLUSIONS: So far, the nanoparticles here described have the potential to be a chemotherapy treatment in the future.

Comparative Analysis of 3D Bladder Tumor Spheroids Obtained by Forced Floating and Hanging Drop Methods for Drug Screening.

Introduction: Cell-based assays using three-dimensional (3D) cell cultures may reflect the antitumor activity of compounds more accurately, since these models reproduce the tumor microenvironment better. Methods: Here, we report a comparative analysis of cell behavior in the two most widely employed methods for 3D spheroid culture, forced floating (Ultra-low Attachment, ULA, plates), and hanging drop (HD) methods, using the RT4 human bladder cancer cell line as a model. The morphology parameters and growth/metabolism of the spheroids generated were first characterized, using four different cell-seeding concentrations (0.5, 1.25, 2.5, and 3.75 × 104 cells/mL), and then, subjected to drug resistance evaluation. Results: Both methods generated spheroids with a smooth surface and round shape in a spheroidization time of about 48 h, regardless of the cell-seeding concentration used. Reduced cell growth and metabolism was observed in 3D cultures compared to two-dimensional (2D) cultures. The optimal range of spheroid diameter (300-500 µm) was obtained using cultures initiated with 0.5 and 1.25 × 104 cells/mL for the ULA method and 2.5 and 3.75 × 104 cells/mL for the HD method. RT4 cells cultured under 3D conditions also exhibited a higher resistance to doxorubicin (IC50 of 1.00 and 0.83 µg/mL for the ULA and HD methods, respectively) compared to 2D cultures (IC50 ranging from 0.39 to 0.43). Conclusions: Comparing the results, we concluded that the forced floating method using ULA plates was considered more suitable and straightforward to generate RT4 spheroids for drug screening/cytotoxicity assays. The results presented here also contribute to the improvement in the standardization of the 3D cultures required for widespread application.