Inovação em emulsões: nanopartículas metálicas mediadas por Piper peltatum para aplicações biológicas

Abstract

Neglected tropical diseases remain closely associated with poverty, environmental vulnerability, and limited access to effective interventions, while dengue continues to be one of the main health challenges in tropical regions. Within this scenario, this dissertation investigated the feasibility of using an aqueous extract of Piper peltatum as a botanical platform for the green synthesis of silver nanoparticles (AgNPs), followed by incorporation of the active system into an oil-in-water (O/W) emulsion for biological use. The study comprised four axes: extract preparation and preliminary stability, qualitative phytochemical screening, factorial screening of AgNP synthesis conditions using an unreplicated 2³ design, and physicochemical as well as larvicidal evaluation of the formulated system. Phytochemical screening indicated the presence of flavonoids, alkaloids, and tannins/phenolics, which are compatible with a reducing and stabilizing matrix. UV-Vis monitoring suggested that the extract remained analytically stable for up to four days after preparation. During synthesis screening, absorbance after 2 h ranged from 0.3572 to 1.1845 a.u., with the pH 8 / 1.0% extract / 40 °C condition representing the most promising combination within the studied domain. Temperature showed the largest estimated effect, whereas the pH × extract concentration interaction also deserved attention. For formulation, the non-ionic base outperformed the anionic base. The selected emulsion showed pH values from 4.80 to 4.62, density of 0.97 g cm-3, and an apparent shear-thinning profile, indicating satisfactory preliminary physicochemical stability. However, larvicidal activity was not preserved after emulsification: AgNPs showed an LC50 of 43.49 µg mL-1, crude extract 48.62 µg mL-1, extract + AgNPs 64.29 µg mL-1, whereas the O/W emulsion caused no detectable mortality under the tested conditions. These results indicate that Piper peltatum is a promising regional platform for the green synthesis of AgNPs, but also show that formulation should be considered a critical transformation step rather than a neutral packaging stage. The main contribution of this dissertation lies in demonstrating that synthetic success and physicochemical stability do not necessarily translate into preserved biological performance.