Synthesis of PMMA Nanoparticles Loaded with Geopropolis Extract from the Brazilian Stingless Bee Melipona quadrifasciata Lepeletier , 1836 by Miniemulsion Polymerization

The present work aims to encapsulate the concentrated geopropolis extract from the Brazilian stingless bee Melipona quadrifasciata quadrifasciata Lepeletier, 1836 in poly(methyl methacrylate) (PMMA) nanoparticles produced by miniemulsion polymerization. The concentrated geopropolis extract is obtained by hydroalcoholic maceration and characterized by ultraviolet-visible spectrophotometry (UV-Vis) to quantify flavonoids and polyphenols in terms of quercetin (Q) and galic acid (GA), respectively. The PMMA-Propolis nanoparticles is characterized by size exclusion chromatography (SEC), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), UV-Vis and nuclear magnetic resonance (NMR1H). UV-Vis results of the geopropolis extract revealed an average flavonoid content of 22.51 mg Q g(-1) and an average polyphenol content of 10.15 mg GA g(-1). TEM images showed that the produced PMMA nanoparticles are spherical, and their average diameter reduced from 72.62 to 44.60 nm by increasing the propolis concentration from 0% to 40%. Additionally, the kinetic data reveal a reduction of the polymerization reaction rate as well as the average molecular weight when raising the propolis extract concentration in the reaction media. These results suggest that propolis extract may be used as a biocompatible and biodegradable co-stabilizer and chain transfer agent in miniemulsion polymerization reactions of vinyl monomers.