Microwave-assisted synthesis of bioabsorbable nanoparticles to be used as reinforcement of PLGA in biomedical applications

G.J. Colmenares, M.E. Ramírez, I.C. Ortiz, L.M. Hoyos
Universidad Pontificia Bolivariana,
Colombia

Keywords: polymer, PLGA, reinforcement, hydroxyapatite, amorphous phosphate

Summary:

Biodegradable polymers have been used in a large number of mass production applications such as packaging, paper coating, fibers, films and other disposable items, as well as in biomedical applications (Kalia & Avérous, 2011). The physicochemical properties of these polymers depend on the monomers that compose it, in the proportions that it is found and the process by which it is synthesized, being that determines its final molecular weight and thanks to these depends on properties such as crystallinity, viscosity among others (D’Avila Carvalho Erbetta, 2012; Makadia & Siegel, 2011). However, the mechanical strength of these limits its use in some applications. On the other hand, there are few reports that are found in the literature on the reinforcement of bioabsorbable polymers (Haghshenas, 2017; Udupa & Upadhya, 2017). The present work seeks to show the effect of bioabsorbable nanoparticles such as hydroxyapatite and amorphous magnesium phosphates on the mechanical properties of a bioabsorbable polymer to develop a material 100% bioabsorbable but with mechanical properties superior to those available in the market, which can be used in the manufacture of different biomedical devices. For this work, hydrothermal synthesis assisted by microwave was used to obtain different bioabsorbable nanoparticles which were incorporated into the polymer Poly (L-lactide-co-glycolide) 85:15 (RESOMER LG 857 S, Evonik). To prepare the hydroxyapatite nanoparticles, two types of surfactants were evaluated. The first was CTAB and the second was Pluronic F-127 in different concentrations. Potassium phosphate and calcium nitrate solutions were used as precursors. The solutions were taken to a microwave for 30 minutes, the material obtained was washed to eliminate residues and subsequently calcined. To prepare the amorphous magnesium phosphate particles, a precursor solution of sodium bicarbonate, magnesium chloride, and potassium phosphate was used. For the preparation of amorphous calcium and magnesium phosphates the precursor solution was used sodium nitrate, calcium nitrate, magnesium nitrate, potassium phosphate and nitric acid. These solutions were subjected to 5 minutes of microwaves and subsequently washed and dried to obtain the phosphate particles. The mechanical properties of the polymer were studied using the technique of indentation by AFM and the calculation of the microhardness finding a significant increase of these properties.