Síntese de nanopartículas à base de goma do cajueiro para aplicação em sistemas de liberação de fármacos

Abstract

Nanoparticles based on cashew gum were obtained by two rotes. In the first rote, nanoparticles of cashew gum were synthesized by a graft reaction with polyacrylamide (cashew gum-g-polyacrylamide), in the second one the gum was modified by reaction of the polysaccharide with propionic anhydride. The formation of the nanoparticle from the propionic polysaccharide derivative was made by selfassembly applying the dialysis process. Nanoparticles from the cashew gum-graftacrylamide were characterized by infrared spectroscopy (FT-IR), thermalgravimetric analysis (TGA) and particle size. Infrared spectroscopy confirms the graft of acrylamide onto polysaccharide structure and indicates that part of polyacrylamide has been hydrolyzed. TGA analysis of cashew gum-g-polyacrylamide shows five degradation events. This pattern is very different of the TGA curves from cashew gum and polyacrylamide where only two degradation events were observed, confirming the modification on the cashew gum structure. The change in gum/acrylamide/crosslinking agent ratio does not interfere on particle size. Nanoparticles with unimodal particle size distribution and average particle size of 8 nm were obtained. The particles have a negative surface; this was inferred by the negative zeta potential observed. The nanoparticle shows pH sensitive properties. Aggregation was observed after freeze-drying of nanoparticle suspension. Chloroquine a drug for malaria treatment was incorporated into the nanoparticles. The release of the drug shows to be pH dependent with a controlled released observed for 8 days been observed at pH 6.0. Modification of cashew gum with propionic anhydride was confirmed by FT-IR and 13C- nuclear magnetic resonance(NMR) spectroscopy and TGA analysis. A estimative of degree of substitution (DS) of propionate groups on cashew gum was calculate by 13C-NMR and found to be equal to 1.7. The formation of nanoparticle through dialysis process was made using acetone or DMSO as solvent for nanoparticles and H2O as a non-solvent. Unimodal particle size distribution was observed in both solvents. Particle size ranging from 42 to 142 nm were obtained their size were found to depend on solution concentration or solvent used in the dialysis process. Small particles were obtained using DMSO as solvent. Nanoparticles were shown to be stable for a storage time up to 120 days. Aggregation was also observed after freeze-drying of nanoparticle suspension.