Stability and physicochemical characteristics of PLGA, PLGA:poloxamer and PLGA:poloxamine blend nanoparticles: A comparative study

The physicochemical properties of new nanoparticulate carrier systems, which have been previously used for the delivery of DNA plasmids, have been study in this work. The new nanostructures consist of a blend matrix formed by poly(lactic-coglicolic) acid (PLGA) copolymer and polyoxyethylene derivatives. Two types of blend formulations, PLGA:poloxamer and PLGA:poloxamine, and also pure PLGA nanoparticles have been analyzed and their surface properties compared. Electrophoretic mobility data reflected the differences on surface characteristics among the three formulations. PLGA nanoparticles behaved as typical system with weak acid groups on their surface. For the blend formulations, mobility data corroborated the difference between the two surfactants employed, this is, particles containing poloxamers present a more hydrophilic character than those containing poloxamines. Stability data showed that pure PLGA particles exhibit the expected behavior for lyophobic colloids. In contrast, the stability of the blend formulations is governed by a steric mechanism. At high concentrations of calcium ion in phosphate buffer, however, an anomalous stability behavior was observed. This was explained on the basis of the interaction of the polyethylene oxide (PEO) chains of the surfactant and the divalent cations, Ca2+, in presence of di-phosphate anion. In all the stability experiments both blend nanoparticles behaved identically, this has been ascribed to a considerable amount of surfactants on the surface of the particles.