Effect of glutamate on the electrical properties of cationic solid lipid nanoparticles containing stearylamine and dioctadecyldimethyl ammonium bromide

Electrical properties, including electrophoretic mobility, zeta potential, total surface charge density, and surface charge density resulting from primary amino groups, of cationic solid lipid nanoparticles (CSLNs) were investigated in the present study. Cationic lipids including stearylamine (SA) and dioctadecyldimethyl ammonium bromide (DODAB) were covered on the external cores of CSLNs. The influences of glutamate concentration in the medium, composition of cationic lipids, and surfactant species were especially analyzed. The results indicated that an increase in the mole ratio of SA in the cationic lipid caused an increase in the average diameter of CSLNs. Also, the average diameter of Span 20-stabilized CSLNs was larger than that of Tween 80-stabilized CSLNs. The electrostatic traits of CSLNs were reduced as the mole ratio of SA increased, and the electricity of Span 20-stabilized CSLNs was weaker than that of Tween 80-stabilized CSLNs. An increase in the glutamate concentration in the medium led to a decrease in electrophoretic mobility, zeta potential, and total surface charge density of CSLNs. As the glutamate concentration increased, surface charge density resulting from primary amino groups increased, and that from quaternary amino groups decreased as a result of the adsorption of negatively charged glutamate on CSLN surfaces. Ohshima's soft particle theory was adopted to describe the electrical behavior of CSLNs, and the deviations of zeta potential predicted by the Smoluchowski, Happel, and Kuwabara models were normally greater than 10%.