Physical Characterization of Halofantrine-Encapsulated Fat Nanoemulsions

Abstract

We report the colloidal characterisation of halofantrine (Hf) laden soybean oil (SBO) fat emulsions. Hf increased the zeta potential, at all pH values, of the fat emulsions. Concomitant with this, the isoelectric point (i.e.p.) of the emulsion increased to higher pH values. The emulsion was destabilised by a small amount of Hf; interestingly, however, this was ameliorated by increasing the amount of Hf. The particle size and polydispersity of the fat emulsion reflected this with a small Hf concentration resulting in a significant increase in both particle size and polydispersity, but less so as the Hf concentration was increased. Emulsions lost stability as the pH approached the i.e.p. and this effect was greatest for the small Hf concentration emulsions. Cryogenic transmission electron microscopy showed the presence of beading or string like behaviour leading to gross distortions of the spherical shape for highly unstable emulsions. We conclude that to maintain good stability for Hf laden SBO emulsions, the pH of the emulsion should be kept away from its isoelectric point, and also that the drug concentration should be maintained at a relatively high value.