Polymeric and emulsion carriers—interaction with antiflocculants and ionic surfactants

Abstract

A factor determining the physical stability of polymeric and fat emulsion drug carriers is the electrostatic repulsion of the particles/droplets. An increased repulsion (and subsequently increased stability) was achieved by the addition of antiflocculants to suspensions of polystyrene latex particles used as model carriers. Sodium citrate and sodium pyrophosphate proved to be most efficient by increasing the zeta potential to about −100 mV. This effect was less distinct with emulsions and was overlapped by a simultaneous zeta potential increase due to pH shifts. Eliminating the pH effect, sodium pyrophosphate could still enhance the net zeta potential of fat emulsions by −38 mV compared to −65 mV on polymeric particles. Antiflocculants could thus be selected with similar strong charge enhancing effects as ionic surfactants [sodium dodecyl sulphate, cetyl pyridinium chloride] but with a higher lexicological acceptance.