Physicochemical Characterization of Parenteral Lipid Emulsion: Influence of Cosurfactants on Flocculation and Coalescence

Abstract

Purpose. The stability of lipid emulsions (LE) containing various cosurfactants (oleic acid, cholesterol, Tween 80, or HCO-60) was evaluated using the maximum total interaction energy, Vt^max, and the energy barrier for coalescence, W. Methods. The Vt^max and W were calculated from the ζ potential and the rate of increase in LE particle size, respectively. Results. The Vt^max and W of LE containing the oleic acid were 0.598 × 10⁻¹⁹ J and 3.03 × 10⁻¹⁹ J, respectively, while those of LE without the cosurfactant were 0.141 × 10⁻¹⁹ J and 1.36 × 10⁻¹⁹ J. Conclusions. These findings suggest that oleic acid prevents the flocculation and coalescence of LE. The Vt^max and W of LE containing the cholesterol were 0.435 × 10⁻¹⁹ J and 0.63 × 10⁻¹⁹ J, respectively, suggesting that the cholesterol prevents the flocculation of LE but does not affect the coalescence. Analysis of the stability of LE was performed by the separate considerations of the flocculation and coalescence.