Design of lipid microparticle dispersions based on the physicochemical properties of the lipid and aqueous phase

Lipid microparticle (LMP) dispersions may be utilized as novel pharmaceutical dosage forms for different administration routes. The particle size and particle size distribution of the LMPs can be classified to the most crucial specifications for therapeutical and research applications. The size parameters can be adjusted via the physicochemical properties of the inner lipid and the outer aqueous phase. In the present study, ten different solid lipids with incorporated lecithin and four concentrations of the surfactant poloxamer 407 (P407) were utilized for LMP dispersion preparation. Physicochemical properties of the bulk and dispersed lipid matrices as well as features of the P407 solutions were determined. Correlations between the mean particle size (mean) of the LMPs and the span as parameter for the particle size distribution as responses were identified by plotting against the measured physicochemical parameters. Most significant linear correlations were found between the mean and the micellization onset temperature (Tmicell) in the parent solution and the dynamic viscosity of the emulsifier solution at 25 °C and between the span and the Tmicell in the LMP dispersion. Consequently, P407 micelles as a reservoir for surfactant monomers and the overall viscosity as a separator between newly-formed lipid droplets are fundamental stabilizing parameters.

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