Preparation of calcium chloride-loaded solid lipid particles and heat-triggered calcium ion release

CaCl₂-loaded solid lipid particles (SLPs) were prepared by a melt/emulsification/solidification method. CaCl₂ microparticles (1-5 μm) could be obtained in a mortar with aid of the dispersant (Tween 80/Span80 (35/65, w/w)) when the ratio of CaCl₂ to dispersant was 2 : 0.1 (w/w). SLP was prepared by dispersing 0.42 g of micronized CaCl₂ particles in 2 g of molten PBSA, emulsifying the mixture at 85 .deg. C in 40 ml of Tween 20 solution (0.5% w/v), and quenching the emulsion in an ice bath. The diameter of CaCl₂-loaded SLP was 10-150 μm. The unenveloped CaCl₂ could be removed by dialysis and the specific loading of CaCl₂ in SLP was 0.036mg/mg. An EDS spectrum of CaCl₂-loaded SLP, which was dialyzed, showed that the unenveloped CaCl₂ was completely removed. Any excipients (dispersant, Tween 20, CaCl₂) had little effect on the melting point of SLPs. No appreciable amount of Ca2+ was released in 20-50 .deg. C for 22 h. But the release degree at 60 .deg. C was significant (about 2.3%) during the same period. The matrix of the lipid particle was in a liquid state at 60 .deg. C, so CaCl₂ particles could move freely and contact the surrounding water, leading to the release. At 70 .deg. C, the release degree at a given time was a few times higher than that obtained at 60 .deg. C.