Collisional solute release from thermally activated lipid particles.

Solid lipid particles were evaluated for their potential as a thermo-activated drug delivery system. Submicron-sized diphenylhexatriene (DPH)/myristyl alcohol particles were produced by an atomization/drying process and the release rate of DPH into sodium dodecyl sulfate (SDS) micellar solutions was measured. The results showed that the presence of micelles and thermal activation was necessary and sufficient for the release of DPH. The initial rate of DPH release was linear for most systems. However, nonlinearity was noted at low micelle concentrations where the rate decreased with time due to the loss of sink conditions with the rising concentration of DPH in the micellar solution. Also at high micelle and particle concentrations, the rate increased with time, which may be due to a loss of particle integrity. Analyzing the data from a design study, the release rate was found to be linearly proportional to particle concentration. In contrast, the rate of release increased with micelle concentration in a nonlinear manner and appeared to approach a plateau at high micelle concentrations. The decrease in rate as the micelle concentration increased is suggestive of a saturable process and may involve a collision-based mechanism.