Enzymatic degradation of SLN-effect of surfactant and surfactant mixtures.

Solid lipid nanoparticles (SLN) show different degradation velocities by the lipolytic enzyme pancreatic lipase as a function of their composition (lipid matrix, stabilizing surfactant). In combination with pancreatic colipase a degradation assay has been developed for studying the degradation behavior. As a measure to follow the degradation the formed free fatty acids have been analyzed using an enzymatic test. In the studies SLN degradation showed dependencies in relation to the length of the fatty acid chains in the triglycerides and the surfactants used for SLN production. The longer the fatty acid chains in the glycerides, the slower the degradation. The influence of surfactants can be degradation accelerating (e.g. cholic acid sodium salt) or a hindering, degradation slowing down effect due to steric stabilization (e.g. Poloxamer 407). As a second steric stabilizer, Tween 80 has been used and the results showed a less pronounced effect on hindering the degradation process than for Poloxamer 407. This result seems to be correlated to the number of ethyleneoxide chains in the molecule. The longer the ethyleneoxide chains are in the molecule, the more hindered is the anchoring of the lipase/colipase complex and consequently the degradation of the SLN. The result can be used to adjust degradation of SLN and consequently drug release in a controlled way.