Superoxide Dismutase-Loaded Solid Lipid Nanoparticles Prepared by Cold Homogenization Method: Characterization and Permeation Study Through Burned Rat Skin

Superoxide dismutase (SOD), which inhibits lipid peroxidation and scavengers oxygen radicals, is an effective enzyme for treatment of skin ulcer lesion especially due to burns. Superoxide Dismutase is a hydrophilic compound with high molecular weight and low affinity for partitioning into skin. Moreover, another important limitation for its use in medicine is thermal denaturation and inactivation. We developed solid lipid nanoparticles (SLN) dispersions for enhancing superoxide dismutase penetration across burned rat skin and enzyme protection against environmental degradation. Solid lipid nanoparticles were prepared with cold homogenization method because SOD is a thermo sensitive compound. The characteristics of SLNs such as particle size, entrapment efficiency and enzyme release pattern and permeability through burned rat skin were evaluated. Solid lipid nanoparticles showed more than 90% entrapment efficiency and particle size lower than 102 nm. In vitro release study demonstrated SOD burst and sustained release characters in this manner with maximum of 65% of enzyme released after 48 hours. The SOD activity was measured and results indicated that SLN could protect activity of the enzyme. Differential scanning calorimetry of SLNs showed low crystalinity index percentage that is a reason for high entrapment efficiency and burst release character. The results indicated that SOD-loaded in SLN was delivered into deep burned skin layer and induced high enzyme activity through the skin. Low particle size, application of lecithin as surfactant and low crystallinity index (CI) percentage were important factors for increasing SOD penetration through the burned rat skin. Percentage of activity by SLN dispersions through rat skin was 13 folds more than the control.