Preparation, characterization, and optimization of auraptene-loaded solid lipid nanoparticles as a natural anti-inflammatory agent: In vivo and in vitro evaluations.

Auraptene (AUR) is a bioactive antioxidant coumarin with valuable pharmacological properties; however, poor water solubility is a substantial issue for the topical application of AUR. Therefore, we sought to prepare solid lipid nanoparticles (SLNs) containing AUR (AUR-SLNs) to enhance its anti-inflammatory effect. The prepared formulations were optimized by applying the response surface method. Furthermore, AUR-SLNs were compared to conventional cream containing AUR regarding both the permeation rate of the nanoparticles and the anti-inflammatory effect through both in vitro and in vivo studies. Particle size and entrapment efficiency of the optimized formulation were 140.9 ± 3.55 nm and 84.11% ± 3.30, respectively. Transmission electron microscopy revealed that the nanoparticles were spherical. Differential scanning calorimetry (DSC) analysis demonstrated no drug-lipid incompatibility in the formulation. Fourier transform-infrared spectroscopy (FTIR) spectra revealed the amorphous state of AUR and the encapsulation of this agent in SLNs. The in vitro permeation studies exhibited that AUR-SLNs could significantly enhance cutaneous uptake of AUR and skin targeting. The anti-inflammatory and histopathological studies exhibited no significant differences between AUR-SLNs and indomethacin. AUR-SLNs did not induce skin sensitization in guinea pigs. The results suggest that SLNs could be appropriate carriers for the topical application of AUR as a natural anti-inflammatory agent.