Development of andrographolide-loaded solid lipid nanoparticles for lymphatic targeting: Formulation, optimization, characterization, in vitro, and in vivo evaluation.

Andrographolide, the primary bioactive constituent of Andrographis paniculata, is a promising natural substance with numerous pharmacotherapy uses. Low water solubility, short half-life, and low permeability necessitate the development of a delivery system that enhances its entrapment efficiency, bioavailability, lymphatic targeting, and by-pass hepatic effect. The andrographolide-loaded solid lipid nanoparticles were fabricated by melt-emulsification and ultrasonication and optimized with Design-Expert software. In the optimal formulation, Glycerol monostearate as the solid lipid and Poloxamer 407 and Span 60 as surfactants were used. Optimum AND-SLN was observed to have a mean particle size, polydispersity index, zeta potential, and entrapment efficiency of 193.84 nm, 0.211, - 22.8 mV, and 83.70% respectively. An optimized formulation was characterized by examining surface morphology, X-ray diffraction, and differential scanning calorimetry. In vitro studies have shown sustained drug release from AND-SLN for up to 24 h. The stability studies showed that there was no significant change in the mean particle size and entrapment efficiency after storage at 4 ± 2 °C and 25 ± 2 °C/60 ± 5% RH. In in vivo pharmacokinetics studies, AND-SLN was found to have enhanced bioavailability and specificity in the spleen and thymus compared to plasma, providing evidence that the formulations could enhance target specificity and bioavailability in comparison to pure drugs. The H&E staining of the liver, spleen, and thymus treated with the AND-SLN revealed no signs of damage histopathologically. Thus, AND-SLN possess a high potential for improved efficacy and are an efficient vehicle for delivering drugs to the lymphatic system.