Overcoming clofazimine intrinsic toxicity: statistical modelling and characterization of solid lipid nanoparticles

The aim of this work was to develop solid lipid nanoparticles (SLNs) loaded with clofazimine (CLZ) (SLNs-CLZ) to overcome its intrinsic toxicity and low water solubility, for oral drug delivery. A Box-Behnken design was constructed to unravel the relations between the independent variables in the selected responses. The optimized SLNs-CLZ exhibited the following properties: particle size ca 230 nm, zeta potential of -34.28 mV, association efficiency of 72% and drug loading of 2.4%, which are suitable for oral delivery. Further characterization included Fourier transformed infrared spectroscopy that confirmed the presence of the drug and the absence of chemical interactions. By differential scanning calorimetry was verified the amorphous state of CLZ. The storage stability studies ensured the stability of the systems over a period of 12 weeks at 4°C. In vitro cytotoxicity studies evidenced no effect of both drug-loaded and unloaded SLNs on MKN-28 gastric cells and on intestinal cells, namely Caco-2 and HT29-MTX cells up to 25 µg ml^-1 in CLZ. Free CLZ solutions exhibited IC₅₀ values of 16 and 20 µg ml^-1 for Caco-2 and HT29-MTX cells, respectively. It can be concluded that the optimized system, designed considering important variables for the formulation of poorly soluble drugs, represents a promising platform for oral CLZ delivery.