Formulation, optimization and in vitro evaluation of nanostructured lipid carriers for topical delivery of apremilast

This work was aimed to formulate topical Apremilast loaded nanostructured lipid-carriers (NLCs) for the management of psoriasis. Psoriasis is a widespread skin condition considered to be a Th1 autoimmune skin disease and characterized by excessive growth and abnormal differentiation of keratinocytes. Objective of the study was to investigate the applicability of lipid matrix of NLC composed of solid lipid and liquid lipid (oil), creating imperfections in the crystal lattice, in improving drug loading as well as physical stability. NLCs were prepared by a cold homogenization technique using Compritol® 888ATO, oleic acid, Tween 80 and Span 20, and Transcutol P as a solid lipid, liquid lipid, surfactant mixture and penetration enhancer, respectively. Carbopol 940 was used to convert NLC dispersion into NLC based hydrogel to improve its viscosity for topical administration. The optimized formulation was characterized for size, polydispersity index, zeta potential, percentage entrapment efficiency (%EE), and surface morphology. Further, viscosity, spreadability, stability, in- vitro drug diffusion, ex-vivo skin permeation and skin deposition studies were carried out. Apremilast loaded NLCs showed narrow polydispersity index (PDI- 0.339) with particle size of 758 nm, %EE of 85.5% and zeta potential of -33.3 mV. Scanning electron microscopy confirmed spherical shape of NLCs. In vitro drug diffusion and ex vivo skin permeation results showed low drug diffusion and sustained drug release and 60.1% skin deposition. The present study confirms the potential of the nanostructured lipid form of poorly water-soluble drugs for topical application and increased drug deposition in the skin.