Effect of Different Nail Penetration Enhancers in Solid Lipid Nanoparticles Containing Terbinafine Hydrochloride for Treatment of Onychomycosis

Onychomycosis is considered a stubborn nail fungal infection that does not respond to conventional topical antifungal treatments. This study aimed to develop and characterize novel solid lipid nanoparticles (SLNs) formulae containing terbinafine HCl (TFH) and loaded with different nail penetration enhancers (nPEs). Three (nPEs) N-acetyl-L-cysteine, thioglycolic acid, and thiourea were used. Characterization of the prepared formulae was done regarding particle size, zeta potential, polydispersity index (PDI), entrapment efficiency (EE%), physical stability, in vitro release study, infrared (FT-IR), and their morphological structures. The selected formulae and the marketed cream Lamifen (R) were compared in terms of their antifungal activity against Trichophyton rubrum as well as their nail hydration and their drug uptake by the nail clippers. Thiourea was the nPE of choice; formulae (N2 and N8), with thiourea, were considered the optimum TFH SLNs containing nPEs. They were selected for their optimum particle size of 426.3 +/- 10.18 and 450.8 +/- 11.45 nm as well as their highest EE% of 89.76 +/- 1.25 and 90.35 +/- 1.33, respectively. The in vitro microbiological screening of the antifungal activity of these two formulae showed significantly larger zones of inhibition in comparison with the marketed product. The ex vivo screening of the drug uptake of the two selected formulae was significantly higher than that of the marketed product. The nPE formulae present a very promising option as they showed optimum physicochemical characterization with high antifungal activity and high drug uptake as well as good nail hydration effect.