Purpose: Cutaneous malignant melanoma is regarded as the fifth and sixth most common cancer in men and women respectively in the U.S. The treatment of melanoma continues to be a challenging issue due to the limitations of available treatments. Therefore, there is an urgent need of novel drug approaches. Poorly soluble drugs mostly natural polyphenols such as curcumin (Cur), resveratrol(Res), and quercetin (Que) have shown significant benefits in the treatment of melanoma because of their diverse pharmacological properties. The purpose of this study is to formulate, characterize and carry out skin binding study of Cur-Res and Cur-Que solid lipid nanoparticles as the first step to develop transdermal nanoparticulate formulations for prevention and treatment of melanoma.
Methods: Solid lipid nanoparticles (SLN) were formulated using curcumin (Cur), quercetin (Que) and resveratrol (Res) as model drugs with three different ratios of Cur-Que (C 0.075: Q 0.025, C 0.05: Q 0.05, C 0.025: Q 0.075, w/v %) and Cur-Res (C 0.075: R 0.025, C 0.05: R 0.05, C 0.025: R 0.075, w/v %). Gelucire 50/13 (G50/13), and Compritol 888 ATO (C888) were used as solid lipids with Poloxamer 188(P188) and Tween 80 (Tw 80) being used as surfactant and co-surfactant. All samples were freeze-dried and characterized using X-ray powder Diffractometry (XRPD) and scanning electron microscopy (SEM) (n=3). For stability assessment, prepared nanoparticles were stirred at 37 °C for 24 hours, and particle size of formulations was measured. To study the amount of drug bound to skin, 1 mL of Cur-Res-SLN (C 0.025: R 0.075, w/v %) and Cur-Que-SLN (C 0.075: Q 0.025, w/v %) were mixed with pulverized snake skin. After 24 h incubation at 37 °C, the mediums were centrifuged. The amount of drug that bound to snake skin was measured by subtracting the amount of drug present in the supernatant from the amount of drug originally added.
Results: Among all the formulations tested, compritol-based formulations were optimum in terms of their particle size whereas Gelucire 50/13-based formulations showed higher particle size. After probe sonication, Cur-Que loaded SLN displayed averaged particle size ranging from 130 to 200 nm (Figure 1) and Cur-Res SLNs have shown slightly increased particle size ranging from 170 to 250 nm. Among all the ratios tested of Cur-Que and Cur-Res, the lowest particle size was respectively observed in C 0.075: Q 0.025, w/v % SLNs (138±25 nm) and C 0.025: R 0.075, w/v% SLN (177 ±60 nm). The largest particle size was detected in C 0.025: Q 0.075, w/v % SLNs and C 0.05: R 0.05, w/v % SLNs accounts for 200±21 and 244±55 nm respectively. However, the particle size of the compritol-based formulations significantly increased after freeze drying. The XPRD results showed a unique diffraction pattern consisting of three crystalline peaks at a 2Ө of 19.7, 21.8 and 23.6. These peaks do not correlate with any drug/excipients that are utilized in the formulation and can be due to the formation of unique rearrangement between lipid, surfactant and drugs. SEM showed irregular and porous morphology for all the freeze-dried formulations. All the SLNs were found to be stable as they have shown almost non-significant alterations in particle size after 24 h. However, G50/13-based formulations exhibited higher particle size (> 1000 nm) and the particle size significantly increased after 24 h. Cur-Res SLNs showed 70% and 75% binding for Cur and Res respectively whereas Cur-Que SLNs have 90% and 55% binding of Cur and Que respectively. A significant amount of drug got bound to the skin, indicating that these SLNs are ideal systems for transdermal administration of Cur, Que, and Res and their combinations.
Conclusion: Cur-Que and Cur-Res loaded compritol-based solid lipid nanoparticles with high skin binding were successfully formulated and characterized. These formulations will be utilized for in-vitro and in-vivo testing against melanoma.