Repurposing Lovastatin Cytotoxicity against the Tongue Carcinoma HSC3 Cell Line Using a Eucalyptus Oil-Based Nanoemulgel Carrier

Abstract

Tongue cancer is one of the most common carcinomas of the head and neck region. The antitumor activities of statins, including lovastatin (LV), and the essential oil of eucalyptus (Eu oil), have been adequately reported. The aim of this study was to develop a nanoemulgel containing LV combined with Eu oil that could then be made into a nanoemulsion and assessed to determine its cytotoxicity against the cell line human chondrosarcoma-3 (HSC3) of carcinoma of the tongue. An I-optimal coordinate-exchange quadratic mixture design was adopted to optimize the investigated nanoemulsions. The droplet size and stability index of the developed formulations were measured to show characteristics of the nanoemulsions. The optimized LV loaded self-nanoemulsifying drug delivery system (LV-Eu-SNEDDS) was loaded into the gelling agent Carbopol 934 to develop the nanoemulgel and evaluated for its rheological properties. The cytotoxic efficiency of the optimized LV-Eu-SNEDDS loaded nanoemulgel was tested for cell viability, and the caspase-3 enzyme test was used against the HSC3 cell line of squamous carcinoma of the tongue. The optimized nanoemulsion had a droplet size of 85 nm and a stability index of 93%. The manufactured nanoemulgel loaded with the optimum LV-Eu-SNEDDS exhibited pseudoplastic flow with thixotropic behavior. The developed optimum LV-Eu-SNEDDS-loaded nanoemulgel had the best half-maximal inhibitory concentration (IC₅₀) and caspase-3 enzyme values of the formulations developed for this study, and these features improved the ability of the nanoemulsion-loaded gel to deliver the drug to the investigated target cells. In addition, the in vitro cell viability studies revealed the synergistic effect between LV and Eu oil in the treatment of tongue cancer. These findings illustrated that the LV-Eu-SNEDDS-loaded gel formulation could be beneficial in the local treatment of tongue cancer.

Keywords: essential oils; experimental design; nanosized delivery systems; statins; tongue cancer.

Figure 1

Solubility of LV in different oil phases, surfactants, and co-surfactants.

Figure 2

The pseudoternary-phase diagram of Eu oil/Maisine mixture, surfactant (TPGS), and co-surfactant (propylene glycol).

Figure 3

Statistical design plots for the droplet size and stability index of LV-Eu-SNEDDS: (A) contour plot for droplet size, (B) response surface plot for droplet size, (C) contour plot for stability index, and (D) response surface plot for stability index.

Figure 4

Bar chart and desirability ramp for optimization process. The desirability ramp illustrates the levels of studied factors and expected values for the dependent variables of the optimized LV-Eu-SNEDDS (A). The bar chart illustrates the values of desirability for the conjugated responses (B).

Figure 5

Plots of the shear rate (G) versus the viscosity (η) for (A) nanoemulgel loaded with optimized LV-Eu-SNEDDS and (B) Carbopol 934 hydrogel (plain). Values are expressed as the mean ± SD (n = 3).

Figure 6

Rheograms of (A) nanoemulgel loaded with optimized LV-Eu-SNEDDS and (B) Carbopol 934 hydrogel (plain).

Figure 7

Plots of the logarithm of the shear rate (G) versus the logarithm of the shear stress (F) for (A) nanoemulgel loaded with optimized LV-Eu-SNEDDS and (B) Carbopol 934 hydrogel (plain). Values are expressed as the mean ± SD (n = 3).

Figure 8

SEM for the optimized nanoemulgel loaded with the optimized LV-Eu-SNEDDS.

Figure 9

In vitro release profiles of LV from different formulations.

Figure 10

Effect of different LV formulations and 5-fluorouracil (control) on the viability of the HSC3 cell line. The values represent the mean ± SD of three independent experiments (n = 9).

Figure 11

Caspase-3 enzyme concentrations in HSC3 cells treated with different formulations; data are presented as the mean ± SD (n = 6). Results were statistically tested using the one-way ANOVA followed by the post-hoc Tukey HSD test.