Molecular dynamics and surfactant study for enhancing the formation and anti-oral cancer efficacy of D-limonene nanoemulsions.

Abstract

Objective: D-Limonene (D-LMN) is a potential anti-oral cancer agent. The incorporation of D-LMN into a nanoemulsion enhances its potential efficacy against oral cancer cells by improving its aqueous compatibility. This study evaluated the impact of surfactant type and concentration on their properties through experimental and molecular dynamics studies.

Methods: D-LMN nanoemulsions were produced using different polyoxyethylene nonionic surfactants. The nanoemulsions were compared on droplet size, size distribution, zeta potential, droplet morphology, stability, interaction among molecules, anticancer activity, and cell death mechanism. Molecular dynamics simulations were also conducted to elucidate the dynamics of the components.

Results: Cremophor RH40 and Tween 60 yielded a nanoemulsion with a small droplet size (<100 nm). Cremophor RH40 also produced the nanoemulsion with the narrowest size distribution. Two-dimensional nuclear Overhauser effect spectroscopy-nuclear magnetic resonance and molecular dynamic simulation studies revealed that Cremophor RH40 effectively produced nanoemulsions with small droplets and high stability. The nanoemulsions formulated with Tween 60 exhibited more potent inhibitory effects against oral cancer cells than those with Cremophor RH40. However, surfactant type did not influence the mechanism underlying the apoptotic.

Conclusions: This study demonstrated that surfactants with an intermediate hydrophilic-lipophilic balance of approximately 15, particularly those with large polar heads and multiple hydrocarbon chains, were suitable for the production of anti-oral cancer D-LMN nanoemulsions by phase-inversion temperature technique.