Green Nanoemulsions for Oral Drug Delivery: Formulation Strategies, Characterization, Therapeutic Applications, Challenges, and Future Perspectives

Green nanoemulsions have become a viable delivery method for enhancing the oral administration of naturally occurring bioactive substances and medications that are poorly soluble in water. While green techniques focus on renewable, biodegradable, and biocompatible materials as well as more sustainable production, conventional nanoemulsions tend to depend on synthetic surfactants, petroleum-derived excipients, organic solvents, and energy-intensive processing. Their wide interfacial area and small droplet size can enhance gastrointestinal behavior, drug solubilization, dispersion, and, for appropriate lipophilic drugs, systemic exposure. The basic concepts of green nanoemulsions, the selection of sustainable oils and emulsifiers, preparation techniques, important physicochemical characterization parameters, mechanisms of oral bioavailability enhancement, representative therapeutic applications, safety considerations, and Quality-by-Design approaches are all summarized in this review. The limited availability of natural raw materials, oxidative instability, surfactant-related issues, gastrointestinal changes, scale-up, reproducibility, regulatory ambiguity, and the paucity of relevant clinical evidence are all given special consideration. There is also discussion of emerging directions such as gut-nanoemulsion interactions, life-cycle evaluation, enhanced natural emulsifiers, continuous production, artificial intelligence-assisted formulation, and the integration of sustainability with pharmaceutical quality. Green nanoemulsions offer a lot of potential overall, but effective translation necessitates striking a balance between pharmacological performance, safety, reproducibility, manufacturability, clinical relevance, and observable environmental impact.