Formulation Characteristics of Solid-Dispersible Self-Emulsifying Drug Delivery Systems for Dual Drug Delivery

Background: Oral delivery of chemotherapeutic agents remains challenging due to gastrointestinal degradation, poor intestinal permeability, and extensive first-pass metabolism, which collectively limit bioavailability. Lipid-based drug delivery systems offer a promising strategy to overcome these barriers. This study aimed to develop a freeze-dried, solid-dispersible self-emulsifying drug delivery system (SEDDS) using a water-in-oil-in-water (w/o/w) double emulsion approach for the co-encapsulation of hydrophilic (doxorubicin) and lipophilic (ellipticine) agents to enhance oral delivery. Methods: Double-emulsion SEDDS were prepared via a two-stage emulsification process to enable compartmentalized drug loading within aqueous and oil phases. The formulations were freeze-dried to improve stability and storage. Physicochemical properties were characterized using dynamic light scattering for droplet size and polydispersity index (PDI), zeta potential analysis for colloidal stability, and differential scanning calorimetry for thermal behavior. Drug encapsulation efficiency was determined, and cellular uptake was evaluated in breast cancer cells using fluorescence microscopy. Results: Optimized SEDDS exhibited droplet sizes of 90–347 nm with low PDI values (0.005–0.336), indicating uniform and stable dispersions. Zeta potential values (−10.64 to 2.38 mV) supported colloidal stability, while freeze-dried formulations retained dispersion characteristics upon reconstitution over extended storage. Both drugs demonstrated high encapsulation efficiency (>97%), and thermal analysis confirmed the formation of stable amorphous systems. Fluorescence imaging revealed enhanced intracellular uptake of both agents. Conclusions: This study demonstrates that freeze-dried double-emulsion SEDDS enable efficient co-delivery of hydrophilic and lipophilic drugs, improving stability and cellular uptake. This platform shows strong potential for overcoming key barriers in oral chemotherapy and provides a promising strategy for combination drug delivery.