A solvent-assisted active loading technology to prepare gambogic acid and all-trans retinoic acid co-encapsulated liposomes for synergistic anticancer therapy

Liposomal drug delivery has become an established technology platform to deliver dual drugs to produce synergistic effects and reduce the adverse effects of traditional chemotherapy. Gambogic acid (GA) and retinoic acid (RA) are both effective anticancer components, but their low water-solubility (gambogic acid < 0.0050 mg/mL, retinoic acid 0.0048 < mg/mL) makes it difficult to load both drugs into the liposomes actively using the conventional method. We have successfully used solvent-assisted active loading technology (SALT) to load the insoluble drugs into the internal water phase via water-miscible organic solvent. Gambogic acid and retinoic acid co-encapsulated liposomes (weight ratio of GA to RA = 1:2, GRL) exhibited the strongest synergistic effect; combination index (CI) was 0.614 in 4T1 cells. Our studies demonstrated that GRL had uniform droplet size of about 130 nm, high stability, and controlled release behavior. GRL outperformed gambogic acid and retinoic acid solution (GRS) in pharmacokinetic profiles for a longer half-life and increased AUC. Comparing to GRS, GL, and RL, GRL showed increased cytotoxicity and apoptosis in 4T1 cells and showed the strongest anti-tumor ability in the in vivo anti-tumor efficacy. Overall, the SALT was a promising method to active loading poorly soluble drugs into liposomes, and the results showed GRL possessed a great potential for use in synergistic anticancer therapy.