Multiple nanoemulsion system for an oral combinational delivery of oxaliplatin and 5-fluorouracil: preparation and in vivo evaluation

Oxaliplatin (OXA) is a third-generation cisplatin analog that has been approved as first-line chemotherapy in combination with 5-fluorouracil (5-FU) for the treatment of resectable and advanced colorectal cancer. However, the therapeutic efficacy of oral OXA and 5-FU is limited by their low bioavailability due to poor membrane permeability. The aim of the present study was to develop an oral delivery system for OXA and 5-FU. We constructed an ion-pairing complex of OXA with a deoxycholic acid derivative (Nα-deoxycholyl-l-lysyl-methylester, DCK) (OXA/DCK) as a permeation enhancer. Next, we prepared multiple water-in-oil-in-water nanoemulsions incorporating OXA/DCK and 5-FU to enhance their oral absorption. To evaluate their membrane permeability, we assessed in vitro permeabilities of OXA/DCK and 5-FU through an artificial intestinal membrane and Caco-2 cell monolayer. Finally, oral bioavailability in rats and tumor growth inhibition in the colorectal adenocarcinoma cell (CT26)-bearing mouse model were investigated after oral administration of nanoemulsion containing OXA/DCK and 5-FU. The droplet size of the optimized nanoemulsion was 20.3±0.22 nm with a zeta potential of -4.65±1.68 mV. In vitro permeabilities of OXA/DCK and 5-FU from the nanoemulsion through a Caco-2 cell monolayer were 4.80- and 4.30-fold greater than those of OXA and 5-FU, respectively. The oral absorption of OXA/DCK and 5-FU from the nanoemulsion also increased significantly, and the resulting oral bioavailability values of OXA/DCK and 5-FU in the nanoemulsive system were 9.19- and 1.39-fold higher than those of free OXA and 5-FU, respectively. Furthermore, tumor growth in CT26 tumor-bearing mice given the oral OXA/DCK- and 5-FU-loaded nanoemulsion was maximally inhibited by 73.9%, 48.5%, and 38.1%, compared with tumor volumes in the control group and the oral OXA and 5-FU groups, respectively. These findings demonstrate the therapeutic potential of a nanoemulsion incorporating OXA/DCK and 5-FU as an oral combination therapy for colorectal cancer.