Polymer-surfactant nanoparticles for improving oral bioavailability of doxorubicin

The oral bioavailability of several clinically relevant drugs is compromised because of their limited absorption across the gastrointestinal tract. Active efflux of the drug by transporters such as P-glycoprotein (P-gp) present on the luminal side of the intestinal epithelial cells limits drug absorption. Encapsulation of drugs in nanoparticles can reduce transporter-mediated efflux and increase drug absorption. The purpose of this manuscript is to determine if the bioavailability of doxorubicin, a P-gp substrate, could be increased by encapsulation in nanoparticles. We synthesized polymer-surfactant nanoparticles comprised of a sodium alginate core complexed with doxorubicin and stabilized by the surfactant Aerosol OT (AOT). Encapsulation of doxorubicin in nanoparticles improved its transport across cell monolayers as evidenced by Transwell^® studies. Drug uptake studies were carried out in cells overexpressing P-gp and those with basal levels of P-gp. These studies revealed that AOT inhibited P-gp activity and improved drug uptake in P-gp expressing cells by ~5-6-fold. Increase in drug uptake was found only in cells expressing P-gp and was limited to P-gp substrates. We also determined the in vivo oral bioavailability of the nanoparticle formulation of doxorubicin in mice. Doxorubicin delivered in the form of nanoparticles had a higher bioavailability relative to that with the free drug. This study shows that the oral bioavailability of P-gp substrates such as doxorubicin can be enhanced by delivering them in AOT-alginate nanoparticles.