Multi-functional purine nucleoside-modified chitosan polymer micelles for improving the oral absorption of doxorubicin based on nucleoside transporter mediation

A kind of purine nucleoside-chitosan-silybin (PN-CS-SB) polymeric micelles were developed for enhancing the oral absorption of doxorubicin (DOX) by intestinal nucleoside transporter mediation, the inhibition of P-glycoprotein (P-gp) efflux and CYP3A4 metabolism. The four types of PN, including adenosine, deoxyadenosine, guanosine and deoxyguanosine, respectively, and silybin, were conjugated to chitosan via the linker succinic acid. The synthesized PN-CS-SB were identified by ¹H NMR and FT-IR, and the doxorubicin (DOX)-loaded micelles were prepared by ultrasonication. The micelles demonstrated a series of the excellent properties, including the high drug loading capacity of above 8.2%, the regular spherical shapes with the small particle sizes of below 150 nm, and the low critical micelle concentration of below 5.82 × 10⁻⁶ g/mL. The oral bioavailability of the DOX-loaded micelles against DOX solution achieved to as high as 453.28%. The rapid and tremendous absorption of micelles was visually demonstrated by in vivo imaging. The micelle absorption mechanism was proved to be nucleoside transporter-mediation as well as the dual inhibition of P-gp and CYP3A4 by the cellular uptake, enzyme inhibition and immunofluorescence location test. The cellular endocytosis and transportation pathway of micelles across intestinal epithelial cells involved nucleoside transporter target, caveolin mediation or macropinocytosis with energy consumption.