Redox responsive paclitaxel dimer for programmed drug release and selectively killing cancer cells.

Redox stimulus responsive drug delivery systems have been widely investigated and proved to be promising prospects for efficient cancer therapy due to the abnormal high level of reactive oxygen species and glutathione in tumor microenvironment. Herein, three paclitaxel dimers (named as PTX2-R, R = S, Se and Te) bridged with alkyl sulfide, selenide or telluride are synthesized. These dimers can self-assemble into stable uniform nanoparticles (named as PTX2-R NPs, R = S, Se and Te) with impressively high drug loading. As expected, sulfur/selenium/tellurium bonds exhibit different redox responsiveness, thereby affecting the drug release and cytotoxicity. Of note, tellurium bridged paclitaxel dimer shows ultra-sensitivity to hydrogen peroxide, which rapidly cleaves into two paclitaxel under the subsequent dithiothreitol stimulation. Our findings provide deep insight into the redox sensitivity of chalcogenide elements and offer the rational design strategies to biologically redox condition for programmed drug release.

Ultrafine PEG-PLA fibers loaded with both paclitaxel and doxorubicin hydrochloride and their in vitro cytotoxicity.

By means of "emulsion-electrospinning", both hydrophobic and hydrophilic drugs, paclitaxel (PTX) and doxorubicin hydrochloride (DOX), were successfully loaded into PEG-PLA nanofiber mats to realize multi-drug delivery. The release behaviors of both the drugs from the same fiber mats were ascribed to their solubility properties and distribution status in the fibers. Due to its high hydrophilicity, DOX was easy to diffuse out from the fibers, and its release rate was always faster than that of hydrophobic PTX. Moreover, the release rate of PTX was accelerated by DOX's release from the same drug-loaded fibers. In vitro cytotoxicity against rat Glioma C6 cells indicated that the dual drug combination showed a higher inhibition and apoptosis against C6 cells than a single drug-loaded system, which suggests the promise for multi-drug delivery on combination therapy.