Purpose: We report on the design of hypoxia-induced dual-stage acting dendrimeric nanoparticles for selective delivery of two chemotherapeutic model drugs Doxorobicin (DOX) and Tirapazamin (TPZ) for deepened drug delivery into hypoxic tumors in vitro. Methods: PAMAM G5 dendrimers were crosslinked with a hypoxic azo linker, attached to a mPEG to form a detachable corona on the dendrimer surface (PAP NPs). NPs were characterized by Zeta sizer, TEM, FTIR and drug release kinetics. The anti-cancer performance of PAPs was evaluated by numerous tests in 2D and 3D cultured MDA-MB-231 breast cancer cells. Results: MTT assay showed a significant difference between PAP and PAMAMG5 in terms of biocompatibility, and the effect of PAP@DOX was significantly greater than free DOX in hypoxic conditions. The results of DAPI and Annexin V-FITC/PI cell staining also confirmed uniform drug penetration as validated by induction of 90% cell apoptosis in spheroids and a high level of PAP@DOX-induced ROS generation under hypoxia conditions. Mechanistically, PAP@DOX significantly reduced the expression of mTOR, and Notch1, while the expression of Bax and Caspase3 was considerably unregulated, compared to the controls. Importantly, hypoxia-responsive disintegration and hypoxia-induced activation of HAP drug were synergized to promote deep and homogenous HAP distribution in whole microtumor regions to efficiently eliminate residual tumor cells. Conclusion: Our results indicate the safety and high therapeutic potential of PAP system for targeted drug delivery of chemotherapeutics in particular HAPs which show maximum anti-cancer activity against hypoxic solid tumors.
