Tumor Microenvironment Responsive TPZ-Loaded Core-Shell Polymeric Nanoparticles for Selective Cancer Bioreductive...

Tumor hypoxia is a key barrier to successful delivery and activity of anti-cancer agents. To tackle this, we designed hypoxia-responsive Au-PEI-Azo-mPEG nanoparticles (NPs) denoted as APAP NPs for targeted delivery of hypoxia-activated prodrug (HAP), tirapazamine (TPZ) to hypoxic breast cancer cells.

AuNPs were first synthesized. And then, were coated with polyethylene imine (PEI) by EDC-NHS chemistry. To realize NP biocompatibility and self-activating potential, a hypoxia-cleavable mPEG-AZO linker shell was coupled to the Au-PEI core. The hypoxia-responsible behavior of nanoparticles was analyzed under 21% O₂ (normoxia) and 1% O₂ (hypoxia) condition in 2D cell culture as well as MDA-MB-231 and MCF-7 spheroids as reliable biomimetics of tumor hypoxia.

APAP NPs elicited comparable cytotoxicity upon MDA-MB-231 cancer cells lowering TPZ IC₅₀ to 7.46 µg/mL after 24 h. And were capable of enhanced ROS generation (P<0.001), and reduced mitochondrial membrane potential under hypoxia condition compared to the control (P<0.0001). Further, these NPs induced widespread apoptosis in both 2D and 3D cancer cell culture (P<0.0001), significantly reduced cell adhesion density (P<0.01), increased cell uptake by ~100 folds under hypoxia condition, and destroyed large MCF-7 spheroids by 72 h.

Together, APAP@TPZ as biocompatible, and multi-stage activating platforms afford deepened penetration of HAP to hypoxic tumor core, where PEG detachment and TPZ bioreduction into its active form promote selective and effective eradication of hypoxic breast cancer microtumors.