A hypoxic microfluidic organoid-on-a-chip system for studying the efficacy of metronidazole-modified nanomaterials against cholangiocarcinoma established within the chip.

Cholangiocarcinoma (CCA) is a highly aggressive biliary malignancy characterized by a dismal prognosis. Tumor progression relies heavily on the hypoxic tumor microenvironment (TME), a key factor that promotes drug resistance and reduces therapeutic efficacy. A major barrier to clinical translation is that standard in vitro cultures fail to maintain this stable low-oxygen state. Addressing this limitation, we designed a microfluidic platform incorporating patient-derived CCA organoids (CCOs) to act as a high-fidelity tumor model. Moreover, we synthesized a hypoxia-activatable nanodrug, BM-MN@PDA (BMMNP). This agent consists of a metronidazole (MN)-loaded bismuth-TCPP framework shielded by a biocompatible polydopamine (PDA) coating. In a hypoxic environment, the drug generates cytotoxic radicals. Validation studies confirmed that our microfluidic platform successfully established a highly biomimetic hypoxic TME (O2 <2.5%), evidenced by the robust upregulation of HIF-1α and HIF-2α. Furthermore, BMMNP NPs demonstrated superior cellular uptake and potent cytotoxicity within the hypoxic CCOs. Notably, these nanoparticles effectively reversed hypoxia-induced resistance to gemcitabine, acting as a powerful chemosensitizer. Collectively, this platform not only establishes a physiologically relevant "hypoxia-on-a-chip" model for preclinical drug evaluation but also accelerates the optimization of nanoparticle-based strategies for hypoxia-targeted therapy.