Intravesical Mucoadhesive Hydrogel Induces Chemoresistant Bladder Cancer Ferroptosis through Delivering Iron Oxide Nanoparticles in a Three-Tier Strategy

Bladder cancer (BCa) is the most costly solid tumor owing to its high recurrence. Relapsed cancer is known to acquire chemoresistant features after standard intravesical chemotherapy. This cancer state is vulnerable to ferroptosis, which occurs when lipid peroxides generated by iron metabolism accumulate to lethal levels. Increasing the labile iron pool (LIP) by iron oxide nanoparticles (IONPs) promises to inhibit chemoresistant BCa (CRBCa), but systemically administered IONPs do not sufficiently accumulate at the tumor site. Therefore, their efficacy is weakened. Here, we present a three-tier delivery strategy through a mucoadhesive hydrogel platform conveying hyaluronic acid-coated IONPs (IONP-HA). When instilled, the hydrogel platform first adhered to the interface of the tumor surface, sustainably releasing IONP-HA. Subsequently, the tumor stiffness and interstitial fluid pressure were reduced by photothermal therapy, promoting IONP-HA diffusion into the deep cancer tissue. As CRBCa expressed high levels of CD44, the last delivery tier was achieved through antibody-mediated endocytosis to increase the LIP, ultimately inducing ferroptosis. This three-tiered strategy delivered the IONPs stepwise from anatomical to cellular levels and increased the iron content by up to 50-fold from that of systematic administration, which presents a potential regimen for CRBCa.