Gold Nanourchins Potentiate Intravesical Chemotherapy by Accelerating Drug Internalization within a Short Instillation Window

Abstract Intravesical chemotherapy is a standard adjuvant treatment for nonmuscle-invasive bladder cancer after transurethral resection, but its efficacy is limited by drug exposure resulting from urinary dilution and physiological voiding. Most current delivery strategies aim to prolong the intravesical residence through mucoadhesion, depot formation, or sustained release. Although these approaches increase local drug availability, they do not directly address insufficient intracellular drug accumulation during the short instillation window. Here, we report a poly-l-glutamic acid-modified gold nanourchin platform, PGU3@DOX, designed to enhance intravesical chemotherapy by accelerating drug internalization by bladder cancer cells. By optimizing the nanoparticle morphology, we identified long-spiked gold nanourchins as the most effective architecture for rapid cellular uptake. The PLG coating enabled doxorubicin loading and supported pH-facilitated DOX release, while the internalized nanourchins induced lysosomal swelling and lysosomal membrane permeabilization in bladder cancer cells. Under a 1 h pulse exposure that mimics the short intravesical dwell-time window, PGU3@DOX showed greater cytotoxicity against bladder cancer cells after extracellular drug removal while showing lower toxicity toward normal urothelial cells. Furthermore, PGU3@DOX achieved a broader distribution and stronger damage in tumor spheroids than free DOX. In an orthotopic bladder cancer model, a single short-duration intravesical administration of PGU3@DOX significantly suppressed tumor progression without detectable acute hematological, hepatic, renal, or cardiac toxicity under the tested conditions. These findings support rapid cellular internalization as a complementary strategy to improve intravesical chemotherapy and provide a morphology-guided nanocarrier platform for enhancing drug delivery within short therapeutic exposure windows.