Ultrasound-Triggered Charge-Reversal Nanoparticles via Golgi-Dependent Iterative Transcytosis for Enhanced Deep Tumor Penetration

Charge-reversal nanoparticles (NPs) have the potential to enhance tumor penetration, but conventional tumor microenvironment-dependent reversal strategies suffer from low selectivity, slowness, and heterogeneity-impaired efficiency. Here, we discovered that coumarin-derived carbamate (CDC) exhibits ultrasound (US) responsiveness, enabling amino group exposure upon irradiation by a physiotherapeutic US apparatus. We then engineered US-triggered charge-reversal NPs using a polyamino acid scaffold with anionic carboxylate side chains, functionalized with CDC and loaded with therapeutic agents. Our NPs exhibited concentration- and pH-dependent rapid charge reversal, enabling zeta potential reversal from negative to positive values within 5 min at pH 6.8 via US-triggered amino group exposure. With US irradiation, the NPs achieved 3.0-fold deeper penetration and 341-fold enhanced cytotoxicity in 3D tumor spheroid models. As surface charge transitions from negative to positive, the primary endocytic pathway of the NPs shifted from macropinocytosis to caveolin-mediated endocytosis, which in turn promoted Golgi-dependent iterative transcytosis, thereby boosting intratumoral penetration. In the in vivo 4T1 murine breast cancer model, the NPs plus US elicited 93% tumor growth inhibition without detectable systemic toxicity. This approach employs US to achieve spatiotemporal control of chemical reactions, enabling efficient and rapid charge reversal and offering a strategy to enhance NP penetration into tumors.