Motor-Cargo Structured Nanotractors for Augmented NIR Phototherapy via Gas-Boosted Tumor Penetration and...

Tumor microenvironment, characterized by dense extracellular matrix and severe hypoxia, has caused pronounced resistance to photodynamic therapy (PDT). Herein, it has designed an artificial nitric oxide (NO) nanotractor with a unique "motor-cargo" structure, where a photoswitching upconversion nanoparticle (UCNP) core serves as the optical engine to harvest NIR light and asymmetrically coated mesoporous silica (SiO₂) shell acts as a cargo unit to load nitric oxide (NO) fuel molecule (RBS, Roussin's black salt) and PDT photosensitizer (ZnPc, zinc phthalocyanine). Upon illumination by 980 nm light, the UCNP emits blue light to excite RBS salt and release NO gas. On one hand, NO is used as the driving force to propel the particle with a high speed of ≈194 µm s^-1 that generates significant rupture stress (over 0.95 kPa) on cell membrane to promote cellular endocytosis and intratumoral penetration. On the other hand, NO enables to alleviate tumor hypoxia by inhibiting cellular respiration as an oxygen conserver. When the excitation is subsequently switched to 808 nm light, the UCNP emits red light, triggering ZnPc to produce large amount of reactive oxygen species for PDT treatment. This study explores Janus-typed nanostructures for cell-particle interaction and gas-assisted phototherapy, opening avenues for versatile bioapplications.