Multi-Responsive Upconversion Hybrid Nanobots Clad with Dopamine for Light-Driven Breast Cancer Therapy.

The field of fuel-free light-powered nano/microbots with stimulus-responsive behavior can have crucial implications for biomedical research. In this study, we have synthesized smart NIR laser-responsive self-propelling folic acid-functionalized, dopamine-coated, and rose bengal-loaded upconvertible nanobots that exhibited unidirectional phototaxis in the presence of the NIR laser. When exposed to a 980 nm laser, the nanobots demonstrated positive phototaxis with a speed of ≈27 ± 7 μm/s at a power of 1500 mW. These further confirmed stimuli-regulated phototaxis in the presence of various factors like pH, GSH, light intensity, and media composition, enabling their potential usage as a site-specific and stimuli-triggered therapeutic modality. They showed significant tumor growth inhibition (%) in 4T1 tumor-bearing Balb-C mice. The relative tumor volume was much reduced in the presence of a 980 nm laser after treatment with FA-conjugated nanobots. Thus, we have developed a versatile and noninvasive tool for treating breast cancer through precise, spatiotemporal control based on photoreactions, photoisomerization, and thermophoresis, which opens new avenues for implementing nanorobotics and biophotonics in effective cancer therapy.