Magnetically Driven Lasing Microrobots for Precise Photodynamic Therapy

Photodynamic therapy (PDT) is an emerging approach for tumor treatment, valued for its noninvasive and stimuli-responsive properties. However, its therapeutic efficacy is often constrained by unintended damage to healthy tissues, largely due to the strong scattering of pump light within biological media. In this study, we present a magnetically driven lasing microrobot as an effective light source for high-precision localized PDT. The microrobots were constructed from polystyrene microspheres doped with Nile Red and magnetic particles. When pumped with 530 nm light, these microrobots emit strong coherent whispering-gallery-mode (WGM) lasers at approximately 650 nm, matching the absorption of chlorin e6. A 20 μm microrobot demonstrated a lasing threshold of 52.1 μJ mm^-2 and a motion velocity of 78.5 μm s^-2 in biological media. Theoretically, the output power of the microrobot can meet the energy requirements for PDT treatment, while its illumination range reaches 35.1 μm. Leveraging its motion capabilities, the microrobot can navigate to targeted tumor sites on demand, enabling the precise ablation of tumor cells. PDT efficacy was validated using intestine-on-a-chip models and three-dimensional (3D) intestinal tumor spheroids. Results showed that the spatial resolution for tumor cell ablation reached 651.3 μm² in tumor spheroids, highlighting a significant improvement in therapeutic accuracy over conventional PDT approaches. This work integrates microlasers with robotic technology, offering a promising strategy for achieving high-precision PDT.