Near-Infrared-Triggered Nanodroplets for Imaging-Guided Macrophage-Mediated Cancer Immunotherapy

Immunotherapy has transformed cancer treatment; however, solid tumors often evade checkpoint blockade by co-opting tumor-associated macrophages (TAMs) and creating a hypoxic, immunosuppressive tumor microenvironment. Here, we report a laser-triggered theranostic nanodroplet capable of simultaneously remodeling the tumor microenvironment and visualizing therapeutic responses in real-time. These double-emulsion perfluorocarbon droplets encapsulate clinically translatable components: a toll-like receptor-7/8 agonist and near-infrared indocyanine green dye. Upon activation by a near-infrared laser pulse, the nanodroplets transform into echogenic microbubbles, facilitating imaging and targeted therapeutic release. In a mouse model of human triple-negative breast cancer, a single nanodroplet injection followed by periodic illumination repolarized M2-like TAMs into an M1 phenotype, alleviated intratumoral hypoxia, and synergistically anti-programmed-cell-death-protein-1 therapy, resulting in a six-fold reduction in tumor size compared to checkpoint blockade alone. Concurrent non-invasive dual-modal ultrasound and multispectral photoacoustic imaging tracked nanodroplet biodistribution, macrophage recruitment, and oxygen saturation longitudinally, enabling real-time guidance of dosing schedules without biopsy. The nanodroplets demonstrated greater than 60% loading efficiency, minimal hemolysis, and high biocompatibility in vitro. By coupling spatiotemporally controlled immunomodulation with quantitative imaging, this platform addresses critical challenges in treating refractory solid tumors and provides a roadmap for adaptive, image-guided combination immunotherapy.