Enhanced Delivery of Lipid Nanoparticle-Based Immunotherapy by Modulating the Tumor Tissue Stiffness Using Ultrasound-Activated Nanobubbles

Tumors often exhibit an extracellular matrix with elevated stiffness due to excessive accumulation and cross-linking of proteins, particularly collagen. This elevated stiffness acts as a physical barrier, impeding the infiltration of immune cells and the effective delivery of various immunotherapeutic agents, such as lipid nanoparticle-based RNA therapeutics. Here, we investigate the ability of ultrasound-activated nanobubbles (US-NBs) to increase the permeability and immunogenicity of tumors. Our results show that US-NBs physically remodel the tumor tissue by decreasing its stiffness by 60% 5 days after a single treatment. US-NB-treated tumors display randomly oriented collagen with a 5.47-fold lower deposition compared to untreated tumors. This leads to the effective delivery and widespread distribution of lipid nanoparticles (LNPs) in the tumor. Importantly, when assisted by US-NB, LNPs exhibit superior gene-transfection efficiency across pan-immune cells and achieve efficient genetic modification of T cells directly in vivo. This combined approach engages both innate and adaptive immunity, enhancing tumor immunogenicity and boosting cytotoxic cell infiltration by 4-fold compared to LNPs alone. These results indicate that gentle mechanical stimulation of the tumor using US-NB offers a promising strategy to augment the delivery and efficacy of existing immunotherapies.