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

## TL;DR

This study shows that using ultrasound-activated nanobubbles can soften tumors, improving the delivery and effectiveness of lipid nanoparticle-based immunotherapies.

## Contribution

The novel use of ultrasound-activated nanobubbles to reduce tumor stiffness and enhance immunotherapy delivery is introduced.

## Key findings

- US-NBs reduced tumor stiffness by 60% after a single treatment.
- LNPs showed 4-fold increased cytotoxic cell infiltration when combined with US-NBs.
- US-NB treatment enabled efficient in vivo genetic modification of T cells.

## Abstract

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.