Size-dependent ultrasound enhancement of nanoparticle endocytosis in tumor cells

Efficient cellular endocytosis is crucial for the therapeutic success of nanodrug delivery. Although ultrasound (US)-mediated sonoporation has been widely exploited to enhance drug delivery efficiency, the interplay between US exposure and nanoparticle endocytosis remains poorly understood. In this work, we systematically investigate the tumor endocytosis patterns and underlying mechanisms of multi-sized silica nanoparticles (SiO₂ NPs) US stimulation. Our experimental results demonstrate that US exposure can significantly enhance the cellular uptake of SiO₂ NPs within the 20-80 nm range in cancer cells. Notably, US exposure led to a statistically significant increase in the internalization of 40 nm nanoparticles, resulting in a 3.8-fold increase in cellular uptake efficiency. Mechanistic studies further demonstrated that US-induced sonoporation promoted energy-independent cellular internalization of 20 nm particles. US exposure not only counteracted the inhibitory effects of caveolae-mediated, clathrin-mediated, and phagocytic endocytosis blockers but also synergistically amplified nanoparticle uptake via multiple endocytic pathways. These findings elucidate the critical role of nanoparticle size in modulating US-enhanced endocytosis, providing fundamental guidance for engineering stimulus-responsive nanocarriers optimized for US-actuated drug delivery systems. These advancements pave the way for more effective and precise nanomedicine strategies, holding significant implications for clinical translation.