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Superhydrophobic mesoporous silica nanoparticles as ultrasound contrast agents

The size and stability of microbubbles limited their widely applications both for diagnosis and as drug/gene carriers for therapy. Nanoscale stable ultrasound contrast agents would therefore be worth developing. Generating bubbles in situ from nanoscale precursors is a promising solutions to the problem of short lifetime by providing stable air nuclei. The interfacial nanobubbles show a surprising longer lifetime on a hydrophobic surface has been demonstrated in many studies. Mesoporous silica nanoparticles (MSNPs) with different hydrophobicity were proposed to test our hypothesis due to their large surface areas and easy surface modification. Compared with other nanoparticles, the superhydrophobic and porous nanoparticles exhibited a significant and strong contrast intensity. The superhydrophobic nanoparticles enhanced the contrast for at least 30 minutes at a MI of 1.0, while lipid microbubble lasted for about 5 minutes at the same settings. After simple superhydrophobic modification, we found that MSNPs have been changed to reliable bubble precursors, showing potentials as stable and nanoscale ultrasound agents.