Nanosized Hollow Colloidal Organosilica Nanospheres with High Elasticity for Contrast-Enhanced Ultrasonography of Tumors.

Despite several reports on using silica hollow spheres as ultrasound contrast agents, they all suffer from their inherent drawbacks, e.g., poor imaging ability caused by highly rigid shell or large particles size that leads to failures of these particles in entering tumor tissues, no mesoporous channels to load other active molecules (e.g., fluorocarbons). In this report, amino groups-functionalized hollow colloidal organosilica nanospheres (HCONs) with approximately 260 nm in diameter are prepared. Depending on the thin and pure organosilica shell, the HCONs feature high elasticity beneficial for acquiring excellent ultrasonic imaging outcomes. Our in vitro experiment shows that the ultrasonic contrast increases 11 times and in vivo experiment also shows that the ultrasound imaging performance of tumor is improved for 1.5 times. More importantly, HCONs can load liquid perfluorohexane (PFH) capable of vaporizing into gas bubbles, which further enhance the ultrasonic imaging outcome. In addition, the organosilica nanospheres have a good biosafety, which is expected to become a new generation of ultrasound contrast agent.