We present a new class of ultrasound molecular imaging agents that extend upon the design of micromotors that are designed to move through fluids by catalyzing hydrogen peroxide (H 2 O 2 ) and propelling forward by escaping oxygen microbubbles. Micromotor converters require 62 mM of H 2 O 2 to move -1000-fold higher than is expected in vivo. Here, we aim to prove that ultrasound can detect the expelled microbubbles, to determine the minimum H 2 O 2 concentration needed for microbubble detection, explore alternate designs to detect the H 2 O 2 produced by activated neutrophils and perform preliminary in vivo testing. Oxygen microbubbles were detected by ultrasound at 2.5 mM H 2 O 2 . Best results were achieved with a 400-500 nm spherical design with alternating surface coatings of catalase and PSS over a silica core. The lowest detection limit of 10-100 µM was achieved when assays were done in plasma. Using this design, we detected the H 2 O 2 produced by freshly isolated PMA-activated neutrophils allowing their distinction from naïve neutrophils. Finally, we were also able to show that direct injection of these nanospheres into an abscess in vivo enhanced ultrasound signal only when they contained catalase, and only when injected into an abscess, likely because of the elevated levels of H 2 O 2 produced by inflammatory mediators.

Peliosis hepatis, an uncommon vascular condition, is characterized by multiple blood-filled cavities distributed throughout the liver. Computed tomography and magnetic resonance imaging findings of peliosis hepatis are nonspecific. A 40-year-old woman presented with multiple hepatic cystic masses. Two years later, the number and sizes of the masses had increased. We suspected metastatic hepatic disease and performed a liver biopsy. Histological examination revealed dilatation of hepatic sinusoids and multiple blood-filled cavities throughout the liver parenchyma. Thus, a diagnosis of peliosis hepatis was confirmed.

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