CA9 and neoplasm: US imaging of intravenously injected nanobubbles functionalized with scrambled ssDNA into CAIX-positive 786-O and HeLa or CAIX-negative BxPC-3 xenografts showed comparable tumor contrast enhancement in all tumors, while aptamer targeted nanobubbles led to a moderate but statistically significant further increase in signal intensity only in 786-O and HeLa xenografts.