Development of a novel folate-modified nanobubbles with improved targeting ability to tumor cells.

•A novel FR-targeted ultrasonic nanobubble with increasing folate content was prepared.•Increasing folate content in nanobubble was accomplished by linking two folate molecules per DSPE-PEG2000 chain.•This novel nanobubble showed a good US contrast imaging ability.•This novel nanobubble showed a better targeted ability to FR-positive tumor cells.