Biomedical applications of acoustically responsive phase shift nanodroplets: Current status and future directions

The evolution of ultrasonic contrast agents to enhance the reflectivity of structures in the human body has consolidated ultrasound's stance as a reliable diagnostic imaging modality. A significant development within this field includes the advent of liquid nanodroplets that are capable of vaporising into gaseous microbubbles upon ultrasonic irradiation. This literature review will therefore appraise and summarise the available literature on the generation of phase-shift nanodroplets, their formulations, applications, safety issues, future developments and any implications that may inhibit their clinical implementation. The main findings of this review affirm that phase change nanodroplets do indeed demonstrate functionality in drug delivery and targeting and characterisation of tumours. Its bioeffects however, have not yet been extensively researched, prompting further exploration into how bubble size can be controlled once it has vaporised into microbubbles and the resulting complications. As such, future research should be directed towards determining the safety, longevity and suitability of phase-shift nanodroplets over contrast agents in current clinical use.