Acoustic nanodrops for biomedical applications

Phase-shift nanodroplets as an emerging sonoresponsive nanomaterial for imaging and drug delivery applications

“…Other nanoparticles used in SDT can be further referred from a review published by Canavese et al 5 Traditional UCAs are gas-filled microparticles with acoustic properties, i.e., the ability to produce echogenicity from acoustic exposures, widely known as microbubbles. 10 The first generation of microbubbles was Albunex®, an echo-enhancer with an air core and a shell constructed with protein albumin. Highly echogenic contrast agents can majorly amplify ultrasound signals even in a low contrast medium, such as blood.…”

Predicting initial nucleation events occurred in a metastable nanodroplet during acoustic droplet vaporization

“…Phase-change nanodroplets emerging as an alternative to conventional microbubbles are highly attractive for cancer theranostics. They are usually composed of a volatile perfluorocarbon (PFC) liquid core and a stabilizing shell of lipid, polymer, protein, or fluorinated surfactant [1] , [2] , [3] , [4] . Thanks to their smaller size and longer circulation time in vivo relative to microbubbles, the PFC nanodroplets are able to passively accumulate in solid tumors via the enhanced permeability and retention (EPR) effect [5] .…”

“…Thanks to their smaller size and longer circulation time in vivo relative to microbubbles, the PFC nanodroplets are able to passively accumulate in solid tumors via the enhanced permeability and retention (EPR) effect [5] . Upon external ultrasound stimulation above a certain threshold, these nanodroplets can be vaporized into microbubbles in situ , a process known as acoustic droplet vaporization (ADV) [1] , [2] , [3] , [4] . It can significantly enhance the ultrasound imaging in the tumor region for treatment guidance/monitoring [6] , [7] , meanwhile, can also perform therapeutic actions such as on-demand drug release [8] , [9] , cell sonoporation [10] , [11] , HIFU sensitization [12] , [13] , and targeted neuromodulation [14] , etc.…”

“…It can significantly enhance the ultrasound imaging in the tumor region for treatment guidance/monitoring [6] , [7] , meanwhile, can also perform therapeutic actions such as on-demand drug release [8] , [9] , cell sonoporation [10] , [11] , HIFU sensitization [12] , [13] , and targeted neuromodulation [14] , etc. For these theranostic applications, the PFC nanodroplets are expected to be reliable and effective only if they do not spontaneously vaporize or dissolve after intravenous injection in vivo , and also can be vaporized in situ with a low enough threshold to avoid adverse effects, hence requiring a trade-off between in vivo stability and ADV threshold [2] , [4] .…”

“… [15] , [16] , [17] , [18] , [19] . One attempt has been made to reduce the ADV threshold via utilizing PFC species with lower boiling points (e.g., perfluoropropane or perfluorobutane) [20] , [21] , but these PFCs are more water soluble [22] , faster clear and more likely to occur spontaneous vaporization during in vivo circulation [1] , [2] , [3] , [4] , which would limit their utility. Alternatively, replacing them with perfluoropentane (PFP) having a relatively higher boiling point and lower solubility should notably increase the circulation persistence, but the latter is more difficult to vaporize because of a higher ADV threshold [1] , [2] , [3] , [4] .…”