Transformation of theranostic alginate-based microbubbles from raspberry-like to core–shell-like microbubbles and in vitro studies

In this study alginate-based microbubbles with a raspberry-like or core–shell-like morphology and with an average particle size of 553.6 ± 69.6 μm were synthesized; this was done through a novel procedure of transforming the structure with a 40 kHz ultrasonication which also stimulated the release of the components inside. Through the use of the electrospray technique in conjunction with agitation processes, components such as shikonin (SHK) and indocyanine green (ICG) were simultaneously encapsulated in alginate microbubbles to produce SHK–ICG alginate microbubbles; these microbubbles had half-maximal inhibitory concentrations of approximately 2.08 and 4.43 μM toward CP70 and SKOV3 ovarian cancer-cell lines, respectively, in an in vitro cell model. Moreover, these SHK–ICG alginate microbubbles enhanced brightness by 2.5 fold in ultrasound imaging relative to CaCl(2) medium only. In conclusion, SHK–ICG alginate microbubbles have promise for use in theranostics.