Over the last century, significant progress has been made towards the development of microbubbles (MBs) as a contrast agent for imaging and as a carrier for the delivery of therapeutic moieties. The unparalleled ability of MBs to respond to ultrasound (US) render them advantageous for molecular imaging, and US-responsive targeted delivery. However, the use of MBs has broadened far beyond the imaging contrast agent or drug delivery system alone. Notably, there has been an enormous surge in the design and fabrication of multimodal MBs for cancer therapy. Furthermore, MBs in the presence of the US has unique ability to convert itself from the micro to nanoscale, which offers diagnostic and therapeutic ability in both dimensions. In this review, we summarize the design considerations of MBs, with particular emphasize on their size and composition. In addition, different MBs formulations are discussed in the context of their current progress as an imaging contrast agent and a vehicle for drug/gene delivery. We further highlight recent advancements in the micro-to-nano conversion of MBs and their potential application for cancer theranostics. This article is characterized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies.
Keywords: cancer therapy; contrast agent; drug delivery; micro-to-nano conversion; microbubbles.
© 2019 Wiley Periodicals, Inc.