Characterization of microbubble-loaded stem cells for targeted cell therapy

The use of stem cells for the repair of damaged cardiac tissue after a myocardial infarction holds great promise. However, a common finding in experimental studies is that only a small fraction of the transplanted cells engraft in the infarcted area of the heart. In this study we investigated the use of stem cells conjugated with targeted microbubbles, creating echogenic complexes dubbed StemBells, to achieve increased stem cell delivery. The dynamics of the constructs in response to an ultrasound wave was characterized using high speed optical imaging. A modified Rayleigh-Plesset equation was developed to corroborate our experimental findings. We show that acoustic radiation force can be used to propel StemBells to the wall of a 200 µm vessel in a chicken embryo. This technique therefore facilitates the possibility to localize stem cell delivery to increase the engraftment and improve the clinical outcome of stem cell therapy.