Nozzle-free droplet generation with focused acoustic beams for encapsulation of single circulating tumor cells

The recovery of single circulating tumor cells (CTCs) from the peripheral blood of cancer patients has great potential for the study of cell heterogeneity and cancer metastasis and the development of personalized cancer immunotherapy. Here we present nozzleless droplet generation with focused acoustic beams for cell encapsulation. The mechanism of droplet generation is sensitive to the pulse width and the droplet diameter ranges from 350 to 550 mu m. The pulse width duration (520 mu s) and cell concentration (5 x 10(3) cells ml(-1)) can be adjusted to obtain the maximum probability (11.61%) of single cell encapsulation. Three-color fluorescence is used to identify encapsulated cells in the droplet and target cells are extracted by microcapillarity for conducting single cell analysis. The reported method of using acoustic tweezers to eject the droplet has advantages of convenience, speed and biocompatibility while being non-invasive, and could become a powerful tool for encapsulating single CTCs.