Fig. 4: In vivo acoustic trapping of GVs@E. coli.

a Schematic diagram of in vivo experiment setup. I and II are the schematic diagrams of the acoustic trapping processes of the GVs@E. coli and control E. coli, respectively. Comparison of acoustic trapping of b GVs@E. coli and c control E. coli in superficial blood vessels on the backs of mice. I in (b, c) indicates the microscopic images of blood vessels in the absence of ultrasound after injection of GVs@E. coli and control E. coli, respectively. II in (b, c) shows the microscopic images of blood vessels after exposure to ultrasound for 180 s based on the situation I in (b, c), respectively. Only GVs@E. coli can be trapped at the focal beam centre and form clusters in the vessels. d Acoustic trapping of GVs@E. coli in blood vessels of different diameters. I, II, III and IV are microscopic images of 110-, 130-, 170- and 200-μm-diameter vessels injected with GVs@E. coli before the ultrasound is on, respectively. V–VIII are microscopic images of trapped GVs@E. coli clusters in the corresponding blood vessels in cases I–IV after the ultrasound is turned on for 20 s. The yellow arrows, white dotted circles, symbol d, and t in (b–d) indicate the blood flow direction, focal zones, vessel diameter, and time, respectively. e The curves of normalised fluorescence intensity increment over time within the focal zones under vessels of different diameters in (d). t1 to t4 represent the moment when the maximum increment of fluorescence intensity is reached in 200-, 170-, 130-, and 110-μm diameter vessels, respectively. f The area of the GVs@E. coli cluster in vessels of different diameters (after the ultrasound is turned on for 20 s). The in vivo acoustic trapping of GVs@E. coli is shown in Supplementary Movie 2.