Fig. 4

Cavitation effect and tumor penetration of MSF@CCM. a Noise signals obtained by the hydrophone for H₂O, MSF and MSF@CCM groups. b FFT spectra of H₂O, MSF and MSF@CCM cavitation noise signals obtained by hydrophone. c Integral areas under the FFT curves for different groups. Data are presented as mean ± SD (n = 10). d CLSM images of the tumor penetration of MSF and MSF@CCM in MTSs with or without US (1.0 MHz, 1 W cm⁻², 3 min, 50% duty cycle) irradiation for 24 h. Scale bar = 200 μm. e The corresponding variance of fluorescence signal intensity along the dotted lines for 4T1 MTSs 24 h in (d). f The penetration of MSF and MSF@CCM after i.v. injection without or with US irradiation (1.0 MHz, 1.5 W cm⁻², 5 min, 50% duty cycle) in the tumor. Blood vessels are labeled with CD31 (red), and MSF and MSF@CCM are labeled with FITC (green), respectively. Scale bar = 100 μm. g The corresponding fluorescence intensity of green across along the lines in the 4T1 tumor section images in (f). h Average fluorescence intensity from the blood vessel to the in-depth tumor parenchyma in the selected region at (f), as indicated by yellow arrows. Data are presented as mean ± SD (n = 3). One-way ANOVA with Tukey’s multiple comparison was used to calculate statistical differences in c and h