Combined use of focused ultrasound and targeting microbubbles to enhanced therapeutic EGFR antibody delivery: Observations from small-animal ultrasound imaging

Recently, emerging discovery of the combined used of microbubbles (MBs), an ultrasound imaging contrast agent, in focused ultrasound (FUS) can enhance the blood-tissue permeability and may enhanced local drug delivery. When coating the targeting ligands on MBs, for example, therapeutic antibodies, may further improve the therapeutic efficacy. The aim of this study is to demonstrate the use of the epidermal growth factor receptor (EGFR)-targeting MBs with focused ultrasound to enhance the permeability of tumor vessels and evaluate the potential of FUS mediates therapeutic-EGFR antibodies delivery to glioma tumor cells using EGFR-targeting MBs. 30 BALB/c nude mice were used with U87 cells were implant to right-lower limbs until the tumor reach 10 mm in diameter. Here, the biotinylated MBs mixed with avidin-modified therapeutic EGFR antibodies were served as the targeting MBs, whereas the biotinylated MBs only served as the non-targeting microbubbles. Three animal groups were conducted: (1) Non-targeting MBs injected intravenously (IV), (2) targeting MBs IV injection, and (3) FUS exposure (pulsed mode, burst length = 10 ms, PRF = 1Hz, duration = 30s; extra non-targeting MBs were simultaneously presented during exposure) prior to targeting MBs injection. All animal groups were monitored and analyzed by using high-frequency small-animal ultrasound imaging system (Vev02100, VisualSonics, CA). The lifetime of targeting MBs in the tumor was longer than non-targeting MBs. When adding the FUS exposure to enhance the blood-tissue permeability; the lifetime of targeting MBs was significantly improved. The mean half-time of the circulating targeting MBs among the three groups were (1) 2.34, (2) 3.13, and (3) 5.86 minutes, respectively. Moreover, inhibition of EGFR with targeting MBs after pulse-FUS mediated SonoVue treatment has been shown to reduce the growth rate in U87 glioma tumors. The tumor volume doubling times in targeting MBs and FUS+targeting MBs were -38.2343% and -2- 9.83%, compared with control-treated animals. This study provides useful information for FUS mediates anti-cancer targeting therapy with targeting MBs.