Opening the Blood-Brain Barrier and Improving the Efficacy of Temozolomide Treatments of Glioblastoma Using Pulsed, Focused Ultrasound with a Microbubble Contrast Agent

OBJECTIVE: To explore the effects of pulsed, focused, and microbubble contrast agent-enhanced ultrasonography (mCEUS) on blood-brain barrier (BBB) permeability and the efficacy temozolomide for glioblastoma. METHODS: Wistar rats (n = 30) were divided into three groups (n = 10 per group) to determine optimal CUES conditions for achieving BBB permeability, as assessed by ultrastructure transmission electron microscopy (TEM) and western blot assays for the tight junction protein claudin-5. Optimized mCEUS effects on BBB permeability were subsequently confirmed with Evans blue staining (2 groups of 10 rats). The glioma cell line 9L was injected into the brain striatum of Wistar rats. After temozolomide chemotherapy, we detected glial fibrillary acidic protein (GFAP) levels in serum by enzyme-linked immunosorbent assay (ELISA) and in brain tissue by western blot, immunocytochemistry, and real-time quantitative polymerase chain reaction (qPCR). RESULTS: BBB permeability was maximized with 1 ml/kg contrast agent mCEUS delivered via 10-min intermittent launches with a 400-ms interval. Evans blue staining confirmed BBB permeability following ultrasonic cavitation in the control group (P < 0.05). Following temozolomide chemotherapy, levels of the tumor marker GFAP were increased in the group with ultrasonic cavitation compared with the control group (P < 0.05). CONCLUSIONS: When rats were treated by mCEUS with intermittent launches (interval, 400 ms) and injected with 1 mg/kg contrast agent, BBB permeability was increased and temozolomide BBB penetration was enhanced, therapeutic enhancement for glioblastoma.