REAL-TIME IMAGING OF INTERACTION BETWEEN MICROBUBBLE AND CELL UNDER THERAPEUTIC ULTRASOUND IRRADIATION

摘要

Cellular engineering with ultrasound is applied for gene delivery and ultrasound therapy. To understand the effect of therapeutic ultrasound irradiation, we first observed intracellular Ca~(2+) concentration ([Ca~(2+)]_i) in cultured MC3T3-E1 cells by staining cells with Fura-2. As a result, both plasma membrane rupture and [Ca~(2+)], increase were observed. Because observed [Ca~(2+)]_i increase was induced by plasma membrane rupture in a neighbor cell, at least in part, it was indicated that plasma membrane rupture was a dominant effect in our experimental setup. To verify the speculation that microbubble was involved in observed plasma membrane rupture, real-time imaging of interaction between microbubble and plasma membrane was realized by visualizing microbubble and plasma membrane simultaneously with transparent bright field light and Dibac4. As a result, microbubble traveled through nearby plasma membrane and plasma membrane ruptured immediately. Our results indicate that microbubble traveling has enough impact to disrupt plasma membrane without microbubble collapse under therapeutic ultrasound irradiation in vitro.