Targeted phase-change contrast agents for intracellular delivery to breast cancer tumors: An In vitro study in MDA-MB-231 breast cancer cells

Abstract

We have found that folate-targeted, ultrasound-activated phase-change contrast agents (PCCAs) composed of volatile perfluorocarbons are able to bind and internalize within breast cancer cells prior to vaporization into intracellular microbubbles. We here report studies assessing internalization, stability to thermal activation, and ultrasound activation of PCCAs formed by condensation of dodecafluoropentane (DDFP), decafluorobutane (DFB), and octafluoropropane (OFP). Using a Zonare “z.one-ultra” ultrasound system and L14-5sp probe operating in B-mode at 9 MHz (frame rate 13 Hz) to activate PCCAs and imaging with a Leica confocal microscope, we studied delivery in cultured MDA-MB-231 breast cancer cells with folate-targeted PCCAs. The number of internalized bubbles pre- and post- insonation were measured as a function of: 1) PCCA incubation times (i.e 10 mins, 60 mins); 2) ultrasound exposure (4 passes vs. 12 passes); and 3) mixtures of OFP, DFB, and DDFP. DFB:DDFP PCCAs, 60 minute incubations, and 12 passes offered a promising combination of stability and activation, with post-ultrasound to pre-ultrasound microbubble ratios approximating 3.4 (microbubbles pre-ultrasound per cell = 0.68 + /- 0.49, microbubbles post-ultrasound per cell = 2.35 + /- 0.79). Results indicate that intracellular delivery of targeted-PCCAs can potentially offer a new methodology for clinical application with ultrasound-mediated intracellular imaging of breast cancer.