Abstract 2984: Building an in vitro blood brain barrier model to test the influence of tight junction gene alleles on disruption by focused ultrasound to treat brain tumors
Authors: Iyer Jayashree , Akkad Adam , Tang Nanyun , Berens Michael E. , Zenhausern Frederic , Gu Jian 
Published: July 2021

Abstract
Treating primary or metastatic tumors in the brain (glioblastomas, melanoma, lung cancer, breast cancer) proves challenging by virtue of the protective function of the blood brain barrier (BBB). Recently, it has been shown that low intensity focused ultrasonic (LIFU) waves stably cavitate infused microbubbles which then mechanically disrupt the tight junctions of the BBB. This leads to temporary, recoverable opening of the BBB, and passage of otherwise disqualified cancer-therapeutic drugs at precise locations targeted by the focused ultrasound. To date, potential genetic influences on the durability and vulnerability of tight junctions to LIFU have not been elucidated, nor have the determinants of tight junction repair post LIFU been thoroughly investigated. We report the development of an ultrasound transparent organ-on-chip model to test LIFU with microbubble infusion treatment on a cell-engineered BBB. The BBB is developed using brain-specific endothelial cells derived from genomically characterized immortalized pluripotent stem cells (iPSC). Furthermore, to test genetic variation effects we propose that alleles coding for the proteins involved in tight junction assembly contribute to LIFU disruption variability. Developing preclinical models of the BBB to accommodate cell sources with tight junction genes of different allele makeup will shed light on how individuals will respond to different ultrasound frequencies. The in vitro BBB device is composed of two orthogonally stacked fluidic channels formed by top and bottom polydimethylsiloxane (PDMS) membranes and a middle polyester membrane with 3 µm pores. An ultrasound system is constructed with a waveform generator, amplifier, and 1MHz ultrasound transducer. A 0.5 MHz receiving transducer and a digital storage oscilloscope are used for stable cavitation monitoring. Nanobubbles (FUS Instruments) transduce the LIFU into a mechanical vibration force to disrupt the BBB. To deliver the ultrasonic waves, the device is submerged in degassed DI water in a custom tank. Fluid flow was achieved, and subharmonic ultrasound signal is observed using the digital oscilloscope with Fast Fourier Transform (FFT). Preliminary results convey stable cavitation with LIFU and the formation of tight junctions in a brain microvascular endothelial cell monolayer in the device, eventually leading to a versatile platform to evaluate genetic-based vulnerability of the BBB.
Citation Format: Jayashree Iyer, Adam Akkad, Nanyun Tang, Michael E. Berens, Frederic Zenhausern, Jian Gu. Building an in vitro blood brain barrier model to test the influence of tight junction gene alleles on disruption by focused ultrasound to treat brain tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2984.