EFFECT OF BUBBLES ON CELL VIABILITY IN A CIRCULAR-LUMEN ENDOTHELIALIZED MICROVASCULAR MODEL

Abstract

A novel gas embolotherapy technique is being researched as a potential therapy for cancer. It involves the selective, acoustic vaporization of transvascular liquid perfluorocarbon droplets in or near a tumor, resulting in bubbles which can then stick within the tumor vasculature to occlude blood flow and “starve” the tumor. In achieving the desired outcome of ischemia of the tumor, it is hypothesized that the motion of bubbles within the vasculature would result in collateral endothelial cell injury and apoptosis, the extent of which being dependent on the bubble size and flow rate. A microvessel model has been designed for acoustic vaporization experiments as well as bubble flow experiments to investigate the above-mentioned hypothesis. The specific aim in the current work is to utilize the microvessel model in preliminary studies of the effects of bubble motion on endothelial cell injury and apoptosis. In a novel method of fabricating a microfluidic endothelialized model of a microvessel, a thin wire (diameter 50 to 200 micrometers, matching the desired microchannel dimension) threaded through a rectangular PVC mold was tightened into a straight line on a positioning device. The wire was sheathed in thin syringe needles inserted at both ends of the mold which was filled with a liquid elastomer, poly(dimethylsiloxane) (PDMS). After the PDMS was cured completely, the wire and syringe needles were extracted longitudinally from the cured PDMS, leaving a microchannel (due to the wire) and its inlet/outlet (due to the syringe needles). The microchannel was endothelialized at a density higher than 1x10E5 cells/cm 2 and maintained in an incubator with infusion of culture medium via a syringe pump. Air and PFC bubbles of different sizes were introduced into the microvessel model and moved at different flow rates. The viability of the cells within the microchannel was assessed with standard fluorescent microscopy and morphology studies. Our microvessel model has a circular lumen, optical clarity, gas permeability and is non-toxic to cells. The method of fabrication is also relatively simple and economical. The microchannel was successfully endothelialized, with >90% of the cells appearing viable in the assays, and the different parameters involved in optimal endothelialization of the microchannel were investigated. The effects of cell seeding parameters on cell viability, as well as preliminary findings regarding the effects of bubble size and speed, will be discussed. Ongoing work is aimed at quantifying the effects of bubble propagation and possible mechanisms of bioeffects.