Ultrasound Mediated lntracellular Drug Delivery in 2D Biological Scaffolds
Successful intracellular drug and gene delivery represents a major goal for medical researchers. Sonoporation (i.e. the formation of pores using sound) is considered one of the most promising techniques, especially since it is non-destructive and as it can be carried out deep inside the body under image guidance. The mechanism of sonoporation is not fully understood. Presently, the vast majority of in vitro sonoporation investigations are carried out on cells in monolayer in plastic dishes. These systems are problematic from a variety of aspects. Ultrasound interaction with the wells, themselves acoustically incompatible, can result in unwanted phenomena such as mode conversion, heat generation, and standing waves. These factors combined can lead to uncertainties of up to 700% in the actual ultrasound exposure experienced by cells. Biological scaffolds can serve as an artificial extra cellular matrix to support different cell processes. Compared to plastic dishes, they more realistically resemble the in vivo environment in terms of how ultrasound interacts with cells and the extracellular matrix. The goal of this project was to develop a more biologically and acoustically compatible platform for investigating the process of sonoporation. I have developed a prototypical 2D biological scaffold, based on chitosan and gelatin. Scaffolds formulation was optimized for both cell adhesion and proliferation. I have also designed and custom built an acoustically compatible treatment chamber, where problematic issues of current setup were minimized. The acoustic activity inside the chamber was verified. The acoustic compatibility of the scaffolds was demonstrated using B-mode diagnostic ultrasound imaging and transmission test, compared to traditional culture dish. To study cell survival, sonoporation experiments were carried out over a range of ultrasound intensities and durations in this novel system. High cell survival (i.e. 83%) was achieved at 0.8 w/cm2 for 30 sec. Fluorescent imaging revealed successful intracellular delivery of nanoparticles at this ultrasound exposure. At the same ultrasound exposure, when carried out in a well plate, lower cell survival and higher variability was obtained. Acoustic incompatibility of culture plates produces less predictable results. This new platform was more acoustically compatible, allowing more predictable ultrasound exposures, and more consistent results.
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