Ultrasound Mediated Intracellular 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/cm^2 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.

Adham M Aleid PhD