| Many therapeutic agents such as chemotherapeutic drugs and therapeutic genetic material require delivery to the cell cytoplasm to be effective. However, access to the cytoplasm is limited by the cell membrane which regulates transport to and from the cell cytoplasm. Disruption of the cell membrane would provide a pathway for large molecules to the intracellular environment. The objectives of this project were to demonstrate that ultrasound and membrane-disruptive polymers can synergistically disrupt cell membranes and elucidate the mechanisms for the noted bioeffect.; Studies were conducted using red blood cells as a model for biological membranes and the release of hemoglobin as an indication of membrane disruption. Cell membrane disruption was achieved when cells were incubated with either poly(ethyl acrylic acid) (PEAA) or poly(propyl acrylic acid) (PPAA) and exposed to high intensity focused ultrasound (HIFU). Ultrasound+polymer synergy was dependent upon the pH of the cell suspension, acoustic intensity, and acoustic cavitation activity. Through a series of experiments to study the synergy between HIFU and PPAA, it was determined that (1) solubilized PPAA is a surface-active molecule that can reduce the dissolution rate of an air bubble in liquid, (2) the pH-sensitivity of the synergy is dependent upon the stereochemistry of the polymer, (3) hemoglobin release from cells treated with HIFU+PPAA correlated with inertial cavitation dose, and (4) adsorbed PPAA can enhance cavitation-induced hemolysis. The evidence presented in this work demonstrated that ultrasound+polymer synergy can be controlled through the design of the polymer, acoustic parameters, and the availability of cavitation nuclei. The synergy between ultrasound and membrane-disruptive polymers has great potential as a technique for localized drug and gene delivery across cell membranes. |
