A Master of Science thesis in Chemical Engineering by Salma Elgaili Ahmed entitled, "Dynamics of Chemotherapeutic Drug Release from Liposomes Using Low-Frequency Ultrasound," submitted in January 2015. Thesis advisor is Dr. Ghaleb Husseini. Available in both soft and hard copy.
This thesis focuses on the study of liposomes; nanoparticles that can act as anticancer drug carriers, in combination with ultrasound applied as a drug trigger, with the objective of reducing the side effects caused by traditional chemotherapy. For the purpose of this thesis, PEGylated (containing poly-ethylene glycol) and non-PEGylated liposomes were used to encapsulate calcein and then release this model drug when 20- and 40-kHz ultrasound were applied at different acoustic power densities. Fluorescence techniques were used to measure the percent calcein release from these liposomes at different pH values (5.2 and 7.4). The release experiments were done offline (discontinuous) and also online (continuous measurements), where the latter was conducted to allow the modeling of the results. The size of the synthesized liposomes was determined by Dynamic Light Scattering, and found to be similar for both types of liposomes. The release results obtained offline showed that the release from non-PEGylated liposomes is higher at pH 7.4 than at pH 5.2, for all used power intensities. The release from PEGylated liposomes is similar at both pH's, except for the highest power intensity, where the release at pH 7.4 is significantly higher. Comparing the release from non-PEGylated and PEGylated liposomes at the same pH, it was observed that, at pH 5.2, there are no significant differences, but at pH 7.4 the release from non-PEGylated liposomes seems to be significantly higher. However, the results obtained from the online experiments showed no significant differences between both types of liposomes at pH 7.4. Finally, models of the release from non-PEGylated and PEGylated liposomes were built using artificial neural network (ANN).