Abstract 281: pH-sensitive liposome for siRNA delivery to treat drug-resistant ovarian cancer

Introduction: With a 5-year survival rate of 47%, ovarian cancer is the 5th leading cause of death amongst women worldwide. Over 75% of patients experience recurrence after initial treatment, indicating a need for improved treatment options. Drug resistance is a major barrier hindering the success of current treatment methods. Our study analyzes the characteristics of a stimuli-sensitive liposomal delivery system for combatting drug resistance. Our delivery system will deliver bioactive siRNAs targeting genes related to drug resistance, cell proliferation, and apoptosis. In this study, we investigate the characteristics of the liposomes to determine particle size, surface charge, and ability to encapsulate/bind both siRNAs. We also begin to investigate the delivery potential of the pH-sensitive liposomal formulation in vitro using ovarian cancer cell lines. Methods: Empty and siRNA loaded cationic, pH-sensitive liposomes (CHEMS-LPs) were synthesized by the thin-film hydration method. Liposome size, zeta potential, and polydispersity index (PDI) were measured by dynamic light scattering (DLS). To measure siRNA encapsulation efficiency, fluorescently labeled siRNA was loaded into CHEMS-LPs and subjected to centrifugation to pellet the LPs. Fluorescence spectroscopy was used to detect siRNA in the supernatant. The toxicity of unloaded CHEMS-LPs was determined by an MTS assay using OVCAR3 (drug-sensitive) and OVCAR3-T40 (drug-resistant) human ovarian cancer cells. Results: The size and zeta potential of blank and siRNA-loaded CHEMS-LPs were 97.88 ± 2.39 nm and 29.0 ± 2.00 mV, and 80.78 ± 0.77​ nm and 13.1 ±1.66​ mV, respectively. The positively charged zeta potential confirms the cationic nature of our liposomes. The PDI demonstrated that the liposomes were unimodal and monodisperse with PDI values of less than 0.300 for each formulation. In addition, siRNA was successfully bound to CHEMS-LPs through electrostatic interaction with the cationic lipid layer, resulting in an encapsulation efficiency of 99.6% Conclusion: CHEMS-LPs are pH-sensitive, cationic, monodisperse liposomes able to encapsulate siRNAs in order to mediate delivery into ovarian cancer cells. Their stable structure, positive charge, and low cytotoxicity is promising for future studies, including delivery of bioactive siRNAs to stimulate downregulation of target genes related to drug resistance. Acknowledgements: This work was supported in part by the National Science Foundation EPSCoR Program under Award # OIA-1655740. We would like to thank George Duran from Stanford University for donating the OVCAR3-T40 cell line. Citation Format: Kharimat Lora Alatise, Samantha Gardner, Angela Alexander-Bryant. pH-sensitive liposome for siRNA delivery to treat drug-resistant ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 281.