Effect of Acoustic Pressure on Temozolomide-Loaded Oleic Acid-Based Liposomes and Its Safety to Brain Tissue.

Background: Glioblastoma (GBM) is a highly aggressive primary brain tumor with limited therapeutic options, particularly due to the limited blood-brain barrier (BBB) permeability. Nanoparticle-based drug delivery systems, such as liposomes, can prolong drugs' circulation time and enhance their accumulation within brain tumors, thereby improving therapeutic outcomes. Controlled drug release further contributes to high local drug concentrations while minimizing systemic toxicity. Oleic acid (OA), a monounsaturated fatty acid, is commonly used to enhance drug loading and increase lipid membrane fluidity. In this study, we developed liposomal formulations with optimized temozolomide (TMZ)'s loading and analyze its response to focused ultrasound (FUS). Methods: We synthetized OA-based liposomes with different lipid composition, performed physicochemical characterization (DLS, TEM) and analyzed the TMZ loading efficiency. Different FUS parameters were tested for effective OA-based liposomes destruction. Safety of selected parameters was evaluated in vivo by MRI, histological staining and RT-PCR of pro-inflammatory cytokines. Results: All the formulations exhibited comparable hydrodynamic diameters; however, OA-containing liposomes demonstrated a significantly higher TMZ encapsulation efficiency and enhanced cytotoxicity in U87 glioma cells. Moreover, it was shown that OA-liposomes were disrupted at lower acoustic pressures (5 MPa), while conventional liposomes required higher thresholds (>8 MPa). A safety analysis of FUS parameters indicated that pressures exceeding 11 MPa induced brain edema, necrotic lesions and elevated cytokine levels within 72 h post-treatment. Conclusions: These results suggest that OA-based liposomes possess favorable characteristics, with an increased sonosensitivity for the site-specific delivery of TMZ, offering a promising strategy for glioma treatment.