[P007] Poster

12:10 PM - 1:00 PM JST(3:10 AM - 4:00 AM UTC)

[P04-527] Gondoic Acid-Induced Interfacial Sealing: Tuning Membrane Surface Properties for Thermal Robustness of Monoolein-DOTAP Nanoassemblies

○Supatcha Suankhem¹, Sitthanan Pongcharoen², Nozomi Morishita Watanabe¹, Hiroshi Umakoshi¹ (1. Division of Chemical Engineering, Graduate School of Engineering Science, The University of Osaka (Japan), 2. Faculty of Engineering, Department of Chemical Engineering, Mahidol University (Thailand))

Keywords:

Monoolein-DOTAP,Nanoassemblies,Gondoic acid,Thermal robustness,Membrane Surface Properties,Interfacial Sealing

Monoolein (MO)-based nanoassemblies incorporated with DOTAP have been extensively investigated as efficient cationic carriers for gene delivery due to their superior biocompatibility and high loading capacity. However, a major challenge remains in maintaining the structural integrity of these non-lamellar liquid crystalline systems, particularly under thermal stress. Exposure to elevated temperatures often induces undesirable phase transitions or membrane leakage, which can compromise the delivery efficiency. To address this, Gondoic acid (GA, C20:1) is introduced to enhance the structural integrity and thermal robustness of the lipid assembly. Due to its long hydrocarbon chain, GA has been reported to promote the formation of stable bicontinuous cubic phases. Understanding the interplay between MO, DOTAP, and GA is crucial for reinforcing the lipid bilayer. By investigating how these variations influence molecular packing and interfacial hydration, reinforcing the lipid bilayer through the incorporation of GA as a stabilizing agent is essential to enhance the functional performance of these nanoplatforms.This study systematically characterizes the membrane interface properties of a ternary MO-GA-DOTAP system across a thermal gradient from 25°C to 45°C to achieve structural controllability. Regarding the hydrodynamic diameter, all formulations exhibited their minimum size at 25 °C. Upon increasing the temperature to 37 °C, significant expansion was observed in the MO-DOTAP system, whereas MO and MO-GA remained relatively stable. Notably, at 45 °C, both MO and MO-DOTAP failed to maintain their structural integrity, resulting in a marked increase in particle size indicative of thermal-induced aggregation. In contrast, the MO-GA system showed minimal dimensional changes at elevated temperatures. Interestingly, while the synergistic zone (MO-GA-DOTAP) displayed the largest initial diameter at 25 °C due to reduced electrostatic repulsion, it uniquely exhibited a size reduction at higher temperatures, demonstrating superior thermal robustness compared to other compositions.These GA-rich nanoassemblies maintained an invariant particle size and high GP values throughout heating, reflecting a remarkably ordered and dehydrated interface. Cartesian plot analysis revealed an outstanding horizontal trajectory for the MO-GA system. This serves as a definitive biophysical indicator of a stabilized liquid-ordered (L_o)-like surface, despite the increased thermal mobility of the internal lipid tails (L_d-like state). Mechanistically, the long acyl chain, smaller headgroup and cis-double bond of GA allow for tighter lateral packing, which plugs potential water channels within the monoolein matrix. While GA acts as the primary shield, the ion-pairing effect between the negative charge carboxyl group (-COOH) and cationic DOTAP functions as a critical structural fixator, further enhancing the interfacial seal by reducing the effective area per headgroup. This decoupling mechanism effectively prevents excessive water penetration, which could lead to phase collapse. These findings demonstrate that precise tuning of membrane surface states through GA-induced sealing provides a robust mechanism for stabilizing MO-DOTAP nanoassemblies under thermal stress.