118: Impact of Oscillating Magnetic Fields (OMF)-Based Supercooling Treatment on the Physicochemical Properties of Solid Lipid Nanoparticles (SLNs) Using Cocoa Butter and Soy Lecithin

Introduction

Solid lipid nanoparticles (SLNs) are emerging as effective delivery systems in food and pharmaceutical applications. Their physicochemical properties are influenced by processing conditions. Oscillating magnetic fields (OMF)-based supercooling, a technique that prevents ice crystallization under freezing points, has been proposed to enhance the stability and properties of SLNs. This study investigated the effect of OMF-based supercooling treatment on SLNs.

Methods

5% cocoa butter and 0.2% soy lecithin were combined and then sonicated at 60% amplitude for 5 minutes to form a nanoemulsion. The resulting nanoemulsion was subjected to different cooling treatments for 20 hours to produce SLNs: supercooling at -9°C with OMF (15 mT, 5 Hz), frozen without OMF (-9°C, FR-SLNs), room temperature (20°C, RT-SLNs), and refrigerated (4°C, RF-SLNs). The physicochemical properties of the generated SLNs, including phase separation, particle properties, and solid lipid content, were assessed using dynamic light scattering (DLS), time-domain nuclear magnetic resonance (TD-NMR).

Results

The proprietary OMF system was designed to generate a uniform oscillating magnetic field at a strength of 15 mT and a frequency of 5 Hz. Supercooling treatment at -9°C using OMF preserved the supercooled state of SLNs for 20 hours by preventing ice nucleation. FR-SLNs showed phase separation upon thawing, while SC-SLNs, RF-SLNs, and RT-SLNs remained stable. Regarding particle characteristics, RF-SLNs showed a significant increase in size (p < 0.05), while SC-SLNs and RT-SLNs remained stable without changes in particle size. The polydispersity index values for SC-SLNs, RT-SLNs, and RF-SLNs ranged between 0.15 and 0.25. Zeta potential values were similar across all groups, ranging from -51.7 mV to -52.7 mV. TD-NMR analysis revealed that SC-SLNs exhibited the highest solid fat content (SFC) at 7.1±0.2%, significantly higher than RF-SLNs (6.5±0.1%) and RT-SLNs (0.2±0.1%). These findings indicate that SC-SLNs exhibit enhanced stability at -9°C without phase separation, as well as a higher SFC compared to other treatment groups.

Significance

This study demonstrates that OMF-based supercooling enhances SLN stability, solid fat content, and physicochemical properties, offering a promising approach for improving SLNs in applications such as drug delivery, food, and cosmetics.

Authors: Heejin So, Soojin Jun