Acyclovir Solid Lipid Nanoparticles for Skin Drug Delivery: Fabrication, Characterization and In vitro Study

Prior research has shown that solid lipid nanoparticles (SLNs) offer a promising route for enhancing drug delivery to the skin. It was already known that conventional formulations often struggle with poor bioavailability and inconsistent release profiles. That uncertainty drove the exploration of alternative lipid matrices and surfactants to improve nanoparticle stability and performance. No prior work had resolved the optimal composition for acyclovir-loaded SLNs using fractionated coconut oil. Existing studies have demonstrated that lipid-based systems can improve drug solubility and permeation. However, the specific impact of different lipid ratios and surfactants on nanoparticle morphology remained unclear. This gap motivated the investigation into how varying concentrations of Glyceryl mono stearate (GMS) and Lipoid S75 affect SLN fabrication. The goal was to identify a formulation that balances particle size, zeta potential, and drug entrapment efficiency.

The aim of this study was to develop and characterize acyclovir-loaded solid lipid nanoparticles using fractionated coconut oil as the lipid matrix. The specific problem addressed was the need for a stable and efficient delivery system for acyclovir in dermatological applications. The motivation stemmed from the limitations of conventional formulations in achieving controlled drug release and skin permeation. Researchers focused on comparing two batches using different surfactants—GMS and Lipoid S75. The study aimed to assess how these surfactants influence nanoparticle characteristics such as particle size and zeta potential. By varying concentrations and ratios, the team sought to optimize formulation design for drug delivery. The in vitro drug release was evaluated using dialysis membrane and wistar rat skin models. The ultimate goal was to identify a formulation with superior stability and performance for topical drug delivery.

The study utilized high-pressure hot-homogenization to fabricate acyclovir-loaded solid lipid nanoparticles. Fractionated coconut oil served as the lipid matrix, with Glyceryl mono stearate (GMS) and Lipoid S75 as surfactants. Two batches were prepared with different concentrations of these surfactants. The formulations were evaluated using X-ray diffraction (XRD) to assess crystallinity. Fourier transform infrared spectroscopy (FTIR) was employed to confirm the absence of chemical interactions. Particle size and distribution were measured using master sizer and zeta sizer analyses. Transmission electron microscopy (TEM) was used to observe nanoparticle morphology. Zeta potential was determined to evaluate colloidal stability. In vitro drug release was studied using dialysis membrane and wistar rat skin models to simulate topical delivery.

The best formulation from the GMS batch (GNE5) exhibited a zeta potential of -2.62mV, indicating poor colloidal stability due to high viscosity. In contrast, the Lipoid S75 batch (LS4) showed a zeta potential of 23.23mV, within the recommended range for stable dispersions. The LS4 formulation had a narrow particle size distribution of 53.46nm and a uniformity value of 14.1. The smallest distribution was observed at 6.8, 14.5, and 139.1nm for LS4. SLN dispersions were found to have an average particle size in the nano range. Small particle size correlated with higher drug entrapment efficiency and controlled in vitro release. The Lipoid S75 and Pluronic F68 nanoparticles outperformed conventional GMS and Tween 80 formulations in terms of particle size and stability. These findings suggest that Lipoid S75 is a superior surfactant for acyclovir-loaded SLNs.

The authors propose that Lipoid S75-based formulations offer better stability and drug release profiles compared to GMS-based ones. They suggest that the zeta potential of 23.23mV in LS4 is optimal for colloidal stability. The narrow particle size distribution of 53.46nm indicates uniformity in the LS4 formulation. The in vitro drug release study supports the potential of LS4 for controlled topical delivery. The authors note that the high viscosity of GNE5 led to lower zeta potential and poor performance. They propose that particle size and entrapment efficiency are critical for effective drug delivery. The study highlights the importance of surfactant choice in nanoparticle formulation. The findings suggest that Lipoid S75 is a suitable alternative to conventional surfactants in SLN development.