(558j) Preparation, Characterization and Self-Assembly of Solid Lipid Nanoparticles

Due to their availability to use in both scientific studies and medical and technological applications, nanoparticles have been driving much attention in the recent years. Nanoparticles can be synthesized by using a variety of constituents, primarily metallic, polymer, composite and lipid. The size, shape and the surface functionality as well as the materials constituting the nanoparticles depends on and are relative to the target area. Solid lipid nanoparticles (SLNs), which are prepared by using various physiologically related lipids, emulsifiers and water, are started to be used as an alternative nanocarrier in 1990s [1]. Due to their high biocompatibility, stability and availability/efficiency to encapsulate various active materials, SLNs are distinguished from other alternatives in the use of pharmaceutics and biomedical applications. Since possessing adjustable release kinetics depend on the synthesis method and biocompatible raw material, SLNs are ideal to use in body for different purposes and with various administration routes. Different methodologies exist for the production of finely dispersed solid lipid nanoparticles which are high pressure homogenization, microemulsion based preparation, high shear homogenization and preparation by solvent emulsification [2]. Moreover, spray drying and lyophilization methods can be used to obtain dry SLNs. In our study, 12 types of SLNs with different size and formulations were synthesized by using “microemulsion method”, because of its user friendly nature like avoidance of high pressure, temperature, organic solvents and formation of monodisperse particles. Various techniques have been used in the characterization of SLNs such as Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). In addition, surface charge density of each particle was obtained. After the synthesis of SLNs, encapsulation and release studies were performed by using ascorbic acid (AA) and methylene blue (MB) as model molecules. AA was loaded into the SLNs during the preparation of microemulsion, whereas MB was entrapped on the surface of SLNs via electrostatic interaction dominantly. Although the performance of the synthesized SLNs shows some variations, the optimum result is obtained for SLN to whom 95% of the AA can be loaded and 90% of the drug was released within 24 hours. It was observed that, MB can be entrapped on the surface of SLNs with an efficiency of ~90%. The release kinetic was directly proportional to the surface charge density of the particles.

As well as SLNs are being used in several areas including medical and pharmaceutical individually, more versatile systems can be established via self-assembly of SLNs. These self-assembled structures, independent from their single form, possess attractive properties such as high stability, enhanced functionality and increased loading capacity. In this study, as the following step, novel self-assembled forms with SLNs were prepared by using layer-by-layer method. The performance of establishing the layers was monitored by measuring the change of zeta-potential values. Also the self-assembled structures were visualized with SEM. Due to several advantageous properties such as being composed of physiologically related lipids, possessing properties like small and adjustable structure, high surface area, enhanced stability, stimuli-responsivity and increased encapsulation efficiency, these unique systems will be an ideal alternative to the conventional nanocarriers, which are especially used in pharmaceutical and biomedical applications. After all, this study not only develops an understanding but also it can be considered as an important step in the improvement of controlled drug delivery systems.

References

[1] Müller, R.H. and Weyhers, H. 1996. “Cytotoxicity of Magnetite-Loaded Polylactide, Polylactide/Glycolide Particles and Solid Lipid Nanoparticles”, International Journal of Pharmaceuticals, 138, 85-94.

[2]  Wissing, S.A., Kayser, O. and Müller, R.H. 2003. “Solid lipid nanoparticles for parenteral drug delivery”, Advanced Drug Delivery Reviews, 56, 1257 – 1272.