slns

Solid lipid nanoparticles (SLNs) are submicron carriers made from solid lipids stabilized by surfactants. The lipid core remains solid at body temperature, enabling encapsulation of lipophilic drugs and protection from degradation. Particle sizes typically range from 50 to 1000 nanometers. Developed in the 1990s as an alternative to emulsions and liposomes, SLNs aim to improve stability, drug protection, and controlled release.

SLNs use lipids solid at physiological temperatures, such as glyceryl behenate or glyceryl monostearate, with surfactants like Tween or poloxamer. Production methods include high-pressure homogenization, ultrasonication, and hot or cold processing. The crystalline state of the lipid matrix affects drug loading and release; polymorphism can lead to drug expulsion during storage if the matrix becomes too crystalline.

Applications include oral, parenteral, topical, and ocular drug delivery, as well as dermatology and vaccines. Advantages are biocompatibility, protection of labile drugs, reduced leakage, and potential for targeted delivery through surface modification. Limitations include relatively low loading for hydrophilic drugs, possible lipid polymorphism, and manufacturing challenges for scale-up.

Characterization commonly covers particle size and distribution, zeta potential, entrapment efficiency, and drug loading, with techniques such as differential scanning calorimetry and X-ray diffraction used to assess crystallinity. Electron microscopy can confirm morphology. Safety depends on lipid and surfactant choice; SLNs are generally regarded as biocompatible, but regulatory considerations apply to specific formulations.