Solid Lipid Nanoparticles: A Review on Formulation Methods, Evaluation Parameters and Pharmaceutical Applications

Solid lipid nanoparticles are advanced lipid-based nanocarrier systems designed to address the major drawbacks of conventional dosage forms, including low bioavailability, poor stability and lack of controlled drug release. These nanocarriers consist of biocompatible solid lipids stabilised by appropriate surfactants and remain in the solid state at both ambient and physiological temperatures. Solid lipid nanoparticles can efficiently incorporate hydrophilic as well as lipophilic drugs while maintaining low toxicity and excellent biocompatibility. By integrating the beneficial properties of polymeric nanoparticles and lipid emulsions, these systems offer enhanced physical stability, sustained and controlled drug release and improved therapeutic performance. In addition, solid lipid nanoparticles protect incorporated drugs from chemical degradation, thereby extending shelf life compared with conventional delivery systems. Their compatibility with large-scale manufacturing processes and ability to enhance patient compliance have contributed to their growing significance in pharmaceutical research. The use of biodegradable lipids and the elimination of harmful organic solvents further improve the safety of these nanocarriers for clinical use. In recent years, solid lipid nanoparticles have been widely explored for the delivery of poorly soluble drugs, peptides, proteins and macromolecules owing to their adaptability and favourable safety characteristics. Moreover, these systems exhibit promising potential in targeted drug delivery, sustained release formulations and enhanced drug absorption. This review focuses on the formulation aspects, methods of preparation, advantages, disadvantages, limitations and pharmaceutical applications of solid lipid nanoparticles.