SOLID LIPID NANOPARTICLES IN CONTROLLED DRUG DELIVERY

Solid Lipid Nanoparticles (SLNs) have attracted growing interest in pharmaceutical research over the past three decades. Their capacity to carry both lipophilic and moderately hydrophilic drugs, shield sensitive molecules during circulation, and navigate biological barriers such as the blood-brain barrier (BBB) has established them as one of the more versatile nanocarrier platforms available today. First developed in the early 1990s as a practical alternative to liposomes and polymeric nanoparticles, SLNs employ a solid lipid core stabilised by biocompatible surfactants to achieve controlled, sustained, and targeted drug release. This review examines the structural principles and compositional design of SLNs, the principal preparation methods, standard physicochemical characterisation techniques, and their therapeutic applications across multiple disease areas. Particular attention is given to current research directions including stimuli-responsive formulations, nucleic acid delivery, theranostic systems, and the integration of machine learning into formulation development. Original contributions from the authors addressing dual stimuli-responsive SLNs, peptide-functionalised active targeting, intranasal brain delivery, and AI-assisted manufacturing are also presented. Together, these developments illustrate the ongoing transition of SLN technology toward clinical translation.