Nanostructured Lipid Carriers in Drug Targeting: Characterization, Patents, and Recent Innovations

The second-generation lipid-based nanocarrier system, nanostructured lipid carriers (NLCs), has received much attention due to their distinct properties that enable them to address the various limitations that afflict both solid lipid nanoparticles and the conventional delivery system. The special structure (solid lipids/liquid lipids blend) of NLCs provides a better encapsulation, stability, controlled release, and biocompatibility of drugs, therefore, leading to the effective transportation of hydrophilic and lipophilic drugs. This review briefly examines the design methods, formulation strategies, and other more sophisticated characterization methods, such as traditional characterization (e.g., dynamic light scattering (DLS) and X-ray diffraction) and new methods (e.g., cryo-EM and small-angle X-ray scattering (SAXS) that provide an effect on particle size, lipid crystallinity, and release kinetics. The review notes Process Analytical Technology (PAT) and its ability to aid the real-time monitoring and scale-up production of NLC products. Recent dosage forms that have been used as therapeutic agents that involve the use of NLCs are critically discussed, such as the following routes of administration: oral, transdermal, nasal, ocular, pulmonary, and targeted delivery. Moreover, we will review how NLCs can serve to improve bioavailability, enhance patient compliance, and provide sitespecific action of drug delivery. A recent analysis of patents is reviewed to identify where innovative space is being created regarding surface functionalization, hybrid systems, and combinatorial therapies, as well as the challenges faced, such as regulatory implications and translational opportunities. This work provides a summary of the formulation science, characterization methods, and patent data to offer an overview of the current state and prospective future work of NLCs with respect to drug targeting, delivery, and the nanomedicine field.