Lipid based drug delivery systems for oral, transdermal and parenteral delivery: Recent strategies for targeted delivery consistent with different clinical application

Lipid based drug delivery systems (LBDDS) are valuable and biocompatible nano-carriers for the vehiculation and potential delivery of various hydrophilic, hydrophobic, or amphiphilic compounds. LBDDS have the advantage of targeted drug delivery, as free drugs may have poor targeting, higher systemic toxicity, and possibilities of drug resistance. There is various type of lipid carrier systems for drug delivery based on the properties of drugs and clinical applications; nanoemulsion, microemulsion, lipid vesicles, and lipid nanoparticles. The era of targeted drug delivery is advancing from the superficial convention vesicles to the second generation of LBDDS by modulating the surface chemistry through modifying/surface functionalizing the lipid layer composition. The surfaces of lipid vehicles have been modified with small molecules, antibodies, peptides, and enzymes for targeted drug delivery and reduced toxicity. In this regard, polyethylene glycosylation (PEGylation) on the lipid surface was the first novel approach that improves blood circulation time and curtails opsonin resistance and clearance. However, multi-drug and multi-receptor strategies in the targeted-liposomal approach may be an innovative pathway to overcoming drug resistance while treating certain tumors. Several second-generation conventional drug delivery systems among liposomal formulations are at various stages of clinical trials. This review recapitulates the types of lipid formulations, characterization, and their applications in clinical aspects. Additionally, discuss the strategies for enhancement of disease targeting by surface functionalization with various entities to improve the drug delivery system.