Adapting liposomes for oral drug delivery

Abstract

Liposomes mimic natural cell membranes and have long been investigated as drug carriers due to excellent entrapment capacity, biocompatibility and safety. Despite the success of parenteral liposomes, oral delivery of liposomes is impeded by various barriers such as instability in the gastrointestinal tract, difficulties in crossing biomembranes, and mass production problems. By modulating the compositions of the lipid bilayers and adding polymers or ligands, both the stability and permeability of liposomes can be greatly improved for oral drug delivery. This review provides an overview of the challenges and current approaches toward the oral delivery of liposomes.

Liposomes for Enhanced Bioavailability of Water-Insoluble Drugs: In Vivo Evidence and Recent Approaches

“…In the same manner as various nanoparticles, it is difficult for the intact liposomes to permeate freely across intestinal barriers due to their relatively large size [52]. One of the biggest limitations of liposomes as a drug delivery system has been the difficulty in continuous mass production and quality control because the liposomal system is very complex [8,14]. Lipid degradants such as lysolipids can be formed during manufacturing or storage.…”

“…The mechanisms of oral delivery of liposomes have not been fully understood yet, despite the significant number of in vitro studies on the dissolution and permeation enhancement [8]. According to a meta-analysis performed in 2015, liposomes clearly improved solubility and permeability, showing a 127.4% and 59.5% increase, respectively [10].…”

“…Liposomes, vesicles enclosed by phospholipid bilayers, can solubilize water-insoluble drugs into the lipid domain of the liposomal membrane [5,7]. In addition to their solubilizing capacity and biocompatibility, the structural and compositional similarity of liposomes with bio-membranes has also encouraged their application for non-invasive oral delivery of poorly-permeable drugs [8].…”

“…also encouraged their application for non-invasive oral delivery of poorly-permeable drugs [8]. However, there have been several drawbacks to be overcome, such as instability in the GI tract and poor permeability across the intestinal epithelia because of liposomes' relatively large size [8]. Moreover, it seemed that liposomal oral delivery was faltering during 1980s due to some disappointing results for insulin [9].…”

“…However, it is discouraging that most of this research has been in vitro studies only and there have not been many water-insoluble drugs with in vivo data. The present review focused on the in vivo evidence for the improved BA of water-insoluble drugs using liposomes to resolve doubts raised concerning liposomal oral delivery and attempted to provide insight by highlighting the approaches used for in vivo achievements.Pharmaceutics 2020, 12, 264 2 of 30 However, there have been several drawbacks to be overcome, such as instability in the GI tract and poor permeability across the intestinal epithelia because of liposomes' relatively large size [8]. Moreover, it seemed that liposomal oral delivery was faltering during 1980s due to some disappointing results for insulin [9].…”