RETRACTED: Liposomes: Structure, Biomedical Applications, and Stability Parameters With Emphasis on Cholesterol

Abstract

Liposomes are essentially a subtype of nanoparticles comprising a hydrophobic tail and a hydrophilic head constituting a phospholipid membrane. The spherical or multilayered spherical structures of liposomes are highly rich in lipid contents with numerous criteria for their classification, including structural features, structural parameters, and size, synthesis methods, preparation, and drug loading. Despite various liposomal applications, such as drug, vaccine/gene delivery, biosensors fabrication, diagnosis, and food products applications, their use encounters many limitations due to physico-chemical instability as their stability is vigorously affected by the constituting ingredients wherein cholesterol performs a vital role in the stability of the liposomal membrane. It has well established that cholesterol exerts its impact by controlling fluidity, permeability, membrane strength, elasticity and stiffness, transition temperature (Tm), drug retention, phospholipid packing, and plasma stability. Although the undetermined optimum amount of cholesterol for preparing a stable and controlled release vehicle has been the downside, but researchers are still focused on cholesterol as a promising material for the stability of liposomes necessitating explanation for the stability promotion of liposomes. Herein, the prior art pertaining to the liposomal appliances, especially for drug delivery in cancer therapy, and their stability emphasizing the roles of cholesterol.

Methods of Liposomes Preparation: Formation and Control Factors of Versatile Nanocarriers for Biomedical and Nanomedicine Application

“…This increase in the mechanical rigidity results is important for the liposome stability and prevents its interaction with proteins (such as transferrin, albumin, and high-density lipoproteins), thus avoiding a possible reduction of their performances [ 34 , 35 ]. Moreover, the ability of the cholesterol to control the phospholipid packing, membrane fluidity, and the liposomes’ surface charge, produces an effect also on the liposome size, final morphology, and encapsulation efficiency [ 50 ]. Due to its low, flexible, hydrophobic ring structure, cholesterol can interact (through hydrophobic interactions and cooperative hydrogen bonds) with the phospholipid hydrophobic acyl chains, while its presence stabilizes the straight-chain arrangement of saturated fatty acids (through the van der Waals interactions) [ 50 , 51 ].…”

“…Moreover, the ability of the cholesterol to control the phospholipid packing, membrane fluidity, and the liposomes’ surface charge, produces an effect also on the liposome size, final morphology, and encapsulation efficiency [ 50 ]. Due to its low, flexible, hydrophobic ring structure, cholesterol can interact (through hydrophobic interactions and cooperative hydrogen bonds) with the phospholipid hydrophobic acyl chains, while its presence stabilizes the straight-chain arrangement of saturated fatty acids (through the van der Waals interactions) [ 50 , 51 ]. Recent results evidenced that the inclusion of cholesterol in liposomes causes a sensitive increase of the incorporation efficiency of retinol, as well as an increase of the mean size and the colloidal stability of the liposome nanocarriers [ 51 ].…”

Advances in Nanoliposomes for the Diagnosis and Treatment of Liver Cancer

“…Liposomes are prone to degradation through hydrolysis and oxidation, which is due to their inherent instability. 12 Therefore, adjusting the structure of liposomes, controlling the drug loading and drug release rate, overcoming the rapid clearance of liposomes, and increasing the residence time of liposomes in tissues will accelerate their clinical applicability. 148 To this end, this paper makes the following recommendations for the future use of liposomal drugs.…”

“… 11 The unique properties of liposomes, including their biocompatibility, biodegradability, amphiphilic nature, low toxicity, non-ionicity, sustained release, and ability to be actively targeted, have provided many biomedical opportunities, especially for drug delivery. 12 Liposomes can encapsulate drugs to prevent degradation by the immune system, and are highly biocompatible and effectively targeted. As a chemotherapeutic drug delivery system and gene or immunotherapy tools, liposomes enhance the safety of vector systems, the expression of therapeutic proteins, and the silencing of disease-causing genes.…”

Gelatin Coating for the Improvement of Stability and Cell Uptake of Hydrophobic Drug-Containing Liposomes

“…Liposomes can encapsulate both hydrophobic and hydrophilic drugs owing to their amphipathic properties, and the surface of liposomes can be modified using functionalized lipids [ 1 , 2 ]. The poor physical stability of liposomes has been known to limit their wide application because it leads to the rapid aggregation and combination of membrane bilayers [ 3 ]. To enhance the stability of liposomes, polyethylene glycol (PEG), a synthetic polymer, is used to coat their surfaces.…”