Question

In an experiment, let us say you plan to use liposomes in an attempt to deliver drugs to fat or muscle cells. Is there a method in which you might be able to construct the liposome to increase its target specificity? explain with reference (15points)

Answer 1

Liposomes are a novel drug delivery system (NDDS), they are vesicular structures consisting of bilalyers which form spontaneously when phospholipids are dispersed in water. They are microscopic vesicles in which an aqueous volume is entirely enclosed by a membrane composed of lipid bilayers. Liposomes are colloidal spheres of cholesterol non-toxic surfactants, sphingolipids, glycolipids, long chain fatty acids and even membrane proteins and drug molecules or it is also called vesicular system. It differs in size, composition and charge and drug carrier loaded with variety of molecules such as small drug molecules, proteins, nucleotides or plasmids etc. Few drugs are formulated as liposomes to improve their therapeutic index

The therapeutic efficacy of the drug molecule is governed by the stability of the liposomes involving manufacturing steps, storage and delivery.Phospholipids are chemically unsaturated fatty acids, prone to oxidation and hydrolysis, which may alter the stability of the drug product. pH, ionic strength, solvent system and buffered species also play a major role in maintaining a liposomal formulation.

To improve liposome stability and enhance their circulation times in the blood, sterically-stabilized liposomes were introduced. The hydrophilic polymer, polyethylene glycol (PEG), has been shown to be the optimal choice for obtaining sterically-stabilized liposomes...The establishment of a steric barrier improves the efficacy of encapsulated agents by reducing in vivo opsonization with serum components, and the rapid recognition and uptake by the RES(reticuloendothelial system). This not only reduces the elimination of drugs by prolonging blood circulation and providing accumulation at pathological sites, but also attenuates side effects...Steric stabilization strongly influences the pharmacokinetics of liposomes...with reported half-lives varying from 2 to 24 h in rodents (mice and rats) and as high as 45 h in humans, depending on the particle size and the characteristics of the coating polymer...While coating liposomes with PEG results in prolonged circulation times, there can be an offsetting reduction in the ability to interact with the intended targets

Reference is taken from ncbi.nlm.nih.gov and omiconline.org