PEGylated Liposomes

PEGylation is a technique that is used to coat the surface of different NDDSs. It may be done covalently or noncovalently with hydrophilic, linear, ionic, non-toxic ether diol polymer such as PEG (polyethylene glycol) to improve their pharmacokinetic as well as pharmacodynamic behaviour. PEG and its several derivatives that possess hydrophilic PEG chains and neutral polymeric nature can produce a protective layer on the surface that prevents interaction with antibodies, therefore, decreasing the immunogenic effects and escaping phagocytosis. The hydration capacity of PEG produces a hydration shield around the PEG-linked DDSs and improves the solubility in serum and blood to protect rapid glomerular clearance and enzymatic degradation. When compared with the conventional liposomes, PEGylated liposomes had improved blood circulation time, higher drug bioavailability, improved drug delivery at the target site as well as bypass reticuloendothelial systems (RES). The PEG chain's shape, lenght, weigth, types of bond and density would primarily affect PEGylated liposomes efficiency, and currently, researchers have been working relentlessly toward the selection of PEG derivatives and PEG conjugation methodologies. This is to establish the best PEGylation stratagem for a specific biomedical application. The objectives of the present context will be to explicate the principles and strategies of PEGylation, PEG derivatives and the modification used in PEGylated liposomes, their takeup and clearence, the application in various diseases' drug targeting, in herbal medicines delivery as well as the challenges and future approaches to improve PEGylated liposomes in the clinical application of therapeutic purpose. This chapter also discusses the benefits and application of self-emulsifying drug delivery systems (SEDDS) in herbal medicine.