Polymeric micelles in pharmacy
Polymers can be utilized as investigative nanobiomaterials which can be engineered for the delivery system of different kinds of drugs including genes, and peptides [25, 26]. Polymeric nanoparticles or micelles can be easily formulated and converted to be nanosized entities with various designs in different sizes of 1-50 nm. Structural modification in terms of either simple conjugation or complex reaction can be initiated in different kinds of Polymers for the purpose of targeting and imaging of cancer cells .
Among those polymers, poly(lactic-co-glycolic) acid (PLGA),chitosan and PEG are extensively and enormously used as biocompatible polymers for translational medicine [28, 29].Due to its biocompatibility PLGA is one of the most widely used polymers and was approved by US FDA and European Medicine Agency (EMA). PLGA-based nanoparticles have the huge potential to improve drug efficacy via target specificity of nanoplatforms in vitro and in vivo.PEG is the another most investigative polymer which is vastly used for the surface modification of nanoparticles .
Nanoparticles can be usually engineered with different kinds of targeting ligands conjugated with PEG.By the method of pegylation PEG can contribute enotmosly to make nanoparticles sterically stable for the prolonged period during circulation in the blood after administration . Most of the amphiphilic block copolymers assemble into nanoscopic supramolecular core-shell to form 'polymeric micelles' which are usually less than100 nm and their hydrophilic surface protects nonspecific uptake by RES(Reticuloendothelial system). Micelles in solution are aggregated in which the component molecules are generally distributed in a spheroidal structure where hydrophobic groups shielded from water by a surrounding of hydrophilic groups .
Fig. 6 Structure of block copolymer micelles(30)
These dynamic systems are used for the systemic delivery of water-insoluble drugs. Drugs or contrast agents may be trapped physically within the hydrophobic cores or can be linked covalently to component molecules of the micelle. Polymeric micelles have proved an excellent novel drug delivery system due to high and versatile loading capacity, stability in physiological conditions, slower rate of dissolution, high accumulation of drug at target site and possibility of functionalization of end group for conjugation of targeting ligands.
29. Maeda H, Wu J, Sawa T, Matsumura Y, Hori K. Tumor vascular permeability and the EPR effect in macromolecular therapeutics: a review. J Control Release. 2000;65:271-84. doi: 10.1016/S0168-3659(99)00248-5. [PubMed] [Cross Ref]