Polymersome
Preparation
Several different morphologies of the block copolymer used to create the polymersome have been used. The most frequently used are the linear diblock or triblock copolymers. In these cases, the block copolymer has one block that is hydrophobic; the other block or blocks are hydrophilic. Other morphologies used include comb copolymers, where the backbone block is hydrophilic and the comb branches are hydrophobic, and dendronized block copolymers, where the dendrimer portion is hydrophilic.
In the case of diblock, comb and dendronized copolymers the polymersome membrane has the same bilayer morphology of a liposome, with the hydrophobic blocks of the two layers facing each other in the interior of the membrane. In the case of triblock copolymers the membrane is a monolayer that mimics a bilayer, the central block filling the role of the two facing hydrophobic blocks of a bilayer.
In general they can be prepared by the methods used in the preparation of liposomes. Film rehydration, direct injection method or dissolution method.
Uses
Polymersomes that contain active enzymes and that provide a way to selectively transport substrates for conversion by those enzymes have been described as nanoreactors.
Polymersomes have been used to create candidate controlled release drug delivery systems[clarification needed].
Similar to coating liposomes with polyethylene glycol, polymersomes can be made invisible to the immune system if the hydrophilic block consists of polyethylene glycol. Thus, polymersomes are useful carriers for targeted medication.
For in vivo applications, polymersomes are de facto limited to the use of FDA-approved polymers as most pharmaceutical firms are unlikely to develop novel polymers due to cost issues. Fortunately there are a number of such polymers available, with varying properties, including:
Hydrophilic blocks
Poly(ethylene glycol) (PEG/PEO)
Poly(2-methyloxazoline)
Hydrophobic blocks
Polydimethylsiloxane (PDMS)
Poly(caprolactone (PCL)
Poly(lactide) (PLA)
Poly(methyl methacrylate) (PMMA)
If enough of the block copolymer molecules that make up a polymersome are cross-linked, the polymersome can be made into a transportable powder.
Polymersomes can be used to make an artificial cell if hemoglobin and other components are added. The first artificial cell was made by Thomas Chang.
See also
Cell (biology)
Liposome
Polymer
Copolymer
Artificial cell
References
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^ Circulation times of PEGylated vesicles: Bringing together biology and polymer physics. Photos P, Parthasarathy R, Discher B, Discher D E, Abstracts, 36th Middle Atlantic Regional Meeting of the American Chemical Society, Princeton, NJ, United States, June 8-11 (2003), 175. Publisher: American Chemical Society, Washington, D. C
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^ http://science.nasa.gov/headlines/y2003/29may_polymersomes.htm
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