Water-soluble stimuli-responsive vesicles from peptide-based diblock copolymers

Polypeptide secondary structure controls the dimensions of aggregates formed from a polybutadieneb-poly(L-glutamic acid) diblock copolymer after direct dissolution into water. The hydrodynamic radius (RH) of these aggregates (even at high NaCl concentrations) were found to correlate (see picture) with a transition from a compactly folded α-helical poly(L-glutamic acid) block at low pH to an extended random coil conformation at basic pH

From supramolecular polymersomes to stimuli-responsive nano-capsules based on poly(diene-b-peptide) diblock copolymers

This paper discusses the self-assembly of block copolymers into vesicular morphology. After a brief state of art of the field, a system based on an amphiphilic poly(butadiene)- b-poly(-L-glutamic acid) (PB- b-PGA) diblock copolymer in aqueous solution is discussed in detail. The aggregation behavior of this block copolymer has been investigated by means of fluorescence spectroscopy, dynamic (DLS) and static (SLS) light scattering as well as transmission electron microscopy (TEM). The diblock copolymer was found to form well-defined vesicles in water. The size of these so-called polymersomes or peptosomes could be reversibly manipulated as a function of both pH and ion strength. Depending on the pH of the aqueous solution, the hydrodynamic radii of these vesicles were found to vary from 100 nm to 150 nm. By cross-linking the 1,2-vinyl double bonds present in the polybutadiene block, the ability to transform a transient supramolecular self-organized aggregate into a permanent "shape-persistent stimuli-responsive nanoparticle" has been demonstrated

Materials Science Pulsating vesicles

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Temperature responsive poly(trimethylene carbonate)-block-poly(L-glutamic acid) copolymer: polymersomes fusion and fission

We have reported on a new type of thermotropic transition in synthetic diblock copolymer vesicles. Vesicles were self-assembled from a well-defined poly(trimethylene carbonate)-b-poly(L-glutamic acid) (PTMC22-b-PGA14, M(n) = 4.05*10(3) g mol(-1)) copolymer. PTMC(22) is a semi-crystalline hydrophobic block with a melting endotherm observed at 37 degrees C in the bulk copolymer and at 34-35 degrees C in the vesicular dispersions. This temperature transition, as observed by mDSC in the aqueous vesicular dispersions, arose from a variation of the PTMC chain packing inside the vesicular bilayer. A large range of vesicle sizes, from 100 nm to 5 mu m, was accessible by varying the experimental conditions to prepare the vesicles. Large vesicles were more sensitive to the melting transition due to a low membrane curvature and high hydrophobic block interactions. By many aspects, this transition presented strong analogies with the gel-to-liquid crystalline phase transition observed in liposomes. Vesicle budding and fission occurred when temperature was increased above the PTMC melting temperature and fusion events were observed when temperature was decreased. The fission process was certainly due to the creation of an excess area upon heating whereas fusion is due to membrane defects arising from variation in PTMC membrane packing. As a consequence, the size of the vesicles was found correlated to the crystalline state of the PTMC chains, its variation being fully reversible with the temperature