Dual effect of thiol addition on fluorescent polymeric micelles: ON-to-OFF emissive switch and morphology transition

YesThe morphology transition from micelles to vesicles of a solution-state self-assembled block copolymer, containing a fluorescent dye at the core–shell interface, has been induced by an addition–elimination reaction using a thiol, and has been shown to be coupled to a simultaneous ON-to-OFF switch in particle fluorescence.EPSRC and the IAS at the University of Warwic

Peptide based amphiphiles

Contains fulltext : 13849.pdf (publisher's version ) (Open Access

Characterisation of aggregates of cyclodextrin-drug complexes using Taylor Dispersion Analysis

There is a need to understand the nature of aggregation of cyclodextrins (CDs) with guest molecules in increasingly complex formulation systems. To this end an innovative application of Taylor dispersion analysis (TDA) and comparison with dynamic light scattering (DLS) have been carried out to probe the nature of ICT01-2588 (ICT-2588), a novel tumor-targeted vascular disrupting agent, in solvents including a potential buffered formulation containing 10% hydroxypropyl-β-cyclodextrin. The two hydrodynamic sizing techniques give measurement responses are that fundamentally different for aggregated solutions containing the target molecule, and the benefits of using TDA in conjunction with DLS are that systems are characterised through measurement of both mass- and z-average hydrodynamic radii. Whereas DLS measurements primarily resolve the large aggregates of ICT01-2588 in its formulation medium, methodology for TDA is described to determine the size and notably to quantify the proportion of monomers in the presence of large aggregates, and at the same time measure the formulation viscosity. Interestingly TDA and DLS have also distinguished between aggregate profiles formed using HP-β-CD samples from different suppliers. The approach is expected to be widely applicable to this important class of drug formulations where drug solubility is enhanced by cyclodextrin and other excipients

Preparation and development of block copolypeptide vesicles and hydrogels for biological and medical applications

There have been many recent advances in the controlled polymerization of α-amino acid-N-carboxyanhydride (NCA) monomers into well-defined block copolypeptides. Transition metal initiating systems allow block copolypeptide synthesis with excellent control over number and lengths of block segments, chain length distribution, and chain-end functionality. Using this and other methods, block copolypeptides of controlled dimensions have been prepared and their self-assembly into organized structures studied by many research groups. The ability of well-defined block copolypeptides to assemble into supramolecular copolypeptide vesicles and hydrogels has led to the development of these materials for use in biological and medical applications. These assemblies have been found to possess unique properties that are derived from the amino acid building blocks and ordered conformations of the polypeptide segments. Recent work on the incorporation of active and stimulus-responsive functionality in these materials has tremendously increased their potential for use in biological and medical studies

Hierarchy of hybrid materials — the place of inorganics-in-organics in it, their composition and applications

Hybrid materials, or hybrids incorporating both organic and inorganic constituents, are emerging as a very potent and promising class of materials due to the diverse, but complementary nature of the properties inherent of these different classes of materials. The complementarity leads to a perfect synergy of properties of desired material and eventually an end-product. The diversity of resultant properties and materials used in the construction of hybrids, leads to a very broad range of application areas generated by engaging very different research communities. We provide here a general classification of hybrid materials, wherein organics–in-inorganics (inorganic materials modified by organic moieties) are distinguished from inorganics–in–organics (organic materials or matrices modified by inorganic constituents). In the former area, the surface functionalization of colloids is distinguished as a stand-alone sub-area. The latter area—functionalization of organic materials by inorganic additives—is the focus of the current review. Inorganic constituents, often in the form of small particles or structures, are made of minerals, clays, semiconductors, metals, carbons, and ceramics. They are shown to be incorporated into organic matrices, which can be distinguished as two classes: chemical and biological. Chemical organic matrices include coatings, vehicles and capsules assembled into: hydrogels, layer-by-layer assembly, polymer brushes, block co-polymers and other assemblies. Biological organic matrices encompass bio-molecules (lipids, polysaccharides, proteins and enzymes, and nucleic acids) as well as higher level organisms: cells, bacteria, and microorganisms. In addition to providing details of the above classification and analysis of the composition of hybrids, we also highlight some antagonistic yin-&-yang properties of organic and inorganic materials, review applications and provide an outlook to emerging trends

Mechanism of nanocapsules formation by the emulsion–diffusion process

International audienceA detailed investigation into the mechanisms of nanocapsule formation by means of the two stages “emulsion–diffusion” process is reported. Such widely used process is still poorly understood. An emulsion of oil, polymer and ethyl acetate is fabricated as a first step; dilution with pure water allows ethyl acetate to diffuse out from the droplets, leaving a suspension of nanocapsules at the end. It has been shown that the size of nanocapsules was related to the chemical composition of the organic phase and the size of primary emulsion through a simple geometrical relationship. As a consequence, most of the properties of the nanocapsules were decided at the emulsification step. The influence of several formulation and processing parameters of the primary emulsion was studied accordingly. The thin polymer membrane of nanocapsules was observed by means of cryo-fracture electron microscopy. Finally two experiments were designed for a mechanistic investigation of the diffusion step. A step-by-step diffusion of the organic solvent takes place by successive partition equilibria of ethyl acetate between the droplets and aqueous phase. A time-resolved experiment shows the fast diffusion (less than 20 ms) related to the small droplet size of the emulsion

Smart hybrid magnetic self-assembled micelles and hollow capsules

Novel magnetic nano-composites are obtained by the self-assembly in water of polypeptide-based di-block copolymers polybutadiene-b-poly(glutamic acid) combined with hydrophobically modified gamma-Fe2O3 nanoparticles. These hybrid supramolecular objects are either filled micelles (3-d) or hollow vesicles with a magnetic membrane (2-d), deformation of which under an applied magnetic field has been evidenced. These nanoparticles are also able to respond to stimuli such as pH and ionic strength due to the presence of the polypeptide block, thus forming what we called multi-responsive nanocapsules. These superparamagnetic hybrid self-assemblies offer attractive potentialities in biomedicine and biotechnology due to their dimensions (0.1-0.5 mu m) small enough to stay for some time in the blood circulation. and due to the properties brought about by the iron oxide nanoparticles: possible manipulation by an external magnetic field gradient, local heating by a radio-frequency field for cancer radio-therapy, labeling of organs to enhance the contrast in Magnetic Resonance Imaging

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