Polyelectrolyte capsules

Figure 5.4 LbL assembly of polyelectrolyte capsule. Alternately charged molecules are added to the template several times, giving species (d).This is followed by dissolution ofthe template (e) leaving the polyelectrolyte capsule. Reproduced with permission from [36],...

Electrostatic self-assembly of polymers in the bulk Polyelectrolyte capsules controlled release vehicles, smart delivery systems 50-500 nm Anal et al., 2008... 

Layer-by-layer electrostatic deposition of biopolymers at interface of emulsion droplets Polyelectrolyte capsules microparticles with novel functionality and triggered release multiple layers around oil droplets exhibiting improved stability towards environmental stresses (temperature, ionic strength, pH, freezing, dehydration) McClements, 2005, 2006 Sanguansri and Augustin, 2006... 

The variety of materials which can be incorporated into polyelectrolyte multilayers makes them attractive to use as biosensors [431], Polyelectrolyte multilayers can also be formed on curved surfaces of small particles [432], After adsorption, the core particle can be chemically dissolved and a hollow polyelectrolyte capsule remains. These capsules are selectively permeable for small molecules like water or certain dyes. The permeability can be tuned externally by varying the ion strength, pH, temperature and solvent nature [433 135], Therefore, it has been suggested to use them as selective membranes for separation, as well as a possible drug delivery system. The adjustment of their size and permeability allows us to exploit them as micro- or nanocontainers for chemical synthesis and crystallization. 

Radtchenko IL, Sukhorukov GB, Leporatti S, Khomutov GB, Donath E, Mohwald H. Assembly of alternated multivalent ion/polyelectrolyte layers on colloidal particles. Stability of the multilayers and encapsulation of macromolecules into polyelectrolyte capsules. Journal of Colloid Interface Science 2000, 230, 272-280. 

Fig. 9 (a-c) Preparation of matrix-type polyelectrolyte capsules templated on CaCC>3 microparticles. (d, e) Scanning microscopy images of the CaCC>3 microparticles and the matrix-type capsules, respectively, (f) Confocal laser scanning microscopy image of the capsules loaded with fluores-cently labeled bovine serum albumin. Adapted from [111, 112]... 

The capsules with a defined shell (so-called hollow multilayered polyelectrolyte capsules) are free-standing LbL films with a peculiar advantage - the ability to uptake the material inside the capsule, in other words to encapsulate it and to control its release by changing the LbL film permeability properties. Macromolecules like proteins have been successfully loaded into polyelectrolyte LbL capsules through pH-controlled and water/ethanol mixture-controlled methods [118, 119], Alternative stimuli could be applied, e.g., a magnetic field [120], This approach consists of destabilization of the LbL membrane, which then becomes more permeable. The capsule is loaded with molecules of interest under destabilized conditions and then the conditions are changed back to the initial ones (under which the LbL shell is stable). 

The matrix polyelectrolyte capsules have high protein-loading capacity, and both the loading and, in principle, the release are driven by electrostatic interaction with polyelectrolytes [111]. Moreover, the loading and release can be controlled by the number of polyelectrolyte adsorption steps [112] as well as by the pore size of the CaCC>3 cores [116],... 

Moya S, Donath E, Sukhorukov GB et al (2000) Lipid coating on polyelectrolyte surface modified colloidal particles and polyelectrolyte capsules. Macromolecules 33 4538 1544... 

Munoz JA, del Pino P, Bedard MF et al (2008) Photoactivated release of cargo from the cavity of polyelectrolyte capsules to the cytosol of cells. Langmuir 24 12517-12520... 

Mechanical Properties of Freestanding Polyelectrolyte Capsules a Quantitative Approach Based on Shell Theory... 

Amines have also been microencapsulated within small cellulosic or polyelectrolyte capsules. This is a method for keeping the amine separate from the epoxy resin during storage. When the user decides to initiate cure, the capsules are broken, usually in the application process, and the amine is free to react with the epoxy resin. A successful example of this type of product is an epoxy adhesive that can be preapplied to machine screw threads. When the screw is ultimately threaded into place, the shearing action causes the capsule to break. Bond strengths are generally low for this type of adhesive, but this may not be important in certain applications. 

Polyelectrolyte (capsule core) Counterion (outer membrane) Reaction Time (min) Setting Time (hrs) Force to Burst (Newtons)b... 

MANGANESE CARBONATE PARTICLES PREPARATION BY COLLOIDAL AGGREGATION FOR HOLLOW POLYELECTROLYTE CAPSULES FABRICATION... 

Method for synthesis of monodisperse spherical-like manganese carbonate (MnCOs) particles by colloidal aggregation process is developed. Hollow polyelectrolyte capsules have been prepared by means of layer-by-layer absorption of charged polyelectrolytes on microsized MnCOs particles with the subsequent decomposition of a micrometer nucleus. The use of inorganic templates is a way for clean capsules fabrication. The manganese carbonate particles and capsules obtained were investigated by SEM, SFM, XRD, and confocal fluorescent microscopy. 

Hollow polyelectrolyte capsules were prepared as described earlier [8]. 

Figure 2. Confocal microscopy and SEM images of hollow polyelectrolyte capsules prepared by layer-by-layer on manganese carbonate particles. Scalebar is 5 pm. 

Initial poly(styrene sulfonate) (PSS, MW 70000) / poly(allylamine hydrochloride) (PAH, MW 50000) polyelectrolyte capsules containing 0.1 M of PAH monomers... 

Figure 1. Schematic illustration of hollow polyelectrolyte capsule formation (a-c) followed by the selective inorganic synthesis inside (d-e). a-b layer-by-layer precipitation of poly(styrene sulfonate), poly(allylamine hydrochloride) monolayers b-c dissolution of template core c-d loading of polyelectrolyte capsules with corresponding anions d-e precipitation of inorganic material from... 

Figure 2. SEM images of polyelectrolyte capsules filled hydroxiapatite (a), Fe304 (b) and YF3 (c). (d) -TEM image of ultramicrotomed polyelectrolyte capsule filled with Fe304.

In conclusion, controllable inorganic precipitation can be performed exclusively inside polyelectrolyte capsules forming the hollow composite structure. Capsules bearing material with certain properties (conductivity, magnetic susceptibility, etc.) can find practical applications in novel micron-scale electronic and optoelectronic devices, drug delivery, microreactors for spatially restricted catalytic chemical and biochemical synthesis. The influence of micron-scale volume and capsule composition on chemical reactions in capsule interior is a subject for further investigations. 

Another type of functional nanocontainers can be fabricated by Layer-by-Layer assembly of oppositely charged species. Layer-by-Layer assembly of oppositely charged species was first proposed by Iler in 1966 [1] and later developed by Decher et al. [2]. The universal character of the method does not have any restriction on the type of the charged species employed for a shell construction. The precision of one adsorbed layer thickness is about 1 nm. The shell of the polyelectrolyte capsules is semipermeable and sensitive to a variety of physical and chemical conditions of the surrounding media, which might dramatically influence the structure of polyelectrolyte complexes and the permeability of the capsules. Introduction of nanosized metals (Ag, Au) or magnetic nanomaterials (Fe3O4) into the shell of polyelectrolyte capsules attains... 

De Geest BG, Skirtach AG, De Beer TRM et al (2007) Stimuli-responsive multilayered hybrid nanoparticle/polyelectrolyte capsules. Macromol Rapid Commun 28(l) 88-95... 

Choi WS, Koo HY, Park JH et al (2005) Synthesis of two types of nanoparticles in polyelectrolyte capsule nanoreactors and their dual functionality. J Am Chem Soc 127(46) 16136-16142... 

Tong W, Gao C, Mohwald H (2005) Manipulating the properties of polyelectrolyte capsules by glutaraldehyde cross-linking. Chem Mater 4610-4616... 

Pastoriza-Santos I, Scholer B, Catuso F (2001) Core-shell colloids and hollow polyelectrolyte capsules based on diazoresins. Adv Funct Mater 11 122-128... 

Zelikin AN, Li Q, Caruso F (2006) Degradable polyelectrolyte capsules filled with oligonucleotide sequences. Angew Chem Int Ed 45 7743-7745... 

Ibarz G, Dahne L, Donath E, et al. (2002) Reseating of polyelectrolyte capsules after core removal. Macromol Rapid Commtm 23 474- 78... 

Stadler B, Chandrawati R, Goldie K, et al. (2009) Capsosomes subcompartmentalizing polyelectrolyte capsules using liposomes. Langmuir 25 6725-6732... 

Vasiliu, S., Popa, M., Rinaudo, M., 2005. Polyelectrolyte capsules made of two biocompatible natural polymers. European Polymer Journal 41 (5), 923—932. 

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