Polyelectrolyte nanocontainers

By contrast, opening of polyelectrolyte nanocontainers with silver-modified TiOz cores results from the photothermal transitions in the polyelectrolyte shell. Similar mechanism is responsible for the opening of SiOz-based containers with silver nanoparticles incorporated directly into the polyelectrolyte shell. The possibility of selective light-addressable opening of containers embedded into the SiOxiZrOx matrix was confirmed with the use of... 

X.R. Teng, D.G. Shchukin, and H. Mohwald, A novel drug carrier Lipophilic drug-loaded polyglutamate/polyelectrolyte nanocontainers, Langmuir, 24(2), 383-389 (2008). 

Schematic illustration of the fabrication of 2-mercaptobenzothiazole-loaded halloysite/polyelectrolyte nanocontainers. Right zeta potential data for sequential deposition of PAH and PSS polyelectrolytes on halloysite nanotubes, pH 7.5 (Shchukin et al., 2008). 

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. 

Mesoporous Particles with Polyelectrolyte Shell as Nanocontainers for Inhibitors... 

To make the containers sensitive to IR laser light, preformed silver nanoparticles were directly incorporated into the polyelectrolyte shell. For this purpose, AgNPs were added into solutions of polyelectrolytes for LbL deposition and hence fixed between the polyelectrolyte layers. The AFM images of the resultant nanocontainer-impregnated him showed a uniform distribution of the containers over the coating, with the concentration of the silica containers equalling 107 containers per meter squared. 

The release characteristics of nanocontainers with the polyelectrolyte shell (Fig. Ic) were studied in aqueous neutral solutions under laser irradiation. It is seen from Fig. Id that under the dark conditions the release of eneapsulated BSA is almost completely suppressed. The release of BSA under IR laser irradiation was observed for Si02- and Ti02-based containers modified with Ag nanoparticles, while only Ti02-based containers (both bare and silver-modified ones) exhibit switching into the open state under UV irradiation. It is seen from Fig. Id that the UV-induced release appears to be especially effective in the case... 

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... 

Furthermore, porous CPs (e.g., polypyrrole, polyanUine) films have been used as host matrices for polyelectrolyte capsules developed from composite material, which can combine electric conductivity of the polymer with controlled permeability of polyelectrolyte shell to form controllable micro- and nanocontainers. A recent example was reported by D.G. Schchukin and his co-workers [21]. They introduced a novel application of polyelectrolyte microcapsules as microcontainers with a electrochemically reversible flux of redox-active materials into and out of the capsule volume. Incorporation of the capsules inside a polypyrrole (PPy) film resulted in a new composite electrode. This electrode combined the electrocatalytic and conducting properties of the PPy with the storage and release properties of the capsules, and if loaded with electrochemical fuels, this film possessed electrochemically controlled switching between open and closed states of the capsule shell. This approach could also be of practical interest for chemically rechargeable batteries or fuel cells operating on an absolutely new concept. However, in this case, PPy was just utilized as support for the polyelectrolyte microcapsules. 

Grigoriev DO, Bukreeva T, Mohwald H, Shchukin DG. New method for fabrication of loaded micro- and nanocontainers emulsion encapsulation by polyelectrolyte layer-by-layer deposition on the liquid core. Langmuir 2008 24(3) 999—1004. 

The most probable mechanism is based on the local change of pH in the damaged area due to the corrosion processes. When the corrosion processes start, the pH value is changed in the neighbouring area, which opens the poly electrolyte shells of the nanocontainers in a local area with the following release of BTA. Then, the released inhibitor suppresses the corrosiou activity and the pH value recovers, closing the polyelectrolyte shell of nanocontainers and terminating further release of the inhibitor, as schematically shown in Fig. 9.9 (Zheludkevich et ai, 2007). 

Key words nanocontainer(s), self-heahng, controlled release, LbL assembly, polyelectrolyte. 

Grigoriev D. O., Bukreeva T, Mohwald H. and Shchukin D. G. (2008), New Method for Fabrication of Loaded Micro- and Nanocontainers Emulsion Encapsulation by Polyelectrolyte Layer-by-Layer Deposition on the Liquid Core , Langmuir, 24,999-1004. 

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