Alexei Antipov

pH‐Controlled Macromolecule Encapsulation in and Release from Polyelectrolyte Multilayer Nanocapsules

pH-Controlled encapsulation in and release of macromolecules from polyelectrolyte capsules of a few microns in diameter is demonstrated. Capsules were prepared via alternating adsorption of the oppositely charged polymers poly(allylamine hydrochloride) and poly(styrene sulfonate) onto decomposable melamin formaldehyde cores. The capsules were open for macromolecules at pH values below 6 and closed at pH > 8.

Polyelectrolyte multilayer capsule permeability control

Abstract The permeability properties of hollow polyelectrolyte multilayer capsules for different substances were investigated as a function of pH and salt concentration. Capsules were prepared by layer-by-layer (LBL) adsorption of oppositely charged polyelectrolytes onto the surface of melamine formaldehyde and CdCO3 particles followed by core removal. It was shown that the capsules are closed at a pH value of 8 and higher, but at a pH lower than 6 the macromolecules permeate into the capsule interior. For low molecular weight molecules capsules, templated on CdCO3 cores were found to be less permeable than MF-derived capsules. The open and closed states of the capsule wall are reversible. It provides thus an opportunity to encapsulate different materials into polyelectrolyte capsules.

Carbonate microparticles for hollow polyelectrolyte capsules fabrication

Calcium, cadmium and manganese carbonate crystals were used as core material for fabrication of hollow polyelectrolyte capsules by means of the Layer-by-Layer assembly. The use of inorganic templates is a way of fabrication of clean capsules, which is essential for basic research and is a significant step towards their biocompatibility. The ways of particle and capsule fabrication and characterization are described. Scanning electron microscopy (SEM)-Energy dispersive X-ray spectroscopy (EDX) measurements proved the purity of the hollow capsules from the core material. The capsules obtained were characterized by scanning force microscopy, and confocal fluorescence microscopy.

Entrapment of alpha-chymotrypsin into hollow polyelectrolyte microcapsules.

Stable hollow polyelectrolyte capsules were produced by the layer by layer assembling of non-biodegradable polyelectrolytes - poly(allylamine) and poly(styrenesulfonate) on melamine formaldehyde micro cores followed by the core decomposition at low pH. A proteolytic enzyme, a-chymotrypsin, was encapsulated into these microcapsules with high yields of up to 100%. The encapsulation procedure was based on the protein adsorption onto the capsule shells and on the pH-depend ent opening and closing of capsule wall pores. The protein in the capsules retained a high activity, and thermo- and storage stability. The nanostructured polyelectrolyte shell protected the proteinase from a high molecular weight inhibitor. Such enzyme-loaded capsules can be used as microreactors for biocatalysis.

Ultrasound stimulated release and catalysis using polyelectrolyte multilayer capsules

Ultrasound has been used to trigger release of encapsulated material from polyelectrolyte multilayer capsules. Sonication was found to destroy both plain and nanoparticle-modified capsules. Cavitation occurs through the collapse of generated microbubbles and the resulting shear forces should cause the destruction of the polyelectrolyte capsules. Application in catalysis is demonstrated in this paper, while further potential usage of ultrasound triggered release is anticipated in bio-medical applications.

Novel polyelectrolyte multilayer micro- and nanocapsules as magnetic carriers.

Polyelectrolyte multilayer (PEM) capsules are introduced as versatile magnetic carrier systems. Superparamagnetic magnetite is mounted to the multilayer shell itself or is a component of the capsule interior. The PEM is formed at different (decomposable) colloidal templates, e.g. melamine formaldehyde resin, glutaraldehyde fixed red blood cells, emulsion oil droplets. The results are illustrated by transmission electron microscopy and confocal laser scanning microscopy.

Palladium nanoclusters in microcapsule membranes: From synthetic shells to synthetic cells

We show that polyelectrolyte shells may be perfect hosts and microreactors for catalysis. Using a layer-by-layer self-assembly process to form hollow polyelectrolyte capsules, we show that individual layers can be replaced by palladium and gold nanoclusters forming robust cell-type microcapsules. Testing the catalytic activity of those embedded nanoclusters using the Sonogashira cross-coupling reaction, we show that simple self-assembled polyelectrolyte shells are ideal as carrier of at least one expensive catalyst, and possibly several, opening the road to new cascade reactions.

Cytotoxic and Proinflammatory Effects of Metal-Based Nanoparticles on THP-1 Monocytes Characterized by Combined Proteomics Approaches.

Thorough characterization of toxic effects of nanoparticles (NP) is desirable due to the increasing risk of potential environmental contamination by NP. In the current study, we combined three recently developed proteomics approaches to assess the effects of Au, CuO, and CdTe NP on the innate immune system. The human monocyte cell line THP-1 was employed as a model. The anticancer drugs camptothecin and doxorubicin were used as positive controls for cell death, and lipopolysaccharide was chosen as a positive control for proinflammatory activation. Despite equivalent overall toxicity effect (50 ± 10% dead cells), the three NP induced distinctly different proteomics signatures, with the strongest effect being induced by CdTe NP, followed by CuO and gold NP. The CdTe toxicity mechanism involves down-regulation of topoisomerases. The effect of CuO NP is most reminiscent of oxidative stress and involves up-regulation of proteins involved in heat response. The gold NP induced up-regulation of the inflammatory mediator, NF-κB, and its inhibitor TIPE2 was identified as a direct target of gold NP. Furthermore, gold NP triggered activation of NF-κB as evidenced by phosphorylation of the p65 subunit. Overall, the combined proteomics approach described here can be used to characterize the effects of NP on immune cells.