Tannic acid (TA) was assembled in alternation with two different polycations, strong poly(dimethyldiallylamide) (PDDA) and weak poly(allylamine) (PAH), using a layer-by-layer technique. Their deposition at different pH was confirmed by QCM, UV−vis spectroscopy, and surface charge measurements. TA/polyelectrolyte multilayer films and capsules have pH-dependent structural properties different from those of commonly used poly(styrenesulfonate)/poly(allylamine) (PSS/PAH) compositions. The lowest speed of TA/polycation multilayer dissolution was found at the conditions close to those used for film preparation. Permeability for fluorescein-labeled dextrans into tannic acid/polycation capsules with a five bilayer wall composition was investigated as a function of pH using confocal microscopy. It was found that minimal permeability occurs at pH 5−7 and maximal permeability at very high and very low pH, providing new opportunities for capsule loading as compared with an established procedure for PSS/PAH microcapsules. For TA/PDDA layers, less soluble films and less permeable capsules were obtained as compared with TA/PAH layers.

Natural polyphenols with previously demonstrated anticancer potential, epigallocatechin gallate (EGCG), tannic acid, curcumin, and theaflavin, were encased into gelatin-based 200 nm nanoparticles consisting of a soft gel-like interior with or without a surrounding LbL shell of polyelectrolytes (polystyrene sulfonate/polyallylamine hydrochloride, polyglutamic acid/poly-l-lysine, dextran sulfate/protamine sulfate, carboxymethyl cellulose/gelatin, type A) assembled using the layer-by-layer technique. The characteristics of polyphenol loading and factors affecting their release from the nanocapsules were investigated. Nanoparticle-encapsulated EGCG retained its biological activity and blocked hepatocyte growth factor (HGF)-induced intracellular signaling in the breast cancer cell line MBA-MD-231 as potently as free EGCG.

150–200 nm diameter capsules containing 60–70 wt % of poorly soluble drugs, paclitaxel and camptothecin, were produced by layer-by-layer (LbL) assembly on drug nanocores in a solution containing uncharged stabilizers. Optimization of capsule shell architecture and thickness allowed for concentrated (3–5 mg/mL) colloids that are stable in isotonic salt buffers. Nanoparticle aggregation during the washless LbL-assembly was prevented by using low molecular weight block-copolymers of poly(amino acids) (poly-L-lysine and poly-L-glutamic acid) with polyethylene glycol (PEG) in combination with heparin and bovine serum albumin at every bilayer building step. Minimal amounts of the polyelectrolytes were used to recharge the surface of nanoparticles in this non-washing LbL process. Such PEGylated shells resulted in drug nanocapsules with high colloidal stability in PBS buffer and increased protein adhesion resistance. The washless LbL polyelectrolyte nanocapsule assembly process, colloidal stability and nanoparticle morphology were monitored by dynamic light scattering and electrophoretic mobility measurements, UV-vis spectroscopy, TEM, SEM and laser confocal microscopy imaging.

A new type of protective microcontainer, capable of preventing oxidation of encapsulated compounds by low molecular weight oxidizing agents, was demonstrated. These microcontainers (microcapsules) are hollow spheres with the shell made of layer-by-layer assembled polyelectrolytes with an engineered outermost layer. The protecting ability of the developed polyelectrolyte capsules was monitored by oxidation of encapsulated bovine serum albumin by H2O2 dissolved in aqueous solution. Different catalysts for H2O2 decomposition (catalase, Fe3O4 nanoparticles) were deposited onto the polyelectrolyte shell to increase the protection efficiency. The highest protection activity was observed for poly(allylamine)/poly(styrene sulfonate) capsules containing nano-Fe3O4 in the polyelectrolyte shell.