Nanocomposite multifunctional polyelectrolyte thin films with copper nanoparticles as the antimicrobial coatings.

The work presents the formation and physicochemical characterization of polyelectrolyte-copper nanocomposite coatings using: poly(diallyldimethylammonium chloride) (PDADMAC) as a polycation, poly(sodium 4-styrenesulfonate)(PSS) as a polyanion and negatively charged copper nanoparticles (CuNPs) to obtain biocompatible surfaces with an antibacterial functionality. The mass and thickness of composite films were investigated by the quartz crystal microbalance with dissipation monitoring (QCM-D) and the ellipsometry whereas, the structure and morphology of coatings were examined using scanning electron microscopy (SEM). The increase of the UV-Vis absorption confirmed the formation of the consecutive layers of the film. Antibacterial activity of the coatings was tested on a representative Gram-positive bacteria strain, Staphylococcus aureus. The microbiological tests were performed and bacteria visualized using fluorescent staining and microscopic technique. It was demonstrated that nanostructured films had antibacterial properties, which makes polyelectrolyte multilayer films containing copper an interesting material in biomedical applications area, e.g., for the prevention of microbial deposition on surfaces.

Gadolinium alginate nanogels for theranostic applications.

Synthesis of theranostic nanoparticles, which combine both therapeutic and diagnostic capabilities in one platform can be considered as a step forward personalized medicine, since it allows tracing the delivery of the drug to targeted organ. Thus, the aim of this work was to prepare gadolinium alginate gel nanoparticles (gadolinum nanogels - GdNG) by the reverse microemulsions and physical crosslinking method as the vehicles able to carry hydrophilic drugs and to be traced by the Magnetic Resonance Imaging (MRI). The average size of synthesized nanoparticles was about 110nm and the batch concentration was 1010 particles/ml. The morphology of nanogeles was visualized by Cryo-Scanning Electron Microscopy. Surface of nanogels particles was modified by the Layer-by-Layer (LbL) technique using natural polyelectrolytes. The cytotoxicity of non-modified and LbL modified nanogels was evaluated by the cellular viability quantification and cell death assessments using MTT and LDH biochemical tests, respectively. We encapsulated the model compound - fluorescent dye (Rhodamine b) in nanogels networks and proved the possibility of GdNG visualization by MRI.

Linseed oil based nanocapsules as delivery system for hydrophobic quantum dots.

In the present work, the CdSe/ZnS hydrophobic quantum dots were embedded within the polyelectrolyte nanocapsules. The core of the capsules, which consists of a mixture of the linseed oil with chloroform, was prepared using the spontaneous emulsification technique. The obtained emulsions were stabilized with lecithin and encapsulated using the layer-by-layer (LbL) adsorption of polyelectrolytes. The pair of biocompatible polyelectrolytes was used: the cationic poly-l-lysine hydrobromide (PLL) together with the anionic poly-d-glutamic acid sodium salt. The saturation LbL method, which is based on the stepwise formation of consecutive layers on the initial emulsion without the intermediate rinsing step, was applied to form the capsule shells. Their growth was evidenced by the capsule size and electrophoretic mobility measurements. The emulsion and the capsules were deposited on a mica surface and the deposit topology was examined by the means of atomic force microscopy (AFM). The presence of quantum dots within the oil cores was confirmed by recording the fluorescent spectra of the samples containing CdSe/ZnS. In order to evaluate cytotoxicity of the capsules, their influence on the viability of mouse embryonic fibroblasts was examined using the MTT test, followed by optical-microscope observation of morphology of the cells after hematoxylin-eosin staining.

Antireflection TiO x Coating with Plasmonic Metal Nanoparticles for Silicon Solar Cells.

It is known that the light scattering from the metal particles deposited on the surfaces of cells can be used for increasing light trapping in the solar cells. In this work, plasmonic structures are composite materials that consisted of silver nanoparticles embedded in dielectric films of TiO x -used as cell antireflection coating. The films are deposited by sol-gel method using spin-on technique. Microstructure of prepared samples is analyzed by SEM observation. Good homogenity and particles density was obtained by this simple, cheap, and short time-demanding method. We demonstrate that due to light scattering by metal particles, the plasmonic-ARC layer is more effective than TiO x layer without Ag nanoparticles. Implementation of nanoparticles on bare cell surface was carried out too. The influence of the plasmonic structures on the silicon solar cells parameters is presented as well. We announce about 5 % additional growth in short circuit current for cells with nanoparticles.

Polyelectrolyte multilayer capsules with quantum dots for biomedical applications.

The aim of this work was to encapsulate the CdTe quantum dots within the nanocapsules that were prepared by the layer-by-layer adsorption of polyelectrolytes. Two different polyelectrolyte pairs were used as components of the shell: synthetic polycation poly(allyamine hydrochloride) (PAH), together with anionic poly(sodium styrene sulfonate) (PSS), and biocompatible cationic poly-L-lysine hydrobromide in a pair with biocompatible anionic poly-D-glutamic acid sodium salt (PGA). The saturation method was used for formation of consecutive layers on the initial CdTe-polyelectrolyte complex. A growth of the polyelectrolyte shell was followed with the electrophoretic mobility and light scattering measurements, in order to determine the zeta potential and the size of capsules, respectively. The fluorescent spectra of the quantum dots, which are embedded within the capsules, were characterized with spectrofluorimeter. Later on, they were deposited on a negatively charged mica surface and studied by the means of atomic force microscopy (AFM). In order to estimate the cytotoxicity of capsules, their influence on the B-lymphoblastoid cell line proliferation and on unspecific binding to the P-blood mononuclear cells was examined using the flow cytometry.

Formation of biocompatible nanocapsules with emulsion core and pegylated shell by polyelectrolyte multilayer adsorption.

The aim of this work was to develop a novel method of preparation of loaded nanosize capsules based on liquid core encapsulation by biocompatible polyelectrolyte (PE) multilayer adsorption, with or without pegylated outermost layer. Using AOT (docusate sodium salt) as emulsifier, we obtained cores, stabilized by an AOT/PLL (poly-L-lysine hydrobromide) surface complex. These positively charged cores were encapsulated by layer-by-layer adsorption of polyelectrolytes, biocompatible polyanion PGA (poly-L-glutamic acid sodium salt), and biocompatible polycation PLL. We used the saturation method for formation of consecutive layers, and we determined the optimal conditions concerning concentration of surfactant and polyelectrolytes to form stable shells. The average size of the obtained capsules was 60 nm. Pegylated external layer were prepared using PGA-g-PEG (PGA grafted by PEG poly(ethylene glycol)). The capsules were stable for at least a period of 3 months. These nanocapsules were biocompatible when tested for cytotoxicity in a cellular coculture assay and demonstrated no or very low nonspecific binding to peripheral blood mononuclear cells when tested by flow cytometry. In order to study drug effects on leukemia cells, beta-carotene and vitamin A have been encapsulated as model drugs.