Nucleobases thin films deposited on nanostructured transparent conductive electrodes for optoelectronic applications.

Environmentally-friendly bio-organic materials have become the centre of recent developments in organic electronics, while a suitable interfacial modification is a prerequisite for future applications. In the context of researches on low cost and biodegradable resource for optoelectronics applications, the influence of a 2D nanostructured transparent conductive electrode on the morphological, structural, optical and electrical properties of nucleobases (adenine, guanine, cytosine, thymine and uracil) thin films obtained by thermal evaporation was analysed. The 2D array of nanostructures has been developed in a polymeric layer on glass substrate using a high throughput and low cost technique, UV-Nanoimprint Lithography. The indium tin oxide electrode was grown on both nanostructured and flat substrate and the properties of the heterostructures built on these two types of electrodes were analysed by comparison. We report that the organic-electrode interface modification by nano-patterning affects both the optical (transmission and emission) properties by multiple reflections on the walls of nanostructures and the electrical properties by the effect on the organic/electrode contact area and charge carrier pathway through electrodes. These results encourage the potential application of the nucleobases thin films deposited on nanostructured conductive electrode in green optoelectronic devices.

Optimized silicon reinforcement of carbon coatings by pulsed laser technique for superior functional biomedical surfaces fabrication.

We report on the fabrication of silicon-reinforced carbon (C:Si) structures by combinatorial pulsed laser deposition to search for the best design for a new generation of multi-functional coated implants. The synthesized films were characterized from the morphological, structural, compositional, mechanical and microbiological points of view. Scanning electron microscopy revealed the presence, on top of the deposited layers, of spheroid particulates with sizes in the micron range. No micro-cracks or delaminations were observed. Energy dispersive x-ray spectroscopy and grazing incidence x-ray diffraction pointed to the existence of a C to Si compositional gradient from one end of the film to the other. Raman investigation revealed a relatively high sp3 hybridization of up to 80% at 40-48 mm apart from the edge with higher C content. Si addition was demonstrated to significantly increase C:Si film bonding to the substrate, with values above the ISO threshold for coatings to be used in high-loading biomedical applications. Surface energy studies pointed to an increase in the hydrophilic character of the deposited structures along with Si content up to 52 mN m-1. In certain cases, the Si-reinforced C coatings elicited an antimicrobial biofilm action. The presence of Si was proven to be benign to HEp-2 cells of human origin, without interfering with their cellular cycle. On this basis, reliable C:Si structures with good adherence to the substrate and high efficiency against microbial biofilms can be developed for implant coatings and other advanced medical devices.

Laser deposition of poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) - lysozyme microspheres based coatings with anti-microbial properties.

The purpose of this study was to obtain, characterize and evaluate the cytotoxicity and antimicrobial activity of coatings based on poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) - Lysozyme (P(3HB-3HV)/Lys) and P(3HB-3HV) - Polyethylene glycol - Lysozyme (P(3HB-3HV)/PEG/Lys) spheres prepared by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique, in order to obtain functional and improved Ti-based implants. Morphological investigation of the coatings by Infrared Microscopy (IRM) and SEM revealed that the average diameter of P(3HB-3HV)/Lys spheres is around 2µm and unlike the drop cast samples, IRM recorded on MAPLE films revealed a good distribution of monitored functional groups on the entire scanned surface. The biological evaluation of MAPLE structured surfaces revealed an improved biocompatibility with respect to osteoblasts and endothelial cells as compared with Ti substrates and an enhanced anti-biofilm effect against Gram positive (Staphylococcus aureus) and Gram negative (Pseudomonas aeruginosa) tested strains. Thus, we propose that the fabricated P(3HB-3HV)/PEG/Lys and P(3HB-3HV)/Lys microspheres may be efficiently used as a matrix for controlled local drug delivery, with practical applications in developing improved medical surfaces for the reduction of implant-associated infections.

Fabrication of magnetite-based core-shell coated nanoparticles with antibacterial properties.

We report the fabrication of biofunctionalized magnetite core/sodium lauryl sulfate shell/antibiotic adsorption-shell nanoparticles assembled thin coatings by matrix assisted pulsed laser evaporation for antibacterial drug-targeted delivery. Magnetite nanoparticles have been synthesized and subsequently characterized by transmission electron microscopy and x-ray diffraction. The obtained thin coatings have been investigated by FTIR and scanning electron microscope, and tested by in vitro biological assays, for their influence on in vitro bacterial biofilm development and cytotoxicity on human epidermoid carcinoma (HEp2) cells.

Usnic acid-loaded biocompatible magnetic PLGA-PVA microsphere thin films fabricated by MAPLE with increased resistance to staphylococcal colonization.

Due to their persistence and resistance to the current therapeutic approaches, Staphylococcus aureus biofilm-associated infections represent a major cause of morbidity and mortality in the hospital environment. Since (+)-usnic acid (UA), a secondary lichen metabolite, possesses antimicrobial activity against Gram-positive cocci, including S. aureus, the aim of this study was to load magnetic polylactic-co-glycolic acid-polyvinyl alcohol (PLGA-PVA) microspheres with UA, then to obtain thin coatings using matrix-assisted pulsed laser evaporation and to quantitatively assess the capacity of the bio-nano-active modified surface to control biofilm formation by S. aureus, using a culture-based assay. The UA-loaded microspheres inhibited both the initial attachment of S. aureus to the coated surfaces, as well as the development of mature biofilms. In vitro bioevalution tests performed on the fabricated thin films revealed great biocompatibility, which may endorse them as competitive candidates for the development of improved non-toxic surfaces resistant to S. aureus colonization and as scaffolds for stem cell cultivation and tissue engineering.

Functionalized magnetite silica thin films fabricated by MAPLE with antibiofilm properties.

We report on the fabrication of magnetite/salicylic acid/silica shell/antibiotics (Fe(3)O(4)/SA/SiO(2)/ATB) thin films by matrix-assisted pulsed laser evaporation (MAPLE) to inert substrates. Fe(3)O(4)-based powder have been synthesized and investigated by XRD and TEM. All thin films were studied by FTIR, SEM and in vitro biological assays using Staphylococcus aureus and Pseudomonas aeruginosa reference strains, as well as eukaryotic HEp-2 cells. The influence of the obtained nanosystems on the microbial biofilm development as well as their biocompatibility has been assessed. For optimum deposition conditions, we obtained uniform adherent films with the composition identical with the raw materials. Fe(3)O(4)/SA/SiO(2)/ATB thin films had an inhibitory activity on the ability of microbial strains to initiate and develop mature biofilms, in a strain- and antibiotic-dependent manner. These magnetite silica thin films are promising candidates for the development of novel materials designed for the inhibition of medical biofilms formed by different pathogenic agents on common substrates, frequently implicated in the etiology of chronic and hard to treat infections.

Specific biofunctional performances of the hydroxyapatite-sodium maleate copolymer hybrid coating nanostructures evaluated by in vitro studies.

The nanohybrid structures consisting of hydroxyapatite (HA) and sodium maleate-vinyl acetate copolymer (MP) deposited by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique on Ti surfaces were investigated for specific biological qualities required in bone implantology. The data from in vitro studies demonstrated that human primary osteoblasts (OBs) firmly adhered to Ti coated with HA-MP as indicated by cytoskeleton and vinculin dynamics. OBs spread onto biomaterial surface and formed groups of cells which during their biosynthetic activity expressed OB phenotype specific markers (collagen and non-collagenous proteins) and underwent controlled proliferation.

Strontium-substituted hydroxyapatite coatings synthesized by pulsed-laser deposition: in vitro osteoblast and osteoclast response.

The increasing interest in strontium incorporation into biomaterials for hard tissue repair is justified by the growing evidence of its beneficial effect on bone. We successfully synthesized hydroxyapatite (HA) thin films with different extents of strontium substitution for calcium (0, 1, 3 or 7 at.%) by pulsed-laser deposition. The coatings displayed a granular surface and a good degree of crystallinity, which slightly diminished as strontium content increased. Osteoblast-like MG63 cells and human osteoclasts were cultured on the thin films up to 21 days. MG63 cells grown on the strontium-doped HA coatings displayed normal morphology, good proliferation and increased values of the differentiation parameters, whereas the number of osteoclasts was negatively influenced by the presence of strontium. The positive effect of the ion on bone cells was particularly evident in the case of coatings deposited from HA at relatively high strontium contents (3-7%), where significantly increased values of alkaline phosphatase activity, osteocalcin, type I collagen and osteoprotegerin/TNF-related activation-induced cytokine receptor ratio, and considerably reduced values of osteoclast proliferation, were observed.

Human osteoblast response to pulsed laser deposited calcium phosphate coatings.

Octacalcium phosphate (OCP) and Mn(2+)-doped carbonate hydroxyapatite (Mn-CHA) thin films were deposited on pure, highly polished and chemically etched Ti substrates with pulsed laser deposition. The coatings exhibit different composition, crystallinity and morphology that might affect their osteoconductivity. Human osteoblasts were cultured on the surfaces of OCP and Mn-CHA thin films, and the cell attachment, proliferation and differentiation were evaluated up to 21 days. The cells showed a normal morphology and a very good rate of proliferation and viability in every experimental time. Alkaline phosphatase activity was always higher than the control and Ti groups. From days 7 to 21 collagen type I production was higher in comparison with control and Ti groups. The level of transforming growth factor beta 1 (TGF-beta1) was lower at 3 and 7 days, but reached the highest values during following experimental times (14 and 21 days). Our data demonstrate that both calcium phosphate coatings favour osteoblasts proliferation, activation of their metabolism and differentiation.

Biocompatible Mn2+-doped carbonated hydroxyapatite thin films grown by pulsed laser deposition.

Mn(2+)-doped carbonated hydroxyapatite (Mn-CHA) thin films were obtained by pulsed laser deposition on Ti substrates. The results of the performed complementary diagnostic techniques, X-ray diffraction, infrared spectroscopy, X-ray photoelectron spectroscopy, and energy dispersive X-ray spectroscopy investigations indicate that the films are crystalline with a Ca/P ratio of about 1.64-1.66. The optimum conditions, when nearly stoichiometric crystalline thin films were deposited, were found to be 10 Pa oxygen pressure, 400 degrees C substrate temperature, and postdeposition heat treatment in water vapors at the same substrate temperature. The films were seeded with L929 fibroblast and hFOB1.19 osteoblast cells and subjected to in vitro tests. Both fibroblast and osteoblast cells have a good adherence on the Mn-CHA film and on the Ti or polystyrene references. Proliferation and viability tests showed that osteoblast cells growth on Mn-CHA-coated Ti was enhanced as compared to uncoated pure Ti surfaces. Caspase-1 activity was not affected significantly by the material, showing that Mn-CHA does not induce apoptosis of cultured cells. These results demonstrate that Mn-CHA films on Ti should provoke a faster osteointegration of the coated implants as compared to pure Ti. (c) 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 353-358, 2004.

Biocompatible nanocrystalline octacalcium phosphate thin films obtained by pulsed laser deposition.

We extended for the first time pulsed laser ablation to the deposition of octacalcium phosphate Ca8H2(PO4)6.5H2O (OCP) thin films. The depositions were performed with a pulsed UV laser source (lambda=248 nm, tau> or =20 ns) in a flux of hot water vapors. The targets were sintered from crystalline OCP powder and the laser ablation fluence was set at values of 1.5-2 J/cm2. During depositions the collectors, Si or Ti substrates, were maintained at a constant temperature within the range 20-200 degrees C. The resulting structures were submitted to heat treatment in hot water vapors for up to 6 h. The best results were obtained at a substrate temperature of 150 degrees C during both deposition and post-deposition treatment. High-resolution electron microscopy and XRD at grazing incidence indicated that the coatings obtained were made of nanocrystalline OCP. Cross-section TEM investigations showed that the coatings contained droplets stacked on Ti substrates as well as distributed across the entire thickness of the arborescence-like structure layers. The results of WST-1 assay, cell adherence, DNA replication, and caspase-1 activity confirmed the good biocompatibility of the coatings.