Biofunctional composite coating architectures based on polycaprolactone and nanohydroxyapatite for controlled corrosion activity and enhanced biocompatibility of magnesium AZ31 alloy

In this work a biofunctional composite coating architecture for controlled corrosion activity and enhanced cellular adhesion of AZ31 Mg alloys is proposed. The composite coating consists of a polycaprolactone (PCL) matrix modified with nanohydroxyapatite (HA) applied over a nanometric layer of polyetherimide (PEI). The protective properties of the coating were studied by electrochemical impedance spectroscopy (EIS), a non-disturbing technique, and the coating morphology was investigated by field emission scanning electron microscopy (FE-SEM). The results show that the composite coating protects the AZ31 substrate. The barrier properties of the coating can be optimized by changing the PCL concentration. The presence of nanohydroxyapatite particles influences the coating morphology and decreases the corrosion resistance. The biocompatibility was assessed by studying the response of osteoblastic cells on coated samples through resazurin assay, confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). The results show that the polycaprolactone to hydroxyapatite ratio affects the cell behavior and that the presence of hydroxyapatite induces high osteoblastic differentiation. (C) 2014 Elsevier B.V. All rights reserved.

Self-assembly of a dual functional bioactive peptide amphiphile incorporating both matrix metalloprotease substrate and cell adhesion motifs

We describe a bioactive lipopeptide that combines the capacity to promote the adhesion and subsequent self-detachment of live cells, using template-cell-environment feedback interactions. This self-assembling peptide amphiphile comprises a diene-containing hexadecyl lipid chain (C16e) linked to a matrix metalloprotease-cleavable sequence, Thr-Pro-Gly-Pro-Gln-Gly-Ile-Ala-Gly-Gln, and contiguous with a cell-attachment and signalling motif, Arg-Gly-Asp-Ser. Biophysical characterisation revealed that the PA self-assembles into 3 nm diameter spherical micelles above a critical aggregation concentration (cac). In addition, when used in solution at 5–150 nM (well below the cac), the PA is capable of forming film coatings that provide a stable surface for human corneal fibroblasts to attach and grow. Furthermore, these coatings were demonstrated to be sensitive to metalloproteases expressed endogenously by the attached cells, and consequently to elicit the controlled detachment of cells without compromising their viability. As such, this material constitutes a novel class of multi-functional coating for both fundamental and clinical applications in tissue engineering.

Characterisation and electrochemical behaviour of electrodeposited Cu-Fe foams applied as pseudocapacitor electrodes

Copper iron (Cu-Fe) 3D porous foams for supercapacitor electrodes were electrodeposited in the cathodic regime, on stainless steel current collectors, using hydrogen bubbling dynamic template. The foams were prepared at different current densities and deposition times. The foams were submitted to thermal conditioning at temperatures of 150 and 250 degrees C. The morphology, composition and structure of the formed films were studied by SEM, EDS and XRD, respectively. The electrochemical behaviour was studied by cyclic voltammetry, electrochemical impedance spectroscopy and chronopotentiometry. The morphology of the 3D Cu-Fe foams is sensitive to the electrodeposition current and time. The increase of the current density produces a denser, larger and more ramified dendritic structure. Thermal conditioning at high temperature induces a coarser grain structure and the formation of copper oxides, which affect the electrochemical behaviour. The electrochemical response reveals the presence of various redox peaks assigned to the oxidation and reduction of Cu and Fe oxides and hydroxides in the foams. The specific capacitance of the 3D Cu Fe foams was significantly enhanced by thermal conditioning at 150 degrees C. The highest specific capacitance values attained 297 Fg(-1) which are much above the ones typically observed for single Cu or Fe Oxides and hydroxides. These values highlight a synergistic behaviour resulting from the combination of Cu and Fe in the form of nanostructured metallic foams. Moreover, the capacitance retention observed in an 8000 charge/discharge cycling test was above 66%, stating the good performance of these materials and its enhanced electrochemical response as supercapacitor negative electrodes. (C) 2014 Elsevier B.V. All rights reserved.

SOL-GEL Lanthanum Phosphate, Composite and coating for functional Applications.

Lanthanum phosphate is one among the lanthanide family of “Rare Earths” following the periodic table of elements. Known under the generic name, Monazite, the rare earth phosphates have melting points above 1900 °C, high thermal phase stability, low thermal conductivity and thermal expansion coefficient similar to some of the high temperature oxides like alumina and zirconia.

"In-vitro" corrosion behaviour of the magnesium alloy with Al and Zn (AZ31) protected with a biodegradable polycaprolactone coating loaded with hydroxyapatite and cephalexin

Mg alloys are very susceptible to corrosion in physiological media. This behaviour limits its widespread use in biomedical applications as bioresorbable implants, but it can be controlled by applying protective coatings. On one hand, coatings must delay and control the degradation process of the bare alloy and, on the other hand, they must be functional and biocompatible. In this study a biocompatible polycaprolactone (PCL) coating was functionalised with nano hydroxyapatite (HA) particles for enhanced biocompatibility and with an antibiotic, cephalexin, for anti-bacterial purposes and applied on the AZ31 alloy. The chemical composition and the surface morphology of the coated samples, before and after the corrosion tests, were studied by scanning electron microscopy (SEM) coupled with energy dispersive x-ray analysis (EDX) and Raman. The results showed that the presence of additives induced the formation of agglomerates and defects in the coating that resulted in the formation of pores during immersion in Hanks' solution. The corrosion resistance of the coated samples was studied in Hank's solution by electrochemical impedance spectroscopy (EIS). The results evidenced that all the coatings can provide corrosion protection of the bare alloy. However, in the presence of the additives, corrosion protection decreased. The wetting behaviour of the coating was evaluated by the static contact angle method and it was found that the presence of both hydroxyapatite and cephalexin increased the hydrophilic behaviour of the surface. The results showed that it is possible to tailor a composite coating that can store an antibiotic and nano hydroxyapatite particles, while allowing to control the in-vitro corrosion degradation of the bioresorbable Mg alloy AZ31. (C) 2015 Elsevier Ltd. All rights reserved.

Spray coating of oxide and chalcogenide semiconductor layers for TFT application

This work documents the deposition and optimization of semiconductor thin films using chemical spray coating technique (CSC) for application on thin-film transistors (TFTs), with a low-cost, simple method. CSC setup was implemented and explored for industrial application, within Holst Centre, an R&D center in the Netherlands. As zinc oxide had already been studied within the organization, it was used as a standard material in the initial experiments, obtaining typical mobility values of 0.14 cm2/(V.s) for unpatterned TFTs. Then, oxide X layer characteristics were compared for films deposited with CSC at 40°C and spin-coating. The mobility of the spin-coated TFTs was 103 cm2/(V.s) higher, presumably due to the lack of uniformity of spray-coated film at such low temperatures. Lastly, tin sulfide, a relatively unexplored material, was deposited by CSC in order to obtain functional TFTs and explore the device’s potential for working as a phototransistor. Despite the low mobilities of the devices, a sensitive photodetector was made, showing drain current variation of nearly one order of magnitude under yellow light. CSC technique’s simplicity and versatility was confirmed, as three different semiconductors were successfully implemented into functional devices.

Hot-dip galvanized steel dip-coatedwith ureasilicate hybrid in simulated concrete pore solution: Assessment of coating morphology and corrosion protection efficiency

The barrier effect and the performance of an organic–inorganic hybrid (OIH) sol–gel coating are highlydependent on the coating deposition method as well as processing conditions. In this work, studies onthe influence of experimental parameters using the dip coating method were performed. Factors suchas residence time (Rt), a curing step between each dip step and the number of layers of sol–gel OIHfilms deposited on HDGS to prevent corrosion in highly alkaline environments were studied. These OIHcoatings were obtained using a functionalized siloxane, 3-isociantepropyltriethoxysilane that reactedwith a diamino-functionalized oligopolymer (Jeffamine®D-230). The barrier efficiency of OIH coatings insimulated concrete pore solutions (SCPS) was assessed in the first moments of contact, by electrochemicalimpedance spectroscopy and potentiodynamic methods. The durability and stability of the OIH coatings inSCPS was monitored during eight days by macrocell current density. The morphological characterizationof the surface was performed by scanning electronic microscopy before and after exposure to SCPS.Glow discharge optical emission spectroscopy was used to obtain quantitative composition profiles toinvestigate the thickness of the OIH coatings as a function of the number of layers deposited and theinfluence of the Rt in the coating thickness.

Influence of chitosan coating on protein-based nanohydrogels properties and in vitro gastric digestibility

Chitosan coating was applied in Lactoferrin (Lf)-Glycomacropeptide (GMP) nanohydrogels by layer-by-layer coating process. A volume ratio of 0.1 of Lf-GMP nanohydrogels (0.2 mg.mL-1, at pH 5.0) to chitosan (1 mg.mL-1, at pH 3) demonstrated to be the optimal condition to obtain stable nanohydrogels with size of 230 ± 12 nm, a PdI of 0.22 ± 0.02 and a -potential of 30.0 ± 0.15 mV. Transmission electron microscopy (TEM) images showed that the application of chitosan coating in Lf-GMP did not affect the spherical shape of nanohydrogels and confirmed the low aggregation of nanohydrogels in solution. The analysis of chemical interactions between chitosan and Lf-GMP nanohydrogels were performed by Fourier transform infrared spectroscopy (FTIR) and by circular dichroism (CD) that revealed that a specific chemical interaction occurring between functional groups of protein-based nanohydrogels and active groups of the chitosan was established. The effect of chitosan coating on release mechanisms of Lf-GMP nanohydrogels at acid conditions (pH 2, 37 ºC) was evaluated by the encapsulation of a model compound (caffeine) in these systems. Linear Superposition Model was used to fit the experimental data and revealed that Fick and relaxation mechanisms are involved in caffeine release. It was also observed that the Fick contribution increase with the application of chitosan coating. In vitro gastric digestion was performed with Lf-GMP nanohydrogels and Lf-GMP nanohydrogels with chitosan coating and it was observed that the presence of chitosan improve the stability of Lf and GMP (proteins were hydrolysed at a slower rate and were present in solution by longer time). Native electrophoreses revealed that the nanohydrogels without coating remained intact in solution until 15 min and with chitosan coating remained intact until 60 min, during gastric digestion.

Enzyme convertedstarch in pigment coating

Tämän diplomityön tavoitteena oli selvittää entsyymikonvertoinnin mahdollisuudet vaikuttaa sideainetärkkelyksen toiminnallisiin ominaisuuksiin. Tärkein tehtävä oli etsiä vastaukset kysymykseen, kuinka paljon entsyymikonvertointia optimoimalla voidaan maksimoida tärkkelyksen positiivisia vaikutuksia. Tavoitteena oli myös tutkia, voiko lisäaineita käyttämällä ja tärkkelystä plastisoimalla säilyttää tärkkelyksen vaikutus paperin jäykkyyteen ja saada tärkkelysfilmille joustavuutta. Kirjallisuusosassa tarkasteltiin tärkkelyksen entsyymikonvertointiin vaikuttavia tekijöitä, eri tärkkelysraaka-aineiden eroja, sekä konvertoinnissa käytettävien entsyymien ominaisuuksia. Kirjallisuusosassa tarkasteltiin myöstärkkelyksen käyttöä sideaineena pigmenttipäällystyksessä. Kokeellisessa osassakeskityttiin selvittämään entsyymikonvertoinnin olosuhteiden, käytettävän raakatärkkelyksen ja entsyymin vaikutusta konvertoidun tärkkelyksen ominaisuuksiin. Konvertoiduista tärkkelyksistä valmistettiin päällystyspastat, ja tutkittiin niinpastan kuin päällystetyn paperin ominaisuuksia. Myös erilaisten pehmentimien vaikutusta niin päällystyspastaan, kuin paperin pinnalle tutkittiin. Havaittiin, että konvertoimalla tärkkelysketjua entsymaattisesti, voidaan tärkkelysketjun pituutta säädellä. Tarkoituksena oli konvertoida tärkkelystä niin, että tärkkelyksen molekyyliketjujakaumat sisältävät lyhyitä, keskipitkiä sekäpitkiä molekyylejä. Päällystämisen havaittiin olevan vaikeaa Helicoaterilla varsinkin pitkäketjuista tärkkelystä suuren määrän sisältävillä pastoilla. Myös tärkkelys/lateksi-suhde vaihteli eri pastoilla. Päällystyspastojen reologisia ominaisuuksia testattaessa huomattiin, että tärkkelysketjun pituuden kasvaessa pastanviskositeetti lisääntyy ja vesiretentio vähenee. Havaittiin vain muutamia teknisiä paperiominaisuuksia, jotka korreloivat hyvin tärkkelysketjun pituuden kanssa. Näitä olivat kiilto, Gurley-Hill huokoisuus, taivutusvastus, taivutuspituus sekä IGT pintalujuus. Pehmentimien ei havaittu vaikuttavan moneenkaan paperin eri tekniseen ominaisuuteen. Suurimmat erot huomattiin paperin taivutuspituudessa ja taivutusvastuksessa.

Highly functional binding surface for miniaturised solid-phase immunoassays. - A spot story -

Several bioaffinity assays are based on the detection of an analyte which is bound on a solid substrate via biochemical interaction. These so called solid phase assays are based on the adhesion of the primary binding partner on a solid surface, which then binds the analyte to be detected. In this thesis work a novel solid phase based assay technology, known as spot technology, was developed. The spot technology is based on combination of high-capacity solid phases, concentrated in a spot format, utilising modified streptavidin molecules and recombinant antibody fragments. The reduction of the solid phase binding surface to a size of a spot enabled denser binding of the target molecules, providing improved signal intensities and signal-to-background ratio when applied in different solid phase immunoassays. Streptavidin-biotin interactions are commonly utilised in numerous different bioaffinity assays and the ultimate nature of streptavidin to bind biotin is among the strongest non-covalent interaction reported between two biomolecules. In this study native core streptavidin was chemically modified to provide polymerised streptavidin molecules with altered adsorption properties. These streptavidin conjugates, when coated onto polystyrene surface, provided enhanced biotin binding capacity and surface stability when compared to a reference coating constructed with native streptavidin. Furthermore, the combination of chemically modified streptavidin, sitespecifically biotinylated antibody fragments and the spot coating technology provided highly dense solid phase coating with improved binding properties. The performance of the spot assay technology was further demonstrated in different immunoassay configurations. Human thyroid stimulating hormone (TSH) and human cardiac troponin I (cTnI) were used as model analytes to show the applicability of the highly sensitive spot-based solid-phase immunoassay for detection of very low levels of analytes. It was demonstrated that the spot technology provided an assay concept with enhanced sensitivity and short turn-around times, characteristics that are highly suitable for point-of-care applications.

DPS-Like Peroxide Resistance Protein: Structural and Functional Studies on a Versatile Nanocontainer

Oxidative stress is a constant threat to almost all organisms. It damages a number of biomolecules and leads to the disruption of many crucial cellular functions. It is caused by reactive oxygen species (ROS), such as hydrogen peroxide (H2O₂), superoxide (•O₂ -), and hydroxyl radical (•OH). The most harmful of these compounds is •OH, which is only formed in cells in the presence of redox-cycling transition metals, such as iron and copper. Bacteria have developed a number of mechanisms to cope with ROS. One of the most widespread means employed by bacteria is the DNA-binding proteins from starved cells (Dps). Dps proteins protect the cells by binding and oxidizing Fe2+, thus greatly reducing the production of •OH. The oxidized iron is stored inside the protein as an iron core. In addition, Dps proteins bind directly to DNA forming a protective coating that shields DNA from harmful agents. Moreover, Dps proteins have been found to elicit other protective functions in cells and to participate in bacterial virulence. Dps proteins are of special importance to Streptococci owing to the lack of catalase in this genus of bacteria.This study was focused on structural and functional characterization of streptococcal Dpslike peroxide resistance (Dpr) proteins. Initially, crystal structures of Streptococcus pyogenes Dpr were determined. The data confirmed the presence of a di-metal ferroxidase center (FOC) in Dpr proteins and revealed the presence of a novel N-terminal helix as well as a surface metal-binding site. The crystal structures of Streptococcus suis Dpr complexed with transition metals demonstrated the metal specificity of the FOC. Solution binding studies also indicated the presence of a di-metal FOC. These results suggested a possible role for Dpr in the detoxification of various metals. Iron was found to mineralize inside the protein as ferrihydrite based on X-ray absorption spectroscopy data. The iron core was found to exhibit clear superparamagnetic behaviour using magnetic and Mössbauer measurements. The results from this study are expected to further increase our understanding on the binding, oxidation, and mineralization of iron and other metals in Dpr proteins. In particular, the structural and magnetic properties of the iron core can form a basis for potential new applications in nanotechnology. From the streptococcal viewpoint, the results would help in understanding better the complicated picture of bacterial pathogenesis. Dpr proteins may also provide a novel target for drug design due to their tight involvement in bacterial virulence.

Effect of an edible crosslinked coating and two types of packaging on antioxidant capacity of castilla blackberries

In order to increase the shelf life and maintain the quality and stability of the biological compounds with antioxidant activity present in Castilla blackberry fruits, a sodium alginate-based edible crosslinked coating was applied, and the fruits were packed in two different plastic containers and stored under refrigeration (3 ± 1 °C). Total antioxidant capacity and its relationship to physicochemical variables such as pH, Brix, and acidity were evaluated in six treatments: uncoated blackberry stored in a macroperforated container (T1) and thermosealed container (T2), without crosslinked coating in a macroperforated container (T3) and thermosealed container (T4), with crosslinked coating (calcium ions) packed in macroperforated container (T5) and thermosealed container (T6). The results indicated that factors such as gas permeability in the coatings, the packaging used, and physicochemical parameters significantly affected the fruit total antioxidant capacity, with the highest level in T1 (0.22 µgEAA/ml) at the end of the essay, which is related to the lowest levels of pH and direct exposure to air. On the other hand, the lowest value was obtained in T6 (0.16 µgEAA/ml) due to the crosslinked coating, packaging in the thermosealed container, and higher pH value. Variations in acidity, Brix, and pH indicate the presence of degenerative processes in the crosslinked coating treatments, which limited the physicochemical changes.

Sol-Gel Alumina Nano Composites for Functional Applications

The thesis entitled "Sol-Gel Alumina Nano Composites for Functional Applications" investigate sol-gel methods of synthesis of alumina nanocomposites special reference to alumina-aluminium titanate and alumina-lanthanum phosphate composites. The functional properties such as thermal expansion coefficient and thermal shock resistance, machinability of composites as well as thermal protection are highlighted in addition to novel approach in synthesis of composites.A general introduction of alumina matrix composites materials, followed by brief coverage of alumina-aluminium titanate and alumina-lanthanum phosphate composites is highlight of the first chapter. The second chapter deals with the sol-gel synthesis of aluminium titanate and alumina-aluminium titanate composite. The synthesis of machinable substrate, based on alumina and lanthanum phosphate forms the basis of the third chapter. The fourth chapter describes the sol-gel coating of mullite on SiC substrate for the possible gas filtration application.

Lightly branched comb polyesters: application in fast drying solvent-borne coating formulations

Novel oxazoline-based comb-polymers possessing linoleyl or oleic side chains have been synthesized and used to produce low viscosity coatings. Inclusion of the polymers in model paint formulations results in coatings that exhibit faster drying times than commercially available alkyd resin formulations. The comb polymers were produced from diol substituted oxazoline monomers that were synthesized through a scalable, solvent free protocol and purified by simple recrystallisation. Co-polymerisation of the oxazolines with adipic acid at 160 °C in the bulk resulted in the targeted polyester comb type polymers. The polymers were soluble in a range of organic solvents and compatible with commercial alkyd resins. Model paint formulations containing up to 40 wt% of the linoleyl-based comb polymers exhibited a dramatic reduction in viscosity (from 35 to 13 Poise at 25 °C) with increasing quantities of polymer added. Dynamic mechanical analysis (DMA) studies revealed that the drying rate of the model paint formulations containing the comb polymers was enhanced when compared with that of commercial alkyd resins.

Evaluation of Bulk and Surfaces Absorption Edge Energy of Sol-Gel-Dip-Coating SnO2 Thin Films

The absorption edge and the bandgap transition of sol-gel-dip-coating SnO2 thin films, deposited on quartz substrates, are evaluated from optical absorption data and temperature dependent photoconductivity spectra. Structural properties of these films help the interpretation of bandgap transition nature, since the obtained nanosized dimensions of crystallites are determinant on dominant growth direction and, thus, absorption energy. Electronic properties of the bulk and (110) and (101) surfaces are also presented, calculated by means of density functional theory applied to periodic calculations at B3LYP hybrid functional level. Experimentally obtained absorption edge is compared to the calculated energy band diagrams of bulk and (110) and (101) surfaces. The overall calculated electronic properties in conjunction with structural and electro-optical experimental data suggest that the nature of the bandgap transition is related to a combined effect of bulk and (101) surface, which presents direct bandgap transition.