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  • Open access
  • 369 Reads
Functionalization of PU Foams via Inorganic and Organic Coatings to Improve Cell and Tissue Interactions
Published: 26 February 2019 by MDPI in 1st Coatings and Interfaces Web Conference session Biomaterial Surfaces & Interfaces

In this work an innovative method to obtain hybrid bio-functional scaffolds has been developed. Polyether urethane (PU) foam scaffolds were synthetized by one-step gas foaming process. PU foams were coated with crosslinked gelatin hydrogel to promote cell adhesion and proliferation for the regeneration of soft tissues (e.g., adipose tissue). PU foams were coated with inorganic coating (i.e., CaPs) to improve the interaction with osteoblasts for bone tissue regeneration. The functionalized 3D PU porous scaffolds have been characterized investigating morphological properties by SEM and microCT, water uptake and coating stability, and compressive mechanical properties. Adipose tissue derived stem cells (ADSCs), endothelial cells (MS1), amnion mesenchymal cells (AMCs) and chorion mesenchymal cells (CMCs) isolated from human placenta were in vitro cultured on the hybrid functionalized 3D scaffolds. Mechanical properties showed elastic modulus ranging between 15.75 ± 2.14 and 22.9 ± 3.1 kPa; in vitro biological studies showed good cell adhesion, proliferation, and differentiation. In particular, compared to the results with uncoated PU, when cells where differentiated into adipocytes, Oil red O staining confirmed a higher presence of lipid droplets; in case of osteoblasts differentiation, inorganic extracellular matrix deposition was evidenced on CaPs coated PU. The obtained results suggest the important role of an adequate coating on the scaffold to stimulate a better interaction with cells, promoting the differentiation into different cells phenotypes.

  • Open access
  • 423 Reads
Properties of Bio-Materials Obtained from Milk Whey Proteins at Different pH Values and Plasticizer Concentrations
Published: 28 February 2019 by MDPI in 1st Coatings and Interfaces Web Conference session Biomaterial Surfaces & Interfaces

Milk whey (MW) represents the major by-product of cheese industry. One possibility to recycle the MW wastes is the use of their globular proteins (MWPs) as a polymer source for the production of biodegradable plastic materials. MWP-based films are usually obtained by protein heat treatment in the presence of glycerol (GLY) as plasticizer at pH 7, a method which would require commercially high costing process. In this work it was exploited the possibility to produce manageable MW-derived biomaterials without any heat-treatment but under alkaline conditions. Our results demonstrated that the casting at pH 12 of the unheated MWP film forming solutions (FFSs), containing either 40% or 50% GLY, led to produce more resistant and flexible biomaterials than the ones obtained at pH 7. Also film transparency was observed significantly improved, being lower in the samples obtained at alkaline pH without MWP heating and with higher GLY concentrations. Finally, moisture content decreased with the reduction of GLY content, both in heated and unheated MWP-based films, whereas water uptake of the different films prepared at pH 12 did not significantly change.

  • Open access
  • 294 Reads
Coating of Sub-Micrometric Keratin Fibers on Titanium Substrates: A Successful Strategy for Stimulating Adhesion and Alignment of Fibroblasts and Reducing Bacterial Contamination
Published: 28 February 2019 by MDPI in 1st Coatings and Interfaces Web Conference session Biomaterial Surfaces & Interfaces

Coatings are a versatile tool for modulation of the biological response of biomaterials; in particular, the use of biopolymers as coating material may improve cell interactions and tissue adhesion. Among others, keratin is a natural protein able to stimulate fibroblast cells effectively and has the ability to bind metal ions. Coatings of keratin fibers onto titanium substrates can improve soft tissue adhesion, eventually coupling topographical (contact guidance) and chemical stimulus through the alignment of the fibers along sub-micrometric grooves of the substrate. Sub-micrometric keratin fibers were obtained by electrospinning both in random and oriented arrangements (though a rotating collector); in addition, antibacterial properties were added by enrichment of the coating with silver ions. This type of coating can be of interest in transmucosal dental implants, where perimplantitis is often due to infection (biofilm formation) and disease worsening is due to inflammation of the surrounding soft tissue, which is guided by fibroblasts. Keratin fibres coatings were prepared and characterized by means of Field Emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), cell (gingival fibroblasts) and bacteria (S. aureus) culture tests. FESEM observations demonstrated the possibility to deposit keratin fibres onto titanium substrates in random or oriented arrangements effectively. Keratin fibres were able to increase fibroblast adhesion and proliferation. On randomly deposited keratin fibres, fibroblast cells were significantly biologically stimulated and showed high adhesion and proliferation, but not orientation ability; on the other hand, aligned keratin fibres on a grooved substrate were able to stimulate cells both from the topographical (orientation) and biological standpoint. Finally, Ag-doped keratin fibres coatings were able to reduce S. aureus adhesion significantly, maintaining high biocompatibility. Considering these results, keratin sub-micrometric fibres coatings are a promising strategy for stimulating fibroblasts and reducing bacterial contamination.

  • Open access
  • 776 Reads
Improving the health quality of fried falafel (Middle Eastern food) by using transglutaminase and/or pectin coating

The most disadvantage of the fried falafel balls are the highest level of acrylamide formed during Maillard reaction. Falafel balls are one of the largest deep fat frying fast food in the Middle East made basically of chickpeas. The main aim of this study was to investigate the effect of adding transglutaminase (TG, E.C. to the falafel dough followed or not by dipping into pectin (PEC 1%) coating solution. Acrylamide, oil and water content of the fried falafel balls treated or not by TG (5 or 20U/g of chickpea proteins) and coated or not with PEC-containing film forming solutions were evaluated. In addition, the texture profile analyses were carried out. We observed, by TOF LC/MS, that the acrylamide content was reduced, compared to control sample, by 10.8% and 34.4% in the samples set up by adding 5 and 20 U TG/g respectively. In PEC-coated samples, acrylamide reduction was about by 59%, 65.3% and 84.5%, in falafel balls prepared either without of TG or containing 5U or 20 U of the enzyme, respectively, suggesting that TG-mediated crosslinks increase the water content inside the falafel balls, thus, reducing the rate of Maillard reaction. However, TG treatment does not affect oil content, while the PEC coating reduces the oil uptake about 23.5%. Finally, no difference was observed between the control sample and the one dipped in PEC regarding their texture properties hardness, chewiness and gumminess, while these properties were influenced in samples set up in the presence of the enzyme.

  • Open access
  • 169 Reads
Implementation of superhydrophobic PS electrospun nano/microfibers for corrosion protection of aluminum substrates
Published: 03 March 2019 by MDPI in 1st Coatings and Interfaces Web Conference session Posters

In this work, the electrospinning technique is used for the synthesis of micro/nanofibers using a polymeric precursor with hydrophobic (even superhydrophobic) behaviour such as polystyrene (PS) or polyvinyl chloride (PVC). These electrospun fibers are deposited onto aluminum substrates (6061T6). The effect of varying the different electrospinning deposition parameters (mostly applied voltage and flow-rate) will be exhaustively analyzed in order to optimize the resultant electrospun coatings. Several fiber characterization tests have been performed, including Field Emission Scanning Electron Microscopy (FE-SEM), Atomic Force Microscopy (AFM), Termogravimetric analysis (TGA), Optical Microscopy (OM) and Water Contact Angle (WCA) measurements. Furthermore, the anti-corrosion properties of these electrospun coatings can be enhanced by the addition of metal oxide nanoparticles (ZnO) which act as corrosion inhibitors. Finally, electrochemical corrosion tests (Tafel and pitting tests) have been perfomed, showing an improvement in the resultant corrosion resistance of the aluminum alloys coated by the combination of both polymeric film with metal oxide inorganic nanoparticles.

  • Open access
  • 110 Reads
Estimation of the range extension of the milage of the electric vehicles by the automotive-colored car-roof photovoltaic
Published: 03 March 2019 by MDPI in 1st Coatings and Interfaces Web Conference session Posters

A car-roof photovoltaic has enormous potential to change our society. With this technology, 70% of a car can run on the solar energy collected by the solar panel on its roof.

Since it is to be accepted the majority of the customers, it should be painted as the normal car-painting. This paper estimated the energy yield loss by the automotive painting and setting the goal of the energy conversion efficiency with coated photovoltaic on the car-roof.

The estimation is not as simple as the spectroscopic transparency calculation but needs to consider angular weighting, the curvature of the panel, mismatching loss by the advanced multi-junction solar cells. To estimate the practical value of the target performance, we first monitored the PV module using three-junction solar cell (30 % efficiency) in outdoor for three years. We also developed the new energy yield model, because the conventional model only considers irradiance and temperature.

The newly-developed model successfully explained the seasonal trend of the energy yield of the spectrum-and-angular sensitive three-junction photovoltaic module. We also combined the ray-tracing simulation for consideration of the curvature of the car-roof. With the new and validated (by 3 years) energy generation model, we could define the target base PV efficiency for several car-painting, like blue, gold, red, green and grey.

  • Open access
  • 148 Reads
Surface Modification of Austenitic Stainless Steel by means of Low Pressure Glow-Discharge Treatments with Nitrogen

When low temperature nitriding of austenitic stainless steels is carried out, it is very important to remove the surface passive layer for obtaining homogeneous incorporation of nitrogen. In glow-discharge nitriding technique this surface activation is performed by cathodic sputtering pre-treatment, which can heat also the samples up to nitriding temperature. This preliminary study investigates the possibility of producing modified surface layers on austenitic stainless steels by performing low pressure glow-discharge treatments with nitrogen, similar to cathodic sputtering, so that surface activation, heating and nitrogen incorporation can occur in a single step having a short duration (up to about 10 min). Depending on treatment parameters, it is possible to produce different types of modified surface layers. One type, similar to that obtained with low temperature nitriding, consists mainly of S phase and it shows improved surface hardness and corrosion resistance in 5% NaCl solution in comparison with the untreated steel. Another type has large amounts of chromium nitride precipitates, which cause a marked hardness increase but a poor corrosion resistance. These surface treatments influence also water wetting properties, so that the apparent contact angle values become >90°, indicating a hydrophobic behaviour.

  • Open access
  • 169 Reads
Surface Coating and functionalization of Metallic Biomaterials with Essential Oils for Antibacterial Applications

Essential oils (EO) are complex mixtures of natural molecules with a great activity against bacteria, virus and fungi. Despite their wide use in folk medicine, their employment in medicine or in biomedical products is still scarce and there are only few studies in literature. Their antibacterial and anti-adhesive properties are of interest for the development of coatings or functionalization of implant surfaces, but also for non-implantable medical devices, with the advantage of a reduced bacterial contamination, without the risk of developing bacteria resistance. For a first attempt, a peppermint essential oil was used in this research. The aim of the work was to functionalize or to coat the surface of different materials (Ti6Al4V, Steel 316L) with different surface finishing (grinded, polished, and chemically-treated). The obtained samples were characterized by means of XPS, FTIR, Fluorescent microscope observations and tape test. These analyses highlighted the presence of grafted oil biomolecules, or of a coating, on all the substrates after the procedure of functionalization/coating with remarkable chemical stability (during soaking in water or washing with acid or basic solutions) and mechanical adhesion. The samples were also subjected to antibacterial tests selected in order to simulate non-implantable applications: the test showed a reduction of the adherent bacteria and their viability on coated surfaces. In conclusion, the research work shows the great potential of the use of essential oils for surface functionalization or coating of biomaterials to obtain enhanced antibacterial properties: according to the final application, different oils can be selected in order to obtain the desired effects.

  • Open access
  • 171 Reads
Nitrogen Rich Stainless Steel Coatings Obtained by RF Sputtering Process

Magnetron sputtering is a useful tool for producing coatings on various substrates at low temperature. The use of an austenitic stainless steel target in a nitrogen-containing plasma mixture allows to obtain nanostructured coatings with the formation of the so-called S phase, supersaturated interstitial solid solution of nitrogen in the expanded and distorted austenite lattice, which shows improved hardness and higher corrosion resistance in comparison with the bulk alloy. In the present research, RF magnetron sputtering deposition of austenitic stainless steel coatings using an AISI 316L target in nitrogen-containing plasma gas was studied. The effect of the N2/Ar gas ratio and the deposition temperature on nitrogen content, phase composition and crystallite size is investigated by mean of XPS, XRD and electron microscopy analyses. The results show that the nitrogen content in the resulting deposit slightly depends on the N2/Ar ratio in the chamber during the deposition, reaching a maximum value of about 35% with a 30% N2/Ar gas composition mixture in the chamber. Data obtained on different substrates are presented and a preliminary evaluation of the corrosion resistance behaviour is also reported.

  • Open access
  • 185 Reads
Enhancement of Tribological Behavior of ZrCN Coating

This paper focuses on tribological behavior of ZrCN coating on bearing steel substrates DIN 17230, 100Cr6 / 1.3505, fulfilling also roughness and adherence requirements. Two strategies are followed to achieve a reduction of coefficient of friction. Initially, a low roughness coating by using Physical Vapour Deposition (PVD sputtering process) is developed. At this stage, PVD conditions guarantying adherence step and avoiding drops generated during that process are achieved. A second strategy consisting of application of several polish post-processes is proposed. These polish post-processes pretend to reduce roughness keeping, at the same time, a proper adherence. Different post-process durations and conditions are analysed to achieve positive adherence results. Coated bearing samples obtained from the application of these two strategies are tested in friction test rigs. These tests concluded that there is not a significant improvement of friction performance by applying ZrCN coatings compared to bearing baseline.

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