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Coatings, Volume 2, Issue 1 (March 2012) – 3 articles , Pages 1-63

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1639 KiB  
Article
Polyurethane Organosilicate Nanocomposites as Blood Compatible Coatings
by Johnson H. Y. Chung, Menno L. W. Knetsch, Leo H. Koole, Anne Simmons and Laura A. Poole-Warren
Coatings 2012, 2(1), 45-63; https://doi.org/10.3390/coatings2010045 - 27 Feb 2012
Cited by 3 | Viewed by 8256
Abstract
Polymer clay nanocomposites (NCs) show remarkable potential in the field of drug delivery due to their enhanced barrier properties. It is hypothesised that well dispersed clay particles within the polymer matrix create a tortuous pathway for diffusing therapeutic molecules, thereby resulting in more [...] Read more.
Polymer clay nanocomposites (NCs) show remarkable potential in the field of drug delivery due to their enhanced barrier properties. It is hypothesised that well dispersed clay particles within the polymer matrix create a tortuous pathway for diffusing therapeutic molecules, thereby resulting in more sustained release of the drug. As coatings for medical devices, these materials can simultaneously modulate drug release and improve the mechanical performance of an existing polymer system without introducing additional materials with new chemistries that can lead to regulatory concerns. In this study, polyurethane organosilicate nanocomposites (PUNCs) coated onto stainless steel wires were evaluated for their feasibility as blood compatible coatings and as drug delivery systems. Heparin was selected as the model drug to examine the impact of silicate loading and modifier chain length in modulating release. Findings revealed that better dispersion was achieved from samples with lower clay loadings and longer alkyl chains. The blood compatibility of PUNCs as assessed by thrombin generation assays showed that the addition of silicate particles did not significantly decrease the thrombin generation lag time (TGT, p = 0.659) or the peak thrombin (p = 0.999) of polyurethane (PU). PUNC coatings fabricated in this research were not cytotoxic as examined by the cell growth inhibition assay and were uniformly intact, but had slightly higher growth inhibition compared to PU possibly due to the presence of organic modifiers (OM). The addition of heparin into PUNCs prolonged the TGT, indicating that heparin was still active after the coating process. Cumulative heparin release profiles showed that the majority of heparin released was from loosely attached residues on the surface of coils. The addition of heparin further prolonged the TGT as compared to coatings without added heparin, but a slight decrease in heparin activity was observed in the NCs. This was thought to be from competitive interactions between clay-heparin that influenced the formation of the ternary complex between heparin, ATIII thrombin. In summary, the feasibility of using PUNC as drug delivery coatings was shown by the good uniformity in the coating, absence of by-products from the coating process, and the release of active molecules without significantly interfering with their activity. Full article
(This article belongs to the Special Issue Advances in Medical Device Coatings)
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8413 KiB  
Article
Ion-Induced Surface Modification of Magnetically Operated Contacts
by Karen Arushanov, Igor Zeltser, Sergey Karabanov, Rafail Maizels, Evgeny Moos and Alexander Tolstoguzov
Coatings 2012, 2(1), 8-44; https://doi.org/10.3390/coatings2010008 - 24 Feb 2012
Cited by 5 | Viewed by 7043
Abstract
A study has been made of permalloy (iron-nickel) contacts of reed switches before and after ion-induced surface modification using atomic force and optical microscopy, Auger electron and X-ray photoelectron spectroscopy. It has been found that the formation of surface nitride layers enhances corrosion [...] Read more.
A study has been made of permalloy (iron-nickel) contacts of reed switches before and after ion-induced surface modification using atomic force and optical microscopy, Auger electron and X-ray photoelectron spectroscopy. It has been found that the formation of surface nitride layers enhances corrosion and erosion resistance of contacts. We proposed to produce such layers directly into sealed reed switches by means of pulsing glow-discharge nitrogen plasma. Full article
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176 KiB  
Article
Electroplated Coatings for Magnetically Operated Contacts (Reed Switches)
by Lyudmila Shishkina, Olga Lokshtanova and Sergey Karabanov
Coatings 2012, 2(1), 1-7; https://doi.org/10.3390/coatings2010001 - 23 Dec 2011
Cited by 9 | Viewed by 5798
Abstract
Electroplated coatings for reed switches were developed and investigated. The optimal compositions of industrial electrolytes currently used in the mass production of reed switches were given. The pros and cons of the different electroplated coatings, including those containing precious metals and with barrier [...] Read more.
Electroplated coatings for reed switches were developed and investigated. The optimal compositions of industrial electrolytes currently used in the mass production of reed switches were given. The pros and cons of the different electroplated coatings, including those containing precious metals and with barrier layers of base metal alloys, were discussed. Full article
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