Cold Plasma Systems and Their Application in Surface Treatments for Medicine

In this paper, a review of cold plasma setups and the physical and chemical processes leading to the generation of active species is presented. The emphasis is given to the interaction of cold plasmas with materials used in medical applications, especially medical implants as well as live cells. An overview of the different kinds of plasmas and techniques used for generation of active species, which significantly alter the surface properties of biomaterials is presented. The elemental processes responsible for the observed changes in the physio-chemical properties of surfaces when exposed to plasma are described. Examples of ongoing research in the field are given to illustrate the state-of-the-art at the more conceptual level.     

Surface Modification Strategies to Improve the Osseointegration of Poly(etheretherketone) and Its Composites

In the last 5 years, a wide variety of surface modification strategies are explored to improve the integration of poly(etheretherketone) (PEEK) implants with bone. Since PEEK does not support bone on‐growth, its surface properties need to be tailored to promote osteogenesis at the bone‐implant interface. Surface modifications applied to achieve this response range from simple surface morphology changes to the deposition of osteoconductive coatings. Of the many methods, titanium and/or hydroxyapatite coatings, extrusion to create surface pores, and an accelerated neutral atom beam treatment have been approved by the U.S. Food and Drug Administration to improve the integration of PEEK spinal cages. The success of these surface modifications brings hope for the clinical translation of other techniques in the future, but there are several limitations that may be preventing other treatments from reaching the clinic. This review describes numerous strategies that have been applied to PEEK‐based implants for improving their osseointegration and enhancing their antibacterial properties. The review concludes with a discussion about future directions for the field and provides suggestions for advancing clinical translation of surface‐modified PEEK implants to improve the lives of patients in need of these implants.     

In vitro biological performances of phosphorylcholine-grafted ePTFE prostheses through RFGD plasma techniques

Arterial prostheses made of microporous Teflon (ePTFE) are currently used in vascular surgery as bypasses for small and medium vessels. However, several clinical complications, such as thrombosis, frequently occur in these prostheses when implanted in humans. In this work, an original strategy was developed to improve the hemocompatibility of ePTFE prostheses, based on glow-discharge surface modification followed by chemical grafting of phosphorylcholine, known for its hemocompatible properties. This procedure leads to a covalent attachment of the molecules, therefore preventing their removal by shear stress induced by blood flow at the implant wall. The improvement of the blood compatibility properties of the modified ePTFE arterial prostheses have been investigated by in vitro tests such as thromboelastography, neutrophil adsorption, platelet aggregation, and cell cultures. These in vitro tests put in evidence that thrombogenicity index, platelet aggregation, and neutrophil adhesion were decreased by the molecule grafted on the prostheses. Moreover, the cell growth on the surface of the PRC-grafted prostheses was greatly enhanced in comparison to the virgin prosthesis. Based on these results, it could be concluded that PRC grafting on ePTFE prostheses permit to improve in vitro hemocompatibility and biocompatibility in comparison with their virgin counterpart.     

Composites Based on Polytetrafluoroethylene and Detonation Nanodiamonds: Filler–Matrix Chemical Interaction and Its Effect on a Composite’s Properties

Specific properties of PTFE composites filled with ultradisperse detonation diamonds (UDDs) with different surface chemistries are studied. It is found for the first time that filler in the form of UDDs affects not only the rate of PTFE thermal decomposition in vacuum pyrolysis, but also the chemical composition of the products of degradation. The wear resistance of UDD/PTFE composites is shown to depend strongly on the UDD surface chemistry. The presence of UDDs in a PTFE composite is found to result in perfluorocarbon telomeres, released as a readily condensable fraction upon composite pyrolysis. The chemical interaction between PTFE and UDDs, characterized by an increase in the rate of gas evolution and a change in the desorbed gas’s composition, is found to occur at temperature as low as 380°C. It is shown that the intensity of this interaction depends on the concentration of oxygen-containing surface groups, the efficiency of UDDs in terms of the composite’s wear resistance being reduced due to the presence of these groups. Based on the experimental data, a conclusion is reached about the chemical interaction between UDDs and a PTFE matrix, its dependence on the nanodiamond surface chemistry, and its effect on a composite’s tribology.     

Material stability investigation of polyamide material before and after laser sintering

Abstract

Polymers are the long chain organic materials that are held together by directional covalent bonds. These kind of organic materials are either synthesized or naturally obtained and they have wide range of application in the medical field due to its physical properties, chemical properties and multifarious processing technique. For the past two decade, these polymers were used to produce variety of medical devices and implants by laser sintering. Since laser based additive manufacturing technique was a thermal process, there may be a change in the material property after sintering and which may affect the usage of the polymer in medical field. This work presented here aims to investigate the material property of biocompatible eos PA12 polymer powder and a laser sintered part. The Scanning Electron Microscope (SEM) with Energy Dispersive Spectroscopy (EDAX), Fourier Transform Infrared Spectroscopy (FT-IR), X-Ray Diffraction (XRD) and Differential Scanning Calorimeter (DSC) analysis were carried out to investigate the properties. The experimental investigation carried out in order to get insight into laser-material interaction and the corresponding results indicated that the laser energy influences the material properties of polyamide powder.     

聚四氟乙烯膜分离技术在含油废水处理中的应用进展

世界生态环境逐渐恶化,为保护生态环境,含油废水的无害化处理排放成为保护生态环境的必要做法。膜处理技术作为20世纪最具发展前景的污水处理技术之一,具备低能耗,分离效率高等特点。聚四氟乙烯薄膜（PTFE）膜由于其具有的极高化学稳定性、良好的力学性能、过滤速度高、使用寿命长等特点,被广泛应用于水处理领域。为此本文概述膜分离原理,结合膜本身特点和改性方法,重点对PTFE膜及其改性膜在含油废水中的应用进行综述,并探讨了PTFE膜在应用过程中亟待解决的问题,为PTFE膜及其改性膜在水处理中的应用提供技术和理论支持。     

Multifunctional cold spray coatings for biological and biomedical applications: A review

A variety of coating techniques are available for medical devices to be tailored with surface properties aimed at optimizing their performance in biological environments. Cold spray, as a member of the thermal spray family, is now being exploited to efficiently deposit micro- to nanometer sized metallic or non-metallic particles on surgical implants, medical devices and surfaces in the healthcare environment to create functional coatings. Cold spray has attracted attention in the context of biomedical applications due to the fact that multiple materials can be combined easily at the surface of these devices, and that oxygen-sensitive and heat-sensitive organic molecules, including bioactive compounds, can be incorporated in these coatings due to the relatively low temperatures used in the process. The ability to maintain material and chemical properties and the ability to create functional coatings make the cold spray process particularly suitable for applications in the MedTech industry sector.This review explores the fabrication of cold spray coatings including the types of materials that have been used for biomedical purposes, provides a detailed analysis of the factors affecting cold spray coating performance, and gives an overview over the most recent developments related to the technology. Cold spray coatings that have been used until this point in time in biomedical applications can be broadly classified as biocompatible coatings, anti-infective coatings, anti-corrosive coatings, and wear-resistant coatings. In addition, this review discusses how these applications can be broadened, for example by providing antiviral effect against coronavirus (COVID-19). While we highlight examples for multifunctional cold spray coatings, we also explore the current challenges and opportunities for cold spray coatings in the biomedical field and predict likely future developments.     

Thermal Analysis of the Poly(Siloxane)–Poly(Tetrafluoroethylene) Coating System

Thermal properties of poly(siloxane)–poly(tetrafluoroethylene) (SIL–PTFE) system were investigated, using Perkin Elmer DSC-7 differential scanning calorimeter and TGA-7 thermogravimetric analyzer. For SIL–PTFE compositions, one glass transition temperature T _g has been found, in accordance with the reciprocal rule up to about 40 mass% of PTFE. However, for higher PTFE contents, T _g values about –118 to –112°C were observed that can be ascribed to motions of cross-linked SIL structures. Endo- and exothermic transitions, found in the range from 70 to 290°C, not observed for pure SIL and PTFE components, are considered as specific ones for the SIL–PTFE semi-IPN structures. The SIL–PTFE system, as well as its components, is thermally stable, if degradation reactions are considered; the temperatures of decomposition at the maximum decomposition rate were above 530°C. It has been found that the thermal stability of the SIL–PTFE system is increasing with the increase of the PTFE content. This revised version was published online in August 2006 with corrections to the Cover Date.     

Compressive ratcheting effect of expanded PTFE considering multiple load paths

Uniaxial stress-controlled ratcheting behaviors of expanded PTFE (ePTFE) under cyclic compressive loads were tested. The effects of temperature, stress rate and mean stress on the ratcheting behaviors of ePTFE considering multiple load paths were discussed in detail. Results present that the steady ratcheting strain is rate-independent when the stress rate is less than about 0.1 MPa/s, while it approximately linearly decreases with increasing the stress rate for greater stress rate. Additionally, the steady ratcheting is temperature-independent when the temperature is greater than about 150 °C, but it nearly linearly increases with enhancing the temperature for lower temperature. Especially, the stress rate almost has little effect on the ratcheting strain of ePTFE at 200 °C. Moreover, the accumulated ratcheting strain enhances rapidly in about the first 80 cycles, and subsequently tends to shakedown in the subsequent cycles for each load path. Furthermore, if a higher stress is used in the prior cycling, the greater ratcheting strain may be produced, and a negative ratcheting strain rate can be obtained in the subsequent cycling with lower mean stress due to the greater strain hardening and deformation resistance produced by the previous higher stress.     

Thermal decomposition of PTFE in the presence of silicon,calcium silicide,ferrosilicon and iron

Simultaneous TG/DTA has been used to study the thermal decomposition of binary compositions containing polytetrafluoroethene (PTFE) with silicon (Si), calcium silicide (CaSi₂), ferrosilicon (FeSi) or iron (Fe) powders. In nitrogen and under dynamic heating program the thermal decomposition of Si/PTFE and CaSi₂/PTFE is an exothermic process. The other two compositions decompose endothermically. In each case the decomposition reactions show first-order kinetics but only iron does not change considerably the kinetics of PTFE depolymerization. The constants of the decomposition rate at 850 K for silicon containing reducers are about four times higher than those of PTFE and Fe/PTFE. This revised version was published online in July 2006 with corrections to the Cover Date.     

Poly(tetrafluoroethylene) separation capillaries for capillary electrophoresis. Properties and applications

Poly(tetrafluoroethylene) (PTFE) is a material widely known for its inertness and excellent electrical properties. It is also transparent in the UV region and has a reasonable thermal conductivity. These properties make PTFE a suitable material for the separation capillary in capillary electrophoresis. Differences in the chemistry of the capillary wall compared to fused silica (FS) can make PTFE an interesting alternative to FS for some special applications. In this work, properties of a commercial PTFE capillary of approx. 100 microm i.d. were investigated, including the dependence of electroosmotic flow (EOF) on pH for unmodified and dynamically modified PTFE, optical properties, and practical aspects of use. The main problems encountered for the particular PTFE capillary used in this study were that it was mechanically too soft for routine usage and the crystallinity of the PTFE caused light scattering, leading to high background absorbance values in the low UV region. The profile of the EOF versus pH for bare PTFE surprisingly showed significantly negative EOF values at pH < 4.2, with an EOF of -30 x 10(-9) m2 V(-1) s(-1) being observed at pH 2.5. This is likely to be caused by either impurities or additives of basic character in the PTFE, so that after their protonation at acidic pH they establish a positive charge on the capillary wall and create a negative EOF. A stable cationic semi-permanent coating of poly(diallyldimethylammonium chloride) (PDDAC) could be established on the PTFE capillary and led to very similar magnitudes of EOF to those observed with FS. A hexadecanesulfonate coating produced a cathodic EOF of extremely high magnitude ranging between +90 and +110 x 10(-9) m2 s(-1) V(-1), which are values high enough to allow counter-EOF separation of high mobility inorganic anions. In addition, pH-independent micellar electrokinetic capillary chromatography (MEKC) separations could be easily realised due to hydrophobic adsorption of sodium dodecylsulfate (used to form the micelles) on the wall of the PTFE capillary. The use of polymers that would be mechanically more robust and optically transparent in the low-UV region should make such CE capillaries an interesting alternative to fused silica.     

Fractionated crystallization in blends of functionalized poly(tetrafluoroethylene) and polyamide

Blends of poly(tetrafluoroethylene)/polyamide (PTFE/PA) were prepared to combine the good processing properties of PA with the excellent sliding properties of PTFE. For the compatibilizing of the immiscible components the chemical reaction of functional groups of modified PTFE (micro powder produced by electron irradiation in air) and polar PA during a reactive extrusion process was used. The parameter influencing the efficiency of the in‐situ reaction between both components were varied. The crystallization and melting behaviour of the different blends was investigated by DSC. In dependence on the degree of compatibilization the phenomenon of fractionated crystallization of the dispersed PTFE component was observed. In this way a qualitative characterization of the dispersity of PTFE in dependence on the functionality of the components and the processing conditions is possible, and therefore an estimation of the efficiency of the in‐situ reaction.     

Friction and Wear of Semi-Crystalline Polytetrafluoroethylene with Spherulitic Micro-Morphology

Polytetrafluoroethylene (PTFE) is an important engineering material with a low coefficient of friction but a high rate of wear. As a semi‐crystalline polymer, its wear resistance is related to its micro‐morphology. Friction and wear properties of semi‐crystalline non‐spherulitic PTFE have been widely studied, but no investigation is reported about tribological properties of spherulitic PTFE due to difficulties in finding such properties. In this paper, friction and wear properties of PTFE with spherulitic micro‐morphology are studied for the first time. The results show that, first, under the same experimental condition, when two kinds of PTFE are rubbed against the steel disc, the number and size of debris of spherulitic PTFE are much less and smaller than that of debris of PTFE without spherulitic crystals. This means that the wear resistance of spherulitic PTFE is better than that of semi‐crystalline PTFE without spherulitic micro‐morphology. Second, the friction property of spherulitic PTFE is also different from that of PTFE without spherulitic crystals. Finally, the friction and wear mechanisms of spherulitic PTFE and non‐spherulitic PTFE are compared.     

Molecular-Level Reinforced Adhesion Between Rubber and PTFE Film Treated by Atmospheric Plasma Polymerization

Extremely strong reinforced adhesion between a polytetrafluoroethylene (PTFE) film and butyl rubber is achieved using an atmospheric pressure plasma graft polymerization, involving argon and acrylic acid vapor. The treated PTFE film is then placed over a raw butyl rubber plate and hot-pressed under 157 N/cm² for 40 min at 150 °C or for 10 min at 180 °C. This procedure results in molecular-level or chemical adhesion between the butyl rubber and the PTFE film. The 180° peeling test results show that a high peeling strength of 3.9 N, per 1 mm sample width, is achieved. Adherend failure of the rubber sheet occurs when the peeling is enforced. From X-ray photoelectron spectroscopy analysis of the treated films, chemical bonds with fluorine atoms are absent from the surface. From scanning electron microscopy analysis, a transparent hydrophilic poly(acrylic acid) layer composed of nanoscale spherical particles is formed. This PTFE-rubber composite material is suitable for high-quality, prefilled medical syringe gaskets.     

Preparation and characterization of polytetrafluoroethylene‐polyacrylate core–shell nanoparticles

Polytetrafluoroethylene (PTFE)‐polyacrylate core–shell nanoparticles were produced by using PTFE micropowder and acrylate via seeded emulsion polymerization in the presence of fluorosurfactant. The properties of emulsion under various polymerization conditions were investigated and optimized. The chemical composition of the PTFE‐polyacrylate nanoparticles was characterized by Fourier‐transform infrared spectrometry (FTIR). The particle size and core–shell structure of the resulting PTFE‐polyacrylate nanoparticles were confirmed by transmission electron microscopy (TEM). Wettability of the PTFE‐polyacrylate core–shell particles was higher than the pristine PTFE. The formation of this kind of PTFE‐polyacrylate core–shell nanoparticles could improve the compatibility of PTFE with other materials because PTFE is covered by polyacrylate shell, which make them promising in various fields. Copyright © 2007 John Wiley & Sons, Ltd.     

Hydrogels and vascular grafts-state of the art and beyond

Vascular grafts represent significant part of implantable medical devices. While the autologous grafts utilizing saphenous veins are used exclusively in cardiac artery bypass graft (CABG) procedures and in peripheral indications, polymer-based grafts are widely used to replace diseased vasculature with internal diameter above 6 mm. The PET yarn is either knitted or woven into tubes of controlled patterns and porosity. The PTFE tubes are expanded into porous conduits (ePTFE) and the polyurethanes are spun, wound, dipped and foamed to produce porosities most suited for the healing. This porosity causes the blood to leak through the graft wall or at anastomosis through the suture holes. Both the wall leakage and suture hole bleeding remain rather serious drawbacks. Currently, collagen, gelatin, albumin and their derivatives are used as sealants. Various modes of application and degree of crosslinking are utilized to control in vivo degradation and graft healing. Enhancement of graft patency via improvement of initial hemocompatibility could be achieved by application of bioactive coatings. Heparinized systems seem to dominate in this field but many new concepts are being investigated. Intraluminal endothelization via endothelial cells seeding and mediating biologicals will open significant potential for synthetic grafts with ID well below 6 mm. Porous biodegradable tubes could be used as temporary scaffold to attract and promote cell propagation and ingrowth, the true angiogenesis. High-swelling hydrogels could play a significant role both as sealants and modifiers of graft bioperformance. This paper discusses concepts and potentials needed for patent “small caliber” graft.     

Host Responses to Biomaterials and Anti‐Inflammatory Design—a Brief Review

Host responses toward foreign implants that lead to chronic inflammation and fibrosis may result in failure of the biomedical device. To solve these problems, first a better understanding of the biomaterial‐induced host reactions including protein adsorption, leukocyte activation, inflammatory and fibrotic responses to biomaterials is required; second an improved design of biomaterial surfaces is needed that results in an appropriate host response, causing less inflammatory response, and supporting tissue regeneration. Hence, this review provides a brief overview on the host response to implants, as well as in vitro models to study inflammatory and fibrotic responses to biomaterials to predict the clinical outcome of implantation. Moreover, the review highlights anti‐inflammatory strategies to improve the biocompatibility of implants, which contain the modification of physicochemical surface properties of materials as well as the immobilization of anti‐inflammatory reagents and bioactive molecules on biomaterials.     

Effect of cold plasma process on the surface wettability of NBR and the kerosene resistance of NBR/PTFE composites

In this study, first the acrylonitrile‐butadiene rubber (NBR5080) was modified by argon (Ar), air, and oxygen plasma at low temperature, and the effect of plasma process (power, time, and pressure) on the surface properties of NBR5080, the interfacial properties, physical properties, and the mechanical properties of NBR5080/polytetrafluoroethylene (PTFE) composites were investigated. The state contact angle and the surface free energy were applied to characterize the surface wettability of NBR5080. The scanning electron microscope and the atomic force microscope were used to observe the surface morphology of the NBR5080. The chemical changes on the NBR5080 surface were verified by X‐ray photoelectron spectroscopy. The average water contact angle the NBR5080 declined obviously when NBR5080 was treated by Ar (100 W/600 s/30 Pa). The active oxygen groups were introduced onto the surface of NBR5080 by cold plasma treatment and more active group containing oxygen were observed on the samples treated by Ar plasma. The peel strength between the NBR5080 and the PTFE was increased obviously, which increased from 0 to 44.2 N?m^?1 for Ar plasma treatment. The mass and the dimension of NBR5080 increase sharply after immersing in kerosene, whereas the NBR5080/PTFE composites changed a little. The mechanical properties of NBR5080 and NBR5080/PTFE composites decreased as the immersion time in kerosene increased, but the decreased degree of NBR5080 is higher than NBR5080/PTFE composites.     

Bone Grafts and Substitutes in Dentistry: A Review of Current Trends and Developments

After tooth loss, bone resorption is irreversible, leaving the area without adequate bone volume for successful implant treatment. Bone grafting is the only solution to reverse dental bone loss and is a well-accepted procedure required in one in every four dental implants. Research and development in materials, design and fabrication technologies have expanded over the years to achieve successful and long-lasting dental implants for tooth substitution. This review will critically present the various dental bone graft and substitute materials that have been used to achieve a successful dental implant. The article also reviews the properties of dental bone grafts and various dental bone substitutes that have been studied or are currently available commercially. The various classifications of bone grafts and substitutes, including natural and synthetic materials, are critically presented, and available commercial products in each category are discussed. Different bone substitute materials, including metals, ceramics, polymers, or their combinations, and their chemical, physical, and biocompatibility properties are explored. Limitations of the available materials are presented, and areas which require further research and development are highlighted. Tissue engineering hybrid constructions with enhanced bone regeneration ability, such as cell-based or growth factor-based bone substitutes, are discussed as an emerging area of development.     

Study of new protective clothing against SARS using semi-permeable PTFE/PU membrane

Chemicals which may pose a hazard to people upon contact may be in several forms, such as liquid, mist, vapor, etc. The damage caused can range from mild skin diseases to more serious chronic illnesses. Therefore, chemical protective clothing must be used to safe some personal who may be exposed to hazardous chemicals. The use of PTFE/PU membrane for chemical protective clothing is discussed in the article. By means of texturing with organic conductive fiber, and then treating with JAM-Y1 anti-bacteria agent, in the end, treating with the XL-550 waterproof agent, the PET fabric has permanent anti-static, anti-bacteria and waterproof and anti-oil properties. The PTFE/PU protective material is prepared by laminating with PET fabric by paste dot coating, and then coated by PU solution in a direct process. The PU coating agent, DMF and acetone, are used in testing through surface tension and peeling strength measurement. The penetration property of poliomyelitis virus in liquid and animalcule in air of PTFE membrane laminated textile, after being coated by PU solution are measured. The results show that it can separate SARS virus in air and liquid, and WVT is 11496 g/24 h m². Then it can provide a satisfactory wearing comfort.