An in vivo study of the host response to starch-based polymers and composites subcutaneously implanted in rats

Implant failure is one of the major concerns in the biomaterials field. Several factors have been related to the fail but in general these biomaterials do not exhibit comparable physical, chemical or biological properties to natural tissues and ultimately, these devices can lead to chronic inflammation and foreign-body reactions. Starch-based biodegradable materials and composites have shown promising properties for a wide range of biomedical applications as well as a reduced capacity to elicit a strong reaction from immune system cells in vitro. In this work, blends of corn starch with ethylene vinyl alcohol (SEVA-C), cellulose acetate (SCA) and polycaprolactone (SPCL), as well as hydroxyapatite (HA) reinforced starch-based composites, were investigated in vivo. The aim of the work was to assess the host response evoked for starch-based biomaterials, identifying the presence of key cell types. The tissues surrounding the implant were harvested together with the material and processed histologically for evaluation using immunohistochemistry. At implant retrieval there was no cellular exudate around the implants and no macroscopic signs of an inflammatory reaction in any of the animals. The histological analysis of the sectioned interface tissue after immunohistochemical staining using ED1, ED2, CD54, MHC class II and alpha/beta antibodies showed positively stained cells for all antibodies, except for alpha/beta for all the implantation periods, where it was different for the various polymers and for the period of implantation. SPCL and SCA composites were the materials that stimulated the greatest cellular tissue responses, but generally biodegradable starch-based materials did not induce a severe reaction for the studied implantation times, which contrasts with other types of degradable polymeric biomaterials.     

Fabrication and In vitro Bioactivity of Robust Hydroxyapatite Coating on Porous Titanium Implant

Compared witli the traditional dental implant, TixOs■ manufactured by direct laser metal forming(DLMF) technology exhibits improved capability for bone osteointegration due to its porous surface structure, and has achieved remarkable clinical effect. However, like the traditional titanium and other alloyed implants, the porous titanium implant TixOsR also has relatively weak bioactivity. To address this issue, a proper surface modification method may be needed. Hydroxyapatite(HA) has been widely used in implant surface coating for its similar chemical composition to bone tissue and its osteoconductive properties. Thus, combining TixOs■ implants with hydroxyapatite can be an efficient way to enhance their bioactivity. We herewith reported a competent pulsed laser deposition(PLD) method of coating nano-sized HA thin film onto the porous TixOs■ implant. The HA coatings were characterized by means of scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy(EDS), X-ray photoelectron spectroscopy(XPS) and focused ion beam(FIB) method, and nanocrystal sized thin HA films were identified on the surface of TixOs■ implants. The low cytotoxicity and improved cell proliferation ability of HA coated implants were further tested and verified using MC 3T3 E1 cells with the consideration of the controlling group. Our results show that a stable and bioactive HA tliin film is able to form on the surtace of the porous titanium implant by PLD method.This may benefit the fiirther clinical application of TixOs■ implants.     

Study on the Friction and Wear Properties of PEEK against Cortical Bone Tissue Under Different Lubricating Conditions

The tribological behavior between orthopedic implants and cortical bone is important but usually neglected. Poly(ether-ether-ketone) (PEEK) is a promising material for orthopedic applications. To further understand and improve the interfacial tribological properties between PEEK implant and host bone tissue, a PEEK-cortical bone tribo-pair is designed and fabricated. The frictional and wear performance of such tribo-pair is investigated under different lubricants, i.e., simulated body fluid (SBF), calf serum (CS), hyaluronic acid (HA), and mucin (MUC). The results suggest that MUC solution can be utilized as an artificial natural synovial fluid to improve the tribological properties of PEEK-based implants.     

Recycling Nanowire Templates for Multiplex Templating Synthesis: A Green and Sustainable Strategy

Template‐directed synthesis of nanostructures has been emerging as one of the most important synthetic methodologies. A pristine nanotemplate is usually chemically transformed into other compounds and sacrificed after templating or only acts as an inert physical template to support the new components. If a nanotemplate is costly or toxic as waste, to recycle such a nanotemplate becomes highly desirable. Recently, ultrathin tellurium nanowires (TeNWs) have been demonstrated as versatile chemical or physical templates for the synthesis of a diverse family of uniform 1D nanostructures. However, ultrathin TeNWs as template are usually costly and are discarded as toxic waste in ionic species after chemical reactions or erosion. To solve the above problem, we conceptually demonstrate that such a nanotemplate can be economically recycled from waste solutions and repeatedly used as template.     

Water confined between sheets of mackinawite FeS minerals

Wet iron-sulfur minerals have been shown to be ideal environments to allow for simple chemical reactions to occur in nature, for instance, in the framework of prebiotic chemistry. Yet, not much is known about such water/mineral interfaces beyond those involving pyrite, FeS(2), which is, however, chemically rather inert. In contrast, mackinawite is chemically reactive and consists of a layered crystal structure comprising FeS sheets that can be easily cleaved. Here, the properties of water confined between such sheets in lamella-like setups is investigated in the spirit of surface science model systems. The properties of this intercalated water are found to depend significantly on the interlayer distance and change from "arrested water" (in the limit of small interlayer distances) to liquid-like behavior.     

Graphene quantum dots from chemistry to applications

Graphene quantum dots (GQDs) have been widely studied in recent years due to its unique structure-related properties, such as optical, electrical and optoelectrical properties. GQDs are considered new kind of quantum dots (QDs), as they are chemically and physically stable because of its intrinsic inert carbon property. Furthermore, GQDs are environmentally friendly due to its non-toxic and biologically inert properties, which have attracted worldwide interests from academic and industry. In this review, a number of GQDs preparation methods, such as hydrothermal method, microwave-assisted hydrothermal method, soft-template method, liquid exfoliation method, metal-catalyzed method and electron beam lithography method etc., are summarized. Their structural, morphological, chemical composition, optical, electrical and optoelectrical properties have been characterized and studied. A variety of elemental dopant, such as nitrogen, sulphur, chlorine, fluorine and potassium etc., have been doped into GQDs to diversify the functions of the material. The control of its size and shape has been realized by means of preparation parameters, such as synthesis temperature, growth time, source concentration and catalyst etc. As far as energy level engineering is concerned, the elemental doping has shown an introduction of energy level in GQDs which may tune the optical, electrical and optoelectrical properties of the GQDs. The applications of GQDs in biological imaging, optoelectrical detectors, solar cells, light emitting diodes, fluorescent agent, photocatalysis, and lithium ion battery are described. GQD composites, having optimized contents and properties, are also discussed to extend the applications of GQDs. Basic physical and chemical parameters of GQDs are summarized by tables in this review, which will provide readers useful information.     

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.     

Towards the nonstick egg: designing fluorous proteins

Anyone who has made scrambled eggs will have had cause to praise the properties of Teflon. Teflon's highly chemically inert and nonstick nature derives from the perfluorinated polymer polytetrafluoroethylene. Perfluorocarbons have unique and valuable physical properties not found in nature. By incorporating fluorine into proteins, it might be possible to produce biological molecules with novel and useful properties.     

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.     

Geographical and Geological Origin of Natural Graphite Heavily Influence the Electrical and Electrochemical Properties of Chemically Modified Graphenes

Natural graphite is an important precursor for the production of chemically modified graphenes in bulk quantities for electrochemical applications. These natural graphites have varying fundamental properties due to the different geological processes and environments at their points of origin, which are expected to affect their chemical reactivity and hence the properties of the derived graphene materials. Four different natural graphites with known geographical and geological origins were exposed to a modified Hummers oxidation method and the resulting graphite oxides were studied. The graphite oxides were shown to have different extents of oxidation and types of oxygen groups, which directly influenced their electrochemical properties. These differences were propagated further in the subsequent chemical reduction of the graphite oxides, and the reduced graphene oxides exhibited significantly different reduction efficiencies and electrical conductivities. These findings show that the choice of natural graphite of known origin is important to synthesize chemically modified graphenes with a desired set of properties.     

ePTFE functionalization for medical applications

Polytetrafluoroethylene (PTFE) is a ubiquitous material used in implants and medical devices in general due to its high biocompatibility and inertness; blood vessels, heart, jawbone, nose, eyes, or abdominal wall can benefit from its properties in the case of disease or injury. Its expanded version, ePTFE, is an improved version of PTFE with better mechanical properties, which extend its medical applications. However, ePTFE implants often lack improvement in properties such as antibacterial, antistenosis, or tissue integration properties. Improvements in these properties by several strategies of functionalization for medical purposes are discussed in this review. Covalent and non-covalent bonding are reviewed, including more specifically chemical impregnation, chemical surface modification, autologous vascularization, and cell seeding, which are strategies mainly used for improving the properties of ePTFE and are described in this review.     

An electrically driven jetting technique for diverse high-resolution surface structures of nanometre hydroxyapatite crystals

Nanometre hydroxyapatite (nHA) coated metallic materials have been successfully used for bone tissue implantation for several decades now due to its sound biological and mechanical properties. The microstructure and surface topography of the implant material are well-known to play a crucial role in influencing cellular responses to implants and bone tissue regeneration ultimately. Recently, a novel jet-based patterning technique, template-assisted electrohydrodynamic atomisation (TAEA) spraying, has been devised to prepare depositions with defined surface topography for guiding the cellular response. In this study, an improvement investigation of this patterning process was carried out to precisely control the nHA surface structure in terms of geographies and dimensions via an angular needle jetting during the patterning process. More importantly, the mechanism of such improvement of the TAEA patterning technique was also discussed and uncovered. A range of diverse nHA surface structures with high-resolution was therefore achieved, which paves the way for the research of the new generation implant materials with defined cellular response.     

Titanium levels in the organs and blood of rats with a titanium implant,in the absence of wear,as determined by double-focusing ICP-MS

Titanium (Ti) has long been regarded as an inert and biocompatible metal, ideal for biomedical applications such as dental implants or joint replacements. However, concerns about the biocompatibility of Ti have lately arisen. Unfortunately, information on reliable Ti baseline physiological levels in blood and organ tissues is still pending and the real effects of physiological corrosion as opposed to wear processes of Ti or Ti alloys implants is controversial so far. In this work a previously developed and validated methodology, based on using double-focusing inductively coupled plasma mass spectrometry (DF-ICP-MS) has been used to establish Ti basal levels in blood and organs (heart, liver, spleen, kidneys, and lungs) of Wistar rats. These data were compared with the levels found in three Wistar rats implanted with a Ti wire embedded in their femur for 18 months, in order to assign possible Ti released purely due to non-wear physiological mechanisms. Results showed that Ti content in all the selected organ tissues and blood was higher than previously determined Ti basal levels, clearly showing both corrosion of the Ti implant and systemic Ti accumulation in target tissues. These results indicate that Ti metal corrosion occurs. This seems to be the only mechanism responsible in the long term for the observed passive dissolution of Ti of the implant in the absence of wear. A comparative study of the systemic distribution of the soluble and particulate Ti potentially released from Ti implants was also carried out by intraperitoneally injection of soluble Ti(citrate)₃ and insoluble TiO₂ particles, respectively. Different systemic Ti storage was observed. Whereas soluble Ti was rapidly transported to all distal organs under study, TiO₂ particles were only accumulated in lung tissue.     

When gold is not noble: catalysis by nanoparticles

Bulk gold is chemically inert and is generally regarded as a poor catalyst. However, when gold is in very small particles with diameters below 10 nm and is deposited on metal oxides or activated carbon, it becomes surprisingly active, especially at low temperatures, for many reactions such as CO oxidation and propylene epoxidation. The catalytic performance of Au is defined by three major factors: contact structure, support selection, and particle size. The role of the perimeter interfaces of Au particles as the sites for reactions is discussed as well as the change in chemical reactivity of Au clusters composed of fewer than 300 atoms.     

Multi-Layer Pipes for Hydrocarbons Conveyance

The replacement of metals with plastics in piping systems is a well established practice in a vast range of public and industrial applications. However, difficulties still exist, mainly related to the limited chemical resistance of the polymers commonly used in pipe manufacturing to some conveyed fluids. This prevents using plastic pipes in important applications such as the transport of liquid hydrocarbons, particularly in oil fields. The use of chemically resistant polymers, such as fluorinated polyolefins, is precluded by high cost and poor mechanical properties. Co-extrusion of multi-layer pipes carrying an internal chemically resistant liner can be a viable alternative capable to extend the use of plastic pipes to refining and chemical industries. An experimental PE/PA multi-layer pipe has been developed whose resistance to diffusion and mechanical properties have been tested. Tests in real oil fields confirm the good performance of the new pipes.     

Acceleration of the corrosion reaction of magnesium by Fenton reagents

Abstract

Magnesium alloys have attracted increased attention for a variety of applications, chief among which are alternative energy and medical implants. The use of biodegradable implants in the complex system of the human body, in which myriad reactions occur, must consider the potential effects of the body’s natural chemical reactions on implant corrosion rates. The aim of this study was to elucidate the synergistic effects of pure Mg and Mg alloys on the Mg corrosion reaction with reagents that participate in the Fenton reaction. We corroborated our results with six different measurement methods (hydrogen evolution rate [HER], gas chromatography [GC], potentiodynamic polarization, inductively coupled plasma [ICP] spectrometry, Auger electron spectroscopy [AES], and scanning electron microscope [SEM]). The results point out that the corrosion and hydrogen evaluation rates of Mg were elevated by the addition of Fenton reagents, divalent iron and hydrogen peroxide, to a saline solution. In the context of Mg-based alloy medical implant development and use, this observation is significant.     

Recent advances in the research of bacterial glucuronosyltransferases

Many bacterial extracellular polysaccharides, which play an important role in various biological processes, contain glucuronic acid (GlcA) as a major component. Glucuronosyltransferase (GlcA-T) is the enzyme responsible for GlcA attachment in the biosynthesis of these polysaccharides. GlcA-T has recently attracted significant attention because of its biological activities as well as its potential application to chemoenzymatic synthesis of GlcA-containing oligosaccharides and polysaccharides that are difficult to achieve chemically due to the problems related to glycosylation reactions with GlcA. At present, nine GlcA-Ts derived from Xanthomonas campestris, Pasteurella multocida, Escherichia coli, Sphingomonas paucimobilis, and Streptococci have been characterized. This article reviews the recent progresses made in understanding the structures, functions, physical, and chemical properties of reported GlcA-Ts.     

Relative contributions from the kinetic and thermal characteristics of impurities and the inflammability of air-hydrogen mixtures

The effect of chemically active and inert impurities upon the concentration limits of flame propagation of air-hydrogen mixtures at atmospheric pressure is studied. The effect of impurities as a function of their thermal properties and the mechanism of the action on combustion is discussed. Combustion inhibition is considered a clear sign of the versatility of the one-stage reaction model used as the basis of thermal combustion theory.     

Toxication of Foreign Substances by Conjugation Reactions

Elucidation of the metabolic pathways of foreign compounds in mammalian organisms contributes substantially to the understanding of toxic effects and is therefore a basic component of every risk analysis. The abundance of chemical reactions which take part in metabolic transformations allows one to speculate that we, with our present state of knowledge, are just at the beginning of a development which will help explain the interplay between chemical structure, biochemical transformation and toxic effects. This applies in particular to the conjugation of foreign compounds with structures and molecules endogenous to the body. Until recently it was thought that these conjugation reactions lead to chemically and biologically inert products, which could be easily eliminated by the organism. Using new biological testing procedures and sensitive methods of analysis, this assumption has been refuted. The fact is, that highly toxic, mutagenic and carcinogenic products can result from the chemical interactions of foreign substances with endogenous substrates.