Editorial: Inorganic Biomaterials.

The intention of the editors A. R. Boccaccini and W. Höland has been to target this e-book to a broad readership and at the same time to present scientific contributions sufficiently detailed which discuss various specific fundamental aspects of inorganic biomaterials and their biomedical and dental applications. In this context, two large categories of biomaterials need to be mentioned, namely bioactive biomaterials for the replacement and regeneration of hard tissue and biocompatible, non-bioactive biomaterials for restorative dentistry. Both categories include products based on glasses or glass-ceramics as well as organic-inorganic composite materials. Among the bioactive products, BIOGLASS®, developed in the late 1960s by Prof. Dr. L. L. Hench, occupies a prominent position, being BIOGLASS® the first man-made material shown to form strong and functional bonding to leaving tissue. Sadly, Prof. Hench passed away in December 2015, at the time this e-book was being completed, it is therefore a great honor for the editors to dedicate this e-book to his memory. Indeed the book contains a comprehensive review written by Prof. Hench, in collaboration with Prof. J. R. Jones (UK), which provides a timely overview of the development and applications of bioactive glasses, including a discussion on the remaining challenges in the field. Further bioactive materials have been developed over the years by leading scientists such as Prof. Kokubo (Japan). These materials have also found their way into this book. The other contributions in this book, written by worldwide recognized experts in the field, present the latest advances in relevant areas such as scaffolds for bone tissue engineering, metallic ion releasing systems, cements, bioactive glass–polymer coatings, composites for bone regeneration, and effect of porosity on cellular response to bioceramics. In addition to bioactive materials, inorganic systems for restorative dentistry are also discussed in this e-book. Biomaterials for dental restorations consist of glassy or crystalline phases. Glass-ceramics represent a special group of inorganic biomaterials for dental restorations. Glass-ceramics are composed of at least one inorganic glassy phase and at least one crystalline phase. These products demonstrate a combination of properties, which include excellent aesthetics and the ability to mimic the optical properties of natural teeth, as well as high strength and toughness. They can be processed using special processing procedures, e.g. machining, moulding and sintering, to fabricate high quality products. The editors would like to extend their gratitude to the Frontiers team in Lausanne, Switzerland, for their outstanding dedication to make possible the publication of this e-book in a timely manner. It is our wish that the book will contribute to expand the field of inorganic biomaterials, both in terms of fundamental knowledge and applications, and that the book will be useful not only to established researchers but also to the increasing number of young scientists starting their careers in the field of inorganic biomaterials

Synthesis of monodispersed Ag-doped bioactive glass nanoparticles via surface modification

© 2016 by the authors.Monodispersed spherical Ag-doped bioactive glass nanoparticles (Ag-BGNs) were synthesized by a modified Stöber method combined with surface modification. The surface modification was carried out at 25, 60, and 80 °C, respectively, to investigate the influence of processing temperature on particle properties. Energy-dispersive X-ray spectroscopy (EDS) results indicated that higher temperatures facilitate the incorporation of Ag. Hydroxyapatite (HA) formation on Ag-BGNs was detected upon immersion of the particles in simulated body fluid for 7 days, which indicated that Ag-BGNs maintained high bioactivity after surface modification. The conducted antibacterial assay confirmed that Ag-BGNs had an antibacterial effect on E. coli. The above results thereby suggest that surface modification is an effective way to incorporate Ag into BGNs and that the modified BGNs can remain monodispersed as well as exhibit bioactivity and antibacterial capability for biomedical applications

Is non-buffered DMEM solution a suitable medium for in vitro bioactivity tests?

Several laboratories had tested bioactivity of the materials in commercially available solution DMEM (Dulbecco's Modified Eagle's Medium) that is normally used for cultivation of cell cultures. The objective of this work was to find out whether it is possible to replace TRIS-buffered SBF currently used for bioactivity tests with the non-buffered DMEM solution. To understand the role of the organic part of the DMEM solution in the process of crystallization, we have prepared non-buffered solution simulating only its inorganic part (identified as I-solution). It was found that under static-dynamic test conditions calcite (CaCO3) and the amorphous phase of calcium phosphate (ACP) formed on the surface of the glass-ceramic (45S5 bioactive glass based) scaffold exposed to both solutions. Additionally, halite (NaCl) formed at the beginning of exposure to DMEM. Hydroxyapatite phase was not detected on the surface in either non-buffered solution. Organic components contained in the DMEM solution failed to prevent formation of crystalline phases. The present results indicate that it is not recommendable to use DMEM for bioactivity tests of glass-ceramic materials due to its low concentration of Ca2+ ions, high concentration of HCO 3- ions and the necessity to maintain sterile environment during the test. © 2014 the Partner Organisations

Polyaniline based polymers in tissue engineering applications: a review

A number of electrically conducting polymers, such as polyaniline (PANi), as well as functionalized aniline copolymers and composites, which are simultaneously biodegradable and conductive, have been applied for developing electrically conductive scaffolds for tissue engineering (TE) in recent years. The rationale behind these scaffolds is to induce ‘electroactivity’ in scaffolds, as many research works have shown that an intrinsic electrical activity leads to both increased regeneration rates and improved healing of damaged tissues. PANi is the conductive polymer of choice because it is economical and easy to process with a variety of methods. The resultant PANi based biomaterials have shown biocompatibility, conductivity, suitable processability, positive cellular response, as well as an intrinsic antibacterial effect in numerous research studies. The analysis of the literature has revealed that PANi based scaffolds have been investigated for TE applications including skin/wound healing, bone, cartilage, nerve/spinal cord, vascular, skeletal muscle repair and for the treatment of infertility. Although PANi based materials find widespread applications in other sectors, they are still far away from being commercially exploited as scaffolds for TE despite positive research results. This review aims to discuss and critically assess the current state of PANi based TE scaffolds for different applications. A future perspective for utilizing PANi based biomaterials for applications in TE is discussed, including recent considerations about potential cytotoxic effects

Engineering of Metabolic Pathways by Artificial Enzyme Channels.

Application of industrial enzymes for production of valuable chemical compounds has greatly benefited from recent developments in Systems and Synthetic Biology. Both, in vivo and in vitro systems have been established, allowing conversion of simple into complex compounds. Metabolic engineering in living cells needs to be balanced which is achieved by controlling gene expression levels, translation, scaffolding, compartmentation, and flux control. In vitro applications are often hampered by limited protein stability/half-life and insufficient rates of substrate conversion. To improve stability and catalytic activity, proteins are post-translationally modified and arranged in artificial metabolic channels. Within the review article, we will first discuss the supramolecular organization of enzymes in living systems and second summarize current and future approaches to design artificial metabolic channels by additive manufacturing for the efficient production of desired products

Processing of porous glass ceramics from highly crystallisable industrial wastes

This study was carried out to gain understanding about the sintering behaviour of highly crystallisable industrial waste derived silicate mixtures under direct heating and rapid cooling conditions. The materials used in this study were plasma vitrified air pollution control waste and rejected pharmaceutical borosilicate glass. Powder compacts sintered under direct heating conditions were highly porous; compacts with particle size <38 μm reached a maximum density of 2.74 g cm-3 at 850°C, whereas compacts with particles of size <100 and <250 mm reached maximum densities of 2.69 and 2.72 g cm-3 at 875 and 900°C respectively. Further increase in sintering temperature resulted in a rapid decrease in density of the glass ceramics. Image analysis results were used to link the sudden drop in density to the increase in volume of microsized pores formed in the samples during sintering. In particular, compacts made from ,38 mm particles sintered at 9508C resulted in 65 vol.-% porosity with a pore size of <20 μm. Such materials can be used for sound and thermal insulation purposes

Protein Engineering of the Calb Lipase to Synthesize Fragrance Compounds

Abstract A computationally-guided semi-rational protein design approach was used to improve the enzymatic selectivity and catalytic efficiency of Pseudozyma antarctica lipase B (CalB) to synthesize methyl salicylate and methyl cinnamate. These fatty acid esters have significant relevance as flavoring and fragrance compounds in the biotechnological industry. Moreover, CalB is a highly active lipase that is widely used for the enzymatic hydrolysis and synthesis of esters, offering potential for the biological production of flavoring agents. However, the relatively confined organization of its active site precludes the recognition of bulky and aromatic substrates. To overcome this limitation, in silico docking analyses of CalB were undertaken to identify amino acid residues involved in precursor binding and recognition. These “hot spots” were subjected to combinatorial mutagenesis to yield three generations of CalB libraries per substrate. A surrogate substrate was used to screen for synthetic activity and evaluation of the new CalB variants revealed mutations giving rise to significant increase in synthetic activity relative to wild-type CalB. Ultimately, the best CalB variant could serve as a template to develop an E. coli whole-cell biocatalyst suitable for industrial enzymatic synthesis of methyl salicylate.</p

Mechanical properties and drug release behavior of PCL/zein coated 45S5 bioactive glass scaffolds for bone tissue engineering application.

This article presents data related to the research article entitled "The effect of coating type on mechanical properties and controlled drug release of PCL/zein coated 45S5 bioactive glass scaffolds for bone tissue engineering" [1]. We provide data on mechanical properties, in vitro bioactivity and drug release of bioactive glass (BG) scaffolds coated by poly (ε-caprolactone) (PCL) and zein used as a controlled release device for tetracycline hydrochloride (TCH). By coating the BG scaffolds with PCL or PCL/zein blend the mechanical properties of the scaffolds were substantially improved, i.e., the compressive strength increased from 0.004±0.001 MPa (uncoated BG scaffolds) to 0.15±0.02 MPa (PCL/zein coated BG scaffolds). A dense bone-like apatite layer formed on the surface of PCL/zein coated scaffolds immersed for 14 days in simulated body fluid (SBF). The data describe control of drug release and in vitro degradation behavior of coating by engineering the concentration of zein. Thus, the developed scaffolds exhibit attractive properties for application in bone tissue engineering research