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Nachhaltigkeitskonzepte sind kein selbstverständlicher Gegenstand der chemischen Hochschulausbildung. Der vorliegende Text fragt nach den Ursachen und zeigt anschließend Anschlussflächen für das Thema Nachhaltigkeit in der Chemieausbildung. Er stellt ein fachübergreifendes und zugleich fachbezogenes Konzept vor, welches Nachhaltigkeit zum Gegenstand für Chemiestudierende macht. Dieses ermöglicht den Studierenden einen subjektiv bedeutsamen Zugang zu den Fachinhalten. Es fördert Bewertungskompetenzen und Verantwortungsfähigkeit, schult die Sprachgewandtheit und erleichtert methodisch geführt die Reflexion auf Gegenstand und Selbstverständnis.
Atherosclerosis is a chronic disease of the arteries and accounts for about 50 percent of all deaths in industrialized countries. For its treatment, patients primarily need to undergo lifestyle changes, concerning their diet or sportive behavior, while additional pharmaceutical approaches help to reduce major risk factors such as hypertension and hyperlipidemia. However, these two areas of treatment are only briefly mentioned here. Instead, this article focuses on literature and patents from the last decade focusing on invasive surgical procedures necessary for treatment of diseased blood vessels in severe cases of atherosclerosis. Described herein are synthetic grafts and so-called autografts, which are harvested from the patient for bypass surgery. In addition, implantable stents are discussed, which deal with different atherosclerotic aspects, such as restenosis, re-endothelialization, neointimal hyperplasia and thrombosis. And finally, publications and inventions are presented from the relatively new field of artificial tissue engineering incorporating stem cells or biomaterials to construct new vessels as substitutes for diseased veins and arteries.
Lignins in general have been extensively studied, though the relation between source, isolation method and application is rarely described. In the present work, lignin from different sources (wheat straw and beech wood) and isolation methods (steam explosion, Organosolv) has been characterized regarding their application as a chemical resource and polymeric material. A range of analytical methods were applied including elemental analysis, FT-IR, 31P NMR, SEC, Py-GC-MS and HPLC to gain information about establish the purity, structure, molecular weight, thermal behavior and to determine carbohydrate residues according to the NREL protocol. TGA and DSC were used to study the thermal behavior of the isolated lignins and showed relatively low glass transition temperatures around 120 °C and decomposition temperatures between 340 and 380 °C. NREL analysis presented a carbohydrate-free lignin fraction derived from beech wood via Organosolv process which has not been achieved to date. The finding of this work supports Organolsolv as an efficient method to isolate pure lignin fractions from beech wood with practical value in industry, in particular for application in polyurethanes and phenolic resins.
Mesenchymal Stem Cells
(2020)
This chapter focuses on mesenchymal stem cells (MSCs), a multipotent stem cell type that has been found in a variety of tissues and organs of the human body since their discovery in 1970. Their main function is to maintain and repair the respective tissue in vivo. Mesenchymal stem cells can be easily isolated from different tissues and can undergo extensive self-proliferation prior to differentiation into various mesodermal cell types such as osteoblasts, chondrocytes, adipocytes, tenocytes, myocytes, and fibroblasts. Because of this vast differentiation potential, mesenchymal stem cells are a promising tool for regenerative medicine approaches. They could play an important role in cellular therapy, tissue replacement and regeneration in the future. Mesenchymal stem cells will be compared for their application and differentiation potential to embryonic stem cells and induced pluripotent stem cells and the limitations and challenges using scaffolds for tissue repair will be presented. In addition, legal and ethical aspects of the use of mesenchymal stem cells will be discussed. Moreover, isolation protocols for mesenchymal stem cells from the most common sources namely bone marrow, adipose tissue and umbilical cord are included.
Three-dimensional scaffolds are known to directly influence proliferation and differentiation of mesenchymal stem cells into bone tissue due to their properties such as stiffness and topography. While conventional methods for chemical induction of differentiation processes are based on incorporation of growth factors and/or cytokines via blending or adhesion onto the scaffold surfaces, novel approaches use template-mediated biomineralization to mimic the stimuli stem cells receive in their natural niche. This chapter summarizes recent progresses in guided bone tissue engineering with particular focus on design and functionality of three dimensional scaffolds, chemical templates and promising approaches for the corresponding cellbased approaches for future therapies.
The main objective of this chapter is to explore the lignocellulose feedstock (LCF) biorefinery for industrial usage according to green chemistry principles. In particular, the isolation and valorization of lignin as one of the most interesting intermediates of LCF biorefineries is discussed, including lignin isolation, purification, and structure analysis. Structure elucidation involves various chromatographic, spectroscopic, microscopic, and thermochemical methods. Thus, basic structure–property relationships regarding the influence of biomass source and isolation process on lignin amount, constitution, and 3D structure are highlighted. Furthermore, storage effects on lignin structure and degradation effects are presented. Finally, potential applications are discussed, including novel lignin-based hydrogels, composite compounds (hybrids), and nanomaterials. Focus is drawn to antioxidant and antimicrobial activity of lignin for applications in packaging and biomedicine, that is, biomaterials for drug release and tissue engineering.
Bone regeneration and replacement is a major focus in regenerative medicine since degenerative diseases and tumor surgery as well as accidents or dangerous recreational behavior is leading to an increasing need for bone reconstruction strategies. Especially for critical size bone defects, tissue engineering with mesenchymal stem cells is extensively studied because these cells are functioning as precursors for osteoblast in vivo. Nevertheless to reproduce the complex interaction of various factors in vitro is not an easy approach and further investigations have to be done. The status quo is summarized. A variety of growth and transcription factors are known to be involved in osteogenesis with bone morphogenetic proteins (BMPs) and the transcription factor Runx2 being the most extensively studied ones. But also PPAR γ and Osterix are generally regarded as the master regulators of osteoblast differentiation. Recently the large family of purinergic receptors has proven to be essential molecules in osteogenesis as well. In addition, scaffolding is needed to create a three-dimensional tissue. Recent developments in scaffold design are summarized, including natural and synthetic materials with or without the use of bioactive molecules constructed to mimic the natural environment. The status quo of scaffold fabrication methods such as 3D nanoprinting and their influence on cell-scaffold interactions is discussed. In this review we summarize the most interesting results and our related work focusing on two joined approaches: 1) the complex interaction of the most promising factors improving or accelerating osteogenic differentiation and ii) the development of scaffold materials with osteoconductive and osteoinductive properties.
Bone tissue engineering is an ever-changing, rapidly evolving, and highly interdisciplinary field of study, where scientists try to mimic natural bone structure as closely as possible in order to facilitate bone healing. New insights from cell biology, specifically from mesenchymal stem cell differentiation and signaling, lead to new approaches in bone regeneration. Novel scaffold and drug release materials based on polysaccharides gain increasing attention due to their wide availability and good biocompatibility to be used as hydrogels and/or hybrid components for drug release and tissue engineering. This article reviews the current state of the art, recent developments, and future perspectives in polysaccharide-based systems used for bone regeneration.
With increasing life expectancy, demands for dental tissue and whole-tooth regeneration are becoming more significant. Despite great progress in medicine, including regenerative therapies, the complex structure of dental tissues introduces several challenges to the field of regenerative dentistry. Interdisciplinary efforts from cellular biologists, material scientists, and clinical odontologists are being made to establish strategies and find the solutions for dental tissue regeneration and/or whole-tooth regeneration. In recent years, many significant discoveries were done regarding signaling pathways and factors shaping calcified tissue genesis, including those of tooth. Novel biocompatible scaffolds and polymer-based drug release systems are under development and may soon result in clinically applicable biomaterials with the potential to modulate signaling cascades involved in dental tissue genesis and regeneration. Approaches for whole-tooth regeneration utilizing adult stem cells, induced pluripotent stem cells, or tooth germ cells transplantation are emerging as promising alternatives to overcome existing in vitro tissue generation hurdles. In this interdisciplinary review, most recent advances in cellular signaling guiding dental tissue genesis, novel functionalized scaffolds and drug release material, various odontogenic cell sources, and methods for tooth regeneration are discussed thus providing a multi-faceted, up-to-date, and illustrative overview on the tooth regeneration matter, alongside hints for future directions in the challenging field of regenerative dentistry.
Renewable resources are gaining increasing interest as a source for environmentally benign biomaterials, such as drug encapsulation/release compounds, and scaffolds for tissue engineering in regenerative medicine. Being the second largest naturally abundant polymer, the interest in lignin valorization for biomedical utilization is rapidly growing. Depending on its resource and isolation procedure, lignin shows specific antioxidant and antimicrobial activity. Today, efforts in research and industry are directed toward lignin utilization as a renewable macromolecular building block for the preparation of polymeric drug encapsulation and scaffold materials. Within the last five years, remarkable progress has been made in isolation, functionalization and modification of lignin and lignin-derived compounds. However, the literature so far mainly focuses lignin-derived fuels, lubricants and resins. The purpose of this review is to summarize the current state of the art and to highlight the most important results in the field of lignin-based materials for potential use in biomedicine (reported in 2014⁻2018). Special focus is placed on lignin-derived nanomaterials for drug encapsulation and release as well as lignin hybrid materials used as scaffolds for guided bone regeneration in stem cell-based therapies.
This review is divided into two interconnected parts, namely a biological and a chemical one. The focus of the first part is on the biological background for constructing tissue-engineered vascular grafts to promote vascular healing. Various cell types, such as embryonic, mesenchymal and induced pluripotent stem cells, progenitor cells and endothelial- and smooth muscle cells will be discussed with respect to their specific markers. The in vitro and in vivo models and their potential to treat vascular diseases are also introduced. The chemical part focuses on strategies using either artificial or natural polymers for scaffold fabrication, including decellularized cardiovascular tissue. An overview will be given on scaffold fabrication including conventional methods and nanotechnologies. Special attention is given to 3D network formation via different chemical and physical cross-linking methods. In particular, electron beam treatment is introduced as a method to combine 3D network formation and surface modification. The review includes recently published scientific data and patents which have been registered within the last decade.
The antiradical and antimicrobial activity of lignin and lignin-based films are both of great interest for applications such as food packaging additives. The polyphenolic structure of lignin in addition to the presence of O-containing functional groups is potentially responsible for these activities. This study used DPPH assays to discuss the antiradical activity of HPMC/lignin and HPMC/lignin/chitosan films. The scavenging activity (SA) of both binary (HPMC/lignin) and ternary (HPMC/lignin/chitosan) systems was affected by the percentage of the added lignin: the 5% addition showed the highest activity and the 30% addition had the lowest. Both scavenging activity and antimicrobial activity are dependent on the biomass source showing the following trend: organosolv of softwood > kraft of softwood > organosolv of grass. Testing the antimicrobial activities of lignins and lignin-containing films showed high antimicrobial activities against Gram-positive and Gram-negative bacteria at 35 °C and at low temperatures (0-7 °C). Purification of kraft lignin has a negative effect on the antimicrobial activity while storage has positive effect. The lignin release in the produced films affected the activity positively and the chitosan addition enhances the activity even more for both Gram-positive and Gram-negative bacteria. Testing the films against spoilage bacteria that grow at low temperatures revealed the activity of the 30% addition on HPMC/L1 film against both B. thermosphacta and P. fluorescens while L5 was active only against B. thermosphacta. In HPMC/lignin/chitosan films, the 5% addition exhibited activity against both B. thermosphacta and P. fluorescens.
Antioxidant activity is an essential feature required for oxygen-sensitive merchandise and goods, such as food and corresponding packaging as well as materials used in cosmetics and biomedicine. For example, vanillin, one of the most prominent antioxidants, is fabricated from lignin, the second most abundant natural polymer in the world. Antioxidant potential is primarily related to the termination of oxidation propagation reactions through hydrogen transfer. The application of technical lignin as a natural antioxidant has not yet been implemented in the industrial sector, mainly due to the complex heterogeneous structure and polydispersity of lignin. Thus, current research focuses on various isolation and purification strategies to improve the compatibility of lignin material with substrates and enhancing its stabilizing effect.
Small Molecules Enhance Scaffold-Based Bone Grafts via Purinergic Receptor Signaling in Stem Cells
(2018)
The need for bone grafts is high, due to age-related diseases, such as tumor resections, but also accidents, risky sports, and military conflicts. The gold standard for bone grafting is the use of autografts from the iliac crest, but the limited amount of accessible material demands new sources of bone replacement. The use of mesenchymal stem cells or their descendant cells, namely osteoblast, the bone-building cells and endothelial cells for angiogenesis, combined with artificial scaffolds, is a new approach. Mesenchymal stem cells (MSCs) can be obtained from the patient themselves, or from donors, as they barely cause an immune response in the recipient. However, MSCs never fully differentiate in vitro which might lead to unwanted effects in vivo. Interestingly, purinergic receptors can positively influence the differentiation of both osteoblasts and endothelial cells, using specific artificial ligands. An overview is given on purinergic receptor signaling in the most-needed cell types involved in bone metabolism-namely osteoblasts, osteoclasts, and endothelial cells. Furthermore, different types of scaffolds and their production methods will be elucidated. Finally, recent patents on scaffold materials, as wells as purinergic receptor-influencing molecules which might impact bone grafting, are discussed.