Margit Schulze

Biomaterials and mesenchymal stem cells for regenerative medicine.

The reconstruction of hard and soft tissues is a major challenge in regenerative medicine, since diseases or traumas are causing increasing numbers of tissue defects due to the aging of the population. Modern tissue engineering is increasingly using three-dimensional structured biomaterials in combination with stem cells as cell source, since mature cells are often not available in sufficient amounts or quality. Biomaterial scaffolds are developed that not only serve as cell carriers providing mechanical support, but actively influence cellular responses including cell attachment and proliferation. Chemical modifications such as the incorporation of chemotactic factors or cell adhesion molecules are examined for their ability to enhance tissue development successfully. E.g. growth factors have been investigated extensively as substances able to support cell growth, differentiation and angiogenesis. Thus, continuously new patents and studies are published, which are investigating the advantages and disadvantages of different biomaterials or cell types for the regeneration of specific tissues. This review focuses on biomaterials, including natural and synthetic polymers, ceramics and corresponding composites used as scaffold materials to support cell proliferation and differentiation for hard and soft tissues regeneration. In addition, the local delivery of drugs by scaffold biomaterials is discussed.

Synthesis and spectroscopic properties of phthalocyanine dimers in solution

Abstract A soluble dimer of a tetra-(methoxy)-tetra-(octyloxy)-substituted silicon phthalocyanine has been prepared. Optical absorption spectra of the compound in solution showed a pronounced solvatochromism, characterized by a rather sharp peak with maximum at 640 nm in aromatic solvents and a broad absorption band consisting of up to five individual peaks for non-aromatic solutions such as THF or chloroform. Nanosecond transient absorption spectra exhibited a long-lived photoinduced absorption band at 520 nm which can be assigned to triplet absorption. Large quantum yields for intersystem crossing ranging between 30% and 40% were observed. These findings are compared to the results on the monomeric and polymeric compounds and discussed in the framework of exciton coupling.

Nucleophilic substitution in arylazo phenols : a simple route for preparing chlorosubstituted azobenzenes

Abstract The reaction of arylazo phenols 6–11 , arylazo resorcinols 20,25, and arylazo phloroglucinols 26 with POCl 3 in dimethylformamide yields chlorosubstituted arylazo benzenes 13–18 , 21, 23 , respectively, in moderate to high yields. Replacement of the OH-group by Cl is favoured by acceptor substituents in the aryl fragments ortho- and/or para-linked to the azo group. If arylazo compounds derived from resorcinol are used, the substitution reaction proceeds in a stepwise manner, giving rise to the formation of o-hydroxy-p-chlorosubstituted azo compounds 20 primarily and then of the dichlorosubstituted azo compounds 23 .

Artificial Scaffolds and Mesenchymal Stem Cells for Hard Tissues

Medicine was revolutionized in the last two centuries and its advances have more than doubled life expectancy. Nevertheless, some problems are as old as mankind and although the underlying causes might have changed, the problems themselves have not. Musculoskeletal disorders and tooth loss are such problems; they are the major reasons for the ever-growing need for bone replacement, which cannot always be realized by autologous material. New, multidisciplinary strategies are needed for the development of novel materials to meet the demand. Stem-cell-based approaches combined with newly designed scaffold materials seem to be promising tools for constructing tissue replacements. Human mesenchymal stem cells and their remarkable differentiation potential are an interesting cell source for the development of bio-engineered tissues. Scaffolds based on natural and synthetic materials with or without the use of bioactive molecules are constructed to mimic the natural environment. They can improve proliferation and differentiation of the scaffold-seeded cells. Combined, they can provide specific remedies for hard tissue replacement, which will be discussed in this chapter.

Stem Cells on Biomaterials for Synthetic Grafts to Promote Vascular Healing

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.

Novel method for the determination of average molecular weight of natural polymers based on 2D DOSY NMR and chemometrics: Example of heparin

Graphical abstract Figure. No caption available. HighlightsDOSY NMR spectroscopy was used for the determination of molecular weight of heparin and LMWH.PLS model using GPC reference data was developed and completely validated.The method was applicable to heparin and LMWH of different animal origin.The method can be used as a fast complementary measurement to standard NMR assay. ABSTRACT Apart from the characterization of impurities, the full characterization of heparin and low molecular weight heparin (LMWH) also requires the determination of average molecular weight, which is closely related to the pharmaceutical properties of anticoagulant drugs. To determine average molecular weight of these animal‐derived polymer products, partial least squares regression (PLS) was utilized for modelling of diffused‐ordered spectroscopy NMR data (DOSY) of a representative set of heparin (n = 32) and LMWH (n = 30) samples. The same sets of samples were measured by gel permeation chromatography (GPC) to obtain reference data. The application of PLS to the data led to calibration models with root mean square error of prediction of 498 Da and 179 Da for heparin and LMWH, respectively. The average coefficients of variation (CVs) did not exceed 2.1% excluding sample preparation (by successive measuring one solution, n = 5) and 2.5% including sample preparation (by preparing and analyzing separate samples, n = 5). An advantage of the method is that the sample after standard 1D NMR characterization can be used for the molecular weight determination without further manipulation. The accuracy of multivariate models is better than the previous results for other matrices employing internal standards. Therefore, DOSY experiment is recommended to be employed for the calculation of molecular weight of heparin products as a complementary measurement to standard 1D NMR quality control. The method can be easily transferred to other matrices as well.

Molecular Composites Based on Rigid Rod Polymers for Electrooptical Applications

Novel rigid rod polymers substituted with NLO-active chromophores have been developed towards application in electrooptical signal Modulation. The Materials are based on rigid polyesters and polyesteramids, in which the chromophores are either covalently linked to the backbone by short flexible spacers or directly incorporated into the main chain. In the bulk these systems form macroscopically ordered structures with layers of rigid rod backbones separated by the side chain segments. The properties and stability of the induced polar order can thus be adjusted by morphological parameters like the layer distance or the orientation of the main chains relative to the substrate. The relaxation of the NLO activity with time is described by a Multi-exponential decay and shows enhanced time-temperature stability even above 100°C. The temperature dependence of the relaxation times exhibits unusual features that distinguishes these systems from conventional NLO side chain polymers.

Qualitative and Quantitative Analysis of Lignins from Different Sources and Isolation Methods for an Application as a Biobased Chemical Resource and Polymeric Material

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.

Recent Patents on Biomedical Applications for the Treatment of Atherosclerosis

Atherosclerosis is a chronic disease of the arteries and accounts for about 50 percent of all deaths in industrial- ized 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. How- ever, 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 neces- sary 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 engi- neering incorporating stem cells or biomaterials to construct new vessels as substitutes for diseased veins and arteries.

Materials Engineering For Polarized Light Emitting Diodes

Electroluminescent devices have been made from organo-soluble derivatives of poly(pphenylene). Solubility and processibility by the LB-technique is achieved by attaching alkoxy side groups to the backbone-p-phenylene units. These polymers are of the hairy-rod (HR) type. If transferred as monolayers from the air-water-interface, monodomain multilayers with large order parameters of chain orientation are obtained. A 130 nm thick LB-film of poly(2,5-diisopentoxy-pphenylene) shows blue photoluminescence at λ max = 3.08 eV (404 nm) with a tail extending to 2 eV. The anisotropy was (l II - l 1 )/ (l 11 , + l 11 )= 0.5. This LB-film between a transparent gold and an evaporated Al-electrode shows polarized light emission at E ≤ 6.10 7 V cm −1 with am=a λ max 2.2 eV and an in-plane anisotropy of 0.54. Thin films obtained by spincoating of the same polymer show isotropic electroluminescence between ITO and Al-electrodes with an external quantum efficiency of about 0.03 %. Higher efficiencies up to 4 % were realized optimizing the device architecture and the electrodes. Photocrosslinkable sites are introduced as side groups to the poly(pphenylene) chain. This allows patterning of the LEDs. General features of the supramolecular architecture and typical defect structures occurring in films of polyconjugated macromolecules are discussed using prototypical polymers as examples. Important effects are chain segregation according to chain length and formation of disclinations.