Synthese neuer zwitterionischer Methacrylate und deren Anwendungen in oberflächeninitiierten Polymerisationen

Ziel dieser Arbeit war die Herstellung von Oberflächen mit zwitterionischen Polymerbeschichtungen, welche Anwendung als Substrate zur Stammzell-Kultivierung finden könnten. Der erste Teil der Arbeit beschreibt zunächst die Synthese einer Substanzbibliothek teilweise neuer zwitterionischer Methacrylate. Im zweiten Teil werden verschiedene Techniken der oberflächeninitiierten, kontrolliert-radikalischen Polymerisation (RAFT, ATRP) der Monomere auf CVD-modifizierten Oberflächen behandelt

Potential of electrospun cationic BSA fibers to guide osteogenic MSC differentiation via surface charge and fibrous topography

Large or complex bone fractures often need clinical treatments for sufficient bone repair. New treatment strategies have pursued the idea of using mesenchymal stromal cells (MSCs) in combination with osteoinductive materials to guide differentiation of MSCs into bone cells ensuring complete bone regeneration. To overcome the challenge of developing such materials, fundamental studies are needed to analyze and understand the MSC behavior on modified surfaces of applicable materials for bone healing. For this purpose, we developed a fibrous scaffold resembling the bone/bone marrow extracellular matrix (ECM) based on protein without addition of synthetic polymers. With this biomimetic in vitro model we identified the fibrous structure as well as the charge of the material to be responsible for its effects on MSC differentiation. Positive charge was introduced via cationization that additionally supported the stability of the scaffold in cell culture, and acted as nucleation point for mineralization during osteogenesis. Furthermore, we revealed enhanced focal adhesion formation and osteogenic differentiation of MSCs cultured on positively charged protein fibers. This pure protein-based and chemically modifiable, fibrous ECM model allows the investigation of MSC behavior on biomimetic materials to unfold new vistas how to direct cells’ differentiation for the development of new bone regenerating strategies

Nanostructured Bifunctional Hydrogels as Potential Instructing Platform for Hematopoietic Stem Cell Differentiation

Hematopoietic stem cells (HSCs) are blood forming cells which possess the ability to differentiate into all types of blood cells. T cells are one important cell type HSCs can differentiate into, via corresponding progenitor cells. T cells are part of the adaptive immune system as they mediate cellular immune responses. Due to this crucial function, in vitro differentiated T cells are the subject of current studies in the biomedical field in terms of cell transplantation. Studies show that the density of the immobilized Notch ligand Delta-like 1 (DLL1) presented in HSCs' environment can stimulate their differentiation toward T cells. The development of reliable synthetic cell culture systems presenting variable densities of DLL1 is promising for the future expansion of T cells' clinical applications. Here we introduce bifunctional polyethylene glycol-based (PEG-based) hydrogels as a potential instructing platform for the differentiation of human hematopoietic stem and progenitor cells (HSPCs) to T cells. PEG hydrogels bearing the cell adhesion supporting motif RGD (arginyl-glycyl-aspartic acid) were synthesized by UV-light induced radical copolymerization of PEG diacrylate and RGD modified PEG acrylate. The hydrogels were furthermore nanostructured by incorporation of gold nanoparticle arrays that were produced by block copolymer micelle nanolithography (BCML). BCML allows for the decoration of surfaces with gold nanoparticles in a hexagonal manner with well-defined interparticle distances. To determine the impact of DLL1 density on the cell differentiation, hydrogels with particle distances of ~40 and 90 nm were synthesized and the gold nanoparticles were functionalized with DLL1. After 27 days in culture, HSPCs showed an unphysiological differentiation status and, therefore, the differentiation was evaluated as atypical T lymphoid differentiation. Cluster of differentiation (CD) 4 was the only tested T cell marker which was expressed clearly in all samples. Thus, although the applied nanopatterned hydrogels affected two important signaling pathways (integrins and Notch) for T cell differentiation, it appears that more functionalities that control T cell differentiation in nature need to be considered for achieving fully synthetic in vitro T cell differentiation strategies

Carbohydrate‐Based Polymer Brushes Prevent Viral Adsorption on Electrostatically Heterogeneous Interfaces

Chemical heterogeneity on biomaterial surfaces can transform its interfacial properties, rendering nanoscale heterogeneity profoundly consequential during bioadhesion. To examine the role played by chemical heterogeneity in the adsorption of viruses on synthetic surfaces, a range of novel coatings is developed wherein a tunable mixture of electrostatic tethers for viral binding, and carbohydrate brushes, bearing pendant α‐mannose, β‐galactose, or β‐glucose groups, is incorporated. The effects of binding site density, brush composition, and brush architecture on viral adsorption, with the goal of formulating design specifications for virus‐resistant coatings are experimentally evaluated. It is concluded that virus‐coating interactions are shaped by the interplay between brush architecture and binding site density, after quantifying the adsorption of adenoviruses, influenza, and fibrinogen on a library of carbohydrate brushes co‐immobilized with different ratios of binding sites. These insights will be of utility in guiding the design of polymer coatings in realistic settings where they will be populated with defects.A tunable coating comprising nonfouling carbohydrate brushes and electrostatic binding sites for viruses is employed to study the relationship between surface design parameters and viral adsorption. Ultimately, brush architecture determines whether the binding sites are exposed to, or shielded from viruses. These insights will guide the design of polymer coatings that can resist viral binding despite being populated with defects.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147118/1/marc201800530-sup-0001-SuppMat.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147118/2/marc201800530_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147118/3/marc201800530.pd

Multifunctional nanoparticles for specific neuroblastoma targeting

Neuroblastoma is a solid extracranial cancer of the nervous system. Besides leukemia, brain tumors, and central nervous system tumors, neuroblastoma is the most common cancer in children.1 It mainly affects children under 15 years old and accounts for 15% of childhood cancer deaths.2 There is a wide variety of treatment options for neuroblastomas; ranging from surgery or chemotherapy in children with low-risk to medium-risk forms of the disease, to aggressive multimodal therapies in patients with high-risk forms.3 A treatment used in certain high-risk patients is iodine-131 meta-iodobenzylguanidine (I-131 MIBG) radiotherapy. MIBG is a norepinephrine analogue that localizes to adrenergic cells. Neuroblastoma cells overexpress adrenergic receptors, and thus take up MIBG at higher rates than other tissues.4 Because of this, when modified with I-131, MIBG is used as a radiotherapy agent.5 I-131 MIBG treatment, as a highly specific therapy, avoids many of the heavy side effects seen in other cancer treatments, but its radioactivity causes a need for highly specialized facilities. Additionally, all patients undergoing I-131 MIBG treatment must remain in isolation for several days while radiation in their system is reduced to safe levels, which is especially difficult for children. As an alternative to I-131 MIBG treatment, a nanoparticle (NP) system that uses MIBG to home to neuroblastoma cells and then releases chemotherapy agents in their immediate vicinity may result in a better treatment for the disease. It would be more patient friendly in that, in addition to the above stated advantages of MIBG, it would contain no radioactive properties and therefore avoid the need for patient isolation and specialized facilities, which would increase patient compliance and reduce costs. Similar NPs were previously shown to be useful for drug loading purposes and therapeutic release rates can be controlled in NP systems, as opposed to the traditional therapy.6 Through electrohydrodynamic (EHD) co-jetting, our group has fabricated surface modifiable, biodegradable nanoparticles that can be used for predictable, controlled, and distinct delivery of therapeutics.7 In this work we present the fabrication poly-lactic-glycolic acid NPs chemically modified to display MIBG on their surface that were manufactured using our EDH methodology. We characterized the system using proton nuclear magnetic resonance, scanning electron microscopy, dynamic light scattering, and nanoparticle tracking analysis. Increased particle uptake for MIBG modified NPs vs controls in a neuroblastoma line was observed using confocal microscopy and flow cytometry. Future work will investigate the efficacy of these particles for delivering chemotherapeutics in in-vitro and in-vivo systems based on previously published work on drug loading studies in our group.8 1. Pizzo, P. A. & Poplack, D. G. Principles and practice of pediatric oncology. (2006). 2. Stiller, C. A. & Parkin, D. M. International variations in the incidence of neuroblastoma. Int. J. Cancer 52, 538–543 (1992). 3. Park, J. R., Eggert, A. & Caron, H. Neuroblastoma: Biology, Prognosis, and Treatment. Hematol. Oncol. Clin. North Am. 24, 65–86 (2010). 4. Hattner, R. S., Huberty, J. P., Engelstad, B. L. & Gooding, C. A. Localization of m-lodo (I-131) benzylguanidine Neuroblastoma. 373–374 (1984). 5. Riad, R. et al. Role of 131-I MIBG Therapy in the Treatment of Advanced Neuroblastoma. J. Egypt. Natl. Canc. Inst. 21, 51–8 (2009). 6. Rahmani, S., Park, T. H., Dishman, A. F. & Lahann, J. Multimodal delivery of irinotecan from microparticles with two distinct compartments. J. Control. Release 172, 239–245 (2013). 7. Rahmani, S. & Lahann, J. Recent progress with multicompartmental nanoparticles. MRS Bull. 39, 251–257 (2014). 8. Rahmani, S. et al. Dual Release Carriers for Cochlear Delivery. Adv. Healthc. Mater. 5, 94–100 (2016)

Backbone‐Degradable Polymers Prepared by Chemical Vapor Deposition

Polymers prepared by chemical vapor deposition (CVD) polymerization have found broad acceptance in research and industrial applications. However, their intrinsic lack of degradability has limited wider applicability in many areas, such as biomedical devices or regenerative medicine. Herein, we demonstrate, for the first time, a backbone‐degradable polymer directly synthesized via CVD. The CVD co‐polymerization of [2.2]para‐cyclophanes with cyclic ketene acetals, specifically 5,6‐benzo‐2‐methylene‐1,3‐dioxepane (BMDO), results in well‐defined, hydrolytically degradable polymers, as confirmed by FTIR spectroscopy and ellipsometry. The degradation kinetics are dependent on the ratio of ketene acetals to [2.2]para‐cyclophanes as well as the hydrophobicity of the films. These coatings address an unmet need in the biomedical polymer field, as they provide access to a wide range of reactive polymer coatings that combine interfacial multifunctionality with degradability.Verletzliches Rückgrat: Beschichtungen aus Polymeren mit abbaubarem Rückgrat wurden durch Copolymerisation mittels chemischer Dampfabscheidung erhalten. Die Beschichtungen vereinen die Möglichkeit zur mehrfachen Funktionalisierung von Grenzflächen mit einer Abbaufähigkeit, was insbesondere für biomedizinische Anwendungen von Interesse ist.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135566/1/ange201609307-sup-0001-misc_information.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135566/2/ange201609307_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135566/3/ange201609307.pd

Nanostructured Bifunctional Hydrogels as Potential Instructing Platform for Hematopoietic Stem Cell Differentiation

Hematopoietic stem cells (HSCs) are blood forming cells which possess the ability to differentiate into all types of blood cells. T cells are one important cell type HSCs can differentiate into, via corresponding progenitor cells. T cells are part of the adaptive immune system as they mediate cellular immune responses. Due to this crucial function, in vitro differentiated T cells are the subject of current studies in the biomedical field in terms of cell transplantation. Studies show that the density of the immobilized Notch ligand Delta-like 1 (DLL1) presented in HSCs' environment can stimulate their differentiation toward T cells. The development of reliable synthetic cell culture systems presenting variable densities of DLL1 is promising for the future expansion of T cells' clinical applications. Here we introduce bifunctional polyethylene glycol-based (PEG-based) hydrogels as a potential instructing platform for the differentiation of human hematopoietic stem and progenitor cells (HSPCs) to T cells. PEG hydrogels bearing the cell adhesion supporting motif RGD (arginyl-glycyl-aspartic acid) were synthesized by UV-light induced radical copolymerization of PEG diacrylate and RGD modified PEG acrylate. The hydrogels were furthermore nanostructured by incorporation of gold nanoparticle arrays that were produced by block copolymer micelle nanolithography (BCML). BCML allows for the decoration of surfaces with gold nanoparticles in a hexagonal manner with well-defined interparticle distances. To determine the impact of DLL1 density on the cell differentiation, hydrogels with particle distances of ~40 and 90 nm were synthesized and the gold nanoparticles were functionalized with DLL1. After 27 days in culture, HSPCs showed an unphysiological differentiation status and, therefore, the differentiation was evaluated as atypical T lymphoid differentiation. Cluster of differentiation (CD) 4 was the only tested T cell marker which was expressed clearly in all samples. Thus, although the applied nanopatterned hydrogels affected two important signaling pathways (integrins and Notch) for T cell differentiation, it appears that more functionalities that control T cell differentiation in nature need to be considered for achieving fully synthetic in vitro T cell differentiation strategies

Bioinstructive Coatings for Hematopoietic Stem Cell Expansion Based on Chemical Vapor Deposition Copolymerization

We report the chemical vapor deposition (CVD) of dual-functional polymer films for the specific and orthogonal immobilization of two biomolecules (notch ligand delta-like 1 (DLL1) and an RGD-peptide) that govern the fate of hematopoietic stem and progenitor cells. The composition of the CVD polymer and thus the biomolecule ratio can be tailored to investigate and optimize the influence of the relative surface concentrations of biomolecules on stem cell behavior. Prior to cell experiments, all surfaces were characterized by infrared reflection adsorption spectroscopy, time-of-flight secondary ion mass spectrometry, and X-ray photoelectron spectroscopy to confirm the presence of both biomolecules. In a proof-of-principle stem cell culture study, we show that all polymer surfaces are cytocompatible and that the proliferation of the hematopoietic stem and progenitor cells is predominantly influenced by the surface concentration of immobilized DLL1

Surface-initiated RAFT polymerization from vapor-based polymer coatings

Surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization was used to synthesize poly(methyl methacrylate) (PMMA) and poly[2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammoniumhydroxide (PMEDSAH) brushes grafted from reactive poly[p-xylylene] surfaces. The synthetic approach involved functionalization of substrates via chemical vapor deposition polymerization of an electron-deficient alkynyl-functionalized [2.2]paracyclophane derivative. An azide-functionalized RAFT agent was anchored to the resulting poly[(p-xylylene-4-methyl propiolate)-co-p-xylylene] films via copper-free click-chemistry. Subsequent SI-RAFT polymerization yielded PMMA and PMEDSAH films with narrow dispersity which was further tuned by varying the concentration of a sacrificial RAFT agent in solution. Polymer dispersity was determined by size exclusion chromatography to be in the range of 1.2–1.4 for both polymers. This work provides a novel surface modification strategy to decorate a wide range of different substrates with polymer brushes, thereby eliminating the need for cumbersome modification protocols, which so far had to be established for each substrate material independently