Browsing by Subject "Biopolymers"

Now showing 1 - 4 of 4
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    Creating Structured Hydrogel Microenvironments for Regulating Stem Cell Differentiation
    (MDPI, 2020-12) Mills, David K.; Luo, Yangyang; Elumalai, Anusha; Esteve, Savannah; Karnik, Sonali; Yao, Shaomian; Mechanical and Energy Engineering, School of Engineering and Technology
    The development of distinct biomimetic microenvironments for regulating stem cell behavior and bioengineering human tissues and disease models requires a solid understanding of cell–substrate interactions, adhesion, and its role in directing cell behavior, and other physico-chemical cues that drive cell behavior. In the past decade, innovative developments in chemistry, materials science, microfabrication, and associated technologies have given us the ability to manipulate the stem cell microenvironment with greater precision and, further, to monitor effector impacts on stem cells, both spatially and temporally. The influence of biomaterials and the 3D microenvironment’s physical and biochemical properties on mesenchymal stem cell proliferation, differentiation, and matrix production are the focus of this review chapter. Mechanisms and materials, principally hydrogel and hydrogel composites for bone and cartilage repair that create “cell-supportive” and “instructive” biomaterials, are emphasized. We begin by providing an overview of stem cells, their unique properties, and their challenges in regenerative medicine. An overview of current fabrication strategies for creating instructive substrates is then reviewed with a focused discussion of selected fabrication methods with an emphasis on bioprinting as a critical tool in creating novel stem cell-based biomaterials. We conclude with a critical assessment of the current state of the field and offer our view on the promises and potential pitfalls of the approaches discussed.
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    Quantitation of Trastuzumab and an Antibody to SARS-CoV-2 in Minutes Using Affinity Membranes in 96-Well Plates
    (American Chemical Society, 2022) Tan, Hui Yin; Yang, Junyan; Linnes, Jacqueline C.; Welch, Christopher J.; Bruening, Merlin L.; Chemistry and Chemical Biology, School of Science
    Quantitation of therapeutic monoclonal antibodies (mAbs) in human serum could ensure that patients have adequate levels of mAbs for effective treatment. This research describes the use of affinity, glass-fiber membranes in a 96-well-plate format for rapid (<5 min) quantitation of the therapeutic mAb trastuzumab and a mAb against the SARS-CoV-2 spike protein. Adsorption of a poly(acrylic acid)-containing film in membrane pores and activation of the -COOH groups in the film enable covalent-linking of affinity peptides or proteins to the membrane. Passage of mAb-containing serum through the affinity membrane results in mAb capture within 1 min. Subsequent rinsing, binding of a secondary antibody conjugated to a fluorophore, and a second rinse yield mAb-concentration-dependent fluorescence intensities in the wells. Calibration curves established from analyses on different days have low variability and allow determination of mAb levels in separately prepared samples with an average error <10%, although errors in single-replicate measurements may reach 40%. The assays can occur in diluted serum with physiologically relevant mAb concentrations, as well as in undiluted serum. Thus, the combination of 96-well plates containing affinity membranes, a microplate reader, and a simple vacuum manifold affords convenient mAb quantitation in <5 min.
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    Regulating Lipid Organization and Investigating Membrane Protein Properties in Physisorbed Polymer-tethered Membranes
    (2012-08-07) Siegel, Amanda P.; Naumann, Christoph A.; Minto, Robert; Thompson, David H. Pai; Ritchie, Kenneth
    Cell membranes have remarkable properties both at the microscopic level and the molecular level. The current research describes the use of physisorbed polymer-grafted lipids in model membranes to investigate some of these properties on both of these length scales. On the microscopic scale, plasma membranes can be thought of as heterogenous thin films. Cell membranes adhered to elastic substrates are capable of sensing substrate/film mismatches and modulating their membrane stiffness to more closely match the substrate. Membrane/substrate mismatch can be modeled by constructing lipopolymer-enriched lipid monolayers with different bending stiffnesses and physisorbing them to rigid substrates which causes buckling. This report describes the use of atomic force microscopy and epimicroscopy to characterize these buckled structures and to illustrate the use of the buckled structures as diffusion barriers in lipid bilayers. In addition, a series of monolayers with varying bending stiffnesses and thicknesses are constructed on rigid substrates to analyze changes in buckling patterns and relate the experimental results to thin film buckling theory. On the molecular scale, plasma membranes can also be thought of as heterogeneous mixtures of lipids where the specific lipid environment is a crucial factor affecting membrane protein function. Unfortunately, heterogeneities involving cholesterol, labeled lipid rafts, are small and transient in live cells. To address this difficulty, the present work describes a model platform based on polymer-supported lipid bilayers containing stable raft-mimicking domains into which transmembrane proteins are incorporated (αvβ3, and α5β1integrins). This flexible platform enables the use of confocal fluorescence fluctuation spectroscopy to quantitatively probe the effect of cholesterol concentrations and the binding of native ligands (vitronectin and fibronectin for αvβ3, and α5β1) on protein oligomerization state and on domain-specific protein sequestration. In particular, the report shows significant ligand-induced integrin sequestration with a low level of dimerization. Cholesterol concentration increases rate of dimerization, but only moderately. Ligand addition does not affect rate of dimerization in either system. The combined results strongly suggest that ligands induce changes to integrin conformation and/or dynamics without inducing changes in integrin oligomerization state, and in fact these ligand-induce conformational changes impact protein-lipid interactions.
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    Synthesis and Structural Characterization of 2′-Deoxy-2′-fluoro-l-uridine Nucleic Acids
    (ACS, 2021-06) Dantsu, Yuliya; Zhang, Ying; Zhang, Wen; Biochemistry and Molecular Biology, School of Medicine
    Despite the development of artificial l-RNA/DNA as therapeutic molecules, the in-depth investigation on their chemical modifications is still limited. Here, we synthesize a chemically derivatized 2′-deoxy-2′-fluoro-l-uridine building block and incorporate it into oligonucleotides. Our thermo-denaturization and enzymatic digestion experiments reveal their superior stability. Furthermore, one crystal structure of l-type fluoro-DNA is determined to characterize its handedness. Our results reveal the increase of l-helix stability by fluoro-modification and provide the foundation for its future functional application.