Scholarly Works, Macromolecules Innovation Institute (MII)
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Browsing Scholarly Works, Macromolecules Innovation Institute (MII) by Department "Sustainable Biomaterials"
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- Bioactive Cellulose Nanocrystal-Poly(epsilon-Caprolactone) Nanocomposites for Bone Tissue Engineering ApplicationsHong, Jung Ki; Cooke, Shelley L.; Whittington, Abby R.; Roman, Maren (2021-02-25)3D-printed bone scaffolds hold great promise for the individualized treatment of critical-size bone defects. Among the resorbable polymers available for use as 3D-printable scaffold materials, poly(epsilon-caprolactone) (PCL) has many benefits. However, its relatively low stiffness and lack of bioactivity limit its use in load-bearing bone scaffolds. This study tests the hypothesis that surface-oxidized cellulose nanocrystals (SO-CNCs), decorated with carboxyl groups, can act as multi-functional scaffold additives that (1) improve the mechanical properties of PCL and (2) induce biomineral formation upon PCL resorption. To this end, an in vitro biomineralization study was performed to assess the ability of SO-CNCs to induce the formation of calcium phosphate minerals. In addition, PCL nanocomposites containing different amounts of SO-CNCs (1, 2, 3, 5, and 10 wt%) were prepared using melt compounding extrusion and characterized in terms of Young's modulus, ultimate tensile strength, crystallinity, thermal transitions, and water contact angle. Neither sulfuric acid-hydrolyzed CNCs (SH-CNCs) nor SO-CNCs were toxic to MC3T3 preosteoblasts during a 24 h exposure at concentrations ranging from 0.25 to 3.0 mg/mL. SO-CNCs were more effective at inducing mineral formation than SH-CNCs in simulated body fluid (1x). An SO-CNC content of 10 wt% in the PCL matrix caused a more than 2-fold increase in Young's modulus (stiffness) and a more than 60% increase in ultimate tensile strength. The matrix glass transition and melting temperatures were not affected by the SO-CNCs but the crystallization temperature increased by about 5.5 degrees C upon addition of 10 wt% SO-CNCs, the matrix crystallinity decreased from about 43 to about 40%, and the water contact angle decreased from 87 to 82.6 degrees. The abilities of SO-CNCs to induce calcium phosphate mineral formation and increase the Young's modulus of PCL render them attractive for applications as multi-functional nanoscale additives in PCL-based bone scaffolds.
- The effect of residual lignin on the rheological properties of cellulose nanofibril suspensionsIglesias, Maria C.; Shivyari, Niloofar; Norris, Ann; Martin-Sampedro, Raquel; Eugenio, M. E.; Lahtinen, Panu; Auad, Maria L.; Elder, Thomas; Jiang, Zhihua; Frazier, Charles E.; Peresin, Maria S. (2020-10-10)Although the removal of lignin and hemicelluloses from cellulose pulp to produce fully bleached cellulose nanofibrils (B-CNF) is the most common practice, the presence of residual lignin and hemicelluloses in raw materials for the production of lignin containing cellulose nanofibrils (LCNFs) holds several advantages. In this work, we investigated the effect of residual lignin inEucalyptus globuluscellulose fibers on the properties of the resulting LCNFs. The stability of the colloidal suspensions was assessed by zeta-potential values and charge density analyses. Morphology of the CNFs was studied using scanning electron microscopy and atomic force microscopy. Fibril diameter and diameter distributions for CNFs with different levels of residual lignin showed a decrease on fiber diameter as the lignin content increases. Differences in the chemical composition of the CNFs was evidenced as indicated in the Fourier-transform infrared spectroscopy spectra, particularly in fingerprint region. Thermal behavior of the CNFs was not altered by the presence of lignin, as indicated by thermogravimetric analysis. Finally, the rheological behavior of the samples was evaluated observing a gel-like behavior as well as an increase of the viscosity in LCNFs with higher lignin contents.
- Folic Acid-Conjugated Cellulose Nanocrystals Show High Folate-Receptor Binding Affinity and Uptake by KB and Breast Cancer CellsBittleman, Katelyn Rose; Dong, Shuping; Roman, Maren; Lee, Yong Woo (American Chemical Society, 2018-10-24)The study evaluates cellulose nanocrystals (CNCs) as nanocarriers for targeted, intracellular delivery of molecular agents. CNCs were labeled with fluorescein-5′-isothiocyanate as an imaging agent and conjugated to folic acid (FA) as a targeting ligand. The CNC conjugates were characterized by UV–vis spectroscopy, ζ-potential analysis, dynamic light scattering, and atomic force microscopy. Cellular binding/uptake of the FA-conjugated CNCs by KB and MDA-MB-468 cells was quantified with cellular uptake assays. Internalization of the particles was confirmed by confocal microscopy. Uptake mechanisms were determined by inhibition studies with chlorpromazine and genistein. Binding affinity was qualitatively assessed with a free folate inhibition assay. Both KB and MDA-MB-468 cells exhibited significant and folate-receptor specific binding/uptake of FA-conjugated CNCs. Clathrin-mediated endocytosis was a significant uptake mechanism in both cell types, whereas caveolae-mediated endocytosis only played a significant role in MDA-MB-468 cells. Uptake inhibition of FA-conjugated CNCs by KB cells required high concentrations (>1 mM) of free FA. The observed FR-specific internalization of FA-conjugated CNCs by FR-positive cancer cells and tumors and their remarkable high affinity for the FR demonstrate the great potential of CNCs as novel nanocarriers for imaging agents and chemotherapeutics in the early detection and treatment of cancer.
- Imparting functional variety to cellulose ethers via olefin cross-metathesisDong, Yifan; Edgar, Kevin J. (The Royal Society of Chemistry, 2015-04-09)Olefin cross-metathesis is a valuable new approach for imparting functional variety to cellulose ethers. Starting from commercially available ethyl cellulose, terminally unsaturated alkyl groups were appended as metathesis handles by reaction with allyl chloride, 5-bromo-1-pentene, 7-bromo-1-heptene and 11-bromo-1-undecene, employing sodium hydride catalyst. These olefin-terminal ethyl cellulose derivatives were then subjected to olefin cross-metathesis with a variety of electron-poor olefin substrates, including acrylic acid and acrylate esters under optimized conditions (5–10 mol% Hoveyda-Grubbs’ 2nd generation catalyst, 37 °C, 2 h). The effects of varying the length of the ω-unsaturated alkyl handle, and of the solvent systems used were evaluated. Ethyl cellulose containing a pent-4-enyl substituent performed best in cross metathesis reactions and a hept-6-enyl substituent gave similarly good results. Ethyl cellulose with allyl substituents gave low to moderate metathesis conversion (<50%), possibly due to steric effects and the proximity of the ether oxygen to the terminal olefin. Interestingly, longer tethers (undec-10-enyl) gave high conversions (up to 90%) but relatively slow reactions (ca. 12 h needed for high conversion). While limited in this study by the relatively low DS (OH) of the starting commercial ethyl cellulose materials, this methodology has strong promise for introduction of diverse functionality to cellulose ethers in chemospecific and mild fashion, enabling amorphous solid dispersion and other applications.