| 1. |
- Abouhmad, Adel, et al.
(author)
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Immobilization to Positively Charged Cellulose Nanocrystals Enhances the Antibacterial Activity and Stability of Hen Egg White and T4 Lysozyme
- 2017
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 18:5, s. 1600-1608
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Journal article (peer-reviewed)abstract
- Antibacterial bionanostructures were produced from cellulose nanocrystals (CNC) with immobilized lysozyme from hen egg white (HEW) and T4 bacteriophage, respectively. The nanocrystals were prepared from microcrystalline cellulose by ammonium persulfate oxidation with a yield of 68% and having an average size of 250 nm and low polydispersity index. HEW lysozyme (HEWL) and T4 lysozyme (T4L) were immobilized to CNC by different mechanisms including adsorption and covalent coupling to carbodiimide-activated carboxylate groups and to glutaraldehyde-activated aminated CNC (Am-CNC), respectively. The effect of immobilization on the enzymatic activity (both lytic and hydrolytic) and antibacterial activity of the lysozymes was studied using different methods. Am-CNC-lysozyme conjugates retained the highest lytic activity, 86.3% and 78.3% for HEWL and T4L, respectively. They also showed enhanced bactericidal activity with high potency against Gram-positive as well as Gram-negative bacteria in a relatively shorter time as compared to the free enzymes and resulted in extensive cellular damage, as shown by transmission electron microscopy. The enhanced antibacterial activity was correlated with the increase in zeta potential of Am-CNC-lysozyme conjugates. The immobilized lysozyme preparations further exhibited enhanced storage stability at 4 and 22 °C.
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| 2. |
- Adamus, Grazyna, et al.
(author)
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MALDI-TOF MS Reveals the Molecular Level Structures of Different Hydrophilic-Hydrophobic Polyether-esters
- 2009
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 10:6, s. 1540-1546
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Journal article (peer-reviewed)abstract
- Multi- and triblock copolymers based on 1,5-dioxepan-2-one/epsilon-caprolactone (DXO/CL) were investigated by MALDI-TOF MS to determine the influence of copolymer composition and architecture on the molecular structures at the individual chain level. The copolymer compositions, average block lengths, and molecular weights were determined by H-1 and C-13 NMR and by SEC, respectively. The structures of polyether-ester oligomers (linear, cyclic) as well as the chemical structures of their end groups were established on the basis of their MALDI-TOF mass spectra. The mass spectrum of PDXO homopolymer was relatively simple, however, complex mass spectra were obtained in the case of multi- and triblock copolymers and the mass spectra clearly discerned the molecular level effect of copolymer composition and copolymer type.
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| 3. |
- Adden, R, et al.
(author)
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New approaches to the analysis of enzymatically hydrolyzed methyl cellulose. Part 1. Investigation of the influence of structural parameters on the extent of degradation
- 2006
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1526-4602 .- 1525-7797. ; 7:5, s. 1399-1409
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Journal article (peer-reviewed)abstract
- Six methyl celluloses (MCs), one with a degree of substitution (DS) of 1.32 and five with DS between 1.83 and 1.88, were thoroughly investigated. Monomer composition and methyl distribution in the polymer chain were analyzed after total or partial random hydrolysis and appropriate derivatization with gas chromatography ( GC) and mass spectrometry (MS), respectively, and used as reference data. The same MCs were then hydrolyzed with an enzyme preparation of Trichoderma longibrachiatum and further investigated with size-exclusion chromatography with multiangle light scattering and refractive index detection (SEC-MALS/RI) and MS. Electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) in combination with various MS analyzers were compared with respect to quantification of the degradation products directly and after perdeuteriomethylation. The methyl group distribution in the oligomeric fractions and the average DS as a function of chain length were calculated from ESI mass spectra. With help of the reference analysis, patterns could be corrected for the unspecific contribution of end groups. By labeling and ESI tandem MS, our knowledge about the tolerance of the enzymes' sub-sites with respect to the number of methyl groups could be improved.
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| 4. |
- Ainalem, Marie-Louise, et al.
(author)
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Dynamic light scattering and fluorescence study of the interaction between double-stranded DNA and poly(amido amine) dendrimers
- 2007
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1526-4602 .- 1525-7797. ; 8:5, s. 1557-1563
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Journal article (peer-reviewed)abstract
- The interaction between a cationic poly(amido amine) (PAMAM) dendrimer of generation 4 and double-stranded salmon sperm DNA in 10 mM NaBr solution has been investigated using dynamic light scattering (DLS) and steady-state fluorescence spectroscopy. The structural parameters of the formed aggregates as well as the complex formation process were studied in dilute solutions. When DNA is mixed with PAMAM dendrimers, it undergoes a transition from a semiflexible coil to a more compact conformation due to the electrostatic interaction present between the cationic dendrimer and the anionic polyelectrolyte. The DLS results reveal that one salmon sperm DNA molecule forms a discrete aggregate in dilute solution with several PAMAM dendrimers with a mean apparent hydrodynamic radius of 50 nm. These discrete complexes coexist with free DNA at low molar ratios of dendrimer to DNA, which shows that cooperativity is present in the complex formation. The formation of the complexes was confirmed by agarose gel electrophoresis measurements. DNA in the complexes was also found to be significantly more protected against DNase catalyzed digestion compared to free DNA. The number of dendrimers per DNA chain in the complexes was found to be approximately 35 as determined by steady-state fluorescence spectroscopy.
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| 5. |
- Albertsson, Ann-Christine
(author)
-
Celebrating 20 years of Biomacromolecules!
- 2019
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 20:2, s. 767-768
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Journal article (peer-reviewed)
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| 6. |
- Albertsson, Ann-Christine, et al.
(author)
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Design of renewable hydrogel release systems from fiberboard mill wastewater
- 2010
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 11:5, s. 1406-1411
-
Journal article (peer-reviewed)abstract
- A new route for the design of renewable hydrogels is presented. The soluble waste from masonite production was isolated, fractionized, and upgraded. The resulting hemicellulose rich fraction was alkenyl-functionalized and used in the preparation of covalently cross-linked hydrogels capable of sustained release of incorporated agents. Said hydrogels showed a Fickian diffusion-based release of incorporated bovine serum albumin. Also, a method for the coating of seeds with hydrogel was developed. The sustained release of incorporated growth retardant agents from the hydrogel coating on rape seeds was shown to enable the temporary inhibition of germination.
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| 7. |
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| 8. |
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| 9. |
- Albertsson, Ann-Christine, et al.
(author)
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Recent developments in ring opening polymerization of lactones for biomedical applications
- 2003
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 4:6, s. 1466-1486
-
Research review (peer-reviewed)abstract
- Aliphatic polyesters prepared by ring-opening polymerization of lactones are now used worldwide as bioresorbabale devices in surgery (orthopaedic devices, sutures, stents, tissue engineering, and adhesion barriers) and in pharmacology (control drug delivery). This review presents the various methods of the synthesis of polyesters and tailoring the properties by proper control of molecular weight, composition, and architecture so as to meet the stringent requirements of devices in the medical field. The effect of structure on properties and degradation has been discussed. The applications of these polymers in the biomedical field are described in detail.
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| 10. |
- An, Junxue, et al.
(author)
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Comparison of a Brush-with-Anchor and a Train-of-Brushes Mucin on Poly(methyl methacrylate) Surfaces : Adsorption, Surface Forces, and Friction
- 2014
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 15:4, s. 1515-1525
-
Journal article (peer-reviewed)abstract
- Interfacial properties of two types of mucins have been investigated at the aqueous solution/poly(methyl methacrylate) (PMMA) interface. One is commercially available bovine submaxillary mucin, BSM, which consists of alternating glycosylated and nonglycosylated regions. The other one is a recombinant mucin-type fusion protein, PSGL-1/mIgG(2b), consisting of a glycosylated mucin part fused to the Fc part of an immunoglobulin. PSGL-1/mIgG(2b) is mainly expressed as a (timer upon production. A quartz crystal microbalance with dissipation was used to study the adsorption of the mucins to PMMA surfaces. The mass of the adsorbed mucin layers, including the adsorbed mucin and water trapped in the layer, was found to be significantly higher for PSGL-1/mIgG(2b) than for BSM. Atomic force microscopy with colloidal probe was employed to study interactions and frictional forces between mucin-coated PMMA surfaces. Purely repulsive forces of steric origin were Observed between PSGL-1/mIgG(2b) mucin layers, whereas a small adhesion was detected between BSM layers and attributed to bridging. Both mucin layers reduced the friction force between PMMA surfaces in aqueous solution. The reduction was, however, significantly more pronounced for PSGL-1/mIgG(2b). The effective friction coefficient between PSGL-1/mIgG(2b)-coated PMMA surfaces is as low as 0.02 at low loads, increasing to 0.24 at the highest load explored, 50 nN. In contrast, a friction coefficient of around 0.7 was obtained between BSM-coated PMMA surfaces. The large differences in interfacial properties for the two mucins are discussed in relation to their structural differences.
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| 11. |
- Andersson, Alexandra, et al.
(author)
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Protein release from galactoglucomannan hydrogels : Influence of substitutions and enzymatic hydrolysis by beta-mannanase
- 2008
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 9:8, s. 2104-2110
-
Journal article (peer-reviewed)abstract
- O-Acetyl-galactoglucomannan (AcGGM) is the major soft-wood hemicellulose. Structurally modified AcGGM and hydrogels of AcGGM were prepared. The degree of substitution (DS) of AcGGM was modified enzymatically with beta-galactosidase, and chemically with an acrylate derivative, 2-hydroxyethylmethacrylate (HEMA). The hydrolysis of AcGGM with beta-mannanase was shown to increase with decreasing DS. AcGGM hydrogels were prepared from chemically modified AcGGM with varying DS of HEMA. Bovine serum albumin (BSA) was encapsulated in hydrogels. A spontaneous burst release of BSA was decreased with increased DS of HEMA. The addition of beta-mannanase significantly enhanced the BSA release from hydrogels with a DS of 0.36, reaching a maximum of 95% released BSA after eight hours compared to 60% without enzyme. Thus, both the pendant group composition and the enzyme action are valuable tools in the tailoring of hydrogel release profiles of potential interest for intestine drug delivery.
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| 12. |
- Andersson, Marlene, et al.
(author)
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Morphology and Composition of the Spider Major Ampullate Gland and Dragline Silk
- 2013
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 14, s. 2945-2952
-
Journal article (peer-reviewed)abstract
- Spider silk is made of unique proteins-spidroins-secreted and stored as a protein solution (dope) in specialized glands. The major ampullate gland, source of the dragline silk, is composed of a tail, a sac and an elongated duct. For this gland, several different types of epithelial cells and granules have been described, but it is largely unknown how they correlate with spidroin production. It is also not settled what parts of the large spidroins end up in the final silk, and it has been suggested that the N-terminal domain (NT) is lacking. Here we show that NT is present in the dope and throughout drag,line silk fibers, including the skin layer, and that the major ampullate tail and sac consist of three different and sharply demarcated zones (A-C), each with a distinct epithelial cell type. Finally, we show that spidroins are produced in the A and B zone epithelia, while the C zone granules lack spidroins.
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| 13. |
- Andersson, M., et al.
(author)
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Size and structure characterization of ethylhydroxyethyl cellulose by the combination of field-flow fractionation with other techniques. Investigation of ultralarge components
- 2004
-
In: Biomacromolecules. - : Wiley. - 1525-7797 .- 1526-4602. ; 5:1, s. 97-105
-
Journal article (peer-reviewed)abstract
- Ethylhydroxyethyl cellulose (EHEC) of three different viscosity classes (EHEC I, II, and III) was analyzed by programmed cross-flow asymmetrical flow field-flow fractionation coupled to multiangle light scattering and refractive index detectors to determine their size and molar mass distribution. Two size populations were detected in the two lower viscosity classes, EHEC I and II, one high molar mass and one ultrahigh molar mass (UHM). The two covered molar masses from 10(4) up to 10(9) g.mol(-1). The highest viscosity class EHEC III was less size-dispersed covering molar masses from 5x10(5) to 5x10(7) g.mol(-1). Filtering of the EHEC II solution removed small amounts of compact UHM material. Enzyme treatments were performed on EHEC II to further characterize it. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and anion ion-exchange chromatography coupled to pulsed amperometric detection showed that the UHM component contained EHEC.
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| 14. |
- Andersson, M, et al.
(author)
-
Size and Structure Characterization of Ethylhydroxyethyl Cellulose by the Combination of Field-Flow Fractionation with Other Techniques. Investigation of Ultralarge Components
- 2004
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1526-4602 .- 1525-7797. ; 5:1, s. 97-105
-
Journal article (peer-reviewed)abstract
- Ethylhydroxyethyl cellulose (EHEC) of three different viscosity classes (EHEC I, II, and III) was analyzed by programmed cross-flow asymmetrical flow field-flow fractionation coupled to multiangle light scattering and refractive index detectors to determine their size and molar mass distribution. Two size populations were detected in the two lower viscosity classes, EHEC I and II, one high molar mass and one ultrahigh molar mass (UHM). The two covered molar masses from 104 up to 109 g·mol-1. The highest viscosity class EHEC III was less size-dispersed covering molar masses from 5 × 105 to 5 × 107 g·mol-1. Filtering of the EHEC II solution removed small amounts of compact UHM material. Enzyme treatments were performed on EHEC II to further characterize it. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and anion ion-exchange chromatography coupled to pulsed amperometric detection showed that the UHM component contained EHEC.
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| 15. |
- Andersson, Olof, et al.
(author)
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Gradient Hydrogel Matrix for Microarray and Biosensor Applications : An Imaging SPR Study
- 2009
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 10:1, s. 142-148
-
Journal article (peer-reviewed)abstract
- A biosensor matrix based on UV-initiated graft copolymerized poly(ethylene glycol) methacrylate and 2-hydroxyethyl methacrylate has been studied using imaging surface plasmon resonance (iSPR). By using a photo mask and a programmable shutter to vary the exposure time laterally, a gradient of matrix spots with physical thicknesses ranging from a few to tens of nanometers was generated. To maximize the dynamic range, imaging SPR was employed in wavelength interrogation mode. By finding the minimum in the reflectance spectra from each pixel of an image, SPR wavelength maps were constructed. The shift in SPR wavelength upon biospecific interaction was then measured both as a function of matrix thickness and composition. The performance of the matrix was evaluated in terms of immobilization of human serum albumin, biomolecular interaction with its antibody, and nonspecific binding of human fibrinogen. In addition, a low molecular weight interaction pair based on a synthetic polypeptide and calmodulin was also studied to explore the size selectivity of the hydrogel matrix. Our results show that the gradient matrix exhibits excellent properties for quick evaluation and screening of optimal hydrogel performance. The mixed hydrogel matrices display very low levels of nonspecific binding. It is also evident that the low molecular weight calmodulin is capable of freely diffusing and interacting throughout the entire hydrogel matrix, whereas the much larger albumin and its corresponding antibody, in particular, are partly/completely hindered from penetrating the interior of the matrix. This size-selectivity is attributed to a significant UV-initiated cross-linking or branching of the matrix during fabrication and/or protein mediated multipoint attachment during immobilization.
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| 16. |
- Andersson Trojer, Markus, 1981, et al.
(author)
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Quantitative Grafting for Structure-Function Establishment: Thermoresponsive Poly(alkylene oxide) Graft Copolymers Based on Hyaluronic Acid and Carboxymethylcellulose
- 2019
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 20:3, s. 1271-1280
-
Journal article (peer-reviewed)abstract
- © 2019 American Chemical Society. A series of thermoresponsive graft copolymers, gelling at physiological conditions in aqueous solution and cell growth media, have been synthesized using quantitative coupling between a small set of amino-functionalized poly(alkylene oxide) copolymers (PAO) and the carboxylate of the biologically important polysaccharides (PSa) carboxymethylcellulose and the less reactive hyaluronate. Quantitative grafting enables the establishment of structure-function relationship which is imperative for controlling the properties of in situ gelling hydrogels. The EDC/NHS-mediated reaction was monitored using SEC-MALLS, which revealed that all PAOs were grafted onto the PSa backbone. Aqueous solutions of the graft copolymers were Newtonian fluids at room temperatures and formed reversible physical gels at elevated temperatures which were noncytotoxic toward chondrocytes. The established structure-function relationship was most clearly demonstrated by inspecting the thermogelling strength and the onset of thermogelling in a phase diagram. The onset of the thermogelling function could be controlled by the global PAO concentration, independent of graft ratio.
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| 17. |
- Andronova, Natalia, et al.
(author)
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Resilient bioresorbable copolymers based on trimethylene carbonate, L-lactide, and 1,5-dioxepan-2-one
- 2006
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 7:5, s. 1489-1495
-
Journal article (peer-reviewed)abstract
- The new combinations of monomers presented in this work were evaluated in order to create an elastic material for potential application in soft tissue engineering. Thermoplastic elastomers (TPE) of trimethylene carbonate (TMC) with L-lactide (LLA) and 1,5-dioxepan-2-one (DXO) have been synthesized using a cyclic five-membered tin alkoxide initiator. The block copolymers were designed in such a way that poly(trimethylene carbonate-co1,5-dioxepan-2-one) formed an amorphous middle block and the poly(L-lactide) (PLLA) formed semicrystalline terminal blocks. The amorphous middle block consisted of relatively randomly distributed TMC and DXO monomer units, and the defined block structure of the PLLA terminal segments was confirmed by C-13 NMR. The properties of the TMC-DXO-LLA copolymers were compared with those of triblock copolymers based either on LLA-TMC or on LLA-DXO. Differential scanning calorimetry and dynamic mechanical analysis data confirmed the micro-phase separation in the copolymers. The mechanical properties of the copolymers were evaluated using tensile testing and cycling loading. All of the copolymers synthesized showed a highly elastic behavior. The properties of copolymers could be tailored by altering the proportions of the different monomers.
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| 18. |
- Ansari, Farhan, et al.
(author)
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Strong surface treatment effects on reinforcement efficiency in biocomposites based on cellulose nanocrystals in poly(vinyl acetate) matrix
- 2015
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 16:12, s. 3916-3924
-
Journal article (peer-reviewed)abstract
- In this work, the problem to disperse cellulose nanocrystals (CNC) in hydrophobic polymer matrices has been addressed through application of an environmentally friendly chemical modification approach inspired by clay chemistry. The objective is to compare the effects of unmodified CNC and modified CNC (modCNC) reinforcement, where degree of CNC dispersion is of interest. Hydrophobic functionalization made it possible to disperse wood-based modCNC in organic solvent and cast well-dispersed nanocomposite films of poly(vinyl acetate) (PVAc) with 1-20 wt % CNC. Composite films were studied by infrared spectroscopy (FT-IR), UV-vis spectroscopy, dynamic mechanical thermal analysis (DMTA), tensile testing, and field-emission scanning electron microscopy (FE-SEM). Strongly increased mechanical properties were observed for modCNC nanocomposites. The reinforcement efficiency was much lower in unmodified CNC composites, and specific mechanisms causing the differences are discussed.
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| 19. |
- Ansari, Farhan, et al.
(author)
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Toward Semistructural Cellulose Nanocomposites : The Need for Scalable Processing and Interface Tailoring
- 2018
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 19:7, s. 2341-2350
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Journal article (peer-reviewed)abstract
- Cellulose nanocomposites can be considered for semistructural load-bearing applications where modulus and strength requirements exceed 10 GPa and 100 MPa, respectively. Such properties are higher than for most neat polymers but typical for molded short glass fiber composites. The research challenge for polymer matrix biocomposites is to develop processing concepts that allow high cellulose nanofibril (CNF) content, nanostructural control in the form of well-dispersed CNF, the use of suitable polymer matrices, as well as molecular scale interface tailoring to address moisture effects. From a practical point of view, the processing concept needs to be scalable so that large-scale industrial processing is feasible. The vast majority of cellulose nanocomposite studies elaborate on materials with low nanocellulose content. An important reason is the challenge to prevent CNF agglomeration at high CNF content. Research activities are therefore needed on concepts with the potential for rapid processing with controlled nanostructure, including well-dispersed fibrils at high CNF content so that favorable properties are obtained. This perspective discusses processing strategies, agglomeration problems, opportunities, and effects from interface tailoring. Specifically, preformed CNF mats can be used to design nanostructured biocomposites with high CNF content. Because very few composite materials combine functional and structural properties, CNF materials are an exception in this sense. The suggested processing concept could include functional components (inorganic clays, carbon nanotubes, magnetic nanoparticles, among others). In functional three-phase systems, CNF networks are combined with functional components (nanoparticles or fibril coatings) together with a ductile polymer matrix. Such materials can have functional properties (optical, magnetic, electric, etc.) in combination with mechanical performance, and the comparably low cost of nanocellulose may facilitate the use of large nanocomposite structures in industrial applications.
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| 20. |
- Antlauf, Mathis, et al.
(author)
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Thermal Conductivity of Cellulose Fibers in Different Size Scales and Densities
- 2021
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 22:9, s. 3800-3809
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Journal article (peer-reviewed)abstract
- Considering the growing use of cellulose in various applications, knowledge and understanding of its physical properties become increasingly important. Thermal conductivity is a key property, but its variation with porosity and density is unknown, and it is not known if such a variation is affected by fiber size and temperature. Here, we determine the relationships by measurements of the thermal conductivity of cellulose fibers (CFs) and cellulose nanofibers (CNFs) derived from commercial birch pulp as a function of pressure and temperature. The results show that the thermal conductivity varies relatively weakly with density (ρsample = 1340–1560 kg m–3) and that its temperature dependence is independent of density, porosity, and fiber size for temperatures in the range 80–380 K. The universal temperature and density dependencies of the thermal conductivity of a random network of CNFs are described by a third-order polynomial function (SI-units): κCNF = (0.0787 + 2.73 × 10–3·T – 7.6749 × 10–6·T2 + 8.4637 × 10–9·T3)·(ρsample/ρ0)2, where ρ0 = 1340 kg m–3 and κCF = 1.065·κCNF. Despite a relatively high degree of crystallinity, both CF and CNF samples show amorphous-like thermal conductivity, that is, it increases with increasing temperature. This appears to be due to the nano-sized elementary fibrils of cellulose, which explains that the thermal conductivity of CNFs and CFs shows identical behavior and differs by only ca. 6%. The nano-sized fibrils effectively limit the phonon mean free path to a few nanometers for heat conduction across fibers, and it is only significantly longer for highly directed heat conduction along fibers. This feature of cellulose makes it easier to apply in applications that require low thermal conductivity combined with high strength; the weak density dependence of the thermal conductivity is a particularly useful property when the material is subjected to high loads. The results for thermal conductivity also suggest that the crystalline structures of cellulose remain stable up to at least 0.7 GPa.
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| 21. |
- Arcos-Hernandez, Monica, et al.
(author)
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Thermoresponsive Glycopolymers Based on Enzymatically Synthesized Oligo-β-Mannosyl Ethyl Methacrylates and N-Isopropylacrylamide
- 2021
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1526-4602 .- 1525-7797. ; 22:6, s. 2338-2351
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Journal article (peer-reviewed)abstract
- We here present a series of thermoresponsive glycopolymers in the form of poly(N-isopropylacrylamide)-co-(2-[β-manno[oligo]syloxy] ethyl methacrylate)s. These copolymers were prepared from oligo-β-mannosyl ethyl methacrylates that were synthesized through enzymatic catalysis, and were subsequently investigated with respect to their aggregation and phase behavior in aqueous solution using a combination of 1H NMR spectroscopy, dynamic light scattering, cryogenic transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). The thermoresponsive glycopolymers were prepared by conventional free radical copolymerizations of different mixtures of 2-(β-manno[oligo]syloxy)ethyl methacrylates (with either one or two saccharide units) and N-isopropyl acrylamide (NIPAm). The results showed that below the lower critical solution temperature (LCST) of poly(NIPAm), the glycopolymers readily aggregate into nanoscale structures, partly due to the presence of the saccharide moieties. Above the LCST of poly(NIPAm), the glycopolymers rearrange into a heterogeneous mixture of fractal and disc/globular aggregates. Cryo-TEM and SAXS data demonstrated that the presence of the pendant β-mannosyl moieties in the glycopolymers induces a gradual conformational change over a wide temperature range. Even though the onset of this transition is not different from the LCST of poly(NIPAm), this gradual conformational change offers a variation of the temperature-dependent properties in comparison to poly(NIPAm), which displays a sharp coil-to-globule transition. Importantly, the compacted form of the glycopolymers show a larger colloidal stability compared to the unmodified poly(NIPAm). In addition, the thermoresponsiveness can be conveniently tuned by varying the sugar unit-length and the oligo-β-mannosyl ethyl methacrylate content.
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| 22. |
- Areskogh, Dimitri, et al.
(author)
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Investigation of the Molecular Weight Increase of Commercial Lignosulfonates by Laccase Catalysis
- 2010
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 11:4, s. 904-910
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Journal article (peer-reviewed)abstract
- Lignosulfonates are by-products from the sulfite pulping process. During this process, lignin is liberated from pulp fibers through sulfonation and washed away. As a consequence, the lignosulfonate molecules contain both hydrophobic and hydrophilic moieties. Lignosulfonates are low-value products with limited performance and are used as such as binders, surfactants, and plasticizers in concrete. Lignosulfonates face strong competition from synthetic petroleum-based plasticizers with superior quality. Therefore, increasing the performance of lignosulfonates is desirable not only from a sustainability point of view but also to expand their usage. One important aspect that describes how well lignosulfonates can act as plasticizers is the molecular weight. In this paper, the molecular weight of four commercial lignosulfonates is increased through oxidation by two laccases without utilization of mediators. Different parameters to obtain maximal molecular weight increase were identified and the technical significance of the experiments is discussed.
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| 23. |
- Arias, Veluska, et al.
(author)
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Tuning the Degradation Profiles of Poly(L-lactide)-Based Materials through Miscibility
- 2014
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 15:1, s. 391-402
-
Journal article (peer-reviewed)abstract
- The effective use of biodegradable polymers relies on the ability to control the onset of and time needed for degradation. Preferably, the material properties should be retained throughout the intended time frame, and the material should degrade in a rapid and controlled manner afterward. The degradation profiles of polyester materials were controlled through their miscibility. Systems composed of PLLA blended with poly[(R,S)-3-hydroxybutyrate] (a-PHB) and polypropylene adipate (PPA) with various molar masses were prepared through extrusion. Three different systems were used: miscible (PLLA/a-PHB5 and PLLA/a-PHB20), partially miscible (PLLA/PPA5/comp and PLLA/PPA20/comp), and immiscible (PLLA/PPA5 and PLLA/PPA20) blends. These blends and their respective homopolymers were hydrolytically degraded in water at 37 degrees C for up to I year. The blends exhibited entirely different degradation profiles but showed no diversity between the total degradation times of the materials. PLLA presented a two-stage degradation profile with a rapid decrease in molar mass during the early stages of degradation, similar to the profile of PLLA/a-PHB5. PLLA/a-PHB20 presented a single, constant linear degradation profile. PLLA/PPA5 and PLLA/PPA20 showed completely opposing degradation profiles relative to PLLA, exhibiting a slow initial phase and a rapid decrease after a prolonged degradation time. PLLA/PPA5/comp and PLLA/PPA20/comp had degradation profiles between those of the miscible and the immiscible blends. The molar masses of the materials were approximately the same after 1 year of degradation despite their different profiles. The blend composition and topographical images captured at the last degradation time point demonstrate that the blending component was not leached out during the period of study. The hydrolytic stability of degradable polyester materials can be tailored to obtain different and predetermined degradation profiles for future applications.
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| 24. |
- Arumughan, Vishnu, 1994, et al.
(author)
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Calcium Ion-Induced Structural Changes in Carboxymethylcellulose Solutions and Their Effects on Adsorption on Cellulose Surfaces
- 2022
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 23:1, s. 47-56
-
Journal article (peer-reviewed)abstract
- The adsorption of carboxymethylcellulose (CMC) on cellulose surfaces is one of the most studied examples of the adsorption of an anionic polyelectrolyte on a like-charged surface. It has been suggested that divalent ions can act as a bridge between CMC chains and the surface of cellulose and enhance the CMC adsorption: they can, however, also alter the structure of CMCs in the solution. In previous investigations, the influence of cations on solution properties has been largely overlooked. This study investigates the effect of Ca2+ ions on the properties of CMC solutions as well as the influence on cellulose nanofibers (CNFs), which was studied by dynamic light scattering and correlated with the adsorption of CMC on a cellulose surface probed using QCMD. The presence of Ca2+ facilitated the multichain association of CMC chains and increased the hydrodynamic diameter. This suggests that the adsorption of CMCs at high concentrations of CaCl2 is governed mainly by changes in solution properties rather than by changes in the cellulose surface. Furthermore, an entropy-driven mechanism has been suggested for the adsorption of CMC on cellulose. By comparing the adsorption of CMC from H2O and D2O, it was found that the release of water from the cellulose surface is driving the adsorption of CMC.
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| 25. |
- Asplund, J. O. Basse, et al.
(author)
-
Synthesis of highly elastic biodegradable poly(urethane urea)
- 2007
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 8:3, s. 905-911
-
Journal article (peer-reviewed)abstract
- Linear poly(urethane urea) containing a biodegradable soft segment and a hard segment built solely from methyl-2,6-diisocyanatehexanoate (LDI) is presented, using a procedure where no chain extender is required. By having LDI in excess, together with a soft segment, and adding water in the vapor phase continuously creates amines in situ resulting in hard segments containing multiple LDI units linked via urea linkages. As soft segments, polymers of trimethylene carbonate (TMC) and copolymers of TMC, ε-caprolactone, and d,l-lactic acid (DLLA) were used. High inherent viscosity, 0.95−1.65 dL/g, was afforded even when DLLA-containing soft segments were used, which usually undergo aminolysis. With a hard segment content between 12% and 18%, all of the materials showed very high elongation at breakage, ranging from 1600% to 4700%, and an elastic modulus from 2.1 to 140 MPa. This one-pot synthesis is simple and has now been shown to be applicable to a large number of systems.
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| 26. |
- Atoufi, Zhaleh, et al.
(author)
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Green Ambient-Dried Aerogels with a Facile pH-Tunable Surface Charge for Adsorption of Cationic and Anionic Contaminants with High Selectivity
- 2022
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 23:11, s. 4934-4947
-
Journal article (peer-reviewed)abstract
- The fabrication of reusable, sustainable adsorbents from low-cost, renewable resources via energy efficient methods is challenging. This paper presents wet-stable, carboxymethylated cellulose nanofibril (CNF) and amyloid nanofibril (ANF) based aerogel-like adsorbents prepared through efficient and green processes for the removal of metal ions and dyes from water. The aerogels exhibit tunable densities (18-28 kg m-3), wet resilience, and an interconnected porous structure (99% porosity), with a pH controllable surface charge for adsorption of both cationic (methylene blue and Pb(II)) and anionic (brilliant blue, congo red, and Cr(VI)) model contaminants. The Langmuir saturation adsorption capacity of the aerogel was calculated to be 68, 79, and 42 mg g-1for brilliant blue, Pb(II), and Cr(VI), respectively. Adsorption kinetic studies for the adsorption of brilliant blue as a model contaminant demonstrated that a pseudo-second-order model best fitted the experimental data and that an intraparticle diffusion model suggests that there are three adsorption stages in the adsorption of brilliant blue on the aerogel. Following three cycles of adsorption and regeneration, the aerogels maintained nearly 97 and 96% of their adsorption capacity for methylene blue and Pb(II) as cationic contaminants and 89 and 80% for brilliant blue and Cr(VI) as anionic contaminants. Moreover, the aerogels showed remarkable selectivity for Pb(II) in the presence of calcium and magnesium as background ions, with a selectivity coefficient more than 2 orders of magnitude higher than calcium and magnesium. Overall, the energy-efficient and sustainable fabrication procedure, along with good structural stability, reusability, and selectivity, makes these aerogels very promising for water purification applications.
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| 27. |
- Atthoff, Björn, et al.
(author)
-
Synthetic Biodegradable Ionomers that Engulf, Store, and Deliver Intact Proteins
- 2006
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 7:8, s. 2401-2406
-
Journal article (peer-reviewed)abstract
- Telechelic anionic and cationic biodegradable ionomers capable of loading, storing, and releasing proteins are presented. Two different ionomers have been synthesized with either anionic or cationic end groups. The reaction was done quantitatively as shown by 1H NMR. The swelling properties of the hydrophobic poly(trimethylene carbonate) polymer are contributed to the ionic end groups that display hydrophilic properties. Depending on the molecular weight of the ionomer, and also on the ionic charge, the materials swell differently in water, from ~50% for Mw = 12 000 g/mol to ~500% when dealing with 2000 g/mol. The high swelling led us to believe that it would be possible to load and release proteins preferably in a still active form. As models, two different proteins were chosen: hemoglobin and cytochrome c. The swelling and release study shows that both ionomers possess the capability to adsorb and later release the proteins with retained structure. Release measurements from both the swollen and dried states have been evaluated with similar results, showing that the dried state seems to release a little bit less than the swollen one. These kinds of materials should be interesting for a wide variety of applications where drug and protein release is wanted, as well as in applications such as protein separation media.
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| 28. |
- Aulin, Christian, et al.
(author)
-
Self-Organized Films from Cellulose I Nanofibrils Using the Layer-by-Layer Technique
- 2010
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 11:4, s. 872-882
-
Journal article (peer-reviewed)abstract
- The possibility of forming self-organized films using only charge-stabilized dispersions of cellulose I nanofibrils with opposite charges is presented, that is, the multilayers were composed solely of anionically and cationically modified microfibrillated cellulose (MFC) with a low degree of substitution. The build-up behavior and the properties of the layer-by-layer (LbL)-constructed films were studied using a quartz crystal microbalance with dissipation (QCM-D) and stagnation point adsorption reflectometry (SPAR). The adsorption behavior of cationic/anionic MFC was compared with that of polyethyleneimine (PEI)/anionic MFC. The water contents of five bilayers of cationic/anionic MFC and PEI/anionic MFC were approximately 70 and 50%, respectively. The MFC surface coverage was studied by atomic force microscopy (AFM) measurements, which clearly showed a more dense fibrillar structure in the five bilayer PEI/anionic MFC than in the five bilayer cationic/anionic MFC. The forces between the cellulose-based multilayers were examined using the AFM colloidal probe technique. The forces on approach were characterized by a combination of electrostatic and steric repulsion. The wet adhesive forces were very long-range and were characterized by multiple adhesive events. Surfaces covered by PEU/anionic MFC multilayers required more energy to be separated than surfaces covered by cationic/anionic MFC multilayers.
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| 29. |
- Azizi Samir, M. A. S., et al.
(author)
-
Review of recent research into cellulosic whiskers, their properties and their application in nanocomposite field
- 2005
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 6:2, s. 612-626
-
Journal article (peer-reviewed)abstract
- There are numerous examples where animals or plants synthesize extracellular high-performance skeletal biocomposites consisting of a matrix reinforced by fibrous biopolymers. Cellulose, the world's most abundant natural, renewable, biodegradable polymer, is a classical example of these reinforcing elements, which occur as whiskerlike microfibrils that are biosynthesized and deposited in a continuous fashion. In many cases, this mode of biogenesis leads to crystalline microfibrils that are almost defect-free, with the consequence of axial physical properties approaching those of perfect crystals. This quite "primitive" polymer can be used to create high performance nanocomposites presenting outstanding properties. This reinforcing capability results from the intrinsic chemical nature of cellulose and from its hierarchical structure. Aqueous suspensions of cellulose crystallites can be prepared by acid hydrolysis of cellulose. The object of this treatment is to dissolve away regions of low lateral order so that the water-insoluble, highly crystalline residue may be converted into a stable suspension by subsequent vigorous mechanical shearing action. During the past decade, many works have been devoted to mimic biocomposites by blending cellulose whiskers from different sources with polymer matrixes.
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| 30. |
- Babi, Mouhanad, et al.
(author)
-
Efficient Labeling of Nanocellulose for High-Resolution Fluorescence Microscopy Applications
- 2022
-
In: Biomacromolecules. - : American Chemical Society. - 1525-7797 .- 1526-4602. ; 23:5, s. 1981-1994
-
Journal article (peer-reviewed)abstract
- The visualization of naturally derived cellulose nanofibrils (CNFs) and nanocrystals (CNCs) within nanocomposite materials is key to the development of packaging materials, tissue culture scaffolds, and emulsifying agents, among many other applications. In this work, we develop a versatile and efficient two-step approach based on triazine and azide-alkyne click-chem. to fluorescently label nanocelluloses with a variety of com. available dyes. We show that this method can be used to label bacterial cellulose fibrils, plant-derived CNFs, carboxymethylated CNFs, and CNCs with Cy5 and fluorescein derivatives to high degrees of labeling using minimal amounts of dye while preserving their native morphol. and crystalline structure. The ability to tune the labeling d. with this method allowed us to prepare optimized samples that were used to visualize nanostructural features of cellulose through super-resolution microscopy. The efficiency, cost-effectiveness, and versatility of this method make it ideal for labeling nanocelluloses and imaging them through advanced microscopy techniques for a broad range of applications.
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| 31. |
- Bamba, Yu, et al.
(author)
-
Estimating the Strength of Single Chitin Nanofibrils via Sonication-Induced Fragmentation
- 2017
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 18:12, s. 4405-4410
-
Journal article (peer-reviewed)abstract
- We report the mechanical strength of native chitin nanofibrils. Highly crystalline alpha-chitiri nanofibrils Were purified from filaments produced by a microalgae Phaeocystis globosa, and two types of beta-chitin nariofibrils were purified from pens of a squid Loligo bleekeri and tubes of a tubeworm Lamellibrachia satsuma, with relatively low and high crystallinity, respectively. These chitin nanofibrils were fully dispersed in water. The strength of individualized nanofibrils was estimated using cavitation induced tensile fracture of nanoscale filaments in a liquid medium. Both types of beta-chitin nanofibrils exhibited similar strength values of approximately 3 GP; in contrast, the alpha-chitin nanofibrils exhibited a much lower strength value of 1.6 GPa. These strength estimates suggest that the tensile strength of chitin nanofibrils is governed by the molecular packing modes of chitin rather than their crystallinity.
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| 32. |
- Baş, Yağmur, et al.
(author)
-
Preparation and Characterization of Softwood and Hardwood Nanofibril Hydrogels: Toward Wound Dressing Applications
- 2023
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 24:12, s. 5605-5619
-
Journal article (peer-reviewed)abstract
- Hydrogels of cellulose nanofibrils (CNFs) are promising wound dressing candidates due to their biocompatibility, high water absorption, and transparency. Herein, two different commercially available wood species, softwood and hardwood, were subjected to TEMPO-mediated oxidation to proceed with delignification and oxidation in a one-pot process, and thereafter, nanofibrils were isolated using a high-pressure microfluidizer. Furthermore, transparent nanofibril hydrogel networks were prepared by vacuum filtration. Nanofibril properties and network performance correlated with oxidation were investigated and compared with commercially available TEMPO-oxidized pulp nanofibrils and their networks. Softwood nanofibril hydrogel networks exhibited the best mechanical properties, and in vitro toxicological risk assessment showed no detrimental effect for any of the studied hydrogels on human fibroblast or keratinocyte cells. This study demonstrates a straightforward processing route for direct oxidation of different wood species to obtain nanofibril hydrogels for potential use as wound dressings, with softwood having the most potential.
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| 33. |
- Benselfelt, Tobias, et al.
(author)
-
Adsorption of Xyloglucan onto Cellulose Surfaces of Different Morphologies : An Entropy-Driven Process
- 2016
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 17:9, s. 2801-2811
-
Journal article (peer-reviewed)abstract
- The temperature-dependence of xyloglucan (XG) adsorption onto smooth cellulose model films regenerated from N-methylmorpholine N-oxide (NMMO) was investigated using surface plasmon resonance spectroscopy, and it was found that the adsorbed amount increased with increasing temperature. This implies that the adsorption of XG to NMMO-regenerated cellulose is endothermic and supports the hypothesis that the adsorption of XG onto cellulose is an entropy-driven process. We suggest that XG adsorption is mainly driven by the release of water molecules from the highly hydrated cellulose surfaces and from the XG molecules, rather than through hydrogen bonding and van der Waals forces as previously suggested. To test this hypothesis, the adsorption of XG onto cellulose was studied using cellulose films with different morphologies prepared from cellulose nanocrystals (CNC), semicrystalline NMMO-regenerated cellulose, and amorphous cellulose regenerated from lithium chloride/dimethylacetamide. The total amount of high molecular weight xyloglucan (XGHMW) adsorbed was studied by quartz crystal microbalance and reflectometry measurements, and it was found that the adsorption was greatest on the amorphous cellulose followed by the CNC and NMMO-regenerated cellulose films. There was a significant correlation between the cellulose dry film thickness and the adsorbed XG amount, indicating that XG penetrated into the films. There was also a correlation between the swelling of the films and the adsorbed amounts and conformation of XG, which further strengthened the conclusion that the water content and the subsequent release of the water upon adsorption are important components of the adsorption process.
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| 34. |
- Benselfelt, Tobias, et al.
(author)
-
Unidirectional Swelling of Dynamic Cellulose Nanofibril Networks : A Platform for Tunable Hydrogels and Aerogels with 3D Shapeability
- 2019
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 20:6, s. 2406-2412
-
Journal article (peer-reviewed)abstract
- A process has been developed to create self-supporting hydrogels with low solids content (down to 0.5 wt %) and anisotropic aerogels with a low density (down to 5 kg/m(3)) from cellulose nanofibrils (CNFs). The CNF networks were formed by vacuum filtration of dilute dispersions (0.2 wt %) of 90% CNFs and 10% alginate. We call this process "the dynamic CNF network approach" since the solids content of these hydrogels can be tuned in the range of 0.5-3 wt % by reswelling the filter cakes in a medium with a controlled osmotic pressure. These hydrogels are significantly stronger than the 1-2 wt % CNF gels typically used to prepare hydrogels and aerogels because the dynamic CNF networks are formed below their arrested state threshold (ca. 0.5 wt %) and are thus homogeneous. The vacuum filtration leads to a directional reswelling vertical to the plane of the filter cake, and this is crucial in order to turn a two-dimensional (2D) shape, cut from the filter cake, into a 3D hydrogel without distorting the 2D shape. The anisotropic swelling was used to create intricate 3D-shaped hydrogels and solved some of the issues involved in the degassing and molding of high-viscosity CNF gels. Multivalent ions were used to lock the CNF and alginate networks at the desired solids content and 3D shape, and resulted in an increase by an order of magnitude in storage modulus. Moreover, the self-supporting nature of the hydrogels allowed us to freeze-cast them into anisotropic aerogels with the same 3D shape without using any container. The 5 kg/m(3) aerogel had a specific modulus of 43 kN m/kg and an anisotropy index of 12, which are impressive properties in relation to earlier experiences. The process can be used for applications where a precise control of density and shape is critical.
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| 35. |
- Benyahia Erdal, Nejla, et al.
(author)
-
Cellulose-Derived Nanographene Oxide Surface-Functionalized Three-Dimensional Scaffolds with Drug Delivery Capability
- 2019
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 20:2, s. 738-749
-
Journal article (peer-reviewed)abstract
- Multifunctional three-dimensional (3D) scaffolds were targeted by surface grafting cellulose-derived nanographene oxide (nGO) on the surface of porous poly(epsilon-caprolactone) (PCL) scaffolds. nGO was derived from cellulose by microwave-assisted carbonization process and covalently grafted onto aminolyzed PCL scaffolds through an aqueous solution process. Fourier transform infrared spectroscopy and thermogravimetric analysis both verified the successful attachment of nGO and scanning electron microscopy depicted a homogeneous dispersion of nGO over the scaffold surface. Mechanical tests were performed and demonstrated a significant increase in compressive strength for the nGO grafted scaffolds. Grafting of nGO was also shown to induce mineralization with the formation of calcium phosphate precipitates on the surface of the scaffolds with the size increasing with higher nGO content. The potential of surface-grafted nGO as a nanocarrier of an antibiotic drug was also explored. The secondary interactions between nGO and ciprofloxacin, a broad-spectrum antibiotic used in the treatment of osteomyelitis, were optimized by controlling the solution pH. Ciprofloxacin was found to be adsorbed most strongly in its cationic form at pH 5, in which pi-pi electron donor-acceptor interactions predominate and the adsorbed drug content increased with increasing nGO amount. Further, the release kinetics of the drug were investigated during 8 days. In conclusion, the proposed simple fabrication process led to a scaffold with multifunctionality in the form of improved mechanical strength, ability to induce mineralization, as well as drug loading and delivery capability.
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| 36. |
- Benyahia Erdal, Nejla, et al.
(author)
-
Construction of Bioactive and Reinforced Bioresorbable Nanocomposites by Reduced Nano-Graphene Oxide Carbon Dots
- 2018
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 19:3, s. 1074-1081
-
Journal article (peer-reviewed)abstract
- Bioactive and reinforced poly(ϵ-caprolactone) (PCL) films were constructed by incorporation of cellulose derived reduced nanographene oxide (r-nGO) carbon nanodots. Two different microwave-assisted reduction routes in superheated water were utilized to obtain r-nGO and r-nGO-CA. For the latter, a green reducing agent caffeic acid (CA), was incorporated in the reduction process. The materials were extruded and compression molded to obtain proper dispersion of the carbon nanodots in the polymer matrix. FTIR results revealed favorable interactions between r-nGO-CA and PCL that improved the dispersion of r-nGO-CA. r-nGO, and r-nGO-CA endorsed PCL with several advantageous functionalities including improved storage modulus and creep resistance. The considerable increase in storage modulus demonstrated that the carbon nanodots had a significant reinforcing effect on PCL. The PCL films with r-nGO-CA were also evaluated for their osteobioactivity and cytocompatibility. Bioactivity was demonstrated by formation of hydroxyapatite (HA) minerals on the surface of r-nGO-CA loaded nanocomposites. At the same time, the good cytocompatibility of PCL was retained as illustrated by the good cell viability to MG63 osteoblast-like cells giving promise for bone tissue engineering applications.
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| 37. |
- Benyahia Erdal, Nejla, et al.
(author)
-
Degradation of Cellulose Derivatives in Laboratory, Man-Made, and Natural Environments
- 2022
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 23:7, s. 2713-2729
-
Journal article (peer-reviewed)abstract
- Biodegradable polymers complement recyclable materials in battling plastic waste because some products are difficult to recycle and some will end up in the environment either because of their application or due to wear of the products. Natural biopolymers, such as cellulose, are inherently biodegradable, but chemical modification typically required for the obtainment of thermoplastic properties, solubility, or other desired material properties can hinder or even prevent the biodegradation process. This Review summarizes current knowledge on the degradation of common cellulose derivatives in different laboratory, natural, and man-made environments. Depending on the environment, the degradation can be solely biodegradation or a combination of several processes, such as chemical and enzymatic hydrolysis, photodegradation, and oxidation. It is clear that the type of modification and especially the degree of substitution are important factors controlling the degradation process of cellulose derivatives in combination with the degradation environment. The big variation of conditions in different environments is also briefly considered as well as the importance of the proper testing environment, characterization of the degradation process, and confirmation of biodegradability. To ensure full sustainability of the new cellulose derivatives under development, the expected end-of-life scenario, whether material recycling or "biological"recycling, should be included as an important design parameter.
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| 38. |
- Berezhnoy, Nikolay V., et al.
(author)
-
Supramolecular Organization in Self-Assembly of Chromatin and Cationic Lipid Bilayers is Controlled by Membrane Charge Density
- 2012
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1526-4602 .- 1525-7797. ; 13:12, s. 4146-4157
-
Journal article (peer-reviewed)abstract
- In this work we have investigated the structures of aggregates formed in model systems of dilute aqueous mixtures of "model chromatin" consisting of either recombinant nucleosome core particles (NCPs) or nucleosome arrays consisting of 12 NCPs connected with 30 bp linker DNA, and liposomes made from different mixtures of cationic and zwitterionic lipids, 1,2-dioleoyl-3-trimethylammonium-propane chloride salt (DOTAP) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). The aggregates formed were characterized using different optical microscopy methods and small-angle X-ray scattering (SAXS), and the results are discussed in terms of the competing intermolecular interactions among the components. For a majority of the samples, the presence of lamellar structures could be identified. Ir. samples with high fractions of DOTAP in the liposomes, well-defined lamellar structures very similar to those formed by the corresponding lipid mixtures and DNA alone (i.e., without histone proteins) were observed; in these aggregates, the histones are expelled from the model chromatin. The findings suggest that, with liposomes containing large fractions of cationic lipid, the dominating driving force for aggregation is the increase in translational entropy from the release of counterions, whereas with lower fractions of the cationic lipid, the entropy of mixing of the lipids within the bilayers results in a decreased DNA-lipid attraction.
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| 39. |
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| 40. |
- Berglund, Linn, et al.
(author)
-
Self-Assembly of Nanocellulose Hydrogels Mimicking Bacterial Cellulose for Wound Dressing Applications
- 2023
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 24:5, s. 2264-2277
-
Journal article (peer-reviewed)abstract
- The self-assembly of nanocellulose in the form of cellulose nanofibers (CNFs) can be accomplished via hydrogen-bonding assistance into completely bio-based hydrogels. This study aimed to use the intrinsic properties of CNFs, such as their ability to form strong networks and high absorption capacity and exploit them in the sustainable development of effective wound dressing materials. First, TEMPO-oxidized CNFs were separated directly from wood (W-CNFs) and compared with CNFs separated from wood pulp (P-CNFs). Second, two approaches were evaluated for hydrogel self-assembly from W-CNFs, where water was removed from the suspensions via evaporation through suspension casting (SC) or vacuum-assisted filtration (VF). Third, the W-CNF-VF hydrogel was compared to commercial bacterial cellulose (BC). The study demonstrates that the self-assembly via VF of nanocellulose hydrogels from wood was the most promising material as wound dressing and displayed comparable properties to that of BC and strength to that of soft tissue.
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| 41. |
- Bergman, Kristoffer, et al.
(author)
-
Hyaluronic acid derivatives prepared in aqueous media by triazine-activated amidation
- 2007
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 8:7, s. 2190-2195
-
Journal article (peer-reviewed)abstract
- A method is presented for the preparation of hyaluronic acid derivatives obtained through triazine-activated amidation. A number of amines were successfully reacted with hyaluronic acid carboxyl groups using 2-chloro-4,6-dimethoxy-1,3,5-triazine as an activating species in a mixture of water and acetonitrile under neutral conditions. By varying the amount of triazine reagent, it was possible to control the degree of modification. Depending on the amine chosen, degrees of modification ranging from 3 to 20% were obtained when using 0.5 equiv of the triazine to hyaluronic acid carboxyl groups. The possibility to perform the reaction in a mixture of water and acetonitrile facilitates the introduction of a wide range of both hydrophilic and hydrophobic amines. Triazine-activated amidation appears to be a highly versatile, controllable, and relatively mild technique for modification of hyaluronic acid, and we predict that it will be useful in the design of novel hyaluronic acid based biomaterials.
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| 42. |
- Berillo, Dmitry, et al.
(author)
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Cryogelation of Chitosan Using Noble-Metal Ions: In Situ Formation of Nanoparticles.
- 2014
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1526-4602 .- 1525-7797. ; 15:6, s. 2246-2255
-
Journal article (peer-reviewed)abstract
- One of the purposes of the project was to develop the method of preparation of 3D macroporous hydrogel with a structure of interconnected pores by the use of noncovalent interactions. The combination of chitosan and noble-metal complexes was investigated as cross-linking agents for the preparation of ionic cryogels (ICs). Furthermore, the treatment of the ICs containing gold complex by glutaraldehyde results in spontaneous formation of gold nanoparticles (AuNPs) and chemical cross-linking of the cryogel. The characterization of prepared macroporous materials was carried out by the use of FTIR, SEM, TEM techniques, and texture analyzer. A new strategy for control of size distribution of AuNPs was suggested. The size distribution of obtained AuNPs and their population inside of walls of cryogels was estimated. A method for quantifying unreacted chloroauric acid in the presence of acetic acid was proposed. The possibility of use of prepared cryogels with immobilized AuNPs as a catalytic flow through reactor is shown.
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| 43. |
- Bermejo-Velasco, Daniel, 1985-, et al.
(author)
-
Modulating thiol pKa promotes disulfide formation at physiological pH : An elegant strategy to design disulfide cross-linked hyaluronic acid hydrogels
- 2019
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 20:3, s. 1412-1420
-
Journal article (peer-reviewed)abstract
- The disulfide bond plays a crucial role in protein biology and has been exploited by scientists to develop antibody-drug conjugates, sensors and for the immobilization other biomolecules to materials surfaces. In spite of its versatile use, the disulfide chemistry suffers from some inevitable limitations such as the need for basic conditions (pH > 8.5), strong oxidants and long reaction times. We demonstrate here that thiol-substrates containing electron-withdrawing groups at the β-position influence the deprotonation of the thiol group, which is the key reaction intermediate in the formation of disulfide bonds. Evaluation of reaction kinetics using small molecule substrate such as L-cysteine indicated disulfide formation at a 2.8-fold higher (k1 = 5.04 x 10-4 min-1) reaction rate as compared to the conventional thiol substrate, namely 3-mercaptopropionic acid (k1 = 1.80 x 10-4 min-1) at physiological pH (pH 7.4). Interestingly, the same effect could not be observed when N-acetyl-L-cysteine substrate (k1 = 0.51 x 10-4 min-1) was used. We further grafted such thiol-containing molecules (cysteine, N-acetyl-cysteine, and 3-mercaptopropionic acid) to a biopolymer namely hyaluronic acid (HA) and determined the pKa value of different thiol groups by spectrophotometric analysis. The electron-withdrawing group at the β-position reduced the pKa of the thiol group to 7.0 for HA-cysteine (HA-Cys); 7.4 for N-acetyl cysteine (HA-ActCys) and 8.1 for HA-thiol (HA-SH) derivatives respectively. These experiments further confirmed that the concentration of thiolate (R-S-) ions could be increased with the presence of electron-withdrawing groups, which could facilitate disulfide cross-linked hydrogel formation at physiological pH. Indeed, HA grafted with cysteine or N-acetyl groups formed hydrogels within 3.5 minutes or 10 hours, respectively at pH 7.4. After completion of crosslinking reaction both gels demonstrated a storage modulus G’ ≈3300–3500 Pa, indicating comparable levels of crosslinking. The HA-SH gel, on the other hand, did not form any gel at pH 7.4 even after 24 h. Finally, we demonstrated that the newly prepared hydrogels exhibited excellent hydrolytic stability but can be degraded by cell-directed processes (enzymatic and reductive degradation). We believe our study provides a valuable insight on the factors governing the disulfide formation and our results are useful to develop strategies that would facilitate generation of stable thiol functionalized biomolecules or promote fast thiol oxidation according to the biomedical needs.
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| 44. |
- Bettelli, Mercedes, et al.
(author)
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Sustainable Wheat Protein Biofoams : Dry Upscalable Extrusion at Low Temperature
- 2022
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 23:12, s. 5116-5126
-
Journal article (peer-reviewed)abstract
- Glycerol-plasticized wheat gluten was explored for producing soft high-density biofoams using dry upscalable extrusion (avoiding purposely added water). The largest pore size was obtained when using the food grade ammonium bicarbonate (ABC) as blowing agent, also resulting in the highest saline liquid uptake. Foams were, however, also obtained without adding a blowing agent, possibly due to a rapid moisture uptake by the dried protein powder when fed to the extruder. ABC's low decomposition temperature enabled extrusion of the material at a temperature as low as 70 °C, well below the protein aggregation temperature. Sodium bicarbonate (SBC), the most common food-grade blowing agent, did not yield the same high foam qualities. SBC's alkalinity, and the need to use a higher processing temperature (120 °C), resulted in high protein cross-linking and aggregation. The results show the potential of an energy-efficient and industrially upscalable low-temperature foam extrusion process for competitive production of sustainable biofoams using inexpensive and readily available protein obtained from industrial biomass (wheat gluten).
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| 45. |
- Bjurhager, Ingela, et al.
(author)
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State of degradation in archeological oak from the 17th century vasa ship : Substantial strength loss correlates with reduction in (holo)cellulose molecular weight
- 2012
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; :8, s. 2521-2527
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Journal article (peer-reviewed)abstract
- In 1628, the Swedish warship Vasa capsized on her maiden voyage and sank in the Stockholm harbor. The ship was recovered in 1961 and, after polyethylene glycol (PEG) impregnation, it was displayed in the Vasa museum. Chemical investigations of the Vasa were undertaken in 2000, and extensive holocellulose degradation was reported at numerous locations in the hull. We have now studied the longitudinal tensile strength of Vasa oak as a function of distance from the surface. The PEG-content, wood density, and cellulose microfibril angle were determined. The molar mass distribution of holocellulose was determined as well as the acid and iron content. A good correlation was found between the tensile strength of the Vasa oak and the average molecular weight of the holocellulose, where the load-bearing cellulose microfibril is the critical constituent. The mean tensile strength is reduced by approximately 40%, and the most affected areas show a reduction of up to 80%. A methodology is developed where variations in density, cellulose microfibril angle, and PEG content are taken into account, so that cell wall effects can be evaluated in wood samples with different rate of impregnation and morphologies.
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| 46. |
- Bjurhager, Ingela, et al.
(author)
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Ultrastructure and Mechanical Properties of Populus Wood with Reduced Lignin Content Caused by Transgenic Down-Regulation of Cinnamate 4-Hydroxylase
- 2010
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 11:9, s. 2359-2365
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Journal article (peer-reviewed)abstract
- Several key enzymes in lignin biosynthesis of Populus have been down-regulated by transgenie approaches to investigate their role in wood lignification and to explore their potential for lignin modification. Cinnamate 4-hydroxylase is an enzyme in the early phenylpropanoid pathway that has not yet been functionally analyzed in Populus. This study shows that down-regulation of cinnamate 4-hydroxylase reduced Klason lignin content by 30% with no significant change in syringyl to guaiacyl ratio. The lignin reduction resulted in ultrastructural differences of the wood and a 10% decrease in wood density. Mechanical properties investigated by tensile tests and dynamic mechanical analysis showed a decrease in stiffness, which could be explained by the lower density. The study demonstrates that a large modification in lignin content only has minor influences on tensile properties of wood in its axial direction and highlights the usefulness of wood modified beyond its natural variation by transgene technology in exploring the impact of wood biopolymer composition and ultrastructure on its material properties.
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| 47. |
- Blomfeldt, Thomas O. J., et al.
(author)
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Mechanical Properties and Network Structure of Wheat Gluten Foams
- 2011
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 12:5, s. 1707-1715
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Journal article (peer-reviewed)abstract
- This Article reports the influence of the protein network structure on the mechanical properties of foams produced from commercial wheat gluten using freeze-drying. Foams were produced from alkaline aqueous solutions at various gluten concentrations with or without glycerol, modified with bacterial cellulose nanosized fibers, or both. The results showed that 20 wt % glycerol was sufficient for plasticization, yielding foams with low modulus and high strain recovery. It was found that when fibers were mixed into the foams, a small but insignificant increase in elastic modulus was achieved, and the foam structure became more homogeneous. SEM indicated that the compatibility between the fibers and the matrix was good, with fibers acting as bridges in the cell walls. IR spectroscopy and SE-HPLC revealed a relatively low degree of aggregation, which was highest in the presence of glycerol. Confocal laser scanning microscopy revealed distinct differences in HMW-glutenin subunits and gliadin distributions for all of the different samples.
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| 48. |
- Bodin, Aase Katarina, 1977, et al.
(author)
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Modification of nanocellulose with a xyloglucan-RGD conjugate enhances adhesion and proliferation of endothelial cells: implications for tissue engineering.
- 2007
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1526-4602 .- 1525-7797. ; 8:12, s. 3697-3704
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Journal article (peer-reviewed)abstract
- This paper describes a novel method for introducing the RGD cell adhesion peptide to enhance cell adhesion onto bacterial cellulose (BC). BC and cotton linters as reference were modified with xyloglucan (XG) and xyloglugan bearing a GRGDS pentapeptide. The adsorptions followed Langmuir adsorption behavior, where both XGs probably decorate the cellulose surfaces as a monolayer. The adsorption maximum of the XGs reached around 180 mg/g on BC and only about three times as much on cotton linters. The adsorption was verified with colorimetric methods. The specific surface area of BC measured with XG and XG-GRGDS was about 200 m (2)/g and was almost three times less for cotton linters, 60 m (2)/g. The difference in the amounts of XGs adsorbed might be explained by the swollen network of bacterial cellulose and a more exposed and accessible bulk as compared to cotton linters. The nanocellulose material was modified homogeneously throughout the material, as seen by the z-scan in confocal microscopy. Moreover, the modification in the water phase, in comparison with organic solvents, was clearly advantageous for preserving the morphology, as observed with SEM. The modification slightly increased the wettability, which might explain the decrease in or undetectable adsorption of adhesive protein shown by QCM-D. Initial cell studies showed that adhesion of human endothelial cells is enhanced when the BC hydrogel is modified with XG-GRGDS. QCM-D studies further revealed that the cell enhancement is due to the presence of the RGD epitope on XG and not to a nonspecific adsorption of fibronectin from cell culture medium. Optimization and proliferation studies of human endothelial cells onto bacterial cellulose modified with XG-GRGDS are currently being carried out at the Vascular Engineering Center, Sahlgrenska University Hospital, Gothenburg.
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| 49. |
- Bolivar, Juan M, et al.
(author)
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Coating of soluble and immobilized enzymes with ionic polymers : full stabilization of the quaternary structure of multimeric enzymes
- 2009
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 10:4, s. 742-747
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Journal article (peer-reviewed)abstract
- This paper shows a simple and effective way to avoid the dissociation of multimeric enzymes by coating their surface with a large cationic polymer (e.g., polyethylenimine (PEI)) by ionic exchange. As model enzymes, glutamate dehydrogenase (GDH) from Thermus thermophilus and formate dehydrogenase (FDH) from Pseudomonas sp. were used. Both enzymes are very unstable at acidic pH values due to the rapid dissociation of their subunits (half-life of diluted preparations is few minutes at pH 4 and 25 degrees C). GDH and FDH were incubated in the presence of PEI yielding an enzyme-PEI composite with full activity. To stabilize the enzyme-polymer composite, a treatment with glutaraldehyde was required. These enzyme-PEI composites can be crosslinked with glutaraldehyde by immobilizing previously the composite onto a weak cationic exchanger. The soluble GDH-PEI composite was much more stable than unmodified GDH at pH 4 and 30 degrees C (retaining over 90% activity after 24 h incubation) with no effect of the GDH concentration in the inactivation course. The composite could be very strongly, but reversibly, adsorbed on cationic exchangers. Similarly, FDH could be treated with PEI and glutaraldehyde after adsorption on cationic exchangers, This permitted a stabilized FDH preparation. In this way, the coating of the enzymes surfaces with PEI is used as a simple and efficient strategy to prevent enzyme dissociation of multimeric enzymes. These composites can be used as a soluble catalyst or reversibly immobilized onto a cationic exchanger (e.g., CM-agarose).
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| 50. |
- Bosmans, Toon, 1988, et al.
(author)
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Assembly of Debranched Xylan from Solution and on Nanocellulosic Surfaces
- 2014
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 15:3, s. 924-930
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Journal article (peer-reviewed)abstract
- This study focused on the assembly characteristics of debranched xylan onto cellulose surfaces. A rye arabinoxylan polymer with an initial arabinose/xylose ratio of 0.53 was debranched with an oxalic acid treatment as a function of time. The resulting samples contained reduced arabinose/xylose ratios significantly affecting the molecular architecture and solution behavior of the biopolymer. With this treatment, an almost linear xylan with arabinose DS of only 0.04 was obtained. The removal of arabinose units resulted in the self-assembly of the debranched polymer in water into stable nanoparticle aggregates with a size around 300 nm with a gradual increase in crystallinity of the isolated xylan. Using quartz crystal microbalance with dissipation monitoring, the adsorption of xylan onto model cellulose surfaces was quantified. Compared to the nonmodified xylan, the adsorption of debranched xylan increased from 0.6 to 5.5 mg m(-2). Additionally, adsorption kinetics suggest that the nanoparticles rapidly adsorbed to the cellulose surfaces compared to the arabinoxylan. In summary, a control of the molecular structure of xylan influences its ability to form a new class of polysaccharide nanoparticles in aqueous suspensions and its interaction with nanocellulose surfaces.
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