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Structural and Electrochemical Properties of Functionalized Nanocellulose Materials and Their Biocompatibility
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials. (Nanoteknologi & Funktionella Material)
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nanocellulose has received considerable interest during the last decade because it is renewable and biodegradable, and has excellent mechanical properties, nanoscale dimensions and wide functionalization possibilities. It is considered to be a unique and versatile platform on which new functional materials can be based.

This thesis focuses on nanocellulose from wood (NFC) and from Cladophora algae (CNC), functionalized with surface charges or coated with the conducting polymer polypyrrole (PPy), aiming to study the influence of synthesis processes on structural and electrochemical properties of such materials and assess their biocompatibility.

The most important results of the work demonstrated that 1) CNC was oxidized to the same extent using electrochemical TEMPO-mediated oxidation as with conventional TEMPO processes, which may facilitate easier reuse of the reaction medium; 2) NFC and CNC films with or without surface charges were non-cytotoxic as assessed by indirect in vitro testing. Anionic TEMPO-CNC films promoted fibroblast adhesion and proliferation in direct in vitro cytocompatibility testing, possibly due to its aligned fibril structure; 3) Rinsing of PPy-coated nanocellulose fibrils, which after drying into free-standing porous composites are applicable for energy storage and electrochemically controlled ion extraction, significantly degraded the PPy coating, unless acidic rinsing was employed. Only minor degradation was observed during long-term ambient storage; 4) Variations in the drying method as well as type and amount of nanocellulose offered ways of tailoring the porosities of nanocellulose/PPy composites between 30% and 98%, with increments of ~10%. Supercritical CO2-drying generated composites with the largest specific surface area yet reported for nanocellulose/conducting polymer composites (246 m2/g). The electrochemical oxidation rate was found to be controlled by the composite porosity; 5) In blood compatibility assessments for potential hemodialysis applications, heparinization of CNC/PPy composites was required to obtain thrombogenic properties comparable to commercial hemodialysis membranes. The pro-inflammatory characteristics of non-heparinized and heparinized composites were, to some extent, superior to commercial membranes. The heparin coating did not affect the solute extraction capacity of the composite.

The presented results are deemed to be useful for tuning the properties of systems based on the studied materials in e.g. energy storage, ion exchange and biomaterial applications.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. , p. 73
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1109
Keyword [en]
Nanocellulose, nanofibrillated cellulose, Cladophora cellulose, polypyrrole, TEMPO-mediated oxidation, composite, porosity, cytocompatibility, blood compatibility
National Category
Nano Technology Materials Engineering Physical Sciences Chemical Sciences
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
URN: urn:nbn:se:uu:diva-215090ISBN: 978-91-554-8842-0 (print)OAI: oai:DiVA.org:uu-215090DiVA, id: diva2:686055
Public defence
2014-02-25, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:30 (English)
Opponent
Supervisors
Available from: 2014-02-03 Created: 2014-01-10 Last updated: 2014-09-11
List of papers
1. Electrochemical TEMPO-mediated Oxidation of Highly Crystalline Nanocellulose in Water
Open this publication in new window or tab >>Electrochemical TEMPO-mediated Oxidation of Highly Crystalline Nanocellulose in Water
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2014 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, p. 52289-52298Article in journal (Refereed) Published
National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-215088 (URN)
Available from: 2014-01-10 Created: 2014-01-10 Last updated: 2017-12-06
2. Translational study between structure and biological response of nanocellulose from wood and green algae
Open this publication in new window or tab >>Translational study between structure and biological response of nanocellulose from wood and green algae
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2014 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 6, p. 2892-2903Article in journal (Refereed) Published
Abstract [en]

The influence of nanostructure on the cytocompatibility of cellulose films is analyzed providing insight into how physicochemical properties of surface modified microfibrillated cellulose (MFC) and Cladophora nanocellulose (CC) affect the materials cytocompatibility. CC is modified through TEMPO-mediated oxidation and glycidyltrimethylammonium chloride (EPTMAC) condensation to obtain anionic and cationic nanocellulose samples respectively, while anionic and cationic MFC samples are obtained by carboxymethylation and EPTMAC condensation respectively. Films of unmodified, anionic and cationic MFC and CC are prepared by vacuum filtration and characterized in terms of specific surface area, pore size distribution, degree of crystallinity, surface charge and water content. Human dermal fibroblasts are exposed to culture medium extracts of the films in an indirect contact cytotoxicity test. Moreover, cell adhesion and viability are evaluated in a direct contact assay and the effects of the physicochemical properties on cell behavior are discussed. In the indirect cytotoxicity test no toxic leachables are detected, evidencing that the CC and MFC materials are non-cytotoxic, independently ofthe chemical treatment that they have been subjected to. The direct contact tests show that carboxymethylated-MFC presents a more cytocompatible profile than unmodified and trimethylammonium-MFC. TEMPO-CC promotes fibroblast adhesion and presents cell viability comparable to the results obtained with the tissue culture material Thermanox. We hypothesize that the distinct aligned nanofiber structure present in the TEMPO-CC films is responsible for the improved cell adhesion. Thus, by controlling the surface properties of cellulose nanofibers, such as chemistry, charge, and orientation, cell adhesion properties can be promoted.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2014
National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-211744 (URN)10.1039/C3RA45553J (DOI)000329037100044 ()
Available from: 2013-11-30 Created: 2013-11-30 Last updated: 2017-12-06Bibliographically approved
3. A Comparative Study of the Effects of Rinsing and Aging of Polypyrrole/Nanocellulose Composites on Their Electrochemical Properties
Open this publication in new window or tab >>A Comparative Study of the Effects of Rinsing and Aging of Polypyrrole/Nanocellulose Composites on Their Electrochemical Properties
2013 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 117, no 14, p. 3900-3910Article in journal (Refereed) Published
Abstract [en]

The effects of polymerization conditions, rinsing, and storage on composites composed of polypyrrole (PPy) and Cladophora nanocellulose in terms of purity, chemical composition, conductivity, and electroactivity were investigated using conductivity measurements, cyclic voltammetry, FTIR-ATR, XPS, and ICP-AES. A clear correlation between rinsing volume and PPy degradation was found using water- or NaCl-rinsing solutions as evidenced by conductivity and electroactivity losses. It was further found, through FTIR-ATR as well as XPS-measurements, that this degradation was caused by incorporation of hydroxyl groups in the PPy-layer. The extent of degradation correlated with a shift in the FTIR-ATR peak around 1300 cm(-1), showing that FTIR-ATR may be used as a quick diagnostic tool to evaluate the extent of degradation. By the use of acidic rinsing solution, this degradation effect was eliminated and resulted in superior samples in terms of both conductivity and electroactivity and also in a more efficient removal of reactants. Upon ambient storage, over a period of 200 days, a gradual decrease in conductivity was found for initially highly conductive samples. The electroactivity, on the other hand, was relatively unaffected by storage, showing that conductivity measurements alone are ineffective to determine the degree of polymer degradation if the water content is not controlled. Also, FTIR-ATR measurements indicated that the oxidation state did not change to any large extent upon storage and that only minor degradation of PPy occurred. The results presented herein thus offer valuable guidelines on how to develop simple and reliable postsynthesis treatments of conducting polymer paper composites with performance fulfilling requirements on stability, electroactivity, and purity in applications such as environmentally friendly energy storage devices and biomedical applications.

National Category
Natural Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-200350 (URN)10.1021/jp3125582 (DOI)000317552700022 ()
Available from: 2013-05-28 Created: 2013-05-27 Last updated: 2017-12-06
4. Electroactive nanofibrillated cellulose aerogel composites with tunable structural and electrochemical properties
Open this publication in new window or tab >>Electroactive nanofibrillated cellulose aerogel composites with tunable structural and electrochemical properties
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2012 (English)In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, no 36, p. 19014-19024Article in journal (Refereed) Published
National Category
Nano Technology Inorganic Chemistry
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials; Chemistry with specialization in Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-182555 (URN)10.1039/C2JM33975G (DOI)000307790300046 ()
Available from: 2012-10-11 Created: 2012-10-11 Last updated: 2017-12-07
5. Tailoring porosities and electrochemical properties of composites composed of microfibrillated cellulose and polypyrrole
Open this publication in new window or tab >>Tailoring porosities and electrochemical properties of composites composed of microfibrillated cellulose and polypyrrole
2014 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 17, p. 8489-8497Article in journal (Refereed) Published
Abstract [en]

Composites of polypyrrole and nanocellulose (PPy/nanocellulose) have a high potential as electrodes in energy-storage devices and as membranes for electrochemically controlled ion-exchange systems. In the present work, it is demonstrated that such composites with 42-72% porosity can be produced by using microfibrillated cellulose (MFC) prepared through enzymatic pretreatment or carboxymethylation, or by using different amounts of MFC in the composite synthesis. Together with previous work, this shows that the porosity of PPy/nanocellulose composites can be tailored from 30 to 98% with increments of similar to 10%. Employing the full porosity range of the composites, it is demonstrated that the electrochemical oxidation rate of the materials depends on their porosity due to limitations in the counter ion diffusion process. By tailoring the porosities of PPy/nanocellulose composites, the electrochemical properties can consequently be controlled. The latter provides new possibilities for the manufacturing of electrochemically controlled ion-extraction and energy storage devices with optimized volumetric energy and power densities.

National Category
Natural Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-221065 (URN)10.1039/c3ra47588c (DOI)000330800300012 ()
Available from: 2014-03-26 Created: 2014-03-25 Last updated: 2017-12-05
6. Haemocompatibility and ion exchange capability of nanocellulose polypyrrole membranes intended for blood purification
Open this publication in new window or tab >>Haemocompatibility and ion exchange capability of nanocellulose polypyrrole membranes intended for blood purification
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2012 (English)In: Journal of the Royal Society Interface, ISSN 1742-5689, E-ISSN 1742-5662, Vol. 9, no 73, p. 1943-1955Article in journal (Refereed) Published
Abstract [en]

Composites of nanocellulose and the conductive polymer polypyrrole (PPy) are presented as candidates for a new generation of haemodialysis membranes. The composites may combine active ion exchange with passive ultrafiltration, and the large surface area (about 80 m2 g−1) could potentially provide compact dialysers. Herein, the haemocompatibility of the novel membranes and the feasibility of effectively removing small uraemic toxins by potential-controlled ion exchange were studied. The thrombogenic properties of the composites were improved by applying a stable heparin coating. In terms of platelet adhesion and thrombin generation, the composites were comparable with haemocompatible polymer polysulphone, and regarding complement activation, the composites were more biocompatible than commercially available membranes. It was possible to extract phosphate and oxalate ions from solutions with physiological pH and the same tonicity as that of the blood. The exchange capacity of the materials was found to be 600 ± 26 and 706 ± 31 μmol g−1 in a 0.1 M solution (pH 7.4) and in an isotonic solution of phosphate, respectively. The corresponding values with oxalate were 523 ± 5 in a 0.1 M solution (pH 7.4) and 610 ± 1 μmol g−1 in an isotonic solution. The heparinized PPy–cellulose composite is consequently a promising haemodialysis material, with respect to both potential-controlled extraction of small uraemic toxins and haemocompatibility.

National Category
Nano Technology Medical and Health Sciences
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-169218 (URN)10.1098/rsif.2012.0019 (DOI)000305810200023 ()22298813 (PubMedID)
Available from: 2012-02-24 Created: 2012-02-24 Last updated: 2017-12-07Bibliographically approved

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