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Oxidized Cladophora nanocellulose derivatives: Functionalization towards biocompatible materials
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials. (Nanoteknologi och funktionella material)ORCID iD: 0000-0003-2546-7224
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nanocellulose is a promising candidate for biomedical applications because of its enhanced mechanical properties, increased surface area and greater porosity compared to bulk cellulose.

This thesis investigates the functionalization of Cladophora nanocellulose and evaluates the influence of these modifications on physicochemical properties and biocompatibility of the material.

An electrochemically assisted TEMPO-mediated oxidation setup produced cellulose materials with varying degrees of carboxyl groups. This approach allowed control of the charge applied during the process and adjustment of the carboxylation. Carboxylated nanocellulose membranes had smaller surface area and total pore volume and a more compact structure than the membranes of the unmodified material. Moreover, the introduction of carboxyl groups resulted in membranes with an aligned fiber pattern; the alignment and aggregation of the fibers tended to increase with higher degrees of oxidation.

Cytocompatibility studies using fibroblasts and osteoblastic cells have shown that the bioinert Cladophora nanocellulose membranes can be rendered bioactive by the introduction of carboxyl groups. Nevertheless, at least 260 µmol g-1 carboxyl groups are required to obtain nanocellulose membranes that promote cell adhesion and spreading comparable to those observed when cells are cultured on tissue culture material.

In parallel, a periodate oxidation produced 10-20 µm 2,3-dialdehyde cellulose beads with very smooth and compact surfaces. This material was sulfonated up to 50% of the aldehyde groups, resulting in charged, porous structures that maintained the spherical shape. The mesoporous assembly could be tailored by altering the degree of sulfonation, which also produced variations in surface charge, ζ-potential, specific density, surface area and thermal stability.

Because the physicochemical properties make these sulfonated beads potential candidates for immunosorption and blood-related applications, they were further characterized regarding hemocompatibility. In vitro studies showed that both sulfonated beads and unmodified Cladophora nanocellulose did not present hemolytic activity. The pro-coagulant activity of the sulfonated beads was significantly lower than that of the unmodified nanocellulose; however, the material’s modifications did not diminish the activation of the complement system.

The results presented in this thesis show that it is possible to tailor the biocompatibility of Cladophora nanocellulose by introducing chemical modifications to its structure and by carefully tuning its physicochemical properties.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. , p. 75
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1649
Keywords [en]
Cladophora nanocellulose, TEMPO oxidation, periodate oxidation, sulfonation, cellulose beads, surface properties, biomaterials, cell studies, hemocompatibility
National Category
Nano Technology
Identifiers
URN: urn:nbn:se:uu:diva-346212ISBN: 978-91-513-0280-5 (print)OAI: oai:DiVA.org:uu-346212DiVA, id: diva2:1190839
Public defence
2018-05-09, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:30 (English)
Opponent
Supervisors
Available from: 2018-04-17 Created: 2018-03-15 Last updated: 2018-10-08
List of papers
1. Transition from bioinert to bioactive material by tailoring the biological cell response to carboxylated nanocellulose
Open this publication in new window or tab >>Transition from bioinert to bioactive material by tailoring the biological cell response to carboxylated nanocellulose
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2016 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 17, no 3, p. 1224-1233Article in journal (Refereed) Published
Abstract [en]

This work presents an insight into the relationship between cell response and physicochemical properties of Cladophora cellulose (CC) by investigating the effect of CC functional group density on the response of model cell lines. CC was carboxylated by electrochemical TEMPO-mediated oxidation. By varying the amount of charge passed through the electrolysis setup, CC materials with different degrees of oxidation were obtained. The effect of carboxyl group density on the material’s physicochemical properties was investigated together with the response of human dermal fibroblasts (hDF) and human osteoblastic cells (Saos-2) to the carboxylated CC films. The introduction of carboxyl groups resulted in CC films with decreased specific surface area and smaller total pore volume compared with the unmodified CC (u-CC). While u-CC films presented a porous network of randomly oriented fibers, a compact and aligned fiber pattern was depicted for the carboxylated-CC films. The decrease in surface area and total pore volume, and the orientation and aggregation of the fibers tended to augment parallel to the increase in the carboxyl group density. hDF and Saos-2 cells presented poor cell adhesion and spreading on u-CC, which gradually increased for the carboxylated CC as the degree of oxidation increased. It was found that a threshold value in carboxyl group density needs be reached to obtain a carboxylated-CC film with cytocompatibility comparable to commercial tissue culture material. Hence, this study demonstrates that a normally bioinert nanomaterial can be rendered bioactive by carefully tuning the density of charged groups on the material surface, a finding that not only may contribute to the fundamental understanding of biointerface phenomena, but also to the development of bioinert/bioactive materials.

National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-267300 (URN)10.1021/acs.biomac.6b00053 (DOI)000372391800056 ()
Funder
Swedish Research Council FormasStiftelsen Olle Engkvist Byggmästare
Available from: 2015-11-19 Created: 2015-11-19 Last updated: 2018-03-15Bibliographically approved
2. Sulfonated Nanocellulose Beads as Potential Immunosorbents
Open this publication in new window or tab >>Sulfonated Nanocellulose Beads as Potential Immunosorbents
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2018 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 28, no 3, p. 1899-1910Article in journal (Refereed) Published
Abstract [en]

Herein 2,3-dialdehyde cellulose beads prepared from Cladophora green algae nanocellulose were sulfonated and characterized by FTIR, conductometric titration, elemental analysis, SEM, ζ-potential, nitrogen adsorption–desorption and laser diffraction, aiming for its application as a potential immunosorbent material. Porous beads were prepared at mild reaction conditions in water and were chemically modified by sulfonation and reduction. The obtained 15 µm sized sulfonated beads were found to be highly charged and to have a high surface area of ~ 100 m2 g−1 and pore sizes between 20 and 60 nm, adequate for usage as immunosorbents. After reduction of remaining aldehyde groups, the beads could be classified as non-cytotoxic in indirect toxicity studies with human dermal fibroblasts as a first screening of their biocompatibility. The observed properties make the sulfonated cellulose beads interesting for further development as matrix material in immunosorbent devices.

Keywords
Periodate oxidation Dialdehyde cellulose, Surface group density, Sulfonated beads, Cytotoxicity
National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-346207 (URN)10.1007/s10570-018-1661-2 (DOI)000427379200027 ()
Funder
Knut and Alice Wallenberg Foundation
Available from: 2018-03-15 Created: 2018-03-15 Last updated: 2018-05-18Bibliographically approved
3. Spectroscopic and physicochemical characterization of sulfonated Cladophora cellulose beads
Open this publication in new window or tab >>Spectroscopic and physicochemical characterization of sulfonated Cladophora cellulose beads
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2018 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, no 37, p. 11121-11125Article in journal (Refereed) Published
Abstract [en]

The work presents a full physicochemical characterization of sulfonated cellulose beads prepared from Cladophora nanocellulose intended for use in biological systems. 2,3-Dialdehyde cellulose (DAC) beads were sulfonated, and transformation of up to 50% of the aldehyde groups was achieved, resulting in highly charged and porous materials compared to the compact surface of the DAC beads. The porosity could be tailored by adjusting the degree of sulfonation, and a subsequent reduction of the aldehyde groups to hydroxyl groups maintained the bead structure without considerable alteration of the surface properties. The thermal stability of the DAC beads was significantly increased with the sulfonation and reduction reactions. Raman spectroscopy also showed to be a useful technique for the characterization of sulfonated cellulose materials.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
National Category
Physical Chemistry Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-346211 (URN)10.1021/acs.langmuir.8b01704 (DOI)000445440200035 ()30169040 (PubMedID)
Available from: 2018-03-15 Created: 2018-03-15 Last updated: 2018-10-19Bibliographically approved
4. Blood Compatibility of Sulfonated Cladophora Nanocellulose Beads
Open this publication in new window or tab >>Blood Compatibility of Sulfonated Cladophora Nanocellulose Beads
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2018 (English)In: Molecules, ISSN 1420-3049, E-ISSN 1420-3049, Vol. 23, no 3, article id 601Article in journal (Refereed) Published
Abstract [en]

Sulfonated cellulose beads were prepared by oxidation of Cladophora nanocellulose to 2,3-dialdehyde cellulose followed by sulfonation using bisulfite. The physicochemical properties of the sulfonated beads, i.e., high surface area, high degree of oxidation, spherical shape, and the possibility of tailoring the porosity, make them interesting candidates for the development of immunosorbent platforms, including their application in extracorporeal blood treatments. A desired property for materials used in such applications is blood compatibility; therefore in the present work, we investigate the hemocompatibility of the sulfonated cellulose beads using an in vitro whole blood model. Complement system activation (C3a and sC5b-9 levels), coagulation activation (thrombin-antithrombin (TAT) levels) and hemolysis were evaluated after whole blood contact with the sulfonated beads and the results were compared with the values obtained with the unmodified Cladophora nanocellulose. Results showed that neither of the cellulosic materials presented hemolytic activity. A marked decrease in TAT levels was observed after blood contact with the sulfonated beads, compared with Cladophora nanocellulose. However, the chemical modification did not promote an improvement in Cladophora nanocellulose hemocompatibility in terms of complement system activation. Even though the sulfonated beads presented a significant reduction in pro-coagulant activity compared with the unmodified material, further modification strategies need to be investigated to control the complement activation by the cellulosic materials.

Keywords
sulfonated beads; Cladophora nanocellulose; hemocompatibility; coagulation; complement system
National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-346209 (URN)10.3390/molecules23030601 (DOI)000428514100092 ()
Funder
Knut and Alice Wallenberg Foundation
Available from: 2018-03-15 Created: 2018-03-15 Last updated: 2019-06-28Bibliographically approved

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