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  • 1.
    Aarstad, Olav
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Pedersen, Ina Sander
    NTNU Norwegian University of Science and Technology, Norway.
    Björnöy, Sindre H.
    NTNU Norwegian University of Science and Technology, Norway.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Strand, Berit L.
    NTNU Norwegian University of Science and Technology, Norway.
    Mechanical properties of composite hydrogels of alginate and cellulose nanofibrils2017In: Polymers, ISSN 2073-4360, E-ISSN 2073-4360, Vol. 9, no 8, article id 378Article in journal (Refereed)
    Abstract [en]

    Alginate and cellulose nanofibrils (CNF) are attractive materials for tissue engineering and regenerative medicine. CNF gels are generally weaker and more brittle than alginate gels, while alginate gels are elastic and have high rupture strength. Alginate properties depend on their guluronan and mannuronan content and their sequence pattern and molecular weight. Likewise, CNF exists in various qualities with properties depending on, e.g., morphology and charge density. In this study combinations of three types of alginate with different composition and two types of CNF with different charge and degree of fibrillation have been studied. Assessments of the composite gels revealed that attractive properties like high rupture strength, high compressibility, high gel rigidity at small deformations (Young’s modulus), and low syneresis was obtained compared to the pure gels. The effects varied with relative amounts of CNF and alginate, alginate type, and CNF quality. The largest effects were obtained by combining oxidized CNF with the alginates. Hence, by combining the two biopolymers in composite gels, it is possible to tune the rupture strength, Young’s modulus, syneresis, as well as stability in physiological saline solution, which are all important properties for the use as scaffolds in tissue engineering.

  • 2.
    Chinga-Carrasco, Gary
    et al.
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Kirsebom, H.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Designing nanocellulose qualities for wound dressings2013Conference paper (Refereed)
  • 3.
    Chinga-Carrasco, Gary
    et al.
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Powell, L.C
    Cardiff University School of Dentistry, UK; Swansea University, UK.
    Khan, S
    Cardiff University, UK.
    Hill, K.E
    Cardiff University UK.
    Thomas, D.W
    Cardiff University, UK.
    Wood nanocellulose: Characterization and potential application as barrier against wound bacteria2014Conference paper (Refereed)
    Abstract [en]

    Wood nanocellulose is a novel biomaterial for wound dressing applications. Wood nanocellulose was produced from never-dried P. radiata pulp fibres. The applied pre-treatment was 2,2,6,6-tetramethylpiperidinyl-1-oxyl  (TEMPO) mediated oxidation. To characterise bacterial growth, P. aeruginosa PAO1 biofilms were grown in Mueller Hinton broth on air-dried films. Various microscopy techniques, including atomic force microscopy (AFM), confocal laser scanning microscopy (CLSM) and field-emission scanning electron microscopy (FESEM), were applied to characterise the nanocellulose material and the bacterial-nanocellulose interactions.   Multiscale assessments, including FESEM and AFM, revealed the effective fibrillation of the fibre wall structure, yielding nanofibrils with diameters less than 20 nm and lengths in the micrometre-scale. Importantly, we have demonstrated that the growth of PAO1 was inhibited in the presence of the nanocellulose suspensions when compared to the control. Additionally, SEM imaging revealed distinct clusters of PAO1 cells growing on the surfaces of nanocellulose films. This work highlights the potential usefulness of novel nanocellulose materials in wound dressings with optimized characteristics.

  • 4.
    Chinga-Carrasco, Gary
    et al.
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Powell, L.C
    Cardiff University School of Dentistry, UK; Swansea University, UK.
    Nordli, H.R
    NTNU Norwegian University of Science and Technology, Norway.
    Khan, S
    Cardiff University, UK.
    Hill, K.E
    Cardiff University, UK.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Thomas, D.W
    Cardiff University, UK.
    Nanocellulose from wood as a biomaterial for biomedical applications2014Conference paper (Refereed)
    Abstract [en]

    During the last decades major efforts have been made to produce nanocellulose from wood, where the cellulose fibres are disintegrated into individualized nanofibrils with diameters < 20 nm and lengths in the micrometre scale. Production procedures include various pre-treatments, which yield nanocelluloses with varying chemical and structural properties. One important area of research is nanocellulose as a biomaterial with potential applications within the health sector. As an example, the superior mechanical properties, good moisture retention capability and the ability to form elastic macro-porous structures are advantageous properties for utilizing nanocellulose substrates for wound dressings. However, the utilization of nanocellulose as a substrate for wound dressings requires a thorough assessment of the biocompatibility of the material.  In this respect, it has been demonstrated in-vitro that nanocellulose does not exert acute toxic phenomena on fibroblast cells. However, in addition to in-vitro cytotoxicity testing, in-vivo testing of nanocellulose and the ability of nanocellulose to resist bacterial colonization need a closer attention. This presentation will give an overview of the current research on nanocellulose as a biomaterial for wound dressing applications, considering the morphology of nanocellulose structures, mechanical properties, moisture absorption, cytotoxicity tests and nanocellulose-bacteria interactions.

  • 5.
    Jack, Alison A.
    et al.
    Cardiff University School of Dentistry, UK.
    Nordli, Henriette R.
    NTNU, Norway.
    Powell, Lydia C.
    Cardiff University School of Dentistry, UK.
    Powell, Kate A.
    Cardiff University School of Dentistry, UK.
    Kishnani, Himanshu
    Cardiff University School of Dentistry, UK.
    Johnsen, Per Olav
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Pukstad, Brita
    Trondheim University Hospital, Norway.
    Thomas, David W.
    Cardiff University School of Dentistry, UK.
    Chinga-Carrasco, Gary
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Hill, Katja E.
    Cardiff University School of Dentistry, UK.
    The interaction of wood nanocellulose dressings and the wound pathogen P. aeruginosa2017In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 157, p. 1955-1962Article in journal (Refereed)
    Abstract [en]

    Chronic wounds pose an increasingly significant worldwide economic burden (over £1 billion per annum in the UK alone). With the escalation in global obesity and diabetes, chronic wounds will increasingly be a significant cause of morbidity and mortality. Cellulose nanofibrils (CNF) are highly versatile and can be tailored with specific physical properties to produce an assortment of three-dimensional structures (hydrogels, aerogels or films), for subsequent utilization as wound dressing materials. Growth curves using CNF (diameter &lt;20 nm) in suspension demonstrated an interesting dose-dependent inhibition of bacterial growth. In addition, analysis of biofilm formation (Pseudomonas aeruginosa PAO1) on nanocellulose aerogels (20 g/m2) revealed significantly less biofilm biomass with decreasing aerogel porosity and surface roughness. Importantly, virulence factor production by P. aeruginosa in the presence of nanocellulose materials, quantified for the first time, was unaffected (p &gt; 0.05) over 24 h. These data demonstrate the potential of nanocellulose materials in the development of novel dressings that may afford significant clinical potential.

  • 6.
    Karazisis, Dimitrios
    et al.
    University of Gothenburg, Sweden.
    Ballo, Ahmed M.
    University of Gothenburg, Sweden; University of British Columbia, Canada.
    Petronis, Sarunas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Medicinteknik. University of Gothenburg, Sweden.
    Agheli, Hossein
    University of Gothenburg, Sweden.
    Emanuelsson, Lena
    University of Gothenburg, Sweden.
    Thomsen, Peter
    University of Gothenburg, Sweden.
    Omar, Omar
    University of Gothenburg, Sweden.
    The role of well-defined nanotopography of titanium implants on osseointegration: Cellular and molecular events in vivo2016In: International Journal of Nanomedicine, ISSN 1176-9114, E-ISSN 1178-2013, Vol. 11, p. 1367-1382Article in journal (Refereed)
    Abstract [en]

    Purpose: Mechanisms governing the cellular interactions with well-defined nanotopography are not well described in vivo. This is partly due to the difficulty in isolating a particular effect of nanotopography from other surface properties. This study employed colloidal lithography for nanofabrication on titanium implants in combination with an in vivo sampling procedure and different analytical techniques. The aim was to elucidate the effect of well-defined nanotopography on the molecular, cellular, and structural events of osseointegration. Materials and methods: Titanium implants were nanopatterned (Nano) with semispherical protrusions using colloidal lithography. Implants, with and without nanotopography, were implanted in rat tibia and retrieved after 3, 6, and 28 days. Retrieved implants were evaluated using quantitative polymerase chain reaction, histology, immunohistochemistry, and energy dispersive X-ray spectroscopy (EDS). Results: Surface characterization showed that the nanotopography was well defined in terms of shape (semispherical), size (79±6 nm), and distribution (31±2 particles/μm2). EDS showed similar levels of titanium, oxygen, and carbon for test and control implants, confirming similar chemistry. The molecular analysis of the retrieved implants revealed that the expression levels of the inflammatory cytokine, TNF-α, and the osteoclastic marker, CatK, were reduced in cells adherent to the Nano implants. This was consistent with the observation of less CD163-positive macrophages in the tissue surrounding the Nano implant. Furthermore, periostin immunostaining was frequently detected around the Nano implant, indicating higher osteogenic activity. This was supported by the EDS analysis of the retrieved implants showing higher content of calcium and phosphate on the Nano implants. Conclusion: The results show that Nano implants elicit less periimplant macrophage infiltration and downregulate the early expression of inflammatory (TNF-α) and osteoclastic (CatK) genes. Immunostaining and elemental analyses show higher osteogenic activity at the Nano implant. It is concluded that an implant with the present range of well-defined nanocues attenuates the inflammatory response while enhancing mineralization during osseointegration.

  • 7.
    Karazisis, Dimitrios
    et al.
    Sahlgrenska Academy, Sweden; University of Gothenburg, Sweden; BIOMATCELL, Sweden.
    Petronis, Sarunas
    RISE - Research Institutes of Sweden, Bioscience and Materials, Chemistry and Materials. BIOMATCELL, Sweden.
    Agheli, Hossein
    Sahlgrenska Academy, Sweden; University of Gothenburg, Sweden; BIOMATCELL, Sweden.
    Emanuelsson, Lena
    Sahlgrenska Academy, Sweden; University of Gothenburg, Sweden; BIOMATCELL, Sweden.
    Norlindh, Birgitta
    Sahlgrenska Academy, Sweden; University of Gothenburg, Sweden; BIOMATCELL, Sweden.
    Johansson, Anna
    Sahlgrenska Academy, Sweden; University of Gothenburg, Sweden; BIOMATCELL, Sweden.
    Rasmusson, Lars
    RISE - Research Institutes of Sweden, ICT, SICS.
    Thomsen, Peter
    Sahlgrenska Academy, Sweden; University of Gothenburg, Sweden; BIOMATCELL, Sweden.
    Omar, Omar
    Sahlgrenska Academy, Sweden; University of Gothenburg, Sweden; BIOMATCELL, Sweden.
    The influence of controlled surface nanotopography on the early biological events of osseointegration.2017In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 53, p. 559-571Article in journal (Refereed)
    Abstract [en]

    The early cell and tissue interactions with nanopatterned titanium implants are insufficiently described in vivo. A limitation has been to transfer a pre-determined, well-controlled nanotopography to 3D titanium implants, without affecting other surface parameters, including surface microtopography and chemistry. This in vivo study aimed to investigate the early cellular and molecular events at the bone interface with screw-shaped titanium implants superimposed with controlled nanotopography. Polished and machined titanium implants were firstly patterned with 75-nm semispherical protrusions. Polished and machined implants without nano-patterns were designated as controls. Thereafter, all nanopatterned and control implants were sputter-coated with a 30nm titanium layer to unify the surface chemistry. The implants were inserted in rat tibiae and samples were harvested after 12h, 1d and 3d. In one group, the implants were unscrewed and the implant-adherent cells were analyzed using quantitative polymerase chain reaction. In another group, implants with surrounding bone were harvested en bloc for histology and immunohistochemistry. The results showed that nanotopography downregulated the expression of monocyte chemoattractant protein-1 (MCP-1), at 1d, and triggered the expression of osteocalcin (OC) at 3d. This was in parallel with a relatively lower number of recruited CD68-positive macrophages in the tissue surrounding the nanopatterned implants. Moreover, a higher proportion of newly formed osteoid and woven bone was found at the nanopatterned implants at 3d. It is concluded that nanotopography, per se, attenuates the inflammatory process and enhances the osteogenic response during the early phase of osseointegration. This nanotopography-induced effect appeared to be independent of the underlying microscale topography.

    STATEMENT OF SIGNIFICANCE: This study provides a first line of evidence that pre-determined nanopatterns on clinically relevant, screw-shaped, titanium implants can be recognized by cells in the complex in vivo environment. Until now, most of the knowledge relating to cell interactions with nanopatterned surfaces has been acquired from in vitro studies involving mostly two-dimensional nanopatterned surfaces of varying chemical composition. We have managed to superimpose pre-determined nanoscale topography on polished and micro-rough, screw-shaped, implants, without changes in the microscale topography or chemistry. This was achieved by colloidal lithography in combination with a thin titanium film coating on top of both nanopatterned and control implants. The early events of osseointegration were evaluated at the bone interface to these implants. The results revealed that nanotopography, as such, elicits downregulatory effects on the early recruitment and activity of inflammatory cells while enhancing osteogenic activity and woven bone formation.

  • 8.
    Kuna, V K
    et al.
    University of Gothenburg, Sweden.
    Padma, A M
    University of Gothenburg, Sweden.
    Håkansson, Joakim
    RISE - Research Institutes of Sweden, Bioscience and Materials, Chemistry and Materials.
    Nygren, J
    TATAA Biocenter, Sweden.
    Sjöback, R
    TATAA Biocenter, Sweden.
    Petronis, Sarunas
    RISE - Research Institutes of Sweden, Bioscience and Materials, Chemistry and Materials.
    Sumitran-Holgersson, S
    University of Gothenburg, Sweden.
    Significantly accelerated wound healing of full-thickness skin using a novel composite gel of porcine acellular dermal matrix and human peripheral blood cells2017In: Cell Transplantation, ISSN 0963-6897, E-ISSN 1555-3892, Vol. 26, no 2, p. 293-307Article in journal (Refereed)
    Abstract [en]

    Herein, we report the fabrication of a novel composite gel from decellularized gal-gal-knockout porcine skin and human peripheral blood mononuclear cells (hPBMC) for full-thickness skin wound healing. Decellularized skin extracellular matrix (ECM) powder was prepared via chemical treatment, freeze-drying and homogenization. The powder was mixed with culture medium containing hyaluronic acid to generate a pig skin gel (PSG). The effect of the gel in regeneration of full-thickness wound was studied in nude mice. We found significantly accelerated wound closure already on day 15 in animals treated with PSG only or PSG+hPBMC as compared to untreated and hyaluronic acid treated controls (p<0.05). Addition of the hPBMC to the gel resulted in marked increase of host blood vessels as well as the presence of human blood vessels. At day 25, histologically, the wounds in animals treated with PSG only or PSG+hPBMC were completely closed as compared to controls. Thus, the gel facilitated generation of new skin with well arranged epidermal cells and restored bilayer structure of the epidermis and dermis. These results suggest that porcine skin ECM gel together with human cells may be a novel and promising biomaterial for medical applications especially for patients with acute and chronic skin wounds.

  • 9.
    Lavelle, E
    et al.
    Trinity College, Ireland.
    Moran, L
    Trinity College, Ireland.
    Andersson, Mats
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation.
    The impact of chitosan acetylation pattern on inflammation and toxicity2018In: The 14th International Chitin and Chitosan Conference (14th ICCC): 12th Asia‐Pacific Chitin and Chitosan Symposium (12th APCCS), 2018Conference paper (Other academic)
    Abstract [en]

    The inherent properties of chitosan, being nontoxic, biodegradable and antimicrobial have attracted many scientists developing products for humans use in the fields of biomaterials and pharmaceuticals. Examples of such uses are as a carrier for vaccines and drugs, and as a scaffold for living cells. Many projects have failed due to unwanted side reactions, failure to meet technical specifications or to comply with the regulatory standards set by the medical authorities. There are several contradictions in the literature regarding the role chitosan plays in inducing inflammatory reactions. One common view is that chitosan possess anti-inflammatory properties but there are also examples indicating the opposite, that chitosan promotes inflammation. The origin of an inflammatory reaction is often difficult to tell, is it an effect of the chitosan itself or could it be attributed to remaining impurities in it, like endotoxins or protein residues? Purity and consistency in manufacturing are certainly two issues that need to be overcome. The role of chitosan in inflammatory processes is still not fully understood and further experiments with well characterized preparations are needed to reveal the underlying mechanisms.

    Technically chitosan can be divided in two categories based on their acetylation pattern, heterogeneously and homogeneously deacetylated chitosans.  Their different acetylation pattern follows on the processes used for their manufacturing. This means that depending on the manufacturing process two chitosans could have the same degree of deacetylation and molecular weight, be indistinguishable by 1H-NMR and still be structurally different.

    With a set of well characterized samples, representing heterogeneously and homogeneously deacetylated chitosans, we have investigated the effects of six different chitosans with respect to their impact on different inflammatory markers and cell toxicity. Our results show large differences between the two categories. The homogenously deacetylated chitosans are all poor inducers of inflammatory reactions and show very low toxicity whereas their heterogeneously deacetyleted cousins are significantly more toxic and seems to promote inflammatory reactions.

  • 10.
    Liu, Jun
    et al.
    Åbo Akademi University, Finland.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Cheng, Fang
    Åbo Akademi University, Finland; University of Turku, Finland.
    Xu, Wenyang
    Åbo Akademi University, Finland.
    Willför, Stefan
    Åbo Akademi University, Finland.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute. NTNU Norwegian University of Science and Technology, Norway.
    Xu, Chunlin
    Åbo Akademi University, Finland.
    Hemicellulose-reinforced nanocellulose hydrogels for wound healing application2016In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 5, p. 3129-3143Article in journal (Refereed)
    Abstract [en]

    Polysaccharides are finding an increasing number of applications in medical and pharmaceutical fields thanks to their biodegradability, biocompatibility, and in some cases bioactivity. Two approaches were applied to use hemicelluloses as crosslinkers to tune the structural and mechanical properties of nanofibrillated cellulose (NFC) hydrogel scaffolds, and thus to investigate the effect of these properties on the cellular behavior during wound healing application. Different types of hemicellulose (galactoglucomannan (GGM), xyloglucan (XG), and xylan) were introduced into the NFC network via pre-sorption (Method I) and in situ adsorption (Method II) to reinforce the NFC hydrogels. The charge density of the NFC, the incorporated hemicellulose type and amount, and the swelling time of the hydrogels were found to affect the pore structure, the mechanical strength, and thus the cells’ growth on the composite hydrogel scaffolds. The XG showed the highest adsorption capacity on the NFC, the highest reinforcement effect, and facilitated/promoted cell growth. The pre-sorbed XG in the low-charged NFC network with a lower weight ratio (NFC/XG-90:10) showed the highest efficacy in supporting the growth and proliferation of fibroblast cells (NIH 3T3). These all-polysaccharide composite hydrogels may work as promising scaffolds in wound healing applications to provide supporting networks and to promote cells adhesion, growth, and proliferation.

  • 11.
    Nilebäck, Linnea
    et al.
    KTH Royal Institute of Technology, Sweden.
    Hedin, Jesper
    RISE - Research Institutes of Sweden, Bioscience and Materials, Chemistry and Materials.
    Widhe, Mona
    KTH Royal Institute of Technology, Sweden.
    Floderus, Lotta S
    KTH Royal Institute of Technology, Sweden.
    Krona, Annika
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Bysell, Helena
    RISE - Research Institutes of Sweden, Bioscience and Materials, Chemistry and Materials.
    Hedhammar, My
    KTH Royal Institute of Technology, Sweden.
    Self-Assembly of Recombinant Silk as a Strategy for ChemicalFree Formation of Bioactive Coatings – a Real-Time Study2017In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 18, no 3, p. 846-854Article in journal (Refereed)
    Abstract [en]

    Functionalization of biomaterials with biologically active peptides can improve their performance after implantation. By genetic fusion to self-assembling proteins, the functional peptides can easily be presented on different physical formats. Herein, a chemical-free coating method based on self-assembly of the recombinant spider silk protein 4RepCT is described and used to prepare functional coatings on various biomaterial surfaces. The silk assembly was studied in real-time, revealing occurrence of continuous assembly of silk proteins onto surfaces and formation of nanofibrillar structures. The adsorbed amounts and viscoelastic properties were evaluated, and the coatings were shown to be stable against wash with hydrogen chloride, sodium hydroxide, and ethanol. Titanium, stainless steel, and hydroxyapatite were coated with silk fused to an antimicrobial peptide or a motif from fibronectin. Human primary cells cultured on the functional silk coatings show good cell viability and proliferation, implying potential to improve implant performance and acceptance by the body.

  • 12.
    Nordli, H.R
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Rokstad, A.M
    NTNU Norwegian University of Science and Technology, Norway.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Pukstad, B
    NTNU Norwegian University of Science and Technology, Norway; Trondheim University Hospital, Norway.
    Immunogenic properties of TEMPO-treated wood nanocellulose2014Conference paper (Refereed)
    Abstract [en]

    Bacterial nanocellulose (BNC) has been shown to be a good candidate in wound healing applications. However, there exists to date no cost efficient mass production of BNC. On the other side, wood nanocellulose (WNC) can be produced in large-scale and has also been suggested as a potential substrate for wound dressings. In WNC the cellulose fibers are disintegrated into individualized nanofibrils with typical diameters < 20 nm. Chemical pretreatment such as TEMPO-mediated oxidation yields a homogenous nanofibril morphology and modifies the surface chemistry of cellulose by introducing carboxyl groups and a small amount of aldehyde groups. A difference between BNC and WNC is that the last one usually consists of hemicellulose and small amounts of lignin, in addition to cellulose. Recently, we have demonstrated that WNC is not cytotoxic to 3T3-cells (mouse fibroblasts). However, to properly assess the properties of WNC for wound healing it is necessary to measure the cytotoxicity towards human skin cells, i.e. keratinocytes and fibroblasts, which is performed in this study. Additionally, using the lepirudin whole blood model the effect a material has on the activation of the complement system and the coagulation pathway can be studied. In order to use this model it is crucial to have a material which is free from bacterial composites, such as lipopolysaccharides (LPS). Importantly, we have in this work developed a new protocol for producing ultrapure nanocellulose with LPS concentration below 100 EU/g. This presentation will give an overview of recent results within the testing of the cytotoxic and immunogenic properties of WNC, which is important to verify for advanced wound healing applications.

  • 13.
    Powell, Lydia C.
    et al.
    Cardiff University, UK; Swansea University, UK.
    Khan, Saira
    Cardiff University, UK.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Wright, Chris J.
    Swansea University, UK.
    Hill, Katja E.
    Cardiff University, UK.
    Thomas, David W.
    Cardiff University, UK.
    An investigation of Pseudomonas aeruginosa biofilm growth on novel nanocellulose fibre dressings2016In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 137, p. 191-197Article in journal (Refereed)
    Abstract [en]

    Nanocellulose from wood is a novel biomaterial, which is highly fibrillated at the nanoscale. This affords the material a number of advantages, including self-assembly, biodegradability and the ability to absorb and retain moisture, which highlights its potential usefulness in clinical wound-dressing applications. In these in vitro studies, the wound pathogen Pseudomonas aeruginosa PAO1 was used to assess the ability of two nanocellulose materials to impair bacterial growth (&lt;48 h). The two nanocelluloses had a relatively small fraction of residual fibres (&lt;4%) and thus a large fraction of nanofibrils (widths &lt;20 nm). Scanning electron microscopy and confocal laser scanning microscopy imaging demonstrated impaired biofilm growth on the nanocellulose films and increased cell death when compared to a commercial control wound dressing, Aquacel®. Nanocellulose suspensions inhibited bacterial growth, whilst UV-vis spectrophotometry and laser profilometry also revealed the ability of nanocellulose to form smooth, translucent films. Atomic force microscopy studies of the surface properties of nanocellulose demonstrated that PAO1 exhibited markedly contrasting morphology when grown on the nanocellulose film surfaces compared to an Aquacel® control dressing (p &lt; 0.05). This study highlights the potential utility of these biodegradable materials, from a renewable source, for wound dressing applications in the prevention and treatment of biofilm development.

  • 14.
    Rashad, Ahmad
    et al.
    University of Bergen, Norway.
    Suliman, Salwa
    University of Bergen, Norway.
    Mustafa, Manal
    Oral Health Centre of Expertise in Western Norway, Norway.
    Pedersen, Torbjörn
    University of Bergen, Norway.
    Campodoni, Elisabetta
    National Research Council of Italy, Italy.
    Sandri, Monica
    National Research Council of Italy, Italy.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Mustafa, Kamal
    University of Bergen, Norway.
    Inflammatory responses and tissue reactions to wood-Based nanocellulose scaffolds2019In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 97, p. 208-221Article in journal (Refereed)
    Abstract [en]

    Two wood-derived cellulose nanofibril (CNF) porous scaffolds were prepared by TEMPO-oxidation and carboxymethylation. The effects of these scaffolds on the production of inflammatory cytokines by human macrophage-like cells (U937) was profiled in vitro after 1 and 3 days and in subcutaneous tissues of rats after 4 and 30 days, using PCR and Multiplex arrays. Tissue culture plates (TCP) and gelatin scaffolds served as controls in vitro and in vivo respectively. After 3 days in vitro, there was no significant difference between the effects of CNF scaffolds and TCP on the production of chemokines/growth factors and pro-inflammatory cytokines. At day 4 in vivo there was significantly higher gene expression of the anti-inflammatory IL-1Ra in the CNF scaffolds than the gelatin scaffold. Production of IL-1β, IL-6, MCP-1, MIP-1α CXCL-1 and M-CSF was significantly less than in the gelatin, demonstrating an early mild inflammatory response. At day 30, both CNF scaffolds significantly stimulated the production of the anti-inflammatory cytokine IL-10. Unlike gelatin, neither CNF scaffold had degraded 180 days post-implantation. The slow degradation of CNF scaffolds resulted in a foreign body reaction, with high production of IL-1β, IL-2, TNF-α, IFN-ϒ, MCP-1, MIP-1α, M-CSF, VEGF cytokines and expression of MMP-9 gene. The surface chemistry of the CNF scaffolds elicited a modest effect on cytokine production and did not shift the inflammatory profile in vitro or in vivo. The decisive role in development of the foreign body reaction was the slow degradation of the CNF scaffolds.

  • 15.
    Rees, Adam
    et al.
    Swansea University, UK.
    Powell, Lydia C.
    Swansea University, UK; Cardiff University, UK.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Gethin, David T.
    Swansea University, UK.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Hill, Katja E.
    Cardiff University, UK.
    Thomas, David W.
    Cardiff University, UK.
    3D bioprinting of carboxymethylated-periodate oxidized nanocellulose constructs for wound dressing applications2015In: BioMed Research International, ISSN 2314-6133, E-ISSN 2314-6141, Vol. 2015, article id 925757Article in journal (Refereed)
    Abstract [en]

    Nanocellulose has a variety of advantages, which make the material most suitable for use in biomedical devices such as wound dressings. The material is strong, allows for production of transparent films, provides a moist wound healing environment, and can form elastic gels with bioresponsive characteristics. In this study, we explore the application of nanocellulose as a bioink for modifying film surfaces by a bioprinting process. Two different nanocelluloses were used, prepared with TEMPO mediated oxidation and a combination of carboxymethylation and periodate oxidation. The combination of carboxymethylation and periodate oxidation produced a homogeneous material with short nanofibrils, having widths <20 nm and lengths <200 nm. The small dimensions of the nanofibrils reduced the viscosity of the nanocellulose, thus yielding a material with good rheological properties for use as a bioink. The nanocellulose bioink was thus used for printing 3D porous structures, which is exemplified in this study. We also demonstrated that both nanocelluloses did not support bacterial growth, which is an interesting property of these novel materials.

  • 16.
    Rogstad Nordli, Henriette
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Rokstad, Anne Mari
    NTNU Norwegian University of Science and Technology, Norway.
    Pukstad, Brita
    NTNU Norwegian University of Science and Technology, Norway; Trondheim University Hospital, Norway.
    Producing ultrapure wood cellulose nanofibrils and evaluating the cytotoxicity using human skin cells2016In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 150, p. 65-73Article in journal (Refereed)
    Abstract [en]

    Wood cellulose nanofibrils (CNF) have been suggested as a potential wound healing material, but its utilization is limited by FDA requirements regarding endotoxin levels. In this study a method using sodium hydroxide followed by TEMPO mediated oxidation was developed to produce ultrapure cellulose nanofibrils, with an endotoxin level of 45 endotoxin units/g (EU/g) cellulose. Scanning transmission electron microscopy (S(T)EM) revealed a highly nanofibrillated structure (lateral width of 3.7 ± 1.3 nm). Assessment of cytotoxicity and metabolic activity on Normal Human Dermal Fibroblasts and Human Epidermal Keratinocytes was done. CNF-dispersion of 50 ÎŒg/ml did not affect the cells. CNF-aerogels induced a reduction of metabolic activity by the fibroblasts and keratinocytes, but no significant cell death. Cytokine profiling revealed no induction of the 27 cytokines tested upon exposure to CNF. The moisture-holding capacity of aerogels was relatively high (∌7500%), compared to a commercially available wound dressing (∌2500%), indicating that the CNF material is promising as dressing material for management of wounds with a moderate to high amount of exudate.

  • 17.
    Shah, Furqan A.
    et al.
    University of Gothenburg, Sweden.
    Omar, Omar
    University of Gothenburg, Sweden.
    Suska, Felicia
    University of Gothenburg, Sweden.
    Snis, Anders
    University of Gothenburg, Sweden; Arcam AB, Sweden.
    Matic, Aleksandar
    Chalmers University of Technology, Sweden.
    Emanuelsson, Lena
    University of Gothenburg, Sweden.
    Norlindh, Birgitta
    University of Gothenburg, Sweden.
    Lausmaa, Jukka
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Medicinteknik. University of Gothenburg, Sweden.
    Thomsen, Peter
    University of Gothenburg, Sweden.
    Palmquist, Anders
    University of Gothenburg, Sweden.
    Long-term osseointegration of 3D printed CoCr constructs with an interconnected open-pore architecture prepared by electron beam melting2016In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 36, p. 296-309Article in journal (Refereed)
    Abstract [en]

    In orthopaedic surgery, cobalt chromium (CoCr) based alloys are used extensively for their high strength and wear properties, but with concerns over stress shielding and bone resorption due to the high stiffness of CoCr. The structural stiffness, principally related to the bulk and the elastic modulus of the material, may be lowered by appropriate design modifications, to reduce the stiffness mismatch between metal/alloy implants and the adjacent bone. Here, 3D printed CoCr and Ti6Al4V implants of similar macro-geometry and interconnected open-pore architecture prepared by electron beam melting (EBM) were evaluated following 26 week implantation in adult sheep femora. Despite higher total bone-implant contact for Ti6Al4V (39 ± 4%) than CoCr (27 ± 4%), bone formation patterns were similar, e.g., densification around the implant, and gradual ingrowth into the porous network, with more bone in the outer half (periphery) than the inner half (centre). Raman spectroscopy revealed no major differences in mineral crystallinity, the apatite-to-collagen ratio, or the carbonate-to-phosphate ratio. Energy dispersive X-ray spectroscopy showed similar Ca/P ratio of the interfacial tissue adjacent to both materials. Osteocytes made direct contact with CoCr and Ti6Al4V. While osteocyte density and distribution in the new-formed bone were largely similar for the two alloys, higher osteocyte density was observed at the periphery of the porous network for CoCr, attributable to slower remodelling and a different biomechanical environment. The results demonstrate the possibility to achieve bone ingrowth into open-pore CoCr constructs, and attest to the potential for fabricating customised osseointegrated CoCr implants for load-bearing applications. Statement of Significance Although cobalt chromium (CoCr) based alloys are used extensively in orthopaedic surgery, stress shielding due to the high stiffness of CoCr is of concern. To reduce the stiffness mismatch between CoCr and bone, CoCr and Ti6Al4V implants having an interconnected open-pore architecture were prepared by electron beam melting (EBM). After six months of submerged healing in sheep, both alloys showed similar patterns of bone formation, with densification around the implant and gradual ingrowth into the porous network. The molecular and elemental composition of the interfacial tissue was similar for both alloys. Osteocytes made direct contact with both alloys, with similar overall osteocyte density and distribution. The work attests to the potential for achieving osseointegration of EBM manufactured porous CoCr implants.

  • 18.
    Shah, Furqan A.
    et al.
    University of Gothenburg, Sweden; BIOMATCELL VINN Excellence Centre of Biomaterials and Cell Therapy, Sweden.
    Stenlund, Patrik
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Medicinteknik. University of Gothenburg, Sweden; BIOMATCELL VINN Excellence Centre of Biomaterials and Cell Therapy, Sweden.
    Martinelli, Anna
    Chalmers University of Technology, Sweden.
    Thomsen, Peter
    University of Gothenburg, Sweden; BIOMATCELL VINN Excellence Centre of Biomaterials and Cell Therapy, Sweden.
    Palmquist, Anders
    University of Gothenburg, Sweden; BIOMATCELL VINN Excellence Centre of Biomaterials and Cell Therapy, Sweden.
    Direct communication between osteocytes and acid-etched titanium implants with a sub-micron topography2016In: Journal of materials science. Materials in medicine, ISSN 0957-4530, E-ISSN 1573-4838, Vol. 27, no 11, article id 167Article in journal (Refereed)
    Abstract [en]

    The osteocyte network, through the numerous dendritic processes of osteocytes, is responsible for sensing mechanical loading and orchestrates adaptive bone remodelling by communicating with both the osteoclasts and the osteoblasts. The osteocyte network in the vicinity of implant surfaces provides insight into the bone healing process around metallic implants. Here, we investigate whether osteocytes are able to make an intimate contact with topologically modified, but micrometre smooth (Sa &lt; 0.5 µm) implant surfaces, and if sub-micron topography alters the composition of the interfacial tissue. Screw shaped, commercially pure (cp-Ti) titanium implants with (i) machined (Sa = ~0.2 µm), and (ii) two-step acid-etched (HF/HNO3 and H2SO4/HCl; Sa = ~0.5 µm) surfaces were inserted in Sprague Dawley rat tibia and followed for 28 days. Both surfaces showed similar bone area, while the bone-implant contact was 73 % higher for the acid-etched surface. By resin cast etching, osteocytes were observed to maintain a direct intimate contact with the acid-etched surface. Although well mineralised, the interfacial tissue showed lower Ca/P and apatite-to-collagen ratios at the acid-etched surface, while mineral crystallinity and the carbonate-to-phosphate ratios were comparable for both implant surfaces. The interfacial tissue composition may therefore vary with changes in implant surface topography, independently of the amount of bone formed. Implant surfaces that influence bone to have higher amounts of organic matrix without affecting the crystallinity or the carbonate content of the mineral phase presumably result in a more resilient interfacial tissue, better able to resist crack development during functional loading than densely mineralised bone.

  • 19.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Controlling the elastic modulus of cellulose nanofibrils hydrogels by crosslinking: a premise for their use in medical applications2014Conference paper (Refereed)
    Abstract [en]

    Cellulose nanofibrils can be utilized as a building block in novel material concepts. One area of particular interest is formation of hydrogels for use in medical applications such as drug delivery and tissue engineering. Compared to bacterial cellulose, which is presently used for some medical applications but is produced through a somewhat inefficient process, cellulose nanofibrils from wood can be produced effectively and in large quantities. Cellulose nanofibrils are nano-scaled fibres with high aspect ratio and strong interactions with water. In order to produce stable macroscopic structures which perform adequately in humid conditions, the nanofibrils must be cross-linked in a controlled way. Several properties are important for a successful utilization of hydrogels for biomedical applications, such as degradation, bio-adhesion, bioactivity, transport through the network and mechanical properties. In the present work focus is set on the mechanical and viscoelastic properties of hydrogels. Hydrogels of oxidized cellulose nanofibrils were formed by crosslinking the nanofibrils through the formation of covalent bonds between the crosslinking molecules and oxidized sites at the nanofibril surfaces. The elastic moduli of the hydrogels were controlled by varying the concentration and the length of the crosslinking molecules. Results from cytotoxicity studies of cellulose nanofibrils will be shown.

  • 20.
    Tehrani, Zari
    et al.
    Swansea University, UK.
    Rogstad Nordli, Henriette
    NTNU Norwegian University of Science and Technology, Norway.
    Pukstad, Brita
    NTNU Norwegian University of Science and Technology, Norway; Trondheim University Hospital, Norway.
    Gethin, David T.
    Swansea University, UK.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Translucent and ductile nanocellulose-PEG bionanocomposites-A novel substrate with potential to be functionalized by printing for wound dressing applications2016In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 93, p. 193-202Article in journal (Refereed)
    Abstract [en]

    There is potential that nanocellulose structures can act as a substrate for biomedical applications in which printing can expand its use as a functionalized biomaterial. Nanocellulose has a variety of advantages, which make the material suitable for use in biomedical devices that include wound dressings. The material does not promote bacterial growth, allows for production of translucent films and provides a moist wound-healing environment. However it is intrinsically brittle so research is needed to develop its flexibility and strength through the addition of plasticisers. In this work, we explore the effect of Polyethylene Glycol (PEG 400) as a plasticizer on nanocellulose film formation and performance. The nanocellulose used was prepared with TEMPO mediated oxidation. We also demonstrated different methods such as laser profilometry and atomic force microscopy to observe the topography and morphology of the films. FTIR, UV-vis spectroscopy was used to look at the characteristics of the nanocellulose films. In addition, the mechanical strength of the films with and without plasticizers was assessed. This led to the formulation of films that included PEG400 at 10-40% by weight. These demonstrated properties that are suitable for wound dressings. Additionally, the PEG modification yielded films that showed a surface morphology adequate for surface modification by printing. Importantly, a cytotoxicity test was performed using Human Dermal Fibroblasts and Human Epidermal Keratinocytes. The results showed no effect on the metabolic activity when fibroblasts were incubated in the presence of films containing 10 and 25% PEG. A reduction was measured in the presence of PEG at 40%. However, no significant cell death was detected in any of the cell-types. Hence, the nanocellulose-PEG films are not considered to be cytotoxic against human skin cells at the concentrations applied in this study.

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