| 1. |
- Aguilar Sánchez, Andrea, 1987-
(författare)
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Nanopolysaccharide coatings for functional surfaces in water-treatment materials : From mechanisms to process scalability
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, materials from renewable resources were used to develop functionalized surfaces for water treatment. The work is thus inspired by, and contributes to, the United Nations sustainable goals of: (i) clean water and sanitation, (ii) climate action, (iii) responsible consumption and production, (iv) life below water, and (v) partnerships for the goals.Nanopolysaccharides, most specifically nanocellulose and nanochitin, are great candidates for functional and renewable materials for multiple applications, including the treatment of water and wastewater. This thesis focused on the formulation of different types of nanopolysaccharide-based coatings to enhance the performance of commercially available membranes and cellulose fabrics. We developed a simple waterborne layer-by-layer cellulose nanocrystals (CNC) and TEMPO-oxidized cellulose nanofibrils (T-CNF) coating for commercially available membranes. By changing the surface and pore structure of the membrane, the coating tuned which substrates could pass through the membrane, improved antifouling performanced, and when derived from T-CNF, it was harmful to bacterial colonization. Considering the observed T-CNF’s effect on bacteria, we developed a chemically crosslinked T-CNF/Poly(vinyl) alcohol (PVA) coating with outstanding antibiofouling performance, ion adsorption/rejection combined with size exclusion, and with dimensional and pH stability. Furthermore, we used a surface-impregnation approach based on bio-based nanotechnology which resulted in highly efficient, with improved mechanical properties, and fully bio-based high-flux water filtration membranes using commercially available nonwoven fabrics. Membranes with coatings prepared from CNC, chitin nanocrystals (ChNC) and T-CNF separated particles in the size range of bacteria and viruses, and those prepared from also T-CNF showed high microplastic filtration efficiency. Moreover, membrane coating based on ChNC and T-CNF had outstanding antibacterial properties.Overall, we demonstrated that nanopolysaccharide coatings on membranes could provide a significant reduction in organic fouling and biofilm formation while enabling the adsorption of ions and separation of microplastics. In the case of biofilm formation, the functional group and surface charge of the different nanopolysaccharides determined the effect over bacteria, indicating that surfaces could be tailored against microbes. In addition, we directly compared the effect of the different nanopolysaccharides of interest (CNC, T-CNF, ligno-celullose nanocrystals (L-CNC), and ChNC) on bacterial viability and biofilm formation, and found a great difference between the different types of nanocellulose and a different mechanism for nanochitin. Thorough, none of the nanopolysaccharides displayed cytotoxic effects while in indirect contact with the bacterial cells. Nevertheless, T-CNF, ChNC and L-CNC showed a cytostatic effect on bacterial proliferation. Furthermore, the nanomechanical properties of the bacterial cells and interacting forces between the nanopolysaccharides and Escherichia coli (E. coli) were affected when in direct contact with the nanopolysaccharide surfaces.Lastly, we upscaled one of our coating processes, demonstrating that the method could be easily implemented at an industrial level. The impact of this thesis relies on the effectiveness of the coatings, the different types of functionalities observed, the demonstrated fast implementation at an industrial scale, and the potential to extrapolate this technology to other applications.
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| 2. |
- Asper, M., et al.
(författare)
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Removal of xenotropic murine leukemia virus by nanocellulose based filter paper
- 2015
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Ingår i: Biologicals (Print). - : Elsevier BV. - 1045-1056 .- 1095-8320. ; 43:6, s. 452-456
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Tidskriftsartikel (refereegranskat)abstract
- The removal of xenotrpic murine leukemia virus (xMuLV) by size-exclusion filter paper composed of 100% naturally derived cellulose was validated. The filter paper was produced using cellulose nanofibers derived from Cladophora sp. algae. The filter paper was characterized using atomic force microscopy, scanning electron microscopy, helium pycnometry, and model tracer (100 nm latex beads and 50 nm gold nanoparticles) retention tests. Following the filtration of xMuLV spiked solutions, LRV >= 5.25 log(10) TCID50 was observed, as limited by the virus titre in the feed solution and sensitivity of the tissue infectivity test. The results of the validation study suggest that the nanocellulose filter paper is useful for removal of endogenous rodent retroviruses and retrovirus-like particles during the production of recombinant proteins.
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| 3. |
- Brohede, Ulrika, et al.
(författare)
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A novel graded bioactive high adhesion implant coating
- 2009
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 255:17, s. 7723-7728
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Tidskriftsartikel (refereegranskat)abstract
- One method to increase the clinical success rate of metal implants is to increase their bone bonding properties, i.e. to develop a bone bioactive surface leading to reduced risks of interfacial problems. Much research has been devoted to modifying the surface of metals to make them become bioactive. Many of the proposed methods include depositing a coating on the implant. However, there is a risk of coating failure due to low substrate adhesion. This paper describes a method to obtain bioactivity combined with a high coating adhesion via a gradient structure of the coating. Gradient coatings were deposited on Ti (grade 5) using reactive magnetron sputtering with increasing oxygen content. To increase the grain size in the coating, all coatings were post annealed at 385 degrees C. The obtained coating exhibited a gradual transition over 70 nm from crystalline titanium oxide (anatase) at the surface to metallic Ti in the substrate, as shown using cross-section transmission electron microscopy and X-ray photoelectron spectroscopy depth pro. ling. Using scratch testing, it could be shown that the adhesion to the substrate was well above 1 GPa. The bioactivity of the coating was verified in vitro by the spontaneous formation of hydroxylapatite upon storage in phosphate buffer solution at 37 degrees C for one week. The described process can be applied to implants irrespective of bulk metal in the base and should introduce the possibility to create safer permanent implants like reconstructive devices, dental, or spinal implants.
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| 4. |
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| 5. |
- Brohede, Ulrika, et al.
(författare)
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Multifunctional implant coatings providing possibilities for fast antibiotics loading with subsequent slow release
- 2009
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Ingår i: Journal of materials science. Materials in medicine. - : Springer Science and Business Media LLC. - 0957-4530 .- 1573-4838. ; 20:9, s. 1859-1867
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Tidskriftsartikel (refereegranskat)abstract
- The possibility to fast-load biomimetic hydroxyapatite coatings on surgical implant with the antibiotics Amoxicillin, Gentamicin sulfate, Tobramycin and Cephalothin has been investigated in order to develop a multifunctional implant device offering sustained local anti-bacterial treatment and giving the surgeon the possibility to choose which antibiotics to incorporate in the implant at the site of surgery. Physical vapor deposition was used to coat titanium surfaces with an adhesion enhancing gradient layer of titanium oxide having an amorphous oxygen poor composition at the interface and a crystalline bioactive anatase TiO2 composition at the surface. Hydroxyapatite (HA) was biomimetically grown on the bioactive TiO2 to serve as a combined bone in-growth promoter and drug delivery vehicle. The coating was characterized using scanning and transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The antibiotics were loaded into the HA coatings via soaking and the subsequent release and antibacterial effect were analyzed using UV spectroscopy and examination of inhibition zones in a Staphylococcus aureus containing agar. It was found that a short drug loading time of 15 min ensured antibacterial effects after 24 h for all antibiotics under study. It was further found that the release processes of Cephalothin and Amoxicillin consisted of an initial rapid drug release that varied unpredictably in amount followed by a reproducible and sustained release process with a release rate independent of the drug loading times under study. Thus, implants that have been fast-loaded with drugs could be stored for ~10 min in a simulated body fluid after loading to ensure reproducibility in the subsequent release process. Calculated release rates and measurements of drug amounts remaining in the samples after 22 h of release indicated that a therapeutically relevant dose could be achieved close to the implant surface for about 2 days. Concluding, the present study provides an outline for the development of a fast-loading slow-release surgical implant kit where the implant and the drug are separated when delivered to the surgeon, thus constituting a flexible solution for the surgeon by offering the choice of quick addition of antibiotics to the implant coating based on the patient need.
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| 6. |
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| 7. |
- Carlsson, Daniel O., et al.
(författare)
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Aspirin degradation in surface-charged TEMPO-oxidized mesoporous crystalline nanocellulose
- 2013
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Ingår i: International Journal of Pharmaceutics. - : Elsevier BV. - 0378-5173 .- 1873-3476. ; 461:1-2, s. 74-81
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Tidskriftsartikel (refereegranskat)abstract
- TEMPO-mediated surface oxidation of mesoporous highly crystalline Cladophora cellulose was used to introduce negative surface charges onto cellulose nanofibrils without significantly altering other structural characteristics. This enabled the investigation of the influence of mesoporous nanocellulose surface charges on aspirin chemical stability to be conducted. The negative surface charges (carboxylate content 0.44 ± 0.01 mmol/g) introduced on the mesoporous crystalline nanocellulose significantly accelerated aspirin degradation, compared to the starting material which had significantly less surface charge (0.06 ± 0.01 mmol/g). This effect followed from an increased aspirin amorphisation ability in mesopores of the oxidized nanocellulose. These results highlight the importance of surface charges in formulating nanocellulose for drug delivery.
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| 8. |
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| 9. |
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| 10. |
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| 11. |
- Carlsson, Daniel O., et al.
(författare)
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Cooxidant-free TEMPO-mediated oxidation of highly crystalline nanocellulose in water
- 2014
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 4:94, s. 52289-52298
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Tidskriftsartikel (refereegranskat)abstract
- Selective oxidation of C6 hydroxyls to carboxyls through 2,2,6,6,-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, where the oxidizing species (TEMPO+) is generated by cooxidants, such as NaBrO, NaClO or NaClO2, has become a popular way to modify the surfaces of nanocellulose fibrils in aqueous solutions. Employing highly crystalline nanocellulose from Cladophora sp. algae we demonstrate that the same degree of oxidation (D.O.) can be achieved within approximately the same time by replacing the cooxidants with electrogeneration of TEMPO+ in a bulk electrolysis setup. The D.O. is controlled by the oxidation time and the maximum D.O. achieved (D.O. 9.8%, 0.60 mmol g-1 of carboxylic acids and 0 mmol g-1 aldehydes) corresponds to complete oxidation of the surface-confined C6. This shows that TEMPO+ is not sterically hindered from completely oxidizing the fibril surface of Cladophora nanocellulose, in contrast to earlier hypotheses that were based on results with wood-derived nanocellulose. The oxidation does not significantly affect the morphology, the specific surface area (>115 m2 g-1) or the pore characteristics of the water-insoluble fibrous particles that were obtained after drying, but depolymerization corresponding to ∼20% was observed. For extensive oxidation times, the product recovery of water-insoluble fibrils decreased significantly while significant amounts of charge passed through the system. This could indicate that the oxidation proceeds beyond the fibril surface, in contrast to the current view that TEMPO-mediated oxidation is confined only to the surface.
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| 12. |
- Carlsson, Daniel O., et al.
(författare)
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Cooxidant-free TEMPO-mediated oxidation of highly crystalline nanocellulose in water
- 2014
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Ingår i: RSC Advances. - 2046-2069. ; 4:94, s. 52289-52298
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Tidskriftsartikel (refereegranskat)abstract
- Selective oxidation of C6 hydroxyls to carboxyls through 2,2,6,6,-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, where the oxidizing species (TEMPO+) is generated by cooxidants, such as NaBrO, NaClO or NaClO2, has become a popular way to modify the surfaces of nanocellulose fibrils in aqueous solutions. Employing highly crystalline nanocellulose from Cladophora sp. algae we demonstrate that the same degree of oxidation (D.O.) can be achieved within approximately the same time by replacing the cooxidants with electrogeneration of TEMPO+ in a bulk electrolysis setup. The D.O. is controlled by the oxidation time and the maximum D.O. achieved (D.O. 9.8%, 0.60 mmol g-1 of carboxylic acids and 0 mmol g-1 aldehydes) corresponds to complete oxidation of the surface-confined C6. This shows that TEMPO+ is not sterically hindered from completely oxidizing the fibril surface of Cladophora nanocellulose, in contrast to earlier hypotheses that were based on results with wood-derived nanocellulose. The oxidation does not significantly affect the morphology, the specific surface area (>115 m2 g-1) or the pore characteristics of the water-insoluble fibrous particles that were obtained after drying, but depolymerization corresponding to [similar]20% was observed. For extensive oxidation times, the product recovery of water-insoluble fibrils decreased significantly while significant amounts of charge passed through the system. This could indicate that the oxidation proceeds beyond the fibril surface, in contrast to the current view that TEMPO-mediated oxidation is confined only to the surface.
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| 13. |
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| 14. |
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| 15. |
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| 16. |
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| 17. |
- Carlsson, Daniel O
(författare)
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Structural and Electrochemical Properties of Functionalized Nanocellulose Materials and Their Biocompatibility
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 18. |
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| 19. |
- Carlsson, Daniel O., et al.
(författare)
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Tailoring porosities and electrochemical properties of composites composed of microfibrillated cellulose and polypyrrole
- 2014
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 4:17, s. 8489-8497
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 20. |
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| 21. |
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| 22. |
- Ferraz, Natalia, et al.
(författare)
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Haemocompatibility and ion exchange capability of nanocellulose polypyrrole membranes intended for blood purification
- 2012
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Ingår i: Journal of the Royal Society Interface. - : The Royal Society. - 1742-5689 .- 1742-5662. ; 9:73, s. 1943-1955
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 23. |
- Ferraz, Natalia, et al.
(författare)
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In vitro and in vivo toxicity of rinsed and aged nanocellulose-polypyrrole composites
- 2012
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Ingår i: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 100A:8, s. 2128-2138
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Tidskriftsartikel (refereegranskat)abstract
- Novel composites of nanocellulose and the conducting polymer polypyrrole (PPy) are herein suggested as potential candidates for active ion-extraction membranes in electrochemically controlled hemodialysis. This work has defined processing parameters to obtain a biocompatible nanocellulose-PPy composite and for the first time, the effect of the composite ageing on cell viability has been studied.The influence of rinsing and extraction process steps, as well as ageing under different conditions (i.e. in air, at –20 ˚C and in argon), on the electroactivity and cytotoxicity of a PPy-nanocellulose composite has been investigated. The biocompatibility evaluation was based on indirect toxicity assays with fibroblasts and monocyte cell lines and an acute toxicity test in mice, while the electroactivity was evaluated by cyclic voltammetry experiments.The as-prepared composite did not induce any cytotoxic response in vitro or in vivo. Extensive rinsing and 48 hour incubation in biological buffer previous to the preparation of the culture medium extracts were, however, necessary to obtain a non-cytotoxic composite. The as-prepared composite was also found to exhibit acceptable electrochemical performance, which was retained upon 4 weeks storage in argon atmosphere. It was shown that ageing of the composite had a negative effect on biocompatibility, regardless of the storage condition. Thus, to allow for long time storage of electroactive nanocellulose-PPy hemodialysis membranes, the degradation of PPy upon storage must be controlled. The present results show that the biocompatibility of PPy composites depends on the rinsing and pre-treatment of the composite material as well as the aging of the material.
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| 24. |
- Ferraz, Natalia, et al.
(författare)
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Is there a future for electrochemically assisted hemodialysis? : focus on the application of polypyrrole-nanocellulose composites
- 2014
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Ingår i: Nanomedicine. - : Future Medicine Ltd. - 1743-5889 .- 1748-6963. ; 9:7, s. 1095-1110
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Tidskriftsartikel (refereegranskat)abstract
- This work summarizes the various aspects of using electrochemically assisted solute removal techniques in hemodialysis with a focus on blood electrodialysis and electrochemically controlled uremic retention solute removal using polypyrrole. In particular, the feasibility of using highly porous conductive polypyrrole-Cladophora cellulose membranes for hemodialysis are overviewed as a part of our dedicated research efforts during the past 4 years. The potential benefits and the current limitations associated with using the electrochemically controlled uremic retention solute removal techniques are discussed in detail.
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| 25. |
- Ferraz, Natalia, et al.
(författare)
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Is there a future for electrochemically assisted hemodialysis? : Focus on the application of polypyrrole-nanocellulose composites
- 2014
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Ingår i: Nanomedicine. - 1743-5889 .- 1748-6963. ; 9:7, s. 1095-1110
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Forskningsöversikt (refereegranskat)abstract
- This work summarizes the various aspects of using electrochemically assisted solute removal techniques in hemodialysis with a focus on blood electrodialysis and electrochemically controlled uremic retention solute removal using polypyrrole. In particular, the feasibility of using highly porous conductive polypyrrole-Cladophora cellulose membranes for hemodialysis are overviewed as a part of our dedicated research efforts during the past 4 years. The potential benefits and the current limitations associated with using the electrochemically controlled uremic retention solute removal techniques are discussed in detail.
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| 26. |
- Ferraz, Natalia, et al.
(författare)
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Membrane characterization and solute diffusion in porous composite nanocellulose membranes for hemodialysis
- 2013
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Ingår i: Cellulose. - : Springer. - 0969-0239 .- 1572-882X. ; 20:6, s. 2959-2970
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Tidskriftsartikel (refereegranskat)abstract
- The membrane and solute diffusion properties of Cladophora cellulose and polypyrrole (PPy) functionalized Cladophora cellulose were analyzed to investigate the feasibility of using electroactive membranes in hemodialysis. The membranes were characterized with scanning electron microscopy, zeta-potentiometry, He-pycnometry, N-2 gas adsorption, and Hg porosimetry. The diffusion properties across the studied membranes for three model uremic toxins, i.e. creatinine, vitamin B12 and bovine serum albumin, were also analyzed. The characterization work revealed that the studied membranes present an open structure of weakly negatively charged nanofibers with an average pore size of 21 and 53 nm for pristine cellulose and PPy-Cladophora cellulose, respectively. The results showed that the diffusion of uremic toxins across the PPy-Cladophora cellulose membrane was faster than through pure cellulose membrane, which was related to the higher porosity and larger average pore size of the former. Since it was found that the average pore size of the membranes was larger than the hydrodynamic radius of the studied model solutes, it was concluded that these types of membranes are favorable to expand the Mw spectrum of uremic toxins to also include conditions associated with accumulation of large pathologic proteins during hemodialysis. The large average pore size of the composite membrane could also be exploited to ensure high-fluxes of solutes through the membrane while simultaneously extracting ions by an externally applied electric current.
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| 27. |
- Forsgren, Johan, et al.
(författare)
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A Template-Free, Ultra-Adsorbing, High Surface Area Carbonate Nanostructure
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:7, s. e68486-
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Tidskriftsartikel (refereegranskat)abstract
- We report the template-free, low-temperature synthesis of a stable, amorphous, and anhydrous magnesium carbonate nanostructure with pore sizes below 6 nm and a specific surface area of ~ 800 m2 g−1, substantially surpassing the surface area of all previously described alkali earth metal carbonates. The moisture sorption of the novel nanostructure is featured by a unique set of properties including an adsorption capacity ~50% larger than that of the hygroscopic zeolite-Y at low relative humidities and with the ability to retain more than 75% of the adsorbed water when the humidity is decreased from 95% to 5% at room temperature. These properties can be regenerated by heat treatment at temperatures below 100°C.The structure is foreseen to become useful in applications such as humidity control, as industrial adsorbents and filters, in drug delivery and catalysis.
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| 28. |
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| 29. |
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| 30. |
- Forsgren, Johan, et al.
(författare)
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In Vivo Evaluation of Functionalized Biomimetic Hydroxyapatite for Local Delivery of Active Agents
- 2011
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Ingår i: Journal of Biomaterials and Nanobiotechnology. - : Scientific Research Publishing, Inc.. - 2158-7027 .- 2158-7043. ; 2:2, s. 149-154
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Tidskriftsartikel (refereegranskat)abstract
- This study was carried out to investigate the biological response in vivo to biomimetic hydroxyapatite implant coatings functionalized with bisphosphonates and bone morphogenetic proteins. The functionalization was carried out by a simple soaking procedure in the operating room immediately prior to surgery. Cylindrical titanium samples with and without coatings were implanted in the distal femoral epiphysis of sheep and retrieved after 6 weeks. The histological analysis proved that all samples were integrated well in the tissue with no signs of intolerance. Fewer osteoclasts were observed in the vicinity of bisphosphonate-functionalized samples and the bone was denser around these samples compared to the other samples. Samples functionalized with bone morphogenetic protein induced more bone/implant contact but showed a more inconsistent outcome with reduced bone density around the samples. This study demonstrates a simple method to functionalize implant coatings, which provides surgeons with an option of patient-specific functionalization of implants. The observed biological impact due to the delivery of active molecules from the coatings suggests that this strategy may also be employed to deliver antibiotics from similar coatings.
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| 31. |
- Forsgren, Johan, et al.
(författare)
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Mesoporous Calcium Carbonate as a Phase Stabilizer of Amorphous Celecoxib - An Approach to Increase the Bioavailability of Poorly Soluble Pharmaceutical Substances.
- 2013
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Ingår i: Advanced healthcare materials. - : Wiley. - 2192-2640. ; 2:11, s. 1469-1476
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Tidskriftsartikel (refereegranskat)abstract
- The bioavailability of crystalline pharmaceutical substances is often limited by their poor aqueous solubility but it can be improved by formulating the active substance in the amorphous state that is featured with a higher apparent solubility. Although the possibility of stabilizing amorphous drugs inside nano-sized pores of carbon nanotubes and ordered mesoporous silica has been shown, no conventional pharmaceutical excipients have so far been shown to possess this property. This study demonstrates the potential of using CaCO3 , a widely used excipient in oral drug formulations, to stabilize the amorphous state of active pharmaceutical ingredients, in particular celecoxib. After incorporation of celecoxib in the vaterite particles, a five to sixfold enhancement in apparent solubility of celecoxib is achieved due to pore-induced amorphization. To eliminate the possibility of uncontrolled phase transitions, the vaterite particles were stored in an inert atmosphere at 5 °C throughout the study. Also, to demonstrate that the amorphization effect was indeed associated with vaterite mesopores, accelerated stress conditions of 100% relative humidity was employed to impose transition from mesoporous vaterite to an essentially non-porous aragonite phase of CaCO3 , which shows only limited amorphization ability. Further, an improvement in solubility was also confirmed for ketoconazole when formulated with the mesoporous vaterite. Synthesis of the carrier particles and the incorporation of the active substances were carried out simultaneously in a one-step procedure, enabling easy fabrication. These results represent a promising approach to achieve enhanced bioavailability in new formulations of Type II BCS drugs.
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| 32. |
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| 33. |
- Frykstrand, Sara, et al.
(författare)
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On the pore forming mechanism of Upsalite, a micro- and mesoporous magnesium carbonate
- 2014
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 190, s. 99-104
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Tidskriftsartikel (refereegranskat)abstract
- This work analyzes the pore forming mechanism and stability of Upsalite; an extraordinary moisture absorbing, high-surface area magnesium carbonate powder synthesised without the use of surfactants as pore forming agents. The pores in Upsalite were found to be created in a two-step process where the first step includes the formation of micropores by solvent evaporation and release of physically bound carbon dioxide, acting as an in-situ pore-forming template. In the second step, the micropores expand to mesopores due to partial decomposition of organic groups on the surface of the pore walls when the material is stored in air at moderate temperatures (70 °C). The resulting material has a narrow pore size distribution centered at 5 nm, and the amorphous structure is stable upon storage in a humid atmosphere.It was further shown that calcination at temperatures above 250 °C is required for complete removal of the organic surface groups in Upsalite. Prior to calcination, the organic groups present in the material act as barriers hindering water to induce crystallization of the bulk material. After calcination, however, Upsalite crystallizes into nesquehonite when stored at 100 % relative humidity for several days. The results presented herein are expected to be useful for the development of novel surfactant-free synthesis routes of porous materials as well as for the understanding of the long-term performance of such materials.
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| 41. |
- Gelin, Kristina, et al.
(författare)
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Characterization of water in bacterial cellulose using dielectric spectroscopy and electron microscopy
- 2007
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861 .- 1873-2291. ; 48:26, s. 7623-7631
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Tidskriftsartikel (refereegranskat)abstract
- It is shown that only 10% of the 99 wt% water present in bacterial cellulose (BC) gels, produced by Acetobacter xylinum, behave like free bulk water; the majority of the water molecules in the gels is more or less tightly bound to the cellulose. The magnitude of the diffusion coefficients of ions transported in the water phase of the BC gels as well as the information contained in freeze fracture transmission electron microscopic images of the gel structures indicates that the bulk-like water is confined in “lakes” rather than forming a continuous phase throughout the gel. Water desorption isotherms suggest that these “lakes” decrease in size with increasing oxygen concentration used during the biosynthesis process of the gels.
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| 42. |
- Gelin, Kristina, et al.
(författare)
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Potential controlled anion absorption in a novel high surface area composite of Cladophora cellulose and polypyrrole
- 2009
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Ingår i: Electrochimica Acta. - : Elsevier Ltd. - 0013-4686 .- 1873-3859. ; 54:12, s. 3394-3401
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Tidskriftsartikel (refereegranskat)abstract
- The electrochemical properties of a novel composite paper material of high surface area consisting of polypyrrole (PPy) deposited on cellulose derived from Cladophora sp. algae have been investigated in electrolytes containing different concentrations of nitrate, chloride and p-toluene sulfonate, as well as in solutions containing both p-toluene sulfonate and chloride. The oxidation mechanism and the dependence of the oxidation behavior of the polypyrrole, which was obtained by oxidation of pyrrole with iron(III) chloride, on the anion type and concentration have been studied. Current nucleation maxima, appearing at different times depending on the anion concentration, were obtained during the oxidation of the reduced polymers as a result of the combined action of the formation and growth of conducting polymer strands and anion diffusion. No loss of capacity was seen during repeated oxidation and reduction of the polymer indicating that trapping of anions in the reduced polymer did not limit the electroactivity of the present material. The latter can be explained by the thin polymer layer present on the cellulose substrate. During the oxidation of the polymer, the anions most likely first cover most of the surface of the composite before diffusing into the bulk of the polymer. The estimated distance between these surface sites was also found to match the size of the anions. For electrolytes containing a mixture of anions, the oxidation charge depends on the concentration and size of the different anions.The combination of the thin polymer coating and the large specific surface area of the composite give rise to a high ion absorption capacity even for large anions. Hence, the investigated material should be well-suited for use in biotechnological applications involving, e.g., desalting and extraction of proteins and DNA from biological samples.
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| 43. |
- Gustafsson, Olof, et al.
(författare)
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High-Performance Virus Removal Filter Paper for Drinking Water Purification
- 2018
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Ingår i: Global Challenges. - : Wiley. - 2056-6646. ; 2:7
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Tidskriftsartikel (refereegranskat)abstract
- Access to drinking water is one of the greatest global challenges today. In this study, the virus removal properties of mille‐feuille nanocellulose‐based filter papers of varying thicknesses from simulated waste water (SWW) matrix are evaluated for drinking water purification applications. Filtrations of standard SWW dispersions at various total suspended solid (TSS) content are performed, including spiking tests with 30 nm surrogate latex particles and 28 nm ΦX174 bacteriophages. Filter papers of thicknesses 9 and 29 µm are used, and the filtrations are performed at two different operational pressures, i.e., 1 and 3 bar. The presented data using SWW matrix show, for the first time, that a filter paper made from 100% nanocellulose has the capacity to efficiently remove even the smallest viruses, i.e., up to 99.9980–99.9995% efficiency, at industrially relevant flow rates, i.e., 60–500 L m−2 h−1, and low fouling, i.e., V max > 103–104 L m−2. The filter paper presented in this work shows great promise for the development of robust, affordable, and sustainable water purification systems.
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| 44. |
- Gustafsson, Olof, et al.
(författare)
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Scalable and Sustainable Total Pathogen Removal Filter Paper for Point-of-Use Drinking Water Purification in Bangladesh
- 2019
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Ingår i: ACS Sustainable Chemistry and Engineering. - : AMER CHEMICAL SOC. - 2168-0485. ; 7:17, s. 14373-14383
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Tidskriftsartikel (refereegranskat)abstract
- This article describes for the first time the full cycle of development from raw material cultivation to real-life application of a truly sustainable and scalable filter paper material intended for point-of-use drinking water purification in Bangladesh. The filter paper, featuring tailored pathogen removal properties, is produced from nanocellulose extracted from Pithophora green macroalgae, growing locally in Bangladesh, a new unexploited resource that can address a global problem. We demonstrate that the Pithophora cellulose filter paper can be used as a total pathogen barrier to remove all types of infectious viruses and bacteria from water. The performance of the filter is validated using surrogate latex nanobeads, in vitro model viruses, and real-life water samples collected from the Turag River and Dhanmondi Lake in Dhaka, Bangladesh. Access to clean drinking water is a persistent problem in Bangladesh, affecting tens of millions of people every day. The mortality rate due to water-borne diarreal infections, including viral infections, among susceptible population groups, especially among children under age of 5, is still very high. The proposed solution can dramatically improve the quality of lives for millions of people in the entire Southeast Asian region including and beyond the borders of Bangladesh.
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| 45. |
- Gustafsson, Olof, et al.
(författare)
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Significance of Brownian Motion for Nanoparticle and Virus Capture in Nanocellulose-Based Filter Paper
- 2018
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Ingår i: Membranes. - : MDPI AG. - 2077-0375. ; 8:4
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Tidskriftsartikel (refereegranskat)abstract
- Pressure-dependent breakthrough of nanobioparticles in filtration was observed and it was related to depend on both convective forces due to flow and diffusion as a result of Brownian motion. The aim of this work was to investigate the significance of Brownian motion on nanoparticle and virus capture in a nanocellulose-based virus removal filter paper through theoretical modeling and filtration experiments. Local flow velocities in the pores of the filter paper were modeled through two different approaches (i.e., with the Hagen–Poiseuille equation) and by evaluating the superficial linear flow velocity through the filter. Simulations by solving the Langevin equation for 5 nm gold particles and 28 nm ΦX174 bacteriophages showed that hydrodynamic constraint is favored for larger particles. Filtration of gold nanoparticles showed no difference in retention for the investigated fluxes, as predicted by the modeling of local flow velocities. Filtration of ΦX174 bacteriophages exhibited a higher retention at higher filtration pressure, which was predicted to some extent by the Hagen–Poiseuille equation but not by evaluation of the superficial linear velocity. In all, the hydrodynamic theory was shown able to explain some of the observations during filtration.
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| 46. |
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| 47. |
- Gustafsson, Simon, 1988-, et al.
(författare)
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Comparative Analysis of Dry and Wet Porometry Methods for Characterization of Regular and Cross-Linked Virus Removal Filter Papers
- 2019
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Ingår i: Membranes. - : MDPI AG. - 2077-0375. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Pore-size distribution (PSD) is the most critical parameter for size-exclusion virus removal filters. Yet, different dry- and wet-state porometry methods yield different pore-size values. The goal of this work is to conduct comparative analysis of nitrogen gas sorption (NGSP), liquid-liquid and cryoporometry with differential scanning calorimetry (CP-DSC) methods with respect to characterization of regular and cross-linked virus removal filter paper based on cellulose nanofibers, i.e. the mille-feuille filter. The filters were further characterized with atomic force and scanning electron microscopy. Finally, the removal of the worst-case model virus, i.e. minute virus of mice (MVM; 20 nm, nonenveloped parvovirus) was evaluated. The results revealed that there is no difference of the obtained PSDs between the wet methods, i.e. DSC and liquid-liquid porometry (LLP), as well as no difference between the regular and cross-linked filters regardless of method. MVM filtration at different trans membrane pressure (TMP) revealed strong dependence of the virus removal capability on applied pressure. It was further observed that cross-linking filters showed enhanced virus removal, especially at lower TMP. In all, the results of this study highlight the complex nature of virus capture in size-exclusion filters.
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| 48. |
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| 49. |
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| 50. |
- Gustafsson, Simon, 1988-, et al.
(författare)
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Investigating Protein Throughput, Vmax Values and Virus Removal Efficiency of the Paper Based Mille-Feuille Filter
- 2017
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Ingår i: Abstracts of Papers of the American Chemical Society. - : American Chemical Society (ACS). - 0065-7727. ; 253
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In this work we present Vmax values and throughput for the nanocellulose-based Mille-feuille virus removal filter paper as well as evaluate the affinity of different proteins for the cellulose surface using quartz crystal microbalance (QCMB). The Minute Virus of Mice (MVM) virus removal result for the Mille-feuille filter is also presented. The nanocellulose-based Mille-feuille filter is a non-woven, µm-thick filter paper with a narrow and tailorable pore size distribution, highly suitable for removing viruses of all sizes, including the worst case model Minute Virus of Mice (MVM). It is produced by hot-pressing method rather than by phase-inversion which is otherwise used to manufacture industrial analogues. Robust and cost-efficient virus removal processes are in high demand for the biotechnology industry, especially for the production of monoclonal antibodies derived from mammalian cell lines, therapeutic proteins derived from human plasma, and cell culture media. Non-woven filters have the advantage in contrast to regular phase-inversion made filters of a much higher porosity. For instance, the Mille-feuille filter has a porosity of 42% compared to 10-15% of the functional skin layer in asymmetric virus removal filters used today. In theory a higher porosity will result in higher flow rates. However, it also means that there is a larger filter area exposed to filtrate. Therefore investigating the surface affinity for proteins with different hydrophobicity and charge using QCMB is of great importance to be able to predict protein filtration behaviour. The presented work is a part of continuous efforts to develop a new class of highly efficient and affordable virus removal filters.
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