Susceptibility of Iα- and Iß-Dominated Cellulose to TEMPO-Mediated Oxidation.

The susceptibility of Iα- and Iß-dominated cellulose to TEMPO-mediated oxidation was studied in this work since the cellulose Iα-allomorph is generally considered to be thermodynamically less stable and therefore more reactive than the cellulose Iß-allomorph. Highly crystalline Cladophora nanocellulose, which is dominated by the Iα-allomorph, was oxidized to various degrees with TEMPO oxidant via bulk electrolysis in the absence of co-oxidants. Further, the Cladophora nanocellulose was thermally annealed in glycerol to produce its Iß-dominated form and then oxidized. The produced materials were subsequently studied using FTIR, CP/MAS (13)C NMR, XRD, and SEM. The solid-state analyses confirmed that the annealed Cladophora cellulose was successfully transformed from an Iα- to an Iß-dominated form. The results of the analyses of pristine and annealed TEMPO-oxidized samples suggest that Iα- and Iß-dominated cellulose do not differ in susceptibility to TEMPO-oxidation. This work hence suggests that cellulose from different sources are not expected to differ in susceptibility to the oxidation due to differences in allomorph composition.

Direct ink writing of high-resolution cellulose structures.

3D printing is envisioned to play an important role in the production of membranes for e.g., water purification and bio-separation applications due to the prospect of creating new and cleverly designed structures. Among different 3D printing techniques, direct ink writing offers the opportunity to print a wide variety of materials with high-detail resolution. There is a range of parameters that need to be optimized in order to develop robust printing techniques at that scale. In this study, cellulose acetate (CA), which is a biocompatible material, has been used as an ink. In order to examine the printability and the possibility of printing features as small as a few µm, nozzles with different diameters and inks with varying amounts and molecular weights of CA were investigated. Findings in this study indicate that, depending on the wetting on the underlaying structure, the nozzle's internal and external diameter affects the detail resolution of the printed structure. Different inks result in different widths of printed strands and generally a higher amount and higher molecular weights of CA results in higher detail resolution. However, too high amount of CA and molecular weight will increase the clogging risk in the nozzle. In this study, the internal size of the nozzle was 3 µm, and by selecting a  suitable ink, it was possible to print strands down to 1 µm size and 6 µm inter-strand distance in the air, bridging supports with limited sagging. Furthermore, wall structures consisting of 300 layers, corresponding to about 300 µm in total height, were successfully printed.

Feasibility of using DNA-immobilized nanocellulose-based immunoadsorbent for systemic lupus erythematosus plasmapheresis.

The goal of this project was to study the feasibility of using a DNA-immobilized nanocellulose-based immunoadsorbent for possible application in medical apheresis such as systemic lupus erythematosus (SLE) treatment. Calf thymus DNA was bound to high surface area nanocellulose membrane at varying concentrations using UV-irradiation. The DNA-immobilized samples were characterized with scanning electron microscopy, atomic force microscopy, and phosphorus elemental analysis. The anti-ds-DNA IgG binding was tested in vitro using ELISA. The produced sample showed high affinity in vitro to bind anti-ds-DNA-antibodies from mice, as much as 80% of added IgG was bound by the membrane. Furthermore, the binding efficiency was quantitatively dependent on the amount of immobilized DNA onto nanocellulose membrane. The described nanocellulose membranes are interesting immunoadsorbents for continued clinical studies.

Surface Modified Nanocellulose Fibers Yield Conducting Polymer-Based Flexible Supercapacitors with Enhanced Capacitances.

We demonstrate that surface modified nanocellulose fibers (NCFs) can be used as substrates to synthesize supercapacitor electrodes with the highest full electrode-normalized gravimetric (127 F g(-1)) and volumetric (122 F cm(-3)) capacitances at high current densities (300 mA cm(-2) ≈ 33 A g(-1)) until date reported for conducting polymer-based electrodes with active mass loadings as high as 9 mg cm(-2). By introducing quaternary amine groups on the surface of NCFs prior to polypyrrole (PPy) polymerization, the macropore volume of the formed PPy-NCF composites can be minimized while maintaining the volume of the micro- and mesopores at the same level as when unmodified or carboxylate groups functionalized NCFs are employed as polymerization substrates. Symmetric, aqueous electrolyte-based, devices comprising these porosity-optimized electrodes exhibit device-specific volumetric energy and power densities of 3.1 mWh cm(-3) and 3 W cm(-3) respectively; which are among the highest values reported for conducting polymer electrodes in aqueous electrolytes. The functionality of the devices is verified by powering a red light-emitting diode with the device in different mechanically challenging states.

Aspirin degradation in surface-charged TEMPO-oxidized mesoporous crystalline nanocellulose.

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.

A comparative study of the effects of rinsing and aging of polypyrrole/nanocellulose composites on their electrochemical properties.

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

Haemocompatibility and ion exchange capability of nanocellulose polypyrrole membranes intended for blood purification.

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 m(2) 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.