Eva Ålander

Translational study between structure and biological response of nanocellulose from wood and green algae

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

Characterization of paracetamol agglomerates by image analysis and strength measurement

Paracetamol is crystallized in different solvents and techniques are developed and used to characterize the product. The product particles from three different solvent compositions: ethylene glycol, acetone and an acetone-water mixture (30-70 wt.%) have been examined. Product properties visually observed are quantified by image analysis and evaluation of measured image descriptors with Principal Component Analysis (PCA). The agglomerate strength has been determined by crushing single agglomerates. Depending on the solvent, the content of single crystals and agglomerates differ. Agglomerates differ by the number and size of crystals grown together, as well as by the strength.

Surface Chemistry of Nanocellulose Fibers Directs Monocyte/Macrophage Response

The effect of surface functionalization of nanofibrillated cellulose (NFC) on monocyte/macrophage (MM) behavior is investigated to understand how the physicochemical properties of nanocelluloses influence the interactions of such materials with biological systems. Films of anionic (a-), cationic (c-), and unmodified (u-) NFC were synthesized and characterized in terms of surface charge. THP-1 monocytes were cultured on the surface of the films for 24 h in the presence and absence of lipopolysaccharide, and the cell response was evaluated in terms of cell adhesion, morphology, and secretion of TNF-α, IL-10, and IL-1ra. The results show that MMs cultured on carboxymethylated-NFC films (a-NFC) are activated toward a proinflammatory phenotype, whereas u-NFC promotes a mild activation of the studied cells. The presence of hydroxypropyltrimethylammonium groups on c-NFC, however, does not promote the activation of MMs, indicating that c-NFC closely behaves as an inert material in terms of MM activation. None of the materials is able to directly activate the MMs toward an anti-inflammatory response. These results may provide a foundation for the design of future NFC-based materials with the ability to control MM activation and may expand the use of NFC in biomedical applications.

On the use of ion-crosslinked nanocellulose hydrogels for wound healing solutions: Physicochemical properties and application-oriented biocompatibility studies

Calcium ion-crosslinked nanofibrillated cellulose (NFC) hydrogels were investigated as potential materials for wound healing dressings. The physicochemical properties of the hydrogels were examined by rheology and water retention tests. Skin cells and monocytes were selected for application-oriented biocompatibility studies. The NFC hydrogels presented entangled fibrous networks and solid-like behavior. Water retention tests showed the material´s potential to maintain a suitable moist environment for different type of wounds. The hydrogels did not affect dermal fibroblasts monolayer cultures upon direct contact, as cell monolayers remained intact after application, incubation and removal of the materials. Inflammatory response studies with blood-derived mononuclear cells revealed the inert nature of the hydrogels in terms of cytokine secretion and reactive oxygen species production. Results highlight the great potential of ion-crosslinked NFC hydrogels for the development of advanced wound dressings, where further functionalization of the material could lead to improved properties towards the healing of specific wound types.

Admicellar Polymerization Coating of CNF Enhances Integration in Degradable Nanocomposites

A water-based one-pot synthesis strategy for converting cellulose nanofibrils (CNF) into a hydrophobic and processable biopolymer grade is devised. CNF was chemically modified through admicellar polymerization, producing fibrils coated with fatty acrylate polymers. The proposed modification targets a change in the interfibrillar interactions and improved CNF compatibility with a degradable plastic composite matrix, poly(butylene adipate- co-terephthalate), PBAT in composites prepared by melt extrusion. CNF had a clear reinforcing effect on PBAT, increasing Youngs modulus by at least 35% and 169% at 5 and 20% (w/w) CNF content, respectively. However, unmodified CNF showed aggregation, poor adhesion in the matrix, and severely impaired the ductility of PBAT. CNF modified by admicellar polymerization was homogeneously dispersed in the PBT matrix and showed significantly better preservation of the elongation properties compared to unmodified CNF, especially at 5% (w/w) addition level.