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Authors Alexander Henn, Nina Forsman, and Monika sterberg declare that they have a financial interest in the development and commercialization of the research presented in this article. Aalto University has filed a provisional patent application (FI 20205555). Funding Information: KAH, NF and TZ thank Business Finland for financing via the LignoSphere project (project number: 2117744). This work was also a part of the Academy of Finland's Flagship Programme under projects No. 318890 and 318891 (Competence Center for Materials Bioeconomy, FinnCERES), financial support for KAH. The authors also thank Dr. Heidi Henrickson for her excellent help with proofreading and guidance, Mr. Rob Hindley for his generous help with linguistic support and proofreading, and Valeria Azovskaya for her helpful advice regarding the graphical material. Publisher Copyright: © 2021 The Authors. Published by American Chemical Society. There is a need for safe and sustainable alternatives in the coating industry. Bio-based coatings are interesting in this perspective. Although various oils and waxes have been used as traditional wood coatings, they often lack sufficient durability. Lignin is an abundant natural polyphenol that can be used to cure epoxies, but its poor water solubility has impeded the use of unmodified lignin in coatings in the past. To address this issue, water-dispersible colloidal lignin particles (CLPs) and an epoxy compound, glycerol diglycidyl ether (GDE), were used to prepare multiprotective bio-based surface coatings. With the GDE/CLP ratios of 0.65 and 0.52 g/g, the cured CLP-GDE films became highly resistant to abrasion and heat. When applied as a coating on wooden substrates, the particulate morphology enabled effective protection against water, stains, and sunlight with very thin layers (less than half the weight of commercial coatings) while retaining the wood's breathability excellently. Optimal hydrophobicity was reached with a coat weight of 6.9 g(CLP)/m2, resulting in water contact angle values of up to 120°. Due to their spherical shape and chemical structure, the CLPs acted as both a hardener and a particulate component in the coating, which removed the need for an underlying binding polymer matrix. Light interferometry measurements showed that while commercial polymeric film-forming coatings smoothened the substrate noticeably, the particulate morphology retained the substrate's roughness in lightweight coatings, allowing for a high water contact angle. This work presents new strategies for lignin applications in durable particulate coatings and their advantages compared to both currently used synthetic and bio-based coatings.

openaire: EC/H2020/788489/EU//BioELCell Funding Information: We are thankful for funding support from Commission H2020 program ERC Advanced Grant (No. 788489, BioELCell), the Canada Excellence Research Chair initiative and the Canada Foundation for Innovation (CFI). We are grateful for the support by the FinnCERES Materials Bioeconomy Ecosystem. B. Zhao is grateful for the financial support from the China Scholarship Council (Project #201702640280) and NordForsk Project 82214 “High-Value Products from Lignin”. The authors thank L. Greca for providing the lignin microparticles and for discussions on their oxidative thermostabilization. The authors thank I. Schlapp-Hackl for assisting in the installation of the CO adsorption device. We also acknowledge J. Campbell for XPS measurements. 2 Publisher Copyright: © 2021 The Authors. Published by American Chemical Society. Copyright: Copyright 2021 Elsevier B.V., All rights reserved. Multiscale carbon supraparticles (SPs) are synthesized by soft-templating lignin nano- and microbeads bound with cellulose nanofibrils (CNFs). The interparticle connectivity and nanoscale network in the SPs are studied after oxidative thermostabilization of the lignin/CNF constructs. The carbon SPs are formed by controlled sintering during carbonization and develop high mechanical strength (58 N·mm-3) and surface area (1152 m2·g-1). Given their features, the carbon SPs offer hierarchical access to adsorption sites that are well suited for CO2 capture (77 mg CO2·g-1), while presenting a relatively low pressure drop (∼33 kPa·m-1 calculated for a packed fixed-bed column). The introduced lignin-derived SPs address the limitations associated with mass transport (diffusion of adsorbates within channels) and kinetics of systems that are otherwise based on nanoparticles. Moreover, the carbon SPs do not require doping with heteroatoms (as tested for N) for effective CO2 uptake (at 1 bar CO2 and 40 °C) and are suitablefor regeneration, following multiple adsorption/desorption cycles. Overall, we demonstrate porous SP carbon systems of low cost (precursor, fabrication, and processing) and superior activity (gas sorption and capture).

The use of nanomaterials and polymers from renewable resources is important in the search for sustainable alternatives to plastic-based packaging materials and films. In this work, self-supporting thin films prepared from derivatized and non-derivatized nanocellulose and cellulose derivatives were studied. The effect of drying temperature on the film-forming behavior of compositions comprising hydrophobically modified ethyl(hydroxyethyl)cellulose (EHEC), native microfibrillated cellulose (MFC) and nanocellulose made from methyl cellulose was determined. The interaction between the components was assessed from viscosity measurements made at different temperatures, the result being linked to a thermal-dependent association during liquid evaporation, and the subsequent barrier and film-forming properties. The effect of temperature on suspensions was clearly different between the materials, confirming that there were differences in interaction and association between EHEC–MFC and methyl nanocellulose–MFC compositions. The amphiphilic EHEC affected both the suspension homogeneity and the film properties. Air bubbles were formed under certain conditions and composition particularly in MFC films, dependent on the drying procedure. The presence of air bubbles did not affect the oxygen transmission rate or the oil and grease resistance. An increasing amount of MFC improved the oxygen barrier properties of the films.

openaire: EC/H2020/788489/EU//BioELCell There is an increased interest in renewable carbon as a source of materials, where lignin is expected to play a prominent role. This stems, partially, from new regulations aiming to achieve a cleaner and safer environment. Lignin, as a polyaromatic plant-derived biomolecule, is not only abundant but widely accessible in industrial streams. Due to recent developments in production scalability as well as promising application prospects, nanoscaled lignin particles have recently generated interest in the research and industrial communities. This review describes the main routes to prepare spherical lignin particles, highlighting aspects associated to their shape and topology as well as performance. We discuss the use of spherical lignin particles as dispersants and in the formulation of coatings, adhesives and composites, focusing on the advantages of the spherical shape and nanoscaled size. The state of the particles is furthermore compared in terms of their applicability in dry and wet forms. Finally, we discuss the sustainability, stability and degradation of lignin particles, which are issues that are critically important for any prospective use.

This work made use of Aalto University Bioeconomy Facilities and OtaNano─Nanomicroscopy Center Facilities. Bin Zhao is thanked for conducting the N2 adsorption–desorption experiments. T.Z. acknowledges funding from the Novo Nordisk Foundation (SUSCELL project, Reference Number: NNF17OC0027658), M.V. acknowledges funding from Fortum and Neste Foundation (grant no. 20200079), P.P. acknowledges funding from the Academy of Finland (grant no. 315768), and M.S. acknowledges funding from the Academy of Finland (grant no. 309324). Computational resources by CSC IT Centre for Science, Finland, and RAMI─RawMatTERS Finland Infrastructure are gratefully acknowledged. The authors are also grateful for the support by the FinnCERES Materials Bioeconomy Ecosystem and Photonics Research and Innovation (PREIN) flagship. Spherical lignin nanoparticles (LNPs) fabricated via nanoprecipitation of dissolved lignin are among the most attractive biomass-derived nanomaterials. Despite various studies exploring the methods to improve the uniformity of LNPs or seeking more application opportunities for LNPs, little attention has been given to the fundamental aspects of the solvent effects on the intrinsic properties of LNPs. In this study, we employed a variety of experimental techniques and molecular dynamics (MD) simulations to investigate the solvent effects on the intrinsic properties of LNPs. The LNPs were prepared from softwood Kraft lignin (SKL) using the binary solvents of aqueous acetone or aqueous tetrahydrofuran (THF) via nanoprecipitation. The internal morphology, porosity, and mechanical properties of the LNPs were analyzed with electron tomography (ET), small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), and intermodulation AFM (ImAFM). We found that aqueous acetone resulted in smaller LNPs with higher uniformity compared to aqueous THF, mainly ascribing to stronger solvent–lignin interactions as suggested by MD simulation results and confirmed with aqueous 1,4-dioxane (DXN) and aqueous dimethyl sulfoxide (DMSO). More importantly, we report that both LNPs were compact particles with relatively homogeneous density distribution and very low porosity in the internal structure. The stiffness of the particles was independent of the size, and the Young’s modulus was in the range of 0.3–4 GPa. Overall, the fundamental understandings of LNPs gained in this study are essential for the design of LNPs with optimal performance in applications.

Owing to their superior mechanical strength and structure similarity to the extracellular matrix, nanocelluloses as a class of emerging biomaterials have attracted great attention in three-dimensional (3D) bioprinting to fabricate various tissue mimics. Yet, when printing complex geometries, the desired ink performance in terms of shape fidelity and object resolution demands a wide catalogue of tunability on the material property. This paper describes surface engineered biomimetic inks based on cellulose nanofibrils (CNFs) and cross-linkable hemicellulose derivatives for UV-aided extrusion printing, being inspired by the biomimetic aspect of intrinsic affinity of heteropolysaccharides to cellulose in providing the ultrastrong but flexible plant cell wall structure. A facile aqueous-based approach was established for the synthesis of a series of UV cross-linkable galactoglucomannan methacrylates (GGMMAs) with tunable substitution degrees. The rapid gelation window of the formulated inks facilitates the utilization of these wood-based biopolymers as the feeding ink for extrusion-based 3D printing. Most importantly, a wide and tunable spectrum ranging from 2.5 to 22.5 kPa of different hydrogels with different mechanical properties could be achieved by varying the substitution degree in GGMMA and the compositional ratio between GGMMA and CNFs. Used as the seeding matrices in the cultures of human dermal fibroblasts and pancreatic tumor cells, the scaffolds printed with the CNF/GGMMA inks showed great cytocompatibility as well as supported the matrix adhesion and proliferative behaviors of the studied cell lines. As a new family of 3D printing feedstock materials, the CNF/GGMMA ink will broaden the map of bioinks, which potentially meets the requirements for a variety of in vitro cell-matrix and cell-cell interaction studies in the context of tissue engineering, cancer cell research, and high-throughput drug screening.

This study covers a green method to prepare hybrid lignocellulosic nanopapers by combining wood nanofibres (WNFs) and cellulose nanofibres (CNFs). The WNFs and CNFs behave synergistically to compensate for the drawbacks of each other resulting in enhanced hybrid nanopapers. The draining time of hybrid nanopapers was improved by up to 75% over CNF nanopaper, and the mechanical properties, modulus, strength and elongation, were respectively improved up to 35%, 90% and 180% over WNF nanopaper. Additionally, the water resistance of hybrid nanopapers was considerably improved with a water contact angle of 95°; the neat CNF nanopaper had a contact angle of 52°. The morphology of nanopapers, studied by electron microscopy, indicated that lignin acts as a matrix, which binds the nanofibres together and makes them impervious to external environmental factors, such as high humidity. The reported hybrid nanopapers are 100% bio-based, prepared by a simple and environmentally friendly processing route. Reported hybrid nanopapers can be used in novel applications such as gas barrier membranes and printable electronics.

Biomaterials of different nature have been and are widely studied for various biomedical applications. In many cases, biomaterial assemblies are designed to mimic biological systems. Although biomaterials have been thoroughly characterized in many aspects, not much quantitative information on the molecular level interactions between different biomaterials is available. That information is very important, on the one hand, to understand the properties of biological systems and, on the other hand, to develop new composite biomaterials for special applications. This work presents a systematic, quantitative analysis of self- and cross-interactions between films of collagen I (Col I), collagen IV (Col IV), laminin (LN-521), and cellulose nanofibrils (CNF), that is, biomaterials of different nature and structure that either exist in biological systems (e.g., extracellular matrices) or have shown potential for 3D cell culture and tissue engineering. Direct surface forces and adhesion between biomaterials-coated spherical micro-particles and flat substrates were measured in phosphate-buffered saline using an atomic force microscope and the colloidal probe technique. Different methods (Langmuir-Schaefer deposition, spin-coating, or adsorption) were applied to completely coat the flat substrates and the spherical micro particles with homogeneous biomaterial films. The adhesion between biomaterials films increased with the time that the films were kept in contact. The strongest adhesion was observed between Col IV films, and between Col IV and LN-521 films after 30 s contact time. In contrast, low adhesion was measured between CNF films, as well as between CNF and LN-521 films. Nevertheless, a good adhesion between CNF and collagen films (especially Col I) was observed. These results increase our understanding of the structure of biological systems and can support the design of new matrices or scaffolds where different biomaterials are combined for diverse biological or medical applications.

Three-dimensional (3D) printing has been an emerging technique to fabricate precise scaffolds for biomedical applications. Cellulose nanofibril (CNF) hydrogels have attracted considerable attention as a material for 3D printing because of their shear-thinning properties. Combining cellulose nanofibril hydrogels with alginate is an effective method to enable cross-linking of the printed scaffolds in the presence of Ca2+ ions. In this work, spherical colloidal lignin particles (CLPs, also known as spherical lignin nanoparticles) were used to prepare CNF-alginate-CLP nanocomposite scaffolds. High-resolution images obtained by atomic force microscopy (AFM) showed that CLPs were homogeneously mixed with the CNF hydrogel. CLPs brought antioxidant properties to the CNF-alginate-CLP scaffolds in a concentration-dependent manner and increased the viscosity of the hydrogels at a low shear rate, which correspondingly provide better shape fidelity and printing resolution to the scaffolds. Interestingly, the CLPs did not affect the viscosity at high shear rates, showing that the shear thinning behavior typical for CNF hydrogels was retained, enabling easy printing. The CNF-alginate-CLP scaffolds demonstrated shape stability after printing, cross-linking, and storage in Dulbecco's phosphate buffer solution (DPBS +) containing Ca2+ and Mg2+ ions, up to 7 days. The 3D-printed scaffolds showed relative rehydration ratio values above 80% after freeze-drying, demonstrating a high water-retaining capability. Cell viability tests using hepatocellular carcinoma cell line HepG2 showed no negative effect of CLPs on cell proliferation. Fluorescence microscopy indicated that HepG2 cells grew not only on the surfaces but also inside the porous scaffolds. Overall, our results demonstrate that nanocomposite CNF-alginate-CLP scaffolds have high potential in soft-tissue engineering and regenerative-medicine applications.

All-cellulose composites were prepared by dispersing kraft fibers in a matrix made from pulp dissolved in NaOH-water. To hydrophobize the composite surface while maintaining the material fully bio-based and biodegradable, layer-by-layer deposition of cationic starch and carnauba wax was performed. Various options of surface coating, drying, and curing were tested, including partial and complete melting of the wax. The composite surface was characterized by water contact angle, roughness and scanning electron microscopy, and material properties by adsorption and absorption of water (in vapor and liquid form) and tensile testing. The highest water contact angle was obtained when the layer-by-layer deposition was performed by dipping the dry composite into cationic starch solution, then in wax dispersion, and partially melting the wax after coating. However, it was demonstrated that the dipping approach was detrimental to material tensile properties, due to heterogeneous swelling of cellulose during the treatment and multiple drying sequences. Process optimization via spraying resulted in composites with Young's modulus of 6 GPa and hydrophobic surface with water contact angle 122 degrees C.

In this work, we present a new all-cellulose approach for modifying and functionalizing textiles. The use of 3D-printing and two acetylated cellulose derivatives, rigid cellulose acetate (CA) and flexible acetoxypropyl cellulose (APC), on cellulosic fabrics were studied. In addition, prototypes were generated using a design-driven approach. The interactions of cellulose derivatives with cellulose were assessed by quartz crystal microbalance with dissipation monitoring (QCM-D). 3D-printing of cellulosic materials on cellulosic fabrics was performed using a direct-write method by printing cellulose derivatives on woven and knitted cotton and woven viscose fabrics. The adhesion of the printed structures was evaluated via peeling and washability tests. The results indicated that although both cellulose derivatives had a positive attraction towards the cellulose substrate, CA had higher affinity and good adhesion properties, whereas the more branched molecular structure of APC was less firmly attached to cellulosic material. The applicability of 3D-printing cellulosic materials for textile modification and functionalization was assessed through iterative prototyping. Visual effects and functional surface structures were demonstrated. Utilization of 3D-printing of cellulosic materials for surface tailoring of cellulosic textiles, eliminates labour intensive processing or external glues and may enable new and simple customization processes with minimized material usage. Keywords: 3D-printing, Cellulose derivatives, Cellulose acetate, Acetoxypropyl cellulose, Design-driven, Prototyping

Antibacterial properties of wood structural components and extractives were investigated against methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli O157:H7 by placing bacterial inoculum on the model surfaces and incubating them for 2, 4, and 24 h. After incubation, the amount of viable bacteria on the surfaces was studied. The film coverage and thickness were evaluated with atomic-force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The extracts were analyzed with gas chromatography–mass spectrometry (GC-MS). The results showed that films fully covered the glass surfaces. The XPS results confirmed the analysis of GC-MS, which revealed more similarities between the extractives of pine heartwood and spruce heartwood than between pine heartwood and pine sapwood. Only the pine heartwood extract showed an antibacterial effect against E. coli O157:H7. In contrast, MRSA was susceptible to all of the extracts and milled wood lignin (MWL).

Protection from liquid water and UV radiation are equally important, and a sophisticated approach is needed when developing surface coatings that preserve the natural and well-appreciated aesthetic appearance of wood. In order to prevent degradation and prolong the service life of timber, a protective coating was assembled using carnauba wax particles and zinc oxide nanoparticles via layer-by-layer deposition in water. For this purpose, a facile sonication route was developed to produce aqueous wax dispersion without any surfactants or stabilizers. The suspension was stable above pH 4 due to the electrostatic repulsion between the negatively charged wax particles. The particle size could be controlled by the initial wax concentration with average particle sizes ranging from 260 to 360 nm for 1 and 10 g/L, respectively. The deposition of wax particles onto the surface of spruce wood introduced additional roughness to the wood surface at micron level, while zinc oxide provided nano roughness and UV-absorbing properties. In addition to making wood superhydrophobic, this novel multilayer coating enhanced the natural moisture buffering capability of spruce. Moreover, wood surfaces prepared in this fashion showed a significant reduction in color change after exposure to UV light. A degradation of the wax through photocatalytic activity of the ZnO particles was measured by FTIR, indicating that further studies are required to achieve long-term stability. Nevertheless, the developed coating showed a unique combination of superhydrophobicity and excellent moisture buffering ability and some UV protection, all achieved using an environmentally friendly coating process, which is beneficial to retain the natural appearance of wood and improve indoor air quality and comfort.

Environmental benign cellulosic textiles are hampered by their tendency to absorb water, which restricts their use in functional clothing. Herein we describe a method to functionalize textile surfaces using thin, open coatings based on natural wax particles and natural polymers rendering cellulosic fabrics water-repellent while retaining their feel and breathability. The impact of curing temperature, cationic polymer and fabric properties on wetting and long-term water-repellency were studied using contact angle measurements and scanning electron microscopy. The wetting properties were correlated to roughness of the textiles using white light interferometer. X-ray photoelectron spectroscopy revealed the surface chemical composition, leading to fundamental understanding of the effect of annealing on the wax layer. Breathability was evaluated by water vapor permeability. The optimal curing temperature was 70 °C. The developed coating performed well on different natural textiles, and better than commercial alternatives. A set of garment prototypes were produced using the coating.

Lignin has interesting functionalities to be exploited in adhesives for medicine, foods and textiles. Nanoparticles (NPs) &lt, 100 nm coated with poly (L-lysine), PL and poly(L-glutamic acid) PGA were prepared from the laccase treated lignin to coat nanocellulose fibrils (CNF) with heat. NPs ca. 300 nm were prepared, &beta, casein coated and cross-linked with transglutaminase (Tgase) to agglutinate chamois. Size exclusion chromatography (SEC) and Fourier-transform infrared (FTIR) spectroscopy were used to characterize polymerized lignin, while zeta potential and dynamic light scattering (DLS) to ensure coating of colloidal lignin particles (CLPs). Protein adsorption on lignin was studied by quartz crystal microbalance (QCM). Atomic force microscopy (AFM) was exploited to examine interactions between different polymers and to image NPs with transmission electron microscopy (TEM). Tensile testing showed, when using CLPs for the adhesion, the stress improved ca. 10 and strain ca. 6 times compared to unmodified Kraft. For the &beta, casein NPs, the values were 20 and 8, respectively, and for the &beta, casein coated CLPs between these two cases. When NPs were dispersed in adhesive formulation, the increased Young&rsquo, s moduli confirmed significant improvement in the stiffness of the joints over the adhesive alone. Exploitation of lignin in nanoparticulate morphology is a potential method to prepare bionanomaterials for advanced applications.

A scalable tubular flow reactor was designed and developed for the continuous formation of colloidal lignin particles (CLPs). The reactor consists of a series of tubes, inside which many static mixing elements are equipped to aid in the formation of a homogeneous dispersion of CLPs. The colloids were formed instantaneously through self-assembly upon the addition of the lignin solution into water. The effects of flowrate, length of the tubes and static mixing elements on the particle size, stability and CLP yield after drying were determined. It was found that a higher flowrate of lignin solution within the testing range of 32-240 mL/min resulted in smaller sized CLPs. Optimizations of the mixing length and the static mixing elements to 3 m and at least 1 m, respectively, could ensure an efficient mixing, thus resulting in CLP dispersions with smaller size of lignin particles (200 nm – 400 nm) and high lignin concentrations (up to 2.8 wt. %) along with yields up to 95 %. The TEM images indicated that the formed colloids are composed of lignin particles of regular sphere shape and with good stability. The tubular reactor offers better control of particle size which ensures the formation of colloidal dispersions with narrower particle size distribution in comparison to a stirred mixer reactor. Furthermore, using a tubular reactor enables the continuous production of CLPs, making it suitable for scale up and industrial applications.

Brittleness has hindered commercialization ofcellulose nanofibril (CNF)films. The use of syntheticpolymers and plasticizers is a known detour that impairsbiodegradability and carbon footprint of the product. Herein,we utilize a variety of softwood Kraft lignin morphologies toobtain strong and ductile CNF nanocompositefilms. Anoptimum 10 wt % content of colloidal lignin particles (CLPs)producedfilms with nearly double the toughness compared toa CNFfilm without lignin. CLPs rendered thefilms waterproof, provided antioxidant activity and UV-shieldingwith better visible light transmittance than obtained withmicroscopy, dynamic water sorption analysis, and tp-DSC that homogeneously distributed CLPs act as ball bearing lubricating and stress transferring agents in the CNF matrix. Overall, our results open new avenues for the utilization of lignin nanoparticles in biopolymer composites equipped with versatile functionalities for applications in food packaging, water purification, and biomedicine.

Cellulose nanofiber (CNF) aerogels offer excellent thermal insulation properties, but high flammability restricts their application. In this study, CNF aerogels were prepared by incorporating sodium bicarbonate (SBC), which effectively improved the fire retardancy without compromising the thermal conductivity of the aerogels, which was only 28 mW m-1 K-1. The minimum burning velocity of flame-retardant aerogels was 0.20 cm s-1 at 40 wt % of SBC, which is significantly lower compared to 5.84 cm s-1 of pure CNF aerogels. At the threshold concentration of 20 wt % SBC, the flame-retardant aerogel demonstrated flameless pyrolysis along with enhanced char formation. SBC additionally provides control over the microporosity and morphology, due to the concentration-dependent formation of lamellar layers during the preparation of aerogels. Overall, this work describes an efficient method for preparing flame-retardant CNF aerogels that could lay the foundation for next-generation bio-based insulation materials.

Cellulose nanopapers, known for excellent mechanical properties, loses 90% of their stiffness in the wet conditions. In this study, we attempt to improve the wet mechanical properties of cellulose nanopaper by incorporating polyurethane by a novel and ecofriendly method. Water based PU was dispersed along with CNFs in water and hybrid nanopapers were prepared by draining water under vacuum followed by forced drying. These hybrid nanopapers have a gradient interpenetrating structure with PU concentrated towards one side and CNFs towards the other, which was confirmed by scanning electron microscopy, x-ray photoelectron spectroscopy and contact angle measurements. Because of this, the nanopapers are water resistant on one surface (PU rich side) and hydrophilic on the other (cellulose rich side), making them stereoselectively water resistant. When wetted with water on the PU side, the hybrid nanopaper with 10% PU is able to retain 65% modulus; on the other hand, the reference retains only 10% of the modulus. Similar results are seen in the tensile and the yield strength. Additionally, the hybrid nanopapers have higher elongation and improved thermal stability. The reported material is relevant to the applications such as flexible electronics and transparent displays.

In this experiment, the influence of the morphology and surface characteristics of cellulosic nanoparticles (i.e., cellulose nanocrystals [CNCs] and cellulose nanofibers [CNFs]) on oil-in-water (o/w) emulsion stabilization was studied using non-modified or functionalized nanoparticles obtained following deep eutectic solvent (DES) pre-treatments. The effect of the oil-to-water ratio (5, 10, and 20 wt.-% (weight percent) of oil), the type of nanoparticle, and the concentration of the particles (0.05&ndash, 0.2 wt.-%) on the oil-droplet size (using laser diffractometry), o/w emulsion stability (via analytical centrifugation), and stabilization mechanisms (using field emission scanning electron microscopy with the model compound&mdash, i.e., polymerized styrene in water emulsions) were examined. All the cellulosic nanoparticles studied decreased the oil droplet size in emulsion (sizes varied from 22.5 &micro, m to 8.9 &micro, m, depending on the nanoparticle used). Efficient o/w emulsion stabilization against coalescence and an oil droplet-stabilizing web-like structure were obtained only, however, with surface-functionalized CNFs, which had a moderate hydrophilicity level. CNFs without surface functionalization did not prevent either the coalescence or the creaming of emulsions, probably due to the natural hydrophobicity of the nanoparticles and their instability in water. Moderately hydrophilic CNCs, on the other hand, distributed evenly and displayed good interaction with both dispersion phases. The rigid structure of CNCs meant, however, that voluminous web structures were not formed on the surface of oil droplets, they formed in flat, uniform layers instead. Consequently, emulsion stability was lower with CNCs, when compared with surface-functionalized CNFs. Tunable cellulose nanoparticles can be used in several applications such as in enhanced marine oil response.

Galactose oxidase (GaO)-catalyzed oxidation of the terminal galactosyl groups of guar galactomannan (GM) and tamarind seed galactoxyloglucan (XG) results in cross-linking of these polysaccharides via hemiacetal bonds and formation of elastic hydrogels (GMox and XGox, respectively), and enables the formation of aerogels. Nanofibrillated cellulose (NFC) was added at varying quantities to the aqueous GM and XG solutions and was entrapped in the three-dimensional structure of polysaccharides by enzyme mediated gelation. Addition of NFC up to 25% did not hinder the enzyme activity. The reinforcing effect of NFC on hydrogels was measured with rheometer and texture analyzer. The GMox hydrogels with 25% NFC exhibited higher elastic modulus than corresponding XGox hydrogels, but the latter showed higher compressive modulus. On the other hand, the lyophilized GMox aerogels containing 25% NFC showed the highest compressive modulus, 167 kPa. The reinforcing effect of NFC depended on the type of polysaccharides (GM/XG) and state of the material (hydro- or aerogel). Viewing the aerogels with focused ion beam scanning electron microscopy showed that the pores were approximately 125–250 μm in diameter.

The hygroscopicity of a wooden material or the ability to absorb, store and release moisture helps to naturally regulate the indoor climate by dampening humidity variations and avoiding extremes. This phenomenon, known as moisture buffering, is an energy-efficient way of moderating moisture levels in a living space, improving air quality, and influencing the health and comfort of the occupants. This work focused on developing a surface treatment that preserves the natural ability of timber to buffer moisture vapor whilst increasing the resistance to liquid water. For this purpose we suggest a method based on a natural non-continuous coating of hydrophobic Carnauba wax particles. The coating was compared, in terms of water repellency and moisture buffering efficiency, to a continuous wax film and conventional coating methods like lacquer and linseed oil. The resistance of the surfaces to liquid water was studied by Contact Angle measurement. Moisture Buffering experiments were conducted by exposing the surfaces to cyclic changes in relative humidity. It was found that coating with wax particles resulted in more hydrophobic surfaces with enhanced moisture buffering ability, whilst the rest of the coatings examined either reduced moisture buffering drastically (wax film, lacquer) or were not sufficiently hydrophobic (linseed oil).

All-polysaccharide composite films were prepared from native, unmodified cellulose nanofibrils (CNF) mixed with various natural water-soluble polysaccharides like carboxymethyl cellulose, galactoglucomannan, xyloglucan and guar gum. Composite films were manufactured by pressurized filtration and hot pressing. The mechanical properties of the films were systematically evaluated in the dry and the wet state. GG was furthermore selectively oxidized using galactose oxidase (EC 1.1.3.9), and the effect of the degree of oxidation on the final composite film properties was shown. It was found that all the tested polysaccharides increased the strength and toughness of the dry composite films at 2 weight percent (wt.%) addition to CNF. After soaking the samples for 24 h in water, striking differences between the samples were found: already at 2 wt.% CMC the wet strength of the composite films diminished, while the uncharged polysaccharides improved the wet strength. For example, the addition of 2 wt.% GGM increased Young's modulus by a factor of 1.3, the tensile strength by a factor of 2.8, and the toughness by a factor of 3.4. The results are discussed in relation to the amount of water absorbed in the films and possible reasons for the improved properties are suggested.

Superabsorbents are highly appealing materials for use in cleaning up oil and chemical spills. However, the development of a low-cost, highly efficient superabsorbent remains a major challenge. This paper demonstrates a straightforward method of producing a cellulose nanofibril aerogel that is low-cost, ultralight, highly porous, hydrophobic, and reusable superabsorbing cellulose nanofibril aerogel from recycled waste fibers using a simple, environmentally friendly nanofibrillation treatment involving deep eutectic solvent and freeze-drying. Nanofibrillation and hydrophobic modification (silylation) of waste cellulose fibers resulted in nanofibril sponges with ultralow density (0.0029 g/cm³) and high porosity (up to 99.81%) after freeze-drying. These sponges exhibited excellent absorption performances for various oils and organic solvents and were reusable. In particular, the nanofibril aerogels showed selectivity in absorbing marine diesel oil from an oil–water mixture and possessed ultrahigh absorption capacities of up to 142.9 g/g, much higher than those of the commercial absorbent materials (i.e., polypropylene-based material) (8.1–24.6 g/g) that were used as references. The absorbed oil could easily be recovered by means of simple mechanical squeezing. In addition, the nanofibril sponges exhibited excellent reusability, maintaining a high capacity to absorb diesel oil for at least 30 cycles at 71.4–81.0% of capacity compared to a fresh absorbent. The above-mentioned advantages make cellulose nanofibril superabsorbents created from recycled waste cellulose fibers promising material for cleaning oil and chemical spills.

Native cellulose nanofibrils (CNF) were prepared from bleached birch pulp without any chemical or enzymatic pretreatment. These CNF were modified by adsorption of a small amount of water-soluble polysaccharides and used to prepare nanopapers, which were processed into composites by lamination with an epoxy resin and subsequently cured. The results were compared to the properties of composites prepared using bacterial cellulose nanopapers, since bacterial cellulose constitutes highly pure and crystalline cellulose. It was found that both types of nanopapers significantly improved both the thermal stability and mechanical properties of the epoxy resin. As anticipated, addition of only 2 wt% of water-soluble polysaccharides efficiently hindered crack-propagation within the nanopaper and significantly improved the tensile strength and work of fracture compared to composites containing a conventional nanopaper reinforcement. The mechanical properties of the composites thus reflected the improvement of the nanopaper properties by the polysaccharides. Moreover, it was possible to predict the properties of the final composite from the mechanical performance of the nanopapers.

Herein we present a simple method to render cellulosic materials highly hydrophobic while retaining their breathability and moisture buffering properties, thus allowing for their use as functional textiles. The surfaces are coated via layer-by-layer deposition of two natural components, cationic poly-l-lysine and anionic carnauba wax particles. The combination of multiscale roughness, open film structure, and low surface energy of wax colloids, resulted in long-lasting superhydrophobicity on cotton surface already after two bilayers. Atomic force microscopy, interference microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy were used to decouple structural effects from changes in surface energy. Furthermore, the effect of thermal annealing on the coating was evaluated. The potential of this simple and green approach to enhance the use of natural cellulosic materials is discussed.

Self-organized multilayer films were formed by sequential addition of oppositely charged cellulose I nanoparticles. The all-cellulosic multilayers were prepared via adsorption of cationicially modified cellulose nanofibrils (cat NFC) and anionic short crystalline cellulose (CNC) at pH 4.5 and pH 8.3. The properties and build-up behavior of layer-by-layer-constructed films were studied with microgravimetry (QCM-D) and the direct surface forces in these systems were explored with colloidal probe microscopy to gain information about the fundamental interplay between cat NFC and anionic CNC. The importance of the first layer on the adsorption of the consecutive layers was demonstrated by comparing pure in situ adsorption in the QCM-D with multilayer films made by spin coating the first cationic NFC layer and then subsequently adsorbing the following layers in situ in the QCM-D chamber. Differences in adsorbed amount and viscoelastic behavior were observed between those two systems. In addition, a significant pH dependence of cat NFC charge was found for both direct surface interactions and layer properties. Moreover the underlying cellulose layer in multilayer film was established to influence the surface forces especially at lower pH, where the cat NFC chains extensions were facilitated and overall charge was affected by the cationic counterpart within the layers. This enhanced understanding the effect of charge and structure on the interaction between these renewable nanoparticles is valuable when designing novel materials based on nanocellulose.

The development of materials that combine the excellent mechanical strength of cellulose nanofibrils (CNF) with the lubricating properties of hyaluronic acid (HA) is a new, promising approach to cartilage implants not explored so far. A simple, solvent-free method to produce a very lubricating, strong cellulosic material by covalently attaching HA to the surface of CNF films is described in this work. A detailed analysis of the tribological properties of the CNF films with and without HA is also presented. Surface and friction forces at micro/nanoscale between model hard surfaces (glass microspheres) and the CNF thin films were measured using an atomic force microscope and the colloid probe technique. The effect of HA attachment, the pH and the ionic strength of the aqueous medium on the forces was examined. Excellent lubrication was observed for CNF films with HA attached in conditions where the HA layer was highly hydrated. These results pave the way for the development of new nanocellulose-based materials with good lubrication properties that could be used in biomedical applications. (C) 2015 Elsevier B.V. All rights reserved.

Nanofibrillated cellulose (NFC) is increasingly utilized in materials and biomedical applications consequently increasing interest in the modification of its surface properties. Besides modification using polyelectrolytes and polysaccharides, NFC can be combined with solid particles enabling formation of fibril network loaded with particles. Use of particles enabling easy functionalization could be beneficial for the development of hybrid structures, and lead to preparation of nanocomposites and functional materials. In order to explore interactions related to preparation of such structures, the interactions between nanosized precipitated calcium carbonate (nanoPCC) and nanoclay particles and NFC were examined by observing adsorption of the particles on NFC substrate using a quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM) imaging. By a treatment with carboxymethylated cellulose (CMC), the anionicity of the NFC substrate could be increased, providing an additional tool to affect the interplay between NFC and the inorganic particles. For slightly cationic nanoPCC particles an increase in the anionicity of the NFC by the CMC treatment increased the affinity, while the opposite was true for anionic nanoclay. Additionally, for interactions between nanoclay and NFC, dispersion stability was an important factor. QCM-D was successfully used to examine the adsorption characteristics of nanoparticles although the technique is commonly used to study the adsorption of thin polymer layers. Distinct adsorption characteristics were observed depending on the nanoparticle used; nanoclay particles deposited as a thin layer, whereas nanoPCC particles formed clusters.

Pigment particles used in paper coatings are typically of micrometer size and consequently the thickness of the coatings is, even at its lowest, in micrometer scale. Progress in nanotechnology has given way to the development of nanosized materials to be used in coatings, yet their exploitation has not been studied to a great extent. This study examines utilization of nanosized precipitated calcium carbonate (nanoPCC) particles in nanoscale thin coating layers. In contrast to commonly used coatings, a thin nanoparticle-based coating was targeted to change the substrate surface characteristics via controlled surface structure rather than via high coat weight. A novel approach for stabilizing and modifying the nanoPCC particles with pectin and alkenyl succinic anhydride (ASA) was utilized and a nanoparticle coating with uniform particle distribution was created. The coating applied on paper substrate was hydrophobic, having a water contact angle of 125°. Particle surface modification provided dispersion stability, enabling control of the coating layer structure. The introduced concept provides a new approach to paper coatings utilizing controlled deposition of nanoparticles with extremely low coat weight, yet having high impact on substrate surface properties. Additionally, as paper is an environmentally sound product, the approach to form a controllable nanostructure on a green substrate has potential in applications outside the traditional paper products.

This paper deals, with cationically modified NanoFibrillar Cellulose (cat NFC), obtained by reacting a dissolving pulp with 2,3-epoxypropyl trimethylammonium chloride (EPTMAC). The cat NFC was thoroughly characterized in terms of morphology and physical properties. The dimensions of individual cellulose nanofibrils were determined by atomic force microscopy (AFM) imaging in water and in air. Fibrils as thin as 0.8–1.2 nm were observed in water. The fibril diameter changed upon drying and the average size was further quantified by image analysis. The experiments showed the importance of characterizing nanocellulosic materials in situ before drying. The fibril size in air was confirmed by cryogenic transmission electron microscopy (cryo-TEM), and it was found to be 2.6–3.0 nm. Smooth ultrathin films of cationic NFC were prepared by spincoating on silica substrates. The effect of electrolyte concentration and pH on swelling of the cationic NFC film was studied using a quartz crystal microbalance with dissipation. The results showed that at pH = 8 the cat NFC film was insensitive to electrolyte changes while at pH = 4.5, the water content of the film decreased with increasing ionic strength. The electrophoretic mobility measurements showed a cationic zeta potential for the cat NFC that decreased at increasing pH, verifying the swelling behaviour.

Silica nanoparticles are used in various applications including catalysts, paints and coatings. To reach an optimal performance via stability and functionality, in most cases, the surface properties of the particles are altered using complex procedures. Here we describe a simple method for surface modification of silica nanoparticles (SNP) using sequential adsorption of oppositely charged components. First, the SNPs were made cationic by adsorption of a cationic polyelectrolyte. Poly(allylamine hydrochloride) (PAH) and polyethyleneimine (PEI) were chosen as polycations to investigate the difference between a linear and a branched polyelectrolyte. Next, the dispersion of cationic SNPs was combined with an anionic alkyl ketene dimer (AKD) emulsion. Using this approach cationic, hydrophobic silica particle dispersions were produced. Dynamic light scattering, contact angle measurements and atomic force microscopy (AFM) were used for analyzing the particle and coating layer properties. The chosen polyelectrolyte affected the structure of the dispersion. The layer build-up was studied in detail using a quartz crystal microbalance with dissipation monitoring (QCM-D). The adsorption and layer properties of the cationic polyelectrolytes adsorbed on silica as well as the affinity of AKD to this layer were explored. The application possibilities of the modified particle dispersions were demonstrated by preparing paper and silica surfaces with tailored properties, such as elevated surface hydrophobicity, using an ultrathin coating layer.

This paper combines theoretical considerations with experimental evidence to explain the behavior of cellulose when exposed to different media. The observations are explained based on the amphiphilic character of the cellulose molecule and fundamental physicochemical phenomena. Nanofibrillated cellulose was chosen to demonstrate the phenomena since due to its high surface area the effects at issue are pronounced. X-Ray photoelectron spectroscopy and contact angle measurements were used to demonstrate the chemical and energetical changes taking place on the cellulose surface, and atomic force microscopy was used to follow nanoscale structural changes. Due to its hydrophilicity cellulose is well dispersed in water. However, when exposed to non-polar media like air or organic solvents cellulose undergoes partly irreversible reorganization like aggregation or surface passivation in order to find the energetically most favorable state. We show that when NFC is dried directly from water it aggregates strongly and accumulates a very high amount of non-cellulosic material on the surface. Very similar effects also occur when using non-polar media like toluene. Hence, both the reactivity and nanoscale structure are lost. In contrast, NFC retains its reactivity and nano-scaled structure in amphiphilic media like dimethyl acetamide as is confirmed with a simple silylation reaction. We conclude that the interfacial phenomenon is general for cellulosic material but has the most practical impact on applications of nanoscaled cellulose or ultrathin cellulose films.

Different types of microfibrillated cellulose (MFC) and fines suspensions were produced, characterized, and then added to a papermaking pulp suspension. High and medium molar mass cationic polyelectrolytes were used as fixatives. The drainage behavior of the pulp suspensions with additives were evaluated against the strength properties of hand sheets made thereof. The effects of salt concentration, pH, fixative type, dosage and type of fibrillar material on drainage were examined. All the MFC and fines samples produced had clearly different properties due to their dissimilar production methods, and they also introduced specific responses on the measured drainage and paper strength. Generally, the addition of MFC decreased the drainage rate of pulp suspension and increased the strength of paper. However, it was shown that by optimum selection of materials and process conditions an enhancement of the strength properties could be achieved without simultaneously deteriorating the drainage.

The adsorption of cationic polyelectrolytes (C-PAMs and PDACMAC) with different charge densities and molecular weights on silica and cellulose model surfaces was examined using a quartz crystal microbalance with dissipation, QCM-D. The conformation and viscoelastic properties of the adsorbed polyelectrolyte layers were studied by modelling the data with the Q-Tools program. When comparing the adsorption behavior on cellulose and silica a clear difference both in adsorption kinetics of polyelectrolytes and the viscoelastic properties of the formed polyelectrolyte film was observed. On cellulose the polyelectrolyte films were viscous and more dissipative at the beginning of the adsorption but when the adsorption proceeded the layers became more rigid and stiffer, in contrast to the behavior on silica.

The adsorption of laccases and ferulic acid on a lignin substrate has been studied using a quartz crystal microbalance with dissipation (QCM-D) and an atomic force microscope (AFM). Two different additional strategies were applied: ferulic acid was added after laccase pretreatment, or coadsorbed together with laccase. The effect of two laccases isolated from Trametes hirsuta and Melanocarpus albomyces was compared on lignin activation. The QCM-D results were also compared against bulk experiments on chemithermomechanical pulp. The two laccases affected the adsorption of ferulic acid differently. Adsorption of T. hirsuta laccase was not observed, while the adsorption of M. albomyces laccase was obvious. However, both laccases still activated lignin and the amount of ferulic acid adsorbed was significantly higher on laccase-activated lignin than on the non-activated one. Rinsing after activation removed some slightly bound laccase from the substrate and decreased the adsorbed amount of subsequently added ferulic acid. Interestingly, only T. hirsuta laccase could catalyse the lasting attachment of polymerised ferulic acid onto lignin. The QCM-D and AFM results correlated with the findings of studies concerning bonding of ferulic acid on chemithermomechanical pulp. Thus, this approach is useful in studying the behaviour of enzymes on lignin substrates.

The adsorption of polyelectrolyte (PE) multilayers and complexes, obtained from both high- and low-charge polyelectrolytes, was studied on silica and on cellulose model surfaces by quartz crystal microbalance with dissipation (QCM-D). The film properties acquired with the different strategies were compared. When polyelectrolytes were added on an oppositely charged surface in sequence to form multilayers both the change in frequency and dissipation increased. The changes in frequency and dissipation were clearly higher if low-charge PEs were used in the multilayer formation. The substrate, silica or cellulose, did not affect the adsorption behaviour of low-charge PEs and only minor differences were seen in the adsorbed amounts and changes in dissipation of high-charge PEs between SiO2 and cellulose. The complexes formed by low-charge PEs had higher changes in frequency and dissipation at low ionic strength on both surfaces, while the complexes formed from high-charge polyelectrolytes adsorbed more at high salt concentration. The complexes of low-charge polyelectrolytes adsorbed more on silica, while the complexes formed by high-charge PEs formed thicker layers on cellulose. The charge ratio had a significant effect on the adsorption and the highest changes in frequency and dissipation were obtained in the anionic/cationic charge ratio of 0.5–0.6. Generally, the multilayers and complexes formed by low-charge polyacrylamides adsorbed highly and formed rather thick layers on both surfaces, unlike the high-charge PEs which formed thin layers using either one of the addition techniques.

The aim of this work was to investigate the morphological and structural changes associated with mercerization of cellulose fibres with combined confocal Raman and atomic force microscopy (AFM). During mercerization the alkali induces a change in polymorphic lattice from cellulose I to II. This was observed by confocal Raman spectroscopy from cellulose samples treated with 10, 15 and 25% aqueous sodium hydroxide solution. AFM images from the same samples illustrated that microfibrils were swollen and more granular in cellulose II than in cellulose I. Raman spectral images in plane and depth directions showed that the polymorphous cellulose structure was uniform throughout the cell wall, whereas the microfibril orientation varied between fibre cell wall layers. The changes in microfibril orientation on the sample surfaces were confirmed by AFM images measured from the same sample position.

Native cellulose model films containing both amorphous and crystalline cellulose I regions were prepared by spin-coating aqueous cellulose nanofibril dispersions onto silica substrates. Nanofibrils from wood pulp with low and high charge density were used to prepare the model films. Because the low charged nanofibrils did not fully cover the silica substrates, an anchoring substance was selected to improve the coverage. The model surfaces were characterized using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The effect of nanofibril charge density, electrolyte concentration, and pH on swelling and surface interactions of the model film was studied by quartz crystal microbalance with dissipation (QCM-D) and AFM force measurements. The results showed that the best coverage for the low charged fibrils was achieved by using 3-aminopropyltrimethoxysilane (APTS) as an anchoring substance and hence it was chosen as the anchor. The AFM and XPS measurements showed that the fibrils are covering the substrates. Charge density of the fibrils affected the morphology of the model surfaces. The low charged fibrils formed a network structure while the highly charged fibrils formed denser film structure. The average thickness of the films corresponded to a monolayer of fibrils, and the average rms roughness of the films was 4 and 2 nm for the low and high charged nanofibril films, respectively. The model surfaces were stable in QCM-D swelling experiments, and the behavior of the nanofibril surfaces at different electrolyte concentrations and pHs correlated with other studies and the theories of Donnan. The AFM force measurements with the model surfaces showed well reproducible results, and the swelling results correlated with the swelling observed by QCM-D. Both steric and electrostatic forces were observed and the influence of steric forces increased as the films were swelling due to changes in pH and electrolyte concentration. These films differ from previous model cellulose films due to their chemical composition (crystalline cellulose I and amorphous regions) and fibrillar structure and hence serve as excellent models for the pulp fiber surface.

In this paper cellulose nanofibrils were used together with a cationic polylelectrolyte, poly(amideamine) epichlorohydrin (PAE), to enhance the wet and the dry strength of paper. The adsorption of nanofibrils and PAE on cellulose model surfaces was studied using quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy (AFM). The differences in fibril and polyelectrolyte adding strategies onto cellulose fibres were studied by comparing layer-structures and nano-aggregates formed by the nanofibrils and PAE. The results showed that when PAE was first adsorbed on the model fibre surface a uniform and viscous layer of nanofibrils could be adsorbed. When PAE and nanofibrils were adsorbed as cationic aggregates a non-uniform and more rigid layer was adsorbed. Paper sheets were prepared using both the bi-layer and nano-aggregate adding strategy of the nanofibrils and PAE. When PAE and nanofibrils were adsorbed on pulp fibres as a bi-layer system significant increase in both wet and dry tensile strength of paper could be achieved even at low added amounts of PAE. When the substances were added as nano-aggregates the improvements in paper strength properties were not as significant. Bulk and surface nitrogen content analyses of the paper samples showed that the adding strategy does not affect the total adsorbed amount of PAE but it has a strong effect on distribution of substances in the paper matrix which has a crucial effect on paper wet and dry strength development.

The primary aim of this work was to obtain a better understanding of the colloidal interactions in the wet-end of paper machines that use thermomechanical pulp. Adsorption of colloidal extractives and dissolved hemicelluloses derived from Norway spruce (Picea abies) on model surfaces of cellulose, lignin and extractives was studied, using a quartz crystal micro-balance with dissipation (QCM-D), The goal of the study was to clarify how colloidal extractives and dissolved hemicelluloses interact with fiber components and how these interactions depend on e.g. peroxide bleaching and ionic strength. Dissolved hemicelluloses adsorbed most extensively on cellulose. They also adsorbed on extractives but there was no significant affinity towards lignin. Adsorption on cellulose and extractives increased with increasing ionic strength. Adsorption of electrostatically stabilized colloidal extractives was the largest on cellulose and extensive also on lignin. It increased on both surfaces with increasing ionic strength. These colloids did not adsorb on the extractive surface. The adsorption of colloidal extractives on cellulose and lignin decreased when were sterically stabilized with dissolved hemicelluloses. On the other hand, the sterically stabilized colloids seemed to adsorb on extractives. If the dissolved hemicelluloses were adsorbed also on substrate surfaces, the subsequent adsorption of sterically stable colloidal dispersion was almost completely prevented. This effect was most pronounced on cellulose.

The environmental cues received by the cells from synthetic substrates in vitro are very different from those they receive in vivo. In this study, we applied the LangmuireSchaefer (LS) deposition, a variant of LangmuireBlodgett technique, to fabricate a biomimetic microenvironment mimicking the structure and organization of native Bruch's membrane for the production of the functional human embryonic stem cell derived retinal pigment epithelial (hESC-RPE) cells. Surface pressure-area isotherms were measured simultaneously with Brewster angle microscopy to investigate the self-assembly of human collagens type I and IV on air-subphase interface. Furthermore, the structure of the prepared collagen LS films was characterized with scanning electron microscopy, atomic force microscopy, surface plasmon resonance measurements and immunofluorescent staining. The integrity of hESC-RPE on double layer LS films was investigated by measuring transepithelial resistance and permeability of small molecular weight substance. Maturation and functionality of hESC-RPE cells on double layer collagen LS films was further assessed by RPE-specific gene and protein expression, growth factor secretion, and phagocytic activity. Here, we demonstrated that the prepared collagen LS films have layered structure with oriented fibers corresponding to architecture of the uppermost layers of Bruch's membrane and result in increased barrier properties and functionality of hESC-RPE cells as compared to the commonly used dip-coated controls.

Hydrogen peroxide is the product of various enzymatic reactions, and is thus typically utilized as the analyte in biosensors. However, its detection with conventional materials, such as noble metals or glassy carbon, is often hindered by slow kinetics and biofouling of the electrode. In this study electrochemical properties and suitability to peroxide detection as well as ability to resist biofouling of Pt-doped ta-C samples were evaluated. Pure ta-C and pure Pt were used as references. According to the results presented here it is proposed that combining ta-C with Pt results in good electrocatalytic activity towards H2O2 oxidation with better tolerance towards aqueous environment mimicking physiological conditions compared to pure Pt. In biofouling experiments, however, both the hybrid material and Pt were almost completely, blocked after immersion in protein-containing solutions and did not produce any peaks for ferrocenemethanol oxidation or reduction. On the contrary, it was still possible to obtain clearpeaks for H2O2 oxidation with them after similar treatment Moreover, quartz crystal microbalance experiment showed less protein adsorption on the hybrid sample compared to Pt which is also supported by the electrochemical biofouling experiments for H2O2 detection. (C) 2015 Elsevier B.V. All rights reserved.

Water interactions of ultra-thin films of wood-derived polysaccharides were investigated by using surface sensitive methods, Quartz Crystal Microbalance with Dissipation (QCM-D) and Atomic Force Microscopy (AFM). These approaches allow systematic molecular level detection and reveal information on the inherent behaviour of biobased materials with nanosensitivity. The influence of structural features of cellulose films i.e. crystallinity, surface roughness and porosity on water interactions was clarified. Cellulose films were prepared using spin-coating and Langmuir-Schaefer deposition to obtain thin films of equal thickness, identical cellulose origin, simultaneously with different supramolecular structures. The uptake/release of water molecules and swelling were characterized using QCM-D, and the structural features of the films were evaluated by AFM. More crystalline cellulose film possessed nanoporosity and as a consequence higher accessible surface area (more binding sites for water) and thus, it was capable of binding more water molecules in humid air and when immersed in water when compared to amorphous cellulose film. Due to the ordered structure, more crystalline cellulose film remained rigid and elastic although the water binding ability was more pronounced compared to amorphous film. The lower amount of bound water induced softening of the amorphous cellulose film and the elastic layer became viscoelastic at high humidity. Finally, cellulose thin films were modified by adsorbing a layer of 1-butyloxy-2-hydroxypropyl xylan, and the effect on moisture uptake was investigated. It was found that the supramolecular structure of the cellulose substrate has an effect not only on the adsorbed amount of xylan derivative but also on the water interactions of the material.

A method of preparing model cellulose surfaces by the Langmuir–Blodgett (LB) technique with horizontal dipping procedure has been developed. The primary aim for the use of these surfaces was adsorption studies performed with the quartz crystal microbalance with dissipation (QCM-D) instrument. Hydrophobised cellulose (trimethylsilyl cellulose, TMSC) was deposited on the hydrophobic, polystyrene-coated QCM-D crystal. After 15 dipping cycles, the TMSC film fully covers the crystal surface. TMSC can easily be hydrolysed back to cellulose with acid hydrolysis. With this method a smooth, rigid, thin and reproducible cellulose film was obtained. Its morphology, coverage, chemical composition and wetting was further characterised using atomic force microscopy (AFM), X-Ray photoelectron spectroscopy (XPS), and contact angle measurements. The swelling behaviour and the stability of the cellulose film in aqueous solutions at different ionic strengths were studied using the QCM-D instrument. The swelling/deswelling properties of the cellulose film were those expected of polyelectrolytes with low charge density; some swelling occurred in pure water and the swelling decreased when the ionic strength was increased. No significant layer softening was detected during the swelling. The effect of electrolyte concentration and polymer charge density on the adsorption of cationic polyelectrolytes on the cellulose surface was also investigated. At low electrolyte concentration less of the highly charged PDADMAC was adsorbed as compared to low charged C-PAM. The adsorbed amount of PDADMAC increased with increasing ionic strength and a more compact layer was formed while the effect of electrolyte concentration on the adsorption of C-PAM was not as pronounced.