Highly charged (zeta potential ζ = +105 mV, acetate counterions) chitin nanoparticles (NCh) of three different average aspect ratios (∼5, 25, and >60) were obtained by low-energy deconstruction of partially deacetylated chitin. The nanoparticles were effective in reducing the interfacial tension and stabilized the oil/water interface via network formation (interfacial dilatational rheology data) becoming effective in stabilizing Pickering systems, depending on NCh size, composition, and formulation variables. The improved interfacial wettability and electrosteric repulsion facilitated control over the nanoparticle’s surface coverage on the oil droplets, their aspect ratio and stability against coalescence during long-term storage. Emulsion superstabilization (oil fractions below 0.5) occurred by the microstructuring and thickening effect of NCh that formed networks at concentrations as low as 0.0005 wt %. The ultrasound energy used during emulsion preparation simultaneously reduced the longer nanoparticles, producing very stable, fine oil droplets (diameter ∼1 μm). Our findings indicate that NCh surpasses any reported biobased nanoparticle, including nanocelluloses, for its ability to stabilize interfaces at ultralow concentrations and represent a step-forward in efforts to fully replace surfactants in multiphase systems.

The surface chemistry and adsorption behavior of submicrometer cellulosic and lignin particles have drawn wide-ranging interest in the scientific community. Here, we introduce their assembly at fluid/fluid interfaces in Pickering systems and discuss their role in reducing the oil/water interfacial tension, limiting flocculation and coalescence, and endowing given functional properties. We discuss the stabilization of multiphase systems by cellulosic and lignin colloids and the opportunities for their adoption. They can be used alone, as dual components, or in combination with amphiphilic molecules for the design of multiphase systems relevant to household products, paints, coatings, pharmaceutical, foodstuff, and cosmetic formulations. This invited feature article summarizes some of our work and that of colleagues to introduce the readers to this fascinating and topical area.

PDF/A is an ISO-standardized version of the Portable Document Format (PDF) specialized for the digital preservation of electronic documents. The extension in the file name is pdf. PDF/A differs from "normal" PDF in that features ill-suited for long-term archiving are omitted. PDF/A embeds all fonts used in the document within the PDF file, so that the user of your file will not have to have the same fonts that you used to create the file installed on their computer in order to read it. Recommended versions are PDF/A-1a, -1b, -2a or -2b.PDF/A conversion -how to convert files to the PDF/A -format using different tools Microsoft Word (Office) and PDF-Xchange pro/Editor are installed on all Windows workstations managed by Aalto IT.

Lignin has interesting functionalities to be exploited in adhesives for medicine, foods and textiles. Nanoparticles (NPs) < 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, β-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 β-casein NPs, the values were 20 and 8, respectively, and for the β-casein coated CLPs between these two cases. When NPs were dispersed in adhesive formulation, the increased Young’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.

In vitro cell culture or tissue models that mimic in vivo cellular response have potential in tissue engineering and regenerative medicine, and are a more economical and accurate option for drug toxicity tests than animal experimentation. The design of in vivo -like cell culture models should take into account how the cells interact with the surrounding materials and how these interactions affect the cell behavior. Cell-material interactions are furthermore important in cancer metastasis and tumor progression, so deeper understanding of them can support the development of new cancer treatments. Herein, the colloidal probe microscopy technique was used to quantify the interactions of two cell lines (human pluripotent stem cell line WA07 and human hepatocellular carcinoma cell line HepG2) with natural, xeno-free biomaterials of different chemistry, morphology, and origin. Key components of extracellular matrices –human collagens I and IV, and human recombinant laminin-521−, as well as wood-derived, cellulose nanofibrils –with evidenced potential for 3D cell culture and tissue engineering– were analysed. Both strength of adhesion and force curve profiles depended on biomaterial nature and cell characteristics. The successful growth of the cells on a particular biomaterial required cell-biomaterial adhesion energies above 0.23 nJ/m. The information obtained in this work supports the development of new materials or hybrid scaffolds with tuned cell adhesion properties for tissue engineering, and provides a better understanding of the interactions of normal and cancerous cells with biomaterials in the human body.