The preparation of stable spherical alkali lignin nanoparticles with great thermal stability and no cytotoxicity.

In order to further develop the potential applications of lignin biomass, the research on lignin nanoparticles (LNPs) and their nanocomposites has attracted increasing attention. In this study, a facile and no chemical modification approach to prepare stable alkali lignin nanospheres is presented. The nanospheres around 85-125 nm were prepared through the π-π interactions between molecules in the self-assembly process. Lignin alkali was dissolved in ethylene glycol at different initial concentrations and subsequently ultrasound and dialysis treatment were conducted to prepare LNPs. The prepared LNPs had zeta potentials between -20 mV and -40 mV, and they were electrostatically stable over the pH range of 3 to 12 in aqueous solution. The chemical structure of LNPs was not significantly modified compared to lignin. Meanwhile the increased content of carboxyl and aliphatic hydroxyl groups in the LNPs structure was observed. Furthermore, the thermal stability and solubility in organic solvents (ethanol, acetone and THF) of LNPs were enhanced compared to those of lignin. In vitro cell viability evaluation indicated that the prepared LNPs had no cytotoxicity and excellent biocompatibility with mouse fibroblast. Therefore, we proposed here the production of high-quality and renewable LNPs, which will provide a novel perspective for multifunctional applications of bio-based nanomaterials.

Gold, Silver, and Iron Oxide Nanoparticle Incorporation into Silk Hydrogels for Biomedical Applications: Elaboration, Structure, and Properties.

Silk fibroin (SF) is a versatile material with biodegradable and biocompatible properties, which make it fit for broad biomedical applications. In this context, the incorporation of nanosized objects into SF allows the development of a variety of bionanocomposites with tailored properties and functions. Herein, we report a thorough investigation on the design, characterization, and biological evaluation of SF hydrogels incorporating gold, silver, or iron oxide nanoparticles. The latter are synthesized in aqueous media using a biocompatible ligand allowing their utilization in various biomedical applications. This ligand seems to play a pivotal role in nanoparticle dispersion within the hydrogel. Results show that the incorporation of nanoparticles does not greatly influence the mechanism of SF gelation and has a minor impact on the mechanical properties of the so-obtained bionanocomposites. By contrast, significant changes are observed in the swelling behavior of these materials, depending on the nanoparticle used. Interestingly, the main characteristics of these bionanocomposites, related to their potential use for biomedical purposes, show the successful input of nanoparticles, including antibacterial properties for gold and silver nanoparticles and magnetic properties for iron oxide ones.

Silk Polymers and Nanoparticles: A Powerful Combination for the Design of Versatile Biomaterials.

Silk fibroin (SF) is a natural protein largely used in the textile industry but also in biomedicine, catalysis, and other materials applications. SF is biocompatible, biodegradable, and possesses high tensile strength. Moreover, it is a versatile compound that can be formed into different materials at the macro, micro- and nano-scales, such as nanofibers, nanoparticles, hydrogels, microspheres, and other formats. Silk can be further integrated into emerging and promising additive manufacturing techniques like bioprinting, stereolithography or digital light processing 3D printing. As such, the development of methodologies for the functionalization of silk materials provide added value. Inorganic nanoparticles (INPs) have interesting and unexpected properties differing from bulk materials. These properties include better catalysis efficiency (better surface/volume ratio and consequently decreased quantify of catalyst), antibacterial activity, fluorescence properties, and UV-radiation protection or superparamagnetic behavior depending on the metal used. Given the promising results and performance of INPs, their use in many different procedures has been growing. Therefore, combining the useful properties of silk fibroin materials with those from INPs is increasingly relevant in many applications. Two main methodologies have been used in the literature to form silk-based bionanocomposites: in situ synthesis of INPs in silk materials, or the addition of preformed INPs to silk materials. This work presents an overview of current silk nanocomposites developed by these two main methodologies. An evaluation of overall INP characteristics and their distribution within the material is presented for each approach. Finally, an outlook is provided about the potential applications of these resultant nanocomposite materials.