Dendritic Polyampholyte-Assisted Formation of Functional Cellulose Nanofibril Materials.

A new platform of functional hybrid materials from anionically charged high-aspect-ratio cellulose nanofibrils (CNFs) and a dendritic polyampholyte, Helux, is herein proposed. The polyampholytic character of Helux enabled facile and efficient nanoscale mixing with the CNFs, and the resulting composite mixtures of CNFs and Helux displayed thixotropic behavior and formed physical and reversibly cross-linked gels when left unperturbed for short spans of time. The gel could be chemically cross-linked into self-supporting solid hydrogels containing impressive water contents of 99.6% and a storage modulus of 1.8 kPa by thermal activation. Non-cross-linked mixtures of CNF/Helux were assembled into composites, such as films by solvent casting and aerogels with densities as low as 4 kg/m3 by lyophilizing ice-templated CNF/Helux mixtures. The resulting materials exhibited excellent wet stability due to the heat-activated cross-linking and were readily available for postfunctionalization via amidation chemistry using Helux-accessible amines in aqueous conditions. The mechanical performance of the films was not jeopardized by the addition of Helux. Additionally, by varying the amount of Helux, the compressive elastic modulus of aerogels was tunable in both the non-cross-linked and cross-linked states. The fast and efficient nanoscale mixing of anionic CNFs and a polymer containing cationic groups is unique, novel, and promising as a functional material platform. Sustainable CNFs guided by heterofunctional dendritic polyampholytes are envisaged to act as a pillar toward high-performance applications, including biomedicine and biomaterials.

Antibiotic-Free Cationic Dendritic Hydrogels as Surgical-Site-Infection-Inhibiting Coatings.

A non-toxic hydrolytically fast-degradable antibacterial hydrogel is herein presented to preemptively treat surgical site infections during the first crucial 24 h period without relying on conventional antibiotics. The approach capitalizes on a two-component system that form antibacterial hydrogels within 1 min and consist of i) an amine functional linear-dendritic hybrid based on linear poly(ethylene glycol) and dendritic 2,2-bis(hydroxymethyl)propionic acid, and ii) a di-N-hydroxysuccinimide functional poly(ethylene glycol) cross-linker. Broad spectrum antibacterial effect is achieved by multivalent representation of catatonically charged ß-alanine on the dendritic periphery of the linear dendritic component. The hydrogels can be applied readily in an in vivo setting using a two-component syringe delivery system and the mechanical properties can accurately be tuned in the range equivalent to fat tissue and cartilage (G' = 0.5-8 kPa). The antibacterial effect is demonstrated both in vitro toward a range of relevant bacterial strains and in an in vivo mouse model of surgical site infection.

Flow-assisted assembly of nanostructured protein microfibers.

Some of the most remarkable materials in nature are made from proteins. The properties of these materials are closely connected to the hierarchical assembly of the protein building blocks. In this perspective, amyloid-like protein nanofibrils (PNFs) have emerged as a promising foundation for the synthesis of novel bio-based materials for a variety of applications. Whereas recent advances have revealed the molecular structure of PNFs, the mechanisms associated with fibril-fibril interactions and their assembly into macroscale structures remain largely unexplored. Here, we show that whey PNFs can be assembled into microfibers using a flow-focusing approach and without the addition of plasticizers or cross-linkers. Microfocus small-angle X-ray scattering allows us to monitor the fibril orientation in the microchannel and compare the assembly processes of PNFs of distinct morphologies. We find that the strongest fiber is obtained with a sufficient balance between ordered nanostructure and fibril entanglement. The results provide insights in the behavior of protein nanostructures under laminar flow conditions and their assembly mechanism into hierarchical macroscopic structures.