Combining Rigid Cellulose Nanocrystals and Soft Silk Proteins: Revealing Interactions and Alignment in Shear

Abstract

Natural materials, such as silk and cellulose, have an inspiring set of properties, which have evolved over hundreds of millions of years. In this study, cellulose nanocrystals (CNCs) and regenerated silk fibroin (RSF) are combined to evaluate their suitability for filament formation. This is assessed by tuning and characterizing the interactions between these two materials and finally by studying the alignment of the mixtures under shear. To modify the interactions between CNCs and silk, CNCs with varying surface functionalities (sulfate and/or aminosilane groups) are used. The interactions and compatibility of the two components are investigated using quartz crystal microbalance with dissipation monitoring (QCM-D) and photothermal atomic force microscopy (AFM-IR), which show that ionic interactions induce sufficient binding between the two components. Then, the alignment of the CNC and silk mixtures is evaluated by shear-induced polarized light imaging, which indicates that silk can orientate with the CNCs when not covalently bound. Finally, the potential of the materials for filament formation is tentatively demonstrated using an industrial dry-spinning environment, where CNCs are expected to bring order and alignment, whereas RSF provides soft and more mobile regions to further facilitate the alignment of the final filament structure.

Lignocellulosic–biomolecules conjugated systems: green-engineered complexes modified by covalent linkers

“…For instance, Leppänen et al observed an increase in the binding between CNC and silk fibroin by amine–amine linked between succinimidyl-6-hydrazinonicotinate acetone hydrazone (SANH) and succinimidyl-4-formyl benzoate (SFB) moieties, but it induced a not-wanted nanocluster formation. 109 Other molecules, such as the combination of tetraethylene pentamine (TEPA) and GMA, form longer linkers capable of connecting cellulose to the rhodamine chromophore (RC). In this configuration, cellulose suffers modification through the cyclohexane ring in the presence of cerium ammonium nitrate, and aldehyde functional molecules such as RC attaches to cellulose – GMA – TEPA by imine reaction in DMF medium.…”

“…For instance, MCC and rhodamine chromophore exhibit excellent optical signals and selectivity (detection limit on Hg 2+ < 9.18 × 10 −7 M) upon contact with mercury, playing a notable role in detecting and removing the metal in tap water. 109 Alternatively, CNC coupled with the pH-indicator dye (5 and 6)-carboxy-2′,7′-dichloro-fluorescein, and l -leucine amino acid were used to construct fluorescent nanoparticles for pH-sensing, demonstrating fluorescent properties when the pH of the media was increased (Fig. 6(b)).…”

AFM-IR investigation of thin PECVD SiOx films on a polypropylene substrate in the surface-sensitive mode

“…One of the first AFM-IR demonstrations was reported in 2005 by Dazzi et al [4], who presented AFM-IR spectra of single bacterial cells. Further on, this technique became more refined and found its way into many and highly diverse fields of application, including virology, DNA nanotechnology, polymer science, and materials science [5][6][7][8][9]. The importance of AFM-IR steadily grew over the past decade and its development has been described in detail in several review papers [1,3,9,10].…”