Preparation of chitin nanofibers by surface esterification of chitin with maleic anhydride and mechanical treatment

Esterification with maleic anhydride significantly improved the mechanical disintegration of chitin into uniform 10-nm nanofibers. Nanofibers with 0.25° of esterification were homogeneously dispersed in basic water due to the carboxylate salt on the surface. Esterification proceeded on the surface and did not affect the relative crystallinity. A cast film of the esterified chitin nanofibers was highly transparent, since the film was free from light scattering

Protein/CaCO3/Chitin Nanofiber Complex Prepared from Crab Shells by Simple Mechanical Treatment and Its Effect on Plant Growth

A protein/CaCO3/chitin nanofiber complex was prepared from crab shells by a simple mechanical treatment with a high-pressure water-jet (HPWJ) system. The preparation process did not involve chemical treatments, such as removal of protein and calcium carbonate with sodium hydroxide and hydrochloric acid, respectively. Thus, it was economically and environmentally friendly. The nanofibers obtained had uniform width and dispersed homogeneously in water. Nanofibers were characterized in morphology, transparency, and viscosity. Results indicated that the shell was mostly disintegrated into nanofibers at above five cycles of the HPWJ system. The chemical structure of the nanofiber was maintained even after extensive mechanical treatments. Subsequently, the nanofiber complex was found to improve the growth of tomatoes in a hydroponics system, suggesting the mechanical treatments efficiently released minerals into the system. The homogeneous dispersion of the nanofiber complex enabled easier application as a fertilizer compared to the crab shell flakes

Bio-based wrinkled surfaces harnessed from biological design principles of wood and peroxidase activity

A new and simple approach for surface wrinkling inspired by polymer assemblies in wood fibers is introduced. A hard skin is synthesized on a linear polysaccharide support that resembles the structural units of the cell wall. This skin, a wood mimetic layer, is produced through immersion in a solution containing phenolic precursor and subsequent surface reaction by horseradish peroxidase. A patterned surface with micron‐scale wrinkles is formed upon drying and as a result of inhomogeneous shrinkage. We demonstrate that the design of the wrinkled surfaces can be controlled by the molecular structure of the phenolic precursor, temperature, and drying stress. It is noteworthy that this is a totally bio‐based system involving green materials and processes

Wood-mimetic skins prepared using horseradish peroxidase catalysis to induce surface wrinkling of chitosan film upon drying

We previously developed bio-based wrinkled surfaces induced by wood-mimetic skins upon drying in which microscopic wrinkles were fabricated on a chitosan (CS) film by immersing it in a phenolic acid solution, followed by horseradish peroxidase (HRP)-catalyzed surface reaction and drying. However, the detailed structure of the resulting wood-mimetic skins, including crosslinking mode and thickness, has not been clarified due to the difficulty of the analysis. Here, we prepare wrinkled films using ferulic acid (FE), vanillic acid (VA), and homovanillic acid (HO) and characterize their structures to clarify the unknown characteristics of wood-mimetic skin. Chemical and structural analyses of wood-mimetic skins prepared using VA and HO indicate that the crosslinking structure in the skin is composed of ionic bonds between CS and an oligophenolic residue generated by the HRP-catalyzed reaction on the CS surface. Moreover, the quantity of these ionic bonds is related to the skin hardness and wrinkle size. Finally, SEM and TOF-SIMS analyses indicate that the skin thickness is on the submicron order (<200 nm)

Novel 1,8-Naphthalimide derivative with an open space for an anion: Unique fluorescence behaviour depending on the binding anion’s electrophilic property

We have designed a novel 1,8-naphthalimide derivative with an open space for an anion. Computational calculation has predicted that the space could trap various anion species and photo-induced charge transfer depending on the anion's electrophilic properties. Indeed, the fluorescence behaviour of the 1,8-naphthalimide derivative complexes with each anion is consistent with the computational prediction

Mineralization of hydroxyapatite upon a unique xanthan gum hydrogel by an alternate soaking process

We previously reported a xanthan gum (Xan) hydrogel showing excellent mechanical properties. Mineralization of hydroxyapatite (Hap) upon the Xan hydrogel would provide a unique biomaterial applicable for bone tissue engineering. Here, we show the mineralization of Hap upon the Xan hydrogel by means of an alternate soaking process. Hap was gradually grown upon the Xan-matrix surface with increasing number of soaking cycles due to the ionic interactions between calcium cations and carboxyl groups. Interestingly, the mineralization induced a microstructure change in the gel-matrix from a layered structure to a porous structure. The mechanical properties of the resulting Hap–Xan composite hydrogels were further investigated by a tensile test, where the Hap–Xan composite hydrogel with an appropriate amount of Hap (Xan/Hap = 2.7) was capable of approximately 370% elongation

Application of Bio-Based Wrinkled Surfaces as Cell Culture Scaffolds

Microscopic surface architectures that can be easily manufactured have been in demand as mechano-structural cues for tissue engineering. Microscopic surface reliefs synthesized by wrinkling were expected as cell culture scaffolds for cell proliferation, control of cellular alignment and differentiation, and spheroid generation. We previously developed bio-based wrinkled films prepared via lignification-mimetic reactions and drying. Although these films are expected as a candidate for cell culture scaffolds, stability and morphology of the wrinkled surfaces in aqueous buffer solutions were not explored. Here, we investigate the surface morphologies of the wrinkled films in phosphate-buffered saline, and their application to 3T3 cell culture. The wrinkled film prepared with the immersion treatment at 40 °C maintained its wrinkled structure in phosphate-buffered saline even after five days, although the wrinkles were broadened by hydration of the skin layer. Interestingly, higher cell numbers were observed in the 3T3 cell culture using the wrinkled film than using flat film with the same surface composition. In addition, the high biocompatibility of the wrinkled film was confirmed by in vivo experiments. These results strongly encourage application of the wrinkled film as a mechano-structural cue. Studies of the advanced applications for the wrinkled films are now in progress