Low solid content mouldable chitin physical hydrogel prepared by atypical rupture-free swelling.

In this study, the atypical swelling gelation of chitin physical hydrogels was investigated. Just by tuning the amount of the N-acetylation reagent, the degree of acetylation varied and mouldable chitin hydrogels with a wide variety of gel concentrations (0.2-6.4 wt%) were obtained. In response to the gel concentration, the mechanical properties ranged from swollen soft gels to shrunken rigid gels (compressive moduli of 4-310 kPa). The thus-prepared chitin hydrogels, which were composed of only chitin and water, exhibited high transparency and integrity. The swelling gelation of chitin physical hydrogels was achieved owing to both the positive charges of the amino groups inducing the osmotic pressure and the toughness of the crystalline nanofibrous network structure of the chitin hydrogels that endured the large volume change. These previously unnoticed advantageous aspects of chitin have pioneered a novel area of swellable physical gels that has been exclusive to chemical gels so far.

Identification of Chitin Allomorphs in Poorly Crystalline Samples Based on the Complexation with Ethylenediamine.

Chitin is a key component of hard parts in many organisms, but the biosynthesis of the two distinctive chitin allomorphs, α- and ß-chitin, is not well understood. The accurate determination of chitin allomorphs in natural biomaterials is vital. Many chitin-secreting living organisms, however, produce poorly crystalline chitin. This leads to spectrums with only broad lines and imprecise peak positions under conventional analytical methods such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy, and solid-state nuclear magnetic resonance spectroscopy, resulting in inconclusive identification of chitin allomorphs. Here, we developed a novel method for discerning chitin allomorphs based on their different complexation capacity and guest selectivity, using ethylenediamine (EDA) as a complexing agent. From the peak shift observed in XRD profiles of the chitin/EDA complex, the chitin allomorphs can be clearly discerned. By testing this method on a series of samples with different chitin allomorphs and crystallinity, we show that the sensitivity is sufficiently high to detect the chitin allomorphs even in near-amorphous, very poorly crystalline samples. This is a powerful tool for determining the chitin allomorphs in phylogenetically important chitin-producing organisms and will pave the way for clarifying the evolution and mechanism of chitin biosynthesis.

Magnetically Collectable Nanocellulose-Coated Polymer Microparticles by Emulsion Templating.

Magnetic nano/microparticles offer potential benefits for environmental applications such as water purification. However, achieving functional and stable surfaces remains a critical challenge for magnetic particle design. Nanocellulose, a naturally occurring nanofiber, is a promising surface material candidate, owing to its ease of functionalization and chemical stability. Here, we developed a magnetically collectable nanocellulose-coated polymer microparticle synthesis method, based on Pickering emulsion templating. The average diameter of the core/shell microparticles was 2.7 µm, and they were well dispersed in water, owing to the coverage with surface-carboxylated nanocelluloses. Most magnetic Fe3O4 nanoparticles with a 30 nm diameter were encapsulated in the microparticles and enriched at the CNF/polymer interfaces. The nanocellulose shell showed high loading of cationic dye molecules. In addition, the nanocellulose-coated microparticles could be recovered even after the dye loading by exposing the aqueous dispersion to a magnetic field.

Synthesis of Chitin Nanofiber-Coated Polymer Microparticles via Pickering Emulsion.

Chitin nanofiber (ChNF) has received significant research attention owing to its potential for use in a variety of applications, such as medicine and cosmetics. Here, we synthesize a novel ChNF material, ChNF-coated polymer microparticles, using a Pickering emulsion-templated approach. Two varieties of ChNF with different crystal structures, lengths, and surface charges were used to form the microparticle shells. When ChNFs with a shorter length and greater surface charge were used, the microparticles showed good dispersibility in water and narrow size distribution with number- and volume-median diameters of 1.46 and 1.84 µm, respectively. The microparticles were easily collected by filtration and redispersed in water, even after drying. The surface ChNF shells assembled at the microparticle surfaces showed potential as an adsorption site, effectively capturing anionic dye molecules. This technique offers new opportunities for the development of green nanocomposite materials using a facile aqueous process.

Chitin nanofiber-coated biodegradable polymer microparticles via one-pot aqueous process.

Tailoring the surface of biodegradable microparticles is important for various applications in the fields of cosmetics, biotechnology, and drug delivery. Chitin nanofibers (ChNFs) are one of the promising materials for surface tailoring owing to its functionality, such as biocompatibility and antibiotic properties. Here, we show biodegradable polymer microparticles densely coated with ChNFs. Cellulose acetate (CA) was used as the core material in this study, and ChNF coating was successfully carried out via a one-pot aqueous process. The average particle size of the ChNF-coated CA microparticles was approximately 6 µm, and the coating procedure had little effect on the size or shape of the original CA microparticles. The ChNF-coated CA microparticles comprised 0.2-0.4 wt% of the thin surface ChNF layers. Owing to the surface cationic ChNFs, the ζ-potential value of the ChNF-coated microparticles was +27.4 mV. The surface ChNF layer efficiently adsorbed anionic dye molecules, and repeatable adsorption/desorption behavior was exhibited owing to the coating stability of the surface ChNFs. The ChNF coating in this study was a facile aqueous process and was applicable to CA-based materials of various sizes and shapes. This versatility will open new possibilities for future biodegradable polymer materials that satisfy the increasing demand for sustainable development.