ABSTRACT
Many reinforcing materials have been investigated to improve the mechanical performance of the host matrices. Among reinforcing materials, α-chitin nanocrystals (α-ChNCs) from shrimp or crab shells were recently used as reinforcing nanofillers of polymer nanocomposites. In this study, novel ß-chitin nanocrystals (ß-ChNCs) were employed for the reinforcing nanomaterial of methylcellulose (MC) hydrogels. They were obtained from cuttlefish bone by acid hydrolysis. The ß-ChNCs had a different morphology with an irregularly granular shape, unlike the rod-like shape of α-ChNCs, and were stable in their aqueous suspensions. Subsequently, the MC nanocomposite hydrogels were prepared by mechanically mixing the water-soluble MC in aqueous ß-ChNCs suspension. The formation rate and mechanical strength of MC nanocomposite hydrogels were dramatically increased even at a low content of ß-ChNCs. This increment in the gelation rate and gel strength might be associated with the formation of additional physical crosslinking between crystalline ß-ChNCs and MC molecular chains, as well as the original hydrophobic interaction between the MC molecules. Therefore, dual physical crosslinking was constructed in the MC nanocomposite hydrogels. These robust MC composite hydrogels offer great potential for various biomedical applications.
ABSTRACT
Novel ß-chitin nanocrystals (ß-CNCs) were extracted from cuttlefish bone via deproteinization and demineralization, followed by acid hydrolysis. As a new source of ß-chitin, ß-CNCs obtained from cuttlefish bone were bumpy and relatively spherical in shape, whereas α-CNCs extracted from shrimp shell had a rod-like-shape. Also, the average width and length of ß-CNCs were 14 and 22 nm, respectively, whereas the average dimensions of α-CNCs were 26 nm (diameter) × 320 nm (length). The differences in shape and dimensions between ß-CNCs and α-CNCs might originate from the different chitin microfibrillar structures within the hierarchical multilayers with calcium carbonate, called a Bouligand structure, in shrimp shell or cuttlefish bone. From the NMR spectra, the DD values of purified α-CNCs and ß-CNCs were found to be 17% and 13%, respectively. From the XRD patterns, the complete transformation of ß-CNCs to α-CNCs was observed during the acid hydrolysis. By contrast, ß-CNCs had higher surface areas due to their smaller sizes and better dispersity in water suspension without aggregation. Furthermore, the deacetylation of ß-CNCs was induced by a concentrated NaOH solution. The structural and thermal properties of the ß-CNCs and deacetylated ß-CNCs were characterized through proton nuclear magnetic resonance (1H NMR), transmittance electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC).
ABSTRACT
A nanofibrous ß-chitin web was fabricated via electrospinning for use as a novel wound dressing material. ß-chitin was extracted from cuttlefish bone using deproteinization and demineralization. First, cuttlefish bone was alkali-treated to remove the proteins and was then treated with the acid for demineralization. The extracted ß-chitin was dissolved in formic acid as solvent to evaluate its electrospinnability, and the electrospinnability increased remarkably when ß-chitin was blended with poly(ethylene oxide) (PEO) than without. The blended ß-chitin/PEO nanofibers had a fiber diameter of about 400â¯nm, and the diameter decreased after soaking in water to remove the PEO. The structural and physical properties of the ß-chitin material and its nanofibers were characterized using Attenuated total reflectance infrared spectroscopy (ATR-IR), Proton nuclear magnetic resonance (1H NMR), Scanning electron microscopy/Energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), texturometry, viscometry and contact angle measurements, and an animal test was conducted to investigate the wound healing effect. The ß-chitin nanofibers were found to have great potential as nanomaterials for wound healing.
