Halloysite is weakly toxic to cells and can be excreted out through the gastrointestinal metabolism of zebrafish.

Chitin nanocrystals modified by dopamine (D-ChNCs)/graphene oxide (GO) composite membranes were successfully prepared with the assistance of vacuum filtration. D-ChNCs/GO was analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to characterize the surface morphology of the membrane. The hydrophilicity of membrane is dependent on the content of the hydrophilic D-ChNCs, which shows a sharp increase of pure water flux from 8.8 of pure GO to 135.6 L·m–2·h–1. The rejection ratio of methylene blue (MB) and Congo red (CR) is as high as 99.3 and 98.3%, respectively. In addition, the oil rejection ratio of the membrane is above 97.5%, exhibiting good oleophobicity. The recycle experiment also demonstrates acceptable recyclability and proper regeneration for practical application. In total, D-ChNCs/GO composite membranes with excellent hydrophilicity, good oleophobicity, and anti-dye and anti-oil fouling have great potential in wastewater treatment.

Superamphiphobic coating has significant applications in self-cleaning and antifouling materials. Herein, chitin nanocrystals (ChNCs) with a needlelike morphology as building blocks were modified by thiol groups and highly fluorinated long chains to reduce the surface free energy. For the prepared superamphiphobic ChNC particles, a series of morphological and physicochemical characterizations, such as transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and X-ray photoelectron spectroscopy, were performed. The superamphiphobic ChNC particles feature high contact angles and low sliding angles for various liquids, including n-decane with a low surface tension (23.3 mN/m). Different liquid droplets can retain a perfectly quasispherical shape on the coating surface. Most interestingly, liquid marbles wrapped up by this superamphiphobic powder can “stand” on various substrates without any collapse. The coating shows a good repellency for liquids after the mechanical damage tests and thermal treatments. In addition, the superamphiphobic ChNC particles could be applied onto various substrates, exhibiting a good resistance and substrate-independent performance. In sum, the fluorinated ChNC coatings with superior superamphiphobicity, substrate independence, and stable mechanical and thermal properties show promising applications of water/oil-proof, self-cleaning, and antifouling coatings.

In this study, the toxicity of two one-dimensional (1D) nanoparticles, halloysite nanotubes (HNTs) and chitin whiskers (ChNCs), was investigated in detail. Both in vitro and in vivo models were applied to evaluate the toxicity by cell viability staining, apoptosis assay, and reactive oxygen species generation. Particularly, the toxicity of HNTs and ChNCs was compared using an in vivo model Caenorhabditis elegans; their toxicity was assessed using the in vitro models, mouse bone marrow mesenchymal stem cells (mBMSCs) and rat osteosarcoma cells (UMR-106). In vitro, both HNTs and ChNCs exhibited low toxicity at concentrations lower than 50 μg/mL, but HNTs showed higher toxicity than ChNCs at higher concentrations such as 200 μg/mL. Cell viabilities of mBMSCs and UMR-106 were 73.4 and 77.1% at the HNT concentration of 200 μg/mL, while these were 96.2 and 99.8% at the ChNC concentration of 200 μg/mL, respectively. In vivo, HNTs exhibited a side effect on the C. elegans reproduction but did not influence the lifespan and other phenotypes, which suggested that HNTs had no long-term toxicity effects. While ChNCs did not result in obvious alterations in the phenotype of worms below the concentration of 2.5 mg/mL, the brood size of C. elegans decreased at ChNC concentrations of 10 and 50 mg/mL. Moreover, ChNCs had the side effect on the development of C. elegans at the high level. However, ChNC exposure at the concentrations of 10 and 50 mg/mL induced the longer fast movement periods and extended lifespan of C. elegans. It demonstrated that both HNTs and ChNCs had good biocompatibility below the concentration of 2.5 mg/mL. The toxicity studies of these two 1D nanoparticles contributed to their great significance for various biomedical applications.

Chitin nanocrystals (ChNCs), prepared by acid hydrolysis of chitin, exhibit a uniform needlelike morphology and high dispersion stability in aqueous solutions, which makes them good candidates for drug delivery. Porous ChNC scaffolds were freeze-dried from different concentrations of ChNC dispersions and then cross-linked by a reaction with glutaraldehyde. Various techniques, including scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and testing of mechanical properties, porosity, and swelling properties, were used to characterize the structure of chemically cross-linked chitin nanocrystal (XChNC) scaffolds. The compressive mechanical strength, density, porosity, and water absorption rate of XChNC scaffolds were dependent on the concentration of ChNCs. XChNC scaffolds showed interconnected pores with a mean pore size of ∼65 μm diameter. Curcumin was used as a model drug and loaded into the XChNC scaffold by encapsulation in Tween 20 micelles. The drug release period from XChNC scaffolds was determined to be 540 min in phosphate-buffered saline (PBS) at pH 5.3 and 780 min in PBS at pH 7.4. Cytotoxicity experiments using human breast adenocarcinoma cells (MCF-7) revealed that released curcumin inhibited the proliferation of MCF-7 cells. All of the results show that XChNC scaffolds exhibit great potential for tissue-engineering and drug-delivery applications.