Mussel-inspired chitin nanofiber adherable hydrogel sensor with interpenetrating network and great fatigue resistance for motion and acoustics monitoring.

A method for grafting dopamine onto TEMPO-oxidized chitin nanofibers (TOChN) was developed, achieving a surface grafting rate of 54 % through the EDC/NHS reaction. This process resulted in the formation of dopamine-grafted TOChN (TOChN-DA). Subsequently, an adherent, highly sensitive, fatigue-resistant conductive PAM/TOChN-PDA/Fe3+ (PTPF) hydrogel was successfully synthesized based on the composition of polyacrylamide (PAM) and TOChN-DA, which exhibited good cell compatibility, a tensile strength of 89.42 kPa, and a high adhesion strength of 62.56 kPa with 1.2 wt% TOChN-DA. Notably, the PTPF hydrogel showed stable adherence to various surfaces, such as rubber, copper, and human skin. Specifically, the addition of FeCl3 contributed to a multifunctional design in the PTPF interpenetrating network (IPN) hydrogel, endowing it with conductivity, cohesion, and antioxidant properties, which facilitated sensitive motion and acoustics monitoring. Moreover, the PTPF hydrogel demonstrated exceptional fatigue resistance and sensing stability, maintaining performance at 50 % strain over 1000 cycles. These attributes render the PTPF hydrogel a promising candidate for advanced biosensors in medical and athletic applications.

Ir-Doped CuPd Single-Crystalline Mesoporous Nanotetrahedrons for Ethylene Glycol Oxidation Electrocatalysis: Enhanced Selective Cleavage of C-C Bond.

The development of highly efficient electrocatalysts for complete oxidation of ethylene glycol (EG) in direct EG fuel cells is of decisive importance to hold higher energy efficiency. Despite some achievements, their progress, especially electrocatalytic selectivity to complete oxidated C1 products, is remarkably slower than expected. In this work, we developed a facile aqueous synthesis of Ir-doped CuPd single-crystalline mesoporous nanotetrahedrons (Ir-CuPd SMTs) as high-performance electrocatalyst for promoting oxidation cleavage of C-C bond in alkaline EG oxidation reaction (EGOR) electrocatalysis. The synthesis relied on precise reduction/co-nucleation and epitaxial growth of Ir, Cu and Pd precursors with cetyltrimethylammonium chloride as the mesopore-forming surfactant and extra Br- as the facet-selective agent under ambient conditions. The products featured concave nanotetrahedron morphology enclosed by well-defined (111) facets, single-crystalline and mesoporous structure radiated from the center, and uniform elemental composition without any phase separation. Ir-CuPd SMTs disclosed remarkably enhanced electrocatalytic activity and excellent stability as well as superior selectivity of C1 products for alkaline EGOR electrocatalysis. Detailed mechanism studies demonstrated that performance improvement came from structural and compositional synergies, which kinetically accelerated transports of electrons/reactants within active sites of penetrated mesopores and facilitated oxidation cleavage of high-energy-barrier C-C bond of EG for desired C1 products. More interestingly, Ir-CuPd SMTs performed well in coupled electrocatalysis of anode EGOR and cathode nitrate reduction, highlighting its high potential as bifunctional electrocatalyst in various applications.

Nanochitin and poly(N-isopropylacrylamide) interpenetrating network hydrogels for temperature sensor applications.

A strengthened interpenetrating network of 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO)-oxidized nanochitin (TOChN) with poly(N-isopropylacrylamide) (PNIPAm) chains was constructed in an acetic acid coagulation bath to fabricate hydrogels. The TOChN increased the water retention of the PNIPAm hydrogels while maintaining the lower critical solution temperature (LCST) at approximately 34 °C. The storage modulus and compression stress of the 0.62% TOChN@PNIPAm hydrogel were increased by about 32 and 13.47 times, respectively, compared among those as the pure PNIPAm hydrogel. These effects were accompanied by the transformation of the dominant network structure from PNIPAm molecular chain interactions to TOChN nanofibrillar cross-linking. In addition, TOChN@PNIPAm showed a shrinking-reswelling ability with a reserved shape. Fe3+ was further introduced to chelate with carboxyl groups on TOChN, which not only substantially increased the mechanical properties but additionally provided good conductivity for the hydrogels. Therefore, a temperature sensor was designed and showed a good thermal-resistance response, providing potential biosensor applications.

A MoS2QDs/chitin nanofiber composite for improved antibacterial and food packaging.

Chitin nanofiber has potential application as antibacterial nanocomposite material because of its inherent biocompatibility, biological activity, amino containing macromolecular structure and nano-size effect. Molybdenum disulfide quantum dots (MoS2QDs) were uniformly bonded on partially deacetylated chitin nanofibers (DEChNs) by hydrothermal reactions. The antibacterial properties of MoS2QDs/DEChN against Escherichia coli were detected under different conditions. When the antibacterial agent was fixed at 200 µg/mL, the survival rates of bacteria were 2.77% (pH = 4), 5.58% (pH = 5) and 7.83% (pH = 6), which were lower than those in the DEChN groups. Unlike DEChN, which only had excellent antibacterial activity under acidic conditions (pH < 5), the combination of DEChN and MoS2QDs had antibacterial activity close to neutral conditions, with a bacteriostatic rate > 90%. When TEMPO-oxidized cellulose nanofibers (TOCN) were applied for the preparation of MoS2QDs/TOCN, they did not show obvious antibacterial ability, which proved the positive role of DEChN and its amino groups. The MoS2QDs/DEChN assembled film could be applied to preserve meat by delaying spoilage. The current study might inspire new ideas for designing food packaging based on the prepared MoS2QDs/DEChN films.

One-Step Preparation of Chitin Nanofiber Dispersion in Full pH Surroundings Using Recyclable Solid Oxalic Acid and Evaluation of Redispersed Performance.

This study proposed an efficient and economical preparation pathway from purified chitin to nanofibers that can be dispersed in full pH surroundings. Recyclable oxalic acid was applied to prepare chitin nanofibers in a mild environment along with concurrent modifications of the carboxylic groups on the surface. Pretreatment with oxalic acid significantly improved the mechanical disintegration of chitin into nanofibers, the length of nanofibers reached ∼1100 nm, and the crystallinity and thermal stability of the chitin were basically unchanged with mild treatment. Oxalic acid can be reused many times with a high recovery of over 91%. Most importantly, the obtained nanofibers can be fabricated into films and hydrogels with certain mechanical properties, which can be redispersed into nanofibers using mild mechanical treatment. This method not only produces nanofibers in a green, reusable system but also provides a reference for the potential application of chitin nanofibers in commercial transportation and wide applicability.

TEMPO-oxidized nanochitin based hydrogels and inter-structure tunable cryogels prepared by sequential chemical and physical crosslinking.

Well dispersibility of 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO)-oxidized nanochitins under alkaline conditions supports the effective chemical crosslinking between nanochitin and epichlorohydrin. The storage modulus of nanochitin hydrogels can be promoted by approximately 10 times as the nanochitin-to-epichlorohydrin mass ratio changes from 4:1 (120 Pa) to 1:4 (1200 Pa). Besides the enhanced mechanical property of hydrogels, the inter-structure of resulting cryogels is found controllable. With increasing epichlorohydrin dosage, the inter-structure of cryogels transforms from a typical fiber-like to honeycomb-like texture. The balance between chemical crosslinking effect and electrostatic repulsion between nanochitins is believed to result this controllable inter-structure. Further immersing into acetic acid solution can greatly enhance the mechanical strength of nanochitin hydrogels due to the introduction of physical crosslinking domains by shielding the electrostatic repulsion, the storage modulus becomes two times higher after immersing in 50% (w/w) acetic acid solution, while the surface area of nanochitin cryogels decreases due to the denser structure.

An optimized preparation of nanofiber hydrogels derived from natural carbohydrate polymers and their drug release capacity under different pH surroundings.

Cellulose and chitin, as the two important natural carbohydrate polymers, have possibility to disassemble to biomass derived polysaccharide nanofibers. The 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) oxidized nanocellulose and nanochitin based hydrogel was fabricated via acid gas phase coagulation. It was observed that hydrogels began to form when the pH was lower than 3. When 0.1 mL of acetic acid coagulation bath was provided, 10 h were enough to form sufficient physical crosslinking. Moreover, the release time of amygdalin loaded in the hydrogel could be more than 60 h with a release amount of 80 % due to the uniform network and water-bearing structure. Meanwhile, the release capacity of hydrogels showed diversity at different pH surroundings, which was attributed to the existence of carboxyl groups on the oxidized nanofiber. The results suggested the possible application of the produced nanofiber hydrogels in some specific areas, such as drug delivery, wound dressing, and food packaging.

Case Report: A Novel PAX3 Mutation Associated With Waardenburg Syndrome Type 1.

Background: Waardenburg Syndrome Type 1 (WS1) is a rare hereditary disease, which is usually caused by the mutations of PAX3 (paired box 3). Here, we reported a pedigree with WS1, which was caused by a novel mutation in PAX3. Case Report: In this present report, a 10-year-old boy and his twin sister from a Han Chinese family presented with iris pigmentary abnormality, synophrys, and broad and high nasal root. Their father presented premature whitening of the hair, but no iris pigmentary abnormality. Their aunts presented the same clinical characteristics with the twins and premature graying of hair. However, none of the patients reported hearing loss. The clinical diagnosis of the four patients from this pedigree was WS1. The whole exome sequencing (WES) revealed a novel mutation (c.959-5T>G) in the PAX3 gene, which could be responsible for the observed pathogenic of WS1 in this pedigree. The genetic test confirmed the diagnosis of WS1 in the four patients from the studied pedigree. Conclusion: This present study demonstrated that genetic test based on WES, an effective alternative to regular clinical examinations, helps diagnose WS1. The newly identified PAX3 gene mutation can expand the understanding of WS1.

Comparison of cast films and hydrogels based on chitin nanofibers prepared using TEMPO/NaBr/NaClO and TEMPO/NaClO/NaClO2 systems.

Neutral TEMPO/NaClO/NaClO2 (TNN) oxidation, with NaClO2 as the primary oxidant under aqueous conditions at pH 6.8 was applied to selectively oxidize surface C6 primary hydroxyl groups of α-chitin to carboxylate groups. When 0.1 mmol TEMPO, 1 mmol NaClO and 20 mmol NaClO2 were added to 1 g α-chitin, the yield of water-insoluble oxidized chitin was 91.93 %, and the carboxylate content was 0.695 mmol/g. The TNN oxidized chitin (TNN-Ch) was mostly converted to individual nanofibrils by mechanical disintegration in water, with mostly widths of 20-24 nm and average lengths of 1 µm. Compared to chitin nanofibers produced by TEMPO/NaBr/NaClO system (TBN-ChNs), with average widths of 16.67 ±â€¯7.9 nm and average lengths of 770 ±â€¯170 nm, TNN-ChNs were wider, longer and had a higher aspect ratio; its films and hydrogels also showed better mechanical properties, which indicated the size effect on the nanofiber-based materials resulted from different oxidation process.