Collagen/functionalized cellulose nanofibril composite aerogels with pH-responsive characteristics for drug delivery system.

In this work, carboxylated and amination modified cellulose nanofibrils (CNFs) were fabricated via the TEMPO catalytic oxidation system and diethylenetriamine, and collagen composite aerogels were fabricated through a simple self-assembly pretreatment and directional freeze-drying technology. Morphology analysis showed that the collagen composite aerogels had distinct layered-oriented double network structures after the self-assembly pretreatment. The intermolecular interactions between the collagen fibrils and functionalized CNFs (fCNFs) on the structures and properties of the composite aerogels were also examined through various characterization techniques. Water contact angle tests demonstrated the pH-responsive characteristics of the collagen/fCNF composite aerogels. Using 5-fluorouracil as the model drug, the pH-response mechanism was revealed. These results indicated that the collagen/fCNF composite aerogels exhibited excellent pH-responsive drug release capacities. Therefore, these pH-responsive collagen composite aerogels might have potential applications in industrial production in the biomedical, drug delivery, and tissue engineering fields.

Conductive, water-retaining and knittable hydrogel fiber from xanthan gum and aniline tetramer modified-polysaccharide for strain and pressure sensors.

Herein, we explored strategies for defoaming and controllable adjustment of spinnable and mechanical properties of polyanion polysaccharide-based hydrogels to fabricate conductive, water-retaining, and knittable hydrogel fibers for next-generation flexible electronics. Xanthan gum (XG) and aniline tetramer modified-polysaccharide (TMAT38) were crosslinked with sodium trimetaphosphate (STMP) and subsequently by Fe3+/Fe2+ ions coordination to prepare conductive and spinnable hydrogels. Polypropylene glycol was introduced as chemical antifoam, and solvent displacement method was adopted to improve mechanical and water-retaining properties. The glycerol-immersed XG5-TMAT38-STMP-Fe3+/CA-PPG hydrogel exhibited conductivity of 3.55×10-3-27.30×10-3 S/cm, storage modulus at linear viscoelastic region of 573 Pa-1717 Pa and self-healing percentage of 100 %-108 %. The 2 h glycerol-immersed hydrogel fibers with good flexibility, moisture retention and freezing tolerance were ready to bend and knit into fabrics. The hydrogel fiber braid possessed better conductivity, reliability and durability than the single hydrogel fiber as strain sensors. The hydrogel fiber fabric perceived tiny vibration triggered by swallowing, speaking and writing with good sensitivity and reproducibility. Furthermore, a three-component model was developed to evaluate response sensitivity and recoverability of the hydrogel fiber fabric-based pressure sensors, which facilitated understanding transient response of polymer-based hydrogel strain and pressure sensors.

High strength and biodegradable dielectric film with synergistic alignment of chitosan nanofibrous networks and BNNSs.

The development of biodegradable and robust dielectric capacitors with high breakdown strength and energy density are indispensable. Herein, the high strength chitosan/edge hydroxylated boron nitride nanosheets (BNNSs-OH) dielectric film was fabricated via combining the dual chemically-physically crosslinking and the drafting orientation strategy, which could induced BNNSs-OH and chitosan crosslinked network alignment within the film via covalent and hydrogen bonding interaction, leading to the comprehensive reinforcement of tensile strength from 126 to 240 MPa, the Eb from 448 to 584 MV m-1, the in-plane thermal conductivity from 1.46 to 5.95 W m-1 K-1 and energy storage density from 7.22 to 13.71 J cm-1, superior than the comprehensive evaluation of the reported polymer dielectrics. The dielectric film could be completely degraded in soil in 90 days, which opened a new path for the development of next-generation environment-friendly dielectrics with excellent mechanical and dielectric properties.

In situ synthesis of Ag/Ag2O-cellulose/chitosan nanocomposites via adjusting KOH concentration for improved photocatalytic and antibacterial applications.

This work proposed a facile way to construct cellulose/chitosan-loaded Ag/Ag2O nanocomposite films (ACC) from alkali/urea solution by increasing the content of alkali KOH in the solvent. The saturated alkali and hydroxyl groups of the cellulose and chitosan chains were accelerated to convert AgNO3 to Ag0. Ag2O served as nuclei to lower the energy barrier. The formation of Ag/Ag2O nanoparticles (NPs) endowed the cellulose bio-reduced Ag composites with multifunction and stronger photocatalytic activity. Ag/Ag2O NPs with the diameter of 139-360 nm were uniformly dispersed in the composite films, resulting in superior mechanical properties (64.6 MPa) and thermal stability. Almost 92 % of methyl orange was degraded under UV-irradiation within 40 min by ACC. After 3 runs of degradation, the photocatalytic abilities of ACC remained. Moreover, the films exhibited good antibacterial activities. The width of inhibition zones around ACC reached 9.2-12 mm and 8.6-10.4 mm for S. aureus and E. coli. The strategy provided a new avenue to construct multifunctional cellulose/chitosan materials for various applications, such as wastewater treatment, and electrocatalysis.

A fast curing assisted spray-coating method to fabricate a robust core-shell structured evaporator with stable solar vapor generation performance.

Solar driven interfacial vapor generation is considered to be an effective strategy to alleviate the impact of water crisis on human activities. However, great efforts of researchers have been devoted to improving the solar steam generation efficiency, while less attention has been paid to the long-term stability of evaporators. Herein, we proposed a robust core-shell structured evaporator prepared by a simple fast curing assisted spray-coating method. Owing to the inherent superelasticity of melamine-formaldehyde (MF) sponge, the finely designed novel 3D core-shell structure, and the quick curing of branched polyethyleneimine (BPEI) and 5-pentaerythritol pentaacrylate (5Acl) induced special knot shaped photothermal coating, the as-obtained evaporator (CB/MF) performed well in vapor generation with a high water evaporation rate of 2.082 kg m-2 h-1 under 1 sun illumination, and the evaporation efficiency reached 123.5%, which is comparable to the state-of-the-art artificial solar evaporator. Even in strict application situations, such as long-term recycling testing for 40 h, 500 compression-release cycles (20%, 40% or 60%), sonication for 12 h, or shaking for 30 h, the water evaporation rate of the obtained evaporator remains at a high level of above 2.00 kg m-2 h-1. Additionally, the evaporator shows effective purification toward high-concentration brine, acid-base solutions, simulated seawater, dye wastewater, and heavy metal wastewater, as well as reliable pure water, providing an outdoor application. With the advantages of a high evaporation rate, stable long-term vapor generation, and effective purification toward various non-potable water sources, we believe that the fabricated core-shell structured CB/MF evaporator is a promising candidate for practical solar steam generation.

Recent progress in regenerated cellulose-based fibers from alkali/urea system via spinning process.

Cellulose as the most abundant renewable polymer displays great potential to substitute the petroleum-derived synthetic polymers. However, cellulose is difficult to be melted or dissolved, which greatly restricts its development and utilization. Herein, the "green" alkali/urea aqueous system for cellulose dissolution is briefly summarized by illustrating the dissolving mechanism. The comparison of cellulose fibers from different solvent is presented. In addition, the recent achievements for the efficient and "green" preparation of regenerated cellulose fibers from alkali/urea system are also summarized. By investigating the effects of experimental conditions and technical parameters on the structure and performance of regenerated cellulose fibers, the improved fiber mechanical properties and the decreased production costs are achieved. Moreover, the preparation and application of cellulose-based functional fibers from alkali/urea system are also reviewed, together with the urgent challenges and future development perspectives, which provide the novel approach for the high value-added development and utilization of cellulose fibers.

Recent Developments of Tin (II) Sulfide/Carbon Composites for Achieving High-Performance Lithium Ion Batteries: A Critical Review.

The ever-increasing worldwide energy demand and the limited resources of fossil have forced the urgent adoption of renewable energy sources. Additionally, concerns over CO2 emissions and potential increases in fuel prices have boosted technical efforts to make hybrid and electric vehicles more accessible to the public. Rechargeable batteries are undoubtedly a key player in this regard, especially lithium ion batteries (LIBs), which have high power capacity, a fast charge/discharge rate, and good cycle stability, while their further energy density improvement has been severely limited, because of the relatively low theoretical capacity of the graphite anode material which is mostly used. Among various high-capacity anode candidates, tin (II) sulfide (SnS2) has been attracted remarkable attention for high-energy LIBs due to its enormous resource and simplicity of synthesis, in addition to its high theoretical capacity. However, SnS2 has poor intrinsic conductivity, a big volume transition, and a low initial Coulombic efficiency, resulting in a short lifespan. SnS2/carbon composites have been considered to be a most promising approach to addressing the abovementioned issues. Therefore, this review summarizes the current progress in the synthesis of SnS2/carbon anode materials and their Li-ion storage properties, with special attention to the developments in Li-based technology, attributed to its immense current importance and promising prospects. Finally, the existing challenges within this field are presented, and potential opportunities are discussed.

A new strategy to construct cellulose-chitosan films supporting Ag/Ag2O/ZnO heterostructures for high photocatalytic and antibacterial performance.

The industrial wastewater contaminants including dyes and bacteria have caused serious environmental pollutions. Herein, ternary Ag/Ag2O/ZnO heterostructure decorating cellulose-chitosan films were constructed via in situ synthesis. Cellulose and chitosan dissolved in alkali/urea solvent and regenerated in ethylene glycol to form cellulose/chitosan nanofiber network, which was an ideal supporter for ZnO and Ag nanoparticles and beneficial for recycle usage. The hydroxyl groups of cellulose and chitosan chains exposed and were utilized for the synthesis of Ag particles, as well as ZnO nanoparticles by biomineralization. The Ag/Ag2O/ZnO decorating cellulose/chitosan (AZ@CC) films exhibited excellent antibacterial activity against Staphylococcus aureus and Escherichia coli. The width of inhibition zones around AZ@CC films reached 10.0-19.6 mm and 12.4-15.0 mm for S. aureus and E. coli, respectively. Moreover, AZ@CC films exhibited good photocatalytic activity against methyl orange (MO), almost 97% degradation of methyl orange (MO) within 50 min was achieved with the assistance of AZ@CC film. Importantly, the nanocomposite films exhibited excellent tensile strength and thermal stability. This facile and eco-friendly approach provided a new route to utilize cellulose and chitosan advantages for constructing multifunctional materials.

Incorporation of Layered Rectorite into Biocompatible Core-Sheath Nanofibrous Mats for Sustained Drug Delivery.

Searching for drug carries with controlled release and good biocompatibility has always been one of the research hotspots and difficulties. Herein, core-sheath nanofibrous mats (NFs) consisting of biocompatible poly(ethylene oxide) (PEO, core) and poly(l-lactic acid) (PLLA, sheath) for drug delivery were fabricated via coaxial electrospinning strategy. The nontoxic layered silicate rectorite (REC) with 0.5-1 wt % amount was introduced in the sheath for sustained drug delivery. Layered REC could be intercalated with PLLA macromolecule chains, leading to the densified structure for loading and keeping doxorubicin hydrochloride (DOX) while reversibly capturing and releasing DOX to delay the drug migration due to its high cation activity. The addition of REC in NFs could delay the initial burst release of DOX and prolong the residence time from 12 to 96 h. Moreover, DOX-loaded core-sheath NFs had in vitro culture with strong antitumor activity, which was confirmed by cytotoxicity results and live and dead assay. HepG2 tumor-bearing xenograft further demonstrated the tumor-suppression effect and the excellent safety of the DOX-loaded core-sheath NFs in vivo. The constructed NFs as drug carriers showed great potential in the local treatment of solid tumors.

Highly Stretchable Sheath-Core Yarns for Multifunctional Wearable Electronics.

Flexible electronic devices with strain sensing and energy storage functions integrated simultaneously are urgently desirable to detect human motions for potential wearable applications. This paper reports the fabrication of a cotton/carbon nanotube sheath-core yarn deposited with polypyrrole (PPy) for highly multifunctional stretchable wearable electronics. The microscopic structure and morphology of the prepared sheath-core yarn were characterized by scanning electron microscopy and Fourier transform infrared spectrometry. A mechanical experiment demonstrated its excellent stretchable capacity because of its unique spring-like structure. We demonstrate that the sheath-core yarn can be used as wearable strain sensors, exhibiting an ultrahigh strain sensing range (0-350%) and excellent stability. The sheath-core yarn can be used in highly sensitive real time monitoring toward both subtle and large human motions under different conditions. Furthermore, the electrochemical performance of the sheath-core yarn was characterized by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The measured areal capacitance was 761.2 mF/cm2 at the scanning rate of 1 mV/s. The method of spinning technology may lead to new exploitation of CNTs and PPy in future wearable electronic device applications.

Rheological and ion-conductive properties of injectable and self-healing hydrogels based on xanthan gum and silk fibroin.

The hydrogels with injectable and self-healing properties were prepared from xanthan gum (XG) and silk fibroin (SF) by using sodium trimetaphosphate (STMP) as crosslinker. A three-stage model of oscillation-shear-oscillation experiment was designed to mimic injection process and to observe destruction and regeneration of the hydrogels after shear. The XG3-SF-STMP hydrogels immediately recovered to original storage modulus of 80.6%-93.8% on removing shear. The hydrogels were 3D printed into the self-supporting constructions of hydrogel fibers with connected porous structures, and the XG3-SF-STMP hydrogel fibers exhibited smaller width than XG3-STMP. Oscillation rheological behavior indicated that XG3-SF-STMP hydrogels formed rapidly and exhibited more solid-like gel behavior than XG3-STMP. The hydrogel structures were destroyed under a strain (100%) larger than critical strain, but were rebuilt under a small strain (1%) with recovery ratio of 91.36-93.96% within 120 s, suggesting a self-healing property. Introduction of SF particles into XG3-STMP crosslinked networks improved stiffness and retained recoverability. Carboxyl and phosphate groups in the hydrogel networks are beneficial for XG3-SF-STMP hydrogels to absorb enough liquid electrolytes, leading to effective ionic conductivity. The ion-conductive hydrogel with injectable, self-healing, controlled release and non-cytotoxic properties possesses a promising prospect for tissue engineering and drug release application.

Rheological and controlled release properties of hydrogels based on mushroom hyperbranched polysaccharide and xanthan gum.

A hyperbranched polysaccharide, coded as TM3a, was extracted from the Pleurotus tuber-regium sclerotia. TM3a was hybridized with xanthan gum (XG) by chemical crosslinking using sodium trimetaphosphate (STMP) to obtain new hydrogels with self-healing and release-controlled properties. The oscillatory rheological measurements indicated that chemically crosslinking was happened immediately on mixing STMP solutions into the XG-TM3a solutions, and the crosslinked network developed slightly as time increased. The resultant hydroges were disturbed into the loose structures and regrouped the microstructure in 2 min when a large and a small amplitude oscillation were applied in turn, suggesting a self-healable property. The XG-TM3a-STMP hydrogels exhibited shear-thinning behavior with yield stress. The storage modulus of the XG5-TM3a-STMP hydrogel was 445.2 Pa at 1% strain and 243.3 Pa at 100% strain, and yield stress was 160.6 Pa, which was higher than the corresponding value of the XG5-STMP hydrogel. The morphological observation indicated the aggregates of double helical XG chains exhibited directional arrangement, and were combined with the TM3a aggregates to constitute a network of hierarchical structures. The hybrid hydrogels with enhanced mechanical properties displayed good drug loading efficiencies and sustained drug release properties.

Carboxymethylated hyperbranched polysaccharide: Synthesis, solution properties, and fabrication of hydrogel.

The periphery of hyperbranched polysaccharides has many end groups that can be functioned and used as sites to interact with their surroundings. A water-insoluble hyperbranched ß-d-glucan, coded as TM3a, extracted from sclerotia of an edible fungus (Pleurotus tuber-regium), was fractionated and modified chemically to obtain carboxymethylated derivatives (CTM3a). The solution properties of the carboxymethylated polysaccharides were studied systematically in phosphate buffer saline at 37 °C. The results indicated that the carboxymethylated glucans still kept hyperbranched structure after carboxymethylation, and existed as a swollen sphere-like chain conformation. The introduction of carboxymethylated groups permitted the formation of hydrogels through crosslinking CTM3a and silk fibroin with carbodiimide chemistry. The resultant hydrogels with porous and interconnected structure displayed good mechanical and swelling properties. This work provides some valuable and fundamental information of the natural hyperbranched polysaccharide from mushroom for further application in biomedical devices and tissue engineering.