Biodegradable chitin nanofiber-alginate dialdehyde hydrogel: An injectable, self-healing scaffold for anti-tumor drug delivery.

Injectable hydrogels fabricated from natural polymers have attracted increasing attentions for their potential in biomedical application owing to the biocompatibility and biodegradability. A new class of natural polymer based self-healing hydrogel is constructed through dynamic covalent bonds. The injectable self-healing hydrogels are fabricated by introducing alginate aldehyde to form Schiff base bonds with the chitin nanofibers. These hydrogels demonstrate excellent self-healing properties, injectability, and pH-responsive sol-gel transition behaviors. As a result, they can serve as carriers to allow an effective encapsulation of doxorubicin (DOX) for drug delivery. Furthermore, these hydrogels exhibit excellent biocompatibility and degradability in vitro and in vivo. The sustained release of DOX from the hydrogels effectively suppresses tumor growth in animal models without causing significant systemic toxicity, suggesting their potential application in anti-tumor therapies.

Efficient fabrication of anisotropic regenerated cellulose films from bamboo via a facile wet extrusion strategy.

Bamboo, featuring fast growth rate and high cellulose content, is considered to be one of the most attractive feedstocks for degradable bio-materials as a substitute for plastics. However, those was limited to the fields of bamboo structural materials mainly by physical processes. Herein, we report a facile continuous wet extrusion strategy for scalable manufacturing of anisotropic regenerated cellulose films in alkali/urea aqueous solution for the first time. The bamboo cellulose solution was regenerated in H2SO4/Na2SO4/ZnSO4 aqueous solution to facilitate the construction of dense fibrils networks. Moreover, under the synergistic effect of shear orientations and stretching processes in wet extrusion molding, the cellulose networks promoted further orientated assembly into aligned fibrils. Therefore, these anisotropic cellulose hydrogels exhibited good mechanical properties, and the tensile strength was increased from 1.67 MPa of anisotropic cellulose hydrogel with 1.0 of stretching ration (ACH-1.0) to 2.13 MPa of ACH-1.4 with increasing stretching ratio from 1.0 to 1.4, which was about 1.34 times higher than that of the isotropic hydrogel fabricated by tape-casting. Moreover, ACH-1.4 exhibited commendable thermal stability and air barrier properties. This work demonstrated a simple and continuous bottom-up approach for fabrication of anisotropic bamboo-based cellulose hydrogels and films with excellent mechanical properties.

Chitinous Bioplastic Enabled by Noncovalent Assembly.

Natural polymeric-based bioplastics usually lack good mechanical or processing performance. It is still challenging to achieve simultaneous improvement for these two usual trade-off features. Here, we demonstrate a full noncovalent mediated self-assembly design for simultaneously improving the chitinous bioplastic processing and mechanical properties via plane hot-pressing. Tannic acid (TA) is chosen as the noncovalent mediator to (i) increase the noncovalent cross-link intensity for obtaining the tough noncovalent network and (ii) afford the dynamic noncovalent cross-links to enable the mobility of chitin molecular chains for benefiting chitinous bioplastic nanostructure rearrangement during the shaping procedure. The multiple noncovalent mediated network (chitin-TA and chitin-chitin cross-links) and the pressure-induced orientation nanofibers structure endow the chitinous bioplastics with robust mechanical properties. The relatively weak chitin-TA noncovalent interactions serve as water mediation switches to enhance the molecular mobility for endowing the chitin/TA bioplastic with hydroplastic processing properties, rendering them readily programmable into versatile 2D/3D shapes. Moreover, the fully natural resourced chitinous bioplastic exhibits superior weld, solvent resistance, and biodegradability, enabling the potential for diverse applications. The full physical cross-linking mechanism highlights an effective design concept for balancing the trade-off of the mechanical properties and processability for the polymeric materials.

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.

High-performance triboelectric nanogenerator based on chitin for mechanical-energy harvesting and self-powered sensing.

Environment issues and energy crisis call for eco-friendly, biodegradable and low-cost natural materials for the extensive application of distributed energy harvesting triboelectric nanogenerators (TENGs) and multi-functional self-powered sensors. Here, flexible, robust and transparent chitin films fabricated via non-freezing dissolution approach in KOH/urea were used as tribopositive material to assemble TENGs, which served as outstanding mechanical energy harvesters and multi-functional self-powered sensors. The tensile strength and elongation at break of the chitin film reached 84.7 MPa and 14.5%, better than most existing biodegradable-based films. The chitin-based TENG (CF-TENG) achieved open-circuit voltage up to 182.4 V, short-circuit current of 4.8 µA and maximum power density over 1.25 W m-2. Furthermore, the CF-TENG can be utilized as tactile sensors for handwriting recognition and health monitoring of subtle pressures, as well as non-contact sensation, exhibiting great potential as self-powered sensors and human-machine interfaces.

Polyphenol-driving assembly for constructing chitin-polyphenol-metal hydrogel as wound dressing.

The metal-polyphenol networks have attracted appealing attention for diverse biomedical applications due to their remarkable characteristics. Though various of metal-polyphenolic materials have been prepared, the homogeneous metal-polyphenol based hydrogel fabrication remains a challenge (e.g., quick aggregation). Herein, a facile and low-cost polyphenol-mediating non-covalent driven assembly strategy was developed for fabricating homogeneous chitin-polyphenol-metal hydrogels. Polyphenols not only noncovalently crosslinked chitin chains, but simultaneously captured metal nanomaterials from metal substrates and immobilized in chitin-polyphenol networks. A range of metal (Fe, Cu, Ti, Zn) and polyphenol (tannic acid, gallic acid, quercetin, pyrogallic acid) could be incorporated into this hydrogel framework. As a demonstration, the chitin-tannic acid-Cu hydrogel showed excellent antibacterial properties and significantly enhanced infected wound repair via promoting the cell proliferation and angiogenesis, showing the potential in wound dressing. The low cost, versatility and flexibility assembly process can be used to fabricate diverse polymer-polyphenol-metal hydrogel, thereby enabling their use in various applications.

Polyphenol-mediated chitin self-assembly for constructing a fully naturally resourced hydrogel with high strength and toughness.

Natural polymeric hydrogels are expected to serve as potential structural biomaterials, but, most of them are usually soft and fragile. Herein, a polyphenol-mediated self-assembly (PMS) strategy was developed to significantly enhance the chitin hydrogel strength and toughness at the same time, which is distinctive from the rigid-soft double-network energy-dissipation approaches. A polyphenol (tannic acid, TA as a model compound) was introduced to compete with the chitin chains self-assembly for simultaneously forming the weak chitin-TA and strong chitin-chitin networks. High-density noncovalent crosslinking involving hydrogen bonding and ionic and hydrophobic interactions endowed the PMS hydrogels with a high modulus and strength. The relatively weaker chitin-TA crosslinking acted as the sacrificial bonds to dissipate the energy, leading to the high toughness. The mechanical properties of the PMS chitin hydrogels depended on the TA concentration and ethanol aqueous coagulation, which mainly contributed to the hydrophobic and hydrophilic interactions formation, respectively. The fully naturally robust chitin-TA hydrogels exhibited considerable antibacterial properties, stomach acid solubility, and excellent biocompatibility and degradability, enabling their potential in food, biomedical, and sustainable applications.

Novel ZnO/N-halamine-Mediated Multifunctional Dressings as Quick Antibacterial Agent for Biomedical Applications.

Cutaneous hemorrhage often occurs in daily life which may cause infection and even amputation. This research aims to develop a novel chitosan dressing impregnated with ZnO/N-halamine hybrid nanoparticles for quick antibacterial performance, outstanding hemostatic potential, high porosity, and favorable swelling property through combining sonication and lyophilization processing. After 30 days of storage, about 90% bacterial cell viability loss could be observed toward both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli O157:H7 within 30 min of contact by colony counting method. The hybrids assembled much more platelet and red blood cell as compared with pure chitosan control. Moreover, the lower blooding clotting index value gave evidence that these composites could control hemorrhaging and reduce the probability of wound infection. No potential skin irritation and toxicity were detected using in vitro cytocompatibility and a skin stimulation test. Therefore, this work demonstrated a facile and cost-effective approach for the preparation of N-halamine-based hybrid sponges which show promising application for wound dressings.

Cellulose Acetate Nanofibrous Membranes for Antibacterial Applications.

BACKGROUNDS: N-halamine antibacterial materials have been extensively explored over the past few decades due to their fast inactivation of a broad spectrum of bacterial and rechargeability. Electrospun nanofibers loaded with N-halamines have gained great attention because of their enhanced antibacterial capability induced by the larger specific surface area. The patents on electrospun nanofibers (US20080679694), (CN2015207182871) helped in the method for the preparation of nanofibers. METHODS: In this study, a novel N-halamine precursor, 3-(3'-Chloro-propyl)-5,5-dimethylimidazolidine- 2,4-dione(CPDMH), was synthesized. Antimicrobial electrospun Cellulose Acetate (CA) nanofibers were fabricated through impregnating CPDMH as an antimicrobial agent into CA fibers by the bubble electrospinning. The surface morphologies of CA/CPDMH nanofibrous membranes were characterized by Scanning Electron Microscope (SEM). RESULTS: The chlorinated fibrous membranes (CA/CPDMH-Cl) exhibited effective antimicrobial activity against 100% of S. aureus and E. coli O157:H7 within 1 min and 5 min, respectively. The CA/CPDMH-Cl nanofibrous membranes showed good storage stability under the dark and excellent durability towards UVA light exposure. Meanwhile, the release of active chlorine from the chlorinated nanofibrous membranes was stable and safe. Besides, the addition of CPDMH could improve the mechanical property, and chlorination did not obviously affect the strength and elongation of the nanofibrous membranes. CONCLUSION: CPDMH could endow the electrospun CA nanofibers with powerful, durable and regenerable antimicrobial properties. It will provide a continuous and effective method for health-care relative industrial application.

PHB/PCL fibrous membranes modified with SiO2@TiO2-based core@shell composite nanoparticles for hydrophobic and antibacterial applications.

In order to prepare multifunctional fibrous membranes with hydrophobicity, antibacterial properties and UV resistance, we used silica and titanium dioxide for preparing SiO2@TiO2 nanoparticles (SiO2@TiO2 NPs) to create roughness on the fibrous membranes surfaces. The introduction of TiO2 was used for improving UV resistance. N-Halamine precursor and silane precursor were introduced to modify SiO2@TiO2 NPs to synthesize SiO2@TiO2-based core@shell composite nanoparticles. The hydrophobic antibacterial fibrous membranes were prepared by a dip-pad process of electrospun biodegradable polyhydroxybutyrate/poly-ε-caprolactone (PHB/PCL) with the synthesized SiO2@TiO2-based core@shell composite nanoparticles. TEM, SEM and FT-IR were used to characterize the synthesized SiO2@TiO2-based core@shell composite nanoparticles and the hydrophobic antibacterial fibrous membranes. The fibrous membranes not only showed excellent hydrophobicity with an average water contact angle of 144° ± 1°, but also appreciable air permeability. The chlorinated fibrous membranes could inactivate all S. aureus and E. coli O157:H7 after 5 min and 60 min of contact, respectively. In addition, the chlorinated fibrous membranes exhibited outstanding cell compatibility with 102.1% of cell viability. Therefore, the prepared hydrophobic antibacterial degradable fibrous membranes may have great potential application for packaging materials.

Cytocompatible quaternized carboxymethyl chitosan/poly(vinyl alcohol) blend film loaded copper for antibacterial application.

Antibacterial quaternized carboxymethyl chitosan/poly(vinyl alcohol)/Cu blend film (QCMCS/PVA/Cu blend film) was prepared by quaternary ammonium salt modified carboxymethyl chitosan (QCMCS), PVA and copper sulfate pentahydrate via the process of solution casting and ion adsorption. The successful preparation of QCMCS was proved by EA, NMR and FTIR, and the degree of quaternization is 71.86%. The QCMCS/PVA/Cu blend film was characterized by SEM, AFM and EDX, and the content of the copper is about 1 wt%. Tensile tests and TGA showed that the mechanical and thermal properties were improved after being loaded with copper ions. By loading with Cu2+, the blend film showed good antibacterial activities. About 98.3% of S. aureus and 99.9% of E. coli could be inactivated within 60 min. The cell cytotoxicity was also studied and the results showed that all the prepared films had acceptable cell viability and biocompatible, which indicates that this blend film has potential applications in packaging and biomedical materials.