Activating Adsorption Sites of Waste Crayfish Shells via Chemical Decalcification for Efficient Capturing of Nanoplastics.

The property of being stubborn and degradation resistant makes nanoplastic (NP) pollution a long-standing remaining challenge. Here, we apply a designed top-down strategy to leverage the natural hierarchical structure of waste crayfish shells with exposed functional groups for efficient NP capture. The crayfish shell-based organic skeleton with improved flexibility, strength (14.37 to 60.13 MPa), and toughness (24.61 to 278.98 MJ m-3) was prepared by purposefully removing the inorganic components of crayfish shells through a simple two-step acid-alkali treatment. Due to the activated functional groups (e.g., -NH2, -CONH-, and -OH) and ordered architectures with macropores and nanofibers, this porous crayfish shell exhibited effective removal capability of NPs (72.92 mg g-1) by physical interception and hydrogen bond/electrostatic interactions. Moreover, the sustainability and stability of this porous crayfish shell were demonstrated by the maintained high-capture performance after five cycles. Finally, we provided a postprocessing approach that could convert both porous crayfish shell and NPs into a tough flat sheet. Thus, our feasible top-down engineering strategy combined with promising posttreatment is a powerful contender for a recycling approach with broad application scenarios and clear economic advantages for simultaneously addressing both waste biomass and NP pollutants.

Dopamine-Modified Chitosan Patterning Hydrogel with Dynamic Information Storage Ability.

The storage of dynamic information in hydrogels has aroused considerable interest regarding the multiple responsiveness of soft matter. Herein, we propose an electrical writing methodology to prepare dopamine (DA)-modified chitosan hydrogels with a dynamic information storage ability. A pH-responsive chitosan hydrogel medium was patterned by cathodic writing to in situ generate OH- in the writing area, at which dopamine underwent an auto-oxidation reaction in the locally alkaline environment to generate a dark color. The patterned information on the hydrogel can be encoded simply by electrical signals. The speed of information retrieval is positively correlated with the charge transfer during the electrical writing process, and the hiding of information is negatively correlated with the environmental stimulus (i.e., dopamine concentration, pH value, etc.). To showcase the versatility of this medium for information storage and the precision of the pattern, a quick response (QR) code is electronically written on dopamine-modified chitosan hydrogel and can be recognized programmably by a standard mobile phone. The results show that electrical regulation is a novel means to program the information storage process of hydrogels, which inspires future research on structural and functional information storage using stimulus-responsive hydrogels.

A Universal Biomacromolecule-Enabled Assembly Strategy for Constructing Multifunctional Aerogels with 90% Inorganic Mass Loading from Inert Nano-Building Blocks.

Inert inorganic nano-building blocks, such as carbon nanotubes (CNTs) and boron nitride (BN) nanosheets, possess excellent physicochemical properties. However, it remains challenging to build aerogels with these inert nanomaterials unless they are chemically modified or compounded with petrochemical polymers, which affects their intrinsic properties and is usually not environmentally friendly. Here, a universal biomacromolecule-enabled assembly strategy is proposed to construct aerogels with 90 wt% ultrahigh inorganic loading. The super-high inorganic content is beneficial for exploiting the inherent properties of inert nanomaterials in multifunctional applications. Taking chitosan-CNTs aerogel as a proof-of-concept demonstration, it delivers sensitive pressure response as a pressure sensor, an ultrahigh sunlight absorption (94.5%) raising temperature under light (from 25 to 71 °C within 1 min) for clean-up of crude oil spills, and superior electromagnetic interference shielding performance of up to 68.9 dB. This strategy paves the way for the multifunctional application of inert nanomaterials by constructing aerogels with ultrahigh inorganic loading.

Programmable Electrical Signals Induce Anisotropic Assembly of Multilayer Chitosan Hydrogels.

Multilayer hydrogels are widely used in biomedical-related fields due to their complex and variable spatial structures. Various strategies have been developed for preparing multilayer hydrogels, among which electrically induced self-assembly provides a simple and effective method for multilayer hydrogel fabrication. By application of an oscillatory electrical signal sequence, multilayer hydrogels with distinct boundaries can be formed according to the provided programmable signals. In this work, we establish an electrical field in microfluidics combined with polarized light microscopy for in situ visualization of anisotropic construction of multilayer chitosan hydrogel. The noninvasive, real-time birefringence images allow us to monitor the orientation within the hydrogel in response to electrical signals. An increased birefringence was observed from the solution-gel side to the electrode surface side, and a brief electrical signal interruption did not affect the anisotropic assembly process. This understanding of the oscillatory electrical signal-induced hydrogel anisotropy assembly allows us to fabricate chitosan hydrogels with a complex and spatially varying structure.

A fluorescent sensor based on strand displacement amplification and primer exchange reaction coupling for label-free detection of miRNA.

MicroRNAs (miRNAs) are closely associated with human disease occurrence, including cancers, diabetes, inflammation, heart diseases, and viral infections, and their rapid and accurate detection is vital for the diagnosis and treatment of these diseases. Based on one-step reaction of strand displacement amplification (SDA) and primer exchange reaction (PER), a label-free and highly sensitive miRNA-21 detection strategy was developed. In this strategy, the target miRNA-21 binds directly to the hairpin template, triggering the SDA reaction and generating a large number of single strand DNAs as primers for PER amplification. With the help of polymerase, plenty of G-quadruplex fragments of different lengths were accumulated, and the organic dye thioflavin T selectively binds to these G-quadruplex fragments to produce a strong fluorescent signal. There is a wide detection range in this method, miRNA-21 can be detected in the range of 10 fM - 1 nM, the detection limit is low (1.25 fM). This method has good specificity and can effectively distinguish single-base mismatches of miRNA. In addition, the versatility of the method was validated by changing the target recognition site of SDA template.

Long-term antibacterial activity by synergistic release of biosafe lysozyme and chitosan from LBL-structured nanofibers.

Biosafe antibacterial agents are urgently demanded in treating infection especially chronic infection. However, efficient and controlled release of those agents remains great challenging. Two nature-derived agents, lysozyme (LY) and chitosan (CS), are selected to establish a facile method for long-term bacterial inhibition. We incorporated LY into the nanofibrous mats, then deposited CS and polydopamine (PDA) on the surface by layer-by-layer (LBL) self-assembly. In this vein, LY is gradually released with the degradation of nanofibers, and CS is rapidly disassociated from the nanofibrous mats to synergistically result in a potent inhibition against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) over a period of 14 days. Besides long-term antibacterial capacity, LBL-structured mats could readily achieve a strong tensile stress of 6.7 MPa with an increase percentage of up to 103%. The enhanced proliferation of L929 cells arrives at 94% with help of CS and PDA on the surface of nanofibers. In this vein, our nanofiber has a variety of advantages including biocompatibility, strong long-term antibacterial effect, and skin adaptability, revealing the significant potential to be used as highly safe biomaterial for wound dressings.

Silk fibroin-chitosan aerogel reinforced by nanofibers for enhanced osteogenic differentiation in MC3T3-E1 cells.

Proper bone scaffolds should be biocompatible, mechanically robust and porous for cell migration. Here, pure silk fibroin (SF)- chitosan (CS) aerogel scaffolds reinforced with different amount of SF nanofibers (SF-CS/NF1%, SF-CS/NF2% and SF-CS/NF3%) are prepared for bone regeneration. Surface morphology and composition were analyzed to ensure successful integration of each component. Incorporating 3 % nanofibers endowed the aerogels with a resistance to 3.5 times the compressive stress of the pure SF-CS aerogels. The benefits of nanofibers were also confirmed by the high porosity of 72.3 ± 1.3 %, the regulated pore size and the high-water uptake ratio of 1770.4 ± 156.8 %. Enhanced cell viability of the aerogel scaffolds was verified with Cell Counting Kit-8 (CCK-8) assays, and confocal microscopy and scanning electron microscopy (SEM) images were taken to assess the cell migration and distribution. The cell differentiation on the aerogel scaffolds was evaluated with enzyme-linked immunosorbent assay (ELISA). Significantly higher level of Collagen type I (Col-I), osteocalcin (OCN), osteopontin (OPN), and alkaline phosphatase (ALP) expression was observed on SF-CS/NF3% aerogels. This biocompatible nanofiber-reinforced aerogel scaffold facilitates osteogenic differentiation by rougher surface, enhanced mechanical strength and well-regulated pores. Thus, as-prepared scaffolds may be further applied in bone regeneration field.

Fabrication of an exosome-loaded thermosensitive chitin-based hydrogel for dental pulp regeneration.

Injective thermosensitive hydrogels are considered promising scaffolds to trigger dental pulp regeneration in devitalized human teeth. In this study, we developed a hydroxypropyl chitin (HPCH)/chitin whisker (CW) thermosensitive hydrogel with enhanced mechanical properties and biological activities. Exosomes can serve as biomimetic tools for tissue engineering, but the rapid clearance of unconjugated exosomes in vivo limits their therapeutic effects. To address this challenge, exosomes were isolated from human pulp stem cells (hDPSCs) and directly embedded into the HPCH/CW pre-gel to form an exosome-loaded hydrogel (HPCH/CW/Exo). The exosome-loaded thermosensitive hydrogel can be easily injected into an irregular endodontic space and gelated in situ. In vitro cell experiments proved that the delivery of exosomes significantly improved the ability of hydrogels to promote odontogenesis and angiogenesis. Meanwhile, in vivo animal experiments revealed the formation of new dental pulp-like tissues in an implanted tooth root model. Therefore, the proposed hydrogel provides a great potential alternative to traditional root canal therapy in dental clinics.

Electrically induced anisotropic assembly of chitosan with different molecular weights.

Anisotropic hydrogel is emerging as an important soft matter in the field of bionics and bioactuators, owing to its outstanding mechanical toughness and strength. Understanding the dynamic construction process of anisotropic hydrogel is beneficial for matching subsequent application. In this work, we establish an electrical field in microfluidics for the in-situ real time visualization of anisotropic assembly of chitosan, an amino polysaccharide. Polarized light microscopy is adopted to observe the dynamic growth of chitosan with different molecular weights. The results demonstrate that electrical signal has a profound influence on anisotropic assembly process of chitosan. It is interesting to notice that high oriented structure can be found in chitosan hydrogel with large molecular weight, which exhibits a dense and compact structure. This work provides a new perspective for predicting and controlling the formation of different molecular weights anisotropic chitosan hydrogels, which permit the rational design of chitosan hydrogels with excellent mechanical properties and specific functions.

A novel DNA detection using spherical identification probe and strand displacement reaction-initiated silver nanocluster switch.

Herein, we developed a novel fluorescent assay using spherical identification probes and toehold-mediated strand displacement reaction-initiated silver nanoclusters (AgNCs) "on-off" signal switch. In this strategy, the target was captured by the spherical probes to induce the activity of exonuclease III (Exo III), catalyzing the cyclic cleavage of substrates to produce a mass of trigger strands. After magnetic bead separation, the intermediates in the supernatant activated downstream toehold-mediated strand displacement reaction to change the structure of silver nanocluster templates, leading to fluorescence intensity reduction. Furthermore, it is demonstrated that the application of spherical identification probes could reduce the signal leakage and the limit of detection. In addition, AgNCs with perfect optical property were ingeniously combined to realize signal output, which reduced the cost and time of synthesis. Under the optimal conditions, the sensing method displayed a good linear range from 250 pM to 25 nM with a detectable minimum concentration of 250 pM. And the practical application potential in complex biological matrices was also evaluated. Considering these advantages, this constructed strategy opens a new path for nucleic acid detection with better performance. A simple, label- and hairpin-free fluorescent system based on spherical identification probe and toehold-mediated strand displacement reaction-initiated silver nanoclusters (AgNCs) "on-off" signal switch was successfully constructed to detect target DNA.

Ultra-low protein residue of chitosan by one step H2O2 and sodium dodecyl sulfate treatment.

Residual protein in chitosan-based biomaterials may cause inflammation, allergy, and immune rejection after surgery, impeding their clinical application. Facile production of chitosan with ultra-low protein content (residual protein <0.2 %) is yet to be addressed. Herein, we proposed a one-step method for preparing chitosan with residue protein content <0.2 % by using hydrogen peroxide and sodium dodecyl sulfate, which is simple, time-saving, cost-effective, and acid/alkali-free. Notably, the molecular weight of chitosan can be reduced simultaneously. The effects of experimental parameters (i.e. hydrogen peroxide concentration (0.01 %-1 %), SDS concentration (5 %-20 %), and reaction temperature (50 °C-70 °C)) on the protein removal and molecular weight decrease were systematically analyzed by response surface methodology. The results show that temperature and H2O2 concentration are the main parameters affecting the deproteinization of chitosan. Further characterizations on the resulting ultra-low protein residue chitosan revealed unchanged chemical structure, enhanced crystallinity, and reduced thermal stability. The proposed one-step deproteination method may have great potential for industrial mass production of ultra-low protein residue chitosan.

Electrodeposition induced covalent cross-linking of chitosan for electrofabrication of hydrogel contact lenses.

To meet the requirement of personalization, there is an urgent need to develop a simple, efficient and versatile manufacturing method for customized contact lens manufabrication. Here, we report a novel electrofabrication methodology (i.e., electrodeposition) for the fabrication of hydrogel contact lenses, which can induce covalent cross-linking between chitosan and epichlorohydrin simultaneously. The transmittance and toughness of hydrogels are improved by electrochemical cross-linking without affecting their oxygen permeability. Furthermore, the geometry of the chitosan based hydrogel contact lenses can be customized simply by the electrode template, and its characteristics can be regulated by electrical signals and electrochemical cross-linking. The electrodeposited hydrogel contact lenses have good optical properties, mechanical properties and biocompatibility, and their anti-adhesion properties to Staphylococcus aureus are close to commercial contact lenses. This work reveals the mechanism of electrochemical cross-linking between chitosan and epichlorohydrin and provides an alternative method for contact lens fabrication.

Carboxymethyl chitosan assembled piezoelectric biosensor for rapid and label-free quantification of immunoglobulin Y.

Immunoglobulin Y (IgY) proves advantageous to IgG in prophylaxis and diagnosis. Quantification of IgY is therefore becoming a topic of interest. Here, we demonstrate a piezoelectric biosensor with carboxymethyl chitosan (CMCS) as the immobilization matrix. Gelation and hydrophilic nature of CMCS are favored to form a crosslinked matrix for antibody immobilization, and a comparison was made between carboxymethyl cellulose (CMC) and CMCS to investigate the benefits of such substitution. Calibration from 500 ng/mL to 200 µg/mL was established in buffer with the detection limit (LOD) down to 270 ng/mL, confirming its feasibility. As-prepared biosensor effectively prevents non-specific binding of bovine serum albumin (BSA) and lysozyme. Each real-time assay took 15 min including sensor regeneration, which can be further reduced to 4 min for signal readout only, ready for both repeated measurements after regeneration and disposable devices. Thus, as-prepared biosensor offers a rapid, label-free and cost-effective approach for IgY quantification.

Electrical signals regulate the release of insulin from electrodeposited chitosan composite hydrogel: An in vitro and in vivo study.

Electrical signal controlled drug release from polymeric drug delivery system provides an efficient way for accurate and demandable drug release. In this work, insulin was loaded on inorganic nanoplates (layered double hydroxides, LDHs) and coated on a copper wire by co-electrodeposition with chitosan. The formed structure in chitosan composite hydrogel entrapped insulin efficiently, which were proved by various techniques. In addition, the drug loaded chitosan composite hydrogel demonstrated good biocompatibility as suggested by cell attachment. In vitro drug release experiment showed fast responsive pulsed release of insulin by biasing electrical signals. The in vivo experiment in diabetic rats revealed controllable insulin release in plasma and stable decrease of blood glucose can be achieved by using appropriate electrical signal. In addition, HE staining suggested negligible effect to the tissue by electrical signals. This work suggests that the electrical signal controlled insulin release from chitosan composited hydrogel may be a promising administration route for insulin.

Tubular chitosan hydrogels with a tuneable lamellar structure programmed by electrical signals.

The discovery of facile methods to create complex lamellar structures in hydrogels, which mimic the exquisite structures in nature, remains a great challenge. In this work, an ordered lamellar structured hydrogel from the stimuli-responsive amino-polysaccharide chitosan is fabricated by an electro-assembly process, during which the diffusion of OH- and the electrophoresis of the chitosan chains play important roles. Importantly, a complex ordered/disordered structure of chitosan hydrogel can be regulated with high fidelity by programming the input electrical signals.

Hollow chitosan hydrogel tube with controllable wrinkled pattern via film-to-tube fabrication.

Due to mechanical instability, surface wrinkles form spontaneously in plants, animals and human beings for propagation and enhanced surface functionality. However, there remains tremendous challenge in mimicking such exquisite structure at a micro/nanoscale in lab. Herein, we report an approach to converting an electrodeposited chitosan hydrogel film into a hollow tube with controllable wrinkle wavelength and amplitude via soaking the film in acidic sodium dodecyl sulfate (SDS). Notably, wrinkled pattern can be controlled by a self-design device through modulating the shrinkage ratio. The resultant wrinkled hydrogel tube with adjustable wall thickness, outer diameter shows excellent mechanical strength, anti-fatigue ability, recoverability and flexibility. It is demonstrated that 2D/3D complicated hollow framework with wrinkled pattern can be customized on demand. This facile strategy not only provides a feasible approach to preparing hydrogel tube with wrinkles, but also points to possible pathways for bioengineering more complicated materials from natural polymers.

Highly sensitive formaldehyde sensors based on CuO/ZnO composite nanofibrous mats using porous cellulose acetate fibers as templates.

An innovative formaldehyde sensor based on CuO/ZnO composite nanofibrous mats (C-NFMs) coated quartz crystal microbalance (QCM), which is capable of stable determination of formaldehyde gas at ambient temperatures sensitively and selectively, has been successfully fabricated. Triaxial and highly porous C-NFMs with high surface area (126.53 m2 g-1) were synthesized by electrospinning a sol-gel cellulose acetate (CA)/CuAc2/ZnAc2 complex solution and following by calcination process. Benefiting from the unique heterojunction structure, immense pore interconnectivity and large surface area of C-NFMs, the as-developed QCM sensors exhibited an extremely low limit of detection (LOD) down to 26 ppb and a limit of quantification value equals to 87 ppb. Besides, the C-NFMs coated QCM sensors also demonstrated short response times (80s), the long-term stability during 3 weeks as well as good selectivity to formaldehyde over diverse volatile organic compounds. The sorption equilibrium in the adsorption process of QCM coated sensors was well met with the Freundlich model, which certified the heterogeneous adsorption between formaldehyde gas and C-NFMs.

Janus Fibrous Mats Based Suspended Type Evaporator for Salt Resistant Solar Desalination and Salt Recovery.

Solar desalination has been recognized as an emerging strategy for solving the pressing global freshwater crisis. However, salt crystallization at the photothermal interface frequently causes evaporator failure. In addition, arbitrary discharge of concentrated brine produced during desalination results in potential ecological impacts as well as wastage of valuable minerals. In the present work, a suspended-type evaporator (STEs) constructed using Janus fibrous mats is reported. The fibrous structure wicks brine to the evaporation layer and the salt gets confined in the evaporation layer until crystallization for zero liquid discharge due to the suspended design. Enhanced evaporation is observed because STEs have an additional low-resistance vapor escape path directly from the evaporation layer to the atmosphere compared to traditional floating Janus evaporators. Moreover, owing to the drastically different wettability on both sides, the evaporator allows salt crystallization only on the hydrophilic bottom layer, thus eliminating salt accumulation at the hydrophobic photothermal interface. With this unique structural design, the proposed evaporator not only maintains a high evaporation rate of 1.94 kg m-2 h-1 , but also demonstrates zero liquid discharged salt resistance and ideal recovery of the mineral in brine.

Antifatigue Hydration-Induced Polysaccharide Hydrogel Actuators Inspired by Crab Joint Wrinkles.

Joint wrinkles in animals facilitate frequent bending and contribute to the duration of the joint. Inspired by the morphology and function of joint wrinkles, we developed a bionic hydration-induced polymeric actuator with constructed wrinkles at the selected area. Specifically, we adopt electrical writing to create defined single and double cross-linking regions on chitosan (CS) hydrogel. The covalent cross-linking network was constructed by electrical writing-induced covalent cross-linking between CS chains and epichlorohydrin. Subsequent treatment of sodium dodecyl sulfate allows electrostatic cross-linking at the unwritten area with the simultaneous formation of surface wrinkles. The resulting single and double cross-linking hydrogel demonstrates spontaneous deformation behaviors by the influx and efflux of H2O to the electrostatic cross-linking domain under different ion concentrations. Importantly, the wrinkle structure endows the hydrogel with extraordinary antifatigue bending performance. By regulating the surface morphology and spatial cross-linking, we can design novel biomimetic polysaccharide hydrogel actuators with fascinating functions.