Green, chemical-free, and high-yielding extraction of nanocellulose from waste cotton fabric enabled by electron beam irradiation.

Recycling and high-value reutilization of waste cotton fabrics (WCFs) has attracted a widespread concern. One potential solution is to extract nanocellulose. Sulfuric acid hydrolysis is a conventional method for the production of nanocellulose with high negative charge from WCFs. However, the recycling and disposal of chemicals in nanocellulose production, along with low yields, remain significant challenges. Consequently, there is a pressing need for a sustainable method to produce nanocellulose at higher yield without the use of chemicals. Herein, we propose a green, sustainable and chemical-free method to extract nanocellulose from WCFs. The nanocellulose displayed a rod-like shape with a length of 50-300 nm, a large aspect ratio of 18.4 ± 2 and the highest yield of up to 89.9 %. The combined short-time and efficient two-step process, involving electron beam irradiation (EBI) and high-pressure homogenization (HPH), offers a simple and efficient alternative approach with a low environmental impact, to extract nanocellulose. EBI induced a noticeable degradation in WCFs and HPH exfoliated cellulose to nano-size with high uniformity via mechanical forces. The as-prepared nanocellulose exhibits excellent emulsifying ability as the Pickering emulsion emulsifier. This work provides a facile and efficient approach for nanocellulose fabrication as well as a sustainable way for recycle and reutilization of the waste cotton fabrics.

Injectable nano-composite hydrogels based on hyaluronic acid-chitosan derivatives for simultaneous photothermal-chemo therapy of cancer with anti-inflammatory capacity.

Nowadays, the photothermal therapy (PTT) has received widespread attention and research by rapidly killing tumors with local high temperature. However, due to the irregular edges of tumor and the blurred boundary between normal and necrotic tissues, the desirable treatment cannot be achieved by the single PTT, and excessive heat will cause serious inflammation in local tissues. Herein, an injectable composite hydrogel is prepared by the oxidized hyaluronic acid (OHA) and hydroxypropyl chitosan (HPCS) via the imine bonds, which is employed as the delivery substrate for functional substances. In the gel medium, the mesoporous polydopamine (MPDA) nanoparticles are incorporated as the high efficiency photothermal agent and a reservoir of DOX, which can achieve the good photothermal conversion performance and pulsed drug release. Besides, the addition of the curcumin-cyclodextrin host-guest inclusion complex (CUR@NH2-CD) in the composite hydrogel could reduce the inflammation caused by PTT. The composite hydrogel shows favorable the Hepa1-6 tumor inhibition in vivo by virtue of the comprehensive effect of the admired photothermal efficacy of MPDA, chemotherapy of DOX and anti-inflammatory of CUR. It can be predicted that the composite hydrogel has a broad prospect in the field of comprehensive therapy for tumor.

Environmentally Stable, Stretchable, Adhesive, and Conductive Organohydrogels with Multiple Dynamic Interactions as High-Performance Strain and Temperature Sensors.

Nowadays, with the rapid development of artificial intelligence, conductive hydrogel-based sensors play an increasingly vital role in health monitoring and temperature sensing. However, the perfect integration of the environmental stability and applied performance of the hydrogel has always been a challenging and significant problem. Herein, we report an environmentally tolerant, stretchable, adhesive, self-healing conductive gel through multiple dynamic interactions in the water/glycerol/ionic liquids medium, which can be used as a high-performance strain and temperature sensor. The random copolymer poly(acrylic acid-co-acetoacetoxyethyl methacrylate) interacts with the branched poly(ethylene imine) (PEI) and Zr4+ ions via the dynamic covalent enamine bonds, coordinations, and electrostatic interactions to improve stretchable (1300%), compressible, fatigue-resistant (1000 cycles at 50% strain), and self-healing performance (95%, 24 h). The combination of water/glycerol/ionic liquids imparts the resulting gel with excellent electrical conductivity, anti-drying, and anti-freezing performance. By means of the above excellent performance, the gel could be used as the flexible strain or pressure sensor with high sensitivity and stability for the detection of the movement, expression, handwriting, pronouncing, and electrocardiogram (ECG) signals in various models. Meanwhile, the resulting gel can be assembled as the temperature sensor to trace the change of temperature accurately and steadily, which has a wide operating window (0 to 100 °C), an ultralow detection limit (0.2 °C), and high sensitivity (2.1% °C-1). It is believed that the strategy for the multifunction and high-performance gel will blaze a new trail for the smart device in health management, temperature detection, and information transmission under various environmental conditions.

Superior, Environmentally Tolerant, Flexible, and Adhesive Poly(ionic liquid) Gel as a Multifaceted Underwater Sensor.

In recent years, gel-based sensors have been widely considered and fully developed. However, it is of vital importance, yet rather challenging to achieve a multifaceted gel, which can unify the advantages of favorable conductivity, high adhesion, excellent environmental resistance, and so forth and be applied in various harsh conditions. Herein, an ideal, extremely stable, adhesive, conductive poly(ionic liquid) gel (PILG) was designed via a one-step photoinitiated radical polymerization based on 1-vinyl-3-butylimidazolium bis(trifluoromethylsulfonyl)imide (VBIm-NTf2) cross-linked with ethylene glycol dimethacrylate (EGDMA) in methyltributylammonium bis(trifluoromethanesulfonyl)imide (N1444-NTf2) medium. There are abundant hydrophobic butyl chains and fluorinated groups in VBIm-NTf2 and N1444-NTf2, which can impart the PILG with stable conductivity, excellent environmental tolerance, and adhesion even in water due to the ion-dipole and ion-ion interactions. The resulting PILG can be assembled as a soft and smart sensor that can be applied in specific conditions such as underwater or undersea and even in dynamic water, achieving a stable signal transmission. Meanwhile, the PILG can be utilized as a flexible electrode to convey ECG signals in air or water whether it is in the static or dynamic state. Therefore, it is envisioned that this novel PILG will serve as a hopeful electrical device for signal detection and healthy management in specific environments.

Antibacterial thyme oil-loaded zwitterionic emulsion hydrogels.

Emulsion hydrogels are structurally composite materials combining the advantages of emulsions and hydrogels with the ability to accommodate hydrophobic and hydrophilic components in one system. It is a promising strategy for the excellent encapsulation and delivery of many bioactive ingredients. In this work, the thyme oil-loaded zwitterionic emulsion hydrogels are constructed by the cellulose acetoacetate-horseradish peroxidase-hydrogen peroxide-initiated (CAA-HRP-H2O2-initiated) ternary enzyme-mediated polymerization of the thyme oil-in-water (O/W) emulsions stabilized by cellulose acetoacetate (CAA). CAA is the key component in the system, acting as the emulsifier and the polymerization mediator simultaneously. The formed zwitterionic poly(sulfobetaine methacrylate) (PSBMA) hydrogel network provides emulsion hydrogels with good hydration capacity and potential anti-fouling performance. The thyme oil-loaded zwitterionic emulsion hydrogels exhibit interconnected, uniform, and adjustable porous structures with tunable mechanical properties, antifouling performance, good biocompatibility, and excellent antibacterial activity against S. aureus and E. coli. These results all demonstrate that the ternary enzyme-mediated polymerization of zwitterionic monomers in the continuous phase of O/W emulsion templates is a facile and efficient strategy to encapsulate hydrophobic bioactive ingredients.

Injectable and self-healing hydrogel as a stem cells carrier for treatment of diabetic erectile dysfunction.

Diabetic erectile dysfunction has witnessed extensive preclinical and clinical explorations of intracavernous injection of stem cells therapy. However, intracavernous injection of stem cells for diabetic erectile dysfunction is challenged by rapid diffusion from cavernous sinus. Here, we found that a benzaldehyde terminated poly (ethylene glycol)/glycol chitosan (CHO-PEG/GCS) hydrogel with injectability and self-healability served as a stem cell carrier to prolong cell retention in corpus cavernosum. It was able to gelate under physiological condition and encapsulate adipose stem cells (ASCs) without reducing proliferation after injection. Encapsulated labelled ASCs presented higher fluorescence than non-encapsulated ones in the region of penis at 14 days after intracavernous injection in male rats. CHO-PEG/GCS hydrogel enhanced ASCs to ameliorate diabetes-induced fibrosis and apoptosis of CD31-positive endothelial cells, α-SMA-positive smooth muscle and NeuN-positive neural fibers 12 weeks post-operation. It also synergized with ASCs to elevate cGMP level and promote erectile function. CHO-PEG/GCS hydrogel serves as a promising stem cell carrier in conditions requiring injection and in situ gelation to prolong cell retention.

The effect of the degree of substitution on the solubility of cellulose acetoacetates in water: A molecular dynamics simulation and density functional theory study.

The effect of the degree of substitution (DS) on the aqueous solubility of cellulose acetoacetates (CAA) was investigated by molecular dynamics simulations and density functional theory calculations. Using average non-covalent interaction and the electrostatic potential analyses done on cellobiose as the model, it was showed both polar and non-polar areas of the system increased as the more hydroxyls were replaced by acetoacetate groups. Analyses of the solvation free energies of a celludecose (glucan containing 10 monosaccharide sugar units) at constant pressure and temperature showed the polar solvation free energies and the number of decose-water hydrogen bonds increased as DS was varied from 0.3 to 0.8, which contributes to higher solubility in water. When the DS of CAA increased from 0.8 to 1.5, it became insoluble again because the plateaued increase in solvation free energy could no longer compensate for the decreasing CAA-water hydrogen bonding interactions. The growing van der Waals interactions among CAA molecules as the molecule grows bigger with each attached AA group also contributes to the decreasing water solubility.

Cellulosic sponges with pH responsive wettability for efficient oil-water separation.

To obtain efficient oil-water separation materials with responsiveness, cellulosic porous materials with switchable wettability in response to pH changes were developed by reacting cellulose acetoacetate sponges with alkylamines of varying carbon chain length via dynamic covalent enamine bonds. The resulting sponges reversibly changed between being superhydrophilic (θwater = 0°) and highly hydrophobic (maximal θwater = 146°) under suitable pH conditions while maintained the favorable porous structures. Notably, the functionalized sponges exhibited high and selective oil absorption capacity (40-80 g/g) and satisfying desorption ability of 80%, and could efficiently separate oil-water mixtures and emulsions with extremely high efficiency (> 99%) in a controllable manner. With the three-dimensional micro/nano porous structure, switchable wettability and intrinsic environmentally friendliness, the pH responsive cellulosic sponges developed here hold great potential in controllable oil-water separation and oily wastewater purification.

Antibacterial thyme oil-loaded organo-hydrogels utilizing cellulose acetoacetate as reactive polymer emulsifier.

Organo-hydrogels are widely used in various fields, due to functional organic ingredients immobilized by the gel network or stored and protected by the gels. Herein, cellulose acetoacetate (CAA) served as reactive natural polymer emulsifier to stabilize thyme oil-in-water (O/W) emulsions. Hydroxypropyl chitosan (HPCS) was added to the continuous phase in emulsions to achieve the organo-hydrogel via the enamine bonds under mild conditions. The thyme@CAA emulsion with different loadings of the inner phase (up to 50%) displayed uniform droplets distribution (3-5 µm) and favorable stability. The organo-hydrogel was systematically analyzed by Fourier transform infrared spectroscopy, optical microscope, rheology analyses. The emulsion droplets evenly dispersed in the three-dimensional network. The modulus of organo-hydrogels depended on the viscosity of precursor emulsions and the crosslinking density. The resulting organo-hydrogel displayed favorable antibacterial activity against E. coli and S. aureus. CAA, as the reactive emulsifier and crosslinking agent, was a promising alternative candidate to fabricate a series of organo-hydrogel.

Durable and Effective Antibacterial Cotton Fabric Collaborated with Polypropylene Tissue Mesh for Abdominal Wall Defect Repair.

A feasible, efficient antibacterial and anti-infective mesh for clinical abdominal wall defect repair is significant, but challenging due to the complexity of the postoperative wound environment. Herein, a simple strategy was provided to construct woven cotton fabric modified with gentamicin (Gem) via the enamine bonds. The obtained cotton fabric possessed favorable antibacterial properties against E. coli and S. aureus with the bactericidal rate of over 99.99% and could be combined with a commercial polypropylene (PP) mesh to serve as a two-layer composite mesh for abdominal wall defect repair. The antibacterial cotton layer was systematically characterized by FTIR, XPS, SEM, EDS, and mechanical measurements. The C2C12 cells and human fibroblasts were employed to assess the cytocompatibility of the composite mesh in vitro. Furthermore, the rat abdominal wall defect model was used to evaluate the efficacy of antibacterial and anti-infection properties. It was demonstrated that the two-layer composite mesh possessed favorable biocompatibility and satisfactory anti-infection properties involved in abdominal wall defect repair. Therefore, this synergetic two-layer composite mesh would out-perform surgical PP meshes in preventing infectious complications.

Durable antibacterial and hydrophobic cotton fabrics utilizing enamine bonds.

Herein, the acetoacetyl group was directly anchored on the surface of cotton fabric (Cotton-acac) via heterogeneous transesterification. This surface modification strategy was systematically characterized by Fourier transform infrared spectroscopy, solid-state 13C nuclear magnetic resonance spectroscopy, X-ray diffraction, and thermogravimetric analysis, which confirmed it was a mild and efficient process. Besides, Cotton-acac was used as the versatile intermediate post-modified with gentamicin (Gen) and octadecyl amine (ODA) molecules to impart cotton fabric dual functions with hydrophobic and antibacterial properties. The resulting cotton fabric showed dual and outstanding hydrophobic and antibacterial performance against E. coli and S. aureus, with the bactericidal rates of over 99.99% and the water contact angle of 145°even after 10 cycles of standard washing. Therefore, the heterogeneous modification provided a benign and versatile method for regulating the interfacial properties of the cellulosic materials, with the possibility of post modification for various applications through the acetoacetyl chemistry.

Biginelli reaction on cellulose acetoacetate: a new approach for versatile cellulose derivatives.

The Biginelli multicomponent reaction has been used as an effective and model method to efficiently prepare a library of cellulose derivatives based on cellulose acetoacetate (CAA). Various cellulose derivatives containing 3, 4-dihydropyrimidin-2(1 H)-ones (DHPMs) with different functional groups (carboxyl, methoxyl, and nitro) are synthesized. The entire reaction process is followed using FT-IR, 1H NMR. The results demonstrate that more than 80% of the acetoacetyl groups are converted within four hours. Additionally, all the cellulose derivatives are confirmed to have favorable thermostability and good solubility in selected solvents. Furthermore, polymers (in this case, poly (ethylene glycol) monomethyl ether (mPEG)) can also be anchored to the cellulose backbone via this facile modular approach. Therefore, the Biginelli multicomponent reaction offers a straightforward method for diverse and large-scale cellulose derivatization. These results are expected to prompt broader study of this multicomponent reaction in interdisciplinary fields.

A light-weight and high-efficacy antibacterial nanocellulose-based sponge via covalent immobilization of gentamicin.

Covalent grafting of gentamicin to nanocellulose-based sponge was realized for the first time. The named sponge was prepared by initially multi-crosslinking among cellulose nanofibers (CNF), cellulose acetoacetate (CAA) and 3-aminopropyl(triethoxy)silane (APTES) followed by surface modification with gentamicin via the formation of enamine bond. The structure and mechanical performances of the obtained gentamicin-functionalized CNF sponge were characterized with FT-IR, XPS, EDX, SEM, Nitrogen adsorption-desorption measurement, and compressive test. Its antibacterial activity against E. coli and S. aureus was evaluated using disc diffusion and colony forming units (CFU) count methods. The results showed that gentamicin was successfully grafted on the surface of CNF sponges without significant change in morphology and slight improvement in mechanical performance. The superior lightness of the sponge (0.0174 g cm-3) was demonstrated by showing the sponge could be supported by a flower branch without crushing it. Gentamicin-functionalized CNF sponges showed excellent antibacterial performance against E. coli and S. aureus, with bactericidal rates of over 99.9%.

Precipitated silica agglomerates reinforced with cellulose nanofibrils as adsorbents for heavy metals.

Silicon-containing compounds such as silica are effective heavy metal sorbents which can be employed in many applications. This is attributed to the porous nature of hydrothermally-stable silica, endowing such materials with high surface area and rich surface chemistry, all responsible for improving adsorption and desorption performance. However, to this day, the wide application of silica is limited by its skeletal brittleness and high production cost coupled with a risky traditional supercritical drying method. To solve the named problems, herein, precipitated silica agglomerates (referred to as PSA) was crosslinked with TEMPO-oxidized cellulose nanofibrils (TO-CNF) as a reinforcement in the presence of 3-aminopropyltriethoxysilane (APTES), via a facile dual metal synthesis approach, is reported. The resultant new silica-based sponges (TO-CNF PSA) showed desirable properties of flexibility, porosity and multifaceted sorption of various heavy metals with re-usability. The experimental results showed maximum adsorption capacities of 157.7, 33.22, 140.3 and 130.5 mg g-1 for Pb(ii), Hg(ii), Cr(iii) and Cd(ii) ions, respectively. Such a facile approach to modify silica materials by attaching active groups together with reinforcement can provide improved and reliable silica-based materials which can be applied in water treatment, gas purification, thermal insulation etc.

Facile fabrication of redox/pH dual stimuli responsive cellulose hydrogel.

A cellulose-based multi-responsive hydrogel was prepared by the facile incorporation of enamine and disulfide bonds in the same system at physiological pH. The cellulose hydrogel was obtained by simply mixing aqueous solutions of cellulose acetoacetate (CAA) and cystamine dihydrochloride (CYS) at room temperature. The internal morphology, structure, and mechanical properties of the cellulose hydrogel were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and Raman spectroscopies, nuclear magnetic resonance (NMR), and water retention, porosity, and rheology measurements. The cellulose hydrogel showed reversible sol-gel transitions in response to both pH and redox triggers. In addition, it displayed good stability under physiological conditions. Gels loaded with small molecules showed variable release properties in response to pH or redox stimuli. The preparation protocol presented here could be used to fabricate other multi-responsive polysaccharide hydrogels.

Facile synthesis of cellulose derivatives based on cellulose acetoacetate.

In the present work, cellulose acetoacetates (CAA) was used as a precursor for preparing diversely functionalized cellulose derivatives. Four amino-bearing compounds, namely hexylamine (HA), l-glutamic acid (Glu), cysteine (Cys), and tyramine (TA) were reacted with acetoacetyl groups providing alkyl-, carboxyl-, thiol-, or phenolic functionalized cellulose. The reaction was conducted under mild conditions without catalysts and UV light. The products were characterized with FT-IR, NMR and solubility measurement. 1H NMR measurement demonstrated the conversion of acetoacetyl groups were ideal, and all the cellulose derivatives demonstrated good solubility in certain solvent. Besides, CAA held a good stability under room temperature. This approach offers broad possibilities for developing new cellulose based materials. Moreover, this protocol can also be applied to fabricate other polysaccharide derivatives.