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DMTMM-mediated amidation of sodium alginate is one of the methods used for the chemical modification of alginate with amines. However, there is a limited understanding of how the reaction conditions, particularly the pH value, influence the conjugation efficiency (CE) and the resulting degree of substitution (DS). In this study, we investigated the effect of the pH during the reaction, focusing on both neutral and weakly basic conditions, using water and buffer as solvents. Two model amines with high p K a H values were selected, furfurylamine (FFA, p K a H = 9.12) and 4-(2-aminoethyl)morpholine (AEM, p K a H = 9.93). Sodium alginate with a high mannuronate content (60 mol%) and molar mass of 168 kg·mol−1 was used for amidation. Our results show that both FFA and AEM effectively conjugate to sodium alginate under the selected reaction conditions. We found that pH significantly affects both CE and DS, which varied between 2 % to 40 % and 3 % to 53 %, respectively, depending on the specific reaction conditions. Optimal conditions were observed at neutral pH in water, whereas weak basic pH led to lower CE. Our findings thus offer a recommendation for optimizing the DMTMM-mediated amidation of sodium alginate, emphasizing the importance of pH values during the reaction. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, an alginate/PEG hydrogel was developed via a thiol-Michael addition reaction between oxidized quinone of catechols on dopamine-grafted sodium alginate (SA-DA) and sulfhydryl groups of 4-arm polyethylene glycol tetra-thiol (4-arm PEG-SH) under mildly basic conditions. Through the formation of thiol-terminated catechol groups, the accompanying oxidized catechols are reduced, significantly strengthening the internal network structure of the hydrogel and improving tissue adhesion. Meanwhile, the hydrogels have excellent self-healing properties due to the dynamic non-covalent bonds between the groups. Adjustment of hydrogel properties by varying the mass ratio of two hydrogel precursors. Due to the high content of thiol-terminated catechol groups, the Gel 3 exhibited good tissue adhesion, rapid self-healing ability, and other multifunctions beneficial to wound healing, including killing of E. coli and S. aureus , rapid hemostasis and promoting migration of L929 cells. The full-thickness skin wound model shows that the hydrogel dressing significantly accelerated wound contraction, with increased granulation tissue thickness, collagen disposition, and enhanced vascularization, thus promoting wound healing. Therefore, the thiol-Michael addition reaction is an effective method for creating multifunctional hydrogels, and the injectable self-healing alginate/PEG hydrogels prepared in this way could be used in the biomedical area as wound healing dressing materials. [Display omitted] [ABSTRACT FROM AUTHOR]

In response to the pressing environmental challenge posed by petroleum-derived plastics, the development of green plastics derived from all-biomass nanocomposites offers promising solutions. However, conventional nanocomposites often prioritize enhanced stiffness at the expense of flexibility. We introduce sodium alginate (SA)/chitosan nanowhisker (CSW) nanocomposites, derived entirely from marine-sourced all-biomass, to create ultra-strong and flexible green plastics. Through the synergistic interaction between SA and CSW, these nanocomposites demonstrate simultaneous stiffening and toughening, overcoming the traditional trade-off. Two key mechanisms contribute: geometric reinforcement from the needle-like structure of CSW and electrostatic reinforcement at the interface between oppositely charged CSW and SA. Compared to control SA, the SA/CSW nanocomposites exhibit remarkable enhancements in tensile modulus, strength, and stretchability, by 49%, 85%, and 55%, respectively (7.6 GPa, 223.3 MPa, 14.7%). Cellulose nanocrystals, serving as a control, only stiffen the nanocomposites, adhering to the typical trade-off. Biodegradability in compost can be tailored based on the type of nanofillers. Due to the water resistance of CSW, SA/CSW nanocomposites are proven effective for the controlled release of urea fertilizer in agricultural applications. With recyclability and superior mechanical properties, these marine-sourced green plastics offer a sustainable alternative to conventional plastics, promising significant impact in the eco-plastic industry. [Display omitted] [ABSTRACT FROM AUTHOR]

Photothermal therapy has gained great attention as an alternative candidate for radiation therapy or chemotherapy for cancers. However, photothermal agents for photothermal therapy are generally in the form of nanoparticles that are too small to remain in the target tissue, and therefore, the agents are rather quickly removed from the targeted site. Furthermore, conventional photothermal agents are generally expensive or complicated to synthesize. As an approach to these issues, here we present new hydrogels with oxidized alginate ionically crosslinked with Ca2+, bearing polyaniline:poly(sodium 4-styrenesulfonate) (PANI:PSS) nanoparticles in the polymer network. The presented oxidized alginate PANI:PSS hydrogels exhibited excellent injectability as well as a gradual degradation rate from several days to several months depending on the oxidation degree of alginate chains. The presented oxidized alginate PANI:PSS hydrogels showed an excellent photothermal effect even under a neutral pH environment by showing temperature increased to 53 °C in 5 min upon NIR irradiation, which provide strong potential as a candidate for photothermal agent in photothermal therapy. [Display omitted] [ABSTRACT FROM AUTHOR]

The rising prevalence of bone injuries has increased the demand for minimally invasive treatments. Microbead hydrogels, renowned for cell encapsulation, provide a versatile substrate for bone tissue regeneration. They deliver bioactive agents, support cell growth, and promote osteogenesis, aiding bone repair and regeneration. In this study, we synthesized superparamagnetic iron oxide nanoparticles (Sp) coated with a calcium phosphate layer (m-Sp), achieving a distinctive flower-like micro-cluster morphology. Subsequently, sodium alginate (SA) microbead hydrogels containing m-Sp (McSa@m-Sp) were fabricated using a dropping gelation strategy. McSa@m-Sp is magnetically targetable, enhance cross-linking, control degradation rates, and provide strong antibacterial activity. Encapsulation studies with MC3T3-E1 cells revealed enhanced viability and proliferation. These studies also indicated significantly elevated alkaline phosphatase (ALP) activity and mineralization in MC3T3-E1 cells, as confirmed by Alizarin Red S (ARS) and Von Kossa staining, along with increased collagen production within the McSa@m-Sp microbead hydrogels. Immunocytochemistry (ICC) and gene expression studies supported the osteoinductive potential of McSa@m-Sp, showing increased expression of osteogenic markers including RUNX-2, collagen-I, osteopontin, and osteocalcin. Thus, McSa@m-Sp microbead hydrogels offer a promising strategy for multifunctional scaffolds in bone tissue engineering. [ABSTRACT FROM AUTHOR]

Frequent occurrence of wound infection caused by multiple-resistant bacteria (MRB) has posed a serious challenge to the current healthcare system relying on antibiotics. The development of novel antimicrobial materials with high safety and efficacy to heal wound infection is of great importance in combating this crisis. Herein, we prepared a promising antibacterial hydrogel by cross-linking ferrous ions (Fe2+) with the deprotonated carboxyl anion in sodium alginate (Na-ALG) to cure wound infections caused by methicillin-resistant Staphylococcus aureus (MRSA). Interestingly, ferrous-modified Na-ALG (Fe-ALG) hydrogel demonstrated better properties compared to the traditional Na-ALG-based hydrogels, including injectability, self-healing, appropriate fluidity, high-water retention, potent MRSA-killing efficacy, and excellent biocompatibility. Importantly, the addition of Fe2+ enhances the antibacterial efficacy of the Na-ALG hydrogel, enabling it to effectively eliminate MRSA and accelerate the healing of antibiotic-resistant bacterial-infected wounds in a remarkably short period (10 days). This modification not only facilitates wound closure and fur generation, but also mitigates systemic inflammation, thereby effectively impeding the spread of MRSA to the lungs. Taken together, Fe-ALG hydrogel is a promising therapeutic material for treating wound infections by Staphylococcus aureus , especially by antibiotic-resistant strains like MRSA. [ABSTRACT FROM AUTHOR]

Nanocellulose hydrogels are promising to replace synthetic ones for direct ink writing (DIW)-based 3D printing biobased applications. However, less gelation strength and low solid content of the hydrogels limit the printability and subsequent fidelity of the dried object. Herein, a biobased, ternary DIW hydrogel ink is developed by one-pot gelation of cellulose nanofibrils (CNF), sodium alginate (SA), and Ca-montmorillonite (Ca-MMT) via in situ ionic crosslinking. The addition of Ca-MMT into CNF/SA formulation simultaneously increases the solid content and gelation strength of the hydrogel. The resultant hydrogels exhibit shape recovery after compression. The optimal CNF concentration in the hydrogel is 1.2 wt%, enabling the highest compressive mechanical performance of the scaffolds. A series of complex, customized shapes with different curvatures and three-dimensional structures (e.g., high-curvature letters, pyramids, human ears, etc.) can be printed with high fidelity before and after drying. This study opens an avenue on preparing nanocellulose-based DIW hydrogel inks using one-pot gelation of the components, which offers a solution to combine DIW-based 3D printing with biobased hydrogel inks, towards diverse biobased applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Cellulose has outstanding potential for application in energy storage batteries due to its high temperature resistance, high electrolyte affinity, renewability, and suppression of the shuttle effect, but single cellulose membranes still suffer from problems such as inhomogeneous pore distribution and unstable three-dimensional network structure. In this study, a green and sustainable regenerative cellulose (RC)/sodium alginate (SA) gel electrolyte membrane is developed by sol-gel process, the double crosslinked network scaffold centered on Zn2+ was constructed by the synergistic hydrogen-bonding and metal ion- coordination network, the stable and uniform pore structure was also formed. The obtained RC-SA gel electrolyte membrane exhibits outstanding performance, featuring a dual crosslinked network with abundant pore structure and numerous polar groups that effectively enhance Zn2+ transport, significantly improving battery cycling performance. The corresponding RC-SA gel electrolyte membrane demonstrates high ionic conductivity (6.30 mS·cm−1) and Zn2+ transference number (0.66), leading to excellent reversible capacity (159 mA·h·g−1) and self-discharge suppression capability (maintaining 99.2 % of capacity after a 24 h standstill) in Zn//V 2 O 5 full-cell. The coulombic efficiency and cycling stability of the Zn//Cu half-cell and Zn//Zn symmetric cell using RC-SA gel electrolyte membrane outperforms that of the glass fiber separator, highlighting its multifunctionality and potential applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Uncontrolled release of active agents in active packaging reduces antimicrobial efficacy, hindering the effective protection of perishable products from microbial infection. Herein, a novel defective engineering was proposed to design defective and hollow ZIF-8 structures grown on TEMPO oxidized cellulose nanofibrils (TOCNFs) and use them as fast-reacting nanocarriers for loading and controlled release curcumin (Cur) in sodium alginate (SA) active packaging systems (CZT-Cur-SA). By employing stable chelation between tannic acid (TA) and ZIF-8 zinc ions, the connections between zinc ions and imidazole ligands were severed to form a loose and hollow structure, which facilitates the rapid reaction and release of active ingredients triggered by pH changes in the microenvironment. Kinetic tests showed CZT-Cur-SA films released 65.68 % of Cur at pH 6.0 within 24 h, compared to 28.26 % at pH 7.0. These films demonstrated exhibited excellent mechanical properties, antioxidation capacity (82.59 %), reinforced moisture (0.51 × 10−10 g m−1 s−1 Pa−1) and satisfied antimicrobial effects on E. coli (1.69 %) and S. aureus (0.88 %). The optimized CZT-Cur-SA film extended strawberry shelf life to at least 7 days under ambient conditions. Our findings introduce a promising approach to designing responsive, biodegradable active packaging for enhanced food safety. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) mediated g-C 3 N 4 (CN) is a promising visible-light-driven semiconductor in catalyzing peroxymonosulfate (PMS) for aqueous contaminants remediation. However, the poor dispersibility of powered catalyst and its challenging recyclability impede their broader application. Herein, we embedded Fe N bridge within the g-C 3 N 4 framework and immobilized g-C 3 N 4 gel beads (CA/FNCCN) through a 3D cross-linking process with sodium alginate. Alginate can serve as a stabilizing carrier, preserving the crystalline structure of FNCCN through the formation of H bonds between alginate and FNCCN. The resulting beads displayed significantly improved photo-electrochemical performance, along with greatly enhanced adsorption capacity and catalytic activity toward Sulfamethoxazole (SMX). The catalytic efficiency of CA/FNCCN was markedly increased as compared to non-immobilized FNCCN due to reduced photo-carrier recombination and accelerated electron transport. CA/FNCCN-1 can degrade 99.18 % of SMX within 40 mins, with noteworthy reduced Fe leaching. The primary active species in the system were 1O 2 and h+, and the direct electron transfer between PMS and SMX mediated by alginate also contributed to the removal of SMX. Additionally, the degradation pathway of SMX was elucidated through LC-MS and DFT calculations. Simultaneously, FNCCN integrated alginate hydrogel can remain active without decay after 10 cycles. [ABSTRACT FROM AUTHOR]

Natural polysaccharides with excellent biocompatibility are considered ideal materials for repairing diabetic foot ulcer. However, diabetic foot ulcer is often accompanied by decreased muscle function, even resulting in muscle atrophy. During wound repair, monitoring muscle function at the wound site in real time can identify the decreased muscle strength timely, which is crucial for precise wound rehabilitation. Nevertheless, the majority of hydrogels are primarily utilized for wound healing and lack the capability for electromyography monitoring. Here, we designed a multinetwork hydrogel composed of astragalus polysaccharide, chitosan, and sodium alginate and internally embedded conductive PPy-PDA-MnO 2 nanoparticles (P-NPs) loaded with resveratrol (Res) for wound repair and muscle function assessment. The intrinsic hypoglycemic and anti-inflammatory properties of astragalus polysaccharides, combined with the antioxidative and proangiogenic functions of Res, synergistically facilitate wound healing. The multinetwork structure affords the hydrogel excellent mechanical properties. Furthermore, the addition of conductive NPs not only improves the mechanical performance of the hydrogel but also confers electrical conductivity. The conductive hydrogel acts as an epidermal electrode which can be utilized for monitoring of electromyography signals. This novel approach for treating diabetic wounds ultimately achieves improved wound repair and muscle function assessment, carrying out a monitoring-guided safe and accurate wound repair. [Display omitted] [ABSTRACT FROM AUTHOR]

Starch-based hydrogels, characterized by their three-dimensional network structures, are increasingly explored for their biodegradability, low cost, and abundance of modifiable hydroxyl groups. However, a comprehensive understanding of the mechanisms behind the formation and property modulation of these hydrogels has not been systematically described. Drawing from literature of the past decade, this review provides insights into designing multifunctional starch-based hydrogels through various gelation mechanism, crosslinking strategies, and second-network structure. This comprehensive review aims to establish a theoretical framework for controlling the properties of starch-based hydrogels. A crucial aspect of starch hydrogel formation is the dense, cellular structure produced by swollen particles; when these particles fully disrupt, amylose recrystallization creates "junction zones" essential for network stability. In double-network hydrogels, materials such as polyvinyl alcohol (PVA), sodium alginate (SA), and polyacrylamide (PAM) form an effective secondary network, enhancing the mechanical strength and versatility of the hydrogel. The functionalization of starch-based hydrogels is primarily achieved through the introduction of functional group, secondary networks, and ionic liquids. [Display omitted] [ABSTRACT FROM AUTHOR]

To develop a stable hydrogel drug carrier with excellent biocompatibility, biodegradability and low toxicity, a green biomass-based hydrogel was prepared as a methylene blue (MB) drug carrier model using cellulose and sodium alginate (SA) polysaccharide. The addition of nanocellulose (CNF) and hydrothermally prepared carbon microspheres to the hydrogel network formed by SA undergoing chelation with Ca2+ enhanced the multifaceted properties of the drug carrier. Additionally, the prepared SA-CNFgel CS0.1 could withstand a pressure of 8.64 N and showed good compressive and elastic properties. Meanwhile, its encapsulation rate and drug loading capacity could reach 95.5 % and 19.36 mg/g, respectively. The drug release rate reached 43.4 % at 100 h in PBS solution simulating the pH value of the gastric environment, indicating good pH-responsiveness and long-lasting release ability during the drug-carrying release process. The release mechanism of the drug carrier to MB was investigated by different release kinetic models, which was in accordance with the first-order kinetic model. SA-CNFgel CS0.1 at high concentration also did not affect the number of pancreatic cell survival and showed a high degree of biocompatibility. In addition to that, SA-CNFgel CS0.1 can reach 100 % degradation rate in 18 days, which has no burden on the environment during use. The present study offers a novel approach to the synthesis of a biomass drug-carrying model with enhanced performance. Furthermore, this drug carrier provides a promising foundation for the development of oral MB as a potential treatment for gastrointestinal diseases and other chronic condition. [Display omitted] [ABSTRACT FROM AUTHOR]

Hierarchical porous composite microgels (SPZ microgels) were synthesized using microfluidic technology, composed of sodium alginate (SA), polyvinyl alcohol (PVA), and zeolitic imidazolate framework-8 (ZIF-8). The incorporation of ZIF-8 nanoparticles led to the formation of significant porous structures within the microgels, greatly enhancing their dye adsorption performance. Additionally, the diffusion of acetone during the crosslinking reaction resulted in sodium chloride crystal formation, creating a hierarchical porous structure with larger internal porous channels and smaller external channels. These SPZ microgels exhibited remarkable adsorption capabilities for both anionic and cationic dyes. The SPZ microgels showed exceptional adsorption capacities of 180 mg/g for methyl orange (MO) and 210 mg/g for methylene blue (MeB), far exceeding the performance of control microgels without the hierarchical porous structure (20 mg/g for MO and 150 mg/g for MeB). The hierarchical porous structure provided a larger surface area and facilitated improved diffusion and faster adsorption kinetics, contributing to the superior adsorption performance of the SPZ microgels. Kinetic studies revealed that MeB adsorption followed pseudo-second-order kinetics, while MO adsorption followed pseudo-first-order kinetics. Isotherm studies established that the Langmuir model accurately described MeB adsorption, indicating monolayer adsorption, while the Freundlich model effectively characterized MO adsorption, indicating multilayer interactions. [Display omitted] [ABSTRACT FROM AUTHOR]

Poor osseointegration markedly compromises the longevity of prostheses. To enhance the stability of titanium implants, surface functionalization is a proven strategy to promote prosthesis-bone integration. This study developed a hydrogel coating capable of simultaneous osteoangiogenesis and vascularization by incorporating deferoxamine (DFO) into a sodium alginate mineralized collagen composite hydrogel. The physicochemical properties of this hydrogel were thoroughly analyzed. In vivo and in vitro experiments confirmed the hydrogel scaffold's osteogenic and angiogenic capabilities. Results indicated that sodium alginate notably enhanced the mechanical characteristics of the mineralized collagen, allowing it to fully infiltrate the interstices of the 3D-printed titanium scaffold. Furthermore, as the hydrogel degraded, collagen, calcium ion, phosphate ion, and DFO were gradually released around the scaffolds, altering the local osteogenic microenvironment and strongly inducing new bone tissue growth. These findings offer novel perspectives for the creation and utilization of functionalized bone implant materials. [ABSTRACT FROM AUTHOR]

Calcium alginate is one of the most widely employed matrices in regenerative medicine. A downside is its heterogeneity, due to the poorly controllable character of the gelation of sodium alginate (NaAlg), i.e. the commonly used alginate salt, with calcium. Here, we have used magnesium alginate (MgAlg) as an alternative precursor of calcium alginate. MgAlg coils, more compact and thus less entangled than those of NaAlg, allow for an easier diffusion of calcium ions, whereas Mg is exchanged with calcium more slowly than Na; this allows for the formation of a material (Ca(Mg)Alg) with a more reversible creep behaviour than Ca(Na)Alg, due to a more homogeneous – albeit lower - density of elastically active cross-links. We also show that Ca(Mg)Alg supports better than Ca(Na)Alg the network development and function of embedded (rat cortical) neurons: they show greater neurite extension and branching at 7 and 21 days (Tubb3 and Map2 immunofluorescence) and better neuronal network functional maturation / more robust and longer-lasting activity, probed by calcium imaging and microelectrode array electrophysiology. Overall, our results unveil the potential of MgAlg as bioactive biomaterial for enabling the formation of functional neuron-based tissue analogues. [Display omitted] [ABSTRACT FROM AUTHOR]

Facing the severe problem of microplastic pollution, there is an urgent need to develop biodegradable fibers to replace the petrochemical fibers. Sodium alginate, a biomass polysaccharide, has gained widespread attentions recently for the fiber manufacture. However, the limited mechanical strength of alginate fibers restricts their usages as load-bearing fabrics and reinforcement fibers. Here, we develop a novel strategy to prepare alginate multifilaments using pre-crosslinked sodium alginate solutions. The increase in the pre-crosslinking ratio effectively hinders the disentanglement of sodium alginate chains at high stretches, causing an increase in the shear viscosity of the solution ascertained from the capillarity-driven thinning process from 4.5 Pa·s to 9.9 Pa·s and facilitating the high alignment and orientation of sodium alginate chains. The resultant fibers possess a breaking strength of 474 MPa, elongation at break of 16 %, Young's modulus of 14.4 GPa, and toughness of 51.8 MJ/m3, exceeding most biomass fibers without reinforcement additives. The high orientation degree of 0.865 and high spinnability of alginate multifilaments enable their applications in multi-channel encryption fabrics that exhibit distinct information under various optical conditions. This rheological regulation of spinning solutions provides a facile yet effective strategy to enhance the mechanical performance and broaden application scenarios of alginate fibers. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, new types of hybrid double-network (DN) hydrogels composed of polyvinyl alcohol (PVA), chitosan (CH), and sodium alginate (SA) are introduced, with the hypothesis that this combination and incorporating multi-walled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) will enhance osteogenetic differentiation and the structural and mechanical properties of scaffolds for bone tissue engineering applications. Initially, the impact of varying mass ratios of the PVA/CH/SA mixture on mechanical properties, swelling ratio, and degradability was examined. Based on this investigation, a mass ratio of 4:6:6 was determined to be optimal. At this ratio, the hydrogel demonstrated a Young's modulus of 47.5 ± 5 kPa, a swelling ratio of 680 ± 6 % after 3 h, and a degradation rate of 46.5 ± 5 % after 40 days. In the next phase, following the determination of the optimal mass ratio, CNTs and GNPs were incorporated into the 4:6:6 composite resulting in a significant enhancement in the electrical conductivity and stiffness of the scaffolds. The introduction of CNTs led to a notable increase of 36 % in the viability of MG63 osteoblast cells. Additionally, the inhibition zone test revealed that GNPs and CNTs increased the diameter of the inhibition zone by 49.6 % and 52.6 %, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

Polysaccharide-based hydrogels are promising for many biomedical applications including drug delivery, wound healing, and tissue engineering. We illustrate herein self-healing, injectable, fast-gelling hydrogels prepared from multi-reducing end polysaccharides, recently introduced by the Edgar group. Simple condensation of reducing ends from multi-reducing end alginate (M-Alg) with amines from polyethylene imine (PEI) in water affords a dynamic, hydrophilic polysaccharide network. Trace amounts of acetic acid can accelerate the gelation time from hours to seconds. The fast-gelation behavior is driven by rapid Schiff base formation and strong ionic interactions induced by acetic acid. A cantilever rheometer enables real-time monitoring of changes in viscoelastic properties during hydrogel formation. The reversible nature of these crosslinks (imine bonds, ionic interactions) provides a hydrogel with low toxicity in cell studies as well as self-healing and injectable properties. Therefore, the self-healing, injectable, and fast-gelling M-Alg/PEI hydrogel holds substantial promise for biomedical, agricultural, controlled release, and other applications. [Display omitted] [ABSTRACT FROM AUTHOR]

To improve the features of alginate-based hydrogels in physiological conditions, Ca2+-crosslinked semi-interpenetrated hydrogels formed by poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid and alginate (PEDOT/Alg) were subjected to a treatment with glyoxal to form a dual ionic/covalent network. The covalent network density was systematically varied by considering different glyoxalization times (t G). The content of Ca2+ was significantly higher for the untreated hydrogel than for the glyoxalized ones, while the properties of the hydrogels were found to largely depend on t G. The porosity and swelling capacity decreased with increasing t G , while the stiffness and electrical conductance retention capacity increased with t G. The potentiodynamic response of the hydrogels notably depended on the amount of conformational restraints introduced by the glyoxal, which is a very short crosslinker. Thus, the re-accommodation of the polymer chains during the cyclic potential scans became more difficult with increasing number of covalent crosslinks. This information was used to improve the performance of untreated PEDOT/Alg as electrochemical sensor of hydrogen peroxide by simply applying a t G of 5 min. Overall, the control of the properties of glyoxalized hydrogels through t G is very advantageous and can be used as an on-demand strategy to improve the performance of such materials depending on the application. [Display omitted] [ABSTRACT FROM AUTHOR]

Sodium alginate (SA) is a marine polysaccharide biomass material that is environmentally friendly and exhibits color-changing properties under certain conditions. In this study, we have discovered sodium alginate solution to be chromogenic under four conditions, namely alkali-chromogenic, thermo-chromogenic, force-chromogenic and photo-chromogenic. Under simple strong alkaline conditions, sodium alginate forms clusters of blue light-absorbing chromogenic aggregates, which exhibit a bright yellow color at a certain size. Under different temperature conditions, SA shows varying shades of yellow, and the color tends to stabilize after 48 h of resting. The aggregates can be dispersed by stirring, which changes SA from yellow to colorless. The yellow color can then be recovered after resting. Additionally, exposure to sunlight can cause the yellow SA to fade, but the color can be restored by reheating. Therefore, the force-chromogenic and photo-chromogenic properties are reversible. This makes it a promising material for use in color-developing and indicating materials. It is expected to become a sodium alginate cluster pigment with broad application prospects in the future. [Display omitted] [ABSTRACT FROM AUTHOR]

Although conductive hydrogels have been widely developed currently, their low sensitivity and poor stability severely limited their practical application in flexible wearable devices. Herein, a green "stencil" anchoring strategy was proposed in this study to engineer an ultra-stable and supersensitive hydrogel by virtue of polydopamine decorating sodium alginate molecular chains as "stencil" to anchor polyaniline as conductive component. The dispersion of polyaniline was significantly improved by the sodium alginate "stencil" in the conductive hydrogel. The developed conductive hydrogel exhibited outstanding properties that outperformed most conventional ones, including extraordinary sensitivity with a gauge factor of 38.2 and excellent stability with negligible shifting upon long-term cyclic stretching. Moreover, the conductive hydrogel displayed great self-adhesion and reliable self-healing performance endowed by its abundant catechol groups, hydrogen bondings and π-π stackings, respectively. Furthermore, the prepared hydrogel was also assembled as flexible strain and self-powered sensors, which displayed excellent sensing performance, indicating great potential in human-machine interactions, information transmission and road transportation. [Display omitted] [ABSTRACT FROM AUTHOR]

Biological processes, such as bone defects healing are precisely controlled in both time and space. This spatiotemporal characteristic inspires novel therapeutic strategies. The sustained-release systems including hydrogels are commonly utilized in the treatment of bone defect; however, traditional hydrogels often release drugs at a consistent rate, lacking temporal precision. In this study, a hybrid hydrogel has been developed by using sodium alginate, sucrose acetate isobutyrate, and electrospray microspheres as the base materials, and designed with ultrasound response, and on-demand release properties. Sucrose acetate isobutyrate was added to the hybrid hydrogel to prevent burst release. The network structure of the hybrid hydrogel is formed by the interconnection of Ca2+ with the carboxyl groups of sodium alginate. Notably, when the hybrid hydrogel is exposed to ultrasound, the ionic bond can be broken to promote drug release; when ultrasound is turned off, the release returned to a low-release state. This hybrid hydrogel reveals not only injectability, degradability, and good mechanical properties but also shows multiple responses to ultrasound. And it has good biocompatibility and promotes osteogenesis efficiency in vivo. Thus, this hybrid hydrogel provides a promising therapeutic strategy for the treatment of bone defects. [Display omitted] [ABSTRACT FROM AUTHOR]

Developing large-scale hydrogels with high tensile strength and robust mechanical properties is an intricate challenge of great industrial significance. In this study, we demonstrate an efficient method for producing nanocomposite hydrogels with extraordinary mechanical properties. Our approach involves a two-step process: an initial stage of pre-cross-linking boron nitride (BN)-enriched pre-gel sodium alginate, followed by cross-linking with metal ions. In stark contrast to conventional sodium alginate hydrogels (SA), our newly formulated 'BS hydrogel' exhibited an impressive tensile strength exceeding 41 MPa and improved thermal resistance. Moreover, the reconstituted BS hydrogel exhibited tensile strengths ranging from 47 to 96 MPa and elastic moduli ranging from 199 to 1184 MPa, depending on the cross-linking metal ions. These findings indicate the multifaceted potential of the BS hydrogel, which is poised to revolutionize many applications and represents a significant step forward in hydrogel technology for industrial applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Injectable hydrogels have wide applications in clinical practice. However, the development of tough and bioadhesive ones based on biopolymers, along with biofriendly and robust crosslinking strategies, still represents a great challenge. Herein, we report an injectable hydrogel composed of maleimidyl alginate and pristine gelatin, for which the precursor solutions could self-crosslink via mild Michael-type addition without any catalyst or external energy upon mixing. This hydrogel is tough and bioadhesive, which can maintain intactness as well as adherence to the defect of porcine skin under fierce bending and twisting, warm water bath, and boiling water shower. Besides, it is biocompatible, bioactive and biodegradable, which could support the growth and remodeling of cells by affording an extracellular matrix-like environment. As a proof of application, we demonstrate that this hydrogel could significantly accelerate diabetic skin wound healing, thereby holding great potential in healthcare. [Display omitted] [ABSTRACT FROM AUTHOR]

Minimally invasive, efficient, and satisfactory treatment for irregular and lacunar bone defects is still a challenge. Alginate hydrogels serve as promising stem cell (SC) delivery systems for bone regeneration but are limited by low cellular viability, poor osteogenic differentiation, and insufficient mechanical support. Herein, we developed a BMSCs-laden mechanically reinforced bioactive sodium alginate composite hydrogel microspheres (BCHMs) system via a microfluidic method that possesses 1) a uniform size and good injectability to meet clinical bone defects with complex shapes, 2) high cellular viability maintenance and further osteogenic induction capacity, and 3) improved mechanical properties. As the main matrix, the sodium alginate hydrogel maintains the high viability of encapsulated BMSCs and efficient substance exchange. Enhanced mechanical properties and osteogenic differentiation of the BCHMs in vitro were observed with xonotlite (Ca 6 Si 6 O 17 (OH) 2 , CSH) nanowires incorporated. Furthermore, BCHMs with 12.5 % CSH were injected into rat femoral bone defects, and satisfactory in situ regeneration outcomes were observed. Overall, it is believed that BCHMs expand the application of polysaccharide science and provide a promising injectable bone substitute for minimally invasive bone repair. [ABSTRACT FROM AUTHOR]

Due to Cd(II) with highly toxic, persistent and bioaccumulative, the discharge of it into the environment brings serious pollution. Developing strategies that are efficient, low-cost, pollution-free and specific to removing Cd(II) from wastewater is therefore of great urgency and prime importance. A novel chitosan/sodium alginate ionic imprinting(IICA) hydrogels with specific adsorption capacity for Cd(II) was prepared through freeze-thaw and ion imprinting, and finally the colorimetric sensor (IICAS) was prepared via introducing Rhodamine B(RhB) and Victoria blue(VBB) by immersion to achieve visual detection of Cd(II). The IICA hydrogels with imprinted hole structure had higher adsorption capacity and better specific selectivity for Cd(II). As well as internal diffusion, coordination, ion exchange, and hydrogen bonding influenced the adsorption rate. Moreover, the IICAS exhibited good selective detection ability and linearity for Cd(II) with the fitted correlation coefficient (R2) = 0.98, limit of detection (LOD) = 35 nmol/L. Combined with the smartphone platform, portable and quantitative detection of Cd(II) can be achieved, Within the 0–100 mg/L range, R2 remained 0.94, and LOD was 75 nmol/L. This strategy of preparing a novel whole biomass IICAS integrating capture and visual detection provides a new insight into the construction of a promising candidate sensor for the removal and detection of Cd(II). [Display omitted] [ABSTRACT FROM AUTHOR]

Sodium alginate (SA) hybrid fibers have been robustly fabricated by electrospinning of aqueous mixtures containing as high as 60% SA in the presence of polyvinyl alcohol (PVA). Solution viscosities of SA, PVA and their mixtures showed fiber spinning to be strongly influenced by the balance between SA-PVA and PVA-PVA intermolecular polar interaction and SA-SA repulsion. Low viscosity SAl (50 mPas at 1%) enabled higher SA loadings without significantly increasing mixture viscosities, producing more cylindrical fibers. All aqueous mixtures containing 33.3-60% SAl (5.68-7.15% total SAl-PVA) had viscosities ranging from 530 to 3600 mPas and could be electrospun continuously for at least 48 h. The SA-PVA hybrid fibers had diameters ranging from ca. 140 to 350 nm and were rendered stable in water via simultaneous ionic-crosslinking SA and crystallization of PVA (5% CaCl2 in 75% EtOH for 30 min). This aqueous electrospinning and physical crosslinking approach is a green and highly efficient alternative to create alginate hybrid fibers that are biologically compatible and ingestible for potential biomedical, food and other applications.

Due to the expansion of industrial activities, the concentration of dyes in water has been increasing. The dire need to remove these pollutants from water has been heavily discussed. This study focuses on the reproducible and sustainable solution for wastewater treatment and dye annihilation challenges. Adsorption has been rated the most practical way of the several decolorization procedures due to its minimal initial investment, convenient utility, and high-performance caliber. Hydrogels, which are three-dimensional polymer networks, are notable because of their potential to regenerate, biodegrade, absorb bulky amounts of water, respond to stimuli, and have unique morphologies. Natural polysaccharide hydrogels are chosen over synthetic ones because they are robust, bioresorbable, non-toxic, and cheaply accessible. This study has covered six biopolymers, including chitosan, cellulose, pectin, sodium alginate, guar gum, and starch, consisting of their chemical architecture, origins, characteristics, and uses. The next part describes these polysaccharide-based hydrogels, including their manufacturing techniques, chemical alterations, and adsorption effectiveness. It is deeply evaluated how size and shape affect the adsorption rate, which has not been addressed in any prior research. To assist the readers in identifying areas for further research in this subject, limitations of these hydrogels and future views are provided in the conclusion. [Display omitted] • Different physiochemical interactions that result in the adsorption of pollutants. • Discussion and comparison of preparation strategies, chemical modifications, and adsorption outcomes. • The effect of modifiers and factors on the adsorption efficiency of hydrogels. • Critical study of the morphological aspects on hydrogel performance for dye removal. [ABSTRACT FROM AUTHOR]

Sodium alginate was associated to a ternary solvent composed of fructose, glycerol, and water in a 1:1:5 M ratio (FGW), classified as a natural Low Transition Temperature Mixture (LTTM), to generate various soft materials. The rheological properties of mixtures composed of sodium alginate and FGW were thoroughly analyzed and compared to their aqueous analogues. FGW-based solutions present a pronounced shear-thinning character combined to high viscosity, up to 8000 Pa.s. The overlap concentrations and intrinsic viscosities values evidence a good solvent character of FGW for alginate polymer chains. The increase of alginate concentration in FGW leads to materials with enhanced elasticity (up to 6000 Pa) and high energy of activation (55 kJ/mol). Interestingly, the addition of divalent calcium cations in FGW according to two optimized experimental protocols, allows for the generation of never described ionotropic gels in FGW under various shapes as bulk gels or beads of gels able to encapsulate extracted vegetal actives that are used in the cosmetic industry. Thus, FGW appears as a well-suited solvent of alginate to design a broad range of new biobased soft materials. [ABSTRACT FROM AUTHOR]

Biomacromolecules based injectable and self-healing hydrogels possessing high mechanical properties have widespread potential in biomedical field. However, dynamic features are usually inversely proportional to toughness. It is challenging to simultaneously endow these properties to the dynamic hydrogels. Here, we fabricated an injectable nanocomposite hydrogel (CS-NPs@OSA-l-Gtn) stimultaneously possessing excellent autonomous self-healing performance and high mechanical strength by doping chitosan nanoparticles (CS-NPs) into dynamic polymer networks of oxidized sodium alginate (OSA) and gelatin (Gtn) in the presence of borax. The synergistic effect of the multiple reversible interactions combining dynamic covalent bonds (i.e., imine bond and borate ester bond) and noncovalent interactions (i.e., electrostatic interaction and hydrogen bond) provide effective energy dissipation to endure high fatigue resistance and cyclic loading. The dynamic hydrogel exhibited excellent mechanical properties like maximum 2.43 MPa compressive strength, 493.91 % fracture strain, and 89.54 kJ/m3 toughness. Moreover, the integrated hydrogel after injection and self-healing could withstand 150 successive compressive cycles. Besides, the bovine serum albumin embedded in CS-NPs could be sustainably released from the nanocomposite hydrogel for 12 days. This study proposes a novel strategy to synthesize an injectable and self-healing hydrogel combined with excellent mechanical properties for designing high-strength natural carriers with sustained protein delivery. [Display omitted] [ABSTRACT FROM AUTHOR]

Hydrogel beads prepared from protein nanofibers are popular because of their safety, sleek appearance, and protection of biologically active substances. However, extreme external environmental variations, such as pH and temperature, can limit their practical application. To meet the application requirements of hydrogel beads in different environments, non-covalent mixtures of CaCl 2 cross-linked soybean protein nanofibers (SNF) and sodium alginate (SA) were used to prepare hydrogel beads. In the present study, the hardness (782.48 g) and elasticity of hydrogel beads formed at SNF/SA = 7:3 and CaCl 2 concentration of 0.1 mol/L were the maximum. Furthermore, the water content and pH swelling also reached a peak (98.68 %, 43.85 g/g) due to the best morphology and regular internal network structure. Meanwhile, the pH-responsive hydrogel beads with added anthocyanins were able to respond to the ambient pH under different temperatures and pH conditions and maintained color stability during 96 h of storage (ΔE < 5). In this experiment, a pH-responsive hydrogel bead based on soybean protein nanofiber (SNF) and sodium alginate (SA) was prepared by simple ionic crosslinking. It provides a theoretical and experimental basis for the future application of plant protein nanofibers as pH-responsive hydrogel materials. [ABSTRACT FROM AUTHOR]

In this paper, an eco-friendly versatile superabsorbent material was designed for soil improvement, and a synchronous chemical loading strategy was proposed. In this strategy, urea not only acted as fertilizer but also acted as a crosslinker to construct an alginate network. The microstructure, chemical structure, thermal stability and composition of the obtained SA/urea hydrogel were characterized in detail. Adsorption behavior and application performance in agriculture were evaluated. The results demonstrated that urea had two different conformations in the network. The SA/urea hydrogel had abundant pore structures with excellent water absorption performance. It could not only improve the water retention capacity of soil but also release nitrogen, phosphorus and potassium elements with degradation for as long as 9 weeks. Moreover, the hydrogel could promote plant growth, increase the nutritional composition of plants and inhibit the accumulation of harmful nitrate in plants. With advantages, including biodegradability, high water absorption, controllable degradation, excellent water retention, sustained NPK release and improved plant nutrition value, the SA/urea hydrogel has great potential for soil improvement in agriculture as an eco-friendly versatile water retention agent and can be expected to extend to more fields as a novel superabsorbent material. [ABSTRACT FROM AUTHOR]

Sodium alginate is one of the most abundant sustainable gum source for dietary fiber production. However, the preparation efficiencies of low viscosity soluble dietary fiber from sodium alginate remain low. Here, a novel alginate lyase gene (FsAly7) from Flammeovirga sp. was identified and high–level expressed in Pichia pastoris for low viscosity soluble dietary fiber production. The highest enzyme production of 3050 U mL−1 was achieved, which is by far the highest yield ever reported. FsAly7 was used for low viscosity soluble dietary fiber production from sodium alginate, and the highest degradation rate of 85.5 % was achieved under a high substrate content of 20 % (w / v). The molecular weight of obtained soluble dietary fiber converged to 10.75 kDa. FsAly7 catalyzed the cleavage of glycosidic bonds in alginate chains with formation of unsaturated non-reducing ends simultaneously in the degradation process, thus altered the chemical structures of hydrolysates. The soluble dietary fiber exhibited excellent properties, including low viscosity, high oil adsorption capacity activity (2.20 ± 0.03 g g−1) and high emulsifying activity (60.05 ± 2.96 mL/100 mL). This investigation may provide a novel alginate lyase catalyst as well as a solution for the efficient production of low viscosity soluble dietary fiber from sodium alginate. [Display omitted] [ABSTRACT FROM AUTHOR]

• Alginate grafted by P(NIPAM 90 -co-NtBAM 10) exhibiting thermo-induced gelation. • 3D network arisen from the hydrophobic association of the thermosensitive side chains. • Thermo-thickening effect due to the slowdown of the side chain exchange dynamics. • Evaluation of shear viscosity by applying frequency-temperature superposition. • Combination of shear- and thermo- responsiveness provided hydrogel injectability. Sodium alginate grafted by a thermo-responsive copolymer of N-isopropylacrylamide, enriched with the hydrophobic N- tert -butylacrylamide monomer, (P(NIPAM-co-NtBAM)-NH 2) was synthesized and its thermo- and shear-induced responsive capabilities were studied through rheology. The graft copolymer formed a 3D network through thermo-induced hydrophobic association of the thermo-responsive P(NIPAM-co-NtBAM) side chains in water. By applying the frequency-temperature superposition principle, the terminal relaxation time, τ and the shear viscosity, as a function of temperature were evaluated. Both parameters increased exponentially upon heating orders of magnitude, 15 °C above the onset of gelation (35 °C). It is shown that the thermo-induced thickening effect was mainly due to the slowdown of the P(NIPAM 90 -co-NtBAM 10) associative side chains exchange dynamics. Moreover, combination of shear- and thermo-responsiveness provided excellent hydrogel injectability with instantaneous gelation at physiological temperature. The better insight of the thermo-thickening mechanism through oscillatory rheology allows precise tuning of the carbohydrate-based hydrogel properties towards potential bioapplications. [ABSTRACT FROM AUTHOR]

• Novel ASA- g -(THF 5 - b -PIB) copolymers with pH sensitive drug release were achieved. • Crystallization and hydrophilicity of graft copolymer was mediated by PIB branches. • Copolymer/Ag nanocomposites behave antibacterial property and protein resistance. Sodium alginate (SA) is a marine-derived biocompatible polysaccharide with huge reserves and polyisobutylene (PIB) is a saturated elastomer with gas barrier property, bio-inertness, and biocompatibility. Herein, we developed the biomass-based ASA- g -(THF 5 - b -PIB) graft copolymer/Ag (3–11 nm, 0.7–3.8%) nanocomposites formed in-situ via combination of transition of terminal groups in PIB chains with grafting-onto method. The above graft copolymers exhibit microphase separation by self-assembly for the difference in chemical structure from backbone and branches and annealing process as well. The crystallization morphology from backbone depends on the M n,PIB and G N , changing from thin strip to rod-like crystal. The pH sensitivity happens in drug release behavior of ASA- g -(THF 5 - b -PIB) micelles, which reach 100% of drug-release within 40 h at pH = 7.4. The ASA- g -(THF 5 - b -PIB)/Ag composites behave good antibacterial properties to both E. coli and S. aureus and anti-protein adsorption performance. This novel graft copolymer with comprehensive properties and would have a prospect in biomedical field. [ABSTRACT FROM AUTHOR]

• Gel beads based on chitosan, sodium alginate and graphene oxide@Fe 3 O 4 were prepared. • Adsorption capacity of the gel beads to Cu2+ and Cd2+ reached 55.96 and 86.28 mg/g. • The magnetic gel beads had selective adsorption toward Pb2+ (189.04 mg/g). • Addition of graphene oxide@Fe 3 O 4 enhanced stability and recyclability of gel beads. • The gel beads showed good adsorption efficiency in the simulated real environment. As a kind of potential absorbent, polysaccharide materials are limited due to weak stability, low absorption and recovery rate. Herein, a novel composite adsorbent – the magnetic composite gel beads (CMC/SA/graphene oxide@Fe 3 O 4) were prepared by combining carboxymethyl chitosan (CMC), sodium alginate (SA) with graphene oxide@Fe 3 O 4 , and then utilized for the adsorption of Cu2+, Cd2+ and Pb2+ from the wastewater. The physicochemical property of CMC/SA/graphene oxide@Fe 3 O 4 beads were characterized in detail. The CMC/SA/graphene oxide@Fe 3 O 4 magnetic gel beads could separate easily from the wastewater and showed a higher stability due to the addition of graphene oxide@Fe 3 O 4. The adsorption experiments show that the adsorption of Cu2+, Cd2+ and Pb2+ on the magnetic gel bead was well fitted with pseudo-second-order model and Langmuir isotherm model, and the maximum adsorption capacity of Cu2+, Cd2+ and Pb2+ reached 55.96, 86.28 and 189.04 mg/g, respectively. Moreover, the magnetic gel beads had selective adsorption toward Pb2+. In addition, the magnetic gel beads still obtained 90% of the adsorption rates after five cycles, and showed good adsorption efficiency in the simulated real environment. This work proves that the CMC/SA/graphene oxide@Fe 3 O 4 magnetic gel beads as the adsorbents have promising potential in wastewater treatment. [ABSTRACT FROM AUTHOR]

Highlights • Novel supersaturating drug delivery systems of chlorthalidone were developed. • Sodium alginate effects on spray dried solid dispersions were investigated. • It was demonstrated the sodium alginate ability to sustain drug supersaturation. • Sodium alginate with Soluplus® or sodium lauryl sulfate sustain drug supersaturation. Abstract Solid dispersions (SDs) of chlorthalidone (CTD) are promising systems to enhance drug dissolution rate, generate and maintain drug supersaturation levels in gastrointestinal fluids. In this work, SDs of CTD were prepared by spray drying using sodium alginate (SA) as carrier. Six formulations were prepared, varying the drug loading and composition, through the combination of SA with surfactants (sodium lauryl sulfate (SLS) or polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (SOL)). In all SDs, except when SA was used alone at low drug loading, CTD was in the amorphous form. At sink conditions, all SDs showed a faster dissolution rate than the crystalline drug. At non-sink conditions, the SDs prepared with SA and SLS at low drug loading exhibited the best performance to maintain supersaturating drug levels. All SDs, except those prepared with SA alone or SA-SLS at high drug loading, presented no drug recrystallization after 34 months of storage. [ABSTRACT FROM AUTHOR]

Highlights • Castor oil-based waterborne polyurethane/sodium alginate composites were prepared. • The effect of sodium alginate content on the properties of the polymers was studied. • The formation of interpenetrating networks leads to the properties improvement. • Increasing sodium alginate content improves thermal stability of the composite films. Abstract In this paper, bio-based waterborne polyurethane dispersions were successfully prepared from castor oil using 2, 2-dimethylolbutanoic acid as the chain extender. Then, a series of bio-based composite dispersions and films were prepared by blending different amounts of sodium alginate aqueous solution with these bio-based polyurethane dispersions. The chemical structures, thermo-mechanical properties, thermal stability, and mechanical properties of the resulting composite films were characterized and discussed. The results show that the tensile strength and storage moduli of the composite films increase while the elongation at break of the composite films decrease with increasing the sodium alginate content. In addition, the contact angle and thermal stability of the composite films also increase with increasing sodium alginate content. These improvements are related to the increase of the crosslink density and the formation of interpenetrating networks with introduction of sodium alginate macromolecule. [ABSTRACT FROM AUTHOR]

Highlights • Gelled microparticles (GMP) were fabricated from whey protein and alginate. • Incorporation of fiber to GMP was demonstrated by light and electron microscopy. • Texture profile analysis revealed good adhesiveness and cohesiveness of GMP. • GMP showed the behavior of a structured liquid with tan (δ) less than one. • GMP-DF could be used as soft fluid gels or mixed into purees or pastes. Abstract Dietary fiber (DF) - inulin (IN), bacterial cellulose nanofibers (BC), crystalline cellulose (CC) and oat fiber (OF) – were added at a concentration of 5% (2.5% for OF) to a whey protein isolate (WPI)/sodium alginate (NaAlg) dispersion. Gel microparticles (GMP) were formed by cold gelation followed by mechanical shearing. Compression stress-strain curves of bulk gels were similar for GMP-CC and GMP-OF but different from GMP-IN and GMP-BC. The soluble fiber IN did not change the aggregated matrix of the parent WPI/NaAlg gel, while other sources of DF became incorporated into the microgel matrix. Rheological tests (20 °C) revealed that GMP with added DF had a predominantly elastic behavior. Texture profile analysis suggested that GMP and GMP-IN had advantages over a commercial thickener in terms of adhesiveness and cohesiveness. GMP with added DF may find applications in foods for the elderly as texturizer and/or a carrier of fiber. [ABSTRACT FROM AUTHOR]

Highlights • Interpenetrating polymer network (IPN)-structured hydrogels were prepared. • Three different types of nanocellulose were incorporated into the hydrogels. • The hydrogels had an interconnected macro-porous structure. • The hydrogels could be utilized in multiple adsorption–desorption cycles. • The mechanical strength and adsorption capacity of hydrogels were enhanced by nanocellulose. Abstract In this study, interpenetrating polymer network (IPN)-structured hydrogels were fabricated through the crosslinking of neutral polyacrylamide (PAM, the first flexible network) and the polyelectrolyte sodium alginate (SA, the second rigid network). Three types of nanocellulose, including cellulose nanocrystals (CNCs), bacterial cellulose fibers (BCs) and 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-oxidized cellulose nanofibers (TOCNs), were well-dispersed in the SA-PAM gel matrix. The hydrogels, obtained with a high water content (∼83%), exhibit a macroporous structure with a mean pore size of 60 ± 51 μm and high transparency. Comparative studies indicate that BCs are more effective for enhancing the hydrogels due to their higher aspect ratio, and the compressive strength of SA-PAM-BC hydrogel is 6.59 times higher than that of neat SA-PAM. Meanwhile, TOCNs are the best fillers for improving the adsorption capacity owing to the presence of a carboxyl group, and the adsorption capacity of SA-PAM-TOCN is more than 1.3-fold that in SA-PAM. Prepared hydrogels with high mechanical strength and adsorption capacity are advantageous for their applications in wastewater treatments. [ABSTRACT FROM AUTHOR]

Highlights • Iodine was complexed with HL to improve its stability and complexing efficiency. • HLI/CMCS/SA composite membrane was prepared via microwave drying method. • The membrane showed excellent comprehensive properties. • The membrane exhibited pH controllable iodine release and antibacterial properties. • It exhibited high repairing efficiency for seawater immersed wound infection. Abstract Improving the antibacterial properties of membrane wound dressings of natural polymers is crucial. Iodine is an important safe inorganic antibacterial agent, but was confined in the composition with polymer membranes due to the challenges of homogeneity and stability during drying. In the present work, iodine was complexed with hydroxylated lecithin (HL) to improve its stability and complexing efficiency for the composition with carboxymethly chitosan/sodium alginate. With the aid of microwave drying, hydroxylated lecithin complexed iodine/carboxymethly chitosan/sodium alginate (HLI/CMCS/SA) composite membranes with homogeneously distributions of HLI, high contents of activated iodine, good mechanical and swelling properties, proper water vapor permeability, pH controllable iodine release and excellent antibacterial properties were prepared. The composite membranes exhibited high repairing efficiencies for the infection of a rat model of the seawater immersed wound infection of deep partial-thickness burns. This novel antibacterial composite membrane can be potentially used as a high performance wound dressing for treating and repairing open trauma infections. [ABSTRACT FROM AUTHOR]

Highlights • Dehydration of sodium alginate (SA) film occurs in two stages upon heating. • Water molecules disrupt the inter/intra-molecular hydrogen bonding in SA. • Hydrogen bonding within SA chains could be O3H3⋯O5 and O2H2 ⋯ O C O−. • COO− groups are more associated with water molecules. Abstract In this paper, the heat-induced hydrogen bonding evolution in the sodium alginate (SA) film is explored mainly by FTIR spectroscopy in combination with perturbation correlation moving window (PCMW) technique and 2D correlation spectroscopy (2Dcos). Due to the strong hydrophilicity, hydrogen bonds formed between water molecules and polar groups (including OH and COO−) along SA chains hold an predominant role at room temperature, which is believed to disrupt the inter/intra-molecular hydrogen bonding in SA chains. During heating from 30 to 60 °C, most water molecules evaporate abruptly, resulting in the formation of inter/intra-molecular hydrogen bonding within SA chains, such as O3H3 ... O5 and O2H2 ... O = C–O−. Upon further heating form 60 to 170 °C, both inter/intra-molecular hydrogen bonding in SA chains and hydrogen bonds of SA with water molecules are gradually broken, leading to the appearance of relatively free C OH and COO− groups. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Synthesis of polyurethane (PU) film based on TS-SA as a RO membrane. • High thermal and mechanical propertise of PU based on TS-SA. • High hydrophilicity of PU based on TS-SA. • High efficiency of PU based on TS-SA for desalination at high temperature-pressure. Abstract In this study, a series of polyurethane (PU) films based on three different type of chain extenders including glycerol, sodium alginate (SA) and nanocomposite of tetrasodium thiacalix[4]arene tetrasulfonate-sodium alginate (TS-SA) were synthesized. The effect of SA and TS-SA chain extenders on different properties of the PU films were studied using FTIR, XRD, DSC, TGA, SEM, AFM, and tensile analysis and the obtained results were compared with the polyurethane film extended with glycerol. The TGA and tensile studies confirmed that incorporation of TS-SA into the polyurethane backbone provide the superior thermal and mechanical properties compared to SA. Moreover, the influence of the SA and TS-SA chain extenders on hydrophilicity of the prepared films was also investigated by contact angle measurement. The results showed that the hydrophilicity of PU/TS-SA is higher than the PU/Gly and PU/SA samples. In comparison with PU/Gly and PU/SA samples, the PU/TS-SA sample showed significant performance in water desalination via reverse osmosis technique due to its favorable porosity and improved hydrophilicity. The AFM analysis confirmed that the PU/TS-SA sample has the highest surface rouphness which cause an increase in the flux and anti-fouling property of this sample. Therefore, PU/TS-SA sample can be introduced as an efficient membrane for water desalination with enhanced thermal stability, mechanical properties, high salt rejection and water permeability. [ABSTRACT FROM AUTHOR]

Highlights • A precise and fast measurement for alginate hydrogel formation with CaCl 2 is proposed. • The measurement principle is based on the gel inhomogeneity (core/shell). • The method can supplement high temperature NMR analysis of G/M ratio. Abstract Although alginate-based hydrogels are widely used, determining their mechanical properties and explaining their ability to form a hydrogel in situ remains a challenge. A new method of external gelation using calcium chloride (CaCl 2) is proposed to quantify the formation of alginate hydrogel and its mechanical properties as well as to observe its temporal behaviour. To this end, small inhomogeneous alginate beads were formed, which comprised a shell and a core. The bead's shell consisted of calcium alginate hydrogel, while its core was sodium alginate sol. The beads were mechanically tested with a texture analyser to provide a detailed description of the structure. Different alginate samples could be clearly identified, and the M(mannuron)/G(guluron) acid ratios could be extrapolated quickly and easily from the test results if calibrated by NMR. This enables a fast and cost-effective characterisation of different alginates with regard to their composition and gel formation properties. [ABSTRACT FROM AUTHOR]