Design of a novel polysaccharide-based cryogel using triallyl cyanurate as crosslinker for cell adhesion and proliferation

Development of interpenetrating network hydrogels: Enhancing the release and bioaccessibility of green tea polyphenols

Green Tea polyphenols (GTP) are important bioactive compounds with excellent physiological regulation functions. However, they are easily destroyed by the gastric environment during digestion. In this work, a sodium alginate (SA)-gellan gum (GG) interpenetrating network (IPN) hydrogel was synthesized to protect and delivery GTP. The ratio of SA/GG significantly affects the network structure of IPN hydrogels and the performance of delivering GTP. The hydrogel formed by interpenetrating 20 % GG with 80 % SA as the main network had the highest water uptake (55 g/g), holding capacity (950 mg/g), and freeze-thaw stability, with springiness reaching 0.933 and hardness reaching 1300 g, which due to the filling effect and non-covalent interaction. Rheological tests showed that the crosslink density of IPN hydrogel in SA-dominated network was improved by the addition of GG to make it better bound to GTP, and the higher water uptake meant that the system could absorb more GTP-containing solution. This IPN hydrogel maintained 917.3 mg/g encapsulation efficiency at the highest loading capacity (1080 mg/g) in tests as delivery system. In in vitro digestion simulations, owing to the pH responsiveness, the IPN hydrogel reduced the loss of GTP in gastric fluid, achieving a bioaccessibility of 71.6 % in the intestinal tract.

Self-healing, ultra-stretchable, and highly sensitive conductive hydrogel reinforced by sulfate polysaccharide from Enteromorpha prolifera for human motion sensing

The synthesis of multifunctional conductive hydrogel has attracted extensive attention worldwide due to their integrated properties of stretchability, self-adhesion, self-healing, and high sensitivity, while it is still a challenge. Although various kinds of polysaccharides and their derivatives are used to achieve the aforementioned objective, there are few researches about hydrogel design introducing sulfated polysaccharide from Enteromorpha prolifera (SPE), which is rich in hydroxyl, sulfate, and carboxyl groups providing amounts of reaction sites for hydrogel synthesis. Herein, conductive hydrogel (PAA-Al3+-SPE3) reinforced by SPE was designed by simple one pot hot polymerization method. This hydrogel demonstrated charming extension ratio (up to 4027.40 %), strain stress (up to 59.94 kPa), compressive strength (19.71 Mpa), and high conductivity sensibility (GF 6.76, 300 % - 700 %). Additionally, PAA-Al3+-SPE3 showed good self-healing property (repaired autonomously after 60 s) and satisfied self-adhesion (31.11 kPa) due to the reversible hydrogen bonds and metal coordination interactions. Furthermore, the PAA-Al3+-SPE3 hydrogel showed great real-time sensing performance to monitor various motions. These findings suggest the potential of PAA-Al3+-SPE3 hydrogel as an affordable and reliable conductive sensing material. Meantime, the first utilization of SPE to construct flexible wearable sensors offers new route for the high-value application of Enteromorpha prolifera.

Carboxymethyl chitosan/sodium alginate hydrogel films with good biocompatibility and reproducibility by in situ ultra-fast crosslinking for efficient preservation of strawberry

Strawberry is a seasonal and regional fruit. Thus, strawberry waste caused by spoilage and decay is an urgent problem that must be solved. Developing hydrogel films (HGF) for multifunctional food packaging can effectively slow down strawberry. Based on the carboxymethyl chitosan/sodium alginate/citric acid with excellent biocompatibility, preservation effect, and ultrafast (10 s) coating on the strawberry surface, HGF specimens were designed and prepared through the electrostatic interaction of opposite charges between polysaccharides. The prepared HGF specimen exhibited excellent low moisture permeability and antibacterial properties. Its lethality rates against both Escherichia coli and Staphylococcus aureus were more than >99 %. The HGF could keep strawberries fresh for up to 8, 19, and 48 days at 25.0, 5.0, and 0 °C, respectively, by delaying the fruits' ripening, dehydration, microbial invasion, and respiration rate. The HGF dissolved and regenerated five times still exhibited good performance. The water vapor transmission rate of the regenerative HGF could reach 98 % of that of the original HGF. The regenerative HGF could maintain the freshness of strawberries for up to 8 days at 25.0 °C. This study provides new insight into an alternative film design for convenient, green, and renewable alternative films to delay perishable fruit spoilage.

Photo-degradable salecan/xanthan gum ionic gel induced by iron (III) coordination for organic dye decontamination

As dye adsorbents with great potential, polysaccharide-based hydrogels are significantly hampered in practical application owing to intricate preparation methods, low absorption, and bad degradability. Salecan is a water-soluble extracellular polysaccharide with excellent physicochemical and biological properties. Here, salecan and xanthan gum were first used as a dual-precursors system, their mixed solution was crosslinked by Fe³⁺ to assemble a photo-degradable ionic gel for malachite green (MG) adsorption. Photo-degradation was done using visible light under very mild conditions, which gave rise to gel network dissolution and homogeneous solution formation. Extensive dynamic coordinate interactions between Fe³⁺ and polysaccharides maintained gel matrix stability and were systematically investigated. The control of water uptake, micro-structure, and rheology can be facilely implemented by tuning salecan/xanthan gum ratios. Furthermore, various parameters such as polysaccharide ratios, pHs, MG concentrations, and contact time affecting adsorption were optimized using batch experiments. Adsorption process accurately adhered to pseudo-second-order kinetic and Langmuir isotherm model, with the maximum adsorption capacity of 463.0 mg/g. Such mechanism implied monolayer chemisorptive characteristics. The gel exhibited satisfactory reusability and was recycled five times without apparent decrease in adsorption capacity. From these results, the photo-degradable Fe³⁺-induced salecan/xanthan gum ionic gel is an alternative and sustainable absorbent for MG removal.

The production of pH indicator Ca and Cu alginate ((1,4)- β -d-mannuronic acid and α -l-guluronic acid) cryogels containing anthocyanin obtained via red cabbage extraction for monitoring chicken fillet freshness

In recent days, intelligent food packaging has gained attention due to consumers' needs and monitoring of the freshness of food. Biopolymers are used to produce matrix parts and dye chemicals, because of their unique properties, such as biodegradability and biocompatibility. In this study, alginate molecules and anthocyanins were used to produce to monitor chicken fillet freshness via pH response characteristics. Anthocyanins' color and UV characteristics at different pHs were investigated. The obtained anthocyanin solution showed visible color response at different pH level. In the red cabbage extract, the anthocyanin concentration was as 0.65 ± 0.03 mg/g. Alginate and extracted anthocyanins from red cabbage were mixed at the solution phase, then metal alginate hydrogels were synthesized via crosslinking Ca²⁺ and Cu²⁺ with alginate molecules. Due to the porous structure of the cryogels, hydrogels were freeze dried at -80 °C for 24 h at vacuum atmosphere. The obtained cryogel indicated significant color changes from pH 4 to pH 10, and at a basic environment, the color change was observed with the naked eye. The porosity amounts and sizes of the produced cryogels were examined, the average pore amount of cryogels was found to be 85.46 ± 4.36 %, and the average pore size 97.98 ± 26.20 μm. Furthermore, it was seen that the color change was not directly related to the porosity, but the interaction of anthocyanin and metal alginate matrix effected color changes degree of cryogels. Due to the electronegativity of Cu²⁺ ions, and the use of a low amount of anthocyanin was found to be more suitable for color change. The color was changed to blue-purple while total volatile basic nitrogen content increased to 46.67 mg/100 g from 14.00 mg/100 g. As a result, prepared cryogels should be a better candidates for use as a freshness indicator and intelligent packaging.

Sustainable Multi-Network Cationic Cryogels for High-Efficiency Removal of Hazardous Oxyanions from Aqueous Solutions

It is still a challenge to develop advanced materials able to simultaneously remove more than one pollutant. Exclusive cationic composite double- and triple-network cryogels, with adequate sustainability in the removal of Cr₂O₇^2- and H₂PO₄^- oxyanions, were developed in this work starting from single-network (SN) sponges. Chitosan (CS), as the only polycation originating from renewable resources, and poly(N,N-dimethylaminoethylmethacrylate) (PDMAEMA) and polyethyleneimine (PEI), as synthetic polycations, were employed to construct multi-network cationic composite cryogels. The properties of the composites were tailored by the cross-linking degree of the first network (SN5 and SN20, which means CS with 5 or 20 mole % of glutaraldehyde, respectively) and by the order of the successive networks. FTIR, SEM-EDX, equilibrium water content and compressive tests were used in the exhaustive characterization of these polymeric composites. The sorption performances towards Cr₂O₇^2- and H₂PO₄^- anions were evaluated in batch mode. The pseudo-first-order, pseudo-second-order (PSO) and Elovich kinetics models, and the Langmuir, Freundlich and Sips isotherm models were used to interpret the experimental results. The adsorption data were the best fitted by the PSO kinetic model and by the Sips isotherm model, indicating that the sorption mechanism was mainly controlled by chemisorption, irrespective of the structure and number of networks. The maximum sorption capacity for both oxyanions increased with the increase in the number of networks, the highest values being found for the multi-network sponges having SN5 cryogel as the first network. In binary systems, all sorbents preferred Cr₂O₇^2- ions, the selectivity coefficient being the highest for TN sponges. The high sorption capacity and remarkable reusability, with only a 4-6% drop in the sorption capacity after five sorption-desorption cycles, recommend these composite cryogels in the removal of two of the most dangerous pollutants represented by Cr₂O₇^2- and H₂PO₄^-.

Adsorption behavior and mechanism of Lead (Pb2+) by sulfate polysaccharide from Enteromorpha prolifera

Lead (Pb²⁺) pollution poses severe healthy and ecological risks to humans. In this work, sulfate polysaccharide from Enteromorpha prolifera (SPE) was utilized for Pb²⁺ adsorption from simulated intestinal fluid. In order to evaluate its adsorption behaviors comprehensively, batch adsorption of Pb²⁺ was investigated under different conditions. Results showed that SPE presents high adsorption ability for Pb²⁺ through chemical adsorption process and the maximum adsorption capacity for Pb²⁺ was 278.5 mg/g. And SPE exhibited higher removal efficiency (≥60%) for trace Pb²⁺ (<10 mg/L) compared to that of other adsorbents based on polysaccharide. Besides, its adsorption can be described by Langmuir isotherm and pseudo-second-order kinetic models. Further, XRD, FTIR, and XPS were used to characterize the possible interaction of Pb²⁺ with SPE, and the results showed that carboxyl and hydroxyl groups in SPE play more important role than that of sulfate group. Our work represents the first assessment of Pb²⁺ adsorption properties of SPE. This investigation highlights the potential application of SPE to protect the body from hazard of food-derived heavy metals.

Novel Water-in-Oil Emulsions for Co-Loading Sialic Acid and Chitosan: Formulation, Characterization, and Stability Evaluation

This study was designed to co-load sialic acid (SA) and chitosan in a water-in-oil (W/O) emulsion and investigated its characterization and stability. Emulsions were prepared using two different oils (olive oil and maize oil) and polyglycerol polyricinoleate (PGPR) alone or in combination with lecithin (LE) as emulsifiers. The results revealed that the aqueous phase of 5% (w/v) SA and 2% (w/v) chitosan could form a stable complex and make the aqueous phase into a transparent colloidal state. Increasing the concentration of PGPR and LE presented different effects on emulsion formation between olive oil-base and maize oil-base. Two stable W/O emulsions that were olive oil-based with 1.5% (w/v) PGPR+ 0.5% (w/v) LE and maize oil-based with 2% (w/v) PGPR+ 0% (w/v) LE were obtained. Initial droplet size distribution curves of the two stable emulsions displayed unimodal distribution, and the rheological curves displayed the characteristics of shear thinning and low static shear viscosity. Moreover, the storage stability showed that there was no significant change in droplet size distribution and Sauter mean diameter of the emulsions at room temperature (25 °C) for 30 days. These results indicated that the W/O emulsions could effectively co-load and protect sialic acid and chitosan and thus could be a novel method for increasing the stability of these water-soluble bioactive compounds.

Simple ultrasonic-assisted approach to prepare polysaccharide-based aerogel for cell research and histocompatibility study

Salecan, a water-soluble microbial polysaccharide with attractive biocompatible characteristics, is very suitable for aerogel fabrication. However, the practical application of salecan-based aerogels for cell culture was limited by complicated preparation method, lack of cell anchorage signals, and the ability to modulate this properly. Here, a smart aerogel was designed by ultrasonic-assisted self-assembly of salecan and cationic starch (CAS) without any organic and toxic crosslinkers. The ultrasound waves generated a marked impact on self-assemble process by means of ultrasonic cavitation. Aerogel network was produced by strong electrostatic attractions between the polysaccharides. Especially, salecan/CAS ratio can be precisely modulated to tailor the hydrophilicity, mechanical stiffness, and morphologic property. The specific surface area of the aerogels gradually increased with the increase in salecan/CAS ratio. These aerogels were non-cytotoxic, and the incorporation of salecan into them promoted cell-matrix interactions by directionally supporting cell adhesion and proliferation. Most strikingly, in vivo experiment revealed that the histological features in the main organs of the mice were similar to those observed in the PBS-treated control group, and no sign of the histopathological abnormality or tissue destruction was observed, indicating the excellent histocompatibility of the aerogels. This study offered a new and powerful avenue to fabricate functional biomaterial.

Pholiota nameko Polysaccharides Promotes Cell Proliferation and Migration and Reduces ROS Content in H2O2-Induced L929 Cells

Pholiota nameko, a type of edible and medicinal fungus, is currently grown extensively for food and traditional medicine in China and Japan. It possesses various biological activities, such as anti-inflammatory, anti-hyperlipidemia and antitumor activities. However, P. nameko has rarely been discussed in the field of dermatology; identifying its biological activities could be beneficial in development of a new natural ingredient used in wound care. To evaluate its in vitro wound healing activities, the present study assessed the antioxidant and anti-collagenase activities of P. nameko polysaccharides (PNPs) prepared through fractional precipitation (40%, 60% and 80% (v/v)); the assessments were conducted using reducing power, hydroxyl radical scavenging activity, dichloro-dihydro-fluorescein diacetate and collagenase activity assays. The ability of PNPs to facilitate L929 fibroblast cell proliferation and migration was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and scratch assays. The findings indicated that, among all fractions, PNP-80 showed the best antioxidant and anti-collagenase activity, as measured by their reducing power (IC₅₀ of PNP-80 was 2.43 ± 0.17 mg/mL), the hydroxyl radical scavenging (IC₅₀ of PNP-80 was 2.74 ± 0.11 mg/mL) and collagenase activity assay, and significantly reduced cellular ROS content, compared with that of H₂O₂-induced L929 cells. Moreover, PNP-80 significantly promoted L929 fibroblast proliferation and migration, compared with the control group. Overall, we suggested that PNP-80 could be a promising candidate for further evaluation of its potential application on wound healing.