Study of alginate-encapsulated phycoerythrin in promoting the biological activity of synbiotic ice cream with Lactobacillus casei.

This study examines the effect of phycoerythrin (PE) from a cyanobacterial Nostoc strain encapsulated with alginate as a potential prebiotic to produce synbiotic ice cream products with Lactobacillus casei. It was found that the addition of the encapsulated PE affected, mostly favourably, the physicochemical properties, antioxidant activity, probiotic survival, volatile compound contents, and sensory acceptability of the synbiotic ice cream samples before and after aging at the freezing periods of one day to eight weeks. Thus, it confirms the prebiotic potential of PE for synbiotic ice creams with L. casei.

Oral administration of encapsulated catechin in chitosan-alginate nanoparticles improves cognitive function and neurodegeneration in an aluminum chloride-induced rat model of Alzheimer's disease.

The present study aimed to investigate the effect of catechin-loaded Chitosan-Alginate nanoparticles (NPs) on cognitive function in an aluminum chloride (AlCl3)-induced rat model of Alzheimer's disease (AD). The Catechin-loaded Chitosan-Alginate nanocarriers were synthesized through ionotropic gelation (IG) method. Physio-chemical characterization was conducted with the Zetasizer Nano system, the scanning electron microscope, and the Fourier transform infrared spectroscopy. The experiments were performed over 21 days on six groups of male Wistar rats. The control group, AlCl3 treated group, Catechin group, nanocarrier group, treatment group 1 (AlCl3 + Catechin), and treatment group 2 (AlCl3 + nanocarrier). A behavioral study was done by the Morris water maze (MWM) test. In addition, the level of oxidative indices and acetylcholine esterase (AChE) activity was determined by standard procedures at the end of the study. AlCl3 induced a significant increase in AChE activity, along with a significant decrease in the level of Catalase (CAT) and total antioxidant capacity (TAC) in the hippocampus. Moreover, the significant effect of AlCl3 was observed on the behavioral parameters of the MWM test. Both forms of Catechin markedly improved AChE activity, oxidative biomarkers, spatial memory, and learning. The present study indicated that the administration of Catechin-loaded Chitosan-Alginate NPs is a beneficial therapeutic option against behavioral and chemical alteration of AD in male Wistar rats.

Novel L-(CaP-ZnP)/SA Nanocomposite Hydrogel with Dual Anti-Inflammatory and Mineralization Effects for Efficient Vital Pulp Therapy.

Background: Vital pulp therapy (VPT) is considered a conservative treatment for preserving pulp viability in caries and trauma-induced pulpitis. However, Mineral trioxide aggregate (MTA) as the most frequently used repair material, exhibits limited efficacy under inflammatory conditions. This study introduces an innovative nanocomposite hydrogel, tailored to simultaneously target anti-inflammation and dentin mineralization, aiming to efficiently preserve vital pulp tissue. Methods: The L-(CaP-ZnP)/SA nanocomposite hydrogel was designed by combining L-Arginine modified calcium phosphate/zinc phosphate nanoparticles (L-(CaP-ZnP) NPs) with sodium alginate (SA), and was characterized with TEM, SEM, FTIR, EDX, ICP-AES, and Zeta potential. In vitro, we evaluated the cytotoxicity and anti-inflammatory properties. Human dental pulp stem cells (hDPSCs) were cultured with lipopolysaccharide (LPS) to induce an inflammatory response, and the cell odontogenic differentiation was measured and possible signaling pathways were explored by alkaline phosphatase (ALP)/alizarin red S (ARS) staining, qRT-PCR, immunofluorescence staining, and Western blotting, respectively. In vivo, a pulpitis model was utilized to explore the potential of the L-(CaP-ZnP)/SA nanocomposite hydrogel in controlling pulp inflammation and enhancing dentin mineralization by Hematoxylin and eosin (HE) staining and immunohistochemistry staining. Results: In vitro experiments revealed that the nanocomposite hydrogel was synthesized successfully and presented desirable biocompatibility. Under inflammatory conditions, compared to MTA, the L-(CaP-ZnP)/SA nanocomposite hydrogel demonstrated superior anti-inflammatory and pro-odontogenesis effects. Furthermore, the nanocomposite hydrogel significantly augmented p38 phosphorylation, implicating the involvement of the p38 signaling pathway in pulp repair. Significantly, in a rat pulpitis model, the L-(CaP-ZnP)/SA nanocomposite hydrogel downregulated inflammatory markers while upregulating mineralization-related markers, thereby stimulating the formation of robust reparative dentin. Conclusion: The L-(CaP-ZnP)/SA nanocomposite hydrogel with good biocompatibility efficiently promoted inflammation resolution and enhanced dentin mineralization by activating p38 signal pathway, as a pulp-capping material, offering a promising and advanced solution for treatment of pulpitis.

Bone Morphogenetic Protein 7-Loaded Gelatin Methacrylate/Oxidized Sodium Alginate/Nano-Hydroxyapatite Composite Hydrogel for Bone Tissue Engineering.

Background: Bone tissue engineering (BTE) is a promising alternative to autologous bone grafting for the clinical treatment of bone defects, and inorganic/organic composite hydrogels as BTE scaffolds are a hot spot in current research. The construction of nano-hydroxyapatite/gelatin methacrylate/oxidized sodium alginate (nHAP/GelMA/OSA), abbreviated as HGO, composite hydrogels loaded with bone morphogenetic protein 7 (BMP7) will provide a suitable 3D microenvironment to promote cell aggregation, proliferation, and differentiation, thus facilitating bone repair and regeneration. Methods: Dually-crosslinked hydrogels were fabricated by combining GelMA and OSA, while HGO hydrogels were formulated by incorporating varying amounts of nHAP. The hydrogels were physically and chemically characterized followed by the assessment of their biocompatibility. BMP7-HGO (BHGO) hydrogels were fabricated by incorporating suitable concentrations of BMP7 into HGO hydrogels. The osteogenic potential of BHGO hydrogels was then validated through in vitro experiments and using rat femoral defect models. Results: The addition of nHAP significantly improved the physical properties of the hydrogel, and the composite hydrogel with 10% nHAP demonstrated the best overall performance among all groups. The selected concentration of HGO hydrogel served as a carrier for BMP7 loading and was evaluated for its osteogenic potential both in vivo and in vitro. The BHGO hydrogel demonstrated superior in vitro osteogenic induction and in vivo potential for repairing bone tissue compared to the outcomes observed in the blank control, BMP7, and HGO groups. Conclusion: Using hydrogel containing 10% HGO appears promising for bone tissue engineering scaffolds, especially when loaded with BMP7 to boost its osteogenic potential. However, further investigation is needed to optimize the GelMA, OSA, and nHAP ratios, along with the BMP7 concentration, to maximize the osteogenic potential.

Oral microsphere formulation of M2 macrophage-mimetic Janus nanomotor for targeted therapy of ulcerative colitis.

Oral medication for ulcerative colitis (UC) is often hindered by challenges such as inadequate accumulation, limited penetration of mucus barriers, and the intricate task of mitigating excessive ROS and inflammatory cytokines. Here, we present a strategy involving sodium alginate microspheres (SAMs) incorporating M2 macrophage membrane (M2M)-coated Janus nanomotors (denominated as Motor@M2M) for targeted treatment of UC. SAM provides a protective barrier, ensuring that Motor@M2M withstands the harsh gastric milieu and exhibits controlled release. M2M enhances the targeting precision of nanomotors to inflammatory tissues and acts as a decoy for the neutralization of inflammatory cytokines. Catalytic decomposition of H2O2 by MnO2 in the oxidative microenvironment generates O2 bubbles, propelling Motor@M2M across the mucus barrier into inflamed colon tissues. Upon oral administration, Motor@M2M@SAM notably ameliorated UC severity, including inflammation mitigation, ROS scavenging, macrophage reprogramming, and restoration of the intestinal barrier and microbiota. Consequently, our investigation introduces a promising oral microsphere formulation of macrophage-biomimetic nanorobots, providing a promising approach for UC treatment.

Improvement of Alginate Extraction from Brown Seaweed (Laminaria digitata L.) and Valorization of Its Remaining Ethanolic Fraction.

This study aimed to improve the conventional procedure of alginate isolation from the brown seaweed (Laminaria digitata L.) biomass and investigate the possibility of further valorization of the ethanolic fraction representing the byproduct after the degreasing and depigmentation of biomass. The acid treatment of biomass supported by ultrasound was modeled and optimized regarding the alginate yield using a response surface methodology based on the Box-Behnken design. A treatment time of 30 min, a liquid-to-solid ratio of 30 mL/g, and a treatment temperature of 47 °C were proposed as optimal conditions under which the alginate yield related to the mass of dry biomass was 30.9%. The use of ultrasonic radiation significantly reduced the time required for the acid treatment of biomass by about 4 to 24 times compared to other available conventional procedures. The isolated alginate had an M/G ratio of 1.08, which indicates a greater presence of M-blocks in its structure and the possibility of forming a soft and elastic hydrogel with its use. The chemical composition of the ethanolic fraction including total antioxidant content (293 mg gallic acid equivalent/g dry weight), total flavonoid content (14.9 mg rutin equivalent/g dry weight), contents of macroelements (the highest content of sodium, 106.59 mg/g dry weight), and microelement content (the highest content of boron, 198.84 mg/g dry weight) was determined, and the identification of bioactive compounds was carried out. The results of ultra high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry analysis confirmed the presence of 48 compounds, of which 41 compounds were identified as sugar alcohol, phenolic compounds, and lipids. According to the 2,2-diphenyl-1-picrylhydrazyl assay, the radical scavenging activity of the ethanolic fraction (the half-maximal inhibitory concentration of 42.84 ± 0.81 µg/mL) indicated its strong activity, which was almost the same as in the case of the positive control, synthetic antioxidant butylhydroxytoluene (the half-maximal inhibitory concentration of 36.61 ± 0.79 µg/mL). Gram-positive bacteria (Staphylococcus aureus, Enterococcus faecalis, and Bacillus cereus) were more sensitive to the ethanolic fraction compared to Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, and Shigella sonnei). The obtained results indicated the possibility of the further use of the ethanolic fraction as a fertilizer for plant growth in different species and antifouling agents, applicable in aquaculture.

Screening of Short-Chain Antimicrobial Peptide LKARI with Broad-Spectrum Bactericidal Properties and Its Application in Promoting Wound Healing.

Due to the extensive use of antibiotics, many highly resistant bacteria and extensively resistant bacteria have been produced. In recent years, the increase of drug-resistant bacteria and the resulting proliferation of drug-resistant bacteria have increased the incidence of hospital-acquired infections and caused great harm to human health. Antimicrobial peptides (AMPs) are considered to be an innovative antibiotic and belong to the latest advances in this field. We designed a polypeptide and verified its low minimum inhibitory concentration and broad-spectrum activity against Gram-positive bacteria, Gram-negative bacteria, and fungi in microbiology and pharmacology. Several experiments have confirmed that the screened antimicrobial peptides have significant antidrug resistance and also show significant therapeutic properties in the treatment of systemic bacterial infections. In addition, through our experimental research, it was proved that the antibacterial hydrogel composed of poly(vinyl alcohol), sodium alginate, and antimicrobial peptides had excellent antibacterial properties and showed good wound healing ability.

Chloride Ions-Responsive Intelligent Coatings for the Active Protection of Degradable Biomedical Mg Alloys.

In this work, the hydroxyapatite (HA) microspheres are utilized as carriers for 8-hydroxyquinoline (8-HQ) inhibitors with a sodium alginate-silver nitrate layer (Ag-SA) added to confer chloride-responsive properties. These 8-HQ@Ag-SA-HA microspheres are subsequently integrated into poly(lactic acid) (PLA) coatings to produce biocompatible coatings. The resulting 8-HQ@Ag-SA-HA microsphere exhibits a spherical structure with a diameter of 3.16 µm. Thermogravimetric analysis indicates that the encapsulated 8-HQ inhibitors are approximately 11.83 wt %. Furthermore, the incorporation of these microspheres fills the micropores within the PLA coating, leading to a denser coating surface, enhanced wettability (contact angle value = 88°), and improved adhesion strength, thereby reinforcing the physical barrier effect. Corrosion tests reveal that the coatings exhibit increased resistance to corrosion in simulated body fluid (SBF) solutions. The released 8-HQ inhibitors in response to chloride ions form a protective layer of Mg(HQ)2, providing the coatings with self-healing properties and ensuring their durability in the SBF environment. Additionally, the cell test demonstrates a significant presence of MG-63 cells, accompanied by a low hemolysis rate of 3.81%, confirming the exceptional biocompatibility of the coatings. These findings offer valuable insights into the development of stimuli-responsive biocompatible coatings for effectively protecting Mg alloys.

The role of pore size and mechanical properties on the accumulation, retention and distribution of F98 glioblastoma cells in macroporous hydrogels.

Glioblastoma (GBM) accounts for half of all central nervous system tumors. Once the tumor is removed, many GBM cells remain present near the surgical cavity and infiltrate the brain up to a distance of 20-30 mm, resulting in recurrence a few months later. GBM remains incurable due to the limited efficiency of current treatments, a result of the blood-brain barrier and sensitivity of healthy brain tissues to chemotherapy and radiation. A new therapeutic paradigm under development to treat GBM is to attract and accumulate GBM cells in a cancer cell trap inserted in the surgical cavity after tumor resection. In this work, porous gels were prepared using porous polylactide molds obtained from melt-processed co-continuous polymer blends of polystyrene and polylactide, with an average pore size ranging from 5 µm to over 500 µm. In order to efficiently accumulate and retain GBM brain cancer cells within a macroporous sodium alginate-based hydrogel trap, the pores must have an average diameter superior to 100 µm, with the best results obtained at 225 µm. In that case, the accumulation and retention of F98 GBM cells were more homogeneous, especially when functionalized with RGD adhesion peptides. At an alginate concentration of 1% w/v, the compression modulus reaches 15 kPa, close to the average value of 1-2 kPa reported for brain tissues, while adhesion and retention were also superior compared to 2% w/v gels. Overall, 1% w/v gels with 225 µm pores functionalized with the RGD peptide display the best performances.

Self-Powered Engineering of Cell Membrane Receptors to On-Demand Regulate Cellular Behaviors.

On-demand engineering of cell membrane receptors to nongenetically intervene in cellular behaviors is still a challenge. Herein, a membraneless enzyme biofuel cell-based self-powered biosensor (EBFC-SPB) was developed for autonomously and precisely releasing Zn2+ to initiate DNAzyme-based reprogramming of cell membrane receptors, which further mediates signal transduction to regulate cellular behaviors. The critical component of EBFC-SPB is a hydrogel film on a biocathode which is prepared using a Fe3+-cross-linked alginate hydrogel film loaded with Zn2+ ions. In the working mode in the presence of glucose/O2, the hydrogel is decomposed due to the reduction of Fe3+ to Fe2+, accompanied by rapid release of Zn2+ to specifically activate a Zn2+-responsive DNAzyme nanodevice on the cell surface, leading to the dimerization of homologous or nonhomologous receptors to promote or inhibit cell proliferation and migration. This EBFC-SPB platform provides a powerful "sensing-actuating-treating" tool for chemically regulating cellular behaviors, which holds great promise in precision biomedicine.

3D embedded bioprinting of large-scale intestine with complex structural organization and blood capillaries.

Accurate reproduction of human intestinal structure and functionin vitrois of great significance for understanding the development and disease occurrence of the gut. However, mostin vitrostudies are often confined to 2D models, 2.5D organ chips or 3D organoids, which cannot fully recapitulate the tissue architecture, microenvironment and cell compartmentalization foundin vivo. Herein, a centimeter-scale intestine tissue that contains intestinal features, such as hollow tubular structure, capillaries and tightly connected epithelium with invivo-likering folds, crypt-villi, and microvilli is constructed by 3D embedding bioprinting. In our strategy, a novel photocurable bioink composed of methacrylated gelatin, methacrylated sodium alginate and poly (ethylene glycol) diacrylate is developed for the fabrication of intestinal model. The Caco-2 cells implanted in the lumen are induced by the topological structures of the model to derive microvilli, crypt-villi, and tight junctions, simulating the intestinal epithelial barrier. The human umbilical vein endothelial cells encapsulated within the model gradually form microvessels, mimicking the dense capillary network in the intestine. This intestine-like tissue, which closely resembles the structure and cell arrangement of the human gut, can act as a platform to predict the therapeutic and toxic side effects of new drugs on the intestine.

Alginate-gelatine hydrogel microspheres protect NK cell proliferation and cytotoxicity under hypoxic conditions.

AIMS: This study aimed to encapsulate natural killer (NK) cells in a hydrogel to sustain their function within the hypoxic tumour microenvironments. METHODS: An alginate-gelatine hydrogel was generated via electrospray technology. Hydrogel biocompatibility was assessed through cell counting kit-8 and Live/Dead assays to ascertain cell. Moreover, we analysed lactate dehydrogenase assays to evaluate the cytotoxicity against tumours and utilised RT-qPCR to analyse cytokine gene level. RESULTS: Alginate and gelatine formed hydrogels with diameters ranging from 489.2 ± 23.0 µm, and the encapsulation efficiency was 34.07 ± 1.76%. Encapsulated NK cells exhibited robust proliferation and tumour-killing capabilities under normoxia and hypoxia. Furthermore, encapsulation provided a protective shield against cell viability under hypoxia. Importantly, tumour-killing cytotoxicity through cytokines upregulation such as granzyme B and interferon-gamma was preserved under hypoxia. CONCLUSION: The encapsulation of NK cells not only safeguards their viability but also reinforces anticancer capacity, countering the inhibition of activation induced by hypoxia.

Preparation of Controlled Multicompartmental Gel Microcarriers Based on Aqueous Two-Phase Emulsions for 3D Partitioned Cell Coculture In Vitro.

A facile method was proposed for preparing controllable multicompartment gel microcarriers using an aqueous two-phase emulsion system. By leveraging the density difference between the upper polyethylene glycol solution and the lower dextran-calcium chloride (CaCl2) solution in the collection solution and the high viscosity of the lower solution, controllable fusion of core-shell droplets made by coextrusion devices was achieved at the water/water (w/w) interface to fabricate microcarriers with separated core compartments. By adjusting the sodium alginate concentration, collected solution composition, and number of fused liquid droplets, the pore size, shape, and number of compartments could be controlled. Caco-2 and HepG2 cells were encapsulated in different compartments to establish gut-liver coculture models, exhibiting higher viability and proliferation compared to monoculture models. Notably, significant differences in cytokine expression and functional proteins were observed between the coculture and monoculture models. This method provides new possibilities for preparing complex and functional three-dimensional coculture materials.

Decoupling Charge and Side Chain Effects in Hierarchical Organization of Cationic PFX Peptide and Alginate.

We have successfully created self-assembled membranes by combining positively charged (Pro-X-(Phe-X)5-Pro) PFX peptides with negatively charged alginate. These PFX/alginate membranes were formed by three different peptides that contain either X = Arginine (R), Histidine (H), or Ornithine (O) as their charged amino acid. The assemblies were compared to membranes that were previously reported by us composed of X = lysine (K). This study enabled us to elucidate the impact of amino acids' specific interactions on membrane formation. SEM, SAXS, and cryo-TEM measurements show that although K, R, H, and O may have a similar net charge, the specific traits of the charged amino acid is an essential factor in determining the hierarchical structure of alginate/PFX self-assembled membranes.

Remendable Cross-Linked Alginate/Gelatin Hydrogels Incorporating Nanofibers for Wound Repair and Regeneration.

Wound dressings made from natural-derived polymers are highly valued for their biocompatibility, biodegradability, and biofunctionality. However, natural polymer-based hydrogels can come with their own set of limitations, such as low mechanical strength, limited cell affinity, and the potential cytotoxicity of cross-linkers, which delineate the boundaries of their usage and hamper their practical application. To overcome the limitation of natural-derived polymers, this study utilized a mixture of oxidized alginate and gelatin with 5 mg/mL polycaprolactone (PCL):gelatin nanofiber fragments at a ratio of 7:3 (OGN-7) to develop a hydrogel composite wound dressing that can be injected and has the ability to be remended. The in situ formation of the remendable hydrogel is facilitated by dual cross-linking of oxidized alginate chains with gelatin and PCL/gelatin nanofibers through Schiff-base mechanisms, supported by the physical integration of nanofibers, thereby obviating the need for additional cross-linking agents. Furthermore, OGN-7 exhibits increased stiffness (γ = 79.4-316.3%), reduced gelation time (543 ± 5 to 475 ± 5 s), improved remendability of the hydrogel, and excellent biocompatibility. Notably, OGN-7 achieves full fusion within 1 h of incubation and maintains structural integrity under external stress, effectively overcoming the inherent mechanical weaknesses of natural polymer-based dressings and enhancing biofunctionality. The therapeutic efficacy of OGN-7 was validated through a full-thickness in vivo wound healing analysis, which demonstrated that OGN-7 significantly accelerates wound closure compared to alginate-based dressings and control groups. Histological analysis further revealed that re-epithelialization and collagen deposition were markedly enhanced in the regenerating skin of the OGN-7 group, confirming the superior therapeutic performance of OGN-7. In summary, OGN-7 optimized the synergistic effects of natural polymers, which enhances their collective functionality as a wound dressing and expands their utility across diverse biomedical applications.

Layer-over-Layer Electrostatic Self-Assembly of Bioresourced Compounds in Thermoreversible Polylactide Gels as an Effective Approach to Enhance the Flame Retardancy of Aerogels.

Polylactide is a high potential polymer that can satisfy the growing demand for sustainable and lightweight materials in construction, packaging, and structural applications. However, their high flammability poses a serious concern. Herein, with the aid of solvent exchange and noncovalent interactions, poly(l-lactide) (PLLA) thermoreversible gel was modified with sodium alginate (SA), chitosan (CS), and phytic acid (PA) via a layer-over-layer approach. Freeze-drying of the modified hydrogel furnished a highly flame retardant aerogel with shape stability and no shrinkage. The modified PLLA aerogel (PLLA@SA@CS@PA) exhibited self-extinguishment of flame, the highest limiting oxygen index of any porous polylactide (∼32%), and a tremendous reduction in flammability parameters such as the heat release rate, heat release capacity, total heat release, etc. A comprehensive mechanism of flame retardancy was proposed. This work provides a sustainable strategy for the flame retardant modification of semicrystalline polymer-based aerogels and is expected to expand their practical applications in various industrial sectors.

Integration of N- and P- elements in sodium alginate aerogels for efficient flame retardant and thermal insulating properties.

In the field of building energy conservation, the development of biodegradable biomass aerogels with excellent mechanical performance, flame retardancy and thermal insulation properties is of particular importance. Here, a directional freeze-drying method was used for fabricating composite sodium alginate (SA) aerogels containing functionalized ammonium polyphosphate (APP) flame retardant. In particular, APP was coated with melamine (MEL) and phytic acid (PA) by a supramolecular assembly process. Through optimizing the flame retardant addition, the SA-20 AMP sample exhibited excellent flame retardant and thermal insulation properties, with the limiting oxygen index of 38.2 % and the UL-94 rating of V-0. Such aerogels with anisotropic morphology demonstrated a low thermal conductivity of 0.0288 (W/m·K) in the radial direction (perpendicular to the lamellar structure). In addition, as-obtained aerogels displayed remarkable water stability and mechanical properties, indicating significant potential for practical applications.

Design, preparation, and performance of different adsorbents based on carboxymethyl chitosan/sodium alginate hydrogel beads for selective adsorption of Cadmium (II) and Chromium (III) metal ions.

Developing cost-effective and efficient adsorbents for heavy metals in multicomponent systems is a challenge that needs to be resolved to meet the challenges of wastewater treatment technology. Two adsorbents were synthesized, characterized, and investigated for the removal of Cd2+ and Cr3+ as model heavy metals in their single and binary solutions. The first adsorbent (ACZ) was a nanocomposite formed of O-Carboxymethyl chitosan, sodium alginate, and zeolite. While, the other (ACL) contained ZnFe layered double hydroxides instead of the zeolite phase. Adsorbents were characterized using XRD, FTIR, SEM, and swelling degree analysis. For single heavy metal adsorption isotherms, data for both adsorbents was best fitted and indicated a multilayer adsorption nature. For binary adsorption, Langmuir model with interacting parameters showed the best results compared to other models for both pollutants. For single system, Avrami model was found to be the best model representing the adsorption kinetics data, which indicates that the mechanism of adsorption follows multiple kinetic orders that may change during duration of adsorption process. Numerous interaction mechanisms can occur between the heavy metals and functional groups in the synthesized hydrogels such as NH2, COOH, and OH groups leading to efficient adsorption of metal ions.

Fabrication of a self-healing hydrogel with antibacterial activity using host-guest interactions between dopamine-modified alginate and ß-cyclodextrin dimer.

Self-healing hydrogels possess an ability to recover their functionality after experiencing damage by regenerating cross-links. The main challenge in making self-healing hydrogels based on host-guest (HG) interactions is their limited mechanical strength, which can be solved using beta-cyclodextrin dimers (ß-CDsD). Here, ß-CDsD as a host cross-linker was used to increase the mechanical property of the HG interactions. Alginate with acceptable biocompatibility was modified by dopamine (ALG-DOP) and employed as a guest polymer. Self-healing hydrogel was developed between them, and Ag nanoparticles were added to create an antibacterial activity. Dopamine with appropriate size and suitable adhesiveness established HG interactions with ß-CDsD, and cells were able to grow well on hydrogel. This hydrogel showed an impressive self-healing capability <5 min. These hydrogels revealed a respectable porosity from 15 to 55 µm essential for exchanging the substances required for cell growth and cell waste elimination. Biocompatibility was investigated against NIH 3 T3 fibroblasts cells, and the results showed that the cells grew well. The in vitro release of curcumin from the hydrogel was examined in PBS at pH of 7.4. The hydrogel can be a perfect candidate for controlled drug release, and wound-dressing due to self-healing property, antibacterial activity, adhesion, and biocompatibility.

Bio-based melamine formaldehyde resins for flame-retardant polyurethane foams.

The polyurethane (PU) foams can be functionally tailored by modifying the formulation with different additives. One such additive is melamine (MA) formaldehyde resin for improving their flame-retardant properties. In this work, the glycerol-modified (GMF), sodium alginate (SGMF)- and lignosulfonate-modified melamine formaldehyde (LGMF) were prepared and used as flame retardants reacting with isocyanate to prepare the corresponding rigid polyurethane foams (GMF-PU, SGMF-PU and LGMF-PU). The thermomechanical properties and flame-retardant properties of the foams were characterized. The results showed that the specific compression strength of GMF-PU, SGMF-PU and LGMF-PU increased substantially compared to the foams from physical addition of MA, sodium alginate and lignosulfonate, all of which were greater than that of the foam without any flame retardant (PPU). Meanwhile, the cell wall of the foam pores became thicker and the closed pore ratio increased. The sodium alginate and lignosulfonate played a key role in enhancing foam thermal stability. The limiting oxygen index values and cone calorimetry results indicated the flame-retardant efficiency of GMF-PU, SGMF-PU and LGMF-PU was significantly enhanced relative to PPU. Meanwhile, the heat and smoke release results indicated sodium alginate and lignosulfonate could reduce the amount of smoke generation to different degrees during the combustion of the foam.