Incorporation of dumbbell-shaped and Y-shaped cross-linkers in adjustable pullulan/polydopamine hydrogels for selective adsorption of cationic dyes.

Hydrogel adsorbents have attracted considerable attention due to their sludge minimization, good water permeability and renewable performance. Here, a promising strategy for the one-step preparation of pullulan/polydopamine hybird hydrogels (PPGels) was presented. Dumbbell-shaped cross-linker neopentyl glycol diglycidyl ether (NGDE, 2 arms) and Y-shaped cross-linker trimethylolpropane triglycidyl ether (TTE, 3 arms) were selected to study the relationship between cross-linker structure and hydrogel performances. The NGDE possessing less molecular repulsive force and higher reactivity demonstrated more effective cross-linking with the pullulan, which leaded to a decrease in pore size of the hydrogel. Meanwhile, the introduction of polydopamine significantly enhanced the adsorption ability and gave the resulting hybrid gel the specific selectivity toward cationic dyes (96 mg/g for crystal violet, 25.8 mg/g for methylene blue and barely not adsorption for azophloxine). Our data suggested that the electrostatic interaction played a vital role in the dye adsorption process, and the adsorption data could be explained by pseudo-second-order model and Langmuir isotherm model. Furthermore, the obtained PPGel could be easily separated after adsorption. This study describes the relationship between cross-linker structure and properties of pullulan/polydopamine hybrid gels, which provides a new strategy to create polysaccharide-based adsorbents for wastewater remediation.

Salecan-Based pH-Sensitive Hydrogels for Insulin Delivery.

Stimuli-responsive polymeric hydrogels are promising and appealing delivery vehicles for protein/peptide drugs and have made protein/peptide delivery with both dosage- and spatiotemporal-controlled manners possible. Here a series of new Salecan-based pH-sensitive hydrogels were fabricated for controlled insulin delivery via the graft copolymerization reaction between Salecan and 2-acrylamido-2-methyl-1-propanesulfonic acid. In this study, on one hand, Salecan played a key role in modifying the structure and the pore size of the developing hydrogel. On the other hand, Salecan tuned the water content and the water release rate of the obtained hydrogel, leading to a controllable release rate of the insulin. More importantly, in vitro release experiments validated that the release of insulin from this intelligent system could be also tailored by the environmental pH of the release medium. For SGA2, the amount of encapsulated insulin released at gastric conditions (pH 1.2) was relatively low (about 26.1 wt % in 24 h), while that released at intestinal conditions (pH 7.4) increased significantly (over 50 wt % in 6 h). Furthermore, toxicity assays demonstrated that the designed hydrogel carriers were biocompatible. These characteristics make the Salecan-based hydrogel a promising candidate for protein/peptide drug delivery device.

Recent progress in magnetic polydopamine composites for pollutant removal in wastewater treatment.

Various water pollution issues pose a significant threat to human water safety. Magnetic polydopamine composites (MPCs), which can be separated by magnetic fields after the adsorption process, exhibit outstanding adsorption capacity and heterogeneous catalytic properties, making them promising materials for water treatment applications. In particular, by modifying the polydopamine (PDA) coating, MPCs can acquire enhanced high reactivity, antibacterial properties, and biocompatibility. This also provides an attractive platform for further fabrication of hybrid materials with specific adsorption, catalytic, antibacterial, and water-oil separation capabilities. To systematically provide the background knowledge and recent research advances in MPCs, this paper presents a critical review of MPCs for water treatment in terms of both structure and mechanisms of effect in applications. Firstly, the impact of different PDA positions within the composite structure is investigated to summarize the optimization of properties contributed by PDA when acting as the shell, core, or bridge. The roles of various secondary modifications of magnetic materials by PDA in addressing water pollution problems are explored. It is anticipated that this work will be a stimulus for further research and development of magnetic composite materials with real-world application potential.

Injectable conductive hydrogel remodeling microenvironment and mimicking neuroelectric signal transmission after spinal cord injury.

Severe spinal cord injury (SCI) leads to dysregulated neuroinflammation and cell apoptosis, resulting in axonal die-back and the loss of neuroelectric signal transmission. While biocompatible hydrogels are commonly used in SCI repair, they lack the capacity to support neuroelectric transmission. To overcome this limitation, we developed an injectable silk fibroin/ionic liquid (SFMA@IL) conductive hydrogel to assist neuroelectric signal transmission after SCI in this study. The hydrogel can form rapidly in situ under ultraviolet (UV) light. The mechanical supporting and neuro-regenerating properties are provided by silk fibroin (SF), while the conductive capability is provided by the designed ionic liquid (IL). SFMA@IL showed attractive features for SCI repair, such as anti-swelling, conductivity, and injectability. In vivo, SFMA@IL hydrogel used in rats with complete transection injuries was found to remodel the microenvironment, reduce inflammation, and facilitate neuro-fiber outgrowth. The hydrogel also led to a notable decrease in cell apoptosis and the achievement of scar-free wound healing, which saved 45.6 ± 10.8 % of spinal cord tissue in SFMA@IL grafting. Electrophysiological studies in rats with complete transection SCI confirmed SFMA@IL's ability to support sensory neuroelectric transmission, providing strong evidence for its signal transmission function. These findings provide new insights for the development of effective SCI treatments.

UV-assisted ultrafast construction of robust Fe3O4/polydopamine/Ag Fenton-like catalysts for highly efficient micropollutant decomposition.

Fenton-like catalysts represent a family of promising materials to degrade micropollutants from contaminated water. However, the practical applications of Fenton-like catalysts are mainly limited by low catalytic degradation efficiency and stability. Herein, for the first time, rapid fabrication of Ag-decorated Fe3O4/polydopamine (FPA) microspheres was achieved via the help of UV irradiation, and the designed FPA microspheres were employed as Fenton-like catalysts to degrade micropollutants. Results showed that UV irradiation could activate the generation of the polydopamine shell and accelerate the Ag deposition, which played a crucial role in the rapid synthesis of highly active and stable FPA catalysts. Relative to reported catalysts, these FPA microspheres exhibited outstanding catalytic degradation performance, achieving 94.38% removal of tetracycline within 60 min. This work will provide a convenient strategy in the sustainable and efficient purification of wastewater to improve the quality of human life.

Polydopamine-mediated modification of ZIF-8 onto magnetic nanoparticles for enhanced tetracycline adsorption from wastewater.

Magnetic nanoparticle materials which could be used to remove tetracycline were confined seriously due to their poor stability and unsatisfactory reusability. Here, we facilely prepared novel zeolitic imidazolate framework-8 (ZIF-8) functionalized magnetic nanoparticles (Fe3O4@PDA-ZIF-8) adsorbent utilizing polydopamine as a bond to establish a connection between zeolitic imidazolate framework-8 and Fe3O4, which could improve the stability of magnetic nanoparticles and enhance the tetracycline adsorption capacity simultaneously. The prepared nanocomposites were characterized and their TC adsorption abilities under various experiment conditions (contact time, TC initial concentration and pH values) were also investigated. Experimental results proved that the prepared adsorbent showed superior TC adsorption capacities (92.01 mg/g at pH = 7). Further, the adsorption mechanisms were comprehensively studied and the prepared adsorbent showed satisfactory stability and reusability during the cycle experiment. Altogether, our findings provided a feasible way to design and construct functional magnetic MOF materials for enhancing tetracycline adsorption from wastewater.

Fenton-like catalyst Fe3O4@polydopamine-MnO2 for enhancing removal of methylene blue in wastewater.

Fenton technology has been proven an effective way to remove dyes from wastewater. However, the demanding pH of reaction condition restricted its wide application. In this study, we report a novel Fenton-like catalyst (Fe3O4@PDA-MnO2) facilely synthesized by polydopamine (PDA) coating and MnO2 depositing onto the surface of Fe3O4 nanoparticles. This method for preparing magnetic Fe3O4@PDA-MnO2 catalyst could avoid the agglomeration of MnO2 nanoparticles and make the catalyst collect easily from the solution. The resultant Fe3O4@PDA-MnO2 nanoparticles possess core-shell nanostructure. Fe3O4@PDA-MnO2 catalyst could cooperate with hydrogen peroxide to form a Fenton-like reagent for the removal of methylene blue (MB) and performed excellent catalytic activities towards MB, including high degradation efficiency of 97.36% after 240 min. Besides, Fe3O4@PDA-MnO2 can retain excellent reusability after 5 using-cycles. More importantly, the catalyst can be used in a wide pH range from 2 to 12 in Fenton systems, demonstrating that the degradation process is independent on pH which is different from most reported studies. Also, Fe3O4@PDA-MnO2 could still keep more than 75% removal efficiency of MB in industrial wastewater treatment application. Therefore, the synthesized Fe3O4@PDA-MnO2 would be a promising device for the removal of dyes from wastewater.

Synthesis and characterization of a multi-sensitive polysaccharide hydrogel for drug delivery.

Salecan is a novel water soluble polysaccharide produced by a salt-tolerant strain Agrobacterium sp. ZX09. Poly(dimethylaminoethyl methacrylate) (PDMAEMA) is a pH, thermo, and ionic strength multi-sensitive polymer with anti-bacterial property. Here, we report a semi-interpenetrating polymer network (semi-IPN) hydrogel based on salecan and PDMAEMA. The obtained hydrogel is simultaneous sensitive to pH, ionic strength and temperature: the swelling ratio maximizes at pH 1.2 and shrinks at pH value greater than 3; besides, water content of the hydrogel decreases as the ionic strength increases; in terms of temperature, the hydrogel swells/deswells at temperatures below/above 40°C. Cytotoxicity test shows the hydrogel is non-cytotoxic to COS-7 cells. Protein drug insulin was selected as model drug to test the in vitro release behavior of the hydrogel. Results show the release rate increases with the swelling ratio of the hydrogel. In addition, when the temperature is higher than the lower critical solution temperature (LCST) of PDMAEMA, the hydrogel shrinks to extrude more drug molecules. Moreover, the release rate and release amount were higher in acid condition (pH 1.2) than at pH 7.4. In summary, this polysaccharide hydrogel is a promising material for drug delivery.

Preparation of a Salecan/poly(2-acrylamido-2-methylpropanosulfonic acid-co-[2-(methacryloxy)ethyl]trimethylammonium chloride) Semi-IPN Hydrogel for Drug Delivery.

Salecan is a water-soluble bacterial polysaccharide consisting of glucopyranosyl units linked by α-1,3 and ß-1,3 glycosidic bonds. salecan is suitable for the development of hydrogels for biomedical applications, given its outstanding physicochemical and biological profiles. In this study we designed a new semi-interpenetrating polymer network hydrogel that introduces the salecan polysaccharide into a stimuli-responsive poly(2-acrylamido-2-methylpropanosulfonic acid-co-[2-(methacryloxy)ethyl]trimethylammonium chloride) (PAM) hydrogel matrix for controlled insulin release. We found that salecan not only tunes the structure and pore size of the PAM hydrogels, but also endows them with adjustable water release rates. More importantly, in vitro drug loading/release assays demonstrated that insulin is efficiently loaded into the resulting hydrogels and can be released in an on-demand manner by controlling the pH and salecan dose. Furthermore, cell viability and cell adhesion experiments verified the cell compatibility of these hydrogel carriers. Together, these results make salecan-incorporated PAM hydrogels promising materials for drug delivery.

Synthesis and characterization of a novel cationic hydrogel base on salecan-g-PMAPTAC.

Salecan is a biological macromolecular and biocompatible polysaccharide that has been investigated for recent years. Herein, we report a novel cationic hydrogel fabricated by graft-polymerizing 3-(methacryloylamino)propyl-trimethylammonium chloride (MAPTAC) onto salecan chains. The obtained hydrogels were transparent, solid-elastic, macro-porous, ion-sensitive, and non-cytotoxic. The swelling ratios increased with salecan content, while mechanical strength does the opposite. Moreover, drug delivery test was studied as a potential application. Diclofenac sodium (DS) and insulin were selected as model drugs. Interestingly, in drug loading process, DS molecules exhibited highly affinity to these cationic hydrogels. Almost all the DS molecules in loading solution were absorbed and spread into the hydrogel. For drug release profiles, insulin-loaded hydrogel showed an initial rapid release and a sustained release. As a comparison, DS-loaded hydrogel exhibited a more sustained release profile. Results suggested salecan-g-PMAPTAC hydrogel could be a good candidate for anionic drug loading and delivery.