Ultra-absorbent hybrid hydrogel based on alginate and SiO2 microspheres: A high-water-content system for removal of methylene blue

Hydrogel-based platforms for site-specific doxorubicin release in cancer therapy

Hydrogels are promising candidates for the delivery of therapeutics in the treatment of human cancers. Regarding to the biocomaptiiblity, high drug and encapsulation efficacy and adjustable physico-chemical features, the hydrogels have been widely utilized for the delivery of chemotherapy drugs. Doxorubicin (DOX) is one of the most common chemotherapy drugs used in cancer therapy through impairing topoisomerase II function and increasing oxidative damage. However, the tumor cells have developed resistance into DOX-mediated cytotoxic impacts, requiring the delivery systems to increase internalization and anti-cancer activity of this drug. The hydrogels can deliver DOX in a sustained manner to maximize its anti-cancer activity, improving cancer elimination and reduction in side effects and drug resistance. The natural-based hydrogels such as chitosan, alginate and gelatin hydrogels have shown favourable biocompatibility and degradability in DOX delivery for tumor suppression. The hydrogels are able to co-deliver DOX with other drugs or genes to enhance drug sensitivity and mediate polychemotherapy, synergistically suppressing cancer progression. The incorporation of nanoparticles in the structure of hydrogels can improve the sustained release of DOX and enhancing intracellular internalization, accelerating DOX's cytotoxicity. Furthermore, the stimuli-responsive hydrogels including pH-, redox- and thermo-sensitive platforms are able to improve the specific release of DOX at the tumor site. The DOX-loaded hydrogels can be further employed in the clinic for the treatment of cancer patients and improving efficacy of chemotherapy.

Water-Adaptive Microcapsules with a Brittle-Ductile-Brittle Transition Based on an O/W/O Emulsion for the Self-Healing of Cementitious Materials

Cementitious materials inevitably develop cracks, posing a serious threat to the long-term security of infrastructure, especially in the complex underground environment of cementing engineering. Microcapsules are facing the problem of encapsulated structure damage during the mixing and breaking difficultly during self-healing when applied in cementitious materials, resulting in the decline of self-healing efficiency. Herein, the calcium alginate water-adaptive microcapsules (CaAlg-NS/E-51) were prepared via an O/W/O emulsion, and the water adaptability of the shell was applied to achieve a rapid brittle-ductile transition by absorbing water. The water adaptability of the microcapsule is conducive to resisting shear stress during stirring due to the decreased elastic modulus and the increased ductility of the shell when it absorbs water. Meanwhile, the water-bearing shell loses water and becomes brittle during dry curing, making it prone to fracture when self-healing. In the self-healing measurement, the self-healing efficiency of cementitious specimens with microcapsules absorbing water for 10 min improved by 234.9 and 60.0% at 1 and 7 days, respectively, compared with those containing dry microcapsules, owing to the water adaptability of the shell.

Alginate-based porous polyHIPE for removal of single and multi-dye mixtures: Competitive isotherm and molecular docking studies

A novel hydrophilic porous alginate-based polyHIPE (AGA) was synthesized via an oil-in-water emulsion templating approach. AGA was used as an adsorbent for removing methylene blue (MB) dye in single- and multi-dye systems. BET, SEM, FTIR, XRD, and TEM were used to characterize AGA to elucidate its morphology, composition and physicochemical properties. According to the results, 1.25 g/L AGA adsorbed 99 % of 10 mg/L MB in 3 h in a single-dye system. The removal efficiency decreased to 97.2 % in the presence of 10 mg/L Cu2+ ions and 40.2 % when the solution salinity increased to 70 %. In a single-dye system, the experimental data do not match well with the Freundlich isotherm, pseudo-first order, and the Elovich kinetic model, however, in a multi-dye system, it fit well with both extended Langmuir and the Sheindorf-Rebhun-Sheintuch. Notably, AGA removed 66.87 mg/g in a dye solution containing only MB, whereas 50.14-60.01 mg/g adsorption of MB was accomplished in a multiple-dye system. According to the molecular docking analysis, the dye removal process involved chemical bonds between the functional groups of AGA and the dye molecules, hydrogen bonds, hydrophobic and electrostatic interactions. The overall binding score of MB decreased from -26.9 kcal/mol in a single-dye system to -18.3 kcal/mol in a ternary system.

Room temperature fabrication of cobalt mullite for the snappy adsorption of cationic and anionic dyes

Cobalt mullite adsorbent for the robust adsorption performance toward Victoria Blue (VB) and Metanil Yellow (MY) is fabricated by the sol-gel method at room temperature using dipropylamine as a structure-directing agent. The synthesized adsorbent is characterized by XRD, FT-IR, and HRTEM. From these analyses, it is found that dipropylamine binds with the alumina and cobalt oxide, which makes it into tetrahedral to octahedral form. This interaction causes the formation of cobalt mullite. It is observed that trigonal alumina and orthorhombic cobalt mullite are interlinked to form a hybrid network. The special feature of adopting this adsorbent for the adsorption of VB and MY is that it has a large amount of Brønsted acid site because of the octahedral coordination of Al and Co. The large availability of acid sites in the framework and hybridization of two different network systems favors robust adsorption. The rate of adsorption (K₂ = 0.00402 g/mg.min for VB and K₂ = 0.004 g/mg.min for MY) and adsorption capacity (Q_e = 102.041 mg/g for VB and Q_e = 19.0406 mg/g for MY) are greater for VB than MY. This may be due to the more steric factor involved in MY than VB. Thermodynamic parameter indicated that the adsorption of VB and MY is spontaneous, endothermic, and increased randomness in the adsorbent-adsorbate interface. The results from the enthalpy value (ΔH° = 65.43 kJ/mol for VB and ΔH° = 44.729 kJ/mol for MY) revealed that the chemisorption is involved in the adsorption process.

Anti-swellable cellulose hydrogel for underwater sensing

Underwater sensing is of great significance in ocean exploration by divers to monitor their movements and keep in touch with the shore. However, unique sensors are required to apply in the marine environment that is quite different from the land circumstance. Herein, we reported a cellulose-skeleton-based composite hydrogel that is constraint to expand underwater under the effect of hydrogen bonds (H-bonds) and features advantages of high swelling resistance, structural durability, mechanical robustness, medium flexibility, high gauge factor (2.33) and long-term stability in water as a highly efficient wearable underwater sensor. This cellulose-based anti-swellable underwater hydrogel sensor showed tremendous potentials in underwater sensing applications for posture monitoring, communication, and marine biological research, etc.

Injectable Networks Based on a Hybrid Synthetic/Natural Polymer Gel and Self-Assembling Peptides Functioning as Reinforcing Fillers

Double network (DN) hydrogels composed of self-assembling low-molecular-weight gelators and a hybrid polymer network are of particular interest for many emerging biomedical applications, such as tissue regeneration and drug delivery. The major benefits of these structures are their distinct mechanical properties as well as their ability to mimic the hierarchical features of the extracellular matrix. Herein, we describe a hybrid synthetic/natural polymer gel that acts as the initial network based on sodium alginate and a copolymer, namely poly(itaconic anhydride-co-3,9-divinyl-2,4,8,10-tetraoxaspiro (5,5) undecane). The addition of amino acids and peptide-derived hydrogelators, such as Fmoc-Lys-Fmoc-OH and Fmoc-Gly-Gly-Gly-OH, to the already-made network gives rise to DNs crosslinked via non-covalent interactions. Fourier transform infrared spectroscopy (FTIR) and thermal analysis confirmed the formation of the DN and highlighted the interactions between the two component networks. Swelling studies revealed that the materials have an excellent water absorption capacity and can be classified as superabsorbent gels. The rheological properties were systematically investigated in response to different variables and showed that the prepared materials present injectability and a self-healing ability. SEM analysis revealed a morphology consisting of a highly porous and interconnected fibrous network. Finally, the biocompatibility was evaluated using the MTT assay on dermal fibroblasts, and the results indicated that the new structures are non-toxic and potentially useful for biomedical applications.

Recent developments of polysaccharide based superabsorbent nanocomposite for organic dye contamination removal from wastewater - A review

One of the main problems with water pollution is dye contamination of rivers, industrial effluents, and water sources. It has endangered the world's sources of drinking water. Several remediation strategies have been carefully developed and tested to minimize this ominous picture. Due to their appealing practical and financial benefits, adsorption methods in particular are often listed as one of the most popular solutions to remediate dye-contaminated water. Biopolymer-based hydrogel nanocomposites are a cutting-edge class of materials with a wide range of applications that are effective in removing organic dyes from the environment. Since the incorporation of various materials into hydrogel matrices generated composite materials with distinct characteristics, these unique materials were often alluded to as ideal adsorbents. The fundamental emphasis of the conceptual and critical review of the literature in this research is the significant potential of hydrogel nanocomposites (HNCs) to remediate dye-contaminated water (especially for articles from the previous five years). The review also provides knowledge for the development of biopolymer-based HNCs, prospects, and opportunities for future research. It is also focused on optimum conditions for dye adsorption processes along with their adsorption kinetics and isotherm models. In summary, the information gained in this review research may contribute to a strengthened scientific rationale for the practical and efficient application of these novel adsorbent materials.

Cold plasma-assisted regeneration of biochar for dye adsorption

Environmental remedies, including adsorption-based water purification, are now being asked to meet the requirement for a low-carbon circular economy requiring low energy and low material consumption. In this regard, we tested the possibility of regenerating adsorbents via cold plasma (CP) treatment for less use of adsorbents and no washing solution. In the adsorption of methylene blue (MB) using carbonized rice husk (CRH) and five successive regeneration cycles by CP treatment, the removal efficiencies were maintained at a moderate level (∼70% of the initial performance), unlike five consecutive adsorption without CP treatment (∼9-13% of the initial performance). The regeneration of CRH by CP treatment was also double-checked by the FESEM, EDS, BET, FTIR, XPS, and surface zeta potential measurements. The successfully recovered adsorption capability is related to the remediation of adsorption sites. It is also worth noting that the required power consumption for recycling by CP treatment was about 6.4 times lower than carbonizing new rice husks. This work provides insights into recovering adsorbents using CP without rigorous, costly, and energy-intensive processes.

Influence of quince seed mucilage-alginate composite hydrogel coatings on quality of fresh walnut kernels during refrigerated storage

The presence of high unsaturated fat content and polyphenols results in the short storage life of fresh walnut kernels. For prolonging their shelf life, edible coatings incorporated with antimicrobial compounds can be used as a tool. Quince seed mucilage was identified as a novel green biomaterial to be explored as a coating substance. Quince seed mucilage and sodium alginate were mixed in five different proportions of 100:0 (QAH1), 80:20 (QAH2), 60:40 (QAH3), 40:60 (QAH4), and 20:80 (QAH5) and the resultant composite hydrogels were studied for different physical properties. These composite hydrogels incorporated with vanillin were coated on fresh walnut kernels while uncoated samples served as control. Composite hydrogel coatings with a higher proportion of QSM retained a higher whiteness index, lightness (L*), DPPH radical scavenging capacity, total phenolic content, and overall acceptability values in walnut kernels during the entire storage period of 35 days. QAH1 showed the lowest weight loss percentage, lipid oxidation, and yeast and mold counts while the control sample showed the highest (P < 0.05) values. The results concluded that quince-based composite hydrogel coatings were effective in retention of quality and prevention of degradation of fresh walnut kernels during the storage.

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Chemically crosslinked guar gum hydrogels: An investigation on the water transport and its relationship with hydrocortisone release

In this work, we describe the synthesis, the characterization, and the potential application of a pH-responsive guar gum-based hydrogel. The polysaccharide produced permanent hydrogels with improved biocompatibility. In this work, we report the chemical modification of guar gum (with glycidyl methacrylate) and its use, as the main constituent, in obtaining chemically cross-linked hydrogels. The morphology, swelling properties, and cytotoxicity of the resulting materials were studied in-depth. The hydrogels showed to be pH-responsive, and non-toxic being safe to use it as a biomaterial. In addition, we tested the potential of this one as a drug carrier. Herein, we have chosen hydrocortisone (HCS) as a drug model. The mechanism of HCS release changed as a function of pH, owing to different responses in each medium. Our results indicate that the guar gum hydrogels have great potential to be used, with safety, as a drug carrier.

Injectable and biocompatible alginate-derived porous hydrogels cross-linked by IEDDA click chemistry for reduction-responsive drug release application

In this work, novel injectable and reduction-responsive hydrogels were successfully prepared via inverse electron demand Diels-Alder reaction between alginate-norbornene and a water-soluble PEG based disulfide cross-linker. The reduction-responsive cross-linker was designed to contain a PEG chain within two disulfide linkages, and two terminal tetrazine groups. The resulting hydrogels possessed high swelling ratios, porous morphology, excellent drug loading efficiency (~92%), and suitable mechanical properties. The drug release experiments demonstrated that the hydrogels released more than 90% of the encapsulated doxorubicin (DOX) in the presence of 10 mM glutathione while a minimal DOX release (<25%) was measured in physiological buffer (PBS, pH = 7.4) after 11 d. The cross-linker and hydrogels did not exhibit any apparent cytotoxicity to fibroblast cells. In contrast, DOX-loaded hydrogels induced anti-tumor activity against cancer cells. The injectable and reduction-responsive hydrogels hold great potential as a biomaterial for stimuli responsive drug delivery applications.

Highly efficient and selective adsorption of heavy metal ions by hydrazide-modified sodium alginate

In the present study, a new potential adsorbent for the separation and removal of heavy metal ions was prepared using hydrazide modification. Characterization of structural and chemical properties of the absorbent indicated the dialdehyde sodium alginate (DSA) grafted adipic acid dihydrazide (AAD) plays a crucial role. The adsorption process correlated well with Freundlich isotherm and pseudo-second-order kinetics models. Additionally, the adsorption capacities for Hg²⁺, Pb²⁺, Cd²⁺, and Cu²⁺ were 7.833, 2.036, 4.766, and 3.937 mmol g^-1, respectively. The thermodynamic parameter for the sorption demonstrated the process is endothermic and spontaneous. FT-IR and XPS analysis revealed the combination of chelation interactions and ion exchange between nitrogen, oxygen atoms and heavy metal ions. Moreover, after 10 times adsorption-desorption recycles, the adsorption efficiency of the adsorbent was slightly decreased. In conclusion, the as-prepared adsorbent has great potential in practical water pollution purification.

Cross-linked FeCl3-activated seaweed carbon/MCM-41/alginate hydrogel composite for effective biosorption of bisphenol A plasticizer and basic dye from aqueous solution

A FeCl₃-activated seaweed carbon/MCM-41/alginate hydrogel composite (ECAC/MCM-41/ ALG) cross-linked with calcium chloride (2% CaCl₂) was synthesized for the biosorption of bisphenol A (BPA) plasticizer and basic blue (BB) dye. Biosorption uptakes of BPA and BB were performed in a batch mode with varying solution pH from 3 to 11, initial sorbate concentration from 25 to 300 mg/L, reaction time from 0 to 10 h, and biosorption temperature from 30 to 50 °C. The maximum BPA and BB uptake mechanisms were fast, which occurred within contact times of 1 and 2 h with monolayer coverage capacities of 222.32 and 190.11 mg/g at 50 °C, respectively. Cyclic biosorption/desorption behavior was evaluated via an ethanol elution to evaluate the feasibility of the ECAC/MCM-41/ALG for long-term application. Results revealed the biosorption renewability for five cycles up to 80% of the newly synthesized hydrogel composite for the purification of industrial wastewater laden with emerging contaminants.

Magnetic methacrylated gelatin-g-polyelectrolyte for methylene blue sorption

The presence of organic dyes in wastewater is a problem of growing interest due to its effect on the environment and human health. The aim of this work was to obtain magnetic hydrogels of methacrylated gelatin-g-polyelectrolyte to be used for the removal of methylene blue (MB) used as a model contaminant dye. Grafted gelatins with two degrees of functionalization (48% and 76%) were obtained and subsequently crosslinked using 2-acrylamido-2-methyl-1-propansulfonic acid (AMPS) and sodium 4-vinylbenzenesulfonate (SSNa) monomers. Magnetic nanoparticles were formed by an in situ precipitation method to easily remove the hydrogel from the adsorption medium. Our data show that the hydrogel with a low degree of methacrylation displayed a high degree of swelling and decreased stiffness due to its less connected polymer network. MB adsorption experiments showed that neither the low degree of methacrylation nor the presence of the aromatic group in the PSSNa polyelectrolyte generated an increase in the adsorption capacity of the hydrogel. However, a significant increase in the adsorption capacity was observed when dry hydrogels were combined compared to that of previously swollen hydrogel. The experimental data were non-linearly fitted to the pseudo-first and pseudo-second order models and in both cases, the highest q_e values were obtained for the GelMA-HF/PAMPS and GelMA-LF/PAMPS hydrogels. The Freundlich isotherm model was the one with the best correlation with the data (r² > 0.9700). Higher k_f values were obtained for the GelMA-HF/PAMPS and GelMA-LF/PAMPS hydrogels at 20 °C. The results obtained from this study demonstrated that magnetic polyelectrolyte-grafted gelatins are an efficient option for the removal of contaminant dyes from aqueous solutions.

Magnetic methacrylated gelatin grafted with anionic polyelectrolytes hydrogels removes methylene blue efficiently and easily separate with a magnet.

Drug polarity effect over the controlled release in casein and chondroitin sulfate-based hydrogels

This study compared the controlled release of two drugs: vitamin-B12, and l-dopa from hydrogels based on 50% of casein (CAS, a protein), 50% of chondroitin sulfate (CS, a polysaccharide) and different amounts of SiO2. The results indicated that the incorporation of 5% of SiO2 to the materials, allowed the best organization, distribution, and diameter of the pores, which are responsible for ensuring a more controlled release. Also, the matrices were not efficient in releasing vitamin-B12, but it successfully released l-dopa. It happened because vitamin-B12 is highly hydrophilic, interacting more with the medium than with the CAS/CS matrix, while l-dopa is less polar than vitamin-B12, interacting more with the CAS/CS matrix. It is worth mentioning that all synthesized hydrogels were non-toxic to the cells as showed by the in vitro assay. This work also demonstrated the importance of evaluating drug delivery devices using drugs of different polarities before stating if they are efficient or not.

Strategies to Functionalize the Anionic Biopolymer Na-Alginate without Restricting Its Polyelectrolyte Properties

The natural anionic polyelectrolyte alginate and its derivatives are of particular interest for pharmaceutical and biomedical applications. Most interesting for such applications are alginate hydrogels, which can be processed into various shapes, self-standing or at surfaces. Increasing efforts are underway to functionalize the alginate macromolecules prior to hydrogel formation in order to overcome the shortcomings of purely ionically cross-linked alginate hydrogels that are hindering the progress of several sophisticated biomedical applications. Particularly promising are derivatives of alginate, which allow simultaneous ionic and covalent cross-linking to improve the physical properties and add biological activity to the hydrogel. This review will report recent progress in alginate modification and functionalization with special focus on synthesis procedures, which completely conserve the ionic functionality of the carboxyl groups along the backbone. Recent advances in analytical techniques and instrumentation supported the goal-directed modification and functionalization.

Processing and modification of hydrogel and its application in emerging contaminant adsorption and in catalyst immobilization: a review

Due to the wonderful property of hydrogels, they can provide a platform for a wide range of applications. Recently, there is a growing research interest in the development of potential hydrogel adsorbents in wastewater treatment due to their adsorption ability toward aqueous pollutants. It is important to prepare such a hydrogel that possesses appropriate robustness, adsorption capacity, and adsorption efficiency to meet the need of water treatment. In order to improve the property of hydrogels, much effort has been made by researchers to modify hydrogels, among which incorporating inorganic components into the polymeric networks is the most common method, which can reduce the product cost and simplify the preparation procedure. Not only can hydrogel be applied as adsorbent, but it also can be used as matrix for catalyst immobilization. In this review, the key advancement on the preparation and modification of hydrogels is discussed, with special emphasis on the introduction of inorganic materials into polymeric networks and consequential changes in the properties of mechanical strength, swelling, and adsorption. Besides, hydrogels used as adsorbents for removal of dyes and inorganic pollutants have been widely explored, but their use for adsorbing emerging contaminants from aqueous solution has not received much attention. Thus, this review is mainly focused on hydrogels' application in removing emerging contaminants by adsorption. Furthermore, hydrogels can be also applied in immobilizing catalysts, such as enzyme and photocatalyst, to remove pollutants completely and avoid secondary pollution, so their progress as catalyst matrix is overviewed.