Malic acid cross-linked chitosan based hydrogel for highly effective removal of chromium (VI) ions from aqueous environment

Novel ACS film for efficient dual adsorption of Cr(VI) and SDS: Mechanistic insights and practical applications

The current study introduces a novel ACS film as a dual-functional adsorbent for the efficient elimination of hexavalent chromium (Cr(VI)) and sodium dodecyl sulphate (SDS) from aqueous systems. Comprehensive batch experiments were directed, and the results were rigorously validated using Response Surface Methodology (RSM). The maximum adsorption capacity was found to be 467.14 and 244.47 mg g-1 for Cr(VI) and SDS, respectively. The adsorption of Cr(VI) followed the Freundlich isotherm model (R2 = 0.985), indicating multilayer adsorption, while SDS adhered to the Langmuir isotherm (R2 = 0.935), suggesting monolayer adsorption. Kinetic studies revealed that Cr(VI) adsorption was best defined by the Pseudo Second Order model (R2 = 0.994), whereas SDS adsorption conformed to the Pseudo First Order model (R2 = 0.975), elucidating distinct adsorption mechanisms. Thermodynamic analyses confirmed that the adsorption processes for both Cr(VI) and SDS were spontaneous and enthalpy-driven. The film performance was evaluated using real effluent samples from textile industries, demonstrating its practical applicability in complex matrices. Additionally, regeneration studies showed sustained adsorption efficiency across five cycles, highlighting the materials reusability and economic viability. This work emphasizes the potential of the ACS film as a versatile and sustainable material for addressing dual pollution challenges, paving the way for scalable applications in environmental remediation.

Efficacy of malic and tartaric acid in mitigation of cadmium stress in Spinacia oleracea L. via modulations in physiological and biochemical attributes

The increasing level of cadmium (Cd) contamination in soil due to anthropogenic actions is a significant problem. This problem not only harms the natural environment, but it also causes major harm to human health via the food chain. The use of chelating agent is a useful strategy to avoid heavy metal uptake and accumulation in plants. In this study, randomized design pot experiment was conducted to evaluate potential role of malic acid (MA) and tartaric acid (TA) foliar spray to mitigate Cd stress in Spinacia oleracea L plants. For Cd stress, S. oleracea plants were treated with CdCl2 solution (100 µM). For control, plants were given distilled water. One week after Cd stress, MA and TA foliar spray was employed at concentration of 100 and 150 µM for both. The results of this study revealed that Cd stress (100 µM) significantly reduced growth attributes, photosynthetic pigments and related parameters and gas exchange attributes. Cadmium stress also stimulated antioxidant defense mechanism in S. oleracea. Cd stressed plants had elevated levels of Cd metal ions in root and consumable parts (i.e. leaves) and caused severe oxidative damages in the form of increased lipid peroxidation and electrolytic leakage. MA and TA supplements at both low and high levels (100 and 150 µM) effectively reversed the devastating effects of Cd stress and improved growth, photosynthesis and defense related attributes of S. oleracea plants. These supplements also prevented excessive accumulation of Cd metal ions as indicated by lowered Cd metal contents in MA and TA treated plants. These findings demonstrated that MA and TA treatments can potentially reduce Cdl induced phytotoxicity in plants by reducing its uptake and enhancing photosynthesis and defense related parameters.

XG and CS-based self-assembled nanocomposite hydrogel embedding fluorescent NCQDs capable of detection and adsorptive removal of the polar MO and Cr(VI) pollutants

Aiming at dealing with organic and inorganic pollutants dissolved in aquatic environments, we introduce self-assembled fluorescent nanocomposite hydrogel based on a binary polysaccharide network (xanthan gum/chitosan) embedding nitrogen-doped carbon quantum dots not only as a hybrid solid optical sensor for detecting Cr(VI) ions but also to remove anionically charged contaminants Cr(VI) and methyl orange (MO) by acting as an adsorbent. This fluorescent nanocomposite achieved a detection limit of 0.29 μM when used to detect Cr(VI) and demonstrated a fluorescence quantum yield of 59.7 %. Several factors contributed to the effectiveness of the adsorption of Cr(VI) and MO in batch studies, including the solution pH, dosage of the adsorbent, temperature, initial contamination level, and contact time. Experimental results showed 456 mg/g maximum adsorption capacity at pH 4 for MO compared to 291 mg/g at pH 2 for Cr(VI) at 25 °C. In addition to conforming to Langmuir's model, Cr(VI) and MO's adsorption kinetics closely matched pseudo-second-order. Using thermodynamic parameters, the results indicate that Cr(VI) and MO adsorb spontaneously and exothermically. Recycling spent adsorbent for Cr(VI) and MO using NaOH at 0.1 M was possible; the respective adsorption efficiency remained at approximately 82.2 % and 83 % after the fifth regeneration cycle.

Green Synthesis of Silver Nanoparticles with Roasted Green Tea: Applications in Alginate-Gelatin Hydrogels for Bone Regeneration

The incorporation of silver nanoparticles (AgNPs) into alginate-gelatin (Alg-Gel) hydrogels can enhance the properties of these materials for bone regeneration applications, due to the antimicrobial properties of AgNPs and non-cytotoxic concentrations, osteoinductive properties, and regulation of stem cell proliferation and differentiation. Here, the hydrogel formulation included 2% (w/v) sodium alginate, 4 µg/mL AgNPs, and 2.5% (w/v) gelatin. AgNPs were synthesized using a 2% (w/v) aqueous extract of roasted green tea with silver nitrate. The aqueous extract of roasted green tea for AgNP synthesis was characterized using HPLC and UHPLC-ESI-QTOF-MS/MS, and antioxidant capacity was measured in Trolox equivalents (TE) from 4 to 20 nmol/well concentrations. Stem cells from human exfoliated deciduous tooth cells were used for differentiation assays including positive (SHEDs/hydrogel with AgNPs) and negative controls (hydrogel without AgNPs). FTIR was used for hydrogel chemical characterization. Statistical analysis (p < 0.05, ANOVA) confirmed significant findings. Roasted green tea extract contained caffeine (most abundant), (-)-Gallocatechin, gallic acid, and various catechins. XRD analysis revealed FCC structure, TEM showed quasispheroidal AgNPs (19.85 ± 3 nm), and UV-Vis indicated a plasmon surface of 418 nm. This integration of nanotechnology and biomaterials shows promise for addressing bone tissue loss in clinical and surgical settings.

Design and evaluation of fluorescent chitosan-starch hydrogel for drug delivery and sensing applications

Composite bio-based hydrogels have been obtaining a significant attention in recent years as one of the most promising drug delivery systems. In the present study, the preparation of composite chitosan-starch hydrogel using maleic acid as a cross-linker was optimized with the help of response surface methodology. The synthesized hydrogel was fluorescent owing to clustering of large number of functional groups. Different analytical techniques, including XRD, FTIR, SEM, XPS, fluorescence and BET were utilized to characterize the prepared hydrogel. XRD analysis confirmed the formation of non-crystalline hydrogel with random arrangement of macromolecular chains. The composite hydrogel exhibited good swelling percentage with pH sensitivity, hemocompatibility and degradability. BET analysis confirmed that the variation in concentration of crosslinker significantly influences the pore volume of the hydrogel. The synthesized composite chitosan-starch hydrogel was utilized as a prospective candidate for controlling drug release. Cefixime as a model drug was loaded onto the synthesized hydrogel utilizing the swelling diffusion method. SEM micrographs showed uniform distribution of drug molecules in the drug loaded hydrogel. In vitro drug release experiments indicated the swelling dependent drug release behaviour of chitosan-starch hydrogel with higher drug release at pH 7.4 (93.08 %) compared to pH 1.2 (67.85 %). The composite chitosan-starch hydrogel was able to prolong and control the drug release up to 12 h. The drug release from the hydrogel followed Korsmeyer-Peppas and Makoid-Banakar model with Fickian diffusion mechanism. Further, the composite hydrogel displayed excitation dependent fluorescence emission with most intense blue emission band at 425 nm with an excitation wavelength of 350 nm. The inclusion of cefixime drug in the hydrogel matrix significantly reduced the fluorescence intensity; the decrease was linearly correlated to the concentration of the drug. Moreover, the fluorescence emission the chitosan-starch hydrogel was found to be dependent upon pH. The synthesized hydrogel is expected to be a potential candidate for controlled drug release as well as for fluorescent sensing applications.

Chitosan/Poly(maleic acid-alt-vinyl acetate) Hydrogel Beads for the Removal of Cu2+ from Aqueous Solution

Covalent cross-linked hydrogels based on chitosan and poly(maleic acid-alt-vinyl acetate) were prepared as spherical beads. The structural modifications of the beads during the preparation steps (dropping in liquid nitrogen and lyophilization, thermal treatment, washing with water, and treatment with NaOH) were monitored by FT-IR spectroscopy. The hydrogel beads have a porous inner structure, as shown by SEM microscopy; moreover, they are stable in acidic and basic pH due to the covalent crosslinking. The swelling degree is strongly influenced by the pH since the beads possess ionizable amine and carboxylic groups. The binding capacity for Cu2+ ions was examined in batch mode as a function of sorbent composition, pH, contact time, and the initial concentration of Cu2+. The kinetic data were well-fitted with the pseudo-second-order kinetic, while the sorption equilibrium data were better fitted with Langmuir and Sips isotherms. The maximum equilibrium sorption capacity was higher for the beads obtained with a 3:1 molar ratio between the maleic copolymer and chitosan (142.4 mg Cu2+ g-1), compared with the beads obtained using a 1:1 molar ratio (103.7 mg Cu2+ g-1). The beads show a high degree of reusability since no notable decrease in the sorption capacity was observed after five consecutive sorption/desorption cycles.

A novel chitosan-glutamic acid membrane for multi-pollutant amputation: Investigational and RSM optimizations

The novel glutamic acid crosslinked chitosan membrane (CsG) was fabricated and tested for its adsorption capabilities for the removal of multiple pollutants like Cr (VI), cyanide, fluoride and diclofenac sodium from wastewater. This fabricated CsG membrane was characterized by various techniques like FT-IR, SEM, EDX and XRD, BET to assess its structural, compositional and morphological properties. The working parameters studied by batch experiments were solution pH, CsG dose, contact time, pollutant concentration and solution temperature. The CsG membrane exhibited maximum adsorption capacity of 410.7 mg/g, 310.2 mg/g, 14.3 mg/g, 132.7 mg/g for Cr (VI), cyanide, fluoride and diclofenac respectively. The validation of the operational parameters was performed by Response Surface Methodology (RSM). The experimental data fitted well with Langmuir isotherm model and followed pseudo second order kinetics for all the four targeted contaminants. The spontaneity of the process was checked by thermodynamics studies. The high partition coefficients of 7669 L/kg Cr(VI), 23,309 L/kg (CN-), 649 L/kg (F-) and 2613 L/kg (DFC) are the indicators of excellent attractive interaction between CsG membrane and target toxicants. The CsG membrane showed efficient regenerative adsorption properties up to 5 adsorption-desorption cycles. Overall, the developed novel CsG membrane promised as an effective material for the removal of multiple number of pollutants from water.

Chitosan based hybrid superabsorbent for controlled drug delivery application

In the present study, a hybrid chitosan-alginate superabsorbent is prepared using maleic acid as a cross-linker and acrylamide as a grafting agent using the free radical mechanism. The composite hydrogel shows good swelling capacity along with hemocompatibility and biocompatibility and hence it is utilized as a drug delivery device. The characterization techniques including x-ray diffraction, Fourier transform infrared, x-ray photoelectron spectroscopy, and thermal analysis indicate the successful synthesis of stable hydrogel with rich functionalities. Metformin hydrochloride is used as a model drug which is used to treat diabetes. The drug encapsulation is done using the swelling diffusion method after the synthesis of hydrogel. The release of metformin from the drug-loaded hydrogel at physiological pH highlights the role of non-covalent interactions between the drug and hydrogel. In vitro release studies of Metformin from the drug-loaded hydrogel show higher release profiles at intestinal pH (7.4) compared to stomach pH (1.2). The observed cumulative release is 82.71% at pH 7.4 and 45.67% at pH 1.2 after 10 h. Brunauer-Emmett-Teller analysis reveals the effect of surface area, pore size, and pore volume of hydrogel on the drug release. The drug release from the hybrid chitosan-alginate hydrogel is found to be more sustained in comparison to the pure chitosan hydrogel. For the present drug delivery system, the swelling-controlled release is found to be more dominating than the pH-controlled release. The synthesized hydrogel can be successfully employed as a potential drug delivery system for controlled drug delivery.

Fluorescent composite beads: An advanced tool for environmental monitoring and harmful pollutants removal from water

The quality and safety of water sources have been significantly impacted by various pollutants, including trace elements. To address this concern, this study utilized composite beads made of alginate and carbon quantum dots (CDs) for detecting and removing As(III) and Se(IV) ions in tap water. Fluorescent CDs were hydrothermally synthesized and incorporated into an alginate-Ca2+ matrix through a straightforward procedure. Characterization analyses revealed distinct properties of the composite beads, containing varying amounts of CDs, compared to the pristine beads. Optimal adsorption parameters (30 mg of adsorbent, 10 mg/L of initial pollutant concentration, 35 °C, and 180 min of contact time) for the beads containing 30 w/w-% of CDs (Alg@CDs30) were determined through a fractional factorial design. These composite beads exhibited the highest adsorption capacity for both metals, achieving a removal rate of 94.5% for As(III) and 98.0% for Se(IV) in tap water. Kinetic and isothermal analyses indicated that the adsorption of both metals on Alg@CDs30 involves a combination of chemisorption and diffusion processes. Recycling experiments demonstrated that the composite beads could be reused up to 20 times without a noticeable loss of adsorption efficiency. Regarding the sensing property, our experiments revealed a significant reduction in the fluorescence emission intensity of Alg@CDs30 upon interaction with As(III) and Se(IV), confirming its ability to detect both ions in tap water, with limits of detection (LOD) of 2.6 ± 0.5 μg/L for As(III) and 1.1 ± 0.2 μg/L for Se(IV). The alginate-Ca2+ matrix s contributed to the stability of the CDs' fluorescence. These results confirm the potential of Alg@CDs beads as effective tools for the simultaneous monitoring and removal of hazardous metal ions from real water samples.

Gelatin-Chitosan Hydrogel Biological, Antimicrobial and Mechanical Properties for Dental Applications

Chitosan, a natural polysaccharide sourced from crustaceans and insects, is often used with hydrogels in wound care. Evaluating its cytotoxicity and antimicrobial properties is crucial for its potential use in dentistry.

OBJECTIVE

To investigate the mechanical properties of gelatin hydrogels based on decaethylated chitosan and antimicrobial activity against Streptococcus mutans and their biological effects with stem cells from apical papilla (SCAPs).

MATERIAL AND METHODS

Gelatin-chitosan hydrogels were synthesized at concentrations of 0%, 0.2% and 0.5%. Enzymatic and hydrolytic degradation, along with swelling capacity, was assessed. Fourier transform infrared spectroscopy (FTIR) analysis was employed to characterize the hydrogels. The interaction between hydrogels and SCAPs was examined through initial adhesion and cell proliferation at 24 and 48 h, using the Thiazolyl Blue Tetrazolium Bromide (MTT assay). The antimicrobial effect was evaluated using agar diffusion and a microdilution test against S. mutans. Uniaxial tensile strength (UTS) was also measured to assess the mechanical properties of the hydrogels.

RESULTS

The hydrogels underwent hydrolytic and enzymatic degradation at 30, 220, 300 min and 15, 25, 30 min, respectively. Significantly, (p < 0.01) swelling capacity occurred at 20, 40, 30 min, respectively. Gelatin-chitosan hydrogels' functional groups were confirmed using vibrational pattern analysis. SCAPs proliferation corresponded to 24 h = 73 ± 2%, 82 ± 2%, 61 ± 6% and 48 h = 83 ± 11%, 86 ± 2%, 44 ± 2%, respectively. The bacterial survival of hydrogel interaction was found to be 96 ± 1%, 17 ± 1.5% (p < 0.01) and 1 ± 0.5% (p < 0.01), respectively. UTS showed enhanced (p < 0.05) mechanical properties with chitosan presence.

CONCLUSION

Gelatin-chitosan hydrogels displayed favorable degradation, swelling capacity, mild dose-dependent cytotoxicity, significant proliferation with stem cells from apical papilla (SCAPs), substantial antimicrobial effects against S. mutans and enhanced mechanical properties. These findings highlight their potential applications as postoperative care dressings.

Diffusion-Limited Processes in Hydrogels with Chosen Applications from Drug Delivery to Electronic Components

Diffusion is one of the key nature processes which plays an important role in respiration, digestion, and nutrient transport in cells. In this regard, the present article aims to review various diffusion approaches used to fabricate different functional materials based on hydrogels, unique examples of materials that control diffusion. They have found applications in fields such as drug encapsulation and delivery, nutrient delivery in agriculture, developing materials for regenerative medicine, and creating stimuli-responsive materials in soft robotics and microrobotics. In addition, mechanisms of release and drug diffusion kinetics as key tools for material design are discussed.

A Comprehensive Review of Polysaccharide-Based Hydrogels as Promising Biomaterials

Polysaccharides have emerged as a promising material for hydrogel preparation due to their biocompatibility, biodegradability, and low cost. This review focuses on polysaccharide-based hydrogels' synthesis, characterization, and applications. The various synthetic methods used to prepare polysaccharide-based hydrogels are discussed. The characterization techniques are also highlighted to evaluate the physical and chemical properties of polysaccharide-based hydrogels. Finally, the applications of SAPs in various fields are discussed, along with their potential benefits and limitations. Due to environmental concerns, this review shows a growing interest in developing bio-sourced hydrogels made from natural materials such as polysaccharides. SAPs have many beneficial properties, including good mechanical and morphological properties, thermal stability, biocompatibility, biodegradability, non-toxicity, abundance, economic viability, and good swelling ability. However, some challenges remain to be overcome, such as limiting the formulation complexity of some SAPs and establishing a general protocol for calculating their water absorption and retention capacity. Furthermore, the development of SAPs requires a multidisciplinary approach and research should focus on improving their synthesis, modification, and characterization as well as exploring their potential applications. Biocompatibility, biodegradation, and the regulatory approval pathway of SAPs should be carefully evaluated to ensure their safety and efficacy.

Chitosan membrane drafting silver-immobilized graphene oxide nanocomposite for banana preservation: Fabrication, physicochemical properties, bioactivities, and application

In this study, silver-immobilized graphene oxide/chitosan (AGC/CTS) membranes were assembled by the solvent evaporation method, wherein Curcuma longa extract was used to synthesize silver-immobilized graphene oxide (AGC) nanocomposite. The characterization results showed that the AGC was successfully synthesized with AgNPs distributed quite evenly on GO sheets. The as-prepared AGC also exhibited high antibacterial activity and low cytotoxicity towards normal cell lines compared to human epithelial carcinoma cell lines. Besides, the fabrication of AGC/CTS membranes was additionally assessed with different AGC ratios and thicknesses. The results revealed the membrane containing 3 wt% of AGC with great hygroscopicity and elasticity module of 27.03 ± 3.07 MPa. The samples also performed excellent bactericidal capability, along with good mechanical properties for banana preservation. Therewithal, the membrane-coated bananas were also elucidated to be ripened at slower paces and less damage, with no appearance of patches of mold on the banana peel surface, eventually prolonging the shelf life of bananas up to 10 days as compared to the non-coated ones. The aforesaid results confirm the potential application of the AGC/CTS membrane as a safe and alternative fruit preservation agent in the food industry.

Synthesis and adsorption performance of functionalized chitosan and carboxyethylsilanetriol hybrids

A novel adsorbent from cationic chitosan derivative and anionic silica precursor was fabricated to remove methylene blue (MB). The hybrid material was prepared from N-guanidinium chitosan acetate (GChi) and carboxyethylsilanetriol sodium salt by a simple ionic interaction followed by sol-gel approach. Multiple characterization methods were used to analyze the morphology and the structure of the well-prepared functionalized material. Batch experiments were conducted to optimize the various operational parameters. The Langmuir isotherm was used to fit the data, and it predicted monolayer adsorption with a maximum capacity of 334 mg g^-1. A pseudo-second-order equation fit the adsorption process well. Chitosan/silica hybrids containing carboxylic groups are efficient and cost-effective adsorbents for cationic dyes adsorption from aqueous solutions.

Chitosan-based dual network composite hydrogel for efficient adsorption of methylene blue dye

With the rapid development of the textile industry, a large amount of dyeing wastewater discharge has caused great harm to the ecological environment. In this work, a dual-network, composite hydrogel adsorbent with excellent mechanical properties, good reusability, and large adsorption capacity was prepared by introducing chitosan cross-linked polyvinylamine into the N,N'-methylenebisacrylamide cross-linked polyacrylic acid network. The dual cross-linking network gave the hydrogel excellent mechanical properties with maximum tensile stress and strain up to 1.9 MPa and 920 %. The adsorption capacity of methylene blue on hydrogel was up to 596.14 mg/g. In addition, the prepared hydrogel exhibited good reusability, and their adsorption efficiency remained above 85 % in five consecutive cycles. The adsorption behavior was well fitted by Pseudo-second-order kinetics and the Langmuir equation, indicating that the hydrogel was chemisorbed to the dye as a monolayer. The adsorption mechanism analysis showed that the electrostatic interactions and hydrogen bonding between the functional groups of the hydrogels and methylene blue molecules contributed to the good adsorption capacity. Overall, the synthesized composite hydrogels could be used as an efficient adsorbent for the removal of methylene blue dye, particularly from textile industry wastewater.