Foliar spraying with amino acids and their chitosan nanocomposites as promising way to alleviate abiotic stress in iceberg lettuce grown at different temperatures.

We analyzed the effects of foliar spraying with amino acids, chitosan (CHS) and nanocomposites (NCs) of chitosan with the amino acids proline, L-cysteine and glycine betaine (CHS-Pro NCs; CHS-Cys NCs, CHS-GB NCs, respectively) on the changes in the physiological and biochemical parameters of iceberg lettuce grown at the control temperature (20 °C) and under chilling conditions (4 °C). The physicochemical parameters of the phospholipid monolayers (PLs) extracted from plants showed the effects of the treatments on the properties of the monolayers, namely, the packing density and flexibility. We observed increased accumulation of proline at 4 °C, and differences in the concentrations of sugars in most of the analyzed variants were a consequence of the lowered temperature and/or the use of organic compounds. A temperature of 4 °C caused a significant increase in the L-ascorbic acid level compared with that at 20 °C. Differences were also found in glutathione (GSH) content depending on the temperature and treatment with the tested organic compounds. CHS NCs loaded with Pro and GB were effective at increasing the amount of phenols under stress temperature conditions. We noted that a significant increase in the antioxidant activity of plants at 4 °C occurred after priming with Cys, CHS-Cys NCs, Pro and CHS-Pro NCs, and the CHS nanocomposites were more effective in this respect. Both low-temperature stress and foliar spraying of lettuce with various organic compounds caused changes in the activity of antioxidant enzymes. Two forms of dismutase (SOD), iron superoxide dismutase (FeSOD) and copper/zinc superoxide dismutase (Cu/ZnSOD), were identified in extracts from the leaves of iceberg lettuce seedlings. The application of the tested organic compounds, alone or in combination with CHS, increased the amount of malondialdehyde (MDA) in plants grown under controlled temperature conditions. Chilling caused an increase in the content of MDA, but some organic compounds mitigated the impact of low temperature. Compared with that of plants subjected to 20 °C, the fresh weight of plants exposed to chilling decreased. However, the tested compounds caused a decrease in fresh weight at 4 °C compared with the corresponding control samples. An interesting exception was the use of Cys, for which the difference in the fresh weight of plants grown at 20 °C and 4 °C was not statistically significant. After Cys application, the dry weight of the chilled plants was greater than that of the chilled control plants but was also greater than that of the other treated plants in this group. To our knowledge, this is the first report demonstrating that engineered chitosan-amino acid nanocomposites could be applied as innovative protective agents to mitigate the effects of chilling stress in crop plants.

Dual-drug (Curcumin/Ciprofloxacin) loading and release from chitosan-based hydrogels embedded with magnetic Montmorillonite/Hyaluronic acid for enhancing wound healing.

Montmorillonite (MMt) is extensively applied as an efficient drug-carrier in designing drug delivery systems (DDS) due to its high specific surface area to load drugs. Modification of MMt via iron (Fe) blending can thus be a desirable method to improve its biocompatibility. Herein, magnetic nano-carriers involving the magnetic MMt (mMMt) core surrounded by chitosan (Chito) as a biopolymer and hyaluronic acid (HA) were prepared. To coat the mMMt fabricated through the coprecipitation of the Fe3+/Fe2+ ions in the presence of MMt, the acquired mMMt as the core was then treated with the Chito/HA solution to induce the cross-linked Chito/HA as the shell (namely, the Chito/HA-mMMt). The transmission electron microscopy (TEM) results accordingly revealed the existence of the mMMt inside the Chito/HA solution. Curcumin (CUR) and ciprofloxacin (CIP) were further employed as two model drugs. The CUR and CIP release from the Chito/HA-mMMt subsequently occurred in a sustained manner and pH-dependently. Additionally, an upsurge in the CUR and CIP release by applying an external magnetic field was observed. Thus, the prepared Chito/HA-mMMt hydrogels promise an outstanding potential performance in terms of expanding novel pH-dependent DDS with a sustained release behavior. The scratch assay of the given hydrogels also confirms their applications for wound healing.

Synthesis of magnetic chitosan/hyaluronic acid/κ-carrageenan nanocarriers for drug delivery.

The magnetic nanocarriers containing chitosan/hyaluronic acid complexed with κ-carrageenan were synthesized by solution method, as the drug delivery system. Doxorubicin (DOX) was used as the model drug. Characterization assessments were performed to identify the functional groups, determine the structure and morphology, and magnetic properties of nanodelivery system. Furthermore, their impacts on MCF-7 and MDA-MB-237 cell lines were evaluated by MTT assay. Analyses confirm polymers physical interaction, chemical bonding in the structure, moreover presence of spherical shape magnetic nanoparticles in the 100-150 nm range. The DOX loading was 74.1 ± 2.5 %. Results indicate that the drug loading was raised to 83.0±2.2 % by increasing the amount of κ-carrageenan in specimens. The swelling of samples in the acidic environment (e.g. pH 5.5) was verified by the Dynamic Light Scattering analysis. Consequently, pH stimulus-responsive drug release in the sustained stream and a considerable amount of DOX release (84±3.1 %) was detected as compared to a higher pH medium (27±1.5 % at pH 7.4). According to the MTT assay results, MNPs showed no inhibitory effect on both cell lines. Also, 10 and 15 µg/ml of MNPs-DOX was considered as IC50 value on MDA-MB-237 and MCF-7 cells, respectively. The DOX 25 µg/ml caused 50 % antiproliferative activity in both cell lines.

pH-responsive magnetic biocompatible chitosan-based nanocomposite carrier for ciprofloxacin release.

The pH-sensitive and magnetic-triggered release ensures the effective delivery of drugs. Chitosan carries amine pendants that encourage the fabrication of pH-responsive carriers. Montmorillonite (MMt), an attractive nano-clay in drug delivery possessing high encapsulation properties, was magnetized through the co-precipitation of Fe3+/Fe2+ ions. The study aimed to integrate the magnetic montmorillonite (mMMt) into the chitosan matrix and crosslinked by citric acid (CA) to achieve the nanocomposite carrier with double-responsive features for effective drug delivery. The release evaluation revealed that coating the mMMt with CA-crosslinked chitosan prevented the burst release of Ciprofluxcacin (Cip). The nanocomposite showed a high sustained release, and the release rate in the neutral environment (pH 7.4) was remarkably higher than in acidic media (pH 5.8). The new nanocomposite carrier showed high encapsulation efficiency to Cip (about 98 %). The study was developed by investigating external magnetic effects on the release rate, which lead to an increase in the release rate. The kinetics studies confirmed the diffusion mechanism for Cip release in all experimental media. The Cip-loaded nanocomposite carriers showed antibacterial activity against E. coli and S. aureus.

Seedling nanopriming with selenium-chitosan nanoparticles mitigates the adverse effects of salt stress by inducing multiple defence pathways in bitter melon plants.

Advances in the nanotechnology fields provided crucial applications in plant sciences, contributing to the plant performance and health under stress and stress-free conditions. Amid the applications, selenium (Se), chitosan and their conjugated forms as nanoparticles (Se-CS NPs) have been revealed to have potential of alleviating the harmful effects of the stress on several crops and subsequently enhancing the growth and productivity. The present study was addressed to assay the potential effects of Se-CS NPs in reversing or buffering the harmful effects of salt stress on growth, photosynthesis, nutrient concentration, antioxidant system and defence transcript levels in bitter melon )Momordica charantia(. In addition, some secondary metabolite-related genes were explicitly examined. In this regard, the transcriptional levels of WRKY1, SOS1, PM H+-ATPase, SKOR, Mc5PTase7, SOAR1, MAP30, α-MMC, polypeptide-P and PAL were quantified. Our results demonstrated that Se-CS NPs increased growth parameters, photosynthesis parameters (SPAD, Fv/Fm, Y(II)), antioxidant enzymatic activity (POD, SOD, CAT) and nutrient homeostasis (Na+/K+, Ca2+, and Cl-) and induced the expression of genes in bitter melon plants under salt stress (p ≤ 0.05). Therefore, applying Se-CS NPs might be a simple and effective way of improving crop plants' overall health and yield under salt stress conditions.

pH-sensitive biocompatible chitosan/sepiolite-based cross-linked citric acid magnetic nanocarrier for efficient sunitinib release.

In this study, the magnetite nanoparticles were immobilized on the sepiolite needles via co-precipitation of iron ions. Then, the resulted magnetic sepiolite (mSep) nanoparticles were coated with chitosan biopolymer (Chito) in the presence of citric acid (CA) to prepare mSep@Chito core-shell drug nanocarriers (NCs). TEM images showed magnetic Fe3O4 nanoparticles with small sizes (less than 25 nm) on the sepiolite needles. Sunitinib anticancer drug loading efficiencies were ⁓45 and 83.7 % for the NCs with low and high content of Chito, respectively. The in-vitro drug release results exhibited that the mSep@Chito NCs have a sustained release behavior with high pH-dependent properties. Cytotoxic results (MTT assay) showed that the sunitinib-loaded mSep@Chito2 NC had a significant cytotoxic effect on the MCF-7 cell lines. Also, the in-vitro compatibility of erythrocytes, physiological stability, biodegradability, and antibacterial and antioxidant activities of NCs was evaluated. The results showed that the synthesized NCs had excellent hemocompatibility, good antioxidant properties, and were sufficiently stable and biocompatible. Based on the antibacterial data, the minimal inhibitory concentration (MIC) values for mSep@Chito1, mSep@Chito2, and mSep@Chito3 were obtained as 125, 62.5, and 31.2 µg/mL towards S. aureus, respectively. All in all, the prepared NCs could be potentially used as a pH-triggered system for biomedical applications.

Phenol biodegradation by immobilized Rhodococcus qingshengii isolated from coking effluent on Na-alginate and magnetic chitosan-alginate nanocomposite.

Phenol is a hazardous organic solvent to living organisms, even in its small amounts. In order to bioremediation of phenol from aqueous solution, a novel bacterial strain was isolated from coking wastewater, identified as Rhodococcus qingshengii based on 16S rRNA sequence analysis and named as strain Sahand110. The phenol-biodegrading capabilities of the free and immobilized cells of Sahand110 on the beads of Na-alginate (NA) and magnetic chitosan-alginate (MCA) nanocomposite were evaluated under different initial phenol concentrations (200, 400, 600, 800 and 1000 mg/L). Results illustrated that Sahand110 was able to grow and complete degrade phenol up to 600 mg/L, as the sole carbon and energy source. Immobilized cells of Sahand110 on NA and MCA were more competent than its free cells in degradation of high phenol concentrations, 100% of 1000 mg/L phenol within 96 h, indicating the improved tolerance and performance of the immobilized cells against phenol toxicity. Therefore, the immobilized Sahand110 on the studied beads, especially MCA bead regarding its suitable properties, has significant potential to enhanced bioremediation of phenol-rich wastewaters.

Hydroxyapatite grafted chitosan/laponite RD hydrogel: Evaluation of the encapsulation capacity, pH-responsivity, and controlled release behavior.

In this study, a pH-responsive drug carrier was developed for the controllable release of drugs in the gastric environment. Chitosan (CS), a pH-sensitive biopolymer, and laponite RD (LAP), a nano-clay with a high drug-loading capability, were used to design the new carrier. Hydroxyapatite (HA) was grafted into CS/LAP matrix through a simple co-precipitation technique to overcome the burst release of the CS/LAP. The structural analysis and swelling tests of products demonstrated that the co-precipitation method has led to the penetration of HA nanoparticles inside the CS/LAP matrix and occupying its hollow pores. Occupation of the empty pores can lead to the entrapment of drug molecules, thereby reducing the release rate. The nanocomposite showed a high loading capacity to ofloxacin as a drug model. The effects of HA content on release behavior of nanocomposite were investigated at simulated gastric (pH 1.2) and intestine (pH 7.4) environments. The results indicated a high pH sensitivity for CS/LAP/HA. HA grafting reduced the release rate remarkably regardless of pH. The release rate of CS/LAP/HA decreased by 44-63% in pH 1.2 and 41-51% in pH 7.4 compared to CS/LAP. Kinetic studies indicated that grafting the HA in CS/LAP has changed the drug release mechanism.

Adsorption of Cationic Dyes on a Magnetic 3D Spongin Scaffold with Nano-Sized Fe3O4 Cores.

The renewable, proteinaceous, marine biopolymer spongin is yet the focus of modern research. The preparation of a magnetic three-dimensional (3D) spongin scaffold with nano-sized Fe3O4 cores is reported here for the first time. The formation of this magnetic spongin-Fe3O4 composite was characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential thermal analysis (DTA) (TGA-DTA), vibrating sample magnetometer (VSM), Fourier-transform infrared spectroscopy (FTIR), and zeta potential analyses. Field emission scanning electron microscopy (FE-SEM) confirmed the formation of well-dispersed spherical nanoparticles tightly bound to the spongin scaffold. The magnetic spongin-Fe3O4 composite showed significant removal efficiency for two cationic dyes (i.e., crystal violet (CV) and methylene blue (MB)). Adsorption experiments revealed that the prepared material is a fast, high-capacity (77 mg/g), yet selective adsorbent for MB. This behavior was attributed to the creation of strong electrostatic interactions between the spongin-Fe3O4 and MB or CV, which was reflected by adsorption mechanism evaluations. The adsorption of MB and CV was found to be a function of pH, with maximum removal performance being observed over a wide pH range (pH = 5.5-11). In this work, we combined Fe3O4 nanoparticles and spongin scaffold properties into one unique composite, named magnetic spongin scaffold, in our attempt to create a sustainable absorbent for organic wastewater treatment. The appropriative mechanism of adsorption of the cationic dyes on a magnetic 3D spongin scaffold is proposed. Removal of organic dyes and other contaminants is essential to ensure healthy water and prevent various diseases. On the other hand, in many cases, dyes are used as models to demonstrate the adsorption properties of nanostructures. Due to the good absorption properties of magnetic spongin, it can be proposed as a green and uncomplicated adsorbent for the removal of different organic contaminants and, furthermore, as a carrier in drug delivery applications.

Magnetic κ-carrageenan/chitosan/montmorillonite nanocomposite hydrogels with controlled sunitinib release.

This work aimed to design montmorillonite-incorporated pH-responsive and magnetic κ-carrageenan/chitosan hydrogels via a completely green route for controlled release of sunitinib anticancer drug. This was accomplished by ionic cross-linking of two biopolymers, κ-carrageenan and chitosan, in the presence of magnetic montmorillonite (mMMt) nanoplatelets. Interestingly, it was observed that the amount of mMMt affected not only the microstructure of hydrogels, but also the drug loading efficiency of nanocomposite hydrogels was noticeably increased by introducing mMMt (from 69 to 96%). The in vitro sunitinib release experiments showed that a low content of loaded sunitinib was released from all hydrogels in the buffered solution with pH 7.4. In contrast, a relatively sustained release with a high content of drug release was observed in the acidic solution of pH 5.5. During 48 h, the hydrogels nanocomposite containing a high content of mMMt showed cumulative release of 64.0 and 8.6% at pH 5.5 and 7.4, respectively. During two days, while the cumulative release of sunitinib was obtained 84.3% for the magnetic-free hydrogel, the magnetic ones showed 74.4 and 64% with the low and high contents of magnetic MMt, respectively. The developed κ-carrageenan/chitosan hydrogels with a high capacity of drug loading and subsequent pH-sensitive drug release can be considered in prolonged cancer therapy with reduced side effects.

Highly efficient sunitinib release from pH-responsive mHPMC@Chitosan core-shell nanoparticles.

This study reports developing novel smart drug delivery systems (DDS) that have great importance in anticancer therapeutics. The magnetic hydroxypropyl methylcellulose (mHPMC) synthesized via in situ method and introduced in the fabrication of tripolyphosphate (TPP)-cross-linked chitosan core-shell nano-carriers (mHPMC@Chitosan). The TPP-cross-linked mHPMC@Chitosan nano-carriers then characterized using TEM, SEM/EDS, DLS, XPS, FTIR, TGA, XRD, and VSM. The encapsulation efficiency showed high capacity of loading for sunitinib malate (above 86 % for all samples). At pH 7.4, the minimum content of drug release was observed for all samples fabricated with variable contents of chitosan. At pH 4.5, the effect of chitosan content revealed that the rate of sunitinib release tends to decrease as its content increased. During two days, 44 and 93 % of the loaded sunitinib released from carriers containing high and low contents of chitosan, respectively. Besides, this mHPMC@Chitosan core shell nano-carrier shown pH-sensitive drug release.

Preparation and characterization of antibacterial magnetic-/pH-sensitive alginate/Ag/Fe3O4 hydrogel beads for controlled drug release.

This work reports the synthesis of novel antibacterial magnetic-/pH-sensitive hydrogel beads based on ionotropic-gelation of alginate biopolymer. Using pomegranate peels extract, green-Ag nanoparticles were synthesized inside a mixture of alginate and Fe3O4, via in situ method. The alginate beads were investigated by VSM, TEM, XRD, and FE-SEM techniques. The introducing Ag and Fe3O4 nanoparticles in hydrogel beads caused a reduction in the swelling capacity of hydrogel beads. Besides, a pH-dependent swelling behavior was observed for hydrogel beads with a maximum swelling capacity at pH = 7.4. Diclofenac sodium (DS) as a model drug was loaded in hydrogel beads and its release showed a pH-dependent behavior. Drug release studies exhibited significant behaviors on the subject of physiological simulated pHs with a high release rate at pH = 7.4. The alginate beads have shown a prolonged and successive controlled drug release nearly 83% at pH = 7.4 and time 200 min. In addition to the pH, the release of DS from magnetic beads was affected by the external-magnetic-fields. Also, the Ag-incorporated alginate beads showed strong antibacterial activity against S. aureus and E. coli. These results indicated that the hydrogel beads have potentially applicable in drug delivery systems.

Chitosan cross-linked with κ-carrageenan to remove cadmium from water and soil systems.

In this study, magnetic bio-adsorbent based on chitosan with high molecular weight was prepared. To stabilize under acidic condition, the synthesized magnetic chitosan was cross-linked with κ-carrageenan (mChitoCar). The magnetic bio-adsorbent was characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results indicated that mChitoCar had desirable magnetic-sorption properties, and magnetic/bio-adsorbent was successfully synthesized and cross-linked. The present nanocomposite was applied to remove and immobilize Cd2+ from water and soil systems. Adsorption and desorption of cadmium by the chitosan bio-adsorbent were investigated using batch experiments. Isotherm data were described by using Freundlich, Langmuir, Dubinin-Radushkevich, and Temkin models, and better fitting was introduced by Freundlich model in both water and soil systems. The maximum adsorption capacity (b) of cadmium onto mChitoCar appeared to increase from the water system to the soil system, from 750.2 to 992.7 µmol/g, respectively. The adsorption mechanism with the help of potential theory indicates the adsorption of cadmium onto the mChitoCar surface is following chemical adsorption type. To evaluate the efficiency of the modified chitosan as a good bio-adsorbent in water and soil system, the difference between adsorption and desorption amounts, Δq, was calculated. By comparing the amounts of Δq, the bio-adsorbent is not economically feasible at high initial concentrations in the water system. But, the bio-adsorbent used can be relatively economic as a soil modifier.

In vitro evaluation of sustained ciprofloxacin release from κ-carrageenan-crosslinked chitosan/hydroxyapatite hydrogel nanocomposites.

Although the traditional hydrogels have shown great potential applications in designing drug delivery systems, the burst release of drugs remains an issue. In this work, we develop and evaluate a sustained release of ciprofloxacin using chitosan/hydroxyapatite/κ-carrageenan complexes. The size and structure of HA nanoparticles were characterized by X-ray diffraction, transmittance electron microscopy, and Fourier-transform infrared spectroscopy. The ciprofloxacin-loaded hydrogel nanocomposites exhibited antibacterial activity against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria. Due to the introduced HA, the release of ciprofloxacin occurred in a sustained release manner. While the pristine chitosan/κ-carrageenan complex released about 98% of ciprofloxacin during 120 h, only 52 and 66% of the loaded drug was released from hydrogel nanocomposites containing high and low content of HA, respectively. The sustained release of ciprofloxacin from the hydrogel nanocomposites identifies them as a potential candidate for designing drug delivery systems with prolonged release ability.

pH-controlled sunitinib anticancer release from magnetic chitosan nanoparticles crosslinked with κ-carrageenan.

The main objective of this work was to develop κ-carrageenan-crosslinked magnetic chitosan with different molecular weights as pH-responsive carriers for controlled release of anticancer drug sunitinib. The characterization of magnetic carriers revealed that the size of magnetic nanoparticles is affected by the molecular weight of chitosan. Drug encapsulation efficiency and release performance influenced by the size of magnetic nanoparticles. Encapsulation efficiencies of sunitinib by low, medium and high molecular weights of magnetic chitosan carriers were found to be 62.38, 69.57 and 78.42%, respectively. The in vitro sunitinib release from magnetic chitosan/κ-carrageenan carriers was pH-dependent and followed a Fickian release mechanism. Sunitinib was efficiently released from magnetic carriers into environment under acidic pHs and the release rate was size- and molecular weight-dependent. The pH-dependent release of sunitinib with a minimal release content at pH = 7.4 makes the present magnetic carriers as promising candidate for anticancer drugs with reduced side effects.

Encapsulation of Satureja hortensis L. (Lamiaceae) in chitosan/TPP nanoparticles with enhanced acaricide activity against Tetranychus urticae Koch (Acari: Tetranychidae).

The objective of this study was the fabrication of encapsulated Satureja hortensis essential oil (S.EO) in chitosan/tripolyphosphate nanoparticles (CS/TPP-NPs) via ionic gelation technique and investigation of its acaricidal effect. A high encapsulation efficiency of 96.17% was obtained, which shows successful encapsulation of EOs in CS-TPP nanoparticles. Transmission electron microscopy (TEM) analysis proved the formation of spherical S. hortensis EO-loaded chitosan nanoparticles (S.EO@NPs). Fourier-transform infrared spectroscopy (FTIR) analysis demonstrated the presence of encapsulated S.EO in CS/TPP nanoparticles. The average size of nanoparticles was found to be 192.1 ±â€¯11 nm using dynamic light scattering (DLS) technique. Moreover, durability and fumigant acaricide activity of S.EO@NPs against Tetranychus urticae Koch were investigated. The obtained results demonstrated that there were considerable differences between pure S. hortensis EO and S.EO@NPs in their ovicidal, adulticidal, and persistence activities against T. urticae. The LC50 values of pure EO and as-prepared S.EO@NPs against adult mite were 4.95, 46.98 µL/L after 24 h exposure and 2.02, 31.30 µL/L after 72 h exposure, respectively. Fumigation exposure for 24 and 72 h showed that the sensitivity of adults T. urticae were more than the eggs of T. urticae. The LC50 values of fumigant toxicity of pure S.EO and S.EO@NPs against eggs of T. urticae were measured after 24 and 72 h. The experimental results for 24 h treatment showed 6.71 and 211.66 µL/L air LC50 values for pure S.EO and S.EO@NPs, respectively. In the case of 72 h exposure, The LC50 values of pure S.EO and S.EO@NPs were 4.15 and 107.38 µL/L air, respectively. A sustained release of S.EO from S.EO@NPs was observed during 25 days of the study, indicating the persistence acaricide activity for a long time. The as-prepared S.EO@NPs and pure S.EO illustrated 67% and 2% mortality at 18th day exposure, respectively. The notable increasing of the residual fumigant toxicity may be related to the slow and sustainable release of the active ingredient of EO. Based on this study, the S.EO@NPs showed significantly residual adulticidal activity against adults of T. urticae. S.EO@NPs would be recommended as an alternative for pure EOs and other common acaricides.

Polyvinyl alcohol-based nanocomposite hydrogels containing magnetic laponite RD to remove cadmium.

In this study, magnetic nanocomposite hydrogels based on polyvinyl alcohol were synthesized. Magnetic polyvinyl alcohol/laponite RD (PVA-mLap) nanocomposites were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy. The results indicated that PVA-mLap had desirable magnetic-sorption properties and magnetic-laponite nanoparticles were successfully synthesized and added to polyvinyl alcohol. The present nanocomposites were applied to remove Cd2+ from aqueous solution. The influence of initial Cd2+ concentration, magnetic-laponite concentration, pH, and ionic strength on adsorption isotherm was investigated. Heterogeneity of adsorption sites was intensified by increasing magnetic concentration of adsorbents and by rising pH value. Results of ionic strength studies indicated that by increasing ionic strength more than four times, the adsorption of Cd2+ has only decreased around 15%. According to the results, the dominant mechanism of Cd2+ sorption by the present adsorbents was determined chemical and specific sorption. Therefore, the use of the present nanocomposites as a powerful adsorbent of Cd2+ in the wastewater treatment is suggested. Isotherm data were described by using Freundlich and Langmuir models, and better fitting was introduced Langmuir model.

Ionically crosslinked magnetic chitosan/κ-carrageenan bioadsorbents for removal of anionic eriochrome black-T.

Magnetic bioadsorbents based on chitosan with different molecular weights were prepared. To stabilize under acidic condition the synthesized magnetic chitosan was crosslinked with κ-carrageenan. The characterization of magnetic bioadsorbents revealed that the size of magnetic nanoparticles is affected by the chitosan molecular weight. Magnetic nanoparticles with larger sizes were obtained with the high molecular weight of chitosan. The removal of eriochrome black-T (EBT) by the magnetic bioadsorbents was investigated. The equilibrium adsorption isotherm data of EBT on bioadsorbents were found to be well explained through Langmuir isotherm model, from which the maximum adsorption capacities were found to be 280, 235, and 199mg/g for bioadsorbents prepared with low, medium, and high molecular weights of chitosan, respectively. A remarkable reduction in adsorption capacities of bioadsorbents was observed as the pH of dye solution was increased. The reduction in the dye adsorption under basic media suggested using a mild condition (pH=9) to recycle and reuse the bioadsorbents. Cyclic experiments indicated that current bioadsorbents can be effectively reused to remove anionic EBT from aqueous solutions. The removal efficiencies remained >93% even after five adsorption-desorption cycles, which suggest the present bioadsorbents as a great candidate in the wastewater treatment.

Model protein BSA adsorption onto novel magnetic chitosan/PVA/laponite RD hydrogel nanocomposite beads.

Chitosan-based magnetic beads were developed by solution-mixing method. Firstly, the Fe3O4 nanoparticles were in situ immobilized on laponite RD sheets. The magnetic laponite RD was then dispersed in PVA and mixed with chitosan solution. PVA was aimed to prevent the disintegration of chitosan under acidic media due to its ability to form hydrogel network through freezing-thawing method. The manufactured magnetic chitosan/PVA/laponite RD beads were utilized for adsorption study of a model protein, bovine serum albumin (BSA). The adsorption of BSA on beads was pH-dependent where smaller mass of protein was adsorbed at pH values lower than isoelectric point of BSA. Moreover, it was discovered that introduction of magnetic laponite RD can improve the adsorption capacity of magnetic beads for BSA in which hydrogel with the highest content of magnetic laponite RD demonstrated the maximum adsorption capacity for BSA (qm=240.5mg/g). Langmuir model described the isotherm data better than Freundlich model.

Bioinspired fully physically cross-linked double network hydrogels with a robust, tough and self-healing structure.

The conventional covalently cross-linked double network (DN) hydrogels with high stiffness often show low toughness and self-healing property due to the irreversible bond breakages in their networks. Therefore, scarcity of hydrogels that possess simultaneous features of stiffness, toughness, and autonomous self-healing properties at the same time remains a great challenge and seriously limits their biomedical applications. While, many natural materials acquire these features from their dynamic sacrificial bonds. Inspired by biomaterials, herein we propose a novel strategy to design stiff, tough and self-healing DN gels by substitution of both covalently cross-linked networks with strong, dynamic hydrogen bond cross-linked networks. The prepared fully physically cross-linked DN gels composed of strong agar biopolymer gel as the first network and tough polyvinyl alcohol (PVA) biopolymer gel as the second network. The DN gels demonstrated multiple-energy dissipating mechanisms with a high modulus up to 2200kPa, toughness up to 2111kJm-3, and ability to self-heal quickly and autonomously with regaining 67% of original strength only after 10min. The developed DN gels will open a new avenue to hydrogel research and holds high potential for diverse biomedical applications, such as scaffold, cartilage, tendon and muscle.