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A superabsorbent hydrogel composite based on a starch-grafted-poly(sodium acrylate) matrix filled with husk rice ash (RHA) was synthesized and tested as a soil conditioner to enhance the melon seedling growth. The incorporation of 20 wt% of RHA in the hydrogel matrix endowed the composite with an outstanding liquid uptake capacity (42,000%). Field experiments were performed to investigate the effect of the amount of hydrogel, type o subtract (sandy soil and coconut fibers) and type of soil (sandy soil and clay soil) on several parameters related to the plants' growth process. Overall, the plants cultivated in coconuts fibers exhibited the highest plant growth (5.60 cm) as compared to the plants cultivated in sandy soil (4.12 cm); however, the conditioning effect was limited in this case. Also, in this experiment, the amount of hydrogel used only affected the plant roots size. Additional analyses showed that the plant growth process is enhanced in clay soil as compared to sandy soil. Here, a synergistic beneficial effect was noticed between the type of soil and the amount of hydrogel used as conditioners. A small amount of hydrogel (≤ 0.75 wt%) had an apparent positive effect on the plants' growth process when they are cultivated in clay soils. In summary, the results presented here allow inferring that these composite hydrogels can be ranked as promising materials for use as soil conditioners.

In this study, hydrogel composites based on chitosan-g-poly(acrylic acid) matrices filled with cellulose nanowhiskers (CNWs) were prepared, and their ability to adsorb Pb(II) and Cu(II) ions from the water was investigated. A factorial design approach was performed to examine the effect of some selected parameters on the adsorption process. The optimized conditions revealed that the highest adsorption of Pb(II) (818.4 mg/g) and Cu(II) (325.5 mg/g) is obtained within 30 min, at pH 4.0, using 20 mg of the hydrogel composite containing 10 w/w-% of CNWs. As assessed, functional groups available in the hydrogel matrix and CNWs act as coordination sites for the adsorption. The Langmuir type I isotherm fitted the experimental adsorption data indicating monolayer formation drive the adsorption process. The maximum adsorption capacity of the hydrogel composite prepared in this study concerning the two selected metals was comparable or better than those reported to other similar adsorbent materials. Also, adsorption kinetics followed the pseudo-second-order model. Desorption studies indicate that the post-utilized hydrogel composite can be regenerated and reused again in new adsorption processes without a dramatic loss of efficiency. The results presented here shed light on some essential aspects related to the design and application of hydrogel composites containing nanocellulose in the adsorption process. Moreover, these findings may be helpful to obtain adsorbent materials for practical applications.

In this study, Schiff bases of chitosan (CS) were synthesized using citronellal, citral, and their derivatives containing selenium and sulfur. Organoselenium and organosulfur compounds show attractive biological and pharmaceutical activities, which can be beneficial to CS-based materials. From the characterization analyses, it was found that the CS-derivatives containing organoselenium and organosulfur compounds exhibited the highest conversion degrees (23 and 28%). Biological assays were conducted using films prepared by the blending of CS-derivatives and poly(vinyl alcohol). The antimicrobial evaluation indicated that the film prepared with the sulfur-containing CS was the most active against the tested pathogens (Escherichia coli, Staphylococcus aureus, and Candida albicans) since it reduced considerably their counts (42.5%, 17.4%, and 18.7%). Finally, in vivo assays revealed that this film attenuates atopic dermatitis-like symptoms in mice by suppressing the increase of myeloperoxidase (MPO) activity and reactive species (RS) levels induced by 2,4-dinitrochlorobenzene (DNCB). In summary, CS-derivatives containing chalcogens, mainly organosulfur, are potential candidates for biomedical applications such as for the treatment of chronic skin diseases.

Waste coffee-grounds (WCG), a poorly explored source of biocompounds, were combined with chitosan (Cs) and poly(vinyl alcohol) (PVA) in order to obtain composites. Overall, WCG showed a good interaction with the polymeric matrix and good dispersibility up to 10 wt-%. At 5 wt-% WCG, the composite exhibited a noticeable enhancement (from 10 to 44%) of the adsorption of pharmaceuticals (metamizol (MET), acetylsalicylic acid (ASA), acetaminophen (ACE), and caffeine (CAF)) as compared to the pristine sample. The highest removal efficiency was registered at pH 6 and the removal followed the order ASA > CAF > ACE > MET. For all pharmaceuticals, the adsorption kinetics was found to follow the pseudo-second order model, while the adsorption mechanism was explained by the Freundlich isotherm. Reuse experiments indicated that the WCG-containing composite has an attractive cost-effectiveness since it presented a remarkable reusability in at least five consecutive adsorption/desorption cycles.

The efficiency of Fenton and Fenton-like processes can be seriously affected by the continuous loss of iron ions and by the formation of solid sludge. Here, alginate (Alg) films were synthesized to stabilize iron ions (Fe 2+ and Fe 3+ ) and to enhance their catalytic activities towards the decolorization of methyl orange via heterogeneous Fenton and Fenton-like processes. Iron ions were ionically bond to the Alg molecules resulting in a three-dimensional network with specific structural and morphological features according to the valence states of iron. Our results demonstrated that both Alg-Fe 2+ and Alg-Fe 3+ films show highlighted catalytic activity for the decolorization of MO and high decolorization rates. Reuse experiments demonstrated that both films could be employed in at least five consecutive decolorization processes without losing their catalytic efficiency or stability. Taken together, our findings reveal that the Alg-Fe 2+ and Alg-Fe 3+ films may be suitable low-cost catalysts in heterogeneous Fenton and Fenton-like processes.

Hydrogels based on biopolymers like Gum Arabic (GA) usually show low applicability due to weak mechanical properties. To overcome this issue, (nano)fillers are utilized as reinforcing agents. Here, GA hydrogels were reinforced by chitin nanowhiskers (CtNWs, aspect ratio of 14) isolated from the biopolymer chitin through acid hydrolysis. Firstly, GA was chemically modified with glycidyl methacrylate (GMA), which allowed its crosslinking by free radical reactions. Next, hydrogel samples containing different concentrations of CtNWs (0–10 wt%) were prepared and fully characterized. Mechanical characterization revealed that 10 wt% of CtNWs promoted an increase of 44% in the Young's modulus and 96% the rupture force values compared to the pristine hydrogel. Overall, all nanocomposites were stiffer and more resistant to elastic deformation. Due to this feature, the swelling capacity of the nanocomposites decreased. GA hydrogel without CtNWs exhibited a swelling degree of 975%, whereas nanocomposites containing CtNWs exhibited swelling degrees under 725%.

Superabsorbent hydrogels composites based on the biopolymer starch (ST) and rice husk ash (RHA) were successfully developed and tested towards the removal of methylene blue (MB), a cationic dye. RHA content hit the morphology, mechanical and water uptake properties of the composite. Batch adsorption experiments, carried out under pH 5 at 33 °C and with 2000 mg L−1 as the initial concentration of MB, showed that at 5 wt% RHA the composite exhibited a remarkable adsorption capacity reaching up to 1906.3 mg g−1 within 60 min. The adsorption kinetics followed the pseudo-second-order model and intraparticle diffusion was involved in this process. The Langmuir adsorption isotherm suggested a monolayer formation and spontaneous process. Thermodynamic parameters confirmed the spontaneity of the adsorption and suggested electrostatic interaction among the cationic dye molecules and the anionic adsorption sites on the adsorbent surface. FTIR analysis confirmed the adsorption process occurs via electrostatic mechanism associated with hydrophobic interactions. The adsorbents showed reusability with slight loss of adsorption capacity in five consecutive adsorption/desorption cycles. These results demonstrate ST/RHA superabsorbent composite as a low-cost, eco-friendly, robust and powerful adsorbent material for wastewater remediation.

Physical adsorption has shown to be facile and highly effective to deposit chitosan nanowhiskers (CsNWs, 60 % deacetylated, length: 247 nm, thickness: 4-12 nm, width:15 nm) on electrospun cellulose acetate nanofibers (CANFs, 560 nm) to effect complete surface charge reversal from negatively charged CANFs (-40 mV) to positively charged CsNWs-adsorbed CANFs (+8 mV). The CsNWs coverage did not alter the smooth and homogeneous morphology of fibers, as observed from SEM images. Biological assays showed the CsNWs covered nanofibers were effective against the Gram-negative bacterium E. coli, reducing 99 % of colony forming units (CFU) in 24 h and atoxic to healthy Vero cells. The use of CsNWs to modify cellulose fiber surfaces has been proved to be efficient and may be applied to a broad scope of fields, especially as biomaterials and biomedical applications.

Superabsorbent hydrogels (SH) continue being a very important issue in both academic and industrial fields due to their applications in several technologies. This is proved by the impressive number of publications, through papers and patents as well, dealing with SH. This review is targeted to update and discuss some important aspects of synthesis, characterization and application of SH in agriculture, mainly those based on polysaccharides, as soil conditioners and as polymer carriers for nutrient release. Basic properties of SH and some methods for chemically modifying polysaccharides are given and some directions for hydrogels preparation are highlighted as well. Mechanisms associated with water transport into the 3D matrix, taking into account the transference of mass from hydrogel–soil system to plant, are discussed in the light of some mathematical models. Release of nutrients either from granules coated by hydrophilic polymer or from SH, targeting applications in agriculture, is also discussed on the basis of often used mathematical models (the swelling-based kinetic models) and on a diffusion-based kinetic model with a partition activity coefficient. Examples of recent applications in agriculture as soil conditioners and carriers for nutrient release (fertilizers, etc.) are given. At the final, future trends and perspectives are considered. More than two hundreds references are cited in the whole text.

Cellulose nanowhiskers (CNWs, 90% crystalline) were used to enhance the adsorption capacity of chitosan-g-poly(acrylic acid) hydrogel. The composites up to 20 w/w-% CNWs showed improved adsorption capacity towards methylene blue (MB) as compared to the pristine hydrogel. At 5 w/w-% CNWs the composite presented the highest adsorption capacity (1968 mg/g). The maximum removal of MB (>98% of initial concentration 2000 mg/L) was achieved quickly (60 min) at room temperature, pH 6, and at low ionic strength (0.1 M). Adsorption mechanism was explained with the Langmuir type I model suggesting the formation of a MB monolayer on the adsorbent surface. The interaction between the adsorbent and MB molecules was explained by chemisorption, as suggested by the pseudo-second-order kinetic model. Desorption experiments showed that 75% of loaded-MB could be recovered from the adsorbent by its immersion in a pH 1 solution. Additional experiments showed the post-utilized composite could be regenerated and reused for at least 5 consecutive adsorption/desorption cycles with minimum efficiency loss (∼2%).

The formation of a novel type of hydrogel that combines chemically and physically crosslinked networks in a dual-network approach is presented here. Chitosan (CHT) and chondroitin sulfate (CS) were chemically modified with glycidyl methacrylate (GMA) and then crosslinked. The chemical hydrogels (CHT- and CS-gel) were deposited in different vials filled with CS or CHT stock solutions to form the dual-network hydrogels. FTIR, TGA and XRD analyses were used to characterize the chemical and the dual-network hydrogels. The percentages of CS or CHT complexed to the CHT- and CS-gel networks were calculated from the HPLC data. SEM images and swelling assays indicated that the formation of a secondary network by polyelectrolyte complexation changes the morphologies and liquid uptake capacities of the chemical hydrogels. Hence, the data and discussion presented here enable the formation of dual-network hydrogels with very interesting properties, such as the ability to interact with charged specimens (i.e., drugs, proteins or metal ions), a desirable feature for a wide range of applications.

In this study, copper nanoparticles (CuNPs) were synthesized and stabilized into a chitosan/poly(vinyl alcohol) (CP) based film using a simple protocol under mild conditions. The polymeric matrix utilized in this study allows synthesizing stable nanoparticle with narrow size distribution within the film matrix. Further, this system showed very attractive properties, such as good mechanical properties, chemical resistance, easy handling during use and recovery, relatively low-cost as compared to other similar systems, among others. The catalytic performance of CP-Cu film was tested in the reduction reaction of nitrobenzene (NB) to aniline (AN). Our findings reveal that CP-Cu film catalyzes the reaction efficiently and also decreases the energy of activation (Ea) as compared to other catalysts. The catalytic efficiency of CP-Cu regarding this reaction was kept even after 6 consecutive reuse cycles. All these results rank this novel system as a promising catalyst in the reduction of aromatic nitro compounds to aromatic amines.

Eco-friendly pectin and pectin/cellulose microfibers beads (PB and PB-CF) were synthesized using compounds extracted from orange bagasse, a solid waste from the food industry. PB-CF beads showed remarkable differences regarding several properties as compared to the beads without CF. The adsorption capability of PB and PB-CF was tested towards the removal of methylene blue (MB) from aqueous solution. The effect of various parameters on the MB adsorption was investigated. The kinetics and mechanism of adsorption were explained by the pseudo-second-order kinetics and intra-particle diffusion models. Equilibrium adsorption data are explained by the Langmuir isotherm model, which revealed a maximum adsorption capacity of 1550.3mg/g for PB and 2307.9mg/g for PB-CF5. Thermodynamic analysis suggests that the adsorption of MB on the beads is spontaneous and favorable. Recycling study demonstrated that both PB and PB-CF5 can be implemented in 6 consecutive adsorption/desorption cycles without losing their adsorption capacity. These results enable the use of PB and PB-CF as potentially low-cost adsorbents for wastewater treatments.

Atopic dermatitis (AD) is a chronic inflammatory skin disease that affects a large percent of the world́s population. This long-lasting skin disease has been treated by different approaches according to its causative agent and severity. Nonetheless, the use of advanced biomaterials to treat AD is poorly explored. The present study assessed the protective effectiveness of biocomposites films based on chitosan (Cs), poly(vinyl alcohol) (PVA) and bovine bone powder (BBP) on AD-like skin lesions. These original biocomposites were fully characterized and in vivo biological assays concerning the AD treatment were performed using a mouse model induced by 2,4-dinitrochlorobenzene (DNCB). The dorsal skin and ear of Balb/c female mice were challenging cutaneously with DNCB. Our findings demonstrate BBP-based biocomposite attenuated and treated considerably the DNCB-induced skin lesions in an AD-like model. In this sense, this study suggests that this original biocomposite may be applied as an active biomaterial for AD treatment.

The preparation and characterization of natural polymer-based hydrogels that contain 50-nm diameter magnetite (i.e., FeO:Fe(2)O(3)) nanoparticles are described herein. Fourier-transform infrared spectroscopy (FTIR) analysis confirmed the efficiency of the polysaccharide-modifying process. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and compressive moduli demostrate that the presence of magnetite improves thermal and mechanical resistance. Transient diffusion of water in magnetic hydrogels was analyzed via boundary layer mass transfer across an expaning interface, and the degree of swelling of these polysaccharide hydrogels decreases in the presence of magnetite, with no variation in the binary diffusion mechanism. The absence of hysteresis loops and coercivity observed via magnetometry suggests that magnetic hydrogels are useful for remote-controlled drug release, as demonstrated by magnetic-field-induced release of curcumin. Experiments reveal that magnetic hydrogels with greater magnetic susceptibility have the potential to release larger concentrations of drugs from the hydrogel network.

A2 4-1 fractional factorial design was used to evaluate the effect of some parameters, such as the acrylic acid (AA)/chitosan (CTS) molar ratio, crosslinker concentration, initiator concentration, and filler concentration, in the swelling capacity of superabsorbent hydrogel composites based on CTS-graft-poly(acrylic acid) and nontronite clay. The data from wide-angle X-ray scattering and Fourier transform infrared spectroscopy confirmed the syntheses of the hydrogel composites. Main and interaction effects were analyzed by anal- ysis of variance, F tests, and p values. We found that the AA/CTS and crosslinker were the most influential effects in the evaluated response. The proposed statistical model presented a high coefficient of determination (R 2 ¼ 0.985). In addition to the swelling kinetics, the effects of pH and salt for the both compositions (with and without filler), which presented the best water uptake, were evaluated. Both hydrogels showed responsive behavior in relation to the pH and the salt solution, presenting good potential for application as devi- ces in the controlled release of solutes. V C 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 128: 3480-3489, 2013

Hydrogels based on natural polymers have been widely applied as vehicles for controlled drug release because of their advantages and interesting properties. In this study, a physical hydrogel based on chitosan and chondroitin sulfate (CS) was formed under mild conditions to act as a potential device for the controlled release of theophylline (TH). In vitro CS and TH release studies at pH 2 and 8 were performed. Under acid conditions (pH 2), the fraction of TH released (ca. 0.87) was higher than that of CS (ca. 0.13). On the other hand, under basic conditions, the fractions released of both substances were similar (ca. 0.57). In addition, the system presented in this work was able to sustain the TH release in a controlled way for 30 h. The variation of the pH affected the mechanical properties and contributed to form ordered regions within the hydrogel network, as observed through compression tests and wide-angle X-ray scattering analysis. The experimental data and discussion presented in this article will contribute to the development of a new vehicle for controlled TH release; this ensures the efficacy of the drug and reduced the number of daily doses administered. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Superabsorbents hydrogel nanocomposites based on starch-g-poly(sodium acrylate) and cellulose nanowhiskers (CNWs) were synthesized. A set of experiments was performed to evaluate the influence of some factors such as NaAc/starch mass ratio, crosslinker, and nanowhiskers amount in the swelling capacity and swelling kinetics. Increasing the NaAc/starch mass ratio up to 7 leads to an increase in the water uptake at a maximum value, however, higher ratios decreased that value due to the increase of crosslinking points. Similarly, the incorporation of CNWs up to 10 wt% provided an improvement in the swelling due to the hydrophilic groups from cellobiose units. Further, the incorporation of CNWs diminishes the water uptake. Besides, the CNWs improved the mechanical properties. SEM images showed that CNWs increase the average porous size of composites. The composites presented good responsive behavior in relation to pH and salt presence allowing those materials suitable for many potential applications.

Superabsorbent hydrogels, based on poly(acrylamide-co-acrylate) filled with cellulose nanowhiskers (CNWs), were synthesized by free-radical aqueous copolymerization, using N,N-methylenebisacrylamide (MBAAm), as crosslinker, and potassium persulfate (K2S2O8), as initiator. A series of hydrogels was synthesized varying the percentage of CNWs (1, 2, 5, 10, and 20 wt.%) and the amount of crosslinking agent (0.05, 0.10, 0.15, and 0.20 mol.%). The hydrogels were characterized by FTIR and XRD techniques and their morphologies were investigated by SEM images. Superabsorbent hydrogel with Weq > 1195 g H 2 O /ggel was obtained with percentage of 10 wt.% of CNWs and 0.05 mol.% of crosslinking agent. The hydrogel showed to be responsive to the pH-variation (2–12) and also to the presence of salts (NaCl, KCl, MgCl2, and CaCl2). The hydrogel exhibited a pH-responsiveness and cation-sensitivity character so that a swelling–deswelling pulsatile behavior was recorded at pH 2–8 as well as cycles of hydrogel immersion in sodium and calcium salts solutions.

a b s t r a c t Superabsorbent hydrogel composites based on cellulose nanofibrils and chitosan-graft-poly(acrylic acid) copolymer were developed in this work. The FTIR data showed that the copolymerization and the com- posite formation reaction were successfully performed. In addition, the XRD pattern indicated that the nanofibrils crystallinity was as high as 90%. A 24−1 fractional factorial design was employed to evaluate the effect of acrylic acid/chitosan molar ratio, crosslinker, initiator, and filler in the swelling capacity of hydrogel composites. By the analysis of variance (ANOVA), including F-test and P-values, it was found that the crosslinker and filler correspond to 40% and 30% of the evaluated response, respectively. The addition of nanofibrils provided faster equilibrium conditions as well as improved the swelling capacity in ca. 100 units, from 381 to 486. SEM images showed that the addition of nanofibrils into the hydrogel matrix increased the averaged-dimension of porous. Finally, the composites showed responsive behavior in relation to pH and salt solution. Such characteristics make these smart materials suitable for several technological applications. © 2011 Elsevier Ltd.

This work reports on the formation and characterization of a polyelectrolyte complex based on pectin (PT), functionalized with primary amine groups (PT–NH 2 ), and chondroitin sulfate (CS). From the simple mixture of PT–NH 2 and CS, in acid conditions, it was formed a polyelectrolyte complex, labeled as PT–NH 2 /CS complex, which was confirmed through FTIR spectroscopy. The electrostatic interactions among the protonated amine groups from PT–NH 2 and the sulfate groups from CS are responsible by complex formation. XRD patterns and thermal analysis showed that the complex formation disrupts some interactions present on the PT–NH 2 and CS, but on the other hand, others are created. SEM images showed that the PT–NH 2 /CS complex presents a porous and rough morphology. PT–NH 2 /CS complex is new material that maintains the properties of CS with synergic association of properties from both polymers, which could maximize its applicability as biomaterial, for example.

This work reports the preparation of hydrogels based on PVA-GMA, PVA-GMA is poly(vinyl alcohol) (PVA) functionalized with vinyl groups from glycidyl methacrylate (GMA), and on PVA-GMA with different content of chon- droitin sulfate (CS). The degrees of swelling of PVA-GMA and PVA-GMA/CS hydrogels were evaluated in distilled water and the swelling kinetics was performed in simulated gastric and intestinal fluids (SGF and SIF). PVA-GMA and PVA- GMA/CS hydrogels demonstrated to be resistant on SGF and SIF fluids. The elastic modulus, E, of swollen-hydrogels were determined through compressive tests and, according to the obtained results, the hydrogels presented good mechanical properties. At last, the presence of CS enhances the hydrogel cell compatibility as gathered by cytotoxicity assays. It was concluded that the hydrogels prepared through this work presented characteristics that allow them to be used as biomaterial, as a carrier in drug delivery system or to act as scaffolds in tissue engineering as well.

This work reports the formation of chitosan (CHT)/chondroitin sulfate (CS) polyelectrolyte complexes and evaluates the changes in their complexation-stoichiometries, crystallinity, and mechanical properties at different pHs used for both complex preparation and swelling. Through high-performance liquid chromatography, the changes in CHT/CS complex stoichiometry due to CS release from CHT/CS complexes, which occurred mainly during swelling at pH ≥6, were determined. In addition, strong evidences of self-assembling on CHT/CS complex network as swelled at pH 12 buffer were observed by WAXS patterns. Such a new rearrangement of the network increases the CHT/CS complexes rigidity as well as their elastic moduli, E, as observed through compressive tests. The results found in this work provide new information to allow the tailoring of the biofunctionalities of the CHT/CS complex for the development of physiological pH-compatible materials.

N , N , N -trimethyl chitosan (TMC) was synthesized through the N -methylation of chitosan (CHT) and characterized by FTIR and 1 H NMR spectroscopy. Polyelectrolyte complexes (PECs) based on TMC and heparin (HP) were prepared at different pHs (5, 8, 10 and 12) and characterized through FTIR spectroscopy, DSC and TGA curves and WAXS profiles. It was verified that the higher the pH of feed solution used for the PEC formation the higher is the thermal stability of PECs. Under basic conditions, the complexation between TMC and HP was more effective and alterations on WAXS profiles of PECs in relation to the precursor (TMC) were clearly observed. In addition, WAXS profiles show that the PEC crystallinity depends on the pH used for the complexation. These results are consistent with the FTIR, DSC, and TGA data. Due to the more intense electrostatic interactions, at higher pHs the unlike polymers chains (TMC and HP) are close enough to produce more stable PECs.

Nanocomposite hydrogel consisting of dispersed montmorillonite-crosslinked maltodextrin-co-dimethylacrylamide (malt-dex-co-DMAAm) as a highly stable device was developed. Carbon–carbon π-bonds issued from glycidyl methacrylate (GMA) were incorporated onto both the MMT (MMT-π) and the malt-dex (malt-dex-π) structures. The nanocomposite copolymer hydrogel was processed via radical crosslinking reaction of malt-dex-π with MMT-π in the presence of DMAAm. The radical reaction of the carbon–carbon π-bonds at the MMT-π was verified by treating the MMT-π with sodium persulfate. There was an excellent dispersion of the MMT-π at the interior of the matrix even after the nanocomposite hydrogel being swollen, demonstrating that the developed methodology can imprint stability of mineral nanoparticles into a porous polymer network preventing diffusion of water-bonded silicate platelets toward the outside matrix. The water absorption profile became more dependent on the polymer relaxation for mineral-loader nanocomposite hydrogels. Higher water absorption had an impact on reduction of elasticity modulus due to softer polymer network in swollen state.

The self-rearrangement of polymer networks based on a polyelectrolyte complex (PN-PEC) resulting from electrostatic interactions between chitosan (CHT) and chondroitin sulfate (CS) was studied in different swelling pH and swelling time conditions. Analysis of the swelling degree and WAXS profiles revealed that the PN-PEC dried sample can self-reorganize depending on both the swelling medium pH and the swelling time. The reorganization is supposed to result from the rearrangement of PN-PEC-forming polymer chains after the release of part of the CS chains, mainly at pH values closer to or higher than the pKa of CHT. This reorganization contributes to increase the crystallinity, thermal stability, and average pore size of the polymer network. This phenomenon makes it possible to treat PN-PEC to obtain some interesting application characteristics.

This contribution describes the absorption percentage of Pb2+ and Cu2+ from water by a superabsorbent hydrogel matrix (SH) made from an anionic polysaccharide copolymerized with acrylic acid (AAc) and acrylamide (AAm). Metal-absorption tests, upon sequential pH variation, indicated that the SH has pH-sensitivity for the absorption of both metals from solution, attributed to the functional ionic groups (COOH) present in the AAc and arabic gum (AG) segments. At the pH 5.0, the SH exhibited good absorption capacity: 73.10% for Pb2+, 81.99% for Cu2+ in water and 63.64% for Pb2+, and 76.67% for Cu2+ in saline water with 0.1 mol kg−1 ionic strength. A replicated 22 full factorial design with a central point was built to evaluate the maximum absorption capacity of the metals into the SH. It was found that both the interaction and main effects of the pH and the initial concentration of metal solution on absorption percentage of the metals were statistically significant. Surface response plots indicated that the absorption capacity of both metals into the SH may be appreciably improved by using the solutions with lower initial concentration of metal and with higher pH values. Metal-absorption results demonstrated that the SH is a convenient material for absorption of Pb2+ and Cu2+ from pure aqueous and saline aqueous environments. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Despite a growing interest in amphiphilic polysaccharide-based diblock copolymers as functional polymeric drug delivery nanosystems, biologically relevant sulfated glycosaminoglycan systems were not yet investigated. Here, we report the synthesis and the self-assembly properties in water of chondroitin sulfate-b-poly(lactic acid) (CS-b-PLA(n)). The CS-b-PLA(n) were synthesized using click-grafting onto method implying reducing-end alkynation of low-molecular weight depolymerized CS (M(w) = 5000 g·mol(-1)) and azide-terminated functionalization of PLAn (M(w) = 6500 g·mol(-1) (n = 46) and M(w) = 1700 g·mol(-1) (n = 20)). The diblock copolymer self-assembled in water giving rise to spherical micelles that were characterized in solution using dynamic/static light scattering and at dry state by TEM technique. In vitro assays on healthy cells showed that at high concentrations, up to 10 μg·mL(-1), CS-b-PLA(n) were noncytotoxic. Those preliminary studies are promising in the perspective to use them as biocompatible nanovehicles for anticancer drug delivery.

The development of superabsorbent hydrogels (SHs) is a very important issue in both academic and industrial fields because of their applications in several technologies. The impressive number of publications dealing with SH confirms this statement: a quick search in the ISI (Web of Science) database under the words superabsorbent hydrogels revealed more than 600 articles published, with about 80% of those published in last decade. Current studies on the development of SHs have focused on the formulation of highly functional materials with enhanced properties for suitable applications in different fields. In light of this, the incorporation of microsized or nanosized materials in SH formulations has been explored as a very attractive strategy for tailoring desired properties. In this review, we discuss relevant aspects of the current knowledge of SHs and nanocomposite polymer hydrogels, mainly those based on chitin and cellulose nanocrystals (fibers and/or whiskers), bringing to light some structure–property relationships and future trends. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39725.

Curcumin (CUR) has been proved to be highly cytotoxic against different tumor cell lines. However, its poor solubility in aqueous medium and fast degradation in physiological pH are the common drawbacks preventing its efficient practical use. Herein, we report the development of original microspheres based on the biopolymer starch crosslinked with N,N-methylenebisacrylamide (MBA) to be applied as an efficient delivering system for CUR. The starch-based microspheres showed high loading efficiency even in loading solution with different CUR concentrations. In vitro release assays data showed that the CUR release is governed by anomalous transport (n = 0.73) and it is pH-dependent. Cytotoxicity assays showed that starch microspheres could improve the cytotoxicity of CUR toward Caco-2 and HCT-116 tumor cell lines up to 40 times than that found for pure CUR. This behavior was attributed to the slowly and sustained release of CUR from the microspheres.

Rice husk ash (RHA), an industrial waste, was incorporated in the preparation of high performance chitosan (CTS) and poly(acrylic acid) (PAA) based superabsorbent hydrogel. Hydrogels filled with RHA previously calcinated at 900 °C (RHA900) showed better water uptake (225 gwater/gabsorbent) than those with husk calcinated at 400 °C (RHA400) (198 gwater/gabsorbent) due to the higher purity and crystallinity, at same composition. The hydrogel composite at 5 wt-% of RHA900 showed the best water uptake (255 gwater/gabsorbent). A clear reduction in swelling degree is observed by increasing the amount of crosslinker from 1 to 3 wt-% due to the increase in the crosslinking density forming more rigid hydrogels. On the other hand, an increase in the initiator amount from 1 to 3 wt-% increased the water uptake due to the formation of greater numbers of active sites increasing the number of PAA chains grafted into CTS backbone. Furthermore, the hydrogel composites presented responsive behavior in relation to both pH and sat solution. The data shows it is possible to obtain high performance materials by incorporating an industrial waste, rice husk ash, in the preparation of hydrogel composites.

A magnetic-field-sensitive modified maltodextrin-based hydrogel (ferrogel) was synthesized. Fourier transform infrared and 13C-CP/MAS NMR spectral analyses confirmed the efficiency of the gelling process. X-ray diffraction analysis revealed the appearance of new crystalline planes in the hydrogel diffractograms after embedding of magnetite nanoparticles. Magnetization curves and Mossbauer analysis revealed that the magnetic hydrogel has a high lattice strain due to bonded iron atom covalence. Moreover, some magnetite molecules embedded in the hydrogel ensure a degree of paramagnetism and iron atoms exhibiting oxidation states alternating between 2 and 3 in the final material. Scanning electron microscopy and energy-dispersive X-ray analysis revealed that no phase separation occurred between the magnetite nanoparticles and crosslinked hydrogel, indicating excellent dispersion throughout the hydrogel. Moreover, the average pore sizes decreased on increasing the amount of magnetite inside the polymer network. The results of compression stress versus strain revealed that the elasticity of the magnetic hydrogel was increased on increasing the amount of magnetite nanoparticles. Finally, kinetic studies revealed that the diffusion mechanism of water in the hydrogel is driven by anomalous release with a tendency towards the occurrence of macromolecular relaxation. Copyright © 2011 Society of Chemical Industry