Carboxymethyl Cellulose:Polyvinylamine Complex Hydrogel Swelling

An efficient wastewater treatment through reduction of organic dyes using Ag nanoparticles supported on cellulose gum beads

This work reports silver nanoparticles (AgNPs) supported on biopolymer carboxymethyl cellulose beads (Ag-CMC) serves as an efficient catalyst in the reduction process of p-nitrophenol (p-NP) and methyl orange (MO). For Ag-CMC synthesis, first CMC beads were prepared by crosslinking the CMC solution in aluminium nitrate solution and then the CMC beads were introduced into AgNO3 solution to adsorb Ag ions. Field emission scanning electron microscopy (FE-SEM) analysis suggests the uniform distribution of Ag nanoparticles on the CMC beads. The X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis revealed the metallic and fcc planes of AgNPs, respectively, in the Ag-CMC catalyst. The Ag-CMC catalyst exhibits remarkable reduction activity for the p-NP and MO dyes with the highest rate constant (kapp) of a chemical reaction is 0.519 and 0.697 min-1, respectively. Comparative reduction studies of Ag-CMC with CMC, Fe-CMC and Co-CMC disclosed that Ag-CMC containing AgNPs is an important factore in reducing the organic pollutants like p-NP and MO dyes. During the recyclability tests, the Ag-CMC also maintained high reduction activity, which suggests that CMC protects the AgNPs from leaching during dye reduction reactions.

Carboxymethyl cellulose-chitosan composite hydrogel: Modelling and experimental study of the effect of composition on microstructure and swelling response

Molecular recognition is essential for the advancement of functional supramolecular natural polymer-based hydrogels. First, a series of carboxymethyl cellulose (CMC)-chitosan (CSN) hydrogels crosslinked with fumaric acid are studied, where the influence of composition on microstructure and swelling is investigated using mathematical modelling and experiment and the hydrolytic properties, microstructure parameters and physicochemical properties are examined. Second, best fit values for the responses are obtained using multiple linear regression and MATLAB R2020a curve fitting and predictive models are generated. Third, the optimum microstructure is loaded with polyethylene glycol (PEG) and bismuth telluride (Bi₂Te₃) and coated on fabric for imparting thermal sensitivity. The results show that (1) optimum microstructure (25.65 ± 1.86 nm mesh size, 116.25 ± 0.00 μmol/cm³ effective crosslinking-density, 348.03 ± 10.81% swelling, and 62.86 ± 1.11% gel fraction) is found at CMC:CSN = 1:3 for G3; (2) the model shows good agreement with experimental data demonstrating potential for estimating hydrogel swelling and microstructure; and (3) G3/PEG and G3/PEG/Bi₂Te₃ enhance thermal conductivity of fabric at ambient, body, and elevated temperatures. The study demonstrates the potential of the generated model in predicting CMC-CSN swelling and G3 as an ideal host matrix for wearable textiles/devices.

Physical gels of poly(vinylamine) by thermal curing

Physical gels are a versatile class of materials which can find application in sensors, electrochemistry, biomedicine or rheological modifiers. Herein, we present a hydrogen-bonded physical gel which is based on the interaction between phenylcarbonate telechelic poly(ethylene glycol) (PEG-PC) and poly(vinyl amine-co-acetamide) (p(VAm-co-VAA)). The critical gelation concentration was found to be 10 wt% by rheology and NMR. UV-vis spectroscopy and dynamic light scattering reveal the formation of aggregates in the gel. Rheology and differential scanning calorimetry (DSC) was used to show the effect of thermal curing on the mechanical properties of the physical gel.

Repeated heating cooling cycles can anneal inhomogeneity in physical gels and significantly improve their mechanical properties.

Chitosan⁻Carboxymethylcellulose-Based Polyelectrolyte Complexation and Microcapsule Shell Formulation

Chitosan (CH)–carboxymethyl cellulose sodium salt (NaCMC) microcapsules containing paraffin oil were synthesized by complex formation, and crosslinked with glutaraldehyde (GTA). The electrostatic deposition of NaCMC onto the CH-coated paraffin oil emulsion droplets was demonstrated by zeta potential and optical microscopy. The optimal process conditions were identified in terms of pH of the aqueous solution (5.5) and CH/NaCMC mass ratio (1:1). Encapsulation of paraffin oil and microcapsule morphology were analyzed by ATR-FTIR and SEM, respectively. The effect of GTA crosslinking on paraffin oil latent heat was investigated by DSC and combined with the values of encapsulation efficiency and core content, supporting the compact shell formation.

Transport of stabilized iron nanoparticles in porous media: Effects of surface and solution chemistry and role of adsorption

Carboxymethyl cellulose (CMC) stabilized zero-valent iron (ZVI) (CMC-ZVI) nanoparticles have been extensively tested for remediation of soil and groundwater. This study investigated effects of iron oxide and aluminum oxide on retention and transport of CMC-ZVI nanoparticles, which have a mean hydrodynamic diameter of 155nm. Column breakthrough experiments showed that the metal oxides coatings on quartz sand greatly enhanced particle retention. A mechanistically sounder transport model was proposed by incorporating a Langmuir-type adsorption rate law into the classic convection-dispersion equation with the adsorption parameters derived from independent experiments. The model allows for a quantitative evaluation of the role of adsorption. While filtration is the primary mechanism for particle retention at lower pore velocities, adsorption becomes more significant at elevated velocities. The presence of 40-80mg-CL^-1 of natural organic matter and high ionic strength (up to 200mM CaCl₂) had negligible effect on the breakthrough profiles of the nanoparticles. Starch, a neutral polysugar stabilizer, was also tested as a stabilizer. Starch-stabilized ZVI nanoparticles, with a mean hydrodynamic diameter of 303nm, displayed a higher particle retention than CMC-ZVI. The information and modeling approach can facilitate our understanding of fate and transport of stabilized ZVI nanoparticles under various geochemical conditions.

BSA/HSA ratio modulates the properties of Ca(2+)-induced cold gelation scaffolds

An effective tissue engineering approach requires adjustment according to the target tissue to be engineered. The possibility of obtaining a protein-based formulation for the development of multivalent tunable scaffolds that can be adapted for several types of cells and tissues is explored in this work. The incremental substitution of bovine serum albumin (BSA) by human serum albumin (HSA), changing the scaffolds' hydrophilic/hydrophobic ratio, on a previously optimized scaffold formulation resulted in a set of uniform porous scaffolds with different physical properties and associated cell proliferation profile along time. There was a general trend towards an increase in hydrophilicity, swelling degree and in vitro degradation of the scaffolds with increasing replacement of BSA by HAS. The set of BSA/HSA scaffolds presented distinct values for the storage (elastic) modulus and loss factor which were similar to those described for different native tissues such as bone, cartilage, muscle, skin and neural tissue. The preferential adhesion and proliferation of skin fibroblasts on the BSA25%HSA75% and HSA100% scaffolds, as predicted by their viscoelastic properties, demonstrate that the BSA/HSA scaffold formulation is promising for the development of scaffolds that can be tuned according to the tissue to be repaired and restored.

Synthesis, characterization, and physical properties of a poly(acrylamide-co-4-cyanobiphenyl-4′-oxyundecylacrylate)

The synthesis and characterization of a copolymer containing an LC unit and a hydrophilic unit are reported. The copolymer forms hydrogel in water with the LC component serving as the physical crosslink.

Controlled root targeted delivery of fertilizer using an ionically crosslinked carboxymethyl cellulose hydrogel matrix

Aims

The recent increases in food prices caused by the corresponding increases in fertilizer costs have highlighted the demand for reducing the overuse of fertilizers in industrial agriculture. There has been increasing interest in developing plant root-targeted delivery (RTD) of fertilizers in order to address the problem of inefficient fertilizer use. The aim of this study is to develop a low cost controlled release device to deliver fertilizers to plant roots and thereby increase fertilizer use efficiency.

Methods

The Root Targeted Delivery Vehicle (RTDV) is formed by dissolving Carboxymethyl Cellulose (CMC) chains in water, mixing it with liquid fertilizer and crosslinking using iron and calcium salts. Basic measurements quantifying nutrient release and green house growth trials were carried out to evaluate fertilizer use efficiency on wheat growing in nutrient depleted soil media.

Results

Growing wheat in nutrient depleted media showed that the RTDV permits a 78% reduction in the amount of fertilizer needed to achieve similar levels of plant yield in these conditions. Quantifying the losses associated with the RTDV synthesis showed that optimizing manufacturing could possibly increase this value as high as 94%. Furthermore, the delivery device showed a similar lifetime in soil to the plant’s growth cycle, delivering fertilizer over the course of the plant’s growth before removal from soil by degradation.

Conclusions

These results illustrate the importance of fertilizer delivery in facilitating absorption and may have potential to vastly increase the use efficiency of fertilizers in soil, resulting in a significant reduction of costs and environmental damage. With more in depth study to quantify the fertilizer release and refine the device, there is great potential for the use of the RTDV as an effective means to increase fertilizer use efficiency in agriculture.

Developing scaffolds for tissue engineering using the Ca2+-induced cold gelation by an experimental design approach

The Ca(2+)-induced cold gelation technique was found suitable to prepare highly porous biodegradable scaffolds based on bovine serum albumin (BSA) and alpha-casein from bovine milk for tissue engineering. A 2(3) full factorial design was used to study the influence and impact of each factor on the several responses of the scaffolds. In vitro degradation (ID), swelling ratio (SR), porosity (PO), and pore size (PS) as well cytotoxicity (CT) were evaluated and shown to be dependent on the pH of sample preparation and on the amount of BSA and casein present, making these scaffolds tunable structures. Under optimized working conditions (4.19% of BSA, 0.69% of Casein, pH 7.07), the ID attained was 37.97%, the SR observed was 11.87, the PO was 82.11%, the PS measured was 180.63 μm at surface, and 175.91 μm at fracture, whereas maximum cell viability was 84% in comparison to controls. Moreover, the scaffold supported cell adhesion and proliferation. These results, consistent with the prediction by the experimental design approach, support the use of this methodology to develop tunable scaffolds for tissue engineering using the Ca(2+)-induced cold gelation.

Hydrogels as drug-delivery platforms: physicochemical barriers and solutions

The properties of hydrogels, in particular their high biocompatibility and water sorption uptake, make hydrogels very attractive in drug delivery and biomedical devices. These favorable features of hydrogels are compromised by certain structural limitations such as those associated with their low mechanical strength in the swollen state. This review highlights the most important challenges that may seriously affect the practical implementation of hydrogels in clinical practice and the solutions that may be applied to overcome these limitations.

Microgel adhesives for wet cellulose: measurements and modeling

Nanostructured adhesive layers were prepared by adsorbing and/or grafting polyvinylamine (PVAm) onto carboxylated poly(N-isopropylacrylamide) (PNIPAM) microgels that were then assembled between layers of wet oxidized cellulose. The wet delamination force was measured as functions of PVAm content, PVAm molecular weight, coverage (mass adhesive/joint area), and the distribution of carboxyl groups in the PNIPAM microgels. The use of microgels is attractive because simple physical adsorption onto the cellulose surfaces before lamination gives much higher adhesive content and strength compared to the corresponding adsorbed linear PVAm. Wet adhesion increased with PVAm content in the microgels and the quantity of microgels in the joint whereas adhesion was independent of PVAm molecular weight. Physical adsorption of the PVAm onto/into the microgels gave the same adhesion as covalently coupled PVAm. Finally, the roles of microgel diameter, elasticity, and coverage were simulated by a simple peel adhesion model in which the microgels were treated as ideal springs.

PVA/PVAm Hydrogel Membranes for Removal of Metal Ions from Aqueous Solution

Glutaraldehyde cross-linked Poly (vinyl alcohol)/Polyvinylamine (PVA/PVAm) membranes for removal of metal ions from aqueous solution were prepared by solution casting and solvent evaporation techniques. The membranes were characterized using XRD, Swelling studies and metal ions adsorption experiments. The results show that PVA/PVAm membranes exhibit semi-crystalline natures as PVA macromolecular, however, the degree of crystallinity of membranes decrease as PVAm increased. The membranes were pH-sensitive and the swelling ability of membranes was significantly enhanced. It was found that the change of swelling behavior versus pH was consistent with the change of degree of ionization versus pH. The amount of Cu2+ions adsorbed increased as PVAm increased as well as increasing pH of solution in the range of 2.5~6.0.

Synthesis and characterization of temperature-sensitive and biodegradable hydrogel based on N-isopropylacrylamide

Based on a biodegradable cross-linker, N-maleyl chitosan (N-MACH), a series of Poly(N-isopropylacrylamide) (PNIPAAm) and Poly(N-isopropylacrylamide-co-acrylamide) [P(NIPAAm-co-Am)] hydrogels were prepared, and their lower critical solution temperature (LCST), swelling kinetics, equilibrium swelling ratio in NaCl solution, and enzymatic degradation behavior in simulated gastric fluids (SGF) were discussed. The LCST did not change with different cross-linker contents. By altering the NIPAAm/Am molar ratio of P(NIPAAm-co-Am) hydrogels, the LCST could be increased to 39°C. The LCST of the hydrogel was significantly influenced by the monomer ratio of the NIPAAm/Am but not by the cross-linker content. In the swelling kinetics, all the dry hydrogels exhibited fast swelling behavior, and the swelling ratios were influenced by the cross-linker content and NIPAAm/Am molar ratios. Equilibrium swelling ratio of all the hydrogels decreased with increasing NaCl solution concentration. In enzymatic degradation tests, the weight loss of hydrogels was dependent on the cross-linker contents and the enzyme concentration.

Controllable aggregation and reversible pH sensitivity of AuNPs regulated by carboxymethyl cellulose

A pH-sensitive gold nanoparticle-cysteamine/carboxymethyl cellulose (Au-CA/CMC) dispersion system was prepared by a simple approach. Gold nanoparticles (AuNPs) were first synthesized by directly reducing chloroauric acid (HAuCl(4)) with sodium carboxymethyl cellulose (CMC). Then the AuNPs were decorated by an electrostatic compound of cysteamine hydrochloride (CA) and sodium carboxymethyl cellulose (CMC) through ligand exchange to get the assembly of Au-CA/CMC. The Au-CA/CMC dispersion system exhibits strongly reversible pH-responsive behavior with the aggregation of AuNPs caused by the combined action of the chain conformation change of CMC and electrostatic interactions between CA and CMC at different pH values. Finally, the reversible aggregation mechanism of AuNPs in the Au-CA/CMC dispersion system has been investigated by transmission electron microscopy (TEM) and ultraviolet-visible spectroscopy (UV-vis spectroscopy). This study provides a new method to fabricate a stimuli-responsive system free from complicated organic synthesis without using a toxic reducing agent.