Cellulose-based hydrogels: Present status and application prospects

Cellulose gel dispersion: From pure hydrogel suspensions to encapsulated oil-in-water emulsions

Cellulose hydrogel particles were fabricated from molecularly-dissolved cellulose/IL solutions. The characteristics of the formed hydrogels (cellulose content, particles' size and porosity) were determined as a function of cellulose concentration in the precursor solutions. There is a significant change in the hydrogel structure when the initial cellulose solution concentration increases above about 7-9%wt. These changes include increase of the cellulose content in the hydrogel, and decrease in its pore size. The finest cellulose particle dispersions can be obtained using low concentration cellulose/IL solutions (cellulose concentration in dispersion less than 2%wt.) or hydrogels (concentration less than 1%wt.) in a dispersing medium consisting of IL with no more than 20%wt. water. Stable paraffin oil-in-water emulsions are achieved by mixing oil and water with cellulose/IL solutions. The optimal conditions for obtaining the finest particles (about 20μm in diameter) are attained using cellulose solutions of concentration between 0.7 and 4%wt. at temperature of 70°C and oil/cellulose mass ratios between 1 and 1.5.

Fabrication of cellulose-based aerogels from waste newspaper without any pretreatment and their use for absorbents

Cellulose-based aerogel (CBA) was prepared from waste newspaper (WNP) without any pretreatment using 1-allyl-3-methyimidazolium chloride (AmImCl) as a solvent via regeneration and an environmentally friendly freeze-drying method. After being treated with trimethylchlorosilane (TMCS) via a simple thermal chemical vapor deposition process, the resulting CBAs were rendered both hydrophobic and oleophilic. Successful silanization on the surface of the porous CBA was verified by a variety of techniques including scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and water contact angle (WCA) measurements. As a result, the silane-coated, interconnected CBAs not only exhibited good absorption performance for oils (e.g., waste engine oil), but also showed absorption capacity for organic solvents such as chloroform (with a representative weight gain ranging from 11 to 22 times of their own dry weight), making them diversified absorbents for potential applications including sewage purification.

Synthesis and characterization of hydroxypropyl methylcellulose-g-poly(acrylamide)/LAPONITE® RD nanocomposites as novel magnetic- and pH-sensitive carriers for controlled drug release

pH-responsive magnetic nanocomposite hydrogels based on hydroxypropyl methylcellulose-g-poly(acrylamide)/LAPONITE® RD (HPMC-g-PAALap) were developed.

Fabrication of biomimetic bundled gel fibres using dynamic microfluidic gelation of phase-separated polymer solutions

Here, we discuss the fabrication of biomimetic bundle-structured gel fibres using a microfluidic device and the rapid cross-linking of a phase-separated polymer blend solution.

Thermoresponsive cryogels reinforced with cellulose nanocrystals

Thermoresponsive cryogels reinforced with cellulose nanocrystals which were either physically entangled or covalently crosslinked into the structure.

Imparting functional variety to cellulose ethers via olefin cross-metathesis

Olefin cross-metathesis (CM) was applied to impart functional variety to a series of cellulose ether derivatives.

A novel cellulose-dioctyl phthate-baker's yeast biosorbent for removal of Co(II), Cu(II), Cd(II), Hg(II) and Pb(II)

In this work, dioctyl phthalate (Dop) was used as a highly plasticizing material to coat and link the surface of basic cellulose (Cel) with baker's yeast for the formation of a novel modified cellulose biosorbent (Cel-Dop-Yst). Characterization was accomplished by Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric analysis (TGA) and Scanning Electron Microscope (SEM) measurements. The feasibility of using Cel-Dop-Yst biosorbent as an efficient material for removal of Co(II), Cu(II), Cd(II), Hg(II) and Pb(II) ions was explored using the batch equilibrium technique along with various experimental controlling parameters. The optimum pH values for removal of these metal ions were characterized in the range of 5.0-7.0. Cel-Dop-Yst was identified as a highly selective biosorbent for removal of the selected divalent metal ions. The Cel-Dop-Yst biosorbent was successfully implemented in treatment and removal of these divalent metal ions from industrial wastewater, sea water and drinking water samples using a multistage microcolumn technique.

Glow discharge electrolysis plasma induced synthesis of cellulose-based ionic hydrogels and their multiple response behaviors

The cellulose-based hydrogel which was prepared through glow discharge electrolysis plasma showed excellent swelling performance and multiple response behaviors.

Hydrophobic and flexible cellulose aerogel as an efficient, green and reusable oil sorbent

We have developed a low-cost, highly absorbent but degradable, green cellulose aerogel. Furthermore, hydrophobic modification was performed efficiently using cold plasma technology.

Advances in cellulose-based superabsorbent hydrogels

This contribution provides a brief overview of recent progress in cellulose-based superabsorbent hydrogels, fabrication approaches, materials and promising applications.

Characterization of the substitution pattern of cellulose derivatives using carbohydrate-binding modules

BACKGROUND

Derivatized celluloses, such as methylcellulose (MC) and hydroxypropyl methylcellulose (HPMC), are of pharmaceutical importance and extensively employed in tablet matrices. Each batch of derivatized cellulose is thoroughly characterized before utilized in tablet formulations as batch-to-batch differences can affect drug release. The substitution pattern of the derivatized cellulose polymers, i.e. the mode on which the substituent groups are dispersed along the cellulose backbone, can vary from batch-to-batch and is a factor that can influence drug release.

RESULTS

In the present study an analytical approach for the characterization of the substitution pattern of derivatized celluloses is presented, which is based on the use of carbohydrate-binding modules (CBMs) and affinity electrophoresis. CBM4-2 from Rhodothermus marinus xylanase 10A is capable of distinguishing between batches of derivatized cellulose with different substitution patterns. This is demonstrated by a higher migration retardation of the CBM in acrylamide gels containing batches of MC and HPMC with a more heterogeneous distribution pattern.

CONCLUSIONS

We conclude that CBMs have the potential to characterize the substitution pattern of cellulose derivatives and anticipate that with use of CBMs with a very selective recognition capacity it will be possible to more extensively characterize and standardize important carbohydrates used for instance in tablet formulation.

New finishing possibilities for producing durable multifunctional cotton/wool and viscose/wool blended fabrics

This research work focuses on the development of a one-bath functional finishing procedure for imparting durable multifunctional properties such as easy care, soft-hand, antibacterial and/or ultra violet (UV) protection to cotton/wool and viscose/wool blends using diverse finishing combinations and formulations. In this study finishing agents such as reactant resin, silicon softeners, 4-hydroxybenzophenone, triclosan, and pigment colorant were selected using magnesium chloride/citric acid as a mixed catalyst and the pad-dry microwave fixation technique. The results reveal that enhancement in the imparted functional properties are governed by type of the finished substrate as well as nature and concentration of finishing formulation components. The finished fabrics still retained high level of functionalities even after 15 consecutive laundering. Surface morphology and composition of selected samples were investigated using scan electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX) analysis. The mode of interactions was also investigated. Practical applications for multifunctionlization of cellulose/wool blended fabrics are possible using these sorts of proper finishing formulations and unique finishing application method.

Synthesis and characterization of hydrogels from cellulose acetate by esterification crosslinking with EDTA dianhydride

Hydrogels were prepared from cellulose acetate with a degree substitution (DS) 2.5 dissolved in dimethylformamide by esterification crosslinking with Ethylenediaminetetraacetic dianhydride (EDTAD) catalyzed by triethylamine. Subsequent conversion of the unreacted carboxyl groups to sodium carboxylates by the addition of aqueous NaHCO3 was performed to enhance the water affinity of the gels. The absorbency of the products was strongly dependent on the amount of EDTAD that was esterified to cellulose acetate, and the highest absorbency was observed for the hydrogel composed of approximately 0.36 molecules of EDTAD per repeat unit of cellulose acetate. The hydrogels were synthesized with different degrees of crosslinking and were analyzed by IR spectral (FTIR), near infrared (NIR), thermogravimetry analysis (TG and DTG), and crosslink density evaluation by Flory-Rehner theory. The hydrogels have synthesized with molar ratios EDTAD/OH groups: [1/1], [1/2], and [0.1/1]. The capacity for water absorbency was studied and compared with the water absorbency of the CA.

The crosslinking of polysaccharides with polyamines and dextran-polyallylamine antibacterial hydrogels

A facile modular approach to rapidly prepare pH-responsive hydrogels by crosslinking polysaccharides with polyamines is demonstrated. Hydrogels are prepared by first reacting the less reactive polysaccharides with the cross-linker epichlorohydrin and completed by the addition of polyamines. The crosslinking of polysaccharides with polyamines provides a facile method for incorporating functionality into polysaccharide based hydrogels. This process is demonstrated with the polysaccharides dextran, pullulan and carboxymethyl cellulose and with the polyamines polyallylamine and polyethylene imine. The hydrogels were characterized by FTIR and swelling studies, which showed pH-dependent swelling due to the presence of the polyamine. The hydrogels can also be tailored by varying the mass ratio between the polysaccharide and polyamine. Absorption studies of organic analytes showed the polyamine content affecting the uptake of a charged substrate (methylene blue) and no effect on a neutral substrate (6-methyl coumarin). This synthetic method was also used to prepare hydrogels with antibacterial activity against E. coli and S. aureus by utilizing an amphiphilic polyallylamine.

Injectable cell constructs fabricated via culture on a thermoresponsive methylcellulose hydrogel system for the treatment of ischemic diseases

Cell transplantation via direct intramuscular injection is a promising therapy for patients with ischemic diseases. However, following injections, retention of transplanted cells in engrafted areas remains problematic, and can be deleterious to cell-transplantation therapy. In this Progress Report, a thermoresponsive hydrogel system composed of aqueous methylcellulose (MC) blended with phosphate-buffered saline is constructed to grow cell sheet fragments and cell bodies for the treatment of ischemic diseases. The as-prepared MC hydrogel system undergoes a sol-gel reversible transition upon heating or cooling at ≈32 °C. Via this unique property, the grown cell sheet fragments (cell bodies) can be harvested without using proteolytic enzymes; consequently, their inherent extracellular matrices (ECMs) and integrative adhesive agents remain well preserved. In animal studies using rats and pigs with experimentally created myocardial infarction, the injected cell sheet fragments (cell bodies) become entrapped in the interstices of muscular tissues and adhere to engraftment sites, while a minimal number of cells exist in the group receiving dissociated cells. Moreover, transplantation of cell sheet fragments (cell bodies) significantly increases vascular density, thereby improving the function of an infarcted heart. These experimental results demonstrate that cell sheet fragments (cell bodies) function as a cell-delivery construct by providing a favorable ECM environment to retain transplanted cells locally and consequently, improving the efficacy of therapeutic cell transplantation.

Biopolymer/Calcium phosphate scaffolds for bone tissue engineering

With nearly 30 years of progress, tissue engineering has shown promise in developing solutions for tissue repair and regeneration. Scaffolds, together with cells and growth factors, are key components of this development. Recently, an increasing number of studies have reported on the design and fabrication of scaffolding materials. In particular, inspired by the nature of bone, polymer/ceramic composite scaffolds have been studied extensively. The purpose of this paper is to review the recent progress of the naturally derived biopolymers and the methods applied to generate biomimetic biopolymer/calcium phosphate composites as well as their biomedical applications in bone tissue engineering.

Olive oil based novel thermo-reversible emulsion hydrogels for controlled delivery applications

Gels have been considered as a popular mode of delivering medicament for the treatment of sexually transmitted diseases (STDs) (e.g. human immunodeficiency virus, bacterial vaginosis, epididymitis, human papillomavirus infection and condylomata acuminata etc.). The present study discusses the development of novel olive oil based emulsion hydrogels (EHs) using sorbitan monopalmitate as the structuring agent. The developed EHs may be tried as drug delivery vehicle for the treatment of STDs. The formation of EHs was confirmed by fluorescence and confocal microscopy. FTIR studies suggested intermolecular hydrogen bonding amongst the components of the EHs. X-ray diffraction study suggested the amorphous nature of the EHs. The developed EHs have shown non-Newtonian flow behavior. The EHs were found to be biocompatible. The formulations were able to effectively deliver two model antimicrobial drugs (e.g. ciprofloxacin and metronidazole), commonly used in the treatment of the STDs.

Chemo-responsive bilayer actuator film: fabrication, characterization and actuator response

A bilayer actuator showing fast and stable curling/uncurling motion was prepared by photo-cross-linking poly(AAm-co-AA)-g-CMC onto PA-6.

Synthesis, characterization and optical studies of highly luminescent ZnS nanoparticles associated with hypromellose matrix as a green and novel stabilizer

ZnS nanoparticles stabilized by a carbohydrate-based matrix, hypromellose (hydroxypropyl methylcellulose) were prepared via a wet chemical method. The nanocomposite was characterized by X-ray diffraction, transmission electon microscopy and Fourier transform infrared spectroscopy. X-Ray diffraction patterns revealed a zinc blende structure. Thermogravimetric analysis suggested that polymer attached to the surface decomposes at 700 °C. Absorption measurements were carried out and calculation of the diameter polydispersity index (DPI) suggests the formation of monodisperse nanoparticles. The optical properties of the as-prepared samples were studied by UV/vis spectroscopy and steady-state photoluminescence (PL) spectroscopy. The PL studies indicate the applicability of these nanoparticles as biocompatible sensors or luminescence markers in future.

Stimuli sensitive super-macroporous cryogels based on photo-crosslinked 2-hydroxyethylcellulose and chitosan

Original pH sensitive cryogels, based on two biodegradable natural polymers chitosan (CS) and 2-hydroxyethylcellulose (HEC), were obtained via cryogenic treatment of semi-dilute aqueous solutions and UV induced crosslinking in frozen state. H₂O₂ and N,N'-methylenebisacrylamide (BisAAm) were used as photoinitiator and crosslinking agent, respectively. BisAAm facilitated the formation of polymer co-network and increased both the gel fraction yield and mechanical strength of cryogels. The influence of chitosan content on the physico-mechanical properties of HEC-CS cryogels was investigated. In general, the increase of CS fraction in the polymer co-network increased the degree of swelling and enhanced significantly the storage modulus of materials. All HEC-CS cryogels obtained were opalescent sponge-like materials, which quickly release/uptake water due to their open porous structure. The incorporation of CS provided pH dependent swelling and good bioadhesive properties of cryogels. HEC-CS cryogels were further exploited as drug delivery systems of the highly water soluble drug metronidazole belonging to BCS Class l.

Synthesis and characterization of photochromic azobenzene cellulose ethers

Photochromic azobenzene cellulose ethers were prepared by homogeneous etherification of cellulose with 2,3-epoxypropoxy-azobenzene (EA) in N,N-dimethylacetamide/lithium chloride solution. The EA with epoxy group could highly efficiently react with cellulose to synthesize 3-azobenzyloxy-2-hydroxypropyl-cellulose (Azo-cellulose) ethers with controllable degree of substitution (DS(azo)). The DS(azo) was in a range of 0.2-2.0 adjusted by the molar ratio of EA to anhydroglucose unit of cellulose. The Azo-celluloses with DS(azo)≥0.53 were soluble in aprotic solvents like dimethylsulfoxide. Their chemical structures and properties were characterized by elemental analysis, FT-IR, NMR, and thermogravimetric analysis. They showed reversible trans-cis-trans transition when Azo-cellulose/DMAc solutions were irradiated by successive irradiation of UV and visible light. The transition between trans- and cis- isomers could be effectively controlled by simply adjusting the irradiation time. The photo-stimulated trans-cis-trans conformational change induced conformation transition between rod-like shape of trans-isomer and skewed shape of cis-isomer.