Cellulose Gel Research Articles

COMPARATIVE STUDIES OF PHYSIC-CHEMICAL PROPERTIES AND STRUCTURE OF COTTON CELLULOSE AND ITS MODIFIED FORMS

Comparative studies of the physicochemical properties and structures of cotton cellulose, microcrystalline cellulose, and nanocellulose were carried out using IR, NMR spectroscopy, X-ray diffraction, thermal analysis in order to identify the dependence "particle size - structure - properties". It was revealed that in the series “cotton cellulose – microcrystalline cellulose – nanocellulose” the degree of polymerization decreases (1200, 230, 110 respectively), the degree of crystallinity increases (66%, 72%, 83% respectively). The IR spectra of microcrystalline cellulose and nanocellulose are characterized by sharp peaks (in the range 1000–1500 cm–1) compared with cotton cellulose. The amount of bound water in gels of microcrystalline cellulose and nanocellulose increases with decreasing particle size, the degree of stability of colloidal systems increases with the transition from microcrystalline cellulose to nanocellulose. Nanocellulose and microcrystalline cellulose have relatively smaller mass loss and relatively large temperature ranges of intensive decomposition and their thermal stability is higher than cotton cellulose. It was found that the periodate oxidation rate of nanocellulose is higher than that of microcrystalline cellulose and cotton cellulose. It was established that microcrystalline cellulose is quantitatively susceptible to periodate oxidation in 7–8 hours, and nanocellulose in 0.5–1 hour.

Electro-Responsive Green Gels for Lower Environmental Impact Shale Gas Extraction

In this work, carbon black (CB) is added in small amounts (3–10% w/w) to green aqueous dispersions based on sodium oleate, guar gum, sodium hyaluronate, or hydroxypropyl cellulose gels to enhance their stability against mechanical and thermal stresses and to provide electric responsiveness to an external voltage. Rheology, optical microscopy, small angle X-ray scattering, and conductivity measurements are performed to compare the properties of CB-enriched formulations to those of pristine dispersions. Our results demonstrate that even small amounts of CB are able to confer interesting physicochemical properties to these formulations: a remarkable increase in the viscosity of at least 1 order of magnitude is observed for all systems even at high temperature (up to 60 °C) upon CB addition, indicating that carbonaceous particles play a structuring role for the polymeric network. Furthermore, the application of an external voltage of 30 V for 60 min to CB-containing formulations imparts a significant electric responsiveness to the systems, allowing the modification of their rheological behavior. The CB-loaded formulations can be recycled at least three times. All these results suggest that CB can be effectively used as an alternative green additive to enhance the mechanical and thermal stabilities of the formulations and that its addition can be a feasible way to easily tune the properties of viscoelastic materials, thereby avoiding the use of toxic or potentially dangerous chemicals. The possibility of achieving remote control of mechanical and thermal properties of viscoelastic formulations significantly expands the horizon of their potential applications, for example, in the field of shale gas extraction.

Structural and rheological characterization of bacterial cellulose gels obtained from Gluconacetobacter genus

This study explores the structural and rheological properties of bacterial cellulose gels (pellicles) produced by bacteria isolated from several kinds of fruits. The three bacteria isolated were identified as Gluconacetobacter sp. and two strains of Gluconacetobacter hansenii. The obtained pellicles were analyzed by Fourier transform infrared spectroscopy, solid-state 13C nuclear magnetic resonance, and X-ray diffraction. On the basis of the structural characterization, the Iα content was approximately 60%, the extent of crystallization was in the range 57–67%, and the crystal sizes were in the range 5.23–5.68 nm. Morphology of the pellicles was observed by scanning electron microscopy. Rheological properties of the pellicles were evaluated using a rheometer. The widths of cellulose fibers and rheological properties were different among the pellicles produced by the mentioned bacteria. Overall, the results obtained in this study indicated that the rheological properties of the BC pellicles were strongly influenced by the network structure of the cellulose fibers rather than by fiber concentrations. Thus, we obtained useful information related to BC pellicle for both basic research as well as for the determination of their potential for application in industries concerning food, cosmetics, and medicine.

Surfactant-assisted fabrication of ultra-permeable cellulose gels with macro channels and insights on regeneration of cellulose from ionic liquids

This work presents a new method to fabricate cellulose gels with micrometer size channels that offer ultra-permeability. A non-ionic surfactant was key to the formation of the macro channels. We studied the chemical microstructure of the [Bmim]Cl (1‑butyl‑3‑methylimmidozolium chloride)-cellulose-surfactant mixtures by Fourier transform infrared spectroscopy (FTIR) imaging system. We then questioned the soft template theory and confirmed our surfactant-induced and diffusion-driven hypothesis to explain the formation of the macro channels. We also found that the microstructure of the gels was impacted by the surfactant, according to nitrogen physisorption, X-ray diffraction, nuclear magnetic resonance, and scanning electron microscopy results. Time-dependent attenuated total reflection-FTIR (ATR-FTIR) was used to monitor the phase separation of the ionic liquid and cellulose in situ during the sol-gel transition. A two-step model of cellulose regeneration was thus proposed. Our study offers a strategy to fabricate hierarchical porous materials with macro channels and can increase the understanding of cellulose regeneration mechanism from ionic liquids.

A mechanically robust, biodegradable and high performance cellulose gel membrane as gel polymer electrolyte of lithium-ion battery

Biodegradable matrixes obtained from natural renewable resources have received increasing attention in the field of gel polymer electrolyte for lithium ion batteries. However, the inferior mechanical property, low uptake ability for liquid electrolytes and the poor lithium ion transference are the obvious drawbacks nowadays. Here, a mechanically robust and environmentally friendly cellulose gel membrane is prepared by the facile solution casting and one-step crosslinking method. This study showed that the GPE based on this cellulose membrane with 5% crosslinker not only possessed good tensile fracture strength of 14.61 MPa, but also presented remarkable electrochemical performance, including high electrolyte uptake of 540%, high ionic conductivity of 6.34 × 10−3 S cm−1, high lithium ion transference number of 0.82 at room temperature, excellent compatibility with lithium electrode and good electrochemical stability. In addition, the assembled cell showed a discharge capacity of 145 mA h g−1 after first cycle at 0.2 C-rate and a high capacity retention of 90% after 50 cycles. We anticipate that this natural polymer membrane will be applied as a high safety, low cost and environmental friendly GPE of lithium-ion batteries.

Bacterial cellulose biopolymer film and gel dressing for the treatment of ischemic wounds after lower limb revascularization.

to evaluate the use of a bacterial cellulose biopolymer film and gel dressing in the treatment of patients with ischemic wounds submitted to lower limb revascularization. we conducted a randomized clinical trial in the Angiology and Vascular Surgery outpatient clinic of the Clinics Hospital of the Federal University of Pernambuco, between January 2017 and December 2018. We followed 24 patients after lower limb revascularization, divided into two groups: Experimental, treated with bacterial cellulose biopolymer film and gel, and Control, treated with essential fatty acids. Patients attended weekly appointments to change dressings and had their wound healing processes evaluated over a period of 90 days. the reduction of the ischemic wounds' areas after 30 days was 4.3cm2 (55%) on average for the experimental group, and the 5.5cm2 (48.5%) for the control group (p>0.05). The complete healing rate at 90 days was 34.8%, 50% in the experimental group and 18.2% in the control group (p=0.053). the bacterial cellulose biopolymer film associated with gel can be used as a dressing in the treatment of ischemic wounds of patients undergoing revascularization of the lower limbs.

Proniosomal gel-mediated topical delivery of fluconazole: Development, in vitro characterization, and microbiological evaluation.

The aim of this study was to explore the potential of proniosomal gel for topical delivery of fluconazole, an antifungal drug used in fungal infections caused by pathogenic fungi. Fluconazole-loaded proniosomal gels were prepared by the coacervation phase separation method using different nonionic surfactants (spans and tweens). The prepared fluconazole proniosomal gels were evaluated for various parameters such as particle size (PS), drug entrapment efficiency percentage (EE%), and in vitro drug release. The experimental results showed that the EE% for the prepared formulae are acceptable (85.14%–97.66%) and they are nanosized (19.8–50.1 nm) and the diffusion from the gels gave the desired sustaining effect. F4, which was prepared from span 60, tween 80 (1:1), and cholesterol showed highest EE% and gave slow release (40.50% ± 1.50% after 6 h), was subjected to zeta potential (ZP) test, transmission electron microscopy as well as microbiological study. The results showed a well-defined spherical vesicle with sharp boundaries with good physical stability of fluconazole within the prepared gel. Moreover, F4 showed an excellent microbiological activity represented by a greater zone of inhibition (5.3 cm) compared to control gel (fluconazole in 2% hydroxy propyl methyl cellulose (HPMC) gel formula) (4.2 cm) and plain gel with no drug (0 cm) against Candida albicans. This study showed the suitability of the proniosomal gel in attaining the desired sustainment effect for topical delivery of fluconazole for the management of fungal infection. The physical stability study showed that there was no significant change in EE%, PS, and ZP of fluconazole proniosomal gel after storage for 6 months.

Influence of synthesized thiourea derivatives as a prolific additive with tris(1,10-phenanthroline)cobalt(II/III)bis/tris(hexafluorophosphate)/ hydroxypropyl cellulose gel polymer electrolytes on dye-sensitized solar cells

An exceptional approach of appending tris(1,10-phenanthroline)cobalt(II)/(III)bis/tris(hexafluorophosphate) and synthesized tetramethyl benzidine-based thiourea derivatives as novel additives with hydroxypropyl cellulose are used to construct a gel polymer electrolyte for DSSC. The thiourea derivatives are synthesized using the cost-effective method. The synthesized derivatives are confirmed by 1H, 13C NMR and mass spectroscopy. The conductivity, surface and redox potential of thiourea derivatives doped Co2+/Co3+ redox electrolytes are scrutinized by impedance spectra, FTIR, UV, XRD. A density functional theory method with full geometry optimization is used to elucidate the adsorption of the symmetrical thiocarbamides on TiO2 (101) surface progressing with electron donating/accepting groups. All the organic compounds display a negative shift on the TiO2 Fermi level simultaneously by adsorption and rebutted as an escalated additive in stable Co(II/III)phen redox electrolyte of the dye-sensitized TiO2 solar cell. This impulse effect influences the sorbate dipole moment component normal to TiO2 surface plane; further, the stable redox mediator and hydroxypropyl cellulose deliver a good performance in a dye-sensitized solar cell. The newly synthesized thiourea derivatives doped Co2+/Co3+ with hydroxypropyl cellulose reports high solar to electric conversion, particularly 1,1'-(3,3′,5,5′-tetramethyl-[1,1′-biphenyl]-4,4′-diyl)bis(3-(3,4,5-trimethoxy phenyl)thiourea) (additive-6) doped redox electrolyte shows an outstanding efficiency (ŋ) of 9.1% under the sunlight irradiation of about 70 mW/cm2.

Effects of bacterial cellulose gel on the anorectal resting pressures in rats submitted to anal sphincter injury

The aim of this study is to evaluate if a gel of bacterial cellulose gel can revert the loss of anal resting pressure after anorectum sphincter injury in rat model, elected as a model to simulate fecal incontinence. Thirty-nine animals were equally divided into three groups: Control (CG), Sphincter injury plus Saline injection (SG) and Sphincter injury plus Bacterial Cellulose Gel injection (BCG). Anal pressure at rest was assessed for all animal in the three groups using anorectum manometry. Saline and Gel groups were subject to anorectum sphincter injury to reduce the anal pressure at rest. Fifteen days later Saline or Gel was injected into the anorectum, according to their groups. Sixty days later first manometry, the anorectum of all animals were removed and processed histologically. The CG group showed maintenance of their mean anorectal resting pressure levels; SG presented a fall in their mean anorectal resting pressure. The BCG presented a significant elevation of the mean anorectal resting pressure levels, surpassing the pressure of CG. The gel of bacterial cellulose remained at the injection site and was neovascularized, colonized by fibroblasts and dense conjunctive tissue. Those data suggest that BC can be used as a future filling agent treatment for fecal incontinence in clinical trial protocols.

Synthesis of polysaccharide hybrid gel in ionic liquids via radiation-induced crosslinking

Recently, our research group reported the first synthesis of polysaccharide chemical gels, conducted in the absence of any crosslinking reagents, using ionizing radiation in carboxylate-based room temperature ionic liquids (RTILs). However, the maximum gel fraction of the cellulose gel produced using this methodology was a poor 14% and furthermore, its mechanical properties were too low to measure and insufficient for practical use as soft gel electrodes. In this work, the production of polysaccharide hybrid gels was investigated in RTILs, using ionizing radiation in an attempt to improve their production yields and mechanical properties. A radiation-crosslinked cellulose/chitosan hybrid gel in a RTIL was obtained, and an increase in the gel fraction was observed with an absorbed dose of up to 80%. The mechanical properties, biodegradability, and thermal stability were measured and found to be sufficient for practical use as soft gel electrodes. The electronic voltage response of the hybrid gel was evaluated in terms of electronic conductivity, curvature, and displacement. The cellulose/chitosan hybrid gel displayed favorable properties in terms of the formation yield and mechanical properties and thus, it is envisaged that this gel will find application in bio-devices and soft actuators.

Formulation and evaluation of oxymetazoline hydrochloride nasal gels

The main intend of the implement sniff out formulate and evaluate oxymetazoline nasal gels. To achieve more persistent blood levels with decrease dosage of medicine by extended drug evidence and by passing hepatic initially cross metabolism and body including inferable disgrace. Mod FTIR & DSC spectra there is not any discrepancein the seam clean medicine, polymers & lipids. The Carbopol consisting of reinforce precail eventual scintillating moreover transparent Poloxamer, Hydroxy Propyl Methyl cellulose gels crop up prospective lucent as a consequence frosted slimy. The pH value of all developed formulations of gels (ONGF1-ONGF8) was in the range of 6.2 to 6.9. Spreadability of gels was in the range 19.51 - 33.91 g.cm/sec, The Viscosity of various formulated gels was found in range of 8628 to 9622 centipoises. The percentage drug content of all prepared gel formulations were found to be in the range of 78.53 to 98.56 %. The gel strength of all prepared formulations of gels was found to be in the range of 69 to 96 %. In-vitro diffusion drug release of Oxymetazoline Hydrochloride of nasal gels ONGF1 shows the 95% drug release. The release order kinetics shows all the formulations ONGF1 to ONGF8 formulations were followed Korsemeyer-Peppas with correlation coefficient R2=0.8969 & 0.2692 respectively. ONGF1 formulation follows both Zero order and Korsmeyer-Peppas models, it indicates diffusion release mechanism followed by non-fickian transport.
 Keywords: Nasal, gels, Oxymetazoline, In vitro diffusion, Carbopol.

On-line rheological characterization of semi-solid formulations

The rheological profile of a semi-solid product is a critical quality attribute. To monitor changes of this attribute during manufacturing, it would be beneficial to measure the rheological parameters in an on-line or in-line mode and implement this as a part of a control strategy for manufacturing of semi-solids. None of the process analytical technology (PAT) tools for measuring the rheological parameters have yet been widely accepted in the pharmaceutical area, as most of the equipment can only measure viscosity. Therefore, an automated system based on the measurement of pressure difference across both a topology optimized channel and a tube geometry (capillary viscometer) was investigated. The Pressure Difference Apparatus (PDA) can sample from the bulk intermediate/product stream and press the sample through the apparatus at different flow rates to yield a frequency sweep (G′ and G″) and a flow curve (viscosity). A calibration model was successfully prepared and verified with hydroxyethyl cellulose gels with polymer content varying from 1.0 to 1.5% (w/w) resulting in gels of different viscosities. The calibration model was used on-line during manufacturing of a gel and manufacturing changes related to dilution of the product were clearly reflected in the batch evolution profiles. The measurements with the PDA reflected the shear rate and frequency ranges relevant for manufacturing and thereby complemented the rheology measurements obtained with a standard rheometer with real time data.

Cellulose and poly(vinyl alcohol) composite gels as separators for quasi-solid-state electric double layer capacitors

Cellulose/poly(vinyl alcohol) (PVA) composite gels are prepared as separators for quasi-solid-state electrical double-layer capacitors (EDLCs) by a simple freeze-thawing method. Fourier-transform infrared spectroscopy, scanning electron microscopy and mechanical testing machine are used to characterize the structure and morphology. Compared with the PVA gel, the as-prepared composite gels show improved network structure and enhanced mechanical properties. The cyclic voltammetric curves, galvanostatic charge/discharge curves, electrochemical impedance spectroscopy and cycling performance of EDLCs with these composite gels are also evaluated. It is found that the EDLC with the optimum composite gel can work in a voltage window of 0–1.8 V and display a specific capacitance of 125.1 F g−1 (based on active carbon on one electrode) at a current density of 1 A g−1. Furthermore, it also has an excellent cycling stability with capacitance retention of ~ 88% after 1500 cycles. These results suggest that the composite gels can serve as a class of promising separators for EDLCs.

Production of hollow-type spherical bacterial cellulose as a controlled release device by newly designed floating cultivation

We developed a novel cultivating system for hollow-type spherical bacterial cellulose (HSBC) gel production without any molds or template. It consisted of floating aqueous medium droplet containing Gluconacetobacter xylinus (G. xylinus) at the boundary of two non-mixed silicone oil layers. The fibrils of bacterial cellulose (BC) were produced at the interface of water and oil phases. Fibril layers effectively thickened layer-by-layer and eventually formed a shell structure. The size of the HSBC gel can be controlled by the volume of dropped cell suspension. For cell suspensions of 50 μL and 10 μL, HSBC gels of approximately 4.0 mm and 2.5 mm were obtained, respectively. The shell of the HSBC gel is the gelatinous membrane formed by well-organized fibril networks; they comprised type-I crystal structure of cellulose. Additionally, we studied release profile of the fluorescein isothiocyanate-dextran (FITC-Dex) and observed that it released rapidly from the HSBC gels compared to from the BC gels obtained by the static culture method. The release behavior from HSBC gel agreed satisfactorily with Higuchi model. Therefore, the shell of HSBC gel is surely a thin gelatinous membrane of BC, and would be useful as a drug release device.

A mussel-inspired approach towards heparin-immobilized cellulose gel beads for selective removal of low density lipoprotein from whole blood

In this study, we report a mussel-inspired approach to fabricate heparin-immobilized cellulose (HeTaCe) gel beads with self-anticoagulative and biocompatible properties which can selectively remove low density lipoprotein (LDL) from whole blood directly. First, a phase inversion technique was applied to prepare cellulose gel beads. Then the as-prepared gel beads were dipped into a mixed solution of heparin and tannic acid in phosphate buffered saline (PBS, pH 8.5) to obtain HeTaCe gel beads. Blood compatibility experiments indicated that the HeTaCe gel beads could suppress complement activation as well as contact activation and prolong the clotting times to the upper detect limits (activated partial thromboplastin time >600 s and thrombin time >180 s) of the automated blood coagulation analyzer. An ideal adsorption capacity of LDL in vitro was achieved by the HeTaCe gel beads with an amount of 79.1 mg/g. Besides, dynamic column adsorption test further demonstrated a selective adsorption of LDL without a significant reduction of high density lipoprotein (HDL) in a simulative hemoperfusion system. It is believed that the HeTaCe gel beads will be quite appealing to future clinical practice aiming at lowering LDL and improving the outcomes of patients with high cardiovascular risk.

Regeneration of cellulose dissolved in ionic liquid using laser-heated melt-electrospinning

A “green” and highly efficient route was proposed to fabricate ultrafine cellulose fibers. The processing steps include cellulose dissolution, gel preparation, melt-electrospinning and fiber coagulation. High DP cellulose can be easily dissolved in 1-butyl-3-methylimidazolium chloride (BmimCl) when the blend was stirred at 110 °C for 2 h. The maximum solubility can reach up to 16.7 wt%. A homogeneous ternary cellulose/BmimCl/ethanol or cellulose/BmimCl/water gel was made by the methods of crystallization and casting for the purpose of fixing the shape of the cellulose/BmimCl solution. After laser-heating and electrospinning, multiple jets were ejected from the gel tip and then frozen on a super cold target. Pure cellulose fibers without beads and blocks were achieved after coagulation. The results of WAXD and FTIR indicated that the regenerated cellulose fibers were amorphous and chemically stable. More importantly, this approach can be applied to other polysaccharides for the preparation of ultrafine fibers.

Activated carbon monoliths derived from bacterial cellulose/polyacrylonitrile composite as new generation electrode materials in EDLC

Bacterial cellulose (BC) gel is synthesized by static culture process at the interface between air and medium. The solvent-exchanged BC gel is incorporated into polyacrylonitrile (PAN) copolymer solution under heating at 90 °C and subsequent cooling gives bacterial cellulose-polyacrylonitrile composite (BC-PAN) monolith. The BC-PAN monolith is carbonized at 1000 °C with physical activation in the presence of CO2 to obtain the activated carbon monolith, BC-PAN-AC, with large surface area and high microporosity. Unique morphologies are observed for BC gel which is propagated to the BC-PAN monolith and restored in BC-PAN-AC. The BC nanofibers remain entwined throughout the porous skeleton of the PAN backbone and the entangled structure helps in retaining the continuity of the matrix of BC-PAN-AC and reduce the grain boundary impedance for electrical conduction. Cyclic voltammetry shows that these activated carbons are good electrode materials in electric double layer capacitors (EDLC) with capability of high-speed charging and discharging.

Cellulose emulsions and their hydrolysis

AbstractBACKGROUNDThe abundance and bio‐renewability of cellulose renders it as a sustainable source for bio‐fuels, yet its potential is not fully exploited. There is current interest in combined enzymatic processes in emulsified systems. Previous work described the formation of a stable non‐crystalline cellulose coating on emulsified oil droplets. This raises significant questions regarding enzyme–substrate interactions in such systems. The aim of this work is to evaluate the ability of the enzyme to attack the cellulose shell on the surface of an oil droplet. This ability is foreseen to be relevant for advanced cellulose conversion processes, such as in the simultaneous extraction of reaction products and/or esterification.RESULTSCellulose amphiphilicity was harnessed to fabricate oil‐in‐water emulsions using aqueous hydrogel dispersion fabricated from conventional alkaline solution. The cellulose shell on the surface of the oil droplets presents a huge non‐crystalline surface. Altering the cellulose/oil ratio effects the emulsion dimensions and the rate of enzymatic hydrolysis, where the conversion of emulsions having lower oil content proved similar to that of regenerated cellulose gels (81 and 77% hydrolyzed cellulose after 4 h, respectively).CONCLUSIONCellulose‐coated oil‐in‐water emulsion droplets are introduced as a novel substrate for cellulose hydrolysis for advanced conversion processes. © 2018 Society of Chemical Industry

The self-assembly and formation mechanism of a novel cellulose gel with chiral nematic structure

Novel cellulose hydrogel with the chiral nematic structure was prepared based on the ionic liquid 1-allyl-3-methylimidazolium chloride ([Amim]+Cl−) as solvent, and the iridescent cellulose aerogel with the chiral nematic structure were prepared through freeze-drying of cellulose hydrogel. Synchrotron X-ray radiation (SAXS and WAXS), polarized optical microscopy and scanning electron microscopy were used to observe the structures and the formation processes of gel, and the formation mechanism of cellulose gel and chiral nematic structure were deduced, thus establishing the model of the hydrogel formation.

Extraction, purification, and structure characterization of polysaccharides from Crassostrea rivularis.

Crude polysaccharide was prepared from Crassostrea rivularis by 30% (w/v) potassium hydroxide solution at 90°C for 120 min. Three fractions (OG1, OG2, and OG3) were purified by DEAE‐52 cellulose and Sepharose 2B gel column chromatography. The chemical structures were determined using gas chromatography (GC), high‐performance gel permeation chromatography (HPGPC), Fourier‐transform infrared (FT‐IR) spectroscopy, and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The results indicated that OG1 was composed of rhamnose and little mannose (8.71%), the ratio of Rha: Gal: Xyl: Fuc in OG3 were 14:5.5:3:1. And their average molecular weights (Mw) were about 1.66 × 106 and 2.33 × 106 Da, respectively. OG2 was composed only of glucose (98.23%), which means it was glycogen. OG2 was consisted mainly of →4)‐ α‐D‐Glc‐(1→, with the branch chain every 6.5 glucose residues on average, which is →4,6)‐α‐D‐Glc‐(1→ and trace amount of α‐D‐Glc‐(1→ branched units. The Mw was 2.27 × 106 Da. It provides the bases for the bioactivity research.