Microcrystalline cellulose and itaconic acid pH sensitive semi interpenetrating network hydrogel for oral insulin delivery

Diabetes mellitus is one of the important causes of death worldwide. Generally, a subcutaneous route is used for insulin administration, but has showed low patient compliance. Extensive research has been conducted to identify molecules capable of delivering insulin orally, for this hydrogel based on microcrystalline cellulose and itaconic acid have been produced and explored. Free radical polymerization as a technique was employed for manufacturing the hydrogels using potassium persulphate as initiator and N, N'-methylene bisacrylamide (NNMBA) as a crosslinker. These pH- sensitive exhibited a swelling capacity of up to 20.38 g/g in distilled water and also revealed stronger swelling in glucose solutions than saline solutions. The pH sensitivity of the hydrogels was confirmed by studying the swelling in different pH solutions. Alkaline solutions showed higher swelling than acidic solutions. SEM established the porous nature, and the structure was examined by FTIR analysis. Thermal degradation was examined using TGA. In vitro release study was done by Bradford assay at 595 nm. The result was further confirmed by in-vivo investigations on male Wistar adult rats and hence is an excellent vehicle for oral insulin administration.

pH-sensitive semi-interpenetrating network of microcrystalline cellulose and methacrylic acid hydrogel for the oral delivery of insulin

Insulin is commonly administered to diabetic patients subcutaneously and has shown poor patient compliance. Due to this, research has been carried out extensively to find molecules that could deliver insulin orally. In this context, a new type of pH-responsive hydrogel, composed of microcrystalline cellulose and methacrylic acid-based hydrogels, has been developed and studied for the oral delivery of insulin. These hydrogels were prepared by free radical polymerization using potassium persulphate as initiator and N, N'-methylenebisacrylamide as a cross-linker. These pH-sensitive hydrogels showed swelling in distilled water as high as 5800 %. The hydrogels were investigated for swelling in saline and glucose solutions, and pH sensitivity was confirmed by swelling in solutions of different pH. The morphological shape was established by SEM, and the structure was analyzed by FTIR. Thermal degradation was investigated by TGA. In vitro release studies have confirmed pH sensitivity, showing lower insulin release at pH 1.2 than at pH 6.8. The encapsulation efficiency was determined to be 56.00 ± 0.04 %. It was further validated by in-vivo investigations for which insulin was loaded into hydrogels and administered orally to healthy and diabetic Wistar rats at 40 IU/kg, showing maximum hypoglycemic effect at 6 h, which was sustained for 24 h. In the stomach's acidic environment, the gels remained unaffected due to the formation of intermolecular polymer complexes. Insulin remained in the gel and was protected from proteolytic degradation. Thus, pH-responsive methacrylic acid-based hydrogels are promising for biomedical applications, especially oral drug delivery.

Thiol-Ene Click Reaction in Constructing Liquid Separation Membranes for Water Treatment

In the evolving landscape of water treatment, membrane technology has ascended to an instrumental role, underscored by its unmatched efficacy and ubiquity. Diverse synthesis and modification techniques are employed to fabricate state-of-the-art liquid separation membranes. Click reactions, distinguished by their rapid kinetics, minimal byproduct generation, and simple reaction condition, emerge as a potent paradigm for devising eco-functional materials. While the metal-free thiol-ene click reaction is acknowledged as a viable approach for membrane material innovation, a systematic elucidation of its applicability in liquid separation membrane development remains conspicuously absent. This review elucidates the pre-functionalization strategies of substrate materials tailored for thiol-ene reactions, notably highlighting thiolation and introducing unsaturated moieties. The consequential implications of thiol-ene reactions on membrane properties-including trade-off effect, surface wettability, and antifouling property-are discussed. The application of thiol-ene reaction in fabricating various liquid separation membranes for different water treatment processes, including wastewater treatment, oil/water separation, and ion separation, are reviewed. Finally, the prospects of thiol-ene reaction in designing novel liquid separation membrane, including pre-functionalization, products prediction, and solute-solute separation membrane, are proposed. This review endeavors to furnish invaluable insights, paving the way for expanding the horizons of thiol-ene reaction application in liquid separation membrane fabrication.

Cellulose levulinate ester as a robust building block for the synthesis of fully biobased functional cellulose esters

Facile modification of cellulose or cellulosic derivatives is one of the important strategies to prepare materials with targeted properties, multifunctionality, thus extending their applications in various fields. Cellulose levulinate ester (CLE) has the structural advantage of acetyl propyl ketone moiety pendant, on which fully biobased cellulose levulinate ester derivatives (CLEDs) have been successfully designed and prepared via aldol condensation reaction of CLE with lignin-derived phenolic aldehydes catalyzed by DL-proline. The structure of CLEDs are featured by a phenolic α,β-unsaturated ketone structure, thus endowing them with good UV absorption properties, excellent antioxidant activity, fluorescence properties and satisfactory biocompatibility. The utility of this aldol reaction strategy, together with the facile tunable substitution degree of cellulose levulinate ester and the diversity of aldehydes, can provide potentially a large spectrum of structurally diverse functionalized cellulosic polymers and create new avenues to advanced polymeric architectures.

Functionality and characterization of modified starch films with pineapple leaf fibers

The objective of this work was to modify banana starch with pineapple leaf fibers (PALF) and its production of biodegradable films. The reaction conditions of the starch modification were a Starch/PALF mass ratio of 50, a time of 1 h and a temperature of 140 °C, to obtain a yield of 41.18 %. Characterization by FTIR and NMR confirmed that the chemical reaction was carried out. XRD and TGA analysis showed that the crystalline zones of the starch were affected during the modification and the product obtained is thermally less stable compared to unmodified starch. The modified starch showed a lower pasting profile compared to the native starch; however, the modified starch showed the ability to form a film. The starch-PALF films were obtained by the casting method and partially characterized. These films presented better mechanical properties compared to the unmodified films. Also, these films could compete with conventional non-biodegradable plastics.

Frontal polymerization-triggered simultaneous ring-opening metathesis polymerization and cross metathesis affords anisotropic macroporous dicyclopentadiene cellulose nanocrystal foam

Multifunctionality and effectiveness of macroporous solid foams in extreme environments have captivated the attention of both academia and industries. The most recent rapid, energy-efficient strategy to manufacture solid foams with directionality is the frontal polymerization (FP) of dicyclopentadiene (DCPD). However, there still remains the need for a time efficient one-pot approach to induce anisotropic macroporosity in DCPD foams. Here we show a rapid production of cellular solids by frontally polymerizing a mixture of DCPD monomer and allyl-functionalized cellulose nanocrystals (ACs). Our results demonstrate a clear correlation between increasing % allylation and AC wt%, and the formed pore architectures. Especially, we show enhanced front velocity (v_f) and reduced reaction initiation time (t_init) by introducing an optimal amount of 2 wt% AC. Conclusively, the small- and wide-angle X-ray scattering (SAXS, WAXS) analyses reveal that the incorporation of 2 wt% AC affects the crystal structure of FP-mediated DCPD/AC foams and enhances their oxidation resistance.

A Review on the Modification of Cellulose and Its Applications

The latest advancements in cellulose and its derivatives are the subject of this study. We summarize the characteristics, modifications, applications, and properties of cellulose. Here, we discuss new breakthroughs in modified cellulose that allow for enhanced control. In addition to standard approaches, improvements in different techniques employed for cellulose and its derivatives are the subject of this review. The various strategies for synthetic polymers are also discussed. The recent advancements in polymer production allow for more precise control, and make it possible to make functional celluloses with better physical qualities. For sustainability and environmental preservation, the development of cellulose green processing is the most abundant renewable substance in nature. The discovery of cellulose disintegration opens up new possibilities for sustainable techniques. Based on the review of recent scientific literature, we believe that additional chemical units of cellulose solubility should be used. This evaluation will evaluate the sustainability of biomass and processing the greenness for the long term. It appears not only crucial to dissolution, but also to the greenness of any process.

Progress on chemical modification of cellulose in “green” solvents

Chemical modification of cellulose in "green" solvents.

Morphology-controllable amphiphilic cellulose microgels made from self-assembly of hydrophobic long-chain bromide-alkylated-cellulose/gelatin copolymer

A cellulose-based microgel is firstly synthesized via chemically coupling gelatin and cellulose, and then amphiphilic cellulose copolymers (HMGC) are prepared by alkylated cellulose-based microgel from different long-chain alkyl groups. The long-chain alkyl group is mainly bonded onto the residual hydroxyl group at C₆ from the AGU of cellulose and the imino groups of gelatin, respectively. The results of self-assembly behavior of HMGC demonstrate that the critical aggregation concentrations of the microgels are in the range from 0.628 to 0.075 mg/mL, and the corresponding hydrodynamic diameters are between 104-1000 nm. Besides, the HMGC can self-assemble into microgels of various morphologies including cotton flocculence, sphere, rod-like, vesicle, flower-like cluster, snowflake-like, urchin-like, and coral shapes. These novel morphologies can be controlled by adjusting the degree of alkylation, the length of the alkyl chain, and the concentration of microgel. Furthermore, the possible formation mechanism of the multiform microgels is proposed from the chain conformation.

Chemically Modified Biopolymers for the Formation of Biomedical Hydrogels

Biopolymers are natural polymers sourced from plants and animals, which include a variety of polysaccharides and polypeptides. The inclusion of biopolymers into biomedical hydrogels is of great interest because of their inherent biochemical and biophysical properties, such as cellular adhesion, degradation, and viscoelasticity. The objective of this Review is to provide a detailed overview of the design and development of biopolymer hydrogels for biomedical applications, with an emphasis on biopolymer chemical modifications and cross-linking methods. First, the fundamentals of biopolymers and chemical conjugation methods to introduce cross-linking groups are described. Cross-linking methods to form biopolymer networks are then discussed in detail, including (i) covalent cross-linking (e.g., free radical chain polymerization, click cross-linking, cross-linking due to oxidation of phenolic groups), (ii) dynamic covalent cross-linking (e.g., Schiff base formation, disulfide formation, reversible Diels-Alder reactions), and (iii) physical cross-linking (e.g., guest-host interactions, hydrogen bonding, metal-ligand coordination, grafted biopolymers). Finally, recent advances in the use of chemically modified biopolymer hydrogels for the biofabrication of tissue scaffolds, therapeutic delivery, tissue adhesives and sealants, as well as the formation of interpenetrating network biopolymer hydrogels, are highlighted.

Alginate modification via click chemistry for biomedical applications

Alginate biopolymers are characterized by favorable properties, of biocompatibility, degradability, and non-toxicity. However, the poor stability properties of alginate have limited its suitability for diverse applications. Recently, click chemistry has generated significant research interest due to its high reaction efficiency, high selectivity for a single product, harmless byproducts, and processing simplicity. Alginate modified using click chemistry enables the production of alginate derivatives with enhanced physical and chemical properties. Herein, we review the employment of click chemistry in the development of alginate-based materials or systems. Various click chemistries were highlighted, including azide and alkyne cycloaddition (e.g. Copper-(I)-catalyzed azide-alkyne cycloaddition (CuAAC), Strain-promoted alkyne-azide cycloaddition (SPAAC)), Diels-Alder reaction (Inverse electron demand Diels-Alder (IEDDA) cycloaddition, Tetrazine-norbornene Diels-Alder reactions), Thiol-ene/yne addition (Free-radical thiol-ene addition click reactions, Thiol-Michael addition click reactions, Thiol-yne addition click reaction), Oxime based click reactions, and other click reactions. Alginate functionalized with click chemistry and its properties were also discussed. The present study shows that click chemistry may be employed in modifying the mechanical strength, biochemical/biological properties of alginate-based materials. Finally, the applications of alginate-based materials in wound dressing, drug delivery, protein delivery, tissue regeneration, and 3D bioprinting were described and the future perspectives of alginates modified with click chemistry, are subsequently presented. This review provides new insights for readers to design structures and expand applications of alginate using click chemistry reactions in a detailed and more rational manner.

Viscoelasticity and Solution Stability of Cyanoethylcellulose with Different Molecular Weights in Aqueous Solution

Water-soluble cellulose ethers are widely used as stabilizers, thickeners, and viscosity modifiers in many industries. Understanding rheological behavior of the polymers is of great significance to the effective control of their applications. In this work, a series of cyanoethylcellulose (CEC) samples with different molecular weights were prepared with cellulose and acrylonitrile in NaOH/urea aqueous solution under the homogeneous reaction. The rheological properties of water-soluble CECs as a function of concentration and molecular weight were investigated using shear viscosity and dynamic rheological measurements. Viscoelastic behaviors have been successfully described by the Carreau model, the Ostwald-de-Waele equation, and the Cox–Merz rule. The entanglement concentrations were determined to be 0.6, 0.85, and 1.5 wt% for CEC-11, CEC-7, and CEC-3, respectively. All of the solutions exhibited viscous behavior rather than a clear sol-gel transition in all tested concentrations. The heterogeneous nature of CEC in an aqueous solution was determined from the Cox–Merz rule due to the coexistence of single chain complexes and aggregates. In addition, the CEC aqueous solutions showed good thermal and time stability, and the transition with temperature was reversible.

A flexible Cellulose/Methylcellulose gel polymer electrolyte endowing superior Li+ conducting property for lithium ion battery

With the advent of gel polymer electrolyte (GPE), a series of safety problems of lithium ion batteries have been resolved. However, poor self-standing property, the low ionic conductivity and Li⁺ transference number are still the obstacles that impede the practical application of GPE. Herein, a flexible and eco-friendly GPE is designed using allyl-modified cellulose with methylcellulose through simple UV curing. The crosslinked structure facilitates the integrity of GPE during use, and methylcellulose guarantees the high affinity to liquid electrolyte and improve interfacial compatibility. The specific polar functional groups (OH, OCH₃ and COC) in GPE cooperate to enhance the lithium salt dissociation, anion immobilization and lithium ion transporting and enable the high Li⁺ transference number (0.902) and ion conductivity (4.36 × 10^-3 S cm^-1). The assembled Li/GPE/LiFePO₄ coin cells possess high initial discharge capacity of 150.6 mA h g^-1 and a high capacity retention of 91.6 % after 100 cycles.

Development of microcrystalline cellulose based hydrogels for the in vitro delivery of Cephalexin

Three hydrogels namely, microcrystalline cellulose (MCC), microcrystalline cellulose-carboxymethyl cellulose (MCC-CMC) and microcrystalline cellulose-xylan (MCC-xylan) are synthesized using ethylene glycol diglycidyl ether as crosslinker. For the chemical characterization, FT-IR spectroscopy is adopted, whereas gel fraction and swelling ratio are used for the physical characterization of the hydrogels. Coarse morphology of hydrogels is further visualized by microscopic observation. The rheological characterization proves that MCC-CMC gel withstands higher strain to resist permanent deformation than the other two gels. The hydrogels are used for the loading and in vitro release of Cephalexin. The in vitro delivery is carried out in various simulated body fluids such as phosphate buffer saline (PBS), artificial intestinal fluid (AIF) and artificial gastric fluid (AGF). MCC-CMC is observed to deliver Cephalexin individually 15% in AGF, 86% in AIF, 98% in PBS and 98% in consecutive buffers (AGF followed by AIF and PBS).

Photo-reduction of Ag nanoparticles by using cellulose-based micelles as soft templates: Catalytic and antimicrobial activities

Amphiphilic cellulose derivatives were synthesized from allyl cellulose (AC) and cystein (Cys)/n-dodecyl mercaptan (NDM) via the thiol-ene click reactions. The derivatives were self-assembled into micelles in distilled water, and the micelles sizes increased with an increase of the DS_NDM. The amphiphilic cellulose micelles were served as the soft templates for the controllable synthesis of Ag nanoparticles (NPs) through the photo-reduction. Ag NPs were embedded and stabilized by the amphiphilic cellulose micelles, and their sizes increased from 3.1 to 14.4 nm with an increase of the original template sizes. The catalytic properties of the Ag-loaded micelles were evaluated by the reduction of p-nitropheonl to p-aminophenol. The results demonstrated that the Ag-loaded micelles exhibited excellent catalytic activity. The reduction followed the first-order rate law, and the reaction constant decreased with increasing size of Ag NPs. Moreover, the Ag-loaded micelles displayed good antimicrobial activities to both S. aureus and E. coli. Therefore, the Ag-loaded cellulose-based micelles have potential applications in various fields.

Pharmaceutical Applications of Cellulose Ethers and Cellulose Ether Esters

Cellulose ethers have proven to be highly useful natural-based polymers, finding application in areas including food, personal care products, oil field chemicals, construction, paper, adhesives, and textiles. They have particular value in pharmaceutical applications due to characteristics including high glass transition temperatures, high chemical and photochemical stability, solubility, limited crystallinity, hydrogen bonding capability, and low toxicity. With regard to toxicity, cellulose ethers have essentially no ability to permeate through gastrointestinal enterocytes and many are already in formulations approved by the U.S. Food and Drug Administration. We review pharmaceutical applications of these valuable polymers from a structure-property-function perspective, discussing each important commercial cellulose ether class; carboxymethyl cellulose, methyl cellulose, hydroxypropylcellulose, hydroxypropyl methyl cellulose, and ethyl cellulose, and cellulose ether esters including hydroxypropyl methyl cellulose acetate succinate and carboxymethyl cellulose acetate butyrate. We also summarize their syntheses, basic material properties, and key pharmaceutical applications.

Conformation of Methylcellulose as a Function of Poly(ethylene glycol) Graft Density

Low molecular weight thiol-terminated poly(ethylene glycol) (PEG) (M ≈ 800) has been grafted onto a high molecular weight methylcellulose (MC, M_w ≈ 150000) by a facile thiol-ene click reaction; graft densities varied from 0.7% to 33% (grafts per anhydroglucose unit). Static and dynamic light scattering reveals that the overall radius of the chain increases systematically with graft density, in a manner in excellent agreement with theory. As the contour length remains unchanged, it is apparent that grafting leads to an increase in the persistence length of this semiflexible copolymer, by as much as a factor of 4. These results represent the first experimental verification of the excluded volume theory at low grafting densities, and demonstrate a promising synthetic platform for systematically increasing the persistence length of a model semiflexible, water-soluble polymer.

Improved Performance of Recombinant Protein A Immobilized on Agarose Beads by Site-Specific Conjugation

Protein A affinity adsorbent with high antibody-binding capacity plays a prominent part in the purification of biopharmaceuticals to decrease the manufacturing costs. We describe a site-specific covalent conjugation strategy for protein A to immobilize on agarose beads. Recombinant protein A, which has one cysteine introduced at the C terminus through genetic engineering technology, was immobilized site-specifically on maleimide-functionalized agarose beads by the thiol-maleimide reaction. As a comparison, the recombinant protein A was randomly immobilized on the aldehyde-functionalized agarose beads via free amino groups on the protein surface. The site-specific conjugation of recombinant protein A on the agarose beads was validated through the assay of free SH groups on the adsorbents using the Ellman's reagent. Adsorbents containing various amounts of protein A were used to adsorb antibody from human plasma. Analysis of immunoturbidimetry showed that the adsorbed fractions contained the 90.1% IgG, 4.2% IgA, and 5.7% IgM. The maximal antibodies-binding capacities with static adsorption and dynamic adsorption were approximately 64 and 50 mg, respectively, per swollen gram for site-specifically conjugated adsorbent and 31 and 26 mg for randomly conjugated adsorbent. Remarkably, the high antibody-binding capacity for site-specifically conjugated adsorbent outperformed the existing commercial protein A Sepharose (approximately 30 mg/g). The orientation of a protein is crucial for its activity after immobilization, and these results demonstrate that the site-specifically conjugated protein molecule is in a functionally active form to interact with the antibody with weak steric hindrance. The proposed approach may be an attractive strategy to synthesize affinity adsorbents with high-binding capacity.

Epichlorohydrin-Cross-linked Hydroxyethyl Cellulose/Soy Protein Isolate Composite Films as Biocompatible and Biodegradable Implants for Tissue Engineering

A series of epichlorohydrin-cross-linked hydroxyethyl cellulose/soy protein isolate composite films (EHSF) was fabricated from hydroxyethyl cellulose (HEC) and soy protein isolate (SPI) using a process involving blending, cross-linking, solution casting, and evaporation. The films were characterized with FTIR, solid-state (13)C NMR, UV-vis spectroscopy, and mechanical testing. The results indicated that cross-linking interactions occurred in the inter- and intramolecules of HEC and SPI during the fabrication process. The EHSF films exhibited homogeneous structure and relative high light transmittance, indicating there was a certain degree of miscibility between HEC and SPI. The EHSF films exhibited a relative high mechanical strength in humid state and an adjustable water uptake ratio and moisture absorption ratio. Cytocompatibility, hemocompatibility and biodegradability were evaluated by a series of in vitro and in vivo experiments. These results showed that the EHSF films had good biocompatibility, hemocompatibility, and anticoagulant effect. Furthermore, EHSF films could be degraded in vitro and in vivo, and the degradation rate could be controlled by adjusting the SPI content. Hence, EHSF films might have a great potential for use in the biomedical field.