Low Degree Of Substitution Research Articles

Synthesis of Amorphous Cellulose Derivatives via Michael Addition to Hydroxyalkyl Acrylates for Thermoplastic Film Applications.

The aim of this study is to prepare new cellulose derivatives that show good feasibility and processability. Accordingly, in this study, we demonstrate Michael addition to hydroxyalkyl acrylates, that is, 2-hydroxyethyl and 4-hydroxybutyl acrylates (HEA and HBA, respectively), to synthesize amorphous cellulose derivatives under alkaline conditions. The reactions were carried out in the presence of LiOH in ionic liquid (1-butyl-2,3-dimethylimidazolium chloride)/N,N-dimethylformamide (DMF) solvents at room temperature or 50 °C for 1 h. The Fourier transform infrared and 1H nuclear magnetic resonance (NMR) measurements of the products supported the progress of Michael addition; however, the degrees of substitution (DS) were not high (0.3-0.6 for HEA and 0.6 for HBA). The powder X-ray diffraction analysis of the products indicated their amorphous nature. The cellulosic Michael adduct from HEA with DS = 0.6 was swollen with high polar organic liquids, such as DMF. In addition to swelling with these liquids, the cellulosic Michael adduct from HBA was soluble in dimethyl sulfoxide (DMSO), leading to its 1H NMR analysis in DMSO-d6. This adduct was found to form a cast film with flexible properties from its DMSO solutions. Furthermore, films containing an ionic liquid, 1-butyl-3-methylimidazolium chloride, showed thermoplasticity. The Michael addition approach to hydroxyalkyl acrylates is quite effective to totally reduce crystallinity, leading to good feasibility and processability in cellulosic materials, even with low DS. In addition, the present thermoplastic films will be applied in practical, bio-based, and eco-friendly fields.

Molecular dynamics simulation: Effect of sulfation on the structure of curdlan triple helix in aqueous solution

In this work, by using molecular dynamics simulations, we elucidate the effect of sulfation substitution on the stability of the curdlan triple helix structure. The simulation results indicate that the stability of the triple helix structure is significantly influenced by the sites of sulfation substitution. The substitution at the O2 site directly disrupts the hydrogen bonding network between the triple helix chains, significantly destroying the triple helix conformation. When substitutions occur at both the O4 and O6 sites simultaneously (O4,6), the electrostatic repulsion between numerous sulfate groups introduces considerable energy perturbation to the triple helix, leading to alterations in the glucan chain conformation and consequent destabilization of the triple helix structure. Meanwhile, we find that even if the sulfation substitution is performed at the same substitution sites, the difference in the degree of substitution also has an impact on the triple helix stability. The resistance of the triple helix to sulfation substitution at O2 is weak, and low degree of substitution can lead to the unwinding of the triple helix. However, it demonstrates higher resistance to substitution at O4,6 where only higher degree of substitution results in triple helix destabilization.

Synthesis, characterization, and application of films made from highly substituted N-perfluoroacylated chitosan

Highly substituted perfluoroacylated chitosan can alter the physicochemical properties of chitosan; however, the currently synthesized perfluoroacylated chitosan has a low degree of substitution. In this study, we present a simple method for the homogeneous preparation of highly substituted N-perfluoroacylated chitosan, conducted at room temperature without requiring strict anhydrous or oxygen-free conditions. Various perfluorocarbon chains were successfully attached to chitosan through a reaction between perfluorinated acid esters and amines, catalyzed by DBU. The synthesized N-perfluoroacylated chitosan, with high degree of substitution, demonstrated excellent solubility in common organic solvents. Comprehensive characterization was performed using elemental analysis, nuclear magnetic resonance (including two-dimensional NMR), gel permeation chromatography, infrared spectroscopy, X-ray diffraction, and thermal analysis. The resulting films exhibited high water contact angles. Notably, as the fluorocarbon chain length increased, tensile strength gradually decreased, while elongation at break improved. Additionally, water uptake, water vapor transmission rate, and oxygen transmission rate all exhibited a declining trend. The films exhibited good biocompatibility, and in the grape preservation experiment, HFBC treatment effectively delayed grape aging and deterioration while enhancing quality preservation. These results suggest that HFBC film holds promising potential for food packaging applications.

Impact of the degree of substitution on the enantioseparation of anionic β-cyclodextrin in liquid‒liquid extraction and countercurrent chromatography: Insights from molecular docking simulations

Five types of sulfobutylether-β-cyclodextrin (SBE-β-CD) and carboxymethyl-β-cyclodextrin (CM-β-CD) with different degrees of substitution were synthesized, and six and five racemates were respectively chosen to study the influence of the degree of substitution on the enantioseparation factor. The synthesized SBE-β-CD and CM-β-CD were characterized using 1H NMR spectroscopy and mass spectrometry. The results indicated that the influence of the degree of substitution on enantioseparation for distinct racemates exhibited significant variability. Increasing the degree of substitution of CM-β-CD led to an increasing enantioseparation factor, while SBE-β-CD with a specific degree of substitution provided the optimum enantioseparation factor for some racemates. The optimum enantioseparation factors of N-methyl duloxetine and duloxetine were obtained when a relatively low degree of substitution (DS = 3.5) was selected. And the optimum enantioseparation factor was obtained with a relatively high degree of substitution (DS = 7.5). SBE-β-CD with a low substitution degree of 3.5 was chosen to optimize the countercurrent chromatographic enantioseparation of N-methyl-duloxetine, which resulted in a significant improvement in peak resolution from 0.51 to 0.83. Molecular docking was used to construct three SBE-β-CDs with different degrees and distributions of substitution, and a good agreement was found between the docking results and the experimental results.

Synthesis and characterization of polysaccharide carbamates and mixed carbamates with tunable water solubility

Polysaccharide derivatives with two types of functionalities were synthesized; reactive groups for click-chemistry approaches and groups that can tune the water solubility of the products. Xylan phenylcarbonates (XPCs) and cellulose phenylcarbonates (CPCs) with degrees of substitution (DS) ranging from 0.6 to 3.0 were prepared as starting materials. In a modular synthesis approach, these carbonate derivatives were converted with different amines to obtain functional xylan carbamates (XCs) and cellulose carbamates (CCs) with (i) reactive alkynyl- or furfuryl groups and / or (ii) hydrophilic hydroxyalkyl or tertiary amino groups. Both types of functionalities were introduced separately or simultaneously in a convenient one-pot-approach. Mixed polysaccharide carbamates with low, intermediate, and high DS values (0.6 to 2.5) were successfully prepared and characterized. The water solubility of the carbamates and mixed carbamates was tuned by variation of the type and DS of the two hydrophilic substituents. Surprisingly, some of the products showed lower or upper critical solution temperatures (LCSTs, UCSTs). Thus, the thermoreversible phase transition in aqueous solutions was studied. The products obtained in this work are very promising for the preparation of hydrogels through selective covalent crosslinking as well as for the fabrication of thermoresponsive biomaterials.

Preparation and characterization of acetylated starch/papain composites.

This research aimed to prepare and characterize acetylated starch/papain composites by encapsulating papain within acetylated cassava starch with a low degree of substitution (DS = 0.037) through a stepwise antisolvent precipitation method. The effects of starch concentrations, starch solution volumes, and surfactant types and concentrations were examined. An increase in starch concentration generally enhanced EE, but an excessive concentration led to a decrease in performance due to the aggregation of starch. Furthermore, LC decreased as the starch concentration increased, while the volume of the starch solution primarily influenced LC. Surfactants were employed to disperse the particles and prevent their aggregation during encapsulation, with higher concentrations, particularly of Tween 80, improving both EE and LC but reducing the activity of papain. Optimal results were achieved with a starch concentration of 30 mg mL-1, solution volume of 7 mL, and 3% v/v Tween 80, resulting in an EE of 96.23% and LC of 12.40%. However, the residual papain activity under these conditions dropped to approximately 56%. In contrast, Tween 20 at 1% v/v preserved higher papain activity (87%), although it yielded a lower EE of 69.87% and LC of 9.32%. SEM images revealed that the resulting composite particles had rough, indistinct clusters with surfaces featuring clustered starch nanoparticles. Confirmatory analyses via fluorescence spectra and FTIR confirmed successful entrapment of papain within acetylated starch with a lower degree of substitution.

Synthesis and Ionic Conductivity of Complex Phosphates Li1 + xTi1.8 – xFexGe0.2(PO4)3 with NASICON Structure

Phosphates Li1 + xTi1.8 – xFexGe0.2(PO4)3 (x = 0.1–0.3) with the NASICON structure have been prepared and studied for the first time. It has been shown that co-doping with germanium and iron leads to significant increase in the ionic conductivity of the prepared materials at low degrees of titanium substitution. The influence of the synthesis method (solid-state and sol-gel) and conditions of precursor processing on the ionic conductivity of the materials has been studied. Optimum conditions for the mechanical processing of precursors have been found to obtain ceramics with the highest conductivity. Li1.2Ti1.6Fe0.2Ge0.2(PO4)3 prepared by the solid-state method exhibits the highest ionic conductivity at room temperature (1.7 × 10–4 S/cm) among all samples.

Characterization of methyltetrahydrophthalic anhydride esterified corn starch and their ability in stabilizing Pickering emulsion

Methyltetrahydrophthalic anhydride (MeTHPA) esterified corn starches (MeCS) with degrees of substitution (DS) of 0.0066–0.072 were prepared, characterized and applied to stabilize Pickering emulsion. Fourier transform infrared spectroscopy analysis revealed the presence of a new ester group in MeCS. MeTHPA modification damaged the crystal structure of the corn starch, made its surface structure rough and irregular, and increased its contact angle. These changes were positively correlated with the DS of MeCS. Compared to native corn starch, the particle size of MeCS increased first and then decreased with an increase in DS, the lowest value (4.67 ± 0.08 μm) was observed for MeCS with highest DS (0.072). The stability of Pickering emulsions stabilized by MeCS with a DS of 0.072 was better than those stabilized by MeCS with lower DS (0.0066–0.019), which may attribute to their smaller particle size and higher viscosity. MeCS (DS 0.072) as emulsifiers at a concentration of 3% (w/v) could keep the emulsion stable even after 50 days of storage. This research suggested that MeCS at proper DS and concentration levels may serve as effective particle stabilizers for Pickering emulsions.

Structure and properties of sulfopropyl chitins prepared in NaOH/urea aqueous solutions

A series of sulfopropyl chitins (SCs) with the degree of substitution (DS) ranging from 0.11 to 0.40 and high degree of acetylation (DA ≥ 0.82) were homogeneously synthesized by reacting chitin with sodium 3-chloro-2-hydroxypropanesulfonate (SCHPS) in NaOH/urea aqueous solutions under mild conditions. The structure and properties of SCs were characterized with 1H NMR, CP/MAS 13C NMR, FT-IR, XPS, XRD, elemental analysis, GPC, AFM, ζ-potential and rheological measurements. The mild reaction conditions resulted in less N-deacetylation and uniform structures with substitution occurring predominantly at the hydroxyl groups at C6 of the chitin backbone. The DS value for SC soluble in dilute alkali solution is as low as 0.16. SC exhibited good solubility in distilled water when its DS value reached 0.28. Water-soluble SCs self-assembled in water into micelles by the attractive hydrophobic and hydrogen-bonding interactions between polymer chains. The water-insoluble SC-2 with lower DS could thermally form smart hydrogels at body temperature (37 °C) in physiological condition. Moreover, the SCs exhibited good biocompatibility, making them suitable for biomedical applications.

Cyclodextrin-based tailored polyrotaxanes for highly efficient delivery of the genome-editing molecule

Direct cytosolic delivery of the Cas9 ribonucleoprotein is the most promising method for inducing CRISPR-Cas9 genome editing in mammalian cells. Recently, we focused the movable properties of cyclodextrin-based polyrotaxanes (PRXs), which consist of numerous cyclodextrins threaded onto the axile molecule with bulky endcaps at both ends of the axile molecule, and developed aminated PRXs as multistep transformable carriers for Cas9 ribonucleoprotein, ensuring efficient complexation, cellular internalization, endosomal escape, release, and nuclear localization. This study reports the structural fine-tuning and structure-property relationship of multistep transformable PRXs for more efficient Cas9 ribonucleoprotein delivery. Among various PRXs, PRX derivatives with a longer molecular length (35 kDa polyethylene glycol as the axile molecule) and a low total degree of substitution (1.5 amino groups/α-cyclodextrins), as well as the modified ratio of two modified amines (cystamine and diethylenetriamine) = ≈1:1, exhibited the highest genome-editing efficacy and intracellular dynamics control. These structural properties are important for efficient endosomal escape and Cas9 RNP release. Furthermore, ligand-modified-β-CD, which can endow the ligand through complexation with PRX termini, improved the cellular uptake and genome-editing effects of the optimized PRX/Cas9 RNP in target cells. Thus, structural fine-tuning and the addition of ligand-modified-β-cyclodextrin enabled efficient genome editing by the Cas9 RNP.

Comparative study of rheological properties and Pickering emulsion stabilizing capacity of nonenyl succinic anhydride and octenyl succinic anhydride modified amaranth starches

Functional properties and ability to stabilize Pickering emulsions of amaranth starch with the novel nonenyl succinic anhydride (NSA) modification and the widely used octenyl succinic anhydride (OSA) modification were compared. The NSA modification was more effective in altering the rheological properties of amaranth starches. NSA-modified amaranth starch showed significantly higher peak viscosity (7.13 Pa·s at DS of 0.02209) than the OSA-modified amaranth starch (6.10 Pa·s at DS of 0.03042). The gelatinization temperature, gelatinization enthalpy, and relative crystallinity of amaranth starch were more affected by the OSA than the NSA. The Pickering emulsions stabilized with NSA-modified starches had higher stability than those with the OSA-modified starches as characterized by particle size distribution, morphological, and rheological approaches. A lower degree of substitution by NSA than by OSA is needed to achieve a similar emulsification capacity. Thus, the NSA modification could be an efficient alternative to OSA modification in tailoring physicochemical and rheological functions, as well as stabilizing Pickering emulsions.

Study of the acetylation-induced changes in the physicochemical and functional characteristics of insoluble dietary fiber from wheat bran.

Wheat bran is rich in dietary fiber (DF), particularly insoluble dietary fiber (IDF). Although it was documented the benefits for human health following the consumption of these DFs, its lower water retention capacity and other property still limited their applications. Therefore, the current research investigated the impact of acetylation on the changes in their corresponding physicochemical and functional properties. The current results indicated the acetylated group restricted the alignment of the molecular chains, which led to an increased amorphous phase in the fiber structure, followed by an enhanced thermal sensitivity and a reduced crystallinity as evidenced by X-ray diffraction (XRD). Moreover, the acetylation of the IDFs enhanced the cholesterol absorption capacity, but their corresponding antioxidant capacity and cation exchange capacity were reduced, which might be due to the partial loss of the phenolic compounds onto the polysaccharides during the modification. Interestingly, a lower degree of substitution (DS) of the IDF achieved from water-acetic anhydride modification led to a higher water retention capacity (WRC) and water swelling capacity (WSC). In contrast, a higher DS from acetic anhydride modification demonstrated a greatly improved in vitro hypoglycemic performance of the IDF, including α-amylase inhibitory activity and glucose dialysis retardation index (GDRI), compared to the other samples. This study might highlight a new approach to modify the functionality of the IDFs via the acetylation and it was of great value for designing a novel IDF with hypoglycemic activity. This article is protected by copyright. All rights reserved.

Effects of acetylation, acid-thinning and oxidation on Chrysophyllum albidum (African star apple) kernel native starch

Starch is a biological macromolecule with myriad of industrial uses. The growing need for starch and native starch deficiencies have necessitated researches into under-exploited starch sources and modifications, respectively. Chrysophyllum albidum (African star apple, ASA) seed is a waste consisting of 63.94% carbohydrate in its kernel. Its starch content can be fully utilised, industrially, if it is in a suitable form and its properties understood. That necessitated the isolation of ASA kernel starch, its modification and properties assessment. Acetylation, acid-thinning and oxidation were performed on the native Chrysophyllum albidum kernel starch, NACA, to produce the acetylated Chrysophyllum albidum kernel starch, ACCA, acid-thinned Chrysophyllum albidum kernel starch, ATCA, and oxidised Chrysophyllum albidum kernel starch, OXCA, respectively. The physicochemical properties of the native and modified starches were investigated with established methods. The yield of starch was 43.76%. The acetylated and oxidised starches had low degrees of substitution. FTIR results confirmed the introduction of carbonyl functionality into the acetylated and oxidised starches. Starch morphology revealed smooth, small rounded and truncated ellipsoid granules with diameter ranges of 7–20 μm. Swelling power of modified starches improved, except for the acid-thinned, and increased with temperature. Acetylated and oxidised starches had significantly (p < 0.05) higher water and oil absorption capacities, respectively. Acid-thinning significantly improved starch pasting properties and reduced retrogradation tendency. Modification improved the gelatinisation transition temperature of native starch.

Hemocompatibility of cellulose phosphate aerogel membranes with potential use in bone tissue engineering.

Cellulose is an appealing material for tissue engineering. In an attempt to overcome some obstacles with cellulose II cell scaffolding materials related to insufficient biomineralization, lack of micron-size porosity, and deficiency in surface charge, respective solutions have been proposed. These included covalent phosphorylation of different cellulose materials targeting relatively low degrees of substitution (DS 0.18-0.23) and processing these cellulose derivatives into scaffolding materials by a dissolution/coagulation approach employing the hitherto rarely used TBAF/DMSO/H2O system for cellulose dissolution. Here, we report bioactivity and preliminary hemocompatibility testing of dual-porous cellulose phosphate aerogels (contrasted with the phosphate-free reference) obtained via coagulation (water/ethanol), solvent exchange and scCO2 drying. Deposition of hydroxyapatite from simulated body fluid (7 days of immersion) revealed good bioactivity (1.5-2.2mg Ca2+ per mg scaffold). Incubation of the scCO2-dried and rehydrated scaffolding materials in heparin anticoagulated human whole blood was conducted to study selected parameters of hemostasis (prothrombin F1+2 fragment, PF4, count of thrombocyte-leukocyte conjugates) and inflammatory response (C5a fragment, leukocyte activation marker CD11b). Adhesion of leukocytes on the surface of the incubated substrates was assessed by scanning electron and fluorescence microscopy (DAPI staining). The results suggest that phosphorylation at low DS does not increase platelet activation. However, a significant increase in platelet activation and thrombin formation was observed after a certain fraction of the negative surface charges had been compensated by Ca2+ ions. The combination of both phosphorylation and calcification turned out to be a potent means for controlling the inflammatory response, which was close to baseline level for some of the studied samples.

Fabrication and characterization of O/W emulsion stabilized by Octenyl Succinic Anhydride (OSA) modified resistant starch

Reducing fat content without compromising its sensory qualities is a major technological challenge to the food industry in manufacturing healthy tasty food. Based on the fact that Octenyl Succinic Anhydride (OSA) starch emulsifiers have been successfully applied in food applications for stabilizing oil-in-water (O/W) emulsions, further converting native starch to resistant starch is an attractive alternative which does not require fat reduction but can protect fat droplets against enzymatic digestion. The main purpose of this study was to determine the feasibility of a combined process of debranching and OSA esterification to prepare resistant starch emulsifier for food applications. Following debranching, the resistant starch content of the modified starches markedly increased in comparison with the native starch and reached 43.09% when the enzyme concentration was set at 80 NPUN/g. In contrast, the degree of substitution (DS) of resistant starch was significantly decreased compared with native starch. The resulting resistant starch emulsifier exhibited weaker emulsifying capacity compared to native counterparts, this is caused probably by their lower DS. The environmental stability of resistant starch emulsions has also been investigated and it was observed that these emulsions remained stable after a storage period of 21 days at 4 and 25 °C, respectively however, they showed reduced stability at low pH, increased ionic strength and heat treatment. The overall research study provides useful insights into the utilization of resistant starch emulsifiers in novel food formulations for reduced fat digestion.

Chemical modification and structural analysis of polysaccharide from Solanum tuberdsm

Acetylation, carboxymethylation, sulfation and phosphorylation of polysaccharide from Solanum tuberdsm (STP) were carried out, respectively. Phosphorylated P-STP (P-STP) had the lowest protein content and the highest total carbohydrate content among the four modification products. For degree of substitution (DS), carboxymethylated STP (CM-STP) had the highest DS (0.699), while sulfated STP (S-STP) had the lowest DS (0.211). FT-IR and NMR analysis showed that STP was successfully modified.

Anionic and Ampholytic High-Amylose Starch Derivatives as Excipients for Pharmaceutical and Biopharmaceutical Applications: Structure-Properties Correlations.

Many chemical modifications of starch are realized in organic (mostly methanol) phase, allowing high degrees of substitution (DS). Some of these materials are used as disintegrants. To expand the usage of starch derivative biopolymers as drug delivery system, various starch derivatives obtained in aqueous phase were evaluated with the aim to identify materials and procedures which would generate multifunctional excipients providing gastro-protection for controlled drug delivery. Chemical, structural and thermal characteristics of anionic and ampholytic High Amylose Starch (HAS) derivatives under powder (P), tablet (T) and film (F) forms were evaluated by X-ray Diffraction (XRD), Fourier Transformed Infrared (FTIR) and thermogravimetric analysis (TGA) methods and correlated with the behavior of tablets and films in simulated gastric and intestinal media. At low DS, the HAS carboxymethylation (CMHAS) in aqueous phase, generated tablets and films that were insoluble at ambient conditions. The CMHAS filmogenic solutions, with a lower viscosity, were easier to cast and gave smooth films without the use of plasticizer. Correlations were found between structural parameters and the properties of starch excipients. Compared to other starch modification procedures, the aqueous modification of HAS generated tunable multifunctional excipients that may be recommended for tablets and functional coatings for colon-targeted formulations.

Structural disorder and distribution of impurity atoms in β-Ga2O3 under boron ion implantation

Gallium oxide (Ga2O3) has recently attracted much attention due to the prospect of its application in power electronics and in other areas. An important task is the development of controlled and reproducible methods for doping this material with various impurities, among which boron is of considerable interest. The regularities of Ga2O3 doping with this isovalent (for Ga) impurity are poorly studied. Even for ion implantation as the most common semiconductor doping method these studies are still at the initial stage. In this work, the structural properties of β-Ga2O3 layers upon boron ion irradiation and subsequent annealing have been studied using X-ray Diffraction, Reflection High-Energy Electron Diffraction, Secondary Ion Mass Spectrometry, as well as theoretical calculations from first principles. Among the most interesting results are the establishment of a strong redistribution of implanted boron during post-implantation annealing and the conclusion about low degree of substitution of gallium sites by boron atoms.

Efficient Isolation Method for Highly Charged Phosphorylated Cellulose Nanocrystals.

Phosphorylation of cellulose nanocrystals (CNCs) has remained a marginal activity despite the undisputed application potential in flame-retardant materials, sustainable high-capacity ion-exchange materials, or substrates for biomineralization among others. This is largely due to strenuous extraction methods prone to a combination of poor reproducibility, low degrees of substitution, disappointing yields, and impractical reaction sequences. Here, we demonstrate an improved methodology relying on the modification routines for phosphorylated cellulose nanofibers and hydrolysis by gaseous HCl to isolate CNCs. This allows us to overcome the aforementioned shortcomings and to reliably and reproducibly extract phosphorylated CNCs with exceptionally high surface charge (∼2000 mmol/kg) in a straightforward routine that minimizes water consumption and maximizes yields. The CNCs were characterized by NMR, ζpotential, conductometric titration, thermogravimetry, elemental analysis, wide-angle X-ray scattering, transmission electron microscopy, and atomic force microscopy.

Influence of degree of substitution of octenyl succinic anhydride starch on complexation with chitosan and complex-stabilized high internal phase Pickering emulsions

We analyzed the effects of the degree of substitution (DS) of octenyl succinic anhydride starch (OSA-S) on OSA-S/chitosan complexes and complex-stabilized high internal phase Pickering emulsions (HIPPEs). Because of its low charge density, OSA-S with lower DS weakly interacted with chitosan, forming loosely structured and small-sized complexes. In contrast, OSA-S with higher DS produced complexes four-fold larger in size, with denser structures and enhanced wetting properties. All HIPPEs exhibited gel network structures, and their viscoelasticity and stability significantly increased with increasing DS. This may be related to the enhanced adsorption of the high DS complexes at the oil–water interface, which was verified by the excellent 3D-printing performance of emulsions. Moreover, HIPPEs showed high resistance to heat treatment and ionic strength but were strongly influenced by pH adjustment. Overall, the role of DS in fabrication of HIPPEs was confirmed, and the research for new applications in food industries was motivated.