Degree Of Substitution Research Articles

Hyaluronic acid conjugates of glycine peptides and L-tryptophan

This work reports about the conjugation of glycine C-terminal ethyl and methyl ester peptides and L-tryptophan methyl ester with sodium hyaluronate in aqueous solutions using the peptide coupling agent DMTMM (or short DMT, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methyl-morpholinium chloride). Detailed infrared (IR) absorbance and 1H and 13C (2D) NMR studies (heteronuclear multi-bond correlation spectroscopy, HMBC) confirmed covalent and regioselective amide bonds with the D-glucuronate, but also proves the presence of DMT traces in all conjugates. The ethyl ester`s methyl protons on the peptides` C-terminal could be used to quantify the degree of substitution of the peptide on the hyaluronate scaffold by NMR. The ester group also proved stable during conjugation and work-up, and could in some cases be selectively cleaved in water whilst leaving the amide bond intact as shown by potentiometric charge titration, NMR and IR. The conjugates did not influence the capability of human umbilical vein endothelial cells (HUVECs) to reduce MTS (5-[3-(carboxymethoxy)phenyl]-3-(4,5-dimethyl-2-thiazolyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt) to a formazan dye, which points towards a low cytotoxicity for the obtained products. The conjugation method and products could be tested for tissue engineering gels or drug delivery purposes with alternative, biologically active peptides.

Improving resistant starch content of cassava starch by pulsed electric field-assisted esterification

This study aims to investigate the effect of pulsed electric field (PEF) assisted OSA esterification treatment on the multi-scale structure and digestive properties of cassava starch and structure-digestion relationships. The degree of substitution (DS) of starch dually modified at 1.5–4.5 kV/cm was 37.6–55.3 % higher than that of starch modified by the conventional method. Compared with native starch, the resistant starch (RS) content of esterified starch treated with 3 kV/cm significantly increased by 17.13 %, whereas that of starch produced by the conventional method increased by only 5.91 %. Furthermore, assisted esterification at low electric fields (1.5–3 kV/cm) promotes ester carbonyl grafting on the surface of starch granules, increases steric hindrance and promotes the rearrangement of the amorphous regions of starch, which increases the density of the double-helical structure. These structural changes slow down starch digestion and increase the RS content. Therefore, this study presents a potential method for increasing the RS content of starch products using PEF to achieve the desired digestibility.

Carboxymethyl hemicellulose/sorbitol/gallic acid green composite films for fresh fruit preservation

Fruits are prone to deterioration during transportation and preservation, while conventional packaging materials generally pose a persistent threat to the environment. In the present study, a multifunctional green composite film was developed using solution casting method through the interactions of hydrogen bonds among carboxymethyl hemicellulose, sorbitol, and gallic acid, which was subsequently employed as functional materials for fresh fruit preservation application. In particular, the influence of the degree of substitution (DS) of carboxymethyl hemicellulose on the properties of the composite films was investigated. The results indicated that as the DS increased, the carboxymethyl hemicellulose/sorbitol/gallic acid composite film demonstrated a notable improvement in transmittance, air barrier property, and antibacterial activity. Specifically, the composite film (DS = 0.59) showed a 42.54 % increase in transmittance and a 48.31 % decrease in air permeability compared to the composite film containing hemicellulose (control sample). Furthermore, the composite film (DS = 0.59) displayed a desired inhibition effect against Staphylococcus aureus. Based on the 9-day blueberry preservation test, the composite film (DS = 0.59) exhibited a weight loss rate of 15.36 %, whereas the blank group retained a value up to 20.34 %. In addition, the increased DS was found to lead to the decreased tensile strength but improved elongation at break. Overall, the carboxymethyl hemicellulose/sorbitol/gallic acid green composite films, derived from natural bio-materials and free of environmental concerns, could hold great promise as a novel packaging material for fresh fruit preservation.

Structural relationship of regioselectively-sulfonated botryosphaeran derivatives on activity against herpes simplex virus type 1

The bioactivities of sulfonated polysaccharides are frequently related to their substitution pattern. In this study, the regioselective sulfonation of an exocellular fungal (1→3)(1→6)-β-D-glucan (botryosphaeran) was performed by two different methods: mild sulfonation (MS) and via pivaloyl ester (PS), in order to study the influence of the sulfonation pattern on the antiviral activity of the respective derivatives. Two sulfonated derivatives with substitution degrees of 0.82 (MS) and 0.49 (PS) were obtained, with substitution patterns at positions C-6, and C-2/C-4 of the glucose units, respectively. All derivatives were chemically characterized and evaluated for antiviral activity against Herpes simplex virus type 1 (HSV-1) KOS strain, and dengue type 2 (DENV-2). The sample sulfonated at positions C-6 (MS) showed a remarkable antiviral effect on HSV-1 (IC50 of 5.38 μg mL1), while PS remained inactive. The investigation of the mode of action of sample MS pointed to the inhibition of HSV-1 adsorption to the host cells. Both samples were inactive towards the dengue virus strain. This study demonstrated that the presence of sulfate groups at the C-6 positions of botryosphaeran is the preferred substitution pattern that enables the antiviral activity towards HSV-1.

Effect of Al Substitution on Visible Short-Wave Infrared Reflectance Spectroscopy (VSWIR) of Goethite and Ferrihydrite

Goethite and ferrihydrite are the two major iron hydroxides, essential mineral constituents in the terrestrial surface system. Aluminum (Al) is the most common substituent in iron hydroxides, and it may significantly change the bulk and surficial physicochemical properties of iron hydroxides. Consequently, a practical and convenient approach is needed to efficiently identify the Al substitution degrees of iron hydroxides in natural occurrences. This study presents a comprehensive investigation of the VSWIR characteristics of laboratory-synthesized Al-substituted goethite and ferrihydrite, to establish diagnostic VSWIR parameters for the identification and quantification of Al substitution levels in iron hydroxides. The findings revealed that Al substitution can affect the band positions (P) of goethite and ferrihydrite at ~650 nm, ~900 nm, and ~1400 nm. The relationships between the Al substitution of ferrihydrite and VSWIR parameters can be expressed as P900 = −0.43 × Al(%) + 931 and P1400 = −0.07 × Al(%) + 1428, while that of goethite can be expressed as P650 = 0.42 × Al(%) + 657 and P900 = 2.29 × Al(%) + 936. The peak fitting results showed that the absorption intensity at 480–550 nm linearly decreases with increased Al substitution. The obtained VSWIR spectra of Al-substituted goethite and ferrihydrite provide a critical supplement to the spectral library for (Al) iron hydroxides, and these VSWIR parameters can be utilized for the semi-quantitative determination of Al substitution in natural iron hydroxides

An economic, accessible and stable sulphated cyclodextrin polymer as selector for efficiently separating chiral drugs in HPLC

In this study, sulfopropyl ether β-cyclodextrin polymer (SPE-β-CDP) with simple synthesis steps using cheap reagents was large-scalely prepared. Characterization results showed the average sulfonic group substitution in each β-CD molecule was about 7.261, and there were 195.87 μmol/g β-CD units in polymer. It was low viscosity and produced a little effect on column pressure. It was used as chiral selectors first time to add into mobile phase to separate 13 chiral drugs in HPLC. After investigation, results showed buffer pH, chiral additive concentration, organic phase proportion in mobile phase and flow rate could affect chiral separation. High separation ability of SPE-β-CDP was proved through baseline separation of 12 drugs which attributed to the homogeneity of SPE-β-CDP in sulfonic acid group substitution degree and position. The resolutions of salbutamol, bisoprolol, chlorpheniramine, propranolol and metoprolol could be even up to 7.47–19.02, which were significantly better than that of some references. Separations of 4 chiral drugs were even better than that of CE. Compared with monomer, SPE-β-CDP showed better chiral separation ability. SPE-β-CDP could be used in both of C8 and C18 columns. It was stable in batches and showed good recyclability and reusability. These provided a new strategy for chiral separation.

Polysaccharide‐based H2S donors: Thiol‐ene functionalization of amylopectin with H2S‐releasing N‐thiocarboxyanhydrides

AbstractPolymeric donors of gasotransmitters, gaseous signaling molecules such as hydrogen sulfide, nitric oxide, and carbon monoxide, hold potential for localized and extended delivery of these reactive gases. Examples of gasotransmitter donors based on polysaccharides are limited despite the availability and generally low toxicity of this broad class of polymers. In this work, we sought to create a polysaccharide H2S donor by covalently attaching N‐thiocarboxyanhydrides (NTAs) to amylopectin, the major component of starch. To accomplish this, we added an allyl group to an NTA, which can spontaneously hydrolyze to release carbonyl sulfide and ultimately H2S via the ubiquitous enzyme carbonic anhydrase, and then coupled it to thiol‐functionalized amylopectin of three different molecular weights (MWs) through thiol‐ene “click” photochemistry. We also varied the degree of substitution (DS) of the NTA along the amylopectin backbone. H2S release studies on the six samples, termed amyl‐NTAs, with variable MWs (three) and DS values (two), revealed that lower MW and higher DS led to faster release. Finally, dynamic light scattering experiments suggested that aggregation increased with MW, which may also have affected H2S release rates. Collectively, these studies present a new synthetic method to produce polysaccharide H2S donors for applications in the biomedical field.

Influence of gelatinized octenyl succinic anhydride-modified waxy adlay seed starch on the properties of astaxanthin-loaded emulsions: Emulsion properties, stability and in vitro digestion properties

Octenyl succinic anhydride (OSA)-modified starch is a commonly used food emulsifier and its emulsifying properties are positively correlated with the degree of substitution (DS). However, the maximum concentration of OSA in starch approved by the FDA and the China National Food Safety Standards is 3%. This study aims to enhance the emulsifying properties of OSA-modified waxy adlay seed starch by gelatinization under a limited DS and investigate its use in preparing delivery systems. The gelatinized OSA starch exhibited a more flexible macromolecular structure and better emulsifying activity (20.19 m2/g). The gelatinized OSA starch-stabilized astaxanthin-loaded emulsions showed high retention of astaxanthin (>50%) and long-term stability (56 days). In vitro digestion, the emulsion system showed a protective effect on astaxanthin, and the bioaccessibility of astaxanthin was increased to 16.32%. This study indicated that gelatinization could enhance the emulsifying properties of OSA starch, and this starch-stabilized emulsion was an effective system for astaxanthin.

Hydrophobization of nanofibrillated cellulose from Macaranga gigantea for binding of curcumin

Nanofibrillated cellulose (NFC) has found extensive potential and existing utilizations across various industries. Nonetheless, a notable constraint of NFC lies in its inherent hydrophilic nature, which restricts its suitability for non-aqueous application. This study aims at synthesising hydrophobic NFC through a two-step surface modification by reacting NFC with tannic acid and amine group. The study also investigated the effect of using various alkylamines on the properties of modified NFC. The hydrophobic NFC was characterized using various analytical techniques namely Thermogravimetric Analysis (TGA), X-Ray Diffraction analysis (XRD), Atomic Force Microscopy (AFM), Fourier Transform Infrared Spectroscopy (FTIR), elemental analysis, and contact angle measurements. The present study also looked into the possible use of modified NFC as a pharmaceutical excipient for the delivery of water insoluble curcumin. The analysis of curcumin binding onto the modified NFC was conducted using UV–Visible spectrophotometry. The findings from the study indicated that the modified NFC effectively bound a substantial quantity of curcumin (80 % - 87 %) and the binding varied for samples of different degree of substitution.

Use of simulation to optimize a sweet corn breeding program: implementing genomic selection and doubled haploid technology.

Genomic selection and doubled haploids hold significant potential to enhance genetic gains and shorten breeding cycles across various crops. Here, we utilized stochastic simulations to investigate the best strategies for optimize a sweet corn breeding program. We assessed the effects of incorporating varying proportions of old and new parents into the crossing block (3:1, 1:1, 1:3, and 0:1 ratio, representing different degrees of parental substitution), as well as the implementation of genomic selection in two distinct pipelines: one calibrated using the phenotypes of testcross parents (GSTC scenario) and another using F1 individuals (GSF1). Additionally, we examined scenarios with doubled haploids, both with (DH) and without (DHGS) genomic selection. Across 20 years of simulated breeding, we evaluated scenarios considering traits with varying heritabilities, the presence or absence of genotype-by-environment effects, and two program sizes (50 vs 200 crosses per generation). We also assessed parameters such as parental genetic mean, average genetic variance, hybrid mean, and implementation costs for each scenario. Results indicated that within a conventional selection program, a 1:3 parental substitution ratio (replacing 75% of parents each generation with new lines) yielded the highest performance. Furthermore, the GSTC model outperformed the GSF1 model in enhancing genetic gain. The DHGS model emerged as the most effective, reducing cycle time from 5 to 4 years and enhancing hybrid gains despite increased costs. In conclusion, our findings strongly advocate for the integration of genomic selection and doubled haploids into sweet corn breeding programs, offering accelerated genetic gains and efficiency improvements.

Nanoprecipitation to produce hydrophobic cellulose nanospheres for water-in-oil Pickering emulsions

In recent years, there has been growing interest in replacing petroleum-based water-in-oil (W/O) emulsifiers with sustainable and less toxic natural materials. Pickering emulsifiers are considered well-suited candidates due to their high interfacial activity and the ability to form emulsions with long-term stability. However, only sporadic examples of natural materials have been considered as inverse Pickering emulsifiers. This study describes the synthesis of a series of hydrophobic cellulose nanospheres by bulk modification with acyl groups of different chain lengths followed by nanoprecipitation, and their application as inverse emulsifiers. Modification with acyl groups of longer chain length (C16, C18) afforded lower degrees of substitution, but resulted in greater thermal stability than groups with shorter acyl chains (C12, C14). Formation of nanospheres with low aspect ratios and narrow size distributions required low initial cellulose concentrations (< 1% w/v), high volumetric ratios of antisolvent to solvent (> 10:1), and slow addition rates (< 20 mL/h). The modified cellulose nanospheres were able to reduce the interfacial tension between water and hexane from 45.8 mN/m to 31.1 mN/m, with an effect that increased with the number of carbons in the added acyl chains. The stearate-modified nanospheres exhibited superhydrophobic behavior, showing a contact angle of 156° ± 4° with water, and demonstrated emulsification performance comparable to the commonly used molecular surfactant sorbitan stearate. Our findings suggest that hydrophobically modified cellulose nanospheres have the potential to be a bio-derived alternative to traditional molecular W/O emulsifiers.Graphical

Formulations based on pullulan and a derivative as coating material for the food sector

Carboxymethylated derivatives of pullulan (PU) were synthesized and evaluated as coating for the postharvest preservation of blueberries. Carboxymethylpullulan was obtained by etherification reaction with the substitution degrees of 0.52, 0.34, and 0.26 for CMP1, CMP2, and CMP3 respectively. Infrared spectroscopy and nuclear magnetic resonance results showed characteristic signals of the carbonyl group belonging to the carboxymethyl group. Thermal analysis showed that CMP1, CMP2, and CMP3 derivatives presented thermal stability values of 209.91 C, 214.73 C, and 225.52 °C, respectively, and were lower with respect to PU with Td of 238.84 °C. Furthermore, an increase in the glass transition temperature due to carboxymethylation was determined. The chemical modification decreased the contact angle with respect to PU (71.34°) with values for CMP1, CMP2, and CMP3 of 39.89°, 53.72° and 60.61°, respectively. The carboxymethylation also increased the water vapor permeability and mechanical properties of the films. In addition, it was found that the CMP molecules affected the optical properties. The application of CMP-based coatings reduced the mass loss and ripening rate of blueberries compared to native pullulan, therefore, packaging from CMP molecules could be used as a coating capable of delaying ripening and extending the shelf life of fruits.

Acetylation of cellulose in ethyl acetate: characterization and thin film applications

The study aims to explore the viability of ethyl acetate as a solvent for cellulose acetylation and assess the feasibility of producing films from the acetylated cellulose. Methodologically, the research focused on limited variations in reaction temperature and catalyst amount, specifically two temperatures and four catalyst quantities, while maintaining consistent quantities of EtoAc and acetic anhydride, reaction time, solution concentration, and other factors. The structure and properties of acetylated cellulose were investigated by titration (heterogeneous saponification), viscosity, chemical resistance (solubility), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), proton nuclear magnetic resonance (1H-NMR) and differential scanning calorimetry (DSC). Surprisingly, efficient acetylation in ethyl acetate was achieved with a small catalyst quantity. As the catalyst amount increased, degree of substitution decreased from 2.32 to 0.76. Further investigation involved the production of thin acetate films using the casting method, and evaluating film properties such as ultraviolet (UV) light absorbance, water vapor permeability, tensile strength, and cross-sectional characteristics via scanning electron microscopy (SEM). The films exhibited impressive tensile strengths, reaching up to 76.98 MPa, and demonstrated exceptional transparency. The findings suggest that EtoAc is a suitable solvent for synthesizing cellulose acetate, and adjustments to reaction variables hold the potential to enhance product qualities.

Improved and Highly Reproducible Synthesis of Methacrylated Hyaluronic Acid with Tailored Degrees of Substitution.

Methacrylated hyaluronic acid (HAMA) is a versatile material that has gained significant attention in various pharmaceutical and biomedical applications. This biocompatible material can be photo-cross-linked in the presence of Irgacure 2959 (I2959) to produce hydrogels. Controlling the degree of methacrylation (DM) is crucial since it plays a pivotal role in determining the properties and thus the potential applications of the gels. We report herein a new green approach for the highly controlled and tailored modification of hyaluronic acid (HA) with methacrylic anhydride (MA). The reaction conditions of previously reported procedures were optimized, leading to a decreased reaction time (3 h instead of 24 h) and consumption of fewer equivalents of MA (5 equiv instead of 20) and water as the sole solvent. By changing the amount of base added, HAMA with three different DMs was obtained: 19, 35, and 60%. The influence of the molecular weight of HA, degree of substitution, and concentration of the HAMA solution prior to photo-cross-linking on the rheological, swelling, and degradation properties of HAMA hydrogels was also studied in this work.

Improving thermal stability of starches native cross-linked with citric acid as a compatibilizer for thermoplastic starch/polylactic acid blends

This study aimed to enhance compatibility and thermal stability between thermoplastic starch (TPS) and polylactic acid (PLA) by incorporating citric acid-grafted starch (CA–Starch) at different concentrations (1 and 5%) with varying degrees of substitution for starch derived from sweet potatoes and yams (DY). Blends were produced using a constant TPS/PLA weight ratio of 60:40, both with and without a compatibilizer. The blending process was carried out using a torque rheometer under two distinct conditions. The results exhibited reduced particle sizes in TPS60/PLA40/CA–Starch blends, as evidenced by SEM images displaying improved interaction and smoother surfaces. Significantly, one of the properties that experienced substantial improvement was the compatibility between TPS and PLA, as indicated by reduced phase segregation within the blends. This improvement manifested in enhanced surface morphology, smaller particle sizes, and greater homogeneity in the blends. Additionally, an enhancement in thermal properties, particularly thermal stability, was observed with higher CA content. This study underscores that the incorporation of CA–Starch not only enhances compatibility but also improves thermal stability in TPS60/PLA40 blends, offering potential for the development of biocompatible materials with superior performance.Graphical abstract

Nanoliposomes Permeability in a Microfluidic Drug Delivery Platform across a 3D Hydrogel.

Nanoliposomes are nano-sized vesicles that can be used as drug delivery carriers with the ability to encapsulate both hydrophobic and hydrophilic compounds. Moreover, their lipid compositions facilitate their internalization by cells. However, the interaction between nanoliposomes and the membrane barrier of the human body is not well-known. If cellular tests and animal testing offer a solution, their lack of physiological relevance and ethical concerns make them unsuitable to properly mimic human body complexity. Microfluidics, which allows the environment of the human body to be imitated in a controlled way, can fulfil this role. However, existing models are missing the presence of something that would mimic a basal membrane, often consisting of a simple cell layer on a polymer membrane. In this study, we investigated the diffusion of nanoliposomes in a microfluidic system and found the optimal parameters to maximize their diffusion. Then, we incorporated a custom made GelMA with a controlled degree of substitution and studied the passage of fluorescently labeled nanoliposomes through this barrier. Our results show that highly substituted GelMA was more porous than lower substitution GelMA. Overall, our work lays the foundation for the incorporation of a hydrogel mimicking a basal membrane on a drug delivery microfluidic platform.

Thermal Stability of Amorphous Metal Oxides: The Interplay of Secondary Cations, Degree of Substitution, and Local Structure

Thermal Stability of Amorphous Metal Oxides: The Interplay of Secondary Cations, Degree of Substitution, and Local Structure

Determination of the degree of molar substitution of hydroxypropyl cellulose by gas chromatography

Abstract We have improved the gas chromatography (GC) method with the aid of 1H NMR to determine the degree of molar substitution (MS) of hydroxypropyl cellulose (HPC). This improvement relied on our established dissolution approach for low-substituted HPC, facilitating NMR determination and subsequently expanding the working range of the MS determination from the lower limit of USP specified as 53.4% to 9.3% (MS 0.2). In this method, 2-iodopropane was produced by the reaction of hydroiodic acid with HPC at high-temperature and then measured by GC. 1H NMR was used for the correction of GC method. The MS results via the GC method (MSGC) exhibited a linear correlation with those obtained by the 1H NMR method (MSNMR), with correction equation of MSNMR=1.8026MSGC - 0.2046 (R2 = 0.9979). Method validation results showed that the average recovery and relative standard deviation (RSD) of MS are 103.5% and 0.83%, respectively. Detection limit and quantitation limit were 0.08 and 0.26, respectively. This method is accurate, sensitive with good precision, which is of great value for the production, research and development, and application of HPC, particularly the low-substituted HPC.

Impact of concentration and aging time of pea starch‐based polymeric solutions on the fabrication of electrospun nanofibers

AbstractPolymer concentration and aging time of polymeric solutions are crucial factors that can influence their viscosity, playing an essential role in the fabrication of electrospun nanofibers. Based on this, herein we evaluated the impact of aging time (24 and 48 h) and pea starch concentration (10%, 20%, and 30%, wt/vol) on the polymeric solutions to produce electrospun nanofibers. Solutions were evaluated by rheology, electrical conductivity, and degree of substitution. The nanofibers were analyzed by morphology, size distribution, chemical nature, and thermal properties. The degree of substitution of starches varied from 1.17 to 1.56. Overall, electrical conductivity decreased with increasing starch concentration and aging time of the polymeric solutions. The use of 10% starch displayed a transition from capsules to fibers, while 20% and 30% starch were able to manufacture homogenous, cylindrical, and random nanofibers with diameters varying from 89 to 373 nm. A significant impact of viscosity was not observed; on the other hand, aging time increased the average diameter of nanofibers. Besides, the fabricated nanofibers showed a lower decomposition temperature than raw starch. The fabricated nanofibers have great potential as wall materials for the encapsulation of different compounds and applications in the biomedical and food sectors.

High‐Cerium‐Content Fe–Ce–Nd–B Sintered Magnets with High Coercivity

Ce substitution of Nd in FeNdB sintered magnets is very interesting for reasons of resource efficiency, sustainability and costs. However, the magnetic properties of high Ce‐content magnets are poor. This is mainly due to the lower values of intrinsic magnetic properties of Fe14Ce2B compared to Fe14Nd2B as well as the Laves phase Fe2Ce, which is formed in the grain boundaries and forms flat aggregates for higher Ce‐content. In this article, sintered magnets with 75 at% degree of substitution of the composition Fe70.9–[(Ce1−xLax)0.75Nd0.25]18.8–B5.8–M4.5 (M = Co, Ti, Al, Ga, Cu, 0 ≤ x ≤ 0.3) are produced and analyzed. It is shown that a new rare earth rich grain boundary phase is formed adding La and that the Laves phase fraction can be reduced by up to 85%. With increasing La content, the remanence and Curie temperature increase and the temperature coefficient of Hc improves. A coercivity, remanence, and maximum energy density of up to μ0Hc = 0.74 T, Jr = 0.98 T, and (BH)max = 139.9 kJ m−3 have been achieved.