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Successful bone fragment fixation is a crucial factor in bone fracture healing, the fixation of crushed bone fragments could hinder bone fracture healing. Thus, ideal bone glues to effectively adhere and splice comminuted bone fragments are needed in clinical. Herein, an osteoinductive and biodegradable double cross-linked bone glue (GelMA-oDex-AMBGN) was constructed through Schiff's base reaction between commercial GelMA (with different substitution degrees of amino groups) and Odex mixed with amine-modified mesoporous bioactive glass nanoparticles (AMBGN), followed by crosslink with blue light irradiation. The GelMA-oDex-AMBGN bone glue successfully adhered and spliced the comminuted bone fragments of isolated rat skulls. GelMA-oDex-AMBGN promoted the proliferation of 3T3 cells and enhanced the expression of osteogenic proteins Runx2 and OCN in vitro. In rat cranial critical-sized defect models, GelMA-oDex-AMBGNs with different substitution degrees significantly increased the new bone contents at the fracture defect sites and promoted bone tissue regeneration in vivo. In conclusion, the double cross-linked bone glue (GelMA-oDex-AMBGN) was successfully constructed and can induce bone regeneration. Additionally, there was no significant difference in osteogenic activity among GelMA-oDex-AMBGNs with different substitution degrees and the equal content of AMBGN. [ABSTRACT FROM AUTHOR]

In this study, chitosan (CS) was conjugated with epicatechin gallate (ECG) to prepare CS-ECG conjugates with different substitution degrees (5.18 %, 6.36 % and 7.74 %). Then, antioxidant packaging films were fabricated by blending CS and CS-ECG conjugates. The impact of CS-ECG conjugates' substitution degree on the functionality of CS/CS-ECG films was determined. CS-ECG conjugates showed UV absorption at 275 nm, proton signal at 6.85 ppm and infrared absorption at 1533 cm−1, assigning to the conjugated ECG. As compared with CS, CS-ECG conjugates exhibited less crystalline state but higher antioxidant activity. The structural characterization of CS/CS-ECG films showed CS and CS-ECG conjugates formed hydrogen bonds. CS/CS-ECG films displayed 26.35 %–29.23 % water solubility, 85.61°–86.96° water contact angle, 3.11–3.41 × 10−11 g m−1 s−1 Pa−1 water vapor permeability, 0.29–0.34 cm3 mm m−2 day−1 atm−1 oxygen permeability, 31.54–36.20 MPa tensile strength, 50.12 %–56.40 % elongation at break, as well as potent antioxidant activity and oil oxidation inhibitory ability. Notably, the film containing CS-ECG conjugate with 7.74 % substitution degree had the strongest barrier ability, mechanical property, antioxidant activity and oil oxidation inhibitory ability. Results suggested the substitution degree of CS-ECG conjugates was positively correlated with the barrier, mechanical and antioxidant properties of CS/CS-ECG films. • Chitosan (CS) was reacted with epicatechin gallate (ECG) to prepare conjugates. • Antioxidant packaging films were fabricated based on CS and CS-ECG conjugates. • ECG changed the crystallinity, morphology and antioxidant activity of CS. • CS-ECG conjugates improved the barrier, mechanical and antioxidant activity of films. • The substitution degree of conjugates positively affected the functionality of films. [ABSTRACT FROM AUTHOR]

The modification of the biobased polymer chitosan is a broad and widely studied field. Herein, an insight into the hydrophobization of low-molecular-weight chitosan by substitution of amino functionalities with hexanoyl chloride is reported. Thereby, the influence of the pH of the reaction media was investigated. Further, methods for the determination of the degree of substitution based on 1H-NMR, FTIR, and potentiometric titration were compared and discussed regarding their accuracy and precision. 1H-NMR was the most accurate method, while FTIR and the potentiometric titration, though precise and reproducible, underlie the influence of complete protonation and solubility issues. Additionally, the impact of the pH variation during the synthesis on the properties of the samples was investigated by Cd2+ sorption experiments. The adjusted pH values during the synthesis and, therefore, the obtained degrees of substitution possessed a strong impact on the adsorption properties of the final material.

The present study has been carried out to consider the effect of acetylation conditions and type of bleached pulps [Kraft and SO2–ethanol–water (SEW) pulps] on the properties of obtained cellulose acetates (CA) and their films. The acetylation reaction in the absence of solvent was performed by using acetic anhydride and iodine as a catalyst. The efficiency of acetylation and the degree of substitution, crystallinity, transparency, tensile strength, young modulus, differential scanning calorimetry, water vapor permeability (WVP), scanning electron microscope and atomic force microscopy images were studied. The results showed that the while the Young's modulus and transparency increased by up to 8% of the catalyst due to the increase in iodine charge; higher iodine levels led to embrittlement of the film. The increase in the ratio of acetic anhydride to pulp (A:P) from 10:1 to 20:1 with 4% catalyst led to a reduction of the DS by 8–10%, the crystallinity by 25%, the Young's modulus by 13–25%, and transparency by 1–34% of a CA obtained from SEW and Kraft pulp, respectively. With the use of higher amounts of the catalyst (8%) and a ratio of A:P equal to 20:1, all properties of CA were suitable for film preparation. WVP of films from Kraft pulp and SEW pulp showed a decrease of about 8.5% and 18% respectively when increasing the iodine amount from 4 to 8% in acetylation. The tensile strength of CA films was initially increased by enhancing the amount of iodine, but then reduced in a similar way to other properties. The condition of acetylation can be adjusted to produce a high-quality CA film according to the characteristics of the pulp used as raw material. [ABSTRACT FROM AUTHOR]

Superabsorbent polymers (SAPs) based on polysaccharides, especially alginate, could offer a valuable solution in a plethora of applications going from drug delivery to self-healing concrete. This has already been proven with both calcium alginate and methacrylated alginate combined with acrylic acid. In this manuscript, the effect of varying the degree of methacrylation and use of a combination of acrylic acid and acrylamide is investigated to explore the effects on the relevant SAP characteristics. The materials showed high gel fractions and a strong swelling capacity up to 630 g water /g SAP , especially for superabsorbent polymers with a low degree of substitution. The SAPs also showed only a limited hydrolysis in aqueous and cement filtrate solutions. [ABSTRACT FROM AUTHOR]

Sucrose polyester (SPE) is a carbohydrate ester compound that has diverse functions, from surfactant to low-calorie food products. Sucrose fatty acid ester with the degree of substitution 1-3 can be used as emulsifier in foods and cosmetics. The enzymatic synthesis of sucrose polyesters can be carried out using lipase in organic solvent and contain small amount of water. In these studies sucrose esters were synthesized by esterification reaction between sucrose with fatty acids from coconut and palm oil using Candida rugosa lipase in n-hexane. Optimization esterification reaction carried out for parameters of incubation time, temperature, and the ratio of the substrate. The optimum incubation time is at 18 hours for coconut oil and 12 hours palm oil, the optimum temperature is 30 oC for coconut and palm oil, and the mole ratio of fatty acid to sucrose is 40:1 for coconut oil and 64:1 for palm oil. Esterification products were characterized by FT-IR. The FT-IR spectrum showed the ester bond was formed as indicated by the wave number 1739.79/cm. Esterification products have 2 substitution degrees.

Substitution degree (DS) of carboxymethylcellulose (CMC) is one of the critical internal factors for affecting CMC interacting with other polyelectrolytes. The assembly of lysozyme (Ly) and CMC with various DS were analyzed with turbidities, zeta potentials, intrinsic fluorescence, Fourier transform infrared spectra and circular dichroism. It was found that the electrostatic interactions were weakened with decreasing the ratio for Ly and CMC in the Ly-CMC complexes because of the increasing electrostatic repulsion of CMC itself. Electrostatic attractions were also reduced at neutral or alkaline pH and high salt concentration. In addition, electrostatic attractions were much stronger between Ly and CMC with higher DS. CMC with higher DS value can resist the decomposition of Ly-CMC more effectively. Our work provides a new insight for understanding the interactions between proteins and polysaccharides. [ABSTRACT FROM AUTHOR]

Micelles self-assembled from drug-conjugated polymers indicate advantages in alleviating the premature release before reaching the intended site. Hyaluronic acid (HA) is known to specifically bind with a transmembrane glycoprotein CD44, overexpressed in many types of cancerous cells, and can also be served as micelle carriers. However, an excess amount of drug conjugation to HA backbone may be detrimental to the receptor-mediated cellular uptake. Up to now, the effect of conjugation densities of drugs has never been determined on the physical properties and biological performance of resulting micelles. In the current study, camptothecin (CPT) was conjugated on HA through 3,3′-dithiodipropionic acid to self-assemble into reduction-sensitive micelles. The substitution degrees of CPT on HA backbone were tuned from around 4–20%, to clarify the effects on the cellular uptake efficiency and cytotoxicities of micelles, as well as the tumor accumulation and antitumor efficacy. The CPT substitution degree of around 15% on HA resulted in micelles with a higher cytotoxicity to 4T1 cells and achieved a better balance between the cellular uptake and reduction-triggered drug release, compared with other micelles. In contrast to a fast kidney clearance and an even distribution in major organs after intravenous injection of free CPT, the optimized micelles were accumulated in tumors, livers and lungs. The micelle content indicated a significant decrease in livers after 24 h, while that in tumors displayed a significant increase to 4.9% of the injection dose. The tumor accumulation of micelles led to strong tumor suppression with minimal systemic toxicity. The in situ tumor inhibition and the accumulation of micelles in liver and lungs inhibited tumor metastasis to these tissues. It demonstrates a feasible strategy to develop drug-HA conjugate micelles with a concise and tunable structure for tumor targeting and reduction-triggered release. Statement of Significance Hyaluronic acid (HA) can be served as micelle carriers and targeting ligands to tumor cells. However, the effects of drug conjugation densities on the physical profile and biological performance of resulting micelles have never been investigated. In the current study, camptothecin is conjugated on HA with reduction-sensitive linkers, and the substitution degrees of camptothecin on HA backbone vary from around 4–20%. The micelles with a substitution degree of around 15% achieve a better balance between the cellular uptake and reduction-triggered drug release and a higher cytotoxicity than others. It demonstrates a feasible strategy to develop drug-HA conjugate micelles with a concise and tunable structure for tumor targeting and reduction-triggered release. [ABSTRACT FROM AUTHOR]

• Zein-CMC complexes (ZCs) were dispersible in water. • Interfacial properties of ZCs could be controlled by charge properties of CMC. • The nano-network structures of ZCs enhanced the emulsion stability. • Droplet size and stability of the emulsions could be tailored. In this study, co-assembled protein-polysaccharide complexes (ZCs) were prepared by fixing zein nanoparticles at the fibrillar carboxymethyl cellulose (CMC) by pH-driven anti-solvent precipitation. The complexation boosted the dispersity of zein from 17.3% to 88.6%. Scanning electron microscopy and atomic force microscopy confirmed the formation of network structures where the fibrous polysaccharides inserted into the interval of granular proteins. Circular dichroism spectrum, fluorescence spectrum, and X-ray diffraction verified the electrostatic interaction pattern between zein and CMC. Besides, the ZCs presented favorable amphiphilic properties, and the electrostatic interaction between zein and CMC can be fine-tuned by the substitution degree (DS) of carboxymethyl in CMC. Therefore, the Pickering emulsions stabilized by ZCs had controllable size and long-term stability using DS as a stimulus. Our study offers a novel strategy developing bio-based materials as novel stabilizers of Pickering emulsions. [ABSTRACT FROM AUTHOR]

Carboxymethyl cotton knitted fabrics (CM-CKFs) for wound dressings were fabricated with different solvents: water, ethanol-water, and isopropanol-water. The FTIR analysis showed that carboxymethylation reaction in the CM-CKFs occurred with the different solvents. With the water, ethanol-water and isopropanol-water order and the decrease of water ratio in the mixed solution, the degree of substitution (DS) increased, the crystallinity index of the CM-CKFs decreased, crystal structure of cellulose changed from type I to II, and appreciable increased in fiber diameter and gel formation. The water absorbency and water retention of the CM-CKFs increased with DS. The water absorbency of the CM-CKFs treated in water, ethanol-water (v/v = 3/1), and isopropanol-water (v/v = 3/1) was 1.86, 6.95, and 14.86 g/g, respectively. The breaking force of the CM-CKFs was lower than that of cotton knitted fabrics, but the breaking force increased with the DS, so did the breaking elongation. The water vapor permeability and water diffusibility decreased with the DS. The results demonstrated that the carboxymethylation of CM-CKFs occurring in isopropanol-water was most effective and uniform. The findings have theoretical and practical significance for the industrial uses of carboxymethyl cellulose dressing. [ABSTRACT FROM AUTHOR]

Pea starch ( PS) appears to be very attractive for the peculiar physicochemical characteristics, which is used for the vermicelli, film-forming material due to the high amylose content. The aim of this study was to optimise the hydroxypropylation technology parameters of the microcrystalline pea starch based on pea starch as a raw material, hydrochloric acid as an hydrolysis reagent, epoxy propane as an etherisation reagent by the Box-Behnken method. The thermal properties of hydroxypropylated microcrystalline pea starch were characterised by the thermogravimetric analyser and differential scanning calorimeter, respectively. Through the analysis of Design-Expert software, the regression model and corresponding variances were obtained. In this case, the determination coefficient ( R2) was 0.9631. This implied that 96.31% of the variation could be explained by the regression model. The best reaction conditions for preparing the hydroxypropylated microcrystalline pea starch were as follows: reaction temperature 40 °C, reaction time 16 h, amount of epoxy propane 14%, amount of sodium hydroxide 1.2% and amount of anhydrous sodium sulphate 12%. After the microcrystalline pea starch was hydroxypropylated, its peak temperature, melting enthalpy, temperature range of the endothermic peak increased, but its the thermal stability, onset temperature decreased. [ABSTRACT FROM AUTHOR]

Abstract: A novel substance, cationic acetylcholine potato starch (CAPS), was developed for the first time. The synthesis process had three steps: first, carboxymethyl potato starch (CMPS) was synthesized under sodium hydroxide alkaline condition and in isopropyl alcohol organic media; second, bromocholine chloride (BCC) was synthesized with sulphuric acid as a catalytic agent; finally, CAPS was synthesized by the reaction of CMPS with BCC in N,N′-dimethylformamide (DMF). The degree of substitution (DS) of CAPS was determined by ammonia gas-sensing electrode and elemental analysis. CAPS was characterized by Fourier transformed infrared (FTIR) and near infrared (FTNIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). [Copyright &y& Elsevier]

Abstract: A novel method for simultaneously determining the degree of deacetylation (DD), the degree of substitution (DS) and the distribution fraction of –COONa (δ –COONa) or –COOH (δ –COOH) in carboxymethyl chitosan (CM-chitosan) was developed by potentiometric titration. The effect of precipitate on the third inflection point, a common problem in the previous method, was eliminated by integrated application of alkaline titration and acidic titration. Calculating formulas of DS, DD and δ –COONa considering both the residues (GlcN and GlcNAc) and the carboxymethyl forms (–COONa and –COOH) were proposed. CM-chitosan products in different forms were examined to prove the reliability of the method. The standard deviation of DS, DD and δ –COONa of Na salt CM-chitosan (n =9) were 0.109, 3.51% and 4.30%, respectively. As CM-chitosan was confirmed by IR and 1H NMR to be N,O-CM-chitosan, the method is suitable for the parameter determination of N-, O- and N,O-CM-chitosan. [Copyright &y& Elsevier]

Abstract: The aim of this paper is the modification of the release behaviour of hydrophilic HPMC-based matrices of different substitution degree (E4M, F4M, K4M) by the introduction of a new inert polymeric excipient hydroxypropylcellulose-methyl methacrylate (HCMMA) at different proportions (75:25, 50:50 and 25:75). The product (HCMMA) was dried either in a vacuum oven – OD copolymers – or freeze-dried—FD copolymers. HPMC E4M formulations showed the worst compaction properties. All mixtures presented a percentage of theophylline release between 47% and 32% at 1440min. The drying methods employed had only influence over the drug release in E4M and K4M formulations, at higher proportions of HCMMA, showing the highest release the mixtures containing OD-HCMMA. Combinations of diffusion and erosion release mechanisms were found to matrix tablets. All mixtures with F4M did not modify relaxation rate constant values of Peppas and Shalin equation (k r ) respect to F4M 100%. However, all mixtures with K4M showed the highest k r values, which decreased when HCMMA proportion decreased. Only K4M mixtures showed a different diffusion front movement than the other mixtures. The modulation of theophylline monoaxial release was obtained using a high percentage of HCMMA, and HPMCs with a substantial difference of hydroxypropyl groups (F4M and K4M or E4M). [Copyright &y& Elsevier]

A new kind of polyacrylamide derivate, hydroximic polyacrylamide (HPAM), was prepared from polyacrylamide (PAM) with hydroxylamine hydrochloride in KOH/alcohol solution. Based on colorimetric method in the measurement of C7–9 alkyl hydroximic acid, the substitution degree of HPAM was determined by selecting octyl hydroximic acid as a primary standard substance. The effects of temperature, the amount of hydroxylamine and potassium hydroxide, and the reaction time on the reaction are discussed. HPAM with 5.78% substitution of degree was acquired by optimizing the reaction conditions. IR spectra revealed that tautomerism appears in the HPAM, and that HPAM exists in both the forms of hydroxamic type and hydroximic type, and the latter type can easily lead to the forming of intramolecular hydrogen bond. [ABSTRACT FROM AUTHOR]

In this study, high internal phase Pickering emulsions (HIPPEs) stabilized by protein-polysaccharide complexes were used as inks for food-grade three-dimensional printing (3DP). The complexes (RCs) structured by synergistic interactions between rice proteins (RPs) and carboxymethyl cellulose (CMC) displayed outstanding biphasic wettability with excellent ability to reduce the oil/water interfacial tension. The interfacial structures formed by RCs provided a steric barrier and sufficient electrostatic repulsion, preventing droplet coalescence against heating treatment as well as long-term storage. Moreover, the rheological behaviors of the HIPPEs can be tuned by the substitution degree (DS) of CMC for tailorable hydrophobic/hydrophilic properties of RCs, allowing their controllable injectability and printability during 3DP. The HIPPEs stabilized by RCs with a DS 1.2 showed the most favorable printing resolution, hardness, adhesiveness, and chewiness. Associating the hydrophobic RPs with hydrophilic CMC, our study enabled on-demand amphiphilicity of RCs for effective stabilization of HIPPEs that can be manipulated for 3DP. • Amphiphilic protein-polysaccharide complexes (RCs) were prepared by pH-cycle. • The interfacial properties of RCs could be controlled by the DS of CMC. • High internal phase emulsions (HIPEs) were prepared by RCs with good stability. • The HIPPEs were injectable and were amenable for there-dimensional printing. [ABSTRACT FROM AUTHOR]

The modification of the biobased polymer chitosan is a broad and widely studied field. Herein, an insight into the hydrophobization of low-molecular-weight chitosan by substitution of amino functionalities with hexanoyl chloride is reported. Thereby, the influence of the pH of the reaction media was investigated. Further, methods for the determination of the degree of substitution based on 1H-NMR, FTIR, and potentiometric titration were compared and discussed regarding their accuracy and precision. 1H-NMR was the most accurate method, while FTIR and the potentiometric titration, though precise and reproducible, underlie the influence of complete protonation and solubility issues. Additionally, the impact of the pH variation during the synthesis on the properties of the samples was investigated by Cd2+ sorption experiments. The adjusted pH values during the synthesis and, therefore, the obtained degrees of substitution possessed a strong impact on the adsorption properties of the final material. [ABSTRACT FROM AUTHOR]

• MP oxidation is dependent upon chloride salt type and substitution degree. • Carbonyl content of MP increased with KCl substitution. • The 25% of NaCl substituted by CaCl 2 or MgCl 2 raised MP's disulfide bond level. • Substitution of NaCl significantly affected the protein G′ peak and microstructures. • Protein oxidation and 25% KCl substitution could enhance gel strength and WHC. Effects of partial substitution of NaCl with KCl, MgCl 2 or CaCl 2 on oxidative characteristics of myofibrillar protein (MP) in a hydroxyl radical generating system and their heat-induced gel properties were investigated. Results indicated that MP oxidation is dependent upon the different chloride salt types and substitution degree. MP at 0.60 M NaCl was beneficial to protein unfolding and gel quality in the oxidative system. Increased formation of disulfide bonds affected the MP conformation and resulted in a large particle size and an aggregated network of gel at the 50% substitution degree of KCl. The presence of CaCl 2 or MgCl 2 substitutes contributed to protein polymerization and insolubility. MP aggregation restrained the formation of dense and continuous gel networks during heating, and thus resulted in a low-grade gel. Ca2+ had more serious impact on gel properties than Mg2+, dependent on different cation effects. Substitution of 25% NaCl by KCl gave acceptable gel quality in MP. [ABSTRACT FROM AUTHOR]