Grafting Ratio Research Articles

Preparation of amidated pectins through enzymatic method: Structures, hydrogel properties and its application potential in fat substitutes

In this paper, α-alanine and β-alanine were used as modifiers to prepare α-alanine amidated pectin (α-AP) and β-alanine amidated pectin (β-AP) through enzymatic method. The effects of alanine and its isomer on the amidation degree and physicochemical properties of pectin were studied. Fourier transform infrared spectrum, proton nuclear magnetic resonance analysis, X-ray photoelectron spectrum and elemental analysis indicated that the amino groups from α-C and β-C could be aminated with the carboxyl group of pectin to form the corresponding aminated pectin. The alanine grafting ratio of α-AP and β-AP were 21.99% and 18.92%, respectively. The results showed that the dynamic viscosity of β-AP was significantly higher than that of α-AP due to the influence of amino acid side chain. However, due to the higher alanine grafting ratio of α-AP, the strength of hydrogel prepared by α-AP was higher than that of β-AP, and it also has the highest elastic modulus and swelling capacity. In addition, pectin, as a carbohydrate-based fat substitute, has been widely used in the field of food to simulate the smooth and delicate taste of fat. Compared with High methoxy pectin (HMP) and β-AP, α-AP had better colloid stability and smaller hydrogel particles in the composite system. The results provide references for the application of amidated pectin in low-fat food.

Solid phase synthesis of oxidized sodium alginate-tobramycin conjugate and its application for infected wound healing

Although sodium alginate possesses excellent biocompatibility, moisture retention and easy availability, it cannot be directly applied for infected wound treatment. Herein, a solid phase synthesis strategy was proposed to fabricate oxidized sodium alginate-tobramycin conjugate (OSA-TOB) for anti-infection dressing development. 13C nuclear magnetic resonance spectra indicated that the oxidization process does not change the ratio of β-D-mannuronic acid (M) / α-L-guluronic acid (G) in OSA and the oxidization reaction shows no stereoselectivity. Elemental analysis disclosed that the graft ratio of tobramycin in OSA-TOB is 13.8 %. Antibacterial test indicated that OSA-TOB can effectively inhibit four prevalent pathogenic bacterial S.epidermidis, P. aeruginosa, S. aureus and E. coli via a different antibacterial mechanism compared to the original TOB. Hemolysis and cytotoxicity assays shown that OSA-TOB have superior hemocompatibility and cytocompatibility. Infected wound healing assay shown that the healing rate of OSA-TOB is the highest. Further analysis indicated that OSA-TOB can reduce the local inflammatory response, accelerate the form of epithelium and collagen deposition. In conclusions, OSA-TOB synthesized in solid phase can be potentially applied as a promising anti-infection wound dressing.

Cellulose nanocrystals modification by grafting from ring opening polymerization of a cyclic carbonate

Surface modification of cellulose nanocrystals (CNC) by organocatalysed grafting from ring-opening polymerization (ROP) of trimethylene carbonate was investigated. Organocatalysts including an amidine (DBU), a guanidine (TBD), an amino-pyridine (DMAP) and a phosphazene (BEMP) were successfully assessed for this purpose, with performances in the order TBD > BEMP > DMAP, DBU. The grafting ratio can be tuned by varying the experimental parameters, with the highest grafting of 74 % by weight obtained under mild conditions, i.e at room temperature in tetrahydrofuran with a low amount of catalyst. This value is much higher than that of typical ring opening polymerizations of cyclic esters initiated from the surface of cellulose nanoparticles. Additionally, DSC analysis of the modified material revealed the presence of a glass transition temperature, indicative of a sufficient graft length to display polymeric behaviour. This is, to our knowledge, the first example of cellulose nanocrystals grafted with polycarbonate chains.

High mechanical properties and ionic conductivity of polysiloxane sulfonate via tuning ionization degree with clicking chemical reaction

Despite excellent environmental adaptability and good optical transparency, polysiloxane was poor electron or ion conductors. In this paper, ionized polymethylvinylsiloxane (I-PMVS) had been prepared via coupling anionic ring-opening polymerization of 2, 4, 6, 8-tetravinyl-2, 4, 6, 8-tetramethyl-cyclo-tetrasiloxane with thiolene addition reaction of sodium 2-mercapto-ethanesulfonate (MESNA). The degree of ionization was precisely controlled by adjusting the grafting content of MESNA via clicking chemical reaction. FTIR, 1 H NMR, and XRD were used to investigate the composition and structure of I-PMVS. TGA and DSC was used to investigate the thermal properties. The increase of ionization degree reduced the crystallinity of the polymer and bulk cohesion, and increased the T g of I-PMVS and maintained good thermal stability. Meanwhile, the water contact angle (WCA) test showed that the increase of ionization degree improved the hydrophilicity of PMVS and the high degree of ionization made PMVS having excellent water-solubility. The test of tensile properties showed I-PMVS possessed good tensile strength without filler reinforcement. Electrochemical impedance spectra (EIS) indicated I-PMVS possessed a high ionic conductivity (σ), highest to 4.20 × 10 −6 S/cm when 100% grafting. Ionization of PMVS should provide a strategy to develop high performance of polyelectrolyte applied in the field of energy storage devices and bionic materials. • Ionized polysiloxane with adjustable number of ions was obtained via click reaction. • The physical properties were tuned via varying the grafting ratio of ion group. • Mechanical strength and ion conductivity were enhanced via increasing grafting ratio.

Fabrication of phenylalanine amidated pectin using ultra-low temperature enzymatic method and its hydrogel properties in drug sustained release application

In this study, pectin was modified with phenylalanine by ultra-low temperature enzymatic method to improve its gel properties. The grafting ratio of phenylalanine amidated pectin was studied under different reaction conditions. The highest value (29.21 %) was reached a reaction temperature of −5 °C and time of 12 h. Further analysis indicated that phenylalanine and high methoxyl pectin combined at the solid-liquid two phase interface under the catalysis of papain to form phenylalanine amidated pectin. Moreover, the physicochemical properties of pectin hydrogel and its feasibility as a sustained-release drug carrier were discussed. The results showed that phenylalanine amidated pectin can form hydrogel with a certain strength under acidic conditions, and there is no need to add a lot of soluble solids and divalent cations. Besides, the phenylalanine amidated pectin hydrogel as a sustained release carrier of drugs showed more sustained and complete drug release.

Effects of Carbon Chain Length of Acrylate Monomer on Sizing Properties of Locust Bean Gum-g-P (AA-co-Acrylate)

In order to impart good application properties to locust bean gum size for all-polyester yarn, a series of acrylate monomers including methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and common hydrophilic monomer–acrylic acid were grafted onto molecular chains of native locust bean gum to obtain locust bean gum- g-P(AA-co-acrylate) products with similar grafting ratios through Fenton’s reagent, respectively. The effects of carbon chain length of the series of acrylates on sizing properties of the grafted locust bean gum for polyester warp were studied. It was found that by grafting acrylates onto the molecular chains of locust bean gum the sizing properties of the locust bean gum were improved markedly. Under the condition of similar grafting ratios, locust bean gum- g-poly(AA-co-methyl acrylate) showed the highest apparent viscosity, water solubility, film strength, wettability, and adhesion to polyester fiber in all the grafted locust bean gum prepared. Meanwhile, locust bean gum- g-poly(AA-co-butyl acrylate) and locust bean gum- g-poly(AA-co-2-ethylhexyl acrylate) had the highest wear resistance and elongation of sizing film, respectively. The modified locust bean gum grafted with acrylate monomers with different carbon chain lengths was able to meet various requirements in the sizing process for polyester yarn.

Ferulic acid- and gallic ester-acylated pectin: Preparation and characterization.

In this study, pectin was modified with ferulic acid (Fa), trans-ferulic acid (trans-Fa), methyl gallate (MG), and ethyl gallate (EG) via the enzymatic method using aqueous/organic phases to enhance its physiochemical and bio-active properties. Results revealed that lipase might catalyze the hydrolysis of the ester bond within pectin in aqueous phase and prompt the transesterification between the hydroxyl group in the para position in Fa/trans-Fa or the 2'-OH group of MG/EG and the carboxylic group of pectin in the organic phase. The graft ratio was 21.00%, 21.67%, 13.24%, and 11.93% for the Fa-, trans-Fa-, MG-, and EG-modified pectin, respectively. In addition, compared with native pectin, the modified pectin exhibited improved apparent viscosity and emulsion activity. Moreover, the clearance of 1,1-diphenyl-2-picryl hydrazine (DPPH) and 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) was effectively enhanced for the modified pectin. Furthermore, the modified pectin exhibited strong antibacterial activity against Escherichia coli and Staphylococcus aureus while no cytotoxic effects based on the results of cell culture experiments. Our results provide a theoretical basis for the expansion of pectin applications in the food and pharmaceutical industries.

Application of γ-cyclodextrin-lysozyme as host materials for encapsulation of curcumin: characterization, stability, and controlled release properties.

In this study, a safe and relatively stable γ-cyclodextrin-lysozyme (γ-CD-Lys) was synthesized using epichlorohydrin as the cross-linking agent, and curcumin was successfully encapsulated in γ-CD-Lys. The successful Lys grafting onto γ-CD can be demonstrated by a high grafting ratio (79.02%) and was further confirmed by Fourier transform infrared (FTIR) band shifts and the new signal obtained at δ 2.75 in proton nuclear magnetic resonance. The encapsulation efficiency value of γ-CD-Lys was 76.74%, and the successful encapsulation of curcumin into γ-CD-Lys was confirmed by crystal structure change, increased melting point, and FTIR band shifts. The intermolecular bonds results suggested that associative forces between curcumin and γ-CD-Lys were electrostatic interaction, hydrogen bonds interaction, and hydrophobic interaction. The designed nanoparticles had excellent stability at low pH and low salt concentration. The release rate of these nanoparticles was inhibited in simulated gastric conditions, whereas it increased significantly in intestinal media. Simulated gastrointestinal digestion experiments further confirmed that nanoparticles showed higher bioaccessibility (86.05%) compared with curcumin (58.82%). Overall, our study showed that the nanoparticles were highly promising for delivering curcumin because of their enhanced functional attributes and stabilization in acid or low salt environments. Also, it was an excellent wall material for targeting hydrophobic bioactive compounds in the intestinal tract via oral administration. © 2022 Society of Chemical Industry.

Effects of selective distribution and migration of poly(methyl methacrylate)-grafted nanoclays on the phase behavior of poly(methyl methacrylate)/poly (styrene-co-acrylonitrile) blends

The effect of selective distribution and migration behavior of two kinds of poly (methyl methacrylate)-grafted nanoclays (PMMA- g -clay) on the phase behavior of PMMA/poly (styrene- co -acrylonitrile) (SAN) blends is investigated. The grafting ratios of our two modified nanoclays are similar, but their grafting density and grafted chain lengths are different, resulting in their different initial locations and subsequent migration behaviors in the blend matrix. The PMMA- g -clay(d) nanosheets (NSs) with relatively dense and short chains are always distributed at the interfacial region and further form the percolation networks to block the concentration fluctuation and retard the domain coarsening of blend matrix more remarkably, while the PMMA- g -clay(s) NSs with relatively sparse and long chains are distributed at first in the SAN-rich domains and subsequently move slowly to the interfacial region, resulting in their inhibition of the phase separation for PMMA/SAN blend from retarding SAN chains’ viscous diffusion to their gradual interfacial aggregation for stabilizing the morphology. The variation of storage modulus for three systems in low frequency and long-time regimes are also affected by different selective distributions of two grafted clay NSs in PMMA/SAN blend matrix. • The compatibilization effects of two clay nanosheets grafted with different length and grafting density of PMMA chains were compared. • The two nanosheets have the same thermodynamically stable location but different migration behaviors. • Both the two nanosheets hardly affect the phase coarsening of polymer blend at the early stage of the spinodal decomposition. • The inhibition effects of the two nanosheets are different at intermedium and late stages.

Covalent modification of zein with polyphenols: A feasible strategy to improve antioxidant activity and solubility.

Covalent modification of protein with polyphenols is an attractive research topic, since it is an effective way to improve the properties and broaden the applications of protein. However, the majority of prolamin-polyphenol reactions were carried out in alcohol aqueous solution, and this study aimed to investigate the covalent interaction of zein and polyphenols in water. Chlorogenic acid (CGA), gallic acid (GA), and caffeic acid (CA) were used as polyphenol models. The grafting ratio revealed that zein interacted more strongly with CGA and CA than with GA, which was probably due to the larger molecular weight of CGA and the hydroxycinnamic acid structure of CA. Afterward, the differences in structural and functional properties between control zein and zein-polyphenol complexes were compared. Covalent interaction with polyphenols induced great changes in the morphology and secondary structure of zein. Compared with control zein and non-covalent complexes, covalent zein-polyphenol complexes exhibited better solubility, antioxidant activity, and thermal stability. PRACTICAL APPLICATION: Covalent modification of zein with polyphenols in water is a simple and efficient method, which can ameliorate the antioxidant activity as well as the hydrophilicity of zein and improve its application value. The findings of this research carry important implications for using zein-polyphenol complexes as novel food additives, or to design more efficient delivery systems.

Preparation and application performance of graft-quaternization double modified chitosan electrospun antibacterial nanofibers

Inexpensive, biodegradable and antibacterial nanofibers were developed through graft-quaternization double modification of chitosan (CS) as a potential substitute for those from petroleum products. Chitin is available in large quantities at low price from fishery by-products, such as crab and prawn shells. However, native chitin and its derivative - CS have poor solubility in common spinning solvents, are difficult to be used as regenerated fibers, exhibit mediocre antibacterial property, and have limited medical application as functional fiber. In this research, CS-g-polydimethylaminoethyl methacrylate (PDMAEMA) and its quaternized product were prepared successively. Various nanofiber membranes were produced by electrospinning using the modified CS/PVA acetic acid blend spinning solutions. Effects of grafting ratio (GR) of DMAEMA and degree of quaternization (DQ) on major application performance of the blend nanofiber membranes, e.g. fiber fineness, tensile property, moisture-penetrability, and inhibition of E.coli and S.aureus, were evaluated systematically. When the GR and the DQ were 21.5% and 12.3% respectively, the quaternized CS-g-PDMAEMA/PVA blend nanofiber membrane possessed satisfied fiber fineness and smoothness, high tensile property and moisture-penetrability. In addition, the nanofiber thus produced had higher inhibition function to S.aureus than many commonly used antibacterial fibrous membranes.

Comparison of Effects of Different Sacrificial Hydrogen Bonds on Performance of Polyurethane/Graphene Oxide Membrane.

Processing robust mechanical properties is important for elastomeric materials. In this work, different molecular weights of polyethylene glycols (PEG) were used to modify graphene oxide (GO) in order to study the relationship between the number of hydrogen bonds and the properties of the polyurethane/graphene oxide membrane. The fact of PEG was successfully grafted onto the surface of GO was certified by Fourier transform infrared spectra, Raman spectra, X-ray photoelectron spectroscopy. The graft ratio was indicated by thermogravimetric analysis. The presence of hydrogen bonds in PUR/MGO composites membrane was proved by the cyclic loading-unloading test and stress relaxation test. The thermal stability and low-temperature resistance performance of PUR/MGO had been improved compared with PUR/GO. When the molecular weight of PEG grafted on the surface of GO was 600, the tensile strength and elongation at break of the composite membrane were optimal. The reason for the improvement of physical and mechanical properties was that the dispersion of filler in the rubber matrix and the compatibility between filler and rubber had been improved.

Hyaluronic acid-g-PPG and PEG-PPG-PEG hybrid thermogel for prolonged gel stability and sustained drug release

Hyaluronic acid-graft-poly(propylene glycol) (HA-g-PPG) was prepared to induce hydrophobic interactions between HA-g-PPG and F127 PPGs (poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol)) and consequent increases in gel stability of F127 gel. Molecular weights of 340, 1000, and 2500 Da were used for PPG, and grafting ratios of HA-g-PPG varied over 3%, 12%, and 50%. Using rheology measurements, 1H NMR spectra, lower critical solution temperature measurements, dynamic light scattering, and transmission electron spectroscopy, hydrophobic crosslinking and intermicellar bridge formation were suggested in the aqueous HA-g-PPG/F127 hybrid solutions. In particular, the gel stability of the HA-g-PPG/F127 hybrid thermogel increased from 2 days (F127 only) to 6 days, thus the hybrid thermogel can provide longer delivery of an incorporated drug. The HA-g-PPG/F127 thermogel exhibited tissue compatibility in the subcutaneous layer of rats. The protein drug release from the gel indicated that interactions between negative charged HA-g-PPG and positive charged drug (calcitonin) reduced initial burst release.

Comfort fitting shape memory elastomer with constructed strong interface based on amphiphilic hybrid Janus particles

Comfort fitting shape memory elastomer exhibits various potential application in flexible wearable and biomedical devices, which can be developed by mixing the comfort fitting elastomer with the materials of reversible transition. However, it's very difficult to obtain the soft touching feeling, high elongation, and excellent shape memory property at the same time, and the key point mainly depends on improving interface stability and adjusting the morphology by the compatibilizer . In the work, silicone elastomer with excellent shape memory property was obtained by developing an amphiphilic PCL-JP-PDMS hybrid Janus particles compatibilizer for methyl vinyl silicone elastomer/polycaprolactone (MVQ/PCL) blend. Only through increasing the PDMS grafting ratio on the PCL-JP-PDMS particles compatibilizer, the morphology of PCL dispersed phase changed from short fibrous to similar spherical, which ensured the comfort feeling (E = 5.9 MPa), high fixity (R f = 95%) and recovery ratio (R r = 99%) of shape memory MVQ/PCL blends. Furthermore, the shape memory silicone elastomer exhibited impressive elasticity in temporary shape at T = 25 °C, which is quite suitable for designing wearable device. Silicone elastomer with excellent shape memory property was obtained by developing an amphiphilic PCL-JP-PDMS hybrid Janus particles compatibilizer for MVQ/PCL blend, the amphiphilic PCL-JP-PDMS Janus particles were anchored at the interface of MVQ/PCL blends by the similar molecular chain entanglement and the stable conformation of asymmetric SiO 2 @PDVB particles. Much more importantly, the PCL-JP-PDMS particles with different PDMS grafting ratio were prepared as the compatibilizer, which made the interface adhesion and the property of MVQ/PCL blend be regulated by PDMS grafting ratio, which ensured the comfort feeling (E = 5.9 MPa), high fixity (R f = 95%) and recovery ratio (R r = 99%) of shape memory MVQ/PCL blends under the content of 3 wt % particles and 30 wt % PCL. Furthermore, the shape memory silicone elastomer exhibited impressive elasticity in temporary shape at T = 25 °C, which is quite suitable for designing wearable device.

Determination of The Grafting Performance of Some Hybrid Chestnut Genotypes and Cultivars

This study has been carried out to determine the graft compatibility of newly registered some hybrid chestnut cultivars and genotype. The study was conducted between 2012-2018 at the Ondokuz Mayıs University and the Black Sea Agricultural Research Institute. In the study, ‘Marigoule’, Akyüz’, ‘Ali Nihat’ and ‘Macit 55’ cultivars were tested as scion and rootstock, and A41 genotype was tested only as rootstock. Grafting studies were carried out on generative rootstocks in 2014 and mother plants in 2015 using the chip budding method. Graft success (%) was determined 30 days after grafting and survival ratio (%) at the end of the vegetation period. Also rootstock, graft area and scion diameter were measured at the end of the vegetation period by digital caliper. As a result of the study, graft success and survival ratio were low in combinations created with ‘Ali Nihat’ and A41 generative rootstocks. Among the plants, the best generative rootstock was the ‘Macit 55’ cultivar in terms of graft success and survival ratio. ‘Macit 55’ rootstock had good graft compatibility with both itself (‘Macit 55’), ‘Akyüz’ and ‘Ali Nihat’ cultivars. ‘Marigoule’ cultivar has generally shown severe graft incompatibility with complex hybrids tested in the study. In the grafts made on clone plants, the ‘Ali Nihat’ rootstock was determined as a good rootstock for itself (‘Ali Nihat’), ‘Akyüz’ and ‘Macit 55’ cultivars.

Prevention and Management of Small-for-Size Syndrome of Liver Transplantation

Small-for-size syndrome (SFSS) is a critical complication of partial liver transplantation, particularly in adult-to-adult living donor liver transplantation (ALDLT) using a small graft. Minimally required liver graft size for a successful ALDLT is classically 40% of a standard recipient’s liver volume or 0.8% of recipient body weight. Recent progress in perioperative care and technical improvement push the lower limit of safe graft size to 25% of the recipient’s standard liver volume or 0.6% of the graft versus recipient weight ratio although this is an ongoing debate. The clinical manifestations of SFSS include various symptoms and signs related to graft dysfunction and portal hypertension in patients with small grafts. The risk factors for SFSS include poor preoperative patient condition, including portal pressure, surgical techniques to reduce portal pressure, and graft quality and size. Hence, various approaches have been explored to modulate inflow and pressure to a small graft and to decrease the outflow block to alleviate this SFSS as well as the selection of a patient and graft. Additionally, recent research and efforts to prevent and treat SFSS are reviewed. (Ewha Med J 2022;45(2):29-34)

Dual crosslinking of folic acid-modified pectin nanoparticles for enhanced oral insulin delivery

Pectin-based drug delivery systems hold great potential for oral insulin delivery, since they possess excellent gelling property, good mucoadhesion and high stability in the gastrointestinal (GI) tract. However, lack of enterocyte targeting ability and premature drug release in the upper GI tract of the susceptible ionic-crosslinked pectin matrices are two major problems to be solved. To address these issues, we developed folic acid (FA)-modified pectin nanoparticles (INS/DFAN) as insulin delivery vehicles by a dual-crosslinking method using calcium ions and adipic dihydrazide (ADH) as crosslinkers. In vitro studies indicated insulin release behaviors of INS/DFAN depended on COOH/ADH molar ratio in the dual-crosslinking process. INS/DFAN effectively prevented premature insulin release in simulated GI fluids compared to ionic-crosslinked nanoparticles (INS/FAN). At an optimized COOH/ADH molar ratio, INS/DFAN with FA graft ratio of 18.2% exhibited a relatively small particle size, high encapsulation efficiency and excellent stability. Cellular uptake of INS/DFAN was FA graft ratio dependent when it was at/below 18.2%. Uptake mechanism and intestinal distribution studies demonstrated the enhanced insulin transepithelial transport by INS/DFAN via FA carrier-mediated transport pathway. In vivo studies revealed that orally-administered INS/DFAN produced a significant reduction in blood glucose levels and further improved insulin bioavailability in type I diabetic rats compared to INS/FAN. Taken together, the combination of dual crosslinking and FA modification is an effective strategy to develop pectin nano-vehicles for enhanced oral insulin delivery.

An environment-friendly chemical modification method for thiol groups on polypeptide macromolecules to improve the performance of regenerated keratin materials

The R&D and application of natural biomass resources is one of the important ways to solve the world's energy shortage and environmental pollution. However, the complex processing technology and poor mechanical properties seriously hinder the development of the biomass polymers. A kind of natural antioxidant, alpha-lipoic acid, was used to modify wool keratin by grafting thiols in this study, so as to ameliorated the physical properties of regenerated materials. The optimal process parameters and modification mechanism were explored. Research results indicated that grafting ratio of lipoic acid can reach more than 13% and the polypeptide chains were more stretched in solution, when 30% lipoic acid was added into keratin solution at 40 °C with a reaction time of 2 h. In addition, lipoic acid grafted on thiol groups can effectively weaken the intra- and intermolecular forces of keratin, this change made the arrangement of macromolecular chains more orderly. The physical structure of modified keratin became uniform and compact, and the materials had obtained better thermal and mechanical properties. This research provided a novel and environment-friendly method for the modification technology of keratin, and it was beneficial to expand the application fields of biomass materials.

Simulated preparation and hydration property of a new-generation zwitterionic modified PVDF membrane

Improving the surface hydrophilicity of the membrane can effectively deal with the membrane fouling problem in the water treatment process. In this work, the molecular dynamics (MD) simulation method was adopted to simulate the vapor induced phase separation (VIPS) process in the preparation of trimethylamine oxide-derived zwitterionic polymer-grafted polyvinylidene fluoride (PVDF-g-PTMAO) membrane. PTMAO is a new-generation zwitterionic material with zero-length carbon spacer length (CSL), which exclude the hydrophobic effect of the CSL. The hydration properties of the formed zwitterionic membrane were investigated. The effect of grafting ratio of PTMAO:PVDF on the membrane surface morphology and hydration ability were explored. The simulation results show that the zwitterionic segments are enriched at membrane surface due to the attraction of water vapor and a stable hydration layer is formed on the membrane surface. As the grafting ratio increases from 5% to 15%, the number of hydrogen bonds between membrane and water molecules boosts and their interaction is strengthened, while water diffusion along the membrane surface is reduced, as a result of significantly enhanced hydration of PVDF-g-PTMAO membrane. This work helps investigate the migration behavior of the zwitterionic polymer in a PVDF-based membrane during the VIPS process and provides a better understanding of the antifouling mechanism of zwitterionic membrane as well as gives a guidance for designing new antifouling materials.

Amidated pectin with amino acids: Preparation, characterization and potential application in Hydrocolloids

The poor gelatability of pectin is a barrier to its application in hydrogel field. In this study, glutamic acid, glycine and lysine (representing acidic, neutral and basic amino acids respectively) were grafted onto the pectin (Na-Pe) molecules in an ice bath, and the grafting ratio of amidated pectin was 4.98% (glutamic acid grafted pectin, Glu-Pe), 6.35% (glycine grafted penctin, Gly-Pe) and 7.78% (lysine grafted penctin, Lys-Pe), respectively. It was explored the effects of the three amino acids on the gel properties of pectin and evaluated their potential applications in drug sustained-release. Fourier transform infrared spectrum, X-ray photoelectron spectrum and proton nuclear magnetic resonance analysis indicated that the amidogen of the amino acids was bonded to carboxy group of the Na-Pe. After grafting with the amino acids, the viscosity of the amidated pectin was significantly improved, which was improved from 36.7 (Na-Pe) to 62.5 (Glu-Pe), 186.4 (Gly-Pe) and 129.8 mPa s (Lys-Pe). In addition, the gel strength the pectin was significantly improved by the introduction of the amino acids. In the absence of sucrose, Gly-Pe and Lys-Pe could form a solid hydrogel, while the Na-Pe and Glu-Pe could not. Moreover, Glu-Pe and Gly-Pe showed good sustained release ability of matrine, which indicates that they have broad application potential in the field of sustained-release hydrogels.