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Jaeyoung Je - One of the best experts on this subject based on the ideXlab platform.
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gallic acid grafted Chitosan inhibits foodborne pathogens by a membrane damage mechanism
Journal of Agricultural and Food Chemistry, 2013Co-Authors: Jaeyoung JeAbstract:In this study, antimicrobial activity of gallic acid-grafted-Chitosans (gallic acid-g-Chitosans) against five Gram-positive and five Gram-negative foodborne pathogens was evaluated. The minimum inhibitory concentrations (MICs) of gallic acid-g-Chitosans ranged from 16 to 64 μg/mL against Gram-positive bacteria and ranged from 128 to 512 μg/mL against Gram-negative bacteria. These activities were higher than those of unmodified Chitosan. The bactericidal activity of gallic acid-g-Chitosan (I), which showed the highest antimicrobial activity, was evaluated by time-killing assay with multiples of MIC, and it was recognized to depend on its dose. The integrity of cell membrane, outer membrane (OM), inner membrane (IM) permeabilization experiments, and transmission electron microscopy (TEM) observation were conducted for elucidation of the detailed antimicrobial mode of action of gallic acid-g-Chitosan. Results showed that treatment of gallic acid-g-Chitosan (I) quickly increased the release of intracellular c...
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preparation characterization and antioxidant properties of gallic acid grafted Chitosans
Carbohydrate Polymers, 2011Co-Authors: Jaeyoung JeAbstract:Abstract Gallic acid-grafted-Chitosans (GA-g-Chitosans) with four different grafting ratios were prepared by a free radical-induced grafting reaction in order to improve antioxidant and water-solubility. To verify the synthesis of GA-g-Chitosans, 1H NMR and thin layer chromatography were employed, and the results revealed that GA was grafted onto the Chitosan. The antioxidant properties of the GA-g-Chitosans were evaluated using several in vitro models. GA-g-Chitosan (I), which has the highest GA content, showed 92.26% scavenging activity against 2,2-diphenyl-1-picrylhydrazyl and 93.15% hydrogen peroxide scavenging activity at 50 μg/mL. GA-g-Chitosan (I) was also showed higher reducing power compared to others. All GA-g-Chitosans showed improved antioxidant capacities compared to plain Chitosan treated in the same conditions without gallic acid grafting. Furthermore, the GA-g-Chitosans also exhibited good cytocompatibility and effectively inhibited the formation of intracellular reactive oxygen species (ROS) in time- and dose-dependent manner in RAW264.7 macrophages.
Samuel P Meyers - One of the best experts on this subject based on the ideXlab platform.
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comparison of physicochemical binding and antibacterial properties of Chitosans prepared without and with deproteinization process
Journal of Agricultural and Food Chemistry, 2003Co-Authors: Shin Ho Lee, Na Young Park, Samuel P MeyersAbstract:Physicochemical, binding, and antibacterial properties of Chitosans prepared without and with deproteinization (DP) process (5, 10, 15, and 30 min at 15 psi/121 degrees C) were compared. Chitosan from DP 0 min had comparable nitrogen content, lower degree of deacetylation and solubility, but higher molecular weight and viscosity than Chitosans from DP 5-30 min. The latter four Chitosans showed differences only in molecular weight. Deproteinization treatment resulted in slightly decreased L values and increased a and b values compared with those of DP 0 min. Chitosan from DP 0 min had comparable water and fat-binding capacity (FBC) except for Chitosan from DP 15 min, which had a higher FBC but lower dye-binding capacity than those of the four Chitosans from DP 5-30 min. The antibacterial activities of Chitosans against seven different bacteria showed that the inhibitory effects varied with the deproteinization time and the particular bacterium.
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antibacterial activities of Chitosans and Chitosan oligomers with different molecular weights on spoilage bacteria isolated from tofu
Journal of Food Science, 2002Co-Authors: H K No, Na Young Park, H J Hwang, Samuel P MeyersAbstract:Seven bacteria were isolated from spoiled tofu and identified as Bacillus sp. (S08), B. megaterium (S10), B. cereus (S17, S27, S28, S32), and Enterobacter sakazakii (S35). In a paper disc test with 6 Chitosans and 6 Chitosan oligomers of different molecular weights, Chitosans showed higher antimicrobial activity than did Chitosan oligomers at a 0.1% concentration. Results of inhibitory effects of 6 Chitosans on growth of Bacillus sp. (S08) failed to detect viable cells after incubation for 24 hrs at 37 C, even at 0.02% concentration. With B. megaterium (S10) and B. cereus (S27), a 3 to 4 log cycle reduction was found in the Chitosan-treated group. The growth of Enterobacter sakazakii (S35) was completely suppressed in the presence of 0.04% Chitosan except for 1 Chitosan product. The minimum inhibitory concentration of Chitosan differed with products and isolates, ranging from 0.005% to above 0.1%.
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antibacterial activity of Chitosans and Chitosan oligomers with different molecular weights
International Journal of Food Microbiology, 2002Co-Authors: Na Young Park, Shin Ho Lee, Samuel P MeyersAbstract:Antibacterial activities of six Chitosans and six Chitosan oligomers with different molecular weights (Mws) were examined against four gram-negative (Escherichia coli, Pseudomonas fluorescens, Salmonella typhimurium, and Vibrio parahaemolyticus) and seven gram-positive bacteria (Listeria monocytogenes, Bacillus megaterium, B. cereus, Staphylococcus aureus, Lactobacillus plantarum, L. brevis, and L. bulgaricus). Chitosans showed higher antibacterial activities than Chitosan oligomers and markedly inhibited growth of most bacteria tested although inhibitory effects differed with Mws of Chitosan and the particular bacterium. Chitosan generally showed stronger bactericidal effects with gram-positive bacteria than gram-negative bacteria in the presence of 0.1% Chitosan. The minimum inhibitory concentration (MIC) of Chitosans ranged from 0.05% to >0.1% depending on the bacteria and Mws of Chitosan. As a Chitosan solvent, 1% acetic acid was effective in inhibiting the growth of most of the bacteria tested except for lactic acid bacteria that were more effectively suppressed with 1% lactic or formic acids. Antibacterial activity of Chitosan was inversely affected by pH (pH 4.5-5.9 range tested), with higher activity at lower pH value.
Kjell M Varum - One of the best experts on this subject based on the ideXlab platform.
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effect of Chitosan chain architecture on gene delivery comparison of self branched and linear Chitosans
Biomacromolecules, 2011Co-Authors: Jostein Malmo, Kjell M Varum, Sabina P StrandAbstract:Chitosan possesses many characteristics of an ideal gene delivery system. However, the transfection efficiency of conventional Chitosans is generally found to be low. In this study, we investigated the self-branching of Chitosans as a strategy to improve its gene transfer properties without compromising its safety profile. Self-branched (SB) and self-branched trisaccharide-substituted (SBTCO) Chitosans with molecular weights of 11-71 kDa were synthesized, characterized, and compared with their linear counterparts with respect to transfection efficiency, cellular uptake, formulation stability, and cytotoxicity. Our studies show that in contrast with unmodified linear Chitosans that were unable to transfect HeLa cells, self-branched Chitosans mediated high transfection efficiencies. The most efficient Chitosan, SBTCO30, yielded gene expression levels two and five times higher than those of Lipofectamine and Exgen, respectively, and was nontoxic to cells. Nanoparticles formed with SBTCO Chitosans exhibited a higher colloidal stability of formulation, efficient internalization without excessive cell surface binding, and low cytotoxicity.
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binding of ions to Chitosan selectivity studies
Carbohydrate Polymers, 2003Co-Authors: Inger M N Vold, Kjell M Varum, Eric Guibal, Olav SmidsrodAbstract:Abstract Selectivity coefficients for binding of negative and positive ions to Chitosans of different chemical composition have been determined by equilibrium dialysis. Chitosans with different fraction of acetylated units ( F A of 0.01 and 0.49) generally behaved similarly in their selectivity towards both negative and positive ions. No selectivity was found in the binding of chloride and nitrate ions, while Chitosan showed a strong selectivity towards molybdate polyoxyanions, with selectivity coefficients around 100. Chitosan showed a strong selectivity towards copper (Cu 2+ ) compared to the metal ions zinc (Zn 2+ ), cadmium (Cd 2+ ) and nickel (Ni 2+ ), with selectivity coefficients from 10 to 1000, while little or no selectivity could be detected with the other metal ions. Ionic strength and pH did not influence the selectivity coefficients of the Chitosans towards the metal ions.
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mode of action of chitin deacetylase from mucor rouxii on partially n acetylated Chitosans
Carbohydrate Research, 1998Co-Authors: Aggeliki Martinou, Vassilis Bouriotis, Bjorn T Stokke, Kjell M VarumAbstract:Abstract The mode of action of chitin deacetylase (CDA) from Mucor rouxii on fully water–soluble partially N -acetylated Chitosans was investigated. The Michaelis–Menten constants of three high-molecular-weight Chitosans with initial fraction of acetylated units ( F A ) of 0.08, 0.35, and 0.62 were determined to 2.1±0.4, 1.7±0.7, and 2.1±0.3 mg/mL, respectively. The relative rate of enzymatic deacetylation increased linearly with increasing F A on the Chitosans, indicating that CDA does not preferentially attack any sequences in the Chitosan molecules. A water-soluble and highly N -acetylated Chitosan with F A of 0.681, having a Bernoullian distribution of acetylated ( A ) and deacetylated ( D ) units, and a number-average degree of polymerization ( dp n ) of 30, was selected as substrate for CDA for more detailed studies of the mode of action. The Chitosan was enzymatically deacetylated to decreasing F A -values ( F A of 0.582, 0.400, and 0.188), and the nearest neighbour frequencies ( F AA , F AD , F DA and F DD ) were determined by NMR spectroscopy, showing that the transition frequencies F AD and F DA were lower than expected from a random (Bernoullian) distribution in the further enzymatically deacetylated Chitosans, while F AA and F DD were higher compared to a random distribution. The experimental results were compared with model data, assuming an endo-type mechanism with no preferential attack at any sequences in the Chitosan chain. The comparison suggested that CDA hydrolysed acetyl-groups according to a multiple attack mechanism, with a degree of multiple attack of at least three. No deacetylation could be detected at the non-reducing end of the enzymatically deacetylated Chitosans.
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in vitro degradation rates of partially n acetylated Chitosans in human serum
Carbohydrate Research, 1997Co-Authors: Kjell M Varum, Mildrid M Myhr, Ragnhild J N Hjerde, Olav SmidsrodAbstract:The initial degradation rates (r) in human serum of three Chitosans with FA = 0.42, 0.51, and 0.60 were determined by measuring the decrease in viscosity as a function of time. A strong increase in r with increasing FA of the Chitosans was observed, with r increasing proportionally to FA4.5. With increasing concentrations of lysozyme added to the reaction mixtures of Chitosan and serum, the relative increase in degradation rate of Chitosans with increasing FA was almost the same as that without lysozyme added. Addition of the chitinase inhibitor allosamidin (50 microM) did not inhibit the degradation rate of Chitosan (FA = 0.60) by human serum. The results suggest that Chitosans are actually mainly depolymerized by lysozyme in human serum, and not by other enzymes or other depolymerization mechanisms.
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water solubility of partially n acetylated Chitosans as a function of ph effect of chemical composition and depolymerisation
Carbohydrate Polymers, 1994Co-Authors: Kjell M Varum, Mette H Ottoy, Olav SmidsrodAbstract:Abstract The solubility of four partially N -acetylated Chitosans with fraction of acetylated units ( F A ) of 0.01, 0.17, 0.37 and 0.60 as a function of pH was investigated. The Chitosan with F A =0.60 was soluble at all pH-values between 4 and 9. The solubility versus pH curve of the other Chitosans, showed that all Chitosans precipitated between pH 6 and 7.5, but with increasing solubility at higher pH-values with increasing F A . Such solubility differences may have profound effects on enzyme accessability and biological effects of Chitosans. The three Chitosans with the lowest F A values were depolymerised by treatment with nitrous acid, and the fraction of water-soluble material at pH 7.5 was determined. The almost fully deacetylated Chitosan was completely insoluble at pH 7.5 in the depolymerisation range investigated, while the most acetylated Chitosan ( F A =0.60) was fully soluble at all pH-values. However, the two Chitosans with F A =0.17 and 0.37 could be fractionated into a neutral-soluble and a neutral-insoluble fraction. The amount of neutral-soluble material increased with decreasing depolymerisation. The neutral-soluble and the neutral-insoluble fraction differed in both chemical composition and degree of polymerisation. Generally, the neutral-soluble fraction had a higher fraction of acetylated units and a lower degree of depolymerisation than the neutral-insoluble fraction. This compositional heterogeneity of the degraded Chitosans was shown to be consistent with what is expected from the theoretical random degradation of Chitosans with a Bernoullian (random) distribution of acetylated and deacetylated units.
Sekwon Kim - One of the best experts on this subject based on the ideXlab platform.
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reactive oxygen species scavenging activity of aminoderivatized Chitosan with different degree of deacetylation
Bioorganic & Medicinal Chemistry, 2006Co-Authors: Sekwon KimAbstract:Chitosans with different degree of deacetylation were prepared from crab shell chitin in the presence of alkali. Aminoderivatized Chitosan derivatives were prepared in addition of amino functional groups at a hydroxyl site in the Chitosan backbone. Six kinds of aminoderivatized Chitosan such as aminoethyl-Chitosan (AEC90), dimethylaminoethyl-Chitosan (DMAEC90), and diethylaminoethyl-Chitosan (DEAEC90), which were prepared from 90% deacetylated Chitosan, and AEC50, DMAEC50 and DEAEC50, which were prepared from 50% deacetylated Chitosan, were prepared and their reactive oxygen species (ROS) scavenging activities were investigated against hydroxyl radical, superoxide anion radical and hydrogen peroxide. The electron spin resonance (ESR) spectrum revealed that AEC90 showed the highest scavenging effects against hydroxyl and superoxide anion radical, the effects were 91.67% and 65.34% at 0.25 and 5 mg/mL, respectively. For hydrogen peroxide scavenging effect, DEAEC90 exhibited the strongest activity. These results suggest that the scavenging effect depends on their degree of deacetylation and substituted group.
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cytotoxic activities of water soluble Chitosan derivatives with different degree of deacetylation
Bioorganic & Medicinal Chemistry Letters, 2006Co-Authors: Youngsook Cho, Sekwon KimAbstract:Chitosans with different degree of deacetylation (DD) (90% and 50% deacetylated Chitosan) were prepared by N-deacetylation followed by grafted onto Chitosan to form water-soluble aminoethyl-Chitosan (AE-Chitosan), and dimetylaminoethyl-Chitosan (DMAE-Chitosan), diethylaminoethyl-Chitosan (DEAE-Chitosan). In the present study, cytotoxic activities of the Chitosan derivatives were evaluated using three tumor cell lines and two normal cell lines, and structure-activity relationship was suggested. The cytotoxic activity was dependent on their DD and substituted group.
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preparation of hetero chitooligosaccharides and their antimicrobial activity on vibrio parahaemolyticus
Journal of Microbiology and Biotechnology, 2004Co-Authors: Pyojam Park, Hunku Lee, Sekwon KimAbstract:This study was performed to investigate the antimicrobial effects of hetero-Chitosans and their oligosaccharides on the halophilic bacterium, Vibrio parahaemolyticus. Nine classes of hetero-Chitosan oligosaccharides were prepared based on their molecular weights, using an ultrafiltration membrane reactor system with Chitosanase and celluase, from partially different deacetylated Chitosans, 90%, 75%, and 50% deacetylated Chitosan, respectively. Thirty-two strains of V. parahaemolyticus were isolated from various marine organisms such as shellfish, shrimps, octopus, and seabirds. Seventy-five percent deacetylated Chitosan showed the highest antimicrobial acitivity. The minimal inhibitory concentration (MIC) was 0.5 mg/ml on 14 strains of V. parahaemolyticus, and MIC of the rest strains (18 strains) was 1.0 mg/ml. In addition, MIC of most hetero-Chitosan oligosaccharides was 8.0 mg/ml. The results revealed that the antimicrobial effects of hetero-Chitosans and their oligosaccharides against V. parahaemolyticus depend on the degree of deacetylation, their molecular weights, and strains tested.
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angiotensin i converting enzyme ace inhibitory activity of hetero chitooligosaccharides prepared from partially different deacetylated Chitosans
Journal of Agricultural and Food Chemistry, 2003Co-Authors: Pyojam Park, Sekwon KimAbstract:Angiotensin I converting enzyme (ACE) inhibitory activity of hetero-chitooligosaccharides (hetero-COSs) prepared from partially different deacetylated Chitosans was investigated. Partially deacetylated Chitosans, 90, 75, and 50% deacetylated Chitosan, were prepared from crab chitin by N-deacetylation with 40% sodium hydroxide solution for durations. In addition, nine kinds of hetero-COSs with relatively high molecular masses (5000−10 000 Da; 90-HMWCOSs, 75-HMWCOSs, and 50-HMWCOSs), medium molecular masses (1000−5000 Da; 90-MMWCOSs, 75-MMWCOSs, and 50-MMWCOSs), and low molecular masses (below 1000 Da; 90-LMWCOSs, 75-LMWCOSs, and 50-LMWCOSs) were prepared using an ultrafiltration membrane bioreactor system. ACE inhibitory activity of hetero-COSs was dependent on the degree of deacetylation of Chitosans. 50-MMWCOSs that are COSs hydrolyzed from 50% deacetylated Chitosan, the relatively lowest degree of deacetylation, exhibited the highest ACE inhibitory activity, and the IC50 value was 1.22 ± 0.13 mg/mL. In ...
Lingyun Chen - One of the best experts on this subject based on the ideXlab platform.
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low molecular weight Chitosan nanoparticles for cpg oligodeoxynucleotides delivery impact of molecular weight degree of deacetylation and mannosylation on intracellular uptake and cytokine induction
International Journal of Biological Macromolecules, 2020Co-Authors: Oksana Babii, Zhenggang Wang, Guangyu Liu, Elisa C Martinez, Sylvia Van Drunen Littelvan Den Hurk, Lingyun ChenAbstract:Abstract Although synthetic CpG oligodeoxynucleotides (ODNs) have shown substantial potential as immunotherapeutic agents, their effective intracellular delivery remains challenging. In this work, nanoparticles prepared from low-molecular weight (LMW) Chitosans were investigated as CpG ODN delivery systems. Chitosan samples with a molecular weight (Mw) of 5 and 15 kDa and degree of deacetylation (DDA) of 50 and 80% were prepared. Additionally, mannosylated Chitosans with a substitution degree of 15% were synthesized. The impact of LMW Chitosan Mw and DDA on nanoparticle physical properties and the associated immunostimulatory effect in RAW 264.7 cells was studied. Nanoparticles prepared with Chitosan of higher DDA and larger Mw exhibited better CpG ODN binding ability and intracellular uptake. Nevertheless, the most efficient immunostimulatory effect was observed while using 50% acetylated and mannosylated samples. The decreased charge density on Chitosan backbone resulted in the enhanced intracellular CpG ODN release, which promoted in vitro cytokine secretion. Moreover, mannose ligand grafting promoted nanoparticle uptake through receptor-mediated recognition. Overall, this research suggests that Chitosan structural parameters can be modulated to prepare LMW Chitosan nanoparticles that first efficiently encapsulate CpG ODN, and then release it in immune cells, thus may be used as an efficient vector for intracellular CpG ODN delivery.
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preparation characterization and in vitro anticoagulant activity of highly sulfated Chitosan
International Journal of Biological Macromolecules, 2013Co-Authors: Jianhong Yang, Kai Luo, Jun Cai, Lingyun ChenAbstract:This work is the first to report sulfation of Chitosans with different molecular weight (Mw, 51.5-112.4 kDa) via their trimethylsilylated derivatives as the precursors. Different from original Chitosan, silylated Chitosan was easily sulfated with sulfur trioxide-pyridine complex under homogeneous conditions in DMSO, and highly sulfated products with degree of sulfation (DS) in the range of 1.65-2.46 and Mw in the range of 18.1-54.5 kDa were obtained at 20-40°C. Degradation of Chitosan was inevitable in the reaction process. However, the extent of degradation reduced with increasing of degree of trimethylsilylation (DT). The results of UV-vis and fluorescence emission spectra indicated that the Chitosan degradation involved elimination reaction. Clotting assays showed that highly sulfated Chitosans significantly prolonged activated partial thromboplastin time (APTT) and thrombin time (TT), but not prothrombin time (PT). A high DS (>2.1) value was essential for the anticoagulant activity.
