-
[show abstract]
[hide abstract]
ABSTRACT: A novel chitosan antibacterial dispersion system was prepared by oleoyl-chitosan (OCS) nanoparticles (OCNP). We further investigated the antimicrobial mode of OCNP against Escherichia coli and Staphylococcus aureus using a combination of approaches, including measurement of the effect of lecithin and phosphate groups, the conformation of membrane protein, internalization of fluorescein isothiocyanate (FITC)-labeled OCS nanoparticles (FITC-OCS nanoparticles) observed under fluorescence microscopy and DNA/RNA binding assay. Results of fluorescence experiments indicated that OCNP influenced the structure of bacterial membranes. The lecithin effect showed that OCNP bound to cytoplasmic membrane phospholipids of S. aureus, and phosphate groups played an important role. Fluorescence microscopy observations demonstrated that the way OCNP entered into bacteria varied against strains. The gel-retardation experiment showed that OCNP bound strongly to DNA/RNA and retarded their migration in the gels in a concentration-dependent manner. These results indicate that OCNP exerts its antibacterial activity by damaging the structures of cell membrane and putative binding to extracellular targets such as phosphate groups or intracellular targets such as DNA and RNA.
International journal of food microbiology 05/2009; 132(2-3):127-33. · 3.01 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Lactobacillus casei ATCC 393-loaded microcapsules based on alginate and gelatin had been prepared by extrusion method and the product could increase the cell numbers of L. casei ATCC 393 to be 10(7) CFU g(-1) in the dry state of microcapsules. The microparticles homogeneously distributed with size of 1.1 ± 0.2 mm. Four kinds of microcapsules (S(1), S(2), S(3) and S(4)) exhibited swelling in simulated gastric fluid (SGF) while the beads eroded and disintegrated rapidly in simulated intestinal fluid (SIF). Cells of L. casei ATCC 393 could be continuously released from the microcapsules during simulated gastrointestinal tract (GIT) and the release amounts and speeds in SIF were much higher and faster than that in SGF. Encapsulation in alginate-gelatin microcapsules successfully improved the survival of L. casei ATCC 393 and this approach might be useful in delivery of probiotic cultures as a functional food.
Journal of Microencapsulation 09/2008; 26(4):315-24. · 1.55 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Encapsulated Lactobacillus casei ATCC 393 was prepared by extrusion technology with rice shell powder and alginate followed by drying at 4°C. Drying at 4°C was beneficial to the survival of L. casei ATCC 393 compared with freeze drying. Trehalose had a positive effect on the survival of dried L. casei ATCC 393; the live cell numbers remained over 107 cfu/g after 8 weeks of storage at 4°C. Survival of L. casei ATCC 393 decreased with the increase of relative humidity (from 33 to 97%) while the immobilization technique protected cells from adverse gastric conditions (pH 1.2) by the survival ratio of 89%.
Drying Technology 07/2008; 26(7):895-901. · 2.08 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: In this study, we investigated the interface contacting inhibition behaviors of chitosan against bacterial in the dispersing
state. For that purpose, chitosan microspheres (CMs) in the dispersing state was prepared by the emulsification cross-linking
method. The CMs had smooth surface and spherical shape with the diameter of about 124 µm. They were stable after sterilization
at 121°C and 150 kPa for 20 min. The CMs had similar antibacterial activity to that of chitosan in the solution form. Their
antibacterial activities increased with the increase of the CM concentration, while decreased with the increase of pH of the
system. It was found that the CMs with the degree of deacetylation (DD) of 63.6% exhibited the highest antibacterial activity,
while the CMs with the DD of 83.7% exerted the lowest antibacterial activity among the three tested samples.
Frontiers of Materials Science in China 01/2008; 2(2):214-220.
-
[show abstract]
[hide abstract]
ABSTRACT: Oleoylchitosans (O-chitosans), with different molecular masses and degrees of substitution (DS), were synthesized by reacting chitosan with oleoyl chloride. The FT-IR suggested the formation of an amide linkage between amino groups of chitosan and carboxyl groups of oleic acid. The viscosity of O-chitosan sharply increased with the increase of concentration, whereas that of unmodified chitosan rose only slightly. This increase was stronger as the increase of hydrophobicity (DS) and molecular mass of the polymer. The critical aggregation concentration (CAC) of O-chitosans with DS 5, 11, and 27% were 79.43, 31.6, 10 mg/L, respectively, and the CAC of samples with molecular masses of 20, 38, 300, and 1100 kDa were 50.1, 74.93, 125.9, and 630.9 mg/L, respectively. All of the O-chitosans could reduce surface tension slightly. Nanoparticles were prepared using an O/W emulsification method. Mean diameters of the polymeric amphiphilic nanoparticles of O-chitosans with DS 5 and 11% were around 327.4 and 275.3 nm, respectively.
Journal of Agricultural and Food Chemistry 07/2007; 55(12):4842-7. · 2.82 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A novel chitosan antibacterial dispersion system was prepared by oleoyl-chitosan (O-chitosan) nanoparticles (OCNP) and the bactericidal activity against Escherichia coli and Staphylococcus aureus was evaluated by the enumeration of viable organisms at different incubation times. We further investigated the antimicrobial mode of OCNP using a combination of approaches, including cell integrity measurements, outer membrane (OM) and inner membrane (IM) permeabilization assays, SDS–PAGE and transmission electron microscopy (TEM). Results showed that when treated with OCNP, release of intracellular components quickly increased for both E. coli and S. aureus. OCNP also rapidly increased the 1-N-phenylnaphthylamine (NPN) uptake and the release of cytoplasmic β-galactosidase via increasing the permeability of OM and IM. Besides, SDS–PAGE indicated the content of cellular soluble proteins decreased significantly in OCNP-treated bacteria. TEM observations demonstrated adsorption behaviors of OCNP on bacteria and extensive cell surface alterations of OCNP-treated bacteria. OCNP has potential value in the determination of antibacterial mechanism of chitosan.
Carbohydrate Polymers.
-
[show abstract]
[hide abstract]
ABSTRACT: A thermosensitive hydrogel has been prepared with chitosan and αβ-glycerophosphate (αβ-GP) which could be transited from solution into gel at 37 °C. The thermosensitive characteristics, appearance and structure of the hydrogel were affected by concentration, molecular weight and degree of deacetylation (DD) of chitosan. Chitosan, MW 1360 kDa, DD 75.4%, solution concentration 2% was optimal for preparation of chitosan-αβ-glycerophosphate (CS-αβ-GP) thermosensitive hydrogel. The appearance of the hydrogel became more compact and regular with increasing concentration and chitosan MW. Model drugs release from CS-αβ-GP hydrogel prepared by the drug being added into chitosan solution (method I) was slower than that from hydrogel prepared by the drug being directly added into chitosan hydrogel (method II).The release rate for both adriamycin and 6-mercaptopurine from CS-αβ-GP hydrogel decreased with the increase of MW of the chitosan. The hydrophilic model adriamycin was released 60–70% over 24 h which was slower than that of the hydrophobic model 6-mercaptopurine. Therefore it was projected that the CS-αβ-GP hydrogel should be an ideal sustained release system especially for hydrophilic drugs.
Carbohydrate Polymers.
-
[show abstract]
[hide abstract]
ABSTRACT: A novel chitosan antibacterial dispersion system was prepared by oleoyl-chitosan (O-chitosan) nanoparticles (OCNP), and the antibacterial activity against Escherichia coli and Staphylococcus aureus was investigated. Results showed that OCNP could be well distributed in nutrient broth and had strong antibacterial activity. The minimum inhibitory concentrations (MICs) of all OCNP samples ranged from 31.25 to 125 mg/l against E. coli. For S. aureus, the MIC of all samples was 125 mg/l. OCNP of low chitosan molecular weight (MW) appeared most effective against E. coli. For S. aureus, the effect of chitosan MW on the antibacterial activity of OCNP was not pronounced. E. coli was most susceptible to OCNP of O-chitosan with degrees of substitution (DS) 5%, while no marked difference was found among OCNP of O-chitosan with different DS against S. aureus. OCNP exhibited the most pronounced antibacterial activity at pH 6.0 in the experimental range. The integrity of cell membranes was destroyed when bacterial suspensions were treated with OCNP.
Carbohydrate Polymers 74(1):114-120. · 3.63 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Self-aggregation and micelles of amphiphatic polymers are important functions in application, and their properties are influenced by the parent hydrophilic polymer and the hydrophobic groups. In this paper, deoxycholate-chitosan (DE-chitosan) and carboxymethyl-chitosan (CM-chitosan) were prepared from chitosan (MW, 28 kDa; DD, 90%). The effects of acid, pH and ionic concentrations on aggregation behaviors of the polymers in aqueous systems were measured, respectively. The ionic strength was found to enhance the aggregation of DE-chitosan, but had no influence to CM-chitosan and chitosan itself. The modification of hydrophobic groups and hydrophilic groups influenced the rheology properties of both parent chitosan and the derivatives. The assemblage of DE-chitosan in solution can be controlled by an oil/water (methylene chloride/DE-chitosan solution) emulsification process using methylene chloride. The micelles of DE-chitosan formed nano-micelles particles of 200–600 nm in diameter which can be used to encapsulate lipid-soluble compounds for drug dispersing and delivery releasing.
Carbohydrate Polymers.
