Yumin Du

Effect of molecular structure of chitosan on protein delivery properties of chitosan nanoparticles

Chitosan nanoparticles (CS NP) with various formations were produced based on ionic gelation process of tripolyphosphate (TPP) and chitosan. They were examined with diameter 20-200 nm and spherical shape using TEM. FTIR confirmed tripolyphosphoric groups of TPP linked with ammonium groups of chitosan in the nanoparticles. Factors affecting delivery properties of bovine serum albumin (BSA) as model protein have been tested, they included molecular weight (Mw) and deacetylation degree (DD) of chitosan, the concentration of chitosan and initial BSA, and the presence of polyethylene glycol (PEG) in encapsulation medium. Increasing Mws of chitosan from 10 to 210 kDa, BSA encapsulation efficiency was enhanced about two times, BSA total release in PBS (phosphate buffer saline) pH 7.4 in 8 days was reduced from 73.9 to 17.6%. Increasing DD from 75.5 to 92% promoted slightly the encapsulation efficiency and decelerated the release rate. The encapsulation efficiency was highly decreased by increase of initial BSA and chitosan concentration; higher loading capacity of BSA speeded the BSA release from the nanoparticles. Adding PEG hindered the BSA encapsulation and accelerated the release rate.

Enzymic preparation of water-soluble chitosan and their antitumor activity

Water-soluble low-molecular-weight (LMW) chitosan was prepared from enzymatic hydrolysis with efficient hemicellulase. The hydrolysates were separated by ultrafiltration membranes. A separated fraction with Mw more than 5x10(3) and with a degree of deacetylation of 58% was water-soluble in the free amine form. The intraperitoneal injection of LMW chitosan and its N-acetyl product inhibited the growth of sacroma 180 (S180) tumor cells in the mice, and the maximum inhibitory rate reached 64.2%. The oral administration was also effective on decreasing weight of tumor, and the maximum inhibitory rate reached 33.7%. The Water-soluble chitosan with higher Mw than hexamer might have better antitumor activity.

Effect of hydrogen peroxide treatment on the molecular weight and structure of chitosan

Abstract The degradation of chitosan by hydrogen peroxide was studied. The degradation was monitored by gel permeation chromatography (GPC). The molecular weight distribution of partially degraded products from homogeneous reaction displayed a single-modal curve whereas that from heterogeneous reaction was bimodal. The molecular weight (Mw) decreased as the temperature, the time and/or hydrogen peroxide concentration increased. The dissolution of chitosan (pH 5.5) in minimum hydrochloride enhanced its degradation, but excessive hydrogen ion potentially inhibited the degradation. The formation of carboxyl group and deamination in the products indicated that the decrease of Mw was accompanied by structure changes. The degraded chitosans in Mw range from 51×103 to 1.2×103 were characterized by elemental analysis, X-ray diffraction, thermogravimetric analysis (TGA) and differential thermal analysis (DTA), Fourier transform infrared (FT–IR), carbon-13 nuclear magnetic resonance spectroscopy (13C-NMR). There was no significant chemical change in the backbone of chitosan with Mw of 51×103. But degraded chitosan with Mw of 3.5×103 had 1.71 mmol/g carboxyl groups and lost about 15% of amino groups. Further degradation led to more ring-opening oxidation of degraded products, the formation of carboxyl groups and faster deamination. The degraded chitosan with Mw of 1.2×103 had 2.86 mmol/g carboxyl groups and lost more than 40% of amino groups.

Preparation and modification of N-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride nanoparticle as a protein carrier

N-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (HTCC) is water-soluble derivative of chitosan (CS), synthesized by the reaction between glycidyl-trimethyl-ammonium chloride and CS. HTCC nanoparticles have been formed based on ionic gelation process of HTCC and sodium tripolyphosphate (TPP). Bovine serum albumin (BSA), as a model protein drug, was incorporated into the HTCC nanoparticles. HTCC nanoparticles were 110-180 nm in size, and their encapsulation efficiency was up to 90%. In vitro release studies showed a burst effect and a slow and continuous release followed. Encapsulation efficiency was obviously increased with increase of initial BSA concentration. Increasing TPP concentration from 0.5 to 0.7 mg/ml promoted encapsulation efficiency from 46.7% to 90%, and delayed release. As for modified HTCC nanoparticles, adding polyethylene glycol (PEG) or sodium alginate obviously decreased the burst effect of BSA from 42% to 18%. Encapsulation efficiency was significantly reduced from 47.6% to 2% with increase of PEG from 1.0 to 20.0 mg/ml. Encapsulation efficiency was increased from 14.5% to 25.4% with increase of alginate from 0.3 to 1.0 mg/ml.

Biopolymer/montmorillonite nanocomposite: preparation, drug-controlled release property and cytotoxicity

In order to combine the advantages of a biopolymer with clay in a drug delivery system, the hot intercalation technique was used to prepare quaternized chitosan/montmorillonite (HTCC/MMT) nanocomposites. Transmission electron microscopy (TEM), x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) results revealed that HTCC chains entered into the interlayer of MMT, and the interaction between them has taken place. This is the basis of the advantage combination. Then the HTCC/MMT nanocomposites were modified to prepare the nanoparticles, whose drug-controlled release behaviours were evaluated. The results suggested that, compared to pure HTCC nanoparticles, certain montmorillonite loadings on quaternized chitosan enhanced the drug encapsulation efficiency of the nanoparticles and slowed the drug release from the nanocomposites. Finally, a study of 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) indicated that the nanocomposites are not cytotoxic. Therefore, the HTCC/MMT nanocomposites are of great potential in the biomedical field.

The physicochemical properties and antitumor activity of cellulase-treated chitosan

Cellulase was used to partially hydrolyse N-acetylated chitosan. The hydrolysis process was monitored by gel permeation chromatography. Factors affecting the enzymatic hydrolysis of chitosan were studied. The degraded chitosans were characterized by X-ray diffraction, thermogravimetric analysis, differential thermal analysis, Fourier transform infrared and carbon-13 magnetic resonance spectra. The results showed that the enzymatic hydrolysis was by endo-action, and the total acetylation degree of chitosan did not change after degradation. The decrease of molecular weight led to transformation of crystal structure, alteration of thermostability and increase of water-solubility, but the chemical structures of residues were not modified. Most reducing endresidues of produced oligomers were GlcNAc units. This water-soluble product inhibited the growth of sarcoma180 tumor cells in mice with maximum inhibitory rates of 50% by intraperitoneal injection and 31% by oral administration. # 2003 Elsevier Ltd. All rights reserved.

Influence of functional groups on the in vitro anticoagulant activity of chitosan sulfate

A new method for the chemical modification of chitosan sulfate was used to prepare N-propanoyl-, N-hexanoyl- and N,O-quaternary substituted chitosan sulfate. Structural analysis by elemental analysis, FTIR, 13C NMR, and 1H NMR spectroscopy, and gel-permeation chromatography showed that these methods could conveniently be used for the introduction of functional groups. The influences of the acyl or quaternary groups on the anticoagulant activity of the polysaccharides were studied with respect to activated partial thromboplastin time (APTT) thrombin time (TT), and prothrombin time (PT). The propanoyl and hexanoyl groups increased the APTT activity, and the propanoyl groups also increased the TT anticoagulant activity slightly, while the N,O-quaternary chitosan sulfate showed only a slight TT coagulant activity.

Controlling the functional performance of emulsion-based delivery systems using multi-component biopolymer coatings

The digestion and release of bioactive lipophilic components encapsulated within emulsion-based delivery systems can be controlled by coating the lipid droplets with biopolymer coatings. In this study, multi-component biopolymer coatings were formed around lipid droplets using an interfacial electrostatic deposition approach. These coatings consisted of an inner layer of globular protein (beta-lactoglobulin), an intermediate layer of cationic polysaccharide (chitosan), and an outer layer of anionic polysaccharide (pectin or alginate). In the absence of the outer anionic polysaccharide layer, the protein-chitosan-coated droplets were highly unstable to aggregation at high pH values (pH>6), due to loss of chitosan charge. In the presence of the outer layer, the droplets had good stability to aggregation from pH 7 to 4, but aggregated at lower pH due to loss of pectin or alginate charge. An in vitro lipid digestion model (pH stat) indicated that polysaccharide coatings reduced the rate of lipid digestibility. These findings have important implications for the design of delivery systems for bioactive lipophilic components in the pharmaceutical, biopharmaceutical, and food industries.

Chemical modification, characterization and structure-anticoagulant activity relationships of Chinese lacquer polysaccharides.

A natural lacquer polysaccharide with complex branches was separated into two fractions, LPH (MW 16.9x10(4)) and LPL (MW 6.85x10(4)). Results of 13C NMR and FT-IR indicated they had the same structure. The treatment of LPL with sodium periodate led to a partial cut-off of side chains with 4-O-methyl-D-glucuronic acid in the terminal. These polysaccharides were sulfated in the presence of Py*SO3/DMSO. Depending on the reaction conditions, the products showed a different degree of sulfation (DS) ranging from 0.57 to 1.57 and different molecular weights ranging from 1.71x10(4) to 3.49x10(4). FT-IR analysis showed the equatorial primary OH at O-6 and the axial secondary OH at O-4 were sulfated. Activated partial thromboplastin time (APTT), prothrombin time and thrombin time (TT) assays showed the sulfated polysaccharides could prolong APTT and TT, but not TP. These activities strongly depended on the DS, the molecular weights (MW) and the branching structure of polysaccharides. DS of above 0.8 was essential for anticoagulant activity. The anticoagulant activity increased with the DS and the molecular weights. The molecular weights played a more important role. The branching structure of polysaccharides increased the activities. In our studies, the sulfated polysaccharides with the DS of 1.15 and the highest MW of 3.49x10(4) had the best blood anticoagulant activities.

Facile preparation of robust and biocompatible chitin aerogels

Chitin, poly(N-acetylglucosamine), was fabricated into nanoporous aerogels by using aqueous NaOH–urea solution as solvent and ethanol as coagulant. The chitin solution showed rapid temperature-induced gelation. Subsequently, highly porous and mechanically strong chitin aerogels were prepared by gelation of chitin solution from ethanol, followed by supercritical CO2 drying. The chitin hydrogel was composed of a percolating nanofibril network of about 20 nm width. By using supercritical CO2 drying, the network structure in the hydrogel was well preserved in the aerogel. Our chitin aerogels exhibit low density (0.23–0.27 g cm−3), large surface area (up to 366 m2 g−1), moderate thermal stability and high physical integrity up to 270 °C, significantly high mechanical properties, and biocompatibility. Our findings are expected to lead to potential applications of chitin aerogels and allow for the fabrication of biomaterials, heat or sound insulators, catalyst supports and many others.