Relationship between composition and structure in chitosan-based hybrid films

Impact of Deacetylation Degree on Properties of Chitosan for Formation of Electrosprayed Nanoparticles

Biopolymer of natural origin as chitosan has been studied and applied widely in practice. In the pharmaceutical field, especially, chitosan nanoparticles have been researched for a variety of drug delivery systems. There are many factors influencing the success of the chitosan nanoparticle delivery system. Therein, the specific parameters to the physicochemical nature of chitosan greatly determine the efficiency of its drugs carrier. The degree of deacetylation (DD) of chitosan is one of those parameters. In this study, the influence of DD on chitosan properties was clarified to facilitate the preparation of nanoparticles by the electrospraying method. DD can affect the solubility, crystallinity, and surface tension of chitosan, but it cannot strongly impact the viscosity of chitosan solution as much as the molecular weight (Mv). From these results, M3 chitosan, owning a high DD of 86.70%, and crystalline index of 44%, was dissolved in acetic acid for the collection of electrosprayed nanoparticles. The M3 solution having low viscosity of under 50 mm2/s displayed the easy adjustment of the stable Taylor-cone droplet at the nozzle tip. Particularly, the M3 chitosan solution with a concentration of 1.5 wt.% in acetic acid of 90 wt.% concentration operated at the working condition of 12 kV voltage, a distance between the two electrodes of 10 cm created spherical particles with an average diameter of 338 nm, narrow size distribution. These chitosan nanoparticles can obtain the initial requirement for application as injectable drugs carrier.

Starch as a reinforcement agent for poly(ionic liquid) hydrogels from deep eutectic solvent via frontal polymerization

For the first time, conductive starch/poly(ionic liquid) hydrogels from a polymerizable deep eutectic solvent (DES) by frontal polymerization (FP) were reported. The solubility and dispersibility for starch granules in the polymerizable DES was investigated. The effects of starch content on FP behaviors, mechanical properties and electrical conductivity of composite hydrogels were studied. Results showed that starch could be partially dissolved and dispersed in the DES. Comparing with the pure poly(ionic liquid) hydrogel from DES (the tensile strength was 41 K Pa), the tensile strength of composite hydrogel could increased by 3.07 times and reached 126 K Pa. When the fixed strain was 80 %, its compressive strength could increase by 6 times and reaches 16.8 MPa. The main reason was that there was a strong interfacial interaction between starch and the polymer hydrogel network. The starch/poly(ionic liquid) composite hydrogels also had good electrical conductivity. Absorption of water could increase the conductivity of the composite hydrogel significantly.

Enhancing the electrochromic response of polyaniline films by the preparation of hybrid materials based on polyaniline, chitosan and organically modified clay

Electrochromic materials based on PAni, chitosan and clay show distinct colour variation depending on the compound present in the hybrid material.

Preparation of silver nanoparticles with antimicrobial activities and the researches of their biocompatibilities

Silver nanoparticles were prepared by chemical reduction method using chitosan as stabilizer and ascorbic acid as reducing agent in this work. The silver/chitosan nanocomposites were characterized in terms of their particle sizes and morphology by using UV spectrophotometer, nano-grainsize analyzer, and transmission electron microscopy. Antibacterial activities of these nanocomposites were carried out for Staphylococcus aureus and Escherichia coli. The silver nanoparticles exhibited significantly inhibition capacity towards these bacteria. Detailed studies on the biocompatibility of the silver/chitosan nanocomposites were investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and cell adhesion test. The results indicated that these silver/chitosan nanocomposites were benefit for the proliferation and adhesion of L-929 cells, and the biocompatibilities between the nanocomposites and the cells would become better with the culturing days. We anticipated that these silver/chitosan nanocomposites could be a promising candidate as coating material in biomedical engineering and food packing fields wherein antibacterial properties and biocompatibilities are crucial.

One-step preparation of glycopeptide microspheres based on alpha-amino acid-N-carboxyanhydride polymerization using interfacial protocols

A type of polysaccharide-polypeptide hybrid material, chitin derivative with polypeptide side chains was prepared by the graft copolymerization of L-leucine N-carboxyanhydride triggered by water-soluble chitin (WSC). The studies on surface tension and aggregation demonstrated surface activity of WSC. Using this extraordinary property, the microspheres were synchronously obtained via interfacial polymerization. The method employed here to form the microspheres was in direct contrast to previous syntheses that used either templating method or oil-in-water emulsion. The study provided a facile approach for synthesizing microspheres with a variety of distinct polypeptide and regulated graft length, which had mimetic structure of glycoconjugation in extracellular matrix. Furthermore, the swelling capability of the microsphere in both acidic aqueous and organic solvents would give promising application in drug delivery.

In situ preparation of glycoconjugate hollow microspheres mimics the extracellular matrix via interfacial polymerization

A novel chitin-graft-polyleucine microsphere with hollow construction was prepared via ring-opening polymerization initiated with chitin based on interfacial protocol. The FT-IR and (1)H NMR analysis demonstrated the conjugation with regulated graft length. The study provided a facile one-step route to obtain microsphere with glycoconjugation structure. This hybrid polysaccharide-polypeptide microsphere may give promising application in drug delivery and tissue engineering.

Novel nylon-supported organic–inorganic hybrid membrane with hierarchical pores as a potential immobilized metal affinity adsorbent

Chitosan-based porous organic-inorganic hybrid membranes supported by microfiltration nylon membranes were prepared, in which gamma-glycidoxypropyltrimethoxysilane (GPTMS) was used as an inorganic source as well as crosslinking reagent. Polyethylene glycol (PEG) with different molecular weight and content was used as imprinting molecule for morphology control. In situ crosslinking of chitosan and simultaneous polymerization of GPTMS in PEG template environment endowed the hybrid membrane with specific characteristics. Distinct hybrid effect between chitosan (CS) and GPTMS was revealed by shifting in X-ray diffraction (XRD) pattern, decomposition in simultaneous thermogravimetry and differential scanning calorimetry (TG/DSC) testing. As manifested by scanning electron microscopy (SEM), the molecular weight and content of PEG had remarkable effect on the resulting surface morphology of the hybrid membrane and a given surface morphology could be obtained by extracting of the imprinted PEG molecular. Among three types of porogen used: PEG 400, PEG 4000 and PEG 20000, only PEG 20000 could result in a porous surface. Moreover, a special porous surface with three-dimensional (3D) hierarchical structure-in-structure pore fashion was obtained when content of PEG 20000 was controlled at 15%. Experimental results also showed that the hybrid membrane had low swelling ratio and high stability in acidic solution. After conveniently coordinated with copper ions, the porous metal chelating hybrid membrane could effectively adsorb the model protein, bovine serum albumin (BSA). As expected, the hybrid membrane imprinted with 15% PEG 20000 had remarkably high copper ion binding and BSA adsorption capacity, which might result from the large surface area, high ligand density and suitable interconnected 3D hierarchical porous surface.

Morphology study of gold–chitosan nanocomposites

Gold nanoparticles were prepared in the presence of chitosan via reduction of HAuCl4 with sodium borohydride. The gold-chitosan nanocomposite was formed by adsorbing chitosan molecules onto the gold nanoparticle surfaces. The resulting gold nanoparticles were characterized by transmission electron microscopy and UV-vis spectroscopy. Morphology of gold-chitosan nanocomposite films was investigated by polarized optical microscopy. The morphology of chitosan crystal cast from the prepared nanocomposite was much different from that cast from chitosan solution due to the possible nucleation of gold nanoparticles. A branched-like structure or a cross-linked needle-like structure could be formed in nanocomposite films with different casting volumes.

Preparation and characterization of metal–chitosan nanocomposites

Various metal-chitosan nanocomposites were synthesized, including silver (Ag), gold (Au), platinum (Pt), and palladium (Pd) in aqueous solutions. Metal nanoparticles were formed by reduction of corresponding metal salts with NaBH4 in the presence of chitosan. And chitosan molecules adsorbing onto the surface of as-prepared metal nanoparticles formed the corresponding metal-chitosan nanocomposites. Transmission electron microscopy (TEM) images and UV-vis spectra of the nanocomposites revealed the presence of metal nanoparticles. Comparison of all the resulting particles size, it shows that silver nanoparticles are much larger than others (Au, Pt and Pd). In addition, the difference in particles size leads to develop different morphologies in the films cast from prepared metal-chitosan nanocomposites. Polarized optical microscopy (POM) images show a batonet-like structure for Ag-chitosan nanocomposites film, while for the films cast from other metal (Au, Pt, and Pd)-chitosan nanocomposites, some branched-like structures with a few differences among them were observed under POM observation.