Synthesis of Chitosan Quaternary Ammonium Salts

A series of N-alkyl or N-aryl chitosan quaternary ammonium salts were prepared via Schiffs base intermediates. Quaternization of N-substituted chitosan derivatives was carried out using methyl iodide to produce water-soluble cationic chitosan quaternary ammonium salt. The products were characterized by IR, (HNMR)-H-1 and elemental analysis. The degree of substitution of chitosan quaternary ammonium salt was calculated by elemental analysis.

Superoxide Anion Radical Scavenging Ability of Quaternary Ammonium Salt of Chitosan

A series of N-alkyl or N-aryl chitosan quaternary ammonium salt were prepared using 96% deacetylated chitosan. Their scavenging activities against superoxide anion radical were investigated by chemiluminescence. The IC50 values of these compounds range from 280 to 880 μg/mL, which should be attributed to their different substitutes.

Preparation and Properties of Poly(amidoamine) Dendrimer/Quaternary Ammonium Chitosan Hydrogels

A novel quaternary ammonium chitosan hydrogel modified by poly（amidoamine）（PAMAM） dendrimer was prepared by using glutaraldehyde as a cross-linker. The hydrogel was characterized by Fourier transform infrared spectroscopy（FTIR） and scanning electron microscopy（SEM）. The results confirmed its highly porous three-dimensional network structure. The swelling test of hydrogel proved that it had excellent swelling and p H-sensitive properties. The increasing PAMAM content or quaternization degree led to the increase in swelling properties. And the hydrogel with lower cross-linking agent concentration or quaternary ammonium chitosan concentration exhibited better swelling properties. The antibacterial results indicated that with the increase in the PAMAM content, quaternary ammonium chitosan concentration or cross-linking agent concentration, the hydrogels showed better antibacterial activities against both Staphylococcus aureus（S. aureus） and Escherichia coli（E. coli）. Thus, the hydrogel could serve as a promising antibacterial material in the future.

Synthesis and Characterization of a Novel Liquid Crystalline Chitin Quaternary Ammonium Chitosan Salt

N -Butyl chitosan(NBCS) derivatives were prepared by introducing butyl groups into the amine groups of chitosan via Schiff base intermediates. The quaternization of NBCS was carried out by using ethyl iodide to produce water-soluble cationic polyelectrolytes. The degree of the substitution of the products was measured by means of the electron spectroscopy for a successful chemical analysis. The quaternary ammonium chitosan salt(QACS) was proved to be a novel cholesteric liquid crystalline chitin, by means of the polarized optical microscopy and the circular dichroism spectropolarimetry. The critical mass fraction of the QACS/formic acid solution forming a lyotropic liquid crystal phase was 50%, which was almost the same as that of the NBCS/formic acid solution, but much higher than that of the chitosan in the same solvent.

Chemically modified magnetic chitosan microspheres for Cr（VI） removal from acidic aqueous solution

A bioadsorbent composed of magnetic silica nanoparticles encapsulated by chitosan microspheres was prepared by the emulsion cross-linking method, and it was then modified with quaternary ammonium groups by reaction with ethylenediamine and glycidyl trimethylammonium chloride. Characterization of the bioadsorbent indicated that it was highly acid resistant and magnetically responsive. The bioadsor- bent was then used to remove Cr（VI） from acidic aqueous solution. The results of batch experiments indicated that the optimal pH value was 2.5, and the adsorbent exhibited low pH dependence. The maximum adsorption capacity was 233.1mg/g at pH 2.5 and 25 ℃, and the equilibrium time was deter- mined to be 40-120 min depending on the initial Cr（VI） concentration. The adsorbent could be effectively regenerated using a mixture of 0.3 mol/L NaOH and 0.3 mol/L NaCI with a desorption efficiency of 95.6%, indicating high reusability. In conclusion, the bioadsorbent shows potential for Cr（VI） removal from acidic

Enhanced tissue regeneration through immunomodulation of angiogenesis and osteogenesis with a multifaceted nanohybrid modified bioactive scaffold

Major traumatic tissue defects are common clinical problems often complicated by infection and local vascular dysfunction, processes which hinder the healing process. Although local application of growth factors or stem cells through various tissue engineering techniques are promising methods for the repair of tissue defects, limitations in their clinical application exist. Herein, we synthesized multifaceted nanohybrids composed of Quaternized chitosan (QCS), Graphene oxide (GO), and Polydopamine (PDA;QCS-GO-PDA). Covalent grafting of QCS and GO at a mass ratio of 5:1 (5QCS-1GO) displayed excellent biocompatibility and enhanced osteogenic ability, while addition of PDA (5QCS-1GO-PDA) reduced the level of reactive oxygen species (ROS). 5QCS-1GO-PDA was able to achieve wound tissue regeneration by reducing the inflammatory response and enhancing angiogenesis. Furthermore, Polylactic acid/hydroxyapatite (PLA/HA) composite scaffolds were printed using Selective Laser Sintering (SLS) and the hybrid nanomaterial (5QCS-1GO-PDA) was used to coat the PLA/HA scaffold (5QCS-1GO-PDA@PLA/HA) to be used for rapid bone regeneration. 5QCS-1GO-PDA not only improved angiogenesis and osteogenic differentiation, but also induced M2-type polarization of macrophages and promoted bone regeneration via the BMP2/BMPRs/Smads/Runx2 signaling pathway. The bidirectional enhanced healing ability of the multifaceted nanohybrids 5QCS-1GO-PDA provides a promising method of effectively treating tissue defects.