Manufacturing N,O-carboxymethyl chitosan-reduced graphene oxide under freeze-dying for performance improvement of Li-S battery

Lithium-sulfur(Li-S) batteries can provide far higher energy density than currently commercialized lithium ion batteries, but challenges remain before it they are used in practice.One of the challenges is the shuttle effect that originates from soluble intermediates, like lithium polysulfides. To address this issue, we report a novel laminar composite, N,O-carboxymethyl chitosan-reduced graphene oxide(CC-rGO), which is manufactured via the self-assembly of CC onto GO and subsequent reduction of GO under an extreme condition of 1 Pa and-50°C. The synthesized laminar CC-rGO composite is mixed with acetylene black(AB) and coated on a commercial polypropylene(PP) membrane, resulting in a separator(CC-rGO/AB/PP) that can not only completely suppress the polysulfides penetration, but also can accelerate the lithium ion transportation, providing a Li-S battery with excellent cyclic stability and rate capability. As confirmed by theoretic simulations, this unique feature of CC-rGO is attributed to its strong repulsive interaction to polysulfide anions and its benefit for fast lithium ion transportation through the paths paved by the heteroatoms in CC.

LOW MOLECULAR WEIGHT O-CARBOXYMETHYLATED CHITOSANS DERIVED FROM IRRADIATED CHITOSAN AND THEIR ANTIBACTERIAL ACTIVITY

Original chitosan with M-v of 2.7 x 10(5) was degraded by irradiation with gamma-rays and a series of low molecular weight O-carboxymethylated chitosans (O-CMCh) were prepared based on the irradiated chitosan. A kinetic model of the irradiation of chitosan was put forward. Results show that the irradiation degradation of chitosan obeys the rule of random degradation and the degree of deacetylation of irradiated chitosan is slightly raised. The antibacterial activity of O-CMCh is significantly influenced by its MW, and a suppositional antibacterial peak appears when M-v is equal to 2 x 10(5).

Apoptosis of A549 cells by small interfering RNA targeting survivin delivery using poly-β-amino ester/guanidinylated O-carboxymethyl chitosan nanoparticles

Gene-based therapeutics has emerged as a promising approach for human cancer therapy. Among a variety of non-viral vectors, polymer vectors are particularly attractive due to their safety and multivalent groups on their surface. This study focuses on guanidinylated O-carboxymethyl chitosan(GOCMCS) along with poly-β-amino ester(PBAE) for si RNA delivery. Binding efficiency of PBAE/si RNA/GOCMCS nanoparticles were characterized by gel electrophoresis. The si RNA-loaded nanoparticles were found to be stable in the presence of RNase A, serum and BALF respectively. Fine particle fraction(FPF) which was determined by a two-stage impinger(TSI) was 57.8% ± 2.6%. The particle size and zeta potential of the nanoparticles were 153.8 ± 12.54 nm and + 12.2 ± 4.94 m V. In vitro cell transfection studies were carried out with A549 cells. The cellular uptake was significantly increased. When the cells were incubated with si Survivin-loaded nanoparticles, it could induce 26.83% ± 0.59% apoptosis of A549 cells and the gene silencing level of survivin expression in A549 cells were 30.93% ± 2.27%. The results suggested that PBAE/GOCMCS nanoparticle was a very promising gene delivery carrier.

Preparation and Compressive Strength of Calcium Phosphate Bone Cement Containing N,O-carboxymethyl Chitosan

N, O-carboxymethyl chitosan （ CMCTS ）, a kind of biodegradable organic substance, was added to calcium phosphate bone cement （CPC） to prodnce a composite more similar in composition to human bone. The compressive strength of the new material was inereased by 10 times compared with conventional CPC.

Adsorption of Pharmaceutical Contaminants from Aqueous Solutions Using N,O-Carboxymethyl Chitosan/Polyethylene Oxide (PEO) Electrospun Nanofibers

Residues of pharmaceutical and direct metabolites discharged into the aquatic environment have become a challenge for wastewater treatment facilities due to their increase in concentration and their different physicochemical properties. These emerging contaminants are daily detected in surface water and wastewater discharged by municipalities. To remediate the contaminated water, various methods are currently used including primary, secondary, and tertiary advanced treatments. However, some economic and environmental limitations have forced the scientific community to develop alternative disinfection processes to purify wastewater. As such, the adsorption strategy represents a “green” low-cost and effective solution to remove pollutants from water. In this study, a nanomaterial made of N,O-carboxymethyl chitosan (N,O-CMCS) was prepared using chitosan (CS) and monochloroacetic acid under various conditions. N,O-CMCS electrospun was synthetized with the copolymer polyethylene oxide (PEO) to create nanofiber membranes showing a better specificity toward diversified contaminants depending on the pH of medium. The developed adsorbent was used to remove fluoxetine (FLX) from aqueous solutions. The new nanomaterial was characterised using FTIR, NMR, and SEM techniques. Sorption batch tests were carried out using high-performance liquid chromatography and ultraviolet diode array detector (HPLC-UV DAD) under controlled pH experimental conditions to determine the contaminant removal capacity of the nanomaterial. The promising adsorption results obtained with N,O-CMCS/PEO nanofibers are among the best ones obtained so far in comparison to other commercial and synthetized adsorbents tested for FLX’s adsorption. Kinetic experiments were also performed to investigate effects of contact times on the FLX adsorption. Experimental results were fitted to both common kinetic models pseudo-first and second order. The latter kinetic model described the best the sorption on surface. It revealed a possible chemisorption mechanism with electrostatic bounding for N,O-CMCS/PEO nanofibers.

Chemical modification of L-asparaginase with N, O-carboxymethyl chitosan and its effects on plasma half-life and other properties

E.coli L-asparaginase,an antitumor enzyme,was chemically modified with N,O-carboxymethyl chitosan to lower its artigenicity and increase its plasma half-life.The results showed that the modified L-asparaginase has almost the same apparent Km value as that of native enzyme.The modified L-asparaginase also showed a higher protease stability against trypsin and a-chymotrypsin.After being modified,the enzyme exhibited the complete loss of antigenicity towards antiasparaginase serum.In addition,the higher the molecular weight of modifying reagents,the better the effects on reduction of antigenicity.When tested in vivo,the plasma half-life of the modified enzyme (t1/2=40 h) was over 33 times longer than that of the native enzyme (t1/2=1.2 h).

Nano Calcium-Deficient Hydroxyapatite/O-carboxymethyl Chitosan-CaCl_(2) Microspheres Loadedwith RheinforBone Defect Repair

Glutaraldehyde(GA),the most widely used crosslinking agent for biomaterials,is cytotoxic.CaCl_(2) is of particular interest due to its non-toxic nature.Rhein can chelate Ca^(2+)and promote bone growth.Here we reported a novel nano calcium-deficient hydroxyapatite/O-carboxymethyl chitosan-CaCl_(2) microspheres loaded with rhein(RH-nCDHA/OCMC-CaCl_(2) microspheres)using CaCl_(2) as crosslinking agent for bone defect repair.The obtained microspheres were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),thermogravimetric analysis(TG)and Fourier transform infrared spectroscopy(FT-IR).The surface of the obtained microspheres is rough with quite a few voids.The nano calcium-deficient hydroxyapatite(nCDHA)accounts for about 70% of the total weight of the microspheres,which is equivalent to the proportion of inorganic substances in human bones.A high encapsulation efficiency(EE)and loading capacity(LC)of the microspheres loaded with rhein was 90.20±0.60% and 11.03±0.30%,respectively.For microspheres using CaCl_(2) in simulated body fluid(SBF)after 14 days,the drug released continuously and bone-like apatite formed like layer.The cells on the surface of the RH-nCDHA/OCMC-CaCl_(2) microspheres grew better comparing with nCDHA/OCMC-GA microspheres and the skull defects of rats after landfill can be almost repaired after 8 weeks,which revealed the potential of the microspheres for bone repair.