Preparation and Antimicrobial Activity of Chitosan and Its Derivatives: A Concise Review

Despite the advantages presented by synthetic polymers such as strength and durability, the lack of biodegradability associated with the persistence in the environment for a long time turned the attention of researchers to natural polymers. Being biodegradable, biopolymers proved to be extremely beneficial to the environment. At present, they represent an important class of materials with applications in all economic sectors, but also in medicine. They find applications as absorbers, cosmetics, controlled drug delivery, tissue engineering, etc. Chitosan is one of the natural polymers which raised a strong interest for researchers due to some exceptional properties such as biodegradability, biocompatibility, nontoxicity, non-antigenicity, low-cost and numerous pharmacological properties as antimicrobial, antitumor, antioxidant, antidiabetic, immunoenhancing. In addition to this, the free amino and hydroxyl groups make it susceptible to a series of structural modulations, obtaining some derivatives with different biomedical applications. This review approaches the physico-chemical and pharmacological properties of chitosan and its derivatives, focusing on the antimicrobial potential including mechanism of action, factors that influence the antimicrobial activity and the activity against resistant strains, topics of great interest in the context of the concern raised by the available therapeutic options for infections, especially with resistant strains.     

Single and ternary nanocomposite electrodes of Mn3O4/TiO2/rGO for supercapacitors

Journal of Solid State Electrochemistry - Graphene (G) and ternary nanocomposites of Mn3O4, TiO2, and reduced graphene oxide(rGO) electrodes have been prepared for supercapacitor applications. The...     

ZnAl2O4 SiO2纳米复合催化剂用于无溶剂条件下乙酸酐与醇、酚和胺的乙酰化反应简

A ZnAl₂O₄@SiO₂ nanocomposite was prepared from metal nitrates and tetraethyl orthosilicate by the sol-gel process, and characterized by X-ray diffraction, Fourier transform infrared, transmission electron microscopy, and N₂ adsorption-desorption measurements. The nanocomposite was tested as a heterogeneous catalyst for the acetylation of alcohols, phenols, and amines under solvent-free conditions. Under optimized conditions, efficient acetylation of these substrates with acetic anhydride over the ZnAl₂O₄@SiO₂ nanocomposite was obtained. Acetylation of anilines and primary aliphatic amines proceeded rapidly at room temperature, while the reaction time was longer for the acetylation of alcohols and phenols, showing that an amine NH₂ group can be selectively acetylated in the presence of alcoholic or phenolic OH groups. The catalyst can be reused without obvious loss of catalytic activity. The catalytic activity of the ZnAl₂O₄@SiO₂ nanocomposite was higher than that of pure ZnAl₂O₄. The method gives high yields, and is clean, cost effective, compatible with substrates having other functional groups and it is suitable for practical organic synthesis.     

ZnAl_2O_4@SiO_2纳米复合催化剂用于无溶剂条件下乙酸酐与醇、酚和胺的乙酰化反应(英文)

A ZnAl2O4@SiO2 nanocomposite was prepared from metal nitrates and tetraethyl orthosilicate by the sol-gel process,and characterized by X-ray diffraction,Fourier transform infrared,transmission electron microscopy,and N2 adsorption-desorption measurements.The nanocomposite was tested as a heterogeneous catalyst for the acetylation of alcohols,phenols,and amines under solvent-free conditions.Under optimized conditions,efficient acetylation of these substrates with acetic anhydride over the ZnAl2O4@SiO2 nanocomposite was obtained.Acetylation of anilines and primary aliphatic amines proceeded rapidly at room temperature,while the reaction time was longer for the acetylation of alcohols and phenols,showing that an amine NH2 group can be selectively acetylated in the presence of alcoholic or phenolic OH groups.The catalyst can be reused without obvious loss of catalytic activity.The catalytic activity of the ZnAl2O4@SiO2 nanocomposite was higher than that of pure ZnAl2O4.The method gives high yields,and is clean,cost effective,compatible with substrates having other functional groups and it is suitable for practical organic synthesis.     

Synthesis and characterization of water-soluble palladium(II)-functionalized diphosphine complexes

Water-soluble functionalized bis(phosphine) ligands L (a–h) of the general formula CH₂(CH₂PR₂)₂, where for a: R = (CH₂)₆OH; b–g: R = (CH₂)_nP(O)(OEt)₂, n = 2–6 and n = 8; h: R = (CH₂)₃NH₂ ( Scheme 1), have been prepared photochemically by hydrophosphination of the corresponding 1-alkenes with H₂P(CH₂)₃PH₂. Water-soluble palladium complexes cis-[Pd(L)(OAc)₂] (1–8) were obtained by the reaction of Pd(OAc)₂ with the ligands a–h in a 1:1 mixture of dichloromethane:acetonitrile. The water-soluble phosphine ligands and their palladium complexes were characterized by IR, ¹H and ³¹P NMR. A crystallographic study of complex 1 shows that the Pd(II) ion has a square planar coordination sphere in which the acetate ligands and the diphosphine ligand deviate by less than 0.12 Å from ideal planar.     

Synthesis,antibacterial evaluation and survey on the thermophysical characteristics of novel medically applicable polyamides containing pharmaceutically outstanding triazole moieties

There are many different strategies to decrease the incidence of infection of medical device and food related containers. One way to prevent infection is by modifying the polymers used in making the devices and containers. Incorporation of antimicrobial agents in the bulk material or in formulations of medical devices production has been considered a viable alternative for systemic application of antibiotics. In this article, preparation of a series of triazole containing polymers, poly(triazole-amide-imide)s (PTAI)s and poly(triazole-amide) (PTA)s, and their monomers are reported. These polymers were readily soluble in a variety of organic solvents, showed significant thermal properties and also viscosities in the range of 0.55–0.66 dL/g. They have been tested against a range of Gram-positive and Gram-negative pathogens. The results indicated that these novel polymers containing triazole moiety in their repeating units can effectively control Gram-positive and negative pathogens and their physic-chemical properties besides their antibacterial characteristics make them unique candidate for using in the manufacturing of the medical devices.     

Synthesis and properties of polyimides derived from a new diamine containing bulky-flexible pendent group

Novel aromatic polyimides containing bulky-flexible pendent group were successfully synthesized by direct polycondensation of N-(4-(4-(4,5-diphenyl-1H-imidazole-2-yl)phenoxy)phenyl)-3,5-diaminobenzamide with various tetracarboxylic dianhydrides. These polymers are soluble in most of the aprotic organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, dimethylsulfoxide, N,N-dimethylacetamide, hexamethylphosphoramide, m-cresol, and pyridine. The prepared polymers were characterized by viscometry, FT-IR, ¹H NMR, and UV-Vis spectroscopy, fluorimetry, elemental analysis; the thermal properties were evaluated by differential scanning calorimetric and thermogravimetric analysis.     

Radiation synthesis of starch-acrylic acid–vinyl sulfonic acid/multiwalled carbon nanotubes composite for the removal of 134Cs and 152+154Eu from aqueous solutions

Starch-acrylic acid-co-vinyl sulfonic acid/multiwalled carbon nanotubes (starch-AA-VSA/f-MWCNTs) bionanocomposite was successfully synthesized using gamma radiation for initiate the grafting of AA/VSA on starch in the presence of f-MWCNTs by template polymerization technique. The structural characteristics were confirmed by FTIR, SEM, and TGA. The adsorption behaviors of bionanocomposite toward Eu(III) and Cs(I) were examined using the batch adsorption experiments. Langmuir and Freundlich’s models were used to fit the experimental data of the adsorption isotherms. Kinetic studies showed that the adsorption data followed the pseudo-second-order model. Thermodynamic studies indicated that the reaction was favorable at high temperature and endothermic process.

     

Headspace SPME–GC Method for Acetone Analysis and its Biomedical Application

A new method for extraction and analysis of acetone in human urine based on headspace solid phase microextraction using a mixture of activated carbon and zeolite as sorbents in a PVC matrix coated on a silver wire and its application to the determination of ketone bodies is described. Unlike commercial fibers, which are coated on fused silica, the coating adheres strongly to the silver wire and is thermally stable up to 250 °C. After optimization of coating composition and microextraction conditions the fiber was used for the analysis of acetone in human urine.