El-Refaie Kenawy

Biologically active polymers: synthesis and antimicrobial activity of modified glycidyl methacrylate polymers having a quaternary ammonium and phosphonium groups

Polymers with antibacterial activity have been synthesized by chemical modification of poly(glycidyl methacrylate). The glycidyl methacrylate was polymerized by the free radical polymerization technique. The poly(glycidyl methacrylate) was hydrolyzed and was chloroacetylated using chloroacetyl chloride. The chloroacetylated product was modified to yield polymers with either quaternary ammonium or phosphonium salts. The antimicrobial activity of the modified glycidyl methacrylate polymers has been examined against a variety of test microorganisms by the cut plug and the viable cell counting methods using shake flask of ten times diluted nutrient broth medium. All three polymers obtained were inhibitory to the growth of Gram negative bacteria (Escherichia coli, Pseudomones aeruginosa, Shigella sp. and Salmonella typhae) and Gram positive bacteria (Bacillus subtilis and B. cereus) as well as the fungus (Trichophytun rubrum). It was found that the growth inhibitory effect varied according to the structure of the polymer and the composition of the active group and increased with increasing the concentration of the polymer. The tested polymers showed more antimicrobial activity against Gram negative bacteria and the fungus, whereas were less active against Gram positive bacteria.

A review on polymeric hydrogel membranes for wound dressing applications: PVA-based hydrogel dressings

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Biologically Active Polymers: Modification and Anti-microbial Activity of Chitosan Derivatives:

The principal derivative of chitin is chitosan, which is obtained by deacetylation of chitin. Chemical modification of synthetic and natural polymers is a convenient way to obtain materials with unique chemical and physical properties. Chitosan has an amino group at C-2 which is important because amino groups are nucleophilic and readily react with electrophilic reagents. Chitosan modified under mild conditions often results in regioselectivity for the C-2 amino group. In the present work, this reactivity was exploited to attach biologically active moieties into the amino groups of chitosan to yield anti-microbial chitosans. Specifically, vanillin, p-hydroxybenzaldehyde, p-chlorobenzaldehyde, anisaldehyde, methyl 4-hydroxybenzoate, methyl 2,4-dihydroxybenzoate, propyl 3,4,5-trihydroxybenzoate and 2-hydroxymethylbenzoate were attached. The anti-microbial activity of these modified chitosans was explored against fungi such as Candida albicans SC5314, Aspergillus flavus and Fusarium oxysporium. Also, they were tested against bacteria such as Bacillus subtilis, Escherichia coli and Staphylococcus aureus. These modified chitosans were found to be highly active toward fungi species more than bacterial species.

Nanospider technology for the production of nylon-6 nanofibers for biomedical applications

Nylon-6 nanofiber mat incorporated with 5,5-dimethyl hydantoin (DMH) as an antimicrobial drug was electrospun from formic acid. The morphology of the nanofiber mat using scanning electron microscope (SEM) showed that the obtained fiber had an average diameter of around 15-328 nm. The nanofiber was characterized by FTIR spectra, TGA, and DSC. The nanofiber containing drug showed initial fast release. It released about 55% of its drug content within the first two hours. Moreover, the antimicrobial activity of the electrospun nylon-6 nanofiber containing drug was examined against Escherichia coli, Pseudomonas aeruginosa, Aspergillus niger, and Aspergillus flavus. The nylon-6 nanofiber exhibited high inhibitory effects against the microbes. The results clearly indicate that the antimicrobial activity of the electrospun nylon-6 nanofiber containing drug varies with the species of the organisms used. Thus, the study ascertains the value of the use of electrospun nanofiber, which could be of considerable interest to the development of new antimicrobial materials. The microbes, examined by SEM, were totally deformed and exhibited severe destruction. Abnormal cell division was observed at high frequencies among cells that tried to divide in the presence of the nanofiber. Many cells were enlarged, elongated, empty ghosts, or fragmented, consistent with the extremely low viability.

Fabrication of electrospun antimicrobial nanofibers containing metronidazole using nanospider technology

Nanospider technology as a modified electrospinning technique was used for the fabrication of electrospun nanofibers based on poly(vinyl alcohol) (PVA)/poly(ethylene oxide) (PEO) blend as drug delivery system (DDS) for metronidazole (MTZ) as an antimicrobial drug. Electrospun PVA/PEO/MTZ composite nanofibers were stabilized against disintegration in water by heating in oven at 110°C, or by soaking in isopropyl alcohol for 6 hrs. Incorporation of MTZ into electrospun nanofibers was confirmed by SEM, FT-IR spectra and TGA. The drug release results showed that the burst release was suppressed with stabilized electrospun nanofibers compared with non-stabilized ones. Electrospun PVA/PEO/MTZ composite nanofibers exhibited remarkable antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, Aspergillus niger, Penicillium notatum and Aspergillus flavus which varies with the species of the tested organisms.

Controlled release of polymer conjugated agrochemicals. system based on poly(methyl vinyl ether-alt-maleic anhydride)

Controlled release formulations were prepared by using commercially available poly(methyl vinyl ether-alt-maleic anhydride) (I) and 2,4-dichlorophenoxy acetic acid herbicide (2,4-D). The copolymer (I) was reacted with various diamines to produce amido-amine containing carboxylate copolymers. The produced copolymers were reacted with the acid chloride of herbicide 2,4-D as model herbicide for carboxylic group functionalized herbicides. The formulations produced were characterized by IR and elemental analyses. The release of the herbicide 2,4-D from the formulations was studied under different aqueous medium conditions and the effect of copolymer microstructure on release profiles was investigated.

Synthesis and characterization of novel inorganic-organic hybrid Ru(II) complexes and their application in selective hydrogenation.

Novel Ru(II) complex-based hybrid inorganic-organic materials immobilized via a diamine co-ligand site instead of the conventional diphosphine ligand have been prepared. The complexes were prepared by two different methods: sol-gel and surface modification techniques. The structures of the desired materials were deduced by several available physical measurements like elemental analyses, infrared, FAB-MS and 1H-, 13C- and 31P-NMR spectroscopy. Due to a lack of solubility the structures of xerogel 3 and modified 4 were studied by solid state 13C-, 29Si- and 31P-NMR spectroscopy, infrared spectroscopy and EXAFS. These materials were stable enough to serve as hydrogenation catalysts. Selective hydrogenation of functionalized carbonyls in α,β-unsaturated compounds was successfully carried out under mild conditions in a basic medium using these complexes as catalysts.

Controlled release of 5-aminosalicylic acid (5-ASA) from new biodegradable polyurethanes.

Segmented polyurethanes containing azo aromatic groups in the main chain were synthesized by reaction of 3,3′-azobis(6-hydroxybenzoic acid) (ABHB), 5-[4-(hydroxyphenyl)azo] salicylic acid (HPAS), and 5-[1-hydroxynaphthyl)azo] salicylic acid (HNAS) with hexamethylenediisocyanate (HDI). All synthesized monomers and polymers were characterized by elemental analysis, FTIR, 1H-NMR spectra, TGA and DSC analysis. All the synthesized azo polymers showed good thermal stability and the onset decomposition temperature of all these polymers was found to be above 195 °C under nitrogen atmosphere. The release of 5-ASA under physiological conditions (pH = 7.8 and pH = 1.5) was investigated at body temperature (37 °C). The release rate of 5-ASA increased with increasing pH (i.e., 7.8 > 1.5).

Biocidal Polymers: Preparation and Antimicrobial Assessment of Immobilized Onium Salts onto Modified Chitosan

New derivatives of chitosan were synthesized by modification of chitosan (CTS) either with chloroacetyl chloride or with bromoacetyl chloride. The haloacetylated chitosan derivatives were quaternized by reaction with triethyl amine and triphenyl phosphine. The quaternized new derivatives of chitosan were tested against Gram-negative bacteria the Gram-positive bacteria Staphylococcus aureus, and the fungi by the cut plug method and viable cell counting methods. The results showed that the new chitosan derivatives have stronger antimicrobial activities than the chitosan itself. The examination of the treated cells by TEM showed complete discharge of cellular cytoplasm which led to the death of the cells.

High temperature microwave-assisted synthesis and the physico-chemical characterisation of mesoporous crystalline titania

Mesoporous TiO2 with nanocrystalline architecture has been synthesised by using microwave-assisted high temperature method using polymeric surfactant. The polymeric template was removed by stepwise carbonisation process. The structural order, band structure and the textural parameters of the calcined mesoporous titania were investigated by using numerous sophisticated techniques such as XRD, nitrogen adsorption, HRSEM, UV-Vis DRS and HRTEM. The obtained mesoporous TiO2 material have mesoscopic order, high surface area, crystalline walls and narrow pore size distribution as evident from the XRD and nitrogen adsorption results. Wide-angle X-ray diffraction pattern obtained for calcined mesoporous TiO2 shows that the pore wall of the sample is composed of highly crystalline Ti-O-Ti framework with an anatase phase. The photoluminescence properties of the mesoporous TiO2 was also analysed and the results were discussed in detail.