Enhanced Antimicrobial Activity of Amine-Phosphonium (N-P) Hybrid Polymers Against Gram-Negative and Gram-Positive Bacteria

The authors report synthesis, characterization and evaluation of a series of linear polyethylenimine (lPEI)-grafted butyltriphenylphosphonium bromide (LBTP) polymers (N-P hybrid polymers) for their antimicrobial activity on various Gram-positive and Gram-negative bacteria. Polymers with ～5.8–13.8% substitution of butyltriphenylphosphonium bromide (BTP) on the backbone of lPEI showed enhanced charge density as compared to native lPEI confirming the conjugation of BTP onto lPEI. These modified polymers displayed low hemolytic activity and excellent antimicrobial activity against these two types of bacteria with one of the modified polymers, LBTP-40, was found to exhibit high antimicrobial activity in all the strains.     

Studies on PVA/AgI-based polymeric membranes for exploration of antibacterial activity

In the present communication, solid polymer electrolyte films have been prepared using solution cast technique based on polyvinyl alcohol (PVA) as host polymer and silver iodide (AgI) as salt. The objective of the study is to develop PVA electrolytic films with AgI and evaluate to protect against simulants of biological warfare agents. The antibacterial activities of the films are explored against Aeromonas hydrophila, Escherichia coli, Salmonella typhii, and Shigella boydii. The antibacterial effects of the PVA/Ag⁺ hybrids were assessed by the minimum inhibitory concentration method. Polymer electrolyte films show good antibacterial activity against A. hydrophilla, S. typhii, and S. boydii. Scanning electron microscopy is used to study the surface morphology of the polymeric membranes. Complex impedance spectroscopy is used for characterizing the electrical and dielectric properties of the electrolyte samples. Frequency-dependent various dielectric properties such as dielectric constant, dielectric loss, and loss tangent have been discussed. The variations of AC conductivity gives the explanation in understanding the mechanism of the ion transport and determine power exponent value n lying in the range 1 and 1.2 which represents the trapping of ions in the polymer matrix.     

Improved cell viability of linear polyethylenimine through gamma-cyclodextrin inclusion for effective gene delivery

A polypseudorotaxane consisting of a linear polyethylenimine with Mn of 22,000 (LPEI22k) and gamma-cyclodextrins (gamma-CDs; LPEI22k/gamma-CD) has been examined as a gene carrier. The polyplex formation with luciferase-encoding plasmid DNA (pDNA), intracellular trafficking of polyplex, cytotoxicity, and transfection efficiency were evaluated by various characteristic methods. LPEI22k/gamma-CD formed a pDNA polyplex at higher N/P ratios than LPEI22k; this suggests that the gamma-CD threading sterically interfered with the polyplex formation. In addition, the zeta potentials of the polyplex significantly decreased due to the reduction in charge density of LPEI22k caused by gamma-CD threading. The cellular uptake of pDNA in the LPEI22k/gamma-CD polyplex was enhanced by free gamma-CDs released from the polyplex that might accelerate the cellular uptake through enhanced membrane affinity. LPEI22k/gamma-CD significantly increased cell viability even at high N/P ratios, and the polyplex showed high transfection efficacy. The low cytotoxicity and high gene expression of LPEI22k/gamma-CD are advantageous to polyplex administration in vivo.     

Plant mediated green synthesis and antibacterial activity of silver nanoparticles using Crataegus douglasii fruit extract

In this study, silver nanoparticles were synthesized using the Crataegus douglasii fruit extract as a reducing agent. The reaction process was monitored by UV–vis spectroscopy. Further characterization was carried out using scanning electron microscopy (SEM). To optimize the biosynthesis of silver nanoparticles, the effect of process variables such as extract concentrations, mixing ratio of the reactants, time and pH were also investigated. The SEM images showed silver nanoparticles with 29.28 nm size and nearly spherical shape at 24 h interaction time. The antibacterial activity of the synthesized silver nanoparticles was confirmed against Staphylococcus aureus and Escherichia coli.     

Enhanced antibacterial activity of anodic aluminum oxide membranes embedded with nano-silver-titanium dioxide

In this work, the fabrication conditions of anodic aluminum oxide (AAO) templates with different pore size diameters were achieved using oxalic, tartaric, and phosphoric acidic electrolytes. Silver (Ag) nanostructures (NSs) were embedded in AAO template by simple hydrothermal and photoreduction methods. Moreover, titanium dioxide (TiO₂) NSs (nanowires) was deposited into these porous templates by sol-gel method. FESEM results suggested that Ag nanofishstars, nanonecklaces (NNs), and TiO₂ nanowires (NWs) like structures were grown in AAO pores with high-order and -aspect ratios. An anti-adhesive method was used to estimate the nano-size effect of the structures for enhancing antibacterial mechanism against Pseudomonas aeruginosa Gram-negative bacterium, and Staphylococcus aureus Gram-positive bacterium. In this study, the inhibition percentages of the Ag NNs/AAO membrane were 86.4, and 77.4%, respectively whereas that of the Ag film on glass substrate were 65, and 53.9%. Moreover, the inhibition percentages of the TiO₂ NWs/AAO membrane were 85.9, and 70.1%, on the other hand, the TiO₂ film on glass substrate were 60.3, and 45.2%. Results proved that the high porosity of the AAO template improved the contact-killing and release-killing actions of nanoparticles against biofilms.     

Deformation zones and entanglements in glassy polymers

Deformation zones are regions of drawn but unfibrillated material which grow from crack tips in thin films of glassy polymers which have a low value of I_e′, the chain contour length between entanglements. The growth of these zones is observed optically and their final structure characterized by transmission electron microscopy. By microdensitometry of the electron image plate the average value of the extension ratio within the deformation zone, λ_DZ, is measured. Such deformation zones have been grown in thin films of four homopolymers and a series of polymer blends. It is found that λ_DZ is approximately 0.6 λ_max, where λ_max is a predicted maximum extension ratio derived from a simple model in which the entanglement points are assumed to act as permanent crosslinks with no chain slippage or scission occurring. This value of λ_DZ is lower than the extension ratios previously measured for crazes grown in the same polymers; typical λ_craze values lie much closer to λ_max. This result can be rationalized by realizing that at least a limited degree of chain scission/slippage must occur during crazing to permit the generation of the void-fibril network. For those polymers where both crazing and deformation zones may form, the latter grow rapidly whereas the formation of crazes requires longer times. This observation also indicates the importance of the kinetic process of chain scission/chain slippage for crazing. Annealing of the polymer films below the glass transition temperature leads to an increased tendency for crazing relative to the growth of deformation zones.     

Soybean protein bodies: Phospholipids and phospholipase D activity

Protein bodies from mature soybeans were isolated by differential centrifugatioin to examine their composition and relationship with phospholipase D. Densities were adjusted by varying mixtures of soybean oil and carbon tetrachloride. The purity of the final isolate was confirmed by electron microscopy. Approximately 4.5% by weight of the protein bodies was lipid and 2.0% by weight phospholipid. Thin-layer chromatography revealed only a trace of phosphatidic acid. Treatment with 60% ethanol/40% sodium acetate buffer (pH 5.6) (vol/vol) resulted in phosphatidyl transferase activity with conversion of both phosphatidylcholine and phosphatidylethanolamine into phosphatidylethanol. It is proposed that protein bodies of soybeans contain phospholipase D. Presented at the Annual Meeting of the American Oil Chemists’ Society, Toronto, Ontario, Canada, May 10–14, 1992.     

Lysozyme-coated silver nanoparticles for differentiating bacterial strains on the basis of antibacterial activity

Lysozyme, an antibacterial enzyme, was used as a stabilizing ligand for the synthesis of fairly uniform silver nanoparticles adopting various strategies. The synthesized particles were characterized using UV-visible spectroscopy, FTIR, dynamic light scattering (DLS), and TEM to observe their morphology and surface chemistry. The silver nanoparticles were evaluated for their antimicrobial activity against several bacterial species and various bacterial strains within the same species. The cationic silver nanoparticles were found to be more effective against Pseudomonas aeruginosa 3 compared to other bacterial species/strains investigated. Some of the bacterial strains of the same species showed variable antibacterial activity. The difference in antimicrobial activity of these particles has led to the conclusion that antimicrobial products formed from silver nanoparticles may not be equally effective against all the bacteria. This difference in the antibacterial activity of silver nanoparticles for different bacterial strains from the same species may be due to the genome islands that are acquired through horizontal gene transfer (HGT). These genome islands are expected to possess some genes that may encode enzymes to resist the antimicrobial activity of silver nanoparticles. These silver nanoparticles may thus also be used to differentiate some bacterial strains within the same species due to variable silver resistance of these variants, which may not possible by simple biochemical tests.     

Hydroquinone Based Sulfonated Copolytriazoles with Enhanced Proton Conductivity

A series of new fluorinated sulfonated copolytriazoles (PTHQSH‐XX) with ion exchange capacity (IEC_w) values ranging from 1.66 to 2.82 meq g⁻¹ are prepared via cuprous ion catalyzed azide‐alkyne click polymerization reaction between 1,4‐bis(prop‐2‐ynyloxy)benzene, 4,4′‐diazido‐2,2′‐stilbene disulfonic acid disodium salt (SA), and 4,4‐bis[3′‐trifluoromethyl‐4′(4‐azidobenzoxy) benzyl] biphenyl (QAZ). The degree of sulfonation of the copolytriazoles is adjusted between 60% and 90% by varying the molar ratio of sulfonated monomer (SA) to the nonsulfonated monomer (QAZ). The structure of the copolytriazoles is characterized by Fourier transform infrared and NMR spectroscopy. The solution‐cast membranes of these copolymers exhibit high thermal, mechanical, oxidative and hydrolytic stability, and high proton conductivity (19–142 mS cm⁻¹ at 80 °C and 22–157 mS cm⁻¹ at 90 °C). Transmission electron microscopy confirms the formation of good phase separated morphology with ionic clusters in the range of 15–145 nm.     

Some electron microscopic observations of sulphonated EPDM polymers

The electron microscopy observations have been conducted with films cast from dilute solution based on sulpho EPDMs derived from various cations. Some very interesting morphological features are observed. Aggregated regions of sizes in the range of 500 to 1000 nm are found in the metal sulphonated polymers, while the absence of structure is observed in the base polymer and its acid derivative. This type of morphology has not been previously reported, and these aggregates appear about 100 times larger than typically expected for phase separated ionomers. Possible explanations of these morphologies are discussed.     

Enhanced antibacterial activity,antioxidant, and in vitro biocompatibility of modified polycaprolactone-based membranes

The fabrication, surface functionality, and biocompatibility of membranes prepared from blends of polycaprolactone (PCL) and curcumin powder (CURP) (PCL/CURP) were studied. Acrylic acid (AA)-grafted polycaprolactone (PCL-g-AA) was evaluated as an alternative to PCL. Mouse tail-skin fibroblasts (FBs) were seeded on two series of these films to assess cytocompatibility. Collagen and cell proliferation analyses indicated that PCL, PCL-g-AA, and their composite membranes were biocompatible with respect to FB proliferation. However, FB proliferation, collagen production and the percentage of normal cells growing on PCL/CURP membranes were greater than those for PCL-g-AA/CURP membranes. Rapid apoptosis was not observed with assays of FBs on the PCL-series membranes, demonstrating the potential of PCL/CURP or PCL-g-AA/CURP membranes for biomedical applications. Moreover, CURP enhanced the Escherichia coli (BCRC 10239) antibacterial activity and antioxidant properties of the membranes. Membranes of PCL-g-AA or PCL containing CURP had better antibacterial and antioxidant activity.     

Biomolecular Characterization of Diazotrophs Isolated from the Tropical Soil in Malaysia

This study was conducted to evaluate selected biomolecular characteristics of rice root-associated diazotrophs isolated from the Tanjong Karang rice irrigation project area of Malaysia. Soil and rice plant samples were collected from seven soil series belonging to order Inceptisol (USDA soil taxonomy). A total of 38 diazotrophs were isolated using a nitrogen-free medium. The biochemical properties of the isolated bacteria, such as nitrogenase activity, indoleacetic acid (IAA) production and sugar utilization, were measured. According to a cluster analysis of Jaccard’s similarity coefficients, the genetic similarities among the isolated diazotrophs ranged from 10% to 100%. A dendogram constructed using the unweighted pair-group method with arithmetic mean (UPGMA) showed that the isolated diazotrophs clustered into 12 groups. The genomic DNA rep-PCR data were subjected to a principal component analysis, and the first four principal components (PC) accounted for 52.46% of the total variation among the 38 diazotrophs. The 10 diazotrophs that tested highly positive in the acetylene reduction assay (ARA) were identified as Bacillus spp. (9 diazotrophs) and Burkholderia sp. (Sb16) using the partial 16S rRNA gene sequence analysis. In the analysis of the biochemical characteristics, three principal components were accounted for approximately 85% of the total variation among the identified diazotrophs. The examination of root colonization using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) proved that two of the isolated diazotrophs (Sb16 and Sb26) were able to colonize the surface and interior of rice roots and fixed 22%–24% of the total tissue nitrogen from the atmosphere. In general, the tropical soils (Inceptisols) of the Tanjong Karang rice irrigation project area in Malaysia harbor a diverse group of diazotrophs that exhibit a large variation of biomolecular characteristics.     

Transmission electron microscopy of milkfat globules in the low-density lipid fraction of swiss cheese whey

A low-density lipid fraction (LDLF) was recovered from Swiss cheese whey (SCW) residual lipids by high-speed centrifugation. The present study was conducted to determine the microstructural properties of the extremely small-sized milkfat globules (MFG) in LDLF by: (i) freeze-fracture transmission electron microscopy (FF-TEM) and (ii) thin-section TEM (TS-TEM). FF-TEM results revealed that MFG in LDLF were ≤1 μm in size and were embedded in what appeared to be a smooth, protein-like matrix. The MFG in FF-TEM specimens exhibited either planarly cleaved fractions with smooth cores or peripherally cleaved fractions with surface laminations. TS-TEM results revealed that the MFG in LDLF were dispersed in an aggregated nonlipid matrix.     

Biosynthesis of silver nanoparticles from the culture supernatant of Bacillus marisflavi and their potential antibacterial activity

Silver nanoparticles (AgNPs) were prepared using culture supernatant of Bacillus marisflavi, a novel strain isolated from agricultural wastes. The formation of the AgNPs was confirmed using various analytical techniques such as UV–vis absorption spectroscopy, dynamic light scattering (DLS) and transmission electron microscopy (TEM). The antibacterial effect of synthesized nanoparticles was investigated against Pseudomonas aeruginosa. Furthermore, the mechanism of action of cell death of P. aeruginosa was confirmed by reactive oxygen species (ROS) generation in AgNPs treated cells and also our results clearly indicate that AgNPs could induce generation of ROS by dose dependent manner.     

Improving the antibacterial activity of cotton fabrics finished with triclosan by the use of 1,2,3,4‐butanetetracarboxylic acid and citric acid

For producing antibacterial textiles, the conventional finishing processes have high productivity and low processing costs, but textiles finished in these ways exhibit low durability against laundering. Therefore, cotton fabrics were bleached with hydrogen peroxide, finished with triclosan, and then treated with polycarboxylic acids such as 1,2,3,4‐butanetetracarboxylic acid (BTCA) and citric acid (CA) as crosslinking agents to provide durable antibacterial properties. The surface of fibers treated with BTCA had a greater crosslinked area, and the surfaces of fabrics treated with CA were exposed to greater amounts of deformation due to the mechanical and chemical influences after 50 launderings. The bleaching and finishing treatments did not dramatically affect the breaking strength. However, the polycarboxylic acid treatment (both BTCA and CA) alone showed reductions in the breaking strength when the acid concentration was increased. The polycarboxylic acids were fairly effective against both bacteria, even at lower concentrations, when they were applied to stand‐alone cotton fabrics, whereas the antibacterial activity decreased somewhat after the use of polycarboxylic acid and triclosan in the same recipes. Adding polycarboxylic acids to the antibacterial finishing recipes enhanced the durability after 50 launderings, and the durability of the recipes containing BTCA was much higher than that of the recipes containing CA. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Microstructural Characterization of a Commercial Hot‐Pressed Boron Carbide Armor Plate

Detailed microstructural characterization was carried out on a commercial‐grade hot‐pressed boron carbide armor plate. The boron carbide grains have close to B₄C stoichiometry, and most of them have no planar defects. The most prominent second phase is intergranular graphite inclusions that are surrounded by multiple boron carbide grains. Submicrometer intragranular and intergranular BN and AlN precipitates were also observed. In addition, fine dispersions of AlN nanoprecipitates were observed in some but not all grains. No intergranular films were found. These microstructural characteristics are compared with the lab‐consolidated boron carbide and their effects on the mechanical properties of boron carbide are addressed.     

Relaxation time spectra of linear and crosslinked polymers

In this work, an attempt has been made to define a unique relaxation time spectrum for different types of polymeric materials. Empirical models for the relaxation spectrum, proposed for linear flexible polymers in the literature, have been used. A systematic determination of the parameters defining the relaxation time spectrum has been made from dynamic mechanical data. It has been shown that the resulted expression for the relaxation modulus could then be used to calculate the stress response of the materials to various deformations. The strain rate dependence of yield behavior could also be predicted. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 679–684, 1998     

Kinetics and equilibrium of cobalt ion adsorption on cross‐linked polyethylenimine membrane

The kinetics and equilibrium of cobalt ion adsorption on crosslinked polyethylenimine (PEI) membrane were studied by the spectroscopic method in terms of time, cobalt ion concentration, and temperature. It was found that the adsorption of cobalt ion on crosslinked PEI membrane obeyed the pseudofirst‐order kinetic model and the equilibrium adsorption amount of cobalt ion on crosslinked PEI membrane was closely related to the initial cobalt ion concentration. The equilibrium adsorption amount increased with the decrease of temperature and obeyed a Langmuir isotherm to give the equilibrium constant for the adsorption of cobalt ion on crosslinked PEI membrane under various temperatures. Based on Van't Hoff equation the enthalpy and entropy of the adsorption of cobalt ion on crosslinked PEI membrane were determined to be ?12.9 kJ mol^?1 and ?107 J mol^?1 K^?1, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Kinetics of ethylene oxidation on plane Pt/SiO2 catalysts in the viscous pressure regime: evidence of support activity

C₂H₄ oxidation on plane Pt/SiO₂ model catalysts with various Pt loadings was studied atT = 373–473 K and in the pressure ranges 10^–6–10² Torr C₂H₄ and 0.3–1500 Torr 02 (1 Torr = 133.3 Pa). Mass spectrometry combined with spatially resolved gas sampling enabled kinetic data to be collected far into the viscous pressure regime. Reaction orders and activation energies were similar to those of a macroscopic Pt surface. However, under fuel-lean conditions the global reaction rate decreases faster than the decrease in metal area. On the other hand, the global rate wasindependent of Pt loading and metal surface area in fuel-rich gas mixtures. This is interpreted in terms of a spillover effect.     

Preparation and the antioxidant and antibacterial activities of urushiol powders (YPUOH)

Lacquer sap derived from lacquer trees has been widely used in Asian countries for thousands of years as a natural paint and coating material. These natural lacquers exhibit superior barrier properties against oxygen and water, as well as good durability, chemical resistance, mechanical properties, and antibacterial and antioxidant properties. However, they are limited in commercial application due to their high volatility, low drying rate, and allergic reactions. To overcome these limitations, powder-type urushiols (YPUOH), which are essential to provide convenient handling, were successfully prepared using urushiol and different contents of 3-(trimethoxysilyl) propyl methacrylate (TPM). The prepared YPUOH powders were analyzed by Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), thermogravimetric analyzer (TGA), and antibacterial and antioxidant measurements. The as-prepared YPUOH powders exhibited excellent antibacterial activity against E. coli and S. aureus, good antioxidant activity, and high thermal stability.