Corn starch of different physical forms (solid and liquid) was irradiated with 60Co gamma rays and electron beam in the dose range of 50 Gy to 100 kGy to investigate the effect of ionizing radiation on its molecular weight (Mw). Degradation was observed for both solid and liquid states upon radiation. However, degradation of the starch in the liquid state was remarkably greater than that in the solid state. The free radicals that formed during water irradiation must be responsible for such degradation in the liquid form. Thermostated viscometer, rheometer and multi‐angle static laser light scattering were employed to study the changes in the Mw of corn starch that occurred during irradiation at constant temperature and different concentrations. It was observed that electron beam irradiated corn starch has uniform decreasing in Mw and radius of gyration (Rg) in the range of (4.4×107–2.9×107 g mol?1) and (199.3–85.6 nm), respectively. The influence of gas atmosphere on the degradation process during gamma irradiation was studied to find that, the Mw and Rg values were in the range of (4.4×107–1.8×107 g mol?1) and (199.3–120.4 nm) for the oxygen saturated samples, while, they were (4.4×107–1.05×107 g mol?1) and (199.3–85.6 nm) for the argon saturated samples.

Amylose readily dissolves in hot water, unlike amylopectin which is largely insoluble. However, size distributions of amylose isolated in such a manner often show the presence of hyper-branched material consistent with amylopectin. The difference in solubility suggests that the hot-water-soluble (HWS) hyper-branched material might be structurally distinct from typical amylopectin. In the present paper, the structural properties of the two solubility fractions of hyper-branched material are explored in a set of traditional waxy rice varieties. The objective was to elucidate the nature of the HWS component, e.g. to see if it could be phytoglycogen, another water-soluble polysaccharide. We show that solubility is controlled by thermodynamic effects, rather than slow dissolution (kinetic effects). The average size, degree of branching and the debranched chain-length distributions indicate that the HWS fraction is structurally different from phytoglycogen. The debranched chain-length distributions of short chains and the degrees of branching in the HWS material are similar to those of the hot-water-insoluble (HWI) fractions but the chain-length distributions indicate that the HWI fractions carry longer chains than those in the HWS fractions. Light-scattering measurements show that the average size of whole molecules in the HWI component is significantly greater than in the HWS component. It is postulated that the structural differences limit solubility of the molecules in the HWI fraction, possibly due to co-crystallisation with adjacent molecules at more points than is possible for the shorter chains in HWS molecules.

A new instrument, based on the principle of phase analysis light scattering (PALS) for the measurement of electrophoretic mobilities, has been produced. Such measurements are particularly useful in the study of dispersions in nonpolar and highly conducting media. The current PALS configuration can be used to measure mobilities up to 3 orders of magnitude lower than with the conventional Doppler mode. The device has a number of new features; in particular, all the signal processing is digital and the optical system features a reference beam configuration. Data are presented to show that on suitable samples both the PALS technique and conventional laser Doppler electrophoresis can be performed on the same instrument and the techniques are in good agreement

The points of zero charge (PZC) and isoelectric points (IEP) from the recent literature are discussed. This study is an update of the previous compilation [M. Kosmulski, Surface Charging and Points of Zero Charge, CRC, Boca Raton, FL, 2009] and of its previous update [J. Colloid Interface Sci. 337 (2009) 439]. In several recent publications, the terms PZC/IEP have been used outside their usual meaning. Only the PZC/IEP obtained according to the methods recommended by the present author are reported in this paper, and the other results are ignored. PZC/IEP of albite, sepiolite, and sericite, which have not been studied before, became available over the past 2 years.

Here we characterize the structure, stability and intracellular mode of action of DermaVir nanomedicine that is under clinical development for the treatment of HIV/AIDS. This nanomedicine comprises pathogen-like pDNA/PEIm nanoparticles (NPs) having the structure and function resembling spherical viruses that naturally evolved to deliver nucleic acids to the cells. Atomic force microscopy demonstrated spherical 100 – 200 nm NPs with a smooth polymer surface protecting the pDNA in the core. Optical absorption determined both the NP structural stability and biological activity relevant to their ability to escape from the endosome and release the pDNA at the nucleus. Salt, pH and temperature influence nanomedicine shelf-life and intracellular stability. This approach facilitates the development of diverse polyplex nanomedicines where the delivered pDNA-expressed antigens induce immune responses to kill infected cells.

The transport of stabilized zerovalent iron nanoparticles (nZVI) has recently been the topic of extensive research due to its proven potential as an in situ remediation tool. However, these studies have ignored the effects of biofilms—complex aggregations of bacterial cells and excreted extracellular polymeric substances present in nearly all aquatic systems—on the transport of these particles. This study examines the effects of Pseudomonas aeruginosa (PAO1) biofilm, at a cell concentration similar to that reported for saturated aquifers, on the transport of commercially available, poly (acrylic acid) stabilized nZVI (pnZVI) in 14 cm long columns packed with saturated glass beads at salt concentrations of 1 and 25 mM NaCl. Compared to retention on uncoated columns, in the presence of biofilm the retention of pnZVI increased at higher ionic strength, while ionic strength played no role in retention of these nanoparticles in the absence of biofilm. The Tufenkji–Elimelech correlation equation predicts lower retention of pnZVI on biofilm coated columns compared to uncoated columns due to a lower Hamaker constant, and DLVO energy considerations predict the most favorable attachment to uncoated porous media at higher ionic strength. A steric (polymer-mediated) model that considers the combined influence of steric effects of polymers and DLVO interactions is shown to adequately describe particle retention in columns.

There is a pressing need for information on the mobility of nanoparticles in the complex aqueous matrices found in realistic environmental conditions. We dispersed three different metal oxide nanoparticles (TiO2, ZnO and CeO2) in samples taken from eight different aqueous media associated with seawater, lagoon, river, and groundwater, and measured their electrophoretic mobility, state of aggregation, and rate of sedimentation. The electrophoretic mobility of the particles in a given aqueous media was dominated by the presence of natural organic matter (NOM) and ionic strength, and independent of pH. NOM adsorbed onto these nanoparticles significantly reduces their aggregation, stabilizing them under many conditions. The transition from reaction to diffusion limited aggregation occurs at an electrophoretic mobility from around ?2 to ?0.8 μm s?1 V?1 cm. These results are key for designing and interpreting nanoparticle ecotoxicity studies in various environmental conditions.

Structure and biological activity of pathogen-like synthetic nanomedicines

Stability and Aggregation of Metal Oxide Nanoparticles in Natural Aqueous Matrices

美国布鲁克海文仪器公司 Mobility measurements by phase analysis.

Bacterial quorum sensing and cell surface electrokinetic properties

There is current interest in developing new synthesis strategies for multifunctional hollow spheres with tunable structural properties that would be useful in encapsulation and controlled release applications. A new route was reported recently, in which the sequential reaction of polyamines, multivalent anions, and charged nanoparticles leads to the formation of polymer-filled and water-filled organic/inorganic micron-sized structures known as nanoparticle-assembled capsules. This technique is unique among other capsule preparation routes, as it allows the rapid and scalable formation of robust shells at room temperature, in near-neutral water, and with readily available precursors. This nanoparticle assembly synthesis route involves two steps:? the formation of polymer aggregates and the subsequent deposition of particles around the aggregates. The purpose of this paper is to understand in greater detail the noncovalent chemistry of the polymer?salt aggregation step. With poly(allylamine hydrochloride) (PAH) as the model polymer, aggregate formation was investigated as a function of charge ratio, pH, and time through dynamic light scattering, electrophoretic mobility measurements, chloride ion measurements, and optical microscopy. PAH formed aggregates by the cross-linking action of divalent and higher-valent anions above a critical charge ratio and in a pH range defined by the pKa values of PAH and the anion. The aggregates grew in size through coalescence and with growth rates that depended on their surface charge. Controlling polymer aggregate growth provided a direct and simple means to adjust the size of the resultant capsule materials.

The hypothesis tested in this paper is that quorum sensing influences the microbial surface electrokinetic properties. Escherichia coli MG1655 and MG1655 LuxS- mutant (lacking quorum-sensing gene for Autoinducer synthase AI-2) were used for this study. AI-2 production (or lack of) in both strains was analyzed using the Vibrio harveyi bioassay. The levels of extracellular AI-2 with and without glucose in the growth medium were consistent with previously published work. The surface electrokinetic properties were determined for each strain of E. coli MG1655 by measuring the electrophoretic mobility using a phase amplitude light-scattering (PALS) Zeta potential analyser. The findings show that the surface charge of the cells is dependent upon the stage in the growth phase as well as the ability to participate in quorum sensing. In addition, significant differences in the electrophoretic mobility were observed between both strains of E. coli. These findings suggest that quorum sensing plays a significant role in the surface chemistry of bacteria during their growth.

Chitosan and its various neutral pH water-soluble derivatives were investigated for dispersing single-walled carbon nanotubes (SWNTs). Chitosan (CS) can produce good dispersion of SWNTs, but only in acidic pH condition. Our two novel derivatives, O-carboxymethylchitosan (OC) and OC modified by poly(ethylene glycol) at the ?COOH position (OPEG), were able to produce highly effective debundling and dispersion of SWNTs in neutral pH aqueous solution. Atomic force microscopy (AFM), transmission electron microscopy (TEM), photoluminescence, UV?vis?NIR spetroscopy, and Raman spectroscopy confirmed that SWNTs are present as individual nanotubes in the dispersions. The solubilities of individually dispersed SWNTs in neutral water are 0.021 and 0.032 g/L for OC and OPEG, respectively, which are comparable to 0.038 g/L for SWNTs using CS in acetic acid. Further, OC and OPEG aqueous solutions (1 wt %) do not significantly lower the surface tensions (65?67 mN/m). From the Fourier transform infrared spectroscopic results, we conclude that the free electron pair in the pendant amine groups of OC and OPEG plays a vital role in finely dispersing the SWNTs; the ?NH2 contributes to the adsorption of these two chitosan derivatives on the nanotubes. Quaternary ammonium chitosan (QC), with alkyl substitution at the protonated amine, was found to be unable to disperse SWNTs; possibly cation?π interaction with nanotubes is diminished due to steric hindrance.

Tin oxide nanoparticles can be assembled into micron-sized hollow capsule structures through a simple mixing procedure based on charge-mediated polymer aggregate templating.

Chemical conjugation of targeting ligands to polycation/plasmid DNA complexes has been widely used to improve the transfection efficiency of nonviral gene delivery vectors. However, conjugation reactions may reduce or even inactivate the biological activities of chemically sensitive moieties, such as proteins and peptides. Here we describe a new method for introducing targeting ligands into nonviral vectors, in which ternary complexes are formed via charge interactions among polyethylenimine (PEI) of 600 Da, plasmid DNA and targeting peptides with positively charged DNA-binding sequence. Owing to the nerve growth factor (NGF) loop 4 hairpin motif in the targeting peptide, these ternary complexes are capable of mediating gene delivery efficiently and specifically into cells expressing the NGF receptor TrkA. In in vitro experiments, the complexes improved luciferase reporter gene expression by up to 1000-fold while comparing with that produced by complexes with nontargeting control peptide. In an in vivo experiment, the ternary complexes with the targeting peptide was 59-fold more efficient than the control ternary complexes in transfecting dorsal root ganglia (DRG), the peripheral nervous sites with TrkA-expressing neurons. In a cell viability study, the ternary complexes were remarkably different from DNA complexes by PEI of 25 kDa, the gold standard for nonviral gene carriers, displaying no toxicity in tested neuronal cells. Thus, this study demonstrates an alternative method to construct nonviral delivery system for targeted gene transfer into neurons.

In the present study, the competitive adsorption characteristics of binary and ternary heavy metal ions Pb2+, Cu2+, and Cd2+ on microporous titanosilicate ETS-10 were investigated in batch systems. Pure microporous titanosilicate ETS-10 was synthesized with P25 as the Ti source and characterized by the techniques of X-ray diffraction (XRD), field emission-scanning electron microscope (FESEM), nitrogen adsorption, and ζ-potential. Equilibrium and kinetic adsorption data showed that ETS-10 displays a high selectivity toward one metal in a two-component or a three-component system with an affinity order of Pb2+ > Cd2+ > Cu2+. The equilibrium behaviors of heavy metals species with stronger affinity toward ETS-10 can be described by the Langmuir equation while the adsorption kinetics of the metals can be well fitted to a pseudo-second-order (PSO) model.

Phospholipid-coated colloidal magnetic nanoparticles with mean magnetite core size of 8 nm are shown to be effective ion exchange media for the recovery and separation of proteins from protein mixtures. These particles have high adsorptive capacities (up to 1200 mg protein/mL adsorbent, an order of magnitude larger than the best commercially available adsorbents) and exhibit none of the diffusional resistances offered by conventional porous ion exchange media. Protein-laden particles are readily recovered from the feed solution using high-gradient magnetic filtration.

Surface topography is one of the most important factors influencing the attachment and spreading of cells. In the present study, layer-by-layer assembled titanium dioxide (TiO2) nanoparticle thin films were chosen for attachment, proliferation and spreading studies on mouse mesenchymal stem cells (MSC). Increasing surface roughness was observed with increasing number of layer-by-layer assembled TiO2 thin films. Four layer TiO2 thin film showed higher number of attached cells than a one layer thin film and control surfaces. MSCs experienced no cytotoxic effects after culture on the TiO2 coated substrates as observed from the cytotoxicity tests. Cell spreading, visualized with scanning electron microscopy, showed a faster rate of spreading on a rougher surface. Cells on a four-layer substrate, at 12 h showed complete spreading, where as most of the cells on a control surface and a one-layer surface, at 24 h, retained a rounded morphology. In conclusion, TiO2 nanoparticle thin films were successfully assembled in alternation with polyelectrolytes and in-vitro studies with MSC showed an increase in the attachment and faster spreading of cells on rougher surfaces.

Titanate nanotube films are fabricated on F-doped SnO2-coated glass substrates via an electrophoretic deposition method using hydrothermally prepared titanate nanotubes as precursors. The effects of calcination temperature on the microstructures and photoactivity of as-prepared titanate nanotube films are investigated and discussed. The results indicate that the intercalated sodium ions (Na+) in the as-prepared titanate nanotubes are easily removed during the electrophoretic deposition. The phase transformation of titanate to anatase and diffusion of Na+ ions from glass substrates into films occur at 400?°C. With increasing calcination temperature, the crystallization of anatase enhances and sodium content in the films increases. At 500?°C, the tubular structure still holds and the films show the highest photocatalytic activity probably due to their good crystallization, large specific surface areas and tubular structures.

The temperature stability of aqueous dispersions of hydrophobic monodisperse silica particles stabilized with nonionic surfactants has been investigated. Adsorption isotherms in conjunction with surface tension measurements showed that the surfactant formed a monolayer on the surface of the particles, where the adsorbed amount depended on the molecular weight of the ethylene oxide headgroup. The temperature stability of these dispersions has been measured by a standard turbidimetric technique and visual observations in terms of their critical flocculation temperature (CFT). Parameters controlling the CFT of the individual dispersions stabilized with a monolayer of surfactant include the thickness of the steric layer, the particle size, and the volume fraction of the particles. Calculations show that the van der Waals attraction between the particles with adsorbed polymer layers increases as the temperature of the dispersion increases, and this largely accounts for the observed CFT behavior.

The surface properties of carbon nanotubes have been changed by heat treatment with ammonia to yield a basic surface or with N2 to yield an acidic surface without destroying the integrity of the nanotubes. The dispersion state of CNTs could be much improved by the adsorption of a cationic dispersant of poly(ethylenimine) (PEI) or an ionic dispersant of sodium dodecyl sulfate (SDS). Through the electrostatic interaction between components, CNTs could be successfully coated with particles of titania or alumina by colloidal heterocoagulation. A titania coating on 1.5wt% CNTs, shows the same photocatalytic properties in phenol degradation and has advantages in separation and reuse.

文献名： Thermal and osmotic deswelling of poly(NIPAM) microgel particles 作者： Brian R. Saunders and Brian Vincent 摘要： The effects of temperature and added free polymer on the swelling of poly(NIPAM)(NIPAM =N-isopropylacrylamide) microgel particles cross-linked with N,N′-methylene bisacrylamide have been investigated. The microgel particles were characterized by photocorrelation spectroscopy (PCS), TEM and SEM measurements. Particle sizes determined by TEM were invariably larger than those measured at 50 °C by PCS. SEM data suggest that dried particles have an oblate spheroid shape. The rate at which poly(NIPAM) particles collapse and swell in response to cycling of the temperature between 28 and 60 °C was examined and some hysteresis was observed. Excluded free polymer [PEG, where PEG = poly(ethyleneglycol)] also caused deswelling of the poly(NIPAM) particles at 25 °C due to osmotic pressure effects. Osmotic deswelling occurred in the presence of monodisperse PEG when the molecular weight of the latter was 1470 g mol–1. Higher molecular weight PEG polymers caused a general decrease in the extent of deswelling (at a fixed concentration of PEG).

文献名： Adsorption of bovine serum albumin on nanosized magnetic particles 作者： Z.G. Peng, K. Hidajat, M.S. Uddin Department of Chemical and Environmental Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260 摘要： Adsorption of bovine serum albumin (BSA) on nanosized magnetic particles (Fe3O4) was carried out in the presence of carbodiimide. The equilibrium and kinetics of the adsorption process were studied. Nanosized magnetic particles (Fe3O4) were prepared by the chemical precipitation method using Fe2+, Fe3+ salts, and ammonium hydroxide under a nitrogen atmosphere. Characterizations of magnetic particles were carried out using transmission electron microscopy (TEM) and a vibrating sample magnetometer (VSM). Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to confirm the attachment of BSA on magnetic particles. Effects of pH and salt concentrations were investigated on the adsorption process. The experimental results show that the adsorption of BSA on magnetic particles was affected greatly by the pH, while the effect of salt concentrations was insignificant at a low concentration range. The adsorption equilibrium isotherm was fitted well by the Langmuir model. The maximum adsorption of BSA on magnetic particles occurred at the isoelectric point of BSA. Adsorption kinetics was analyzed by a linear driving force mass-transfer model. BSA was desorbed from magnetic particles under alkaline conditions, which was confirmed by SDS–PAGE electrophoresis and FTIR results. 关键词： Nanosized magnetic particles; Bovine serum albumin; Zeta potential; Adsorption; Desorption

文献名： Room temperature synthesis of rutile nanorods and their applications on cloth 作者： Bin Fei1,5, Zhaoxiang Deng2, John H Xin1,5, Yihe Zhang1,3 and Geoffrey Pang4 1 Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hong Kong 2 Department of Chemistry, University of Science and Technology of China, Hefei, People's Republic of China 3 Department of Materials Science and Technology, China University of Geosciences, Beijing, People's Republic of China 4 Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong 5 Authors to whom any correspondence should be addressed 摘要： In order to achieve better photocatalytic performance, rutile nanorods dispersed in anatase and brookite phases were synthesized from titanium isopropoxide (TIP) in a concentrated HNO3 solution at room temperature (23?°C). X-ray diffraction results indicated that the percentage of rutile increased with increasing peptization time. Scanning electron microscopy and and high-resolution transmission electron microscopy measurements revealed that the nanosized titania particles mainly consisted of granular anatase and brookite, and rod-like rutile. It was interesting that the stability of the colloid increased with increasing nanoparticle concentration, and the tricrystalline titania showed a photocatalytic activity higher than that of pure anatase. These nanocrystals were applied onto cotton fabrics, and achieved a promising bactericidal photocatalytic activity and excellent protection against UV radiation.

文献名： Attachment of Escherichia coli O157:H7 grown in tryptic soy broth and nutrient broth to apple and lettuce surfaces as related to cell hydrophobicity, surface charge, and capsule production 作者： A.N. Hassan, J.F. Frank Center for Food Safety, Department of Food Science and Technology, The University of Georgia, Athens, GA 30602-7610, USA 摘要： This study investigated the effect of growth in tryptic soy broth (TSB) and nutrient broth (NB) on the ability Escherichia coli O157:H7 to attach to lettuce and apple surfaces. In addition, cell surface hydrophobicity, charge and capsule production were determined on cells grown in these media. Cells grown in NB attached less to lettuce and apple surfaces than did those grown in TSB. TSB, but not NB, supported capsule production by E. coli O157:H7. Cells grown in TSB were more hydrophilic than those grown in NB. No difference was found in the electrokinetic properties of cells grown in these media. Electrostatic and hydrophobic interactions and surface proteins did not appear to play an important role in the attachment of E. coli O157:H7 to these surfaces. Of the factors studied, only capsule production was associated with attachment ability. 关键词： Lettuce; Apple; Escherichia coli O157:H7; Attachment; Capsules

Adsorption and desorption behavior of Bovine Serum Albumin (BSA) on surface-modified magnetic nanoparticles covered with thermosensitive polymer (PNIPAM) was investigated as a function of temperature, pH, and ionic strength. Functionalization of surface-modified magnetic particles was performed by seed polymerization using N-isopropylacrylamide (PNIPAM) as the main monomer. Characterization of these particles was carried out using transmission electron micrography (TEM), and vibrating sample magnetometry (VSM). The adsorption results exhibited both pH and temperature sensitivity. The results showed that the temperature effect on adsorption/desorption behavior was mainly dependent on the properties of the particles’ surface. The effect of pH was also investigated and it was observed that a smaller amount of protein was adsorbed at higher pH because of the electrostatic repulsive force between protein molecules and latex particles. The maximum amount of protein was adsorbed near the isoelectric point of BSA. Desorption results showed that more protein was desorbed when adsorption was done at lower temperatures and desorption efficiency was found to be higher than 80%.

It has been shown that the swelling of poly-N-isopropyl-acrylamide (poly-NIPAM) microgel particles can be controlled by the addition of alcohols, in addition to the previously observed effect of temperature. The degree of swelling is also controlled by the amount of cross-linker within the microgel particles. At 25?°C, poly-NIPAM microgel particles collapse upon the addition of MeOH, EtOH and 2-PrOH to a minimum size and then, reswell again as the alcohol-rich region is approached. This trend was also observed for poly-NIPAM microgel particles dispersed in 2-PrOH/water mixtures upon heating to 50?°C. The particles, dispersed in either water or alcohol/water mixtures were found to be stable to flocculation between 25?°C and 50?°C.

The points of zero charge (PZC) and isoelectric points (IEP) from the recent literature are discussed. This study is an update of the previous compilation [M. Kosmulski, Surface Charging and Points of Zero Charge, CRC, Boca Raton, FL, 2009] and of its previous update [J. Colloid Interface Sci. 337 (2009) 439]. In several recent publications, the terms PZC/IEP have been used outside their usual meaning. Only the PZC/IEP obtained according to the methods recommended by the present author are reported in this paper, and the other results are ignored. PZC/IEP of albite, sepiolite, and sericite, which have not been studied before, became available over the past 2 years.

Exosomes are naturally occurring biological nanovesicles utilized by tumors to communicate signals to local and remote cells and tissues. Melanoma exosomes can incite a proangiogenic signaling program capable of remodeling tissue matrices. In this study, we show exosome-mediated conditioning of lymph nodes and define microanatomic responses that license metastasis of melanoma cells. Homing of melanoma exosomes to sentinel lymph nodes imposes synchronized molecular signals that effect melanoma cell recruitment, extracellular matrix deposition, and vascular proliferation in the lymph nodes. Our findings highlight the pathophysiologic role and mechanisms of an exosome-mediated process of microanatomic niche preparation that facilitates lymphatic metastasis by cancer cells.