G. Poletti

Surface modification of poly(ethylene terephthalate) fibers induced by radio frequency air plasma treatment

The surface chemical and physical modifications of poly(ethylene terephthalate) (PET) fibers induced by radiofrequency air plasma treatments were correlated with the characteristics of the discharge parameters and the chemical composition of the plasma itself, to identify the plasma-induced surface processes prevailing under different operating conditions. Treated polymer surfaces were characterized by water droplet absorption time measurements and XPS analysis, as a function of the aging time in different media, and by AFM analysis. They exhibited a remarkable increase in hydrophilicity, accompanied by extensive etching and by the implantation of both oxygen- and nitrogen-containing polar groups. Etching was mainly a consequence of ion bombardment, yielding low molecular weight, water soluble oxidation products, while surface chemical modifications were mainly due to the action of neutral species on the plasma-activated polymer surface.

Cold plasma treatment of PET fabrics: AFM surface morphology characterisation

Atomic force microscopy (AFM) has been used to investigate the morphology changes in the surface of poly(ethyleneterephthalate) (PET) fabrics due to cold plasma treatments. This has resulted in the possibility to measure quantitatively the root-mean-square (rms) surface roughness and the surface area of the samples developed after the treatment. The morphology changes, mainly rms surface roughness and surface area, on the PET fabrics surface due to air cold plasma have been measured as a function of treatment time and as a function of gas pressure. The same quantities as a function of pressure were measured also for He, Ar, SF6 and CF4 gases. The changes in morphology in the cases of air, He and Ar gases seems to be due mainly to etching effects. The situation is different for SF6 and CF4 gases where reorganisation of the surface, possibly due to fluorine atoms grafting, seems to be effective.

Cyano-bridged coordination polymer nanoparticles with high nuclear relaxivity: toward new contrast agents for MRI.

New water-soluble paramagnetic Gd-containing cyano-bridged metallic coordination polymer nanoparticles with a chitosan shell show high nuclear relaxivity in acidic water which is up to six times higher than that of the actually used Gd-chelates.

A comparative study between AFM and SEM imaging on human scalp hair

A comparative study of AFM and SEM imaging of the same area of a human scalp hair has been carried out to determine the similarity and the differences between the two techniques. Sample preparation for SEM analysis requires a metallization step and vacuum exposure, both of which could potentially induce modifications to the surface details. By contrast, AFM is a suitable technique to evaluate any effect resulting from sample manipulation because it can be applied without any specific treatment. AFM analysis demonstrates that sample metallization is responsible for modifications to the surface details of hair, mainly comprising an increase in height of scale steps and of root mean square roughness together with variation in scale profiles. Sample treatments for SEM imaging are in general potentially responsible for surface modifications to the samples involved.

Characterization of plasma processing for polymers

Abstract Some selective plasma treatments are described, aiming at modifying specific surface properties of textile polymeric materials, such as their hydrorepellence and dyeability. The prevailing plasma–polymer interactions were identified by correlating the physico-chemical modification of treated polymer surfaces to the characteristics of the plasma sources.

Atomic force microscopy imaging of actin cortical cytoskeleton of Xenopus laevis oocyte

In this study we report an atomic force microscopy (AFM) investigation of the actin cortical cytoskeleton of Xenopus laevis oocytes. Samples consisted of inside‐out orientated plasma membrane patches of X. laevis oocytes with overhanging cytoplasmic material. They were spread on a freshly cleaved mica surface, subsequently treated with Triton X‐100 detergent and chemically fixed. The presence of actin fibres in oocyte patches was proved by fluorescence microscopy imaging. Contact mode AFM imaging was performed in air in constant force conditions. Reproducible high‐resolution AFM images of a filamentous structure were obtained. The filamentous structure was identified as an actin cortical cytoskeleton, investigating its disaggregation induced by cytochalasin D treatment. The thinnest fibres showed a height of 7 nm in accordance with the diameter of a single actin microfilament. The results suggest that AFM imaging can be used for the high‐resolution study of the actin cortical cytoskeleton of the X. laevis oocyte and its modifications mediated by the action of drugs and toxins.

Comparison between gamma and beta irradiation effects on hydroxypropylmethylcellulose and gelatin hard capsules.

The effects of electron beam or λ-irradiation on technological performances (capsule hardness, expressed as deforming work and dissolution time) of empty 2-shell capsules made of gelatin or hydroxypropylmethylcellulose (HPMC) were studied. Capsule structural changes induced by radiation treatment were investigated by capillary viscometry and atomic force microscopy (AFM). The capsules were irradiated in the air at 5, 15, and 25 kGy. The deforming work of nonirradiated HPMC capsules (0.06±0.01 J) was lower than that of gelatin capsules (0.10±0.01 J). The dissolution time of the HPMC capsules (414±33 seconds) was slightly higher than that determined for gelatin hard capsules (288±19 seconds). The hardness and dissolution time of gelatin and HPMC capsules were not significantly influenced by the irradiation type and the applied irradiation dose. As the viscometry analyses are concerned, irradiation caused a reduction of the intrinsic viscosity and water and dimethyl sulfoxide solvent power in both the cases. AFM analysis showed that the radiation treatment did not appreciably affect the surface roughness of the samples nor induce structural changes on capsule surface. However, measurements of force-distance curves pointed out a qualitative parameter for the identification of the irradiated capsules. On the bases of these preliminary results, empty gelatin or HPMC hard capsules can be sanitized/sterilized by ionizing radiation.

Atomic force microscopy imaging of Xenopus laevis oocyte plasma membrane purified by ultracentrifugation.

Atomic force microscopy (AFM) was used to investigate the native plasma membrane of Xenopus laevis (X. laevis) oocyte purified by means of ultracentrifugation on sucrose gradient and subsequently adsorbed on mica leaves through a physisorption process. Reproducible AFM topography images were collected, analyzed, and compared. AFM images showed the presence of large single or double bilayer membrane sheets covered with protein complexes. The lateral dimension and height of protein complexes imaged in air showed a normal distribution centred on 15.4 ± 0.4 nm (mean ± SE; n = 59) and 3.9 ± 0.2 nm (mean ± SE; n = 57), respectively. A density of about 270 protein complexes per square micron was calculated. Less frequently, ordered nanometer domains with densely packed protein complexes arranged in hexagonal patterns were also visualized in AFM images, confirming previously published data. Their lateral dimension and height showed a normal distribution centred on 23.0 ± 0.4 nm (mean ± SE; n = 42) and 1.5 ± 0.6 nm (mean ± SE; n = 90), respectively. A density of about 870 protein complexes per square micrometer was calculated. Advantages and drawbacks of this new sample preparation for AFM imaging are discussed. Microsc. Res. Tech., 2008.

X-ray microscopy of living multicellular organisms with the Prague Asterix Iodine Laser System

Soft X-ray contact microscopy (SXCM) experiments have been performed using the Prague Asterix Iodine Laser System (PALS). Laser wavelength and pulse duration were λ = 1.314 μm and τ (FWHM) = 450 ps, respectively. Pulsed X rays were generated using teflon, gold, and molybdenum targets with laser intensities I ≥ 1014 W/cm2. Experiments have been performed on the nematodes Caenorhabditis elegans. Images were recorded on PMMA photo resists and analyzed using an atomic force microscope operating in contact mode. Our preliminary results indicate the suitability of the SXCM for multicellular specimens.

Study of Multicellular Living Organisms by SXCM (Soft X-Ray Contact Microscopy)

Soft X-ray Contact Microscopy (SXCM) of Caenorhabditis elegans nematodes wit typical length 800 μm and diameter 30 μm has been performed using the PALS laser source of wavelength λ = 1.314 μm and pulse duration τ (FWHM) = 400 ps. Pulsed soft X-rays were generated using molybdenum and gold targets with laser intensities I ≥ 1014 W/cm2. Images have been recorded on PMMA photo resists and analyzed using an atomic force microscope operating in contact mode. Cuticle features and several internal organs have been identified in the SXCM images including lateral field, cuticle annuli, pharynx, and hypodermal and neuronal cell nuclei.