Fouling of nanostructured insect cuticle: adhesion of natural and artificial contaminants

The adhesional properties of contaminating particles of scales of various lengths were investigated for a wide range of micro- and nanostructured insect wing cuticles. The contaminating particles consisted of artificial hydrophilic (silica) and spherical hydrophobic (C₁₈) particles, and natural pollen grains. Insect wing cuticle architectures with an open micro-/nanostructure framework demonstrated topographies for minimising solid–solid and solid–liquid contact areas. Such structuring of the wing membranes allows for a variety of removal mechanisms to contend with particle contact, such as wind and self-cleaning droplet interactions. Cuticles exhibiting high contact angles showed considerably lower particle adhesional forces than more hydrophilic insect surfaces. Values as low as 3 nN were recorded in air for silica of ～28 nm in diameter and <25 nN for silica particles 30 μm in diameter. A similar adhesional trend was also observed for contact with pollen particles.     

Putative functions and functional efficiency of ordered cuticular nanoarrays on insect wings

The putative functions and functional efficiencies of periodic nanostructures on the surface of cicada wings have been investigated by atomic force microscopy (AFM) used as a tool for imaging, manipulation, and probing of adhesion. The structures consist of hexagonal close-packed protrusions with a lateral spacing of ∼200 nm and may have multiple functionalities. Not only do the structures confer survival value by virtue of camouflage, but they may also serve as antiwetting and self-cleaning surfaces and thus be resistant to contamination. These effects have been demonstrated by exposure to white light, liquid droplets, and AFM adhesion measurements. The dependence of optical reflectivity and surface adhesion on surface topography has been demonstrated using AFM as a nanomachining tool as well as an imaging and force-sensing probe. The intact arrays display exceptionally low adhesion for particles in the size range 20 nm-40 μm. The particles can be removed from the array by forces in the range 2-20 nN; conversely, forces in the range 25-230 nN are required to remove identical particles from a flat hydrophilic surface (i.e., polished Si). Measurements of contact angles for several liquids and particle adhesion studies show that the wing represents a low-surface-energy membrane with antiwetting properties. The inference is that a combination of chemistry and structure constitutes a natural technology for conferring resistance to contamination.     

A dual layer hair array of the brown lacewing: repelling water at different length scales

Additional weight due to contamination (water and/or contaminating particles) can potentially have a detrimental effect on the flight capabilities of large winged insects such as butterflies and dragonflies. Insects where the wing surface area-body mass ratio is very high will be even more susceptible to these effects. Water droplets tend to move spontaneously off the wing surface of these insects. In the case of the brown lacewing, the drops effectively encounter a dual bed of hair springs with a topographical structure which aids in the hairs resisting penetration into water bodies. In this article, we demonstrate experimentally how this protective defense system employed by the brown lacewing (Micromus tasmaniae) aids in resisting contamination from water and how the micro- and nanostructures found on these hairs are responsible for quickly shedding water from the wing which demonstrates an active liquid-repelling surface.     

Synthesis of novel porous magnetic silica microspheres as adsorbents for isolation of genomic DNA

An improved procedure is described for preparation of novel mesoporous microspheres consisting of magnetic nanoparticles homogeneously dispersed in a silica matrix. The method is based on a three-step process, involving (i) formation of hematite/silica composite microspheres by urea-formaldehyde polymerization, (ii) calcination of the composite particles to remove the organic constituents, and (iii) in situ transformation of the iron oxide in the composites by hydrogen reductive reaction. The as-synthesized magnetite/silica composite microspheres were nearly monodisperse, mesoporous, and magnetizable, with as typical values an average diameter of 3.5 microm, a surface area of 250 m(2)/g, a pore size of 6.03 nm, and a saturation magnetization of 9.82 emu/g. These magnetic particles were tested as adsorbents for isolation of genomic DNA from Saccharomyces cerevisiae cells and maize kernels. The results are quite encouraging as the magnetic particle based protocols lead to the extraction of genomic DNA with satisfactory integrity, yield, and purity. Being hydrophilic in nature, the porous magnetic silica microspheres are considered a good alternative to polystyrene-based magnetic particles for use in biomedical applications where nonspecific adsorption of biomolecules is to be minimized.     

Significance of exine shedding in Cupressaceae-type pollen

In conifers, which have non-saccate Cupressaceae-type pollen, the pollen must land on a pollination drop or be picked up by the pollination drop from the surface of the cone near the ovule before it can be taken into the ovule. After contact with the drop, the pollen intine absorbs moisture from the drop, expands and the exine is shed. In this study the significance of the shedding of the exine is interpreted from experiments in which simulated pollination drops and micropyles were used to determine the movement of pollen and other particles in suspension. The non-expanded pollen, which can be observed upon contact with the pollination drop, sheds the exine, which then functions as a non-elastic particle, while the pollen from which the exine was shed swells and functions as an elastic particle because it is enclosed by the flexible intine. Non-elastic particles are not easily transferred through narrow passages (the micropyle and micropylar canal) and tend to plug these passages. However, elastic particles, such as the swollen pollen, are easily transferred along narrow passages even when non-elastic particles are present. The simulated experiments demonstrate that exine shedding is an important feature in getting pollen through the narrow micropyle and micropylar canal to the nucellus of the ovule.     

Influence of cuticle nanostructuring on the wetting behaviour/states on cicada wings

The nanoscale protrusions of different morphologies on wing surfaces of four cicada species were examined under an environmental scanning electron microscope (ESEM). The water contact angles (CAs) of the wing surfaces were measured along with droplet adhesion values using a high-sensitivity microelectromechanical balance system. The water CA and adhesive force measurements obtained were found to relate to the nanostructuring differences of the four species. The adhesive forces in combination with the Cassie-Baxter and Wenzel approximations were used to predict wetting states of the insect wing cuticles. The more disordered and inhomogeneous surface of the species Leptopsalta bifuscata demonstrated a Wenzel type wetting state or an intermediate state of spreading and imbibition with a CA of 81.3° and high adhesive force of 149.5 μN. Three other species (Cryptotympana atrata, Meimuna opalifer and Aola bindusara) exhibited nanostructuring of the form of conically shaped protrusions, which were spherically capped. These surfaces presented a range of high adhesional values; however, the CAs were highly hydrophobic (C. atrata and A. bindusara) and in some cases close to superhydrophobic (M. opalifer). The wetting states of A. bindusara, C. atrata and M. opalifer (based on adhesion and CAs) are most likely represented by the transitional region between the Cassie-Baxter and Wenzel approximations to varying degrees.     

Quantitative Measurement ed Pollen Tube Growth and Particle Movement

The growth of pollen tube and the cytoplasmic particle movements in pollen tube of Aloe zebrina Haw. were recorded by micro-video and measured by computer image analysis. The saltatory growth of pollen tube was observed. The movement velocity, diameter and the rate of flux of forward particles towards pollen tube tip were greater than those of backward particles. The results indicate that the cytoplasmic particle movements may play a role in transporting “building blocks” for pollen tube growth.     

An electron microscope study of the morphology and distribution of the intracytoplasmic virus-like particles of Ehrlich ascites tumor cells

Electron microscope studies of eight different sublines of Ehrlich ascites tumor cells which had not, as far as could be determined, come in contact with any known virus, revealed dense particles measuring approximately 55 to 70 mmicro in diameter, both within and attached to the wall of cytoplasmic vesicles identified as the endoplasmic reticulum. All tumor sublines contained significant numbers of particles and revealed no qualitative or quantitative differences in particle morphology or distribution. It is concluded that these structures are a constant morphological component of the Ehrlich ascites tumor and that they probably do not represent contaminating virus. Their morphology and distribution are described, and the possible interpretations of their significance are discussed.     

Release behavior of small sized daughter allergens from Cryptomeria japonica pollen grains during urban rainfall event

In Japan, Cryptomeria japonica pollen (with diameter ~30 μm) is scattered during each spring season. Daughter allergenic particles, which are smaller in size than their parent pollen grain and are abundant in fine particles (the particle sizes < 1.1 μm, PM_1.1), are released in the atmosphere. The daughter allergenic particles of pollen can be transported in the urban atmosphere for a long period of time after their release. In particular, the daily variation delays in the peaks of allergenic Cry j 1 concentrations compared with the peaks of airborne parent pollen counts were observed in high levels during 1 or 2 sunny days after rainfall. In addition, long range transportation of Asian dusts (ADS) from the East Asian continent was also found during the pollen scattering seasons in Japan. Therefore, the interaction between pollen and air pollutants, including ADS, should be of concern. Thus, in this study, the morphological change of Cryptomeria japonica pollen and the elution behavior of its allergenic contents (Cry j 1) were investigated. Our results confirmed the existence of fine daughter allergen particles, which are clearly differ from the parent pollen grains in size. Fine allergenic particles in atmosphere were increased, while coarse allergenic particles were decreased on sunny days after rainfall. However, the correlation between the mass concentrations of fine particles and mass levels of Cry j 1 in coarse particles (the particle sizes > 7.0 μm) was poor. The possible reason may be pollen burst at high humidity before rainfall. Additionally, Cry j 1 contents were emitted from the so-called Ubisch body, which contains allergenic Cry j 1 abundantly when pollen was in contact with rainfall. In particular, we found that 60% of allergenic Cry j 1 contents released in air polluted rainfall contained Ca²⁺ ion derived from road dust and ADS. Therefore, rainfall should be a main factor to induce transition of pollen allergenic contents to fine particles. In conclusion, allergenic particles which are small sized and translated into fine particles by rainfall can be inhaled into the lower respiratory tract and contribute to the hypersensitivity of asthma.     

AN ELECTRON MICROSCOPE STUDY OF THE MORPHOLOGY AND DISTRIBUTION OF THE INTRACYTOPLASMIC "VIRUS-LIKE" PARTICLES OF EHRLICH ASCITES TUMOR CELLS

Electron microscope studies of eight different sublines of Ehrlich ascites tumor cells which had not, as far as could be determined, come in contact with any known virus, revealed dense particles measuring approximately 55 to 70 mµ in diameter, both within and attached to the wall of cytoplasmic vesicles identified as the endoplasmic reticulum. All tumor sublines contained significant numbers of particles and revealed no qualitative or quantitative differences in particle morphology or distribution. It is concluded that these structures are a constant morphological component of the Ehrlich ascites tumor and that they probably do not represent contaminating virus. Their morphology and distribution are described, and the possible interpretations of their significance are discussed.     

Bifunctional silica nanoparticles for the exploration of biofilms of Pseudomonas aeruginosa

Luminescent silica nanoparticles are frequently employed for biotechnology applications mainly because of their easy functionalization, photo-stability, and biocompatibility. Bifunctional silica nanoparticles (BSNPs) are described here as new efficient tools for investigating complex biological systems such as biofilms. Photoluminescence is brought about by the incorporation of a silylated ruthenium(II) complex. The surface properties of the silica particles were designed by reaction with amino-organosilanes, quaternary ammonium-organosilanes, carboxylate-organosilanes and hexamethyldisilazane. BSNPs were characterized extensively by DRIFT, ¹³C and ²⁹Si solid state NMR, XPS, and photoluminescence. Zeta potential and contact angle measurements exhibited various surface properties (hydrophilic/hydrophobic balance and electric charge) according to the functional groups. Confocal laser scanning microscopy (CLSM) measurements showed that the spatial distribution of these nanoparticles inside a biofilm of Pseudomonas aeruginosa PAO1 depends more on their hydrophilic/hydrophobic characteristics than on their size. CLSM observations using two nanosized particles (25 and 68?nm) suggest that narrow diffusion paths exist through the extracellular polymeric substances matrix.     

Flow chamber analysis of size effects in the adhesion of spherical particles

The non-specific adhesion of spherical micro- and nano-particles to a cell substrate is investigated in a parallel plate flow chamber. Differently from prior in-vitro analyses, the total volume of the particles injected into the flow chamber is kept fixed whilst the particle diameter is changed in the range 0.5-10 microm. It is shown that: (i) the absolute number of particles adherent to the cell layer per unit surface decreases with the size of the particle as d(-1.7); (ii) the volume of the particles adherent per unit surface increases with the size of the particles as d(+1.3). From these results and considering solely non-specific particles, the following hypothesis are generated (i) use the smallest possible particles in biomedical imaging and (ii) use the largest possible particles in drug delivery.     

Effects of Methanol on Wettability of the Non-Smooth Surface on Butterfly Wing

The contact angles of distilled water and methanol solution on the wings of butterflies were determined by a visual contact angle measuring system. The scale structures of the wings were observed using scanning electron microscopy, The influence of the scale micro- and ultra-structure on the wettability was investigated. Results show that the contact angle of distilled water on the wing surfaces varies from 134.0° to 159.2°. High hydrophobicity is found in six species with contact angles greater than 150°. The wing surfaces of some species are not only hydrophobic but also resist the wetting by methanol solution with 55% concentration. Only two species in Parnassius can not resist the wetting because the micro-structure （spindle-like shape） and ultra-structure （pinnule-like shape） of the wing scales are remarkably different from that of other species. The concentration of methanol solution for the occurrence of spreading/wetting on the wing surfaces of different species varies from 70% to 95%. After wetting by methanol solution for 10 min, the distilled water contact angle on the wing surface increases by 0.8°-2.1°, showing the promotion of capacity against wetting by distilled water.     

Factors governing the flow cytometric analysis and sorting of large biological particles

We have investigated the suitability of large flow cell tips for the flow cytometric analysis and sorting of large biological particles, including plant cells (pollen) and protoplasts. Using flow tips ranging in diameter from 79-204 micron, we have optimized conditions for the establishment of a stable hydrodynamic flow leading to accurate droplet production. We describe instrument modifications required for large particle sorting and demonstrate the use of these experimental conditions for the sorting to high purity of pollen and viable plant protoplasts possessing diameters as large as 95 micron. Our experiments have revealed a complex interaction among sorting efficiency, particle diameter, flow cell tip diameter and bimorphic crystal drive frequency. This interaction can be satisfactorily explained in terms of interference effects owing to phase differences between the particle-induced disturbance and the undulation driven by the bimorphic crystal.     

Cryo-electron tomography of nanoparticle transmigration into liposome

Nanoparticle transport across cell membrane plays a crucial role in the development of drug delivery systems as well as in the toxicity response induced by nanoparticles. As hydrophilic nanoparticles interact with lipid membranes and are able to induce membrane perturbations, hypothetic mechanisms based on membrane curvature or hole formation have been proposed for activating their transmigration. We report on the transport of hydrophilic silica nanoparticles into large unilamellar neutral DOPC liposomes via an internalization process. The strong adhesive interactions of lipid membrane onto the silica nanoparticle triggered liposome deformation until the formation of a curved neck. Then the rupture of this membrane neck led to the complete engulfment of the nanoparticle. Using cryo-electron tomography we determined 3D architectures of intermediate steps of this process unveiling internalized silica nanoparticles surrounded by a supported lipid bilayer. This engulfing process was achieved for a large range of particle size (from 30 to 200 nm in diameter). These original data provide interesting highlights for nanoparticle transmigration and could be applied to biotechnology development.     

Wettability and Contaminability of Insect Wings as a Function of Their Surface Sculptures

Abstract The wing surfaces of 97 insect species from virtually all relevant major groups were examined by high resolution scanning-electron-microscopy, in order to identify the relationships between the wing microstructures, their wettability with water and their behaviour under the influence of contamination. Isolated wings with contact angles between 31.6° and 155.5° were artificially contaminated with silicate dusts and subsequently fogged until drops of water (“dew”) formed and rolled off. The remaining particles were counted via a digital image analysis system. Remaining particle values between 0.41% and 103% were determined in comparison with unfogged controls. Some insects with very unwettable wings show a highly significant “self-cleaning” effect under the influence of rain or dew. Detailed analysis revealed that there is a correlation between the wettability and the “SM Index” (quotient of wing surface/(body mass)^0.67) with values ranging from 2.42 to 57.0. Furthermore, there is a correlation between the “self-cleaning” effect and the SM Index, meaning that taxa with a high SM Index, e.g. “large-winged” Ephemeroptera, Odonata, Planipennia, and many Lepidoptera, have very unwettable wings and show high particle removal due to dripping water drops. The “small-winged” insects, such as Diptera and Hymenoptera, and insects with elytra, such as Blattariae, Saltatoria, Heteroptera and Coleoptera, show completely opposite effects. This is clearly a result of the fact that species with a high SM Index are, in principle, more restricted in flight by contamination than species with a low SM Index which can also actively clean their own wings. The wings primarily serve a protection function in insects with elytra, so that the effects of contamination are probably of minor importance in these insects. Copyright © 1996 The Royal Swedish Academy of Sciences. Published by Elsevier Science Ltd.     

Action of particle films on the biology and behavior of pear psylla (Homoptera: Psyllidae)

Particle films with different properties have been developed for arthropod pest control. Two basic film types are hydrophobic and hydrophilic films. The hydrophilic film formulations differ in the amount and kind of spreader-sticker that is incorporated into the kaolin particles. The effects of particle film type (hydrophobic versus hydrophilic) and formulation (Surround versus Surround WP) on the biology and behavior of pear psylla, Cacopsylla pyricola (Foerster), were investigated on pear in a series of laboratory studies. Scanning electron microscopy determined that the number of particles that attached to the front tibia of adult psylla differed by particle formulation but the particle sizes were fairly uniform and ranged from 3.6 to 4.5 microm in diameter. Adults had difficulty grasping particle film-treated leaves, and this effect was influenced by film type and leaf surface. Choice and no-choice tests indicated that adult settling and oviposition were very low, regardless of film type or formulation. Under no-choice conditions, adult mortality was low, in part, because the adults were able to feed through all 3% particle films, but at reduced rates. However, the mortality of adults sprayed with 3% particle film solutions ranged from 22.2 to 62.5% within 72 h after treatment, and mortalities differed most between the hydrophilic formulations. Nymphs born on particle film-treated foliage incurred high mortalities ranging from 58.9 to 82.0% by the time they reached the fifth instar and were affected most by particle film type. Nymphal development was not affected by particle film type or formulation. Egg fertility and nymphal hatch also were unaffected by particle films. These studies determined that there are a number of biological effects particle films have on pear psylla beyond the deterrence of adult settling and oviposition.     

Filtering mechanism of the honey bee proventriculus

ABSTRACT. The fine structure and function of a honey bee's ( Apis mellifera Linn.) proventriculus were studied by scanning electron microscopy and video-recording. Our observations revealed that the proventriculus is used to engulf pollen and other particles which contaminate the nectar carried into the crop. The four lips are closed and opened, pulled backwards and straightened by the external circular muscles and internal longitudinal muscles. Combs of filiform-hairs (70 μm in length) located on the margins of the lips 'catch' and filter particles from the fluid. By repeated filtering, opening and closing actions of the hairs and lips, particles are filtered and collected in pouches between the ventricular folds to form boluses and are eventually passed into the midgut. In the present experiment, particle sizes ranging from 0.5 to 100 μm in diameter, including dandelion pollen ( Taraxacum officinale Web.), Torula yeast ( Candida utilis Lodder et Kreger-Van Rij), bee disease spores of Nosema apis Zander and Bacillus larvae White, and man-made particles can be filtered by the hairs. Small particles (0.23 μm in diameter) filter through the hair and return back to the fluid. Large particles (100–200 μm in diameter) are caught between the stylets of the mouthparts and are not ingested. These observations suggest that the particle size plays an important role in determining what can be taken by the mouthparts and the proventriculus and what can later be utilized as a food source by the bee. The role of the proventriculus in disease transmission is also discussed.     

Size distribution of allergenic Cry j 2 released from airborne <Emphasis Type="Italic">Cryptomeria japonica</Emphasis> pollen grains during the pollen scattering seasons

Japanese cedar (Cryptomeria japonica) pollinosis is one of seasonal allergic rhinitis that mainly occurs in Japan. The pollinosis is caused by two main kinds of allergenic proteins called Cry j 1 and Cry j 2 which exist in Cryptomeria japonica pollen. In our previous study, we reported that the size-segregated of airborne fine allergenic Cry j 1 and morphological change of Cry j 1 due to the contact with rainfall. However, the study on airborne allergenic Cry j 2 in different particle sizes has not been identified until now. Therefore, the main aim of this study is to investigate the size distribution and scattering behavior of allergenic Cry j 2. The Cry j 2 particles were collected and determined in different particle sizes at the urban sampling points during the most severe pollination season of 2012 in Saitama, Japan. After the size-segregated Cry j 2 allergenic particles were collected using an Andersen high-volume (AHV) atmospheric sample, the airborne Cry j 2 concentrations were determined with a surface plasmon resonance (SPR) method. At the same time, the airborne Cryptomeria japonica pollens were also counted by the Durham pollen sampler. The higher concentrations of the allergenic Cry j 2 were detected even in particle sizes equal to or less than 1.1 μm (PM_1.1) than other particle sizes. The airborne particles ranges from 0.06 to 11 μm were also collected by a low-pressure impactor (LPI) atmospheric sampler. After that, the concentrations of Cry j 2 allergenic particles in fine particle sizes were measured by the SPR method either. With the help of this study, we have confirmed the existence of fine daughter allergenic particles, which clearly differ from the parent pollen grains in size, especially after the rainy days. It is possible that the daughter allergenic species will be released from the fractions of cell wall and burst pollen grains. We concluded that rainwater was one of the important factors that affects the release of pollen allergenic proteins of both Cry j 1 and Cry j 2 from the parent pollen grains.     

Size control of silica nanoparticles and their surface treatment for fabrication of dental nanocomposites

Nearly monodispersed silica nanoparticles having a controlled size from 5 to 450 nm were synthesized via a sol-gel process, and then the optimum conditions for the surface treatment of the synthesized silica nanoparticles with a silane coupling agent (i.e., 3-methacryloxypropyltrimethoxysilane (gamma-MPS)) were explored to produce dental composites exhibiting enhanced adhesion and dispersion of silica nanoparticles in the resin matrix. The particle size was increased by increasing amounts of the catalyst (NH4OH) and silica precursor (tetraethylorthosilicate, TEOS) and by decreasing the amount of water in the reaction mixtures regardless of solvents used for the synthesis. The particle size prepared by using ethanol as a solvent was significantly larger than that prepared by using methanol as a solvent when the composition of the reaction mixture was fixed. The nanosized particles in the 5-25 nm range were aggregated. The amount of grafted gamma-MPS on the surface of the synthesized silica nanoparticles was dependent on the composition of the reaction mixture when an excess amount of gamma-MPS was used. When surface treatment was performed at optimum conditions found here, the amount of the grafted gamma-MPS per unit surface area of the silica nanoparticles was nearly the same regardless of the particle size. Dispersion of the silica particles in the resin matrix and interfacial adhesion between silica particles and resin matrix were enhanced when surface treated silica nanoparticles were used for preparing dental nanocomposites.