Diameter Microspheres Research Articles

Control of magnetophoretic mobility by susceptibility-modified solutions as evaluated by cell tracking velocimetry and continuous magnetic sorting.

With the analytical expression for the magnetophoretic mobility of an ideal, linearly polarizable sphere undergoing creeping motion in viscous medium, we have shown that both attractive and repulsive motions are possible in the magnetic field. We have validated theoretical predictions using magnetic monodisperse microspheres of 5.2-microm diameter and nonmagnetic polystyrene microspheres of 6.99-microm diameter suspended in solutions of paramagnetic ions. The microsphere magnetophoretic mobility was measured using a modified particle tracking velocimetry system, developed in-house and called a cell tracking velocimeter. The product of measured mobility and viscosity agrees well with the theoretical prediction, differing only by approximately 11%. Further, a 26% increase in resolution between magnetic and nonmagnetic particle distributions was evaluated when paramagnetic ion carrier was used instead of water. Continuous particle sorting based on differences in magnetophoretic mobility was performed with another device developed by us, the quadrupole magnetic flow sorter (QMS). In the QMS, the introduction of paramagnetic ions into the carrier was effective in suppressing nonspecific crossover (i.e., the transport of low-mobility particles into the magnetic particle fraction) in particles and in biologically relevant red blood cells and thus showed promise as a means of increasing the purity of the magnetic separation.

Structure and Magnetic Properties of Polymer Microspheres Filled with Magnetite Nanoparticles

The structure and magnetic properties of collagen microspheres filled with magnetite nanoparticles are studied. The average interparticle separation in the polymer matrix and the size of magnetite nanoparticles before and after the introduction of the nanoparticles into the matrix are determined using electron microscopy. The magnetization curve of the microspheres has a superparamagnetic character. The magnetite nanoparticles undergo no aggregation during the synthesis of microspheres and are evenly distributed over the matrix. The magnetic susceptibility data for magnetic polymer microspheres of different diameters suggest that, at small diameters (<300 μm), all of the nanoparticles, aligned in chains, contribute to magnetization; at large diameters, some of the chains give way to clusters, the chains are shorter, and, accordingly, the susceptibility is lower.

X-ray fluorescence and the study of microcirculation

The feasibility of using K-shell X-ray fluorescence (XRF) technique for study of subchondral bone microcirculation in ex vivo samples is examined. Studies have been carried out at the Daresbury Laboratory Synchrotron Radiation Source (SRS) ultra-dilute extended X-ray absorption fine structure beamline. Initial investigations were made on fine-bore capillaries with diameters of either 500 or 200 μm, attenuated by up to 2 mm of Perspex and containing dilute iodine-based contrast media. This allowed comparison to be made with the capabilities of angiographic imaging systems, also allowing definition of suitable XRF set-up parameters for subsequent microcirculation studies. Measurements were obtained in 30 s run times, for concentrations of iodine ( K ab 33.164 keV) down to <0.4 mg I 2/(ml saline). Intensities were linear up to 3.7 mg/ml, self-absorption becoming significant for concentrations beyond this. To determine detection limits, preliminary studies of subchondral bone microcirculation were made on bone sections which were known to be poorly infused with silver-coated ( K ab 25.517 keV) 30 μm diameter microspheres. For a 2 mm slice of bone, the presence of small numbers of silver-coated microspheres were detected in the first 2 mm layer from the surface, at a level equivalent to ∼1 ppm of silver solution.

Evaluation of spherical particle sizes with an asymmetric illumination microscope

A polarized microscope system is used to perform goniometric measurements of light scattered by small particles. The light incident angle on a sample of monodispersed latex microspheres is increased sequentially and a microscope objective lens collects scattered light from the samples. Light is only collected at angles greater than the objective lens numerical aperture (NA) so that only light scattered by the spheres is collected. The experimental results were modeled with a Mie theory-based algorithm. Experiments conducted with microspheres of diameter 1.03, 2.03, and 6.4 /spl mu/m show that, by decreasing the objective lens NA from NA=0.55 to NA=0.0548, a more distinguishable scattering pattern is detectable. From these highly shaped curves, we found that the size of a sphere of nominal diameter 2.03 /spl mu/m was 2.11 /spl plusmn/0.06 /spl mu/m and a 6.4 /spl mu/m sphere was 6.34 /spl plusmn/0.07 /spl mu/m.

Diffusion and directed motion in cellular transport.

We study the motion of a probe driven by microtubule-associated motors within a living eukaryotic cell. The measured mean square displacement, <x(t)2> of engulfed 2 and 3 microm diameter microspheres shows enhanced diffusion scaling as t(3/2) at short times, with a clear crossover to ordinary or subdiffusive scaling, i.e., t(gamma) with gamma less than or equal to 1, at long times. Using optical tweezers we tried to move the engulfed bead within the cell in order to relate the anomalous diffusion scaling to the density of the network in which the bead is embedded. Results show that the larger beads, 2 and 3 microm diameter, must actively push the cytoskeleton filaments out of the way in order to move, whereas smaller beads of 1 microm diameter can be "rattled" within a cage. The 1 microm beads also perform an enhanced diffusion but with a smaller and less consistent exponent 1.2<gamma<1.45. We interpret the half-integer power observed with large beads based on two diverse phenomena widely studied in purified cytoskeleton filaments: (1) the motion of the intracellular probe results from random forces generated by motor proteins rather than thermal collisions for classical Brownian particles, and (2) thermal bending modes of these semiflexible polymers lead to anomalous subdiffusion of particles embedded in purified gel networks or attached to single filaments, with <x(t)2> approximately t(3/4). In the case of small beads, there may also be a Brownian contribution to the motion that results in a smaller exponent.

The N-terminal peptide of PSGL-1 can mediate adhesion to trauma-activated endothelium via P-selectin in vivo

AbstractP-selectin glycoprotein ligand-1 (PSGL-1) is present on leukocytes and is the major ligand for endothelial expressed P-selectin. A variety of studies strongly suggests that the N-terminal region of PSGL-1 contains the binding site for P-selectin. We hypothesized that this relatively small N-terminal peptide of PSGL-1 is sufficient to support adhesion to P-selectin in vivo. To test this hypothesis, we coated 2 μm–diameter microspheres with a recombinant PSGL-1 construct, termed 19.ek.Fc. The 19.ek.Fc construct consists of the first 19 N-terminal amino acids of mature PSGL-1 linked to an enterokinase cleavage site that, in turn, is linked to human immunoglobulin G Fc. The 19.ek.Fc-coated microspheres were injected into the jugular vein of mice. Intravital microscopy of postcapillary venules within the cremaster muscle of mice revealed that a significantly greater number of 19.ek.Fc microspheres rolled compared with control microspheres. The number of rolling 19.ek.Fc microspheres was significantly diminished by pretreatment of the mice with a monoclonal antibody to P-selectin or by pretreatment of the 19.ek.Fc microspheres with a monoclonal antibody to PSGL-1. Combined, the results indicate that the N-terminal peptide of PSGL-1 can mediate adhesion to trauma-activated microvascular endothelium via P-selectin in vivo.

Concentrated solutions of salivary MUC5B mucin do not replicate the gel-forming properties of saliva

We have developed a new approach to study the molecular organization of salivary mucus and salivary mucins using confocal fluorescence recovery after photobleaching (confocal-FRAP). MUC5B mucin, its reduced subunit and T-domains were prepared from saliva and fluorescently labelled. The translational self-diffusion coefficients were determined up to 3.6mg/ml by confocal-FRAP. The results suggest that, in solutions of purified MUC5B mucin, at concentrations at which the hydrodynamic domains overlap, the intermolecular interactions are predominantly due to dynamic entanglements, and there was no evidence of specific self-association of MUC5B mucin, or of its subunits, or T-domains. The analysis of the salivary mucus gel also showed no specific interactions with the purified MUC5B components, but it was much less permeable than expected from its MUC5B content. The saliva was completely permeable to microspheres of 207nm diameter, but showed size-dependent effects on the diffusion of larger microspheres (499nm and 711nm diameter). From these analyses the salivary mucus was shown to be both permeable and dynamic, and with the characteristics of a semi-dilute transient network at physiological concentration. Comparison of the results from saliva and purified MUC5B mucin solutions showed that the network properties of saliva were equivalent to a solution of purified MUC5B mucin of 10–20 times higher concentration. This showed that saliva has additional structure and organization not present in the purified MUC5B mucin and suggests there are other interactions and/or components within saliva that combine with MUC5B to produce its complete properties.

Diffusion weighted imaging and magnetic resonance imaging are normal after significant microembolic insult, but magnetic resonance spectroscopy is abnormal in the first 24 hours

Introduction. Neurobehavioral deficits are common after cardiopulmonary bypass, but magnetic resonance imaging (MRI) seldom reveals significant abnormalities. We would be better able to evaluate new neuroprotective interventions if a sensitive quantifiable measure of acute brain injury were available. Diffusion weighted imaging (DWI) is purported to be sensitive to acute brain injury, and several clinical trials are under way using DWI to determine if off-pump coronary artery bypass grafting causes less brain injury than traditional on-pump procedures. In an effort to empirically determine the actual sensitivity of the various neuroradiologic imaging techniques, we embolized one hemisphere of a dog and performed repeated scans over the next 6 hours. We scanned a second dog 24 hours postembolization. We report here our initial results. Methods. After institutional Animal Care and Use Committee approval, 2 dogs were anesthetized with pentobarbital IV. A midline scalp incision was made and a thermistor was positioned against the cranium beneath the right temporalis muscle. After the head was cooled to >2°C topically with ice, the common carotid artery was injected with 50 μm diameter microspheres (approximately 10,000). MRI scanning was performed at either 1 to 6 hours or 24 to 26 hours postembolization (P-EMB). The brain was removed and evaluated for histologic abnormalities and the emboli counted. Approximately 1200 microspheres were delivered to the embolized hemisphere and 100 to the contra-lateral midline cortex. During the 1- to 6-hour P-EMB period, the dog was repeatedly scanned for the following analysis: MRI T-2, magnetic resonance spectroscopy (MRS), DWI, perfusion weighted imaging (PWI), and FLAIR-fluid attenuated inversion recovery. Results. MRI and DWI were normal at 6 and 24 hours P-EMB. Flow asymmetries became apparent at 2.5 hours. At 4 hours P-EMB, using a new multi-voxel (n = 25) MRS mapping program, a large increase of the lactate spectra primarily affecting the embolized hemisphere became visible with contralateral hemisphere remaining mostly unaffected except for the midline structures (figure below). At 24 hours, te elevation in lactate spectra was still obvious. Conclusions. MRI/DWI techniques are excellent at detecting large ischemic areas in the brain that may or may not be associated with clinical symptoms depending on the lesion location. However, acute brain injury caused by cerebral microembolization is undetected by MRI/DWI. MRS is not routinely performed but appears to be a sensitive method to detect early changes in brain metabolism that may be better associated with measures of neurobehavioral dysfunction post CPB.[1Stump D.A. Rogers A.T. Hammon J.W. Newman S.P. Cerebral emboli and cognitive outcome after cardiac surgery.J Cardiothorac Vasc Anesthes. 1996; 10: 113-118Abstract Full Text PDF PubMed Scopus (218) Google Scholar, 2Neumann-Haefelin T. et al.New magnetic resonance imaging methods for cerebrovascular disease emerging clinical applications.Ann Neurol. 2000; 47: 559-570Crossref PubMed Scopus (130) Google Scholar] Supported by a grant from the Charles A. Dana foundation.

Glomerular β-galactosidase expression following transduction with microsphere-adenoviral complexes

The aortic injection of adenoviral-microsphere complexes is a useful technique for in vivo gene transfer (transduction) to the glomerulus. In this approach, the appearance of the foreign transprotein in the glomerulus may result from glomerular cell gene transfer and local synthesis or hepatic cell transduction followed by synthesis, secretion, and deposition in the glomerulus. We postulated that glomerular expression of the foreign transgene was the result of glomerular cell transduction. To test this question, male SD rats underwent aortic injections with adenovirus containing the LacZ expression cassette [expressing beta-galactosidase (betagal)] coupled to 16 microm diameter microspheres. After 48 hours, histologic staining confirmed glomerular expression of the betagal transprotein and reverse transcription in situ polymerase chain reaction demonstrated the presence of the betagal transgene in the glomerulus. In addition, hepatic expression of the betagal transprotein was minimal and substantially less than that observed in the glomeruli. These data support the contention that adenoviral-microsphere complexes result in glomerular cell transduction with the desired transgene, followed by local transprotein synthesis. This approach may prove useful for facilitating glomerular gene transfer in the development of gene therapy for glomerulonephritis.

Excitation energy transfer from polystyrene to dye in 40-nm diameter microspheres

When dye molecules are placed into a solid, like a polymer matrix, the opportunity exists for resonant excitation energy transfer from the solid to the dye. We observe a 51% excitation transfer efficiency from polystyrene to the fluorescent dye BODIPY ® 564/591 in 40-nm polystyrene microspheres manufactured for use as fluorescent bioprobes. The Förster radius for this transfer is 19 Å. Despite this modest value for R 0, the high concentration of dye in these spheres permits efficient excitation transfer. Absorption, fluorescence, and fluorescence excitation spectra for the polystyrene spheres with and without dye are reported. Our work highlights the idea that the solid need not just be a structural entity in the creation of a fluorescent material. It can play the role of an element in an excitation transfer network. The solid's absorption of light can sensitize fluorescence from the dye molecules through excitation transfer, increasing the overall emission of the dye. Application to the area of biological fluorescence probe development is discussed.

Surface deformation on azobenzene polymer film induced by optical near-field around polystyrene microspheres

The surface deformations of a urethane–urea copolymer containing azobenzene derivatives under the influence of the electric fields around polystyrene microspheres irradiated with polarized light were investigated. Monolayers of 500 and 100 nm diameter microspheres were formed on the copolymer surface and were irradiated with linearly polarized laser beam. After removing the microspheres, the copolymer surfaces were observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The dents were formed on the copolymer surface where the microsphere had been located. The 500 nm microsphere caused the dent with sides heaped up along the polarization of the incident light; the dent was similar to the one induced by Gaussian beam, indicating that the surface deformation had relation to the electric field around the microsphere. On the contrary, the dent induced by the 100 nm microsphere showed weak dependence on the polarization in shape. This is ascribed to the interaction between the optical near-field of the microsphere and the substrate surface.

Hepatic arterial perfusion regulates portal venous flow between hepatic sinusoids and intrahepatic shunts in the normal rat liver in vitro.

Intrahepatic shunts regulate portal venous pressure during periods of acute portal hypertension when the transhepatic portal resistance is momentarily increased in the normal rat liver in vivo. Hepatic arterial inflow may also increase the transhepatic portal resistance and activate intrahepatic shunts. In the present study, the transhepatic portal resistance and the activity of intra-hepatic shunts were measured in vitro and the point of confluence between the hepatic artery and portal vein in the rat determined. Livers of male Sprague-Dawley rats were single-pass, dual-perfused in vitro. Total cessation or diversion of the hepatic arterial inflow to the portal venous vasculature, whilst maintaining total hepatic perfusate flow, decreased intrasinusoidal pressure, increased transhepatic portal venous resistance and opened the portal venous intrahepatic shunts in a manner similar to intraportal injection of 15-microm diameter microspheres. Injections of the microspheres into the hepatic arterial circulation increased hepatic arterial pressure dramatically, consistent with complete occlusion of the arterial vasculature. The intrahepatic shunts are located at a pre-sinusoidal level because no increases were detected in hepatic arterial pressure following intraportal injection of microspheres. The hepatic arterial vasculature, unlike the portal supply, does not possess a collateral shunt circulation and coalesces with the portal vein at an intrasinusoidal location

Heterogeneity of signal transduction at the subcellular level: microsphere-based focal EGF receptor activation and stimulation of Shc translocation.

Epidermal growth factor receptor (EGFR, erbB1) activation and translocation of the Shc adaptor protein to activated receptors were analyzed at the subcellular level by dual-label immunofluorescence and confocal laser scanning microscopy in conjunction with a new microsphere-based protocol. In the Quantitative Microsphere Recruitment Assay (QMRA) introduced here, epidermal growth factor-coated 1 microm diameter microspheres were distributed over the surface of adherent tissue culture cells expressing the receptor. High-resolution confocal microscopy of a fusion construct of the receptor and the green fluorescent protein expressed in Chinese hamster ovary cells demonstrated that engulfment and internalization of the microspheres occurred rapidly within minutes, and in a receptor activation-dependent manner. In human epidermoid carcinoma A431 cells, receptor activation and Shc translocation persisted over the 20-minute time course of the experiments. However, at the subcellular level the positive correlation of receptor activation and Shc translocation observed at 5-8 minutes dissipated, indicating a time-dependent decoupling of the two events and variation in the kinetics of signal transduction for different subcellular locations.

Oral immunization with size-purified microsphere beads as a vehicle selectively induces systemic tolerance and sensitization

Oral administration of antigens has long been recognized as a method to prevent or delay the onset of diseases associated with untoward immune responses to self and non-self antigens. Although oral administration of antigens offers a convenient way to induce systemic tolerance, its therapeutic potential has been seriously limited by the fact that it requires repeated feeding of a large amount of antigens and that it may deteriorate ongoing autoimmune diseases when autoantigens are employed. We have previously shown that orally administered poly- D, L-lactic acid (PDLLA) microspheres containing an antigen were selectively distributed to Peyer’s patches (PP) and systemic lymphoid tissues according to their diameter and then released the antigen over a long period of time. We now report that a single dose of intragastric immunization with a PDLLA microsphere 7–10 μm in diameter and containing 2 mg of OVA was as effective as 100 mg of water soluble OVA to suppress OVA-specific IgG and DTH response. This was associated with a large increase of Interferon-γ production by PPT cells stimulated with an antigen and a small increase in secretory IgA specific to OVA. In contrast, administration of an antigen encapsulated in microspheres 3–4 μm in diameter led to an enhanced OVA-specific IgG response and no significant increase in OVA-specific secretory IgA. Thus, by utilizing microspheres of an appropriate diameter as a vaccination vehicle, we were able to selectively induce both systemic tolerance and sensitization by oral ingestion of single low dose of an antigen.

Effect of immersion in SBF on porous bioactive bodies made by sintering bioactive glass microspheres

Since the mid 90s it has been possible to draw fibers and manufacture microspheres of novel bioactive glasses. Thus, by sintering bioactive glass microspheres it is now possible to form porous textures, in which the bioactive surface area is increased manifold compared with non-porous bodies. Four different types of porous bodies were made by sintering glass microspheres of diameter 250–300 μm. Two of the body types contained only one kind of spheres; either highly bioactive glass spheres or spheres made of glass having a low bioactivity (biocompatible glass). Two additional types of test bodies were obtained by sintering mixtures of bioactive and biocompatible spheres (composites). The dissolution of silica and calcium into simulated body fluid (SBF) was determined at different time intervals using a direct current plasma atomic emission spectrometer (DCPAES). The influence of immersion on the mechanical strength of the porous structures was studied by means of a compression test. Further, the thickness of the silica-rich gel formation on the surface of bioactive glass spheres was measured at each time interval using back-scattered electron imaging of scanning electron microscopy (BEI-SEM). A non-porous glass rod made from the same bioactive glass was used as the control. The results showed that dissolution of silica and calcium into SBF from the porous glass texture was inversely related to the silica content of the glass. The rate of silica gel formation on the sintered bioactive microspheres was significantly higher than on a rod made from the same glass. The initial mechanical strength of porous bodies consisting of only one kind of glass was 17–20 MPa. However, these bodies lost their mechanical strength at an early stage of the immersion showing compression strength of only 7–8 MPa at 14 days of immersion. The initial strength of composite glass bodies (7–11 MPa) was lower compared with bodies containing only one kind of glass but the bodies showed no notable mechanical weakening during the test. Softening of the surface of smooth bioactive glass plates correlated well with the formation of the silica-rich layer on the plate. Interestingly, the study also showed that in porous glass structures containing both bioactive and biocompatible glass the biocompatible glass can act as a site for calcium phosphate precipitation.

Multiphoton-Excited Fluorescence Imaging and Photochemical Modification of Dye-Doped Polystyrene Microsphere Arrays

The use of nonlinear optical methods for thin-film polymeric materials modification and characterization is explored. Ordered 3-dimensional (3-D) dye-doped polystyrene microsphere arrays are photobleached and imaged in these studies. Efficient, irreversible photochemical bleaching of the dye within individual 0.5 and 1 μm diameter microspheres occurs when 810 nm light from a mode-locked Ti:sapphire laser is focused to an ∼400 nm diameter spot within the spheres. Photobleaching is shown to result from three-photon absorption and may involve ionization of the dye. The three-photon-induced photochemistry is dramatically more efficient than that resulting from single-photon excitation. Imaging of the unbleached and bleached arrays is accomplished by monitoring the two-photon-excited fluorescence from the dye. Both the nonlinear photobleaching and imaging methods provide inherent depth-discriminating capabilities, allowing for high-resolution 3-D control of the volume modified and imaged. The results suggest t...

Screening unlabeled DNA targets with randomly ordered fiber-optic gene arrays

We have developed a randomly ordered fiber-optic gene array for rapid, parallel detection of unlabeled DNA targets with surface immobilized molecular beacons (MB) that undergo a conformational change accompanied by a fluorescence change in the presence of a complementary DNA target. Microarrays are prepared by randomly distributing MB-functionalized 3-microm diameter microspheres in an array of wells etched in a 500-microm diameter optical imaging fiber. Using several MBs, each designed to recognize a different target, we demonstrate the selective detection of genomic cystic fibrosis related targets. Positional registration and fluorescence response monitoring of the microspheres was performed using an optical encoding scheme and an imaging fluorescence microscope system.

Derivatized, swellable polymer microspheres for chemical transduction

Derivatized lightly cross-linked polymer microspheres that swell and shrink as a function of analyte concentration are useful chemical transduction elements that can be coupled to a variety of readouts, including methods based on changes in refractive index, physical displacement and electrical properties. We are preparing 0.3 to 3 μm diameter microspheres in one step by dispersion polymerization. To introduce porosity sufficient to allow analyte access to the interior of our microspheres, we are using polymer systems with hydrophilic backbones or using the particles prepared by dispersion polymerization as seed particles for two-step seeded emulsion polymerization which allows us to incorporate a porogenic solvent in the second step. Much of our work to date has been performed with pH-sensitive polymers, either aminated polystyrene or poly(4-hydroxy-3-nitro)styrene. More recently, we have incorporated ionophores into poly(4-hydroxy-3-nitro)styrene microspheres and demonstrated that ion binding accompanied by loss of a proton causes the polymer to swell. This provides a generic approach for incorporating ionophore selectivity into swellable polymer microspheres. We have been particularly interested in optical transduction with swellable polymer microspheres entrapped in a hydrogel. The measured parameter is the change in optical properties of the gel that accompany swelling. This can be measured in the near infrared using technology developed for fiber optic communications.

Uptake of orally administered polystyrene latex and poly(D,L-lactic/glycolic acid) microspheres into intestinal lymphoid tissues in chickens

Fluorescein-labeled microspheres were orally administered to chickens and their distribution in intestinal lymphoid tissues was investigated. Polystyrene latex microspheres were observed in Peyer's patches, and also in the Meckel's diverticulum and the jejunum. Their density, however, seemed to be lower than that in Peyer's patches. Microspheres were rarely observed in the other intestinal tissues examined, including the bursa of Fabricius. Of note is that, although microspheres were present in the lumen, few, if any, were observed in the lamina propria of the caecal tonsil and caecum. Polystyrene latex microspheres of diameter 2.0 μm or 4.5 μm were also observed in Peyer's patches, but their density seemed to be lower as compared with the 0.75 μm microspheres. Poly( d, l-lactic/glycolic acid) (PLGA) microspheres were prepared using PLGAs of various molecular weights (MW) and their uptake into Peyer's patches was compared. Microspheres prepared with PLGA of average MW of 20 000 were not taken up into Peyer's patches, but those prepared with PLGA of average MW of 61 000 or 99 800 were taken up into Peyer's patches.

Description of a dust particle detection system and measurements of particulate contamination from shock, gate valve, and ion pump under ultrahigh vacuum conditions

Dust particle contamination is known to be responsible for reduced quality and yield in microelectronic processing. However it may also limit the operation of particle accelerators as a result of beam lifetime reduction or enhanced field emission in radio-frequency accelerating cavities. Intrinsic dust contamination from sources such as valves or ion pumps has not yet been studied due to the inability of commercial particle counters to be able to detect across large cross sections under ultrahigh vacuum (UHV) conditions. This motivated the development of the dust particle detector described here which is able to quantify, in situ, the level of contamination on a representative part of a vacuum vessel. This system operates under UHV conditions and measures flashes of scattered light from free falling dust particles as they cross a thin laser light sheet across a 100 mm diam vacuum vessel. A calibration using microspheres of known diameter has allowed estimation of the particle size from the scattered signal amplitude. Measurements of particulate contamination generated by shocks onto the vessel walls are presented and determination of the height of origin of dust particles from their transit time across the irradiation sheet is discussed. Measurements of dust particle release right to operation of an all-metal gate valve are also presented in the form of time resolved measurements of dust occurrence during the open/close cycles of the valve, as well as histograms of the particle size distribution. A partial self-cleaning effect is witnessed during the first 10 operation cycles following valve installation. The operation of an ion pump has also been investigated and revealed that, in our conditions, particles were released only at pump startup.