Surface Modified Glass Beads Research Articles

Fast optical method for characterizing plasmonic nanoparticle adhesion on functionalized surfaces

In this paper, a rapid optical method for characterizing plasmonic (gold) nanoparticle (AuNP) adhesion is presented. Two different methods were used for AuNP preparation: the well-known Turkevich method resulted in particles with negative surface charge; for preparing AuNPs with positive surface charge, stainless steel was used as reducing agent. The solid surface for adhesion was provided by a column packed with pristine or surface-modified glass beads. The size of the nanoparticles was studied by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS); the surface charge of the components was determined by streaming potential measurements. The characterization of adhesion was performed in a flow system by UV-Vis spectroscopy. During the adhesion experiments, the role of the surface charge, the particle size, and the pH were studied, as well as the adhered amount of gold nanoparticles and the surface coverage values. The latter was estimated by theoretical calculations and defined by the quotient of the measured and the maximal adhered amount of nanoparticles, which could be determined by the cross-sectional area of the NPs and the specific surface area of the glass beads. The results are verified by the polarization reflectometric interference spectroscopy (PRIfS) method: silica nanoparticles with diameters of a few hundred (d~450) nanometers were immobilized on the surface of glass substrate by the Langmuir–Blodgett method, the surface was modified similar to the 3D (continuous flow packed column) system, and gold nanoparticles from different pH solutions were adhered during the measurements. These kinds of modified surfaces allow the investigation of biomolecule adsorption in the same reflectometric setup.Graphical abstract

Influence of surface characteristics of modified glass beads as model carriers in dry powder inhalers (DPIs) on the aerosolization performance

The aim of this work is to investigate the effect of surface characteristics (surface roughness and specific surface area) of surface-modified glass beads as model carriers in dry powder inhalers (DPIs) on the aerosolization, and thus, the in vitro respirable fraction often referred to as fine particle fraction (FPF). By processing glass beads in a ball mill with different grinding materials (quartz and tungsten carbide) and varying grinding time (4 h and 8 h), and by plasma etching for 1 min, glass beads with different shades of surface roughness and increased surface area were prepared. Compared with untreated glass beads, the surface-modified rough glass beads show increased FPFs. The drug detachment from the modified glass beads is also more reproducible than from untreated glass beads indicated by lower standard deviations for the FPFs of the modified glass beads. Moreover, the FPF of the modified glass beads correlates with their surface characteristics. The higher the surface roughness and the higher the specific surface area of the glass beads the higher is the FPF. Thus, surface-modified glass beads make an ideal carrier for tailoring the performance of DPIs in the therapy of asthma and chronically obstructive pulmonary diseases.

Surface modified glass beads as model carriers in dry powder inhalers—Influence of drug load on the fine particle fraction

The relationship between surface coverage and in vitro respirable fraction—often referred to as fine particle fraction (FPF)—of dry powder inhaler (DPI) formulations for the therapy of asthma was investigated using an artificial lung, the next generation impactor (NGI). Therefore mixtures with 100%, 50% and 25% calculated surface coverage of physically and chemically modified glass beads as model carrier and spray dried salbutamol sulfate as active pharmaceutical ingredient (API) have been prepared. In any of these cases the actual surface coverage was lower than the calculated surface coverage as a certain amount of API particles adheres to the mixing container wall instead of the glass bead surface. Moreover, API particles detach from the glass bead surface during capsule filling and transport resulting in even lower true surface coverage at the moment when the NGI experiments are performed. When investigating the FPF this true surface coverage has to be taken into account. The FPF increased more or less linearly with increasing surface coverage of the surface modified glass beads but the slopes of the lines are different depending of the carriers used. This can be attributed to the distribution of active sites on the glass bead surface that is individually depending on the surface modification applied and the processing time. However the influence of surface coverage on FPF is also influenced by the choice of the carrier particles. Compared to untreated glass beads physically modified glass beads show increased FPFs whereas chemically modified glass beads show lower FPFs.

Miniaturized bead-beating device to automate full DNA sample preparation processes for Gram-positive bacteria

We have developed a miniaturized bead-beating device to automate nucleic acids extraction from Gram-positive bacteria for molecular diagnostics. The microfluidic device was fabricated by sandwiching a monolithic flexible polydimethylsiloxane (PDMS) membrane between two glass wafers (i.e., glass-PDMS-glass), which acted as an actuator for bead collision via its pneumatic vibration without additional lysis equipment. The Gram-positive bacteria, S. aureus and methicillin-resistant S. aureus, were captured on surface-modified glass beads from 1 mL of initial sample solution and in situ lyzed by bead-beating operation. Then, 10 μL or 20 μL of bacterial DNA solution was eluted and amplified successfully by real-time PCR. It was found that liquid volume fraction played a crucial role in determining the cell lysis efficiency in a confined chamber by facilitating membrane deflection and bead motion. The miniaturized bead-beating operation disrupted most of S. aureus within 3 min, which turned out to be as efficient as the conventional benchtop vortexing machine or the enzyme-based lysis technique. The effective cell concentration was significantly enhanced with the reduction of initial sample volume by 50 or 100 times. Combination of such analyte enrichment and in situ bead-beating lysis provided an excellent PCR detection sensitivity amounting to ca. 46 CFU even for the Gram-positive bacteria. The proposed bead-beating microdevice is potentially useful as a nucleic acid extraction method toward a PCR-based sample-to-answer system.

Glass bead grafting with poly(carboxylic acid) polymers and maleic anhydride copolymers

AbstractGlass beads were etched with acids and bases to increase the surface porosity and the number of silanol groups that could be used for grafting materials to the surfaces. The pretreated glass beads were functionalized using 3‐aminopropyltriethoxysilane (APS) coupling agent and then further chemically modified by reacting the carboxyl groups of carboxylic acid polymers with the amino groups of the pregrafted APS. Several carboxylic acid polymers and poly(maleic anhydride) copolymers, such as poly(acrylic acid) (PAA), poly(methacrylic acid) (PMA), poly(styrene‐alt‐maleic anhydride) (PSMA), and poly(ethylene‐alt‐maleic anhydride) (PEMA) were grafted onto the bead surface. The chemical modifications were investigated and characterized by FT‐IR spectroscopy, particle size analysis, and tensiometry for contact angle and porosity changes. The amount of APS and the different polymer grafted on the surface was determined from thermal gravimetric analysis and elemental analysis data. Spectroscopic studies and elemental analysis data showed that carboxylic acid polymers and maleic anhydride copolymers were chemically attached to the glass bead surface. The improved surface properties of surface modified glass beads were determined by measuring water and hexane penetration rates and contact angle. Contact angles increased and porosity decreased as the molecular weights of the polymer increased. The contact angles increased with the hydrophobicity of the attached polymer. The surface morphology was examined by scanning electron microscopy (SEM) and showed an increase in roughness for etched glass beads. Copyright © 2007 John Wiley & Sons, Ltd.

Compression of Langmuir Films Composed of Fine Particles: Collapse Mechanism and Wettability

The collapse mechanism of microparticulate Langmuir films was studied experimentally in the present work. Using a Wilhelmy film balance, surface pressure vs area isotherms were determined, and the particle removal during the compression was examined by video-microscope and by naked eye. Upon compressing partially wettable 75 microm diameter surface modified glass beads at liquid (water or aqueous surfactant solution)-air (or n-octane) interfaces, different collapse mechanisms were visualized depending on the wettability of the particles. At low contact angles (below 40 degrees ) irreversible particle removal was observed as a consequence of a particulate line-by-line collapse mechanism. At higher contact angles a buckling-type collapse mechanism was revealed without particle removal from the liquid interface. In the case of irreversible particle removal we assessed the contact angles from the nondissipative part of the isotherm. These values were found to be in reasonable agreement with those determined directly on the beads.

Surface modification of glass beads with poly(acrylic acid)

Non-porous P2 glass beads were etched with sodium hydroxide to increase the number of silanol groups that could be used to modify the surface. The etched glass beads were then functionalized with 3-aminopropyltriethoxysilane (APS) and/or glycidoxypropyltrimethoxysilane (GPS). The surface of the glass beads were further modified with poly(acrylic acid) (PAA) by reacting the carboxyl groups on PAA with the amino groups of the pregrafted APS. The chemical modifications were characterized by FT-IR spectroscopy, particle size analyzer and tensiometry for contact angle and porosity measurements. Five different molecular weight PAA polymers ranging from 2000 to 3,000,000 were grafted with less than expected increase of grafted PAA with molecular weight. The amount of APS and PAA on the surface was determined from thermogravimetric analysis and elemental analysis data. The surface properties of the surface modified glass beads were determined by measuring water and hexane penetration rate and contact angle. The surface morphology was examined by scanning electron microscopy. Copyright © 2006 John Wiley & Sons, Ltd.

Effects of surface modification of glass beads with poly(acrylic acid)

Etched glass beads were functionalized with 3-aminopropyltriethoxysilane (APS) and glycidoxypropyltrimethoxysilane (GPS). The surface of glass beads were further modified with poly(acrylic acid) by reacting the carboxyl groups on poly(acrylic acid) with the amino groups of the grafted aminopropyltriethoxysilane. The modifications were characterized by FT-IR spectroscopy and tensiometry for contact angle and porosity measurements. Five different molecular weight PAA polymers ranging from 2,000 to 3,000,000 were grafted with less than expected increase of grafting% with molecular weight. The amount of poly(acrylic acid) (PAA) on the surface was determined from thermal gravimetric analysis and elemental analysis data. The surface properties of surface modified glass beads were determined by measuring water and hexane penetration rate and contact angle. The surface morphology was examined by scanning electron microscopy.

On the universal growth of two-dimensional aggregates of hydrophobed glass beads formed at the (aqueous solution of electrolyte)—air interfaces

Two-dimensional aggregation of surface-modified glass beads was carried out at water (aqueous solution of electrolyte)—air interfaces. The effects of particle hydrophobicity and electrolyte concentration on the structure of the forming aggregates and on the growth process were investigated. The growth was characterized by density functions which demonstrate the change in mean particle number density as a function of aggregate size. The aggregation yielded fractal or non-fractal structures, depending on aggregate size. The fractal character for small aggregates was found to be dependent on particle hydrophobicity as well as on electrolyte concentration. However, above a certain electrolyte concentration, where restructuring of the growing aggregates was hindered slightly, practically the same values of fractal dimensions were obtained for investigated systems having different hydrophobicities. This result was attributed to the universal aspect of two-dimensional growth.

INTERFACIAL AGGREGATION OF FLOATING MICROPARTICLES UNDER THE CONTROL OF SHORT-RANGE COLLOID AND VERY LONG-RANGE CAPILLARY FORCES

Interfacial aggregation of surface modified glass beads (62–74 μm diameter) at water/air interface was carried out by using two differently hydrophobic samples, respectively. The effect of aggregation time on the self-similar structure of forming aggregates was studied comparing the actual results to those obtained previously.1 The time dependence of restructuring from the point of view of fractal geometry has been proved but the results call attention to another time dependent process— orientation of growing clusters during their collisions due to anisotropy of cluster-cluster interactions.

On the structure formation of hydrophobed particles in the boundary layer of water and octane phases

Two-dimensional aggregation of the surface modified glass beads was carried out in the boundary layer of water and octane phases. The effect of particles' hydrophobicity was investigated on the structure of forming aggregates and the growth process. The structure of the aggregates and their growth were characterized by a density function which demonstrates the change of mean particle density as a function of aggregate size. The growth yielded fractal or nonfractal structures in the investigated systems. The fractal structure of the aggregates was observed to be dependent on restructuring processes controlled by the surface properties of the beads.

Experimental study of the aggregate structures formed in the boundary layer of water—air phases

Two-dimensional aggregation of surface-modified glass beads was carried out in the boundary layer of water—air phases. The effect of the hydrophobicity of the beads on the structure of forming aggregates and on the growth process was investigated. The structure of the aggregates and their growth were characterized by a density function which expresses the change of mean density of the aggregates as a function of size. The growth yielded fractal or non-fractal structures in the systems studied. The fractal structure of the aggregates was dependent on restructuring processes controlled by the surface properties of the beads.

Effect of interface on the mechanical behaviour of glass bead-filled PVC

The surface of glass beads of average particle size 100μm was modified (a) by incorporating extra hydroxyl groups by chemcial treatment, and (b) by applying a thin coating of polymethacrylic acid (PMA) on the glass surface. The corresponding chemical changes were investigated using infrared spectroscopy. The tensile behaviour of a glass bead-filled PVC composite prepared with surface-modified glass beads, showed the following effects: (a) hydroxyl groups incorporated on to the glass surface did not affect the glass-PVC interface and hence did not change the tensile behaviour of the composite; (b) PMA coating on the glass surface caused improvement in the tensile behaviour in the low strain region and deterioration in the high region. An SEM study of the fractured surface suggested debonding at the glass-PVC interface in the first case, and failure of the PVC-PMA interface in the second case.