Polystyrene Microparticles Research Articles

Dielectrophoresis-enabled surface enhanced Raman scattering on gold-decorated polystyrene microparticle in micro-optofluidic devices for high-sensitive detection

We have developed a method to fabricate higher order surface enhanced Raman scattering (SERS) active structure with gold-decorated polystyrene microparticles (Au/PS microparticles) to serve a wide range of applications in life science and environmental analysis using alternating-current dielectrophoresis (DEP). It is within several tens of seconds to form or gather the SERS—active ‘hot spots’ and analyte. The immobilization of Au/PS microparticles can be demonstrated and qualitatively explained by DLVO and DEP calculation. Our method enables us to detect 4, 4′-bipyridine (4bpy) at 100pM by an easy operation of in situ SERS platform using fiber-type simple Raman spectrometer. This platform can easily generate SERS-active ‘hot spots’ with SERS enhancement factor ∼108 in specific region on demand.

Microparticles manipulation and enhancement of their separation in pinched flow fractionation by insulator-based dielectrophoresis.

The separation and manipulation of microparticles in lab on a chip devices have importance in point of care diagnostic tools and analytical applications. The separation and sorting of particles from biological and clinical samples can be performed using active and passive techniques. In passive techniques, no external force is applied while in active techniques by applying external force (e.g. electrical), higher separation efficiency is obtained. In this article, passive (pinched flow fractionation) and active (insulator-based dielectrophoresis) methods were combined to increase the separation efficiency at lower voltages. First by simulation, appropriate values of geometry and applied voltages for better focusing, separation, and lower Joule heating were obtained. Separation of 1.5 and 6μm polystyrene microparticles was experimentally obtained at optimized geometry and low total applied voltage (25V). Also, the trajectory of 1.5μm microparticles was controlled by adjusting the total applied voltage.

Oyster reproduction is affected by exposure to polystyrene microplastics.

Plastics are persistent synthetic polymers that accumulate as waste in the marine environment. Microplastic (MP) particles are derived from the breakdown of larger debris or can enter the environment as microscopic fragments. Because filter-feeder organisms ingest MP while feeding, they are likely to be impacted by MP pollution. To assess the impact of polystyrene microspheres (micro-PS) on the physiology of the Pacific oyster, adult oysters were experimentally exposed to virgin micro-PS (2 and 6 µm in diameter; 0.023 mg·L(-1)) for 2 mo during a reproductive cycle. Effects were investigated on ecophysiological parameters; cellular, transcriptomic, and proteomic responses; fecundity; and offspring development. Oysters preferentially ingested the 6-µm micro-PS over the 2-µm-diameter particles. Consumption of microalgae and absorption efficiency were significantly higher in exposed oysters, suggesting compensatory and physical effects on both digestive parameters. After 2 mo, exposed oysters had significant decreases in oocyte number (-38%), diameter (-5%), and sperm velocity (-23%). The D-larval yield and larval development of offspring derived from exposed parents decreased by 41% and 18%, respectively, compared with control offspring. Dynamic energy budget modeling, supported by transcriptomic profiles, suggested a significant shift of energy allocation from reproduction to structural growth, and elevated maintenance costs in exposed oysters, which is thought to be caused by interference with energy uptake. Molecular signatures of endocrine disruption were also revealed, but no endocrine disruptors were found in the biological samples. This study provides evidence that micro-PS cause feeding modifications and reproductive disruption in oysters, with significant impacts on offspring.

Fabrication and characterization of polyelectrolyte microcarriers for microorganism cultivation through a microfluidic droplet system

This study experimentally investigates the generation of polyelectrolyte droplets, and subsequently, cured microcarriers for application in microorganism cultivation. Microcarriers containing an mature microorganism culture can replace in situ biofilms in microfluidic bioprocesses to reduce the startup duration and facilitate the replenishment of functional microorganisms. This study examines the effects of particulate solutes (polystyrene (PS) microparticles, Chlorella vulgaris, and Escherichia coli) on polyelectrolyte solution properties (zeta potential, contact angle, and interfacial tension) and droplet/microcarrier formation. The results indicated that, except for interfacial tension and shear stress, the colloidal stability and morphology of particulate solutes should also be considered when generating droplets. A particulate solute resulting in a dispersed phase with colloidal stability was beneficial for the predictable droplet generation. A particulate solute increasing the affinity between the disperse phase and the channel wall hastened the droplet generation to shift from the dripping region to the jetting region. Adding particulate solutes with consistent size and morphology into the dispersed phase was less likely to affect the droplet formation and the droplet size. In this study, adding PS microparticles and C. vulgaris into a diallyldimethylammonium chloride (DDA) solution resulted in a more hydrophilic solution and higher interfacial tension compared with adding DDA solution alone. These particulate solutes also tended to cause incipient colloidal instability. The incipient instability of the C. vulgaris solution led to various droplet sizes. However, the droplet sizes of the PS microparticle solution, which had solution properties similar to those of the C. vulgaris solution, were more uniform because of the consistent size and morphology of PS microparticles. Adding moderate amounts of E. coli resulted in a more hydrophobic solution, lower interfacial tension, and satisfactory colloidal stability. The droplets containing microorganisms were cured to generate poly-DDA (PDDA) microcarriers, and E. coli cultivated in PDDA microcarriers had the same viability as those cultivated in suspension. However, C. vulgaris cultivated in PDDA microcarriers failed to proliferate possibly due to the blockage of the nutrient intake by the quaternary ammonium cation of DDA.

Acoustofluidic coating of particles and cells.

On-chip microparticle and cell coating technologies enable a myriad of applications in chemistry, engineering, and medicine. Current microfluidic coating technologies often rely on magnetic labeling and concurrent deflection of particles across laminar streams of chemicals. Herein, we introduce an acoustofluidic approach for microparticle and cell coating by implementing tilted-angle standing surface acoustic waves (taSSAWs) into microchannels with multiple inlets. The primary acoustic radiation force generated by the taSSAW field was exploited in order to migrate the particles across the microchannel through multiple laminar streams, which contained the buffer and coating chemicals. We demonstrate effective coating of polystyrene microparticles and HeLa cells without the need for magnetic labelling. We characterized the coated particles and HeLa cells with fluorescence microscopy and scanning electron microscopy. Our acoustofluidic-based particle and cell coating method is label-free, biocompatible, and simple. It can be useful in the on-chip manufacturing of many functional particles and cells.

Destruction of a spherical polystyrene microparticle in pulsed ultraviolet beam for micromanipulation purpose

The modelling of heating a spherical polystyrene microparticle by the laser beam having the wavelength 355 nm and varying spot size is described. The simulation results are presented for two different values of the beam spot radius. Nature experiments are reported aimed at measuring the velocity of a particle with the radius 5µm accelerated by microexplosion of the neighbouring particle.

Ingestion of microplastics by Mediterranean mussel (Mytilus galloprovincialis): Influence of particle size on histopathological and oxidative stress responses

Event Abstract Back to Event Ingestion of microplastics by Mediterranean mussel (Mytilus galloprovincialis): Influence of particle size on histopathological and oxidative stress responses Cátia Gonçalves1*, Marta G. Martins1, Paula Sobral1 and Maria Helena Costa1 1 Marine and Environmental Sciences Centre, Faculdade de Ciências e Tecnologia - Universidade Nova de Lisboa, Departamento de Ciências e Engenharia do Ambiente, Portugal Plastic debris is ubiquitous in the marine environments due to its intrinsic properties (e.g. buoyancy) and the growing dependence on plastic consumption all over the world . Due to their small size, microplastics have become a potential threat to the marine biota. Ingestion of microplastics has previously demonstrated in several marine organisms, from zooplankton to bivalve and fish. Although some organisms have the ability to excrete the ingested microplastics, the potential effects at organ and tissue level are poorly studied, especially considering different microplastic sizes. The present work evaluates the potential effects and responses of ingested microplastics by the Mediterranean mussel (Mytilus galloprovincialis) and their relationship with the ingestion rate and residence time of microplastics in the organism. For this purpose, mussels were exposed to three different polystyrene microparticles sizes (2um, 6um, 10um), in single and combined environmentally-relevant concentrations (10 and 1000 particles.mL-1), under controlled laboratory conditions. The ingestion rate and residence time of microplastics were calculated taking account the density and particle size data analysed by Coulter counter assay. Histopathological alterations and oxidative stress biomarkers (e.g. lipid peroxidation, total glutathione, catalase and glutathione S–transferase activity) were assessed in gills and digestive gland. The results showed distinct ingestion rates and residence time of each assayed tested microplastics. Although histopathological analyses revealed the presence of microparticles, tissue alterations were not severe. In general, oxidative responses were directly related with microparticles size. These results stress the importance of considering distinct microplastic size, for they generate distinct effects to this marine organism, implying potential effects in the marine food web. Keywords: microplastic uptake, Mediterranean mussel, Oxidative Stress biomarkers, Plastic debris, Ecotoxicology Conference: IMMR | International Meeting on Marine Research 2016, Peniche, Portugal, 14 Jul - 15 Jul, 2016. Presentation Type: Poster presentation Topic: Biodiversity, Conservation and Coastal Management Citation: Gonçalves C, Martins MG, Sobral P and Costa M (2016). Ingestion of microplastics by Mediterranean mussel (Mytilus galloprovincialis): Influence of particle size on histopathological and oxidative stress responses. Front. Mar. Sci. Conference Abstract: IMMR | International Meeting on Marine Research 2016. doi: 10.3389/conf.FMARS.2016.04.00080 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 30 Apr 2016; Published Online: 13 Jul 2016. * Correspondence: Ms. Cátia Gonçalves, Marine and Environmental Sciences Centre, Faculdade de Ciências e Tecnologia - Universidade Nova de Lisboa, Departamento de Ciências e Engenharia do Ambiente, Caparica, Portugal, cv.goncalves@campus.fct.unl.pt Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Cátia Gonçalves Marta G Martins Paula Sobral Maria Helena Costa Google Cátia Gonçalves Marta G Martins Paula Sobral Maria Helena Costa Google Scholar Cátia Gonçalves Marta G Martins Paula Sobral Maria Helena Costa PubMed Cátia Gonçalves Marta G Martins Paula Sobral Maria Helena Costa Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Acoustofluidic particle manipulation inside a sessile droplet: four distinct regimes of particle concentration.

In this study, we have investigated the motion of polystyrene microparticles inside a sessile droplet of water actuated by surface acoustic waves (SAWs), which produce an acoustic streaming flow (ASF) and impart an acoustic radiation force (ARF) on the particles. We have categorized four distinct regimes (R1-R4) of particle aggregation that depend on the particle diameter, the SAW frequency, the acoustic wave field (travelling or standing), the acoustic waves' attenuation length, and the droplet volume. The particles are concentrated at the centre of the droplet in the form of a bead (R1), around the periphery of the droplet in the form of a ring (R2), at the side of the droplet in the form of an isolated island (R3), and close to the centre of the droplet in the form of a smaller ring (R4). The ASF-based drag force, the travelling or standing SAW-based ARF, and the centrifugal force are utilized in various combinations to produce these distinct regimes. For simplicity, we fixed the fluid volume at 5 μL, varied the SAW actuation frequency (10, 20, 80, and 133 MHz), and tested several particle diameters in the range 1-30 μm to explicitly demonstrate the regimes R1-R4. We have further demonstrated the separation of particles (1 and 10 μm, 3 and 5 μm) using mixed regime configurations (R1 and R2, R2 and R4, respectively).

Enhancement of microfluidic particle separation using cross-flow filters with hydrodynamic focusing.

A microfluidic chip is proposed to separate microparticles using cross-flow filtration enhanced with hydrodynamic focusing. By exploiting a buffer flow from the side, the microparticles in the sample flow are pushed on one side of the microchannels, lining up to pass through the filters. Meanwhile a larger pressure gradient in the filters is obtained to enhance separation efficiency. Compared with the traditional cross-flow filtration, our proposed mechanism has the buffer flow to create a moving virtual boundary for the sample flow to actively push all the particles to reach the filters for separation. It further allows higher flow rates. The device only requires soft lithograph fabrication to create microchannels and a novel pressurized bonding technique to make high-aspect-ratio filtration structures. A mixture of polystyrene microparticles with 2.7 μm and 10.6 μm diameters are successfully separated. 96.2 ± 2.8% of the large particle are recovered with a purity of 97.9 ± 0.5%, while 97.5 ± 0.4% of the small particle are depleted with a purity of 99.2 ± 0.4% at a sample throughput of 10 μl/min. The experiment is also conducted to show the feasibility of this mechanism to separate biological cells with the sample solutions of spiked PC3 cells in whole blood. By virtue of its high separation efficiency, our device offers a label-free separation technique and potential integration with other components, thereby serving as a promising tool for continuous cell filtration and analysis applications.

Bubble-Pen Lithography.

Current lithography techniques, which employ photon, electron, or ion beams to induce chemical or physical reactions for micro/nano-fabrication, have remained challenging in patterning chemically synthesized colloidal particles, which are emerging as building blocks for functional devices. Herein, we develop a new technique - bubble-pen lithography (BPL) - to pattern colloidal particles on substrates using optically controlled microbubbles. Briefly, a single laser beam generates a microbubble at the interface of colloidal suspension and a plasmonic substrate via plasmon-enhanced photothermal effects. The microbubble captures and immobilizes the colloidal particles on the substrate through coordinated actions of Marangoni convection, surface tension, gas pressure, and substrate adhesion. Through directing the laser beam to move the microbubble, we create arbitrary single-particle patterns and particle assemblies with different resolutions and architectures. Furthermore, we have applied BPL to pattern CdSe/ZnS quantum dots on plasmonic substrates and polystyrene (PS) microparticles on two-dimensional (2D) atomic-layer materials. With the low-power operation, arbitrary patterning and applicability to general colloidal particles, BPL will find a wide range of applications in microelectronics, nanophotonics, and nanomedicine.

Study of the performance of a membrane-based vacuum drying process

Abstract The possibility of applying vacuum membrane distillation for drying polystyrene microparticles was recently confirmed and the best membrane unit design, named Vacuum Membrane Dryer (VMDr), identified. However, some limits in the production efficiency were underlined. Therefore, in the present work, further investigations to improve the performance of the previously developed and selected unit were carried out. In particular, the effect of mixing and air bubbling was analyzed. Moreover, the efficiency of the VMDr as function of the particles size, the membrane area and the membrane properties was studied.

Microfluidic Flow Rate Detection With a Large Dynamic Range by Optical Manipulation

Sensitive flow rate detection with a large dynamic range is highly desirable for the lab-on-a-chip applications. We demonstrate an optofluidic flow rate detection method based on the optical manipulation of a single microparticle by a cleaved single-mode fiber (SMF). The microbalance between the optical force and the flow force on the single polystyrene microparticle was used as a new strategy for the detection. Due to the inverse sensitivity, the limit of detection is pushed down to 20 nL/min by detecting the manipulation length as a function of the flow rate. The measurement range of about three orders of magnitude is achieved. The experimental results indicate that the method produces a good repeatability for the flow rate measurement. The cleaved SMF for the optofluidic manipulation also enables low cost, repeatable, and mass production of the sensing device.

Micromotors Powered by Enzyme Catalysis.

Active biocompatible systems are of great current interest for their possible applications in drug or antidote delivery at specific locations. Herein, we report the synthesis and study of self-propelled microparticles powered by enzymatic reactions and their directed movement in substrate concentration gradient. Polystyrene microparticles were functionalized with the enzymes urease and catalase using a biotin-streptavidin linkage procedure. The motion of the enzyme-coated particles was studied in the presence of the respective substrates, using optical microscopy and dynamic light scattering analysis. The diffusion of the particles was found to increase in a substrate concentration dependent manner. The directed chemotactic movement of these enzyme-powered motors up the substrate gradient was studied using three-inlet microfluidic channel architecture.

Enhanced Optical Manipulation of Cells Using Antireflection Coated Microparticles

We demonstrate the use of antireflection (AR) coated microparticles for the enhanced optical manipulation of cells. Specifically, we incubate CHO-K1, HL60, and NMuMG cell lines with AR-coated titania microparticles and subsequently performed drag force measurements using optical trapping. Direct comparisons were performed between native, polystyrene microparticle and AR microparticle tagged cells. The optical trapping efficiency was recorded by measuring the Q value in a drag force experiment. CHO-K1 cells incubated with AR microparticles show an increase in the Q value of nearly 220% versus native cells. With the inclusion of AR microparticles, cell velocities exceeding 50 μm/s were recorded for only 33 mW of laser trapping power. Cell viability was confirmed with fluorescent dyes and cells expressing a fluorescent ubiquitination-based cell cycle protein (FUCCI), which verified no disruption to the cell cycle in the presence of AR microparticles.

Fabrication of dielectrophoretic microfluidic chips using a facile screen-printing technique for microparticle trapping

Trapping of microparticles finds wide applications in numerous fields. Microfluidic chips based on a dielectrophoresis (DEP) technique hold several advantages for trapping microparticles, such as fast result processing, a small amount of sample required, high spatial resolution, and high accuracy of target selection. There is an unmet need to develop DEP microfluidic chips on different substrates for different applications in a low cost, facile, and rapid way. This study develops a new facile method based on a screen-printing technique for fabrication of electrodes of DEP chips on three types of substrates (i.e. polymethyl-methacrylate (PMMA), poly(ethylene terephthalate) and A4 paper). The fabricated PMMA-based DEP microfluidic chip was selected as an example and successfully used to trap and align polystyrene microparticles in a suspension and cardiac fibroblasts in a cell culture solution. The developed electrode fabrication method is compatible with different kinds of DEP substrates, which could expand the future application field of DEP microfluidic chips, including new forms of point-of care diagnostics and trapping circulating tumor cells.

Mechanism of immunoglobulin G adsorption on polystyrene microspheres

The adsorption of polyclonal immunoglobulin G (IgG) on negatively charged polystyrene microparticle suspension (latex) was studied by using the Laser Doppler Velocimetry (LDV) measurements. Using this technique, the dependence of the electrophoretic mobility of particles on the IgG concentration in the suspension was measured for various ionic strengths and pH 3.5. The increase in the electrophoretic mobility was quantitatively interpreted in terms of the 3D electrokinetic model. On the other hand, the maximum coverage of IgG on latex was determined using the depletion method based on AFM imaging. It was shown that IgG adsorption was irreversible and that its maximum coverage on the microspheres increased from 1.4mgm−2 for 0.001M NaCl to 2.0mgm−2 for 0.15M NaCl. This was interpreted in terms of reduced electrostatic repulsion among adsorbed molecules. The stability of IgG monolayers on the particles was confirmed in separate experiments where changes in its electrophoretic mobility were monitored over prolonged time periods. Additionally, the acid-base properties of the IgG monolayers on latex were determined in pH cycling experiments. The isoelectric point of the IgG monolayers on the microspheres was 4.8. The results obtained in this work indicate that basic physicochemical characteristics of IgG can be acquired via electrophoretic mobility measurements using microgram quantities of the protein.

Faraday rotation imaging microscope with microsecond pulse magnet

We have fabricated a high-performance Faraday rotation (FR) imaging microscope that uses a microsecond pulse magnet comprising an insulated gated bipolar transistor and a 2μF capacitor. Our microscope produced images with greater stability and sensitivity than those of previous microscopes that used millisecond pulse magnet; these improvements are likely due to high repetition rate and negligible Joule heating effects. The mechanical vibrations in the magnet coil caused by the pulsed current were significantly reduced. The present FR microscope constructed an averaged image from 1000 FR images within 10min under 1.7T. Applications of the FR microscope to discriminating three benzene derivatives in micro-capillaries and oscillation-free imaging of spherical polystyrene and polymethyl methacrylate microparticles demonstrated its high performance.

EXPERIMENTAL STUDIES OF SURFACE-DRIVEN CAPILLARY FLOW IN PMMA MICROFLUIDIC DEVICES PREPARED BY DIRECT BONDING TECHNIQUE AND PASSIVE SEPARATION OF MICROPARTICLES IN MICROFLUIDIC LABORATORY-ON-A-CHIP SYSTEMS

Proper bonding technique is investigated to achieve leakage-free surface-driven capillary flow in polymethylmethacrylate (PMMA) microfluidic devices. SU-8-based silicon stamp is fabricated by maskless lithography. This stamp is used to produce PMMA microchannel structure by hot embossing lithography. A direct bonding technique is mainly employed for leakage-free sealing inside PMMA microfluidic devices. The effect of surface wettability on surface-driven capillary flow is also investigated in PMMA microfluidic devices. The separation of polystyrene microparticles in PMMA laboratory-on-a-chip systems is investigated with the reduction of separation time by air dielectric barrier discharge (DBD) plasma processing of channel surfaces. This study is useful to fabricate the microfluidic laboratory-on-a-chip systems and to understand the surface-driven capillary flow.

Surface modification of microparticles causes differential uptake responses in normal and tumoral human breast epithelial cells.

The use of micro- and nanodevices as multifunctional systems for biomedical applications has experienced an exponential growth during the past decades. Although a large number of studies have focused on the design and fabrication of new micro- and nanosystems capable of developing multiple functions, a deeper understanding of their interaction with cells is required. In the present study, we evaluated the effect of different microparticle surfaces on their interaction with normal and tumoral human breast epithelial cell lines. For this, AlexaFluor488 IgG functionalized polystyrene microparticles (3 μm) were coated with Polyethyleneimine (PEI) at two different molecular weights, 25 and 750 kDa. The effect of microparticle surface properties on cytotoxicity, cellular uptake and endocytic pathways were assessed for both normal and tumoral cell lines. Results showed a differential response between the two cell lines regarding uptake efficiency and mechanisms of endocytosis, highlighting the potential role of microparticle surface tunning for specific cell targeting.

Non-linear optical flow cytometry using a scanned, Bessel beam light-sheet.

Modern flow cytometry instruments have become vital tools for high-throughput analysis of single cells. However, as issues with the cellular labeling techniques often used in flow cytometry have become more of a concern, the development of label-free modalities for cellular analysis is increasingly desired. Non-linear optical phenomena (NLO) are of growing interest for label-free analysis because of the ability to measure the intrinsic optical response of biomolecules found in cells. We demonstrate that a light-sheet consisting of a scanned Bessel beam is an optimal excitation geometry for efficiently generating NLO signals in a microfluidic environment. The balance of photon density and cross-sectional area provided by the light-sheet allowed significantly larger two-photon fluorescence intensities to be measured in a model polystyrene microparticle system compared to measurements made using other excitation focal geometries, including a relaxed Gaussian excitation beam often used in conventional flow cytometers.