Fluorescent Polystyrene Research Articles

Analysis of the Distinct Pattern Formation of Globular Proteins in the Presence of Micro- and Nanoparticles.

Pattern formation during evaporation of biofluids has numerous biomedical applications, e.g., in disease identification. The drying of a bidisperse colloidal droplet involves formation of coffee ring patterns owing to the deposition of constituent particles. In the present study, we examine the distinctly different pattern formations during the drying of a colloidal solution depending on the nature of the constituent proteins. The pattern formations of two oppositely charged proteins, namely HSA and lysozyme, have been studied in the presence of fluorescence polystyrene beads of two different sizes (providing better image contrast for further analysis). The variation of pattern formation has been studied by varying the concentrations of the proteins as well as the particles. Furthermore, using image analysis, the patterns are segmented into different regions for quantification. To explain the variations in the patterns, we delve into the interplay of the interactions, especially the capillary and the DLVO forces (between the particles and the substrate). The developed methodology based on the coffee ring effect may be used to identify individual proteins.

Up and away: ontogenic transference as a pathway for aerial dispersal of microplastics.

Microplastics (MPs) are ubiquitous pollutants found in marine, freshwater and terrestrial ecosystems. With so many MPs in aquatic systems, it is inevitable that they will be ingested by aquatic organisms and be transferred up through the food chain. However, to date, no study has considered whether MPs can be transmitted by means of ontogenic transference, i.e. between life stages that use different habitats. Here, we determine whether fluorescent polystyrene beads could transfer between Culex mosquito life stages and, particularly, could move into the flying adult stage. We show for the first time that MPs can be transferred ontogenically from a feeding (larva) into a non-feeding (pupa) life stage and subsequently into the adult terrestrial life stage. However, transference is dependent on particle size, with smaller 2 µm MPs transferring readily into pupae and adult stages, while 15 µm MPs transferred at a significantly reduced rate. MPs appear to accumulate in the Malpighian tubule renal excretion system. The transfer of MPs to the adults represents a potential aerial pathway to contamination of new environments. Thus, any organism that feeds on terrestrial life phases of freshwater insects could be impacted by MPs found in aquatic ecosystems.

Impacts of polystyrene microplastic on the gut barrier, microbiota and metabolism of mice

Microplastics (MPs), which are new environmental pollutants with a diameter of <5 mm, have received wide attention in recent years. However, there are still very limited data regarding the risks of MPs to animals, especially higher mammals. In this study, we exposed male mice to 5 μm pristine and fluorescent polystyrene MP for six weeks. The results showed that the polystyrene MP was observed in the guts of mice and could reduce the intestinal mucus secretion and cause damage the intestinal barrier function. In addition, high-throughput sequencing of the V3-V4 region of the 16S rRNA gene was used to explore the change of the gut microbiota composition in the cecal content. At the phylum level, the content of Actinobacteria decreased significantly in the polystyrene MP-treated group. The PD whole-tree indexes of the alpha diversity and principal component analysis (PCA) of the beta diversity indicated that the diversity of gut microbiota was altered after polystyrene MP exposure. At the genus level, a total of 15 types of bacteria changed significantly after exposure to polystyrene MP. Furthermore, the predicted KEGG (Kyoto Encyclopedia of Genes and Genomes) metabolic pathway differences indicated that the main metabolic pathways of the functional genes in the microbial community were significantly influenced by the polystyrene MP. In addition, indexes of amino acid metabolism and bile acid metabolism in the serum were analyzed after polystyrene MP exposure. These results indicated that polystyrene MP caused metabolic disorders. In conclusion, the polystyrene MP induced gut microbiota dysbiosis, intestinal barrier dysfunction and metabolic disorders in mice. This study provided more data on the toxicity of MPs in a terrestrial organism to aid in the assessment of the health risks of polystyrene MP to animals.

Magnetically amplified photothermal therapies and multimodal imaging with magneto-plasmonic nanodomes

Nanotherapies require new ways for controlling and improving the delivery of the therapeutic agents to the site of action to maximize their efficacy and minimize the side effects. This control is particularly relevant in photothermal treatments to reduce the required light intensity and amount of injected nanoparticles, and to minimize necrotic cell deaths. Here we present a novel concept for multifunctional nanobiomedical agents: magneto-plasmonic (MP) nanodomes for magnetically guided and amplified photothermal therapies and as contrast agents for multimodal imaging. The MP nanodomes are composed of a Fe/Au bilayer semi-shell deposited on a 100nm diameter fluorescent polystyrene nanosphere, which gather a unique combination of straightforward functionalization, high colloidal stability, very strong ferromagnetic behavior and intense optical absorption efficiency in the near infrared. We show that the photothermal conversion efficiency of the Fe/Au nanodomes with high Fe ratios is substantially larger than pure plasmonic Au nanodomes and the state-of-art plasmonic nanoheaters, i.e. Au nanorods and nanoshells, by merging strong optical absorption, minimized scattering and low optical anisotropy. Remarkably, the effective magnetophoretic concentration of the Fe/Au nanodomes at the illumination region enables large local increase of the optically induced temperature rise. The Fe semishell also provides very intense T2 contrast in nuclear magnetic resonance, which is at least 15-fold larger per particle than commercial iron oxide contrast agents. Moreover, the fluorescent polystyrene nanosphere and the Au semishell integrate valuable fluorescent and X-ray contrasts, respectively, which we have used to assess the nanodomes internalization by cancer cells. The MP nanodomes are nontoxic to cells even in the case of magnetophoretic local enrichment with initially high particle concentration (100μg/mL). Remarkably, we demonstrate amplified local photothermal treatments by the magnetic enrichment of the nanodomes at the illumination region, which enables reaching nearly 100% reduction of cell viability with low particle concentration (10μg/mL) and mild NIR laser intensity (5W/cm2). These results highlight the high potential of MP nanodomes for magnetically guided and amplified photothermal therapies.

Direct measurement of selective evaporation of binary mixture droplets by dissolving materials

We investigate experimentally and theoretically how a droplet of a binary mixture evaporates when placed on a solid substrate. Our focus is the limit at which the two liquid components have different vapour pressures. Using physicochemical effects, we directly visualize the selective evaporation of the more volatile component and so document the space and time dependence of the chemical distribution in the droplet. In particular, we observe that a mixture consisting of an organic solvent and deionized water dissolves suspended fluorescent polystyrene particles if the lower volatility organic solvent reaches a critical concentration. Consequently, we show that for a small contact angle ($\unicode[STIX]{x1D703}&lt;\unicode[STIX]{x03C0}/2$) the suspended polystyrene particles begin to disappear from near the contact line, which indicates that the volatile component, here water, evaporates rapidly compared to the other component(s). Finally, we show that a diffusion-dominated model for evaporation of a binary mixture can predict well the experimental results where convective and diffusive mixing effects are negligible, in which case there is significant chemical segregation in the drop.

Enhanced Detection of Single Viruses On-Chip via Hydrodynamic Focusing.

Planar optofluidics provide a powerful tool for facilitating chip-scale light-matter interactions. Silicon-based liquid core waveguides have been shown to offer single molecule sensitivity for efficient detection of bioparticles. Recently, a PDMS based planar optofluidic platform was introduced that opens the way to rapid development and prototyping of unique structures, taking advantage of the positive attributes of silicon dioxide-based optofluidics and PDMS based microfluidics. Here, hydrodynamic focusing is integrated into a PDMS based optofluidic chip to enhance the detection of single H1N1 viruses on-chip. Chip-plane focusing is provided by a system of microfluidic channels to force the particles towards a region of high optical collection efficiency. Focusing is demonstrated and enhanced detection is quantified using fluorescent polystyrene beads where the coefficient of variation is found to decrease by a factor of 4 with the addition of hydrodynamic focusing. The mean signal amplitude of fluorescently tagged single H1N1 viruses is found to increase with the addition of focusing by a factor of 1.64.

Flow cytometric analysis of extracellular vesicle subsets in plasma: impact of swarm by particles of non‐interest

Background Extracellular vesicles (EVs) in plasma are increasingly being recognized as potential biomarkers. EV analysis for diagnostic purposes should be robust and should allow analysis of EV subsets with a wide range of abundance and in a large number of patient samples. Flow cytometry offers possibilities to meet these criteria, as it allows multiparameter analysis of individual EVs. However, analysis of plasma EVs is challenging, because of their size and heterogeneity, and the presence of other submicrometer-sized particles in plasma that could interfere with EV analysis. Objectives To explore whether fluorescence-based flow cytometric analysis of EV subsets is suitable when the EVs of interest are present in low abundance in a background of non-labeled or differently labeled EVs and particles. Methods Fluorescently labeled EVs of interest were spiked at different ratios in full plasma, purified plasma components, or (non-)fluorescent polystyrene beads, and subsequently analyzed by flow cytometry with fluorescence threshold triggering. Results We found that light scatter detection of low-abundance or rare EV subsets during fluorescence threshold triggering was severely affected by particles of non-interest, owing to coincidence and swarming. Importantly, we show that interfering particles labeled with different fluorophores induced false-positive fluorescent signals on the particles of interest. These unwanted effects could only be discerned and controlled by performing serial dilutions and analyzing light scatter and fluorescence parameters. Conclusions We demonstrate how particles of non-interest in plasma can impact on the light scatter and fluorescence detection of low-abundance EVs of interest during fluorescence-based flow cytometric analysis, and provide a means to prevent erroneous data interpretation.

Preparation and characterization of functional near ultraviolet fluoresent microspheres

The polymerisable fluorescent monomer, allyl carbazole, was synthesized from carbazole and characterized using FT-IR spectra, 1H NMR and fluorescence spectra. Using allyl carbazole as fluorescent dye, carboxyl polystyrene fluoresent microspheres, polyacrylamide fluorescent microspheres and polystyrene fluoresent microspheres with sulfonic groups with narrow particle size were prepared by dispersion polymerization. These fluorescent microspheres were characterized by SEM, fluorescence microscopy, FT-IR spectroscopy, the conductivity, fluorescence spectrophotometry and UV-vis spectrometer. The results indicated that the three kinds of fluorescent microspheres with good dispersion and stability and high blue fluorescence intensity were obtained. And carboxyl groups, sulfonic groups and amino groups were successfully introduced on the surface, whose contents were approximately 45, 90 and 60 μmol g−1, respectively. Furthermore, the characteristics of allyl carbazole should be maintained in the fluorescent microspheres, the difference of the spectra between fluorescent microspheres and allyl carbazole in ethanol and toluene were also proved.

Inertial focusing of microparticles in curvilinear microchannels with different curvature angles

Inertial microfluidics has become one of the emerging topics due to potential applications such as particle separation, particle enrichment, rapid detection and diagnosis of circulating tumor cells. To realize its integration to such applications, underlying physics should be well understood. This study focuses on particle dynamics in curvilinear channels with different curvature angles (280°, 230°, and 180°) and different channel heights (90, 75, and 60 µm) where the advantages of hydrodynamic forces were exploited. We presented the cruciality of the three-dimensional particle position with respect to inertial lift forces and Dean drag force by examining the focusing behavior of 20 µm (large), 15 µm (medium) and 10 µm (small) fluorescent polystyrene microparticles for a wide range of flow rates (400–2700 µL/min) and corresponding channel Reynolds numbers. Migration of the particles in lateral direction and their equilibrium positions were investigated in detail. In addition, in the light of our findings, we described two different regions: transition region, where the inner wall becomes the outer wall and vice versa, and the outlet region. The maximum distance between the tight particle stream of 20 and 15 µm particles was obtained in the 90 high channel with curvature angle of 280° at Reynolds number of 144 in the transition region (intersection of the turns), which was the optimum condition/configuration for focusing.

A novel method for measuring flotation recovery by means of 4D particle tracking velocimetry

This work focuses on analysing the collection process in flotation by means of a simultaneous time-resolved measurement of particle and bubble trajectories. We introduced a new method that determined the probability of collision and attachment using a 3D particle-tracking method with high temporal resolution (1000 fps) and spatial (0.03 mm/pixel) resolution in a dense particle flow (5000 particles/ml). A 4D particle image tracking device with three high-speed cameras recorded the three-phase flow in a rectangular bubble column (2 mm, bubble chain). Particles made of fluorescent polystyrene were employed so that particles appeared bright and bubbles dark on the captured images. An attachment occurred if the trajectory of a particle coincided with that of a bubble. The recovery was calculated based on the number of particles attached to a bubble compared to the total number of particles within a reference volume. With this method, the true flotation depending on the particle diameter (30–100 μm) was investigated and the results compared with an existing model of the bubble-particle collection microprocess.

Preparation of Swellable Hydrogel-Containing Colloidosomes from Aqueous Two-Phase Pickering Emulsion Droplets.

The fabrication of stable colloidosomes derived from water-in-water Pickering-like emulsions are described that were produced by addition of fluorescent amine-modified polystyrene latex beads to an aqueous two-phase system consisting of dextran-enriched droplets dispersed in a PEG-enriched continuous phase. Addition of polyacrylic acid followed by carbodiimide-induced crosslinking with dextran produces hydrogelled droplets capable of reversible swelling and selective molecular uptake and exclusion. Colloidosomes produced specifically in all-water systems could offer new opportunities in microencapsulation and the bottom-up construction of synthetic protocells.

Inherently fluorescent polystyrene microspheres as a fluorescent probe for highly sensitive determination of chromium (VI) and mercury (II) ions

Nowadays developing fluorescent probes that are cheaper, nontoxic, robust and easy to use for determination of heavy metal ions with high selectivity and sensitivity is still an ongoing challenge. In this paper, inherently fluorescent aminated polystyrene microspheres (PS-NH2) were fabricated from cross-linked polystyrene (PS) microspheres through acetylation, oximation and reduction, which can serve as a selective and sensitive fluorescence (FL) probe for the determination of chromium (VI) (Cr(VI)) and mercury (II) (Hg2+) ions. The photostability, selectivity and sensitivity of the fluorescent PS-NH2 microspheres were studied in detail. The feasibility of PS-NH2 microspheres as a fluorescent probe was conducted by determining Cr(VI) or Hg2+ in real water samples. Results revealed that no photoleaching or leaking issues were observed on PS-NH2 microspheres. The fluorescent probe could analyze Cr(VI) and Hg2+ separately in water samples with high sensitivity and good accuracy in the range of 0.01–1 μM. The detection limits for Cr(VI) and Hg2+ were 9.1 nM and 9.9 nM, respectively. Additionally, two possible FL quenching mechanisms were proposed for Cr(VI) and Hg2+. This work provides a new platform for accurate determination of Cr(VI) and Hg2+ in environmental fields.

Sorption of fluorescent polystyrene microplastic particles to edible seaweed Fucus vesiculosus

Increased global demands for food have raised interest for seaweed as a healthy and sustainable food source. At the same time, the large amounts of microplastic in the oceans have raised concern in relation to pollution of seafood including sea vegetables. The aim of this study was to examine sorption of fluorescent polystyrene (PS) microplastic particles to edible macroalga (seaweed) Fucus vesiculosus, and to investigate to what extent adsorbed PS particles could be washed off, using an industrial relevant method. PS microplastic particles (diameter of 20 μm) were used in a concentration of 2.65 mg L−1 (corresponding to 597 particles per mL) in filtrated seawater (50 mL) to treat F. vesiculosus distal tips in blue cap flasks (100 mL) placed in a rotary box for 2 h. Results showed sorption of PS microplastic particles to F. vesiculosus analysed by microscopy and a significant reduction of 94.5% by washing. These results were based on high microplastic concentrations, not comparable to natural conditions/concentrations. Nonetheless, this study provides methodological and mechanistic insights into procedures for investigating the sorption of microplastics to seaweed, for which there is currently no established standardised method.

Comparison of six digestion methods on fluorescent intensity and morphology of the fluorescent polystyrene beads

Effect of digestion methods on fluorescence intensity of fluorescent polystyrene (PS) beads was poorly understood, which may affect the accuracy of toxicity test of the fluorescent PS beads exposed to marine organisms. Therefore, six digestion approaches were compared on fluorescence intensities and properties of three commercial fluorescent PS beads. Among all the protocols, the digestion using KOH (10% w/v, 60 °C) (KOH-digestion) had no effect on the fluorescence intensity, morphology and composition of the three fluorescent PS beads. Moreover, the extraction efficiency ≥ 95.3 ± 0.2% of fluorescent PS beads in Daphnia magna and zebrafish, confirming its feasibility in fluorescent PS beads quantitative analysis. However, the fluorescence intensities of fluorescent PS beads digested by other five protocols were significantly decreased, as well as the change of morphology and composition on fluorescent PS beads. Overall, the KOH-digestion is an optimal protocol for extracting fluorescent PS beads in biological samples.

Simultaneous detection of tumor markers in human serum using time-resolved fluorescence microspheres immunochromatographic assay

Objective To develop a time-resolved fluorescent microspheres immunochromatographic assay (TRFMIA) for detection of alphafetoprotein (AFP) and carcinoembryonic antigen (CEA) in human serum and to evaluate its performance. Methods The Eu-time-resolved fluorescent polystyrene particles conjugated with monoclonal antibody AC18# for AFP and AE03# for CEA were used as fluorescent labels. The monoclonal antibody AC17# for AFP, AE05# for CEA and goat anti-rabbit antibody were immobilized on the nitrocellulose membrane as the test lines and control line. Several performances indicators were measured, including linear range, detection limit, and specificity. AFP and CEA were measured by the new method and the results were compared with those obtained by time-resolved fluoroimmunoassay (TRFIA) and electro-chemiluminescence immunoassay (ECLIA) using linear correlation analysis. Results The measurement ranges of AFP were 0.07-1 000.00 kU/L with the intra- and inter-assay CV of 5.93% and 11.07%, and those of CEA were 0.12-500.00 μg/L with the intra- and inter-assay CV of 7.53% and 12.13% respectively. The average recovery rate of AFP and CEA was 92.77% and 94.73%, respectively. Measurements obtained by TRFMIA had strong correlation coefficients ranging from 0.93 to 0.97 when compared with those obtained by TRFIA and ECLIA. Conclusion TRFMIA, which can simultaneously detect AFP and CEA, has been successfully established. Key words: Alpha-fetoproteins; Carcinoembryonic antigen; Fluoroimmunoassay; Chemiluminescent measurements

Massively parallel approximate Bayesian computation for estimating nanoparticle diffusion coefficients, sizes and concentrations using confocal laser scanning microscopy.

We implement a massively parallel population Monte Carlo approximate Bayesian computation (PMC-ABC) method for estimating diffusion coefficients, sizes and concentrations of diffusing nanoparticles in liquid suspension using confocal laser scanning microscopy and particle tracking. The method is based on the joint probability distribution of diffusion coefficients and the time spent by a particle inside a detection region where particles are tracked. We present freely available central processing unit (CPU) and graphics processing unit (GPU) versions of the analysis software, and we apply the method to characterize mono- and bidisperse samples of fluorescent polystyrene beads.

Near wall void growth leads to disintegration of colloidal bacterial streamer

We investigated the failure of thick bacterial floc-mediated streamers in a microfluidic device with micropillars. It was found that streamers could fail due to the growth of voids in the biomass that originate near the pillar walls. The quantification of void growth was made possible by the use of 200 nm fluorescent polystyrene beads. The beads get trapped in the extracellular matrix of the streamer biomass and acted as tracers. Void growth time-scales could be characterized into short-time scales and long time-scales and the crack/void propagation showed several instances of fracture-arrest ultimately leading to a catastrophic failure of the entire streamer structure. This mode of fracture stands in strong contrast to necking-type instability observed before in streamers.

Identifying Potential Provider and Environmental Contamination on a Clinical Biocontainment Unit Using Aerosolized Pathogen Simulants.

The Johns Hopkins Hospital created a biocontainment unit (BCU) to care for patients with highly infectious diseases while assuring healthcare worker safety. Research to date for BCU protocols and practices are based on case reports and lessons learned from patient care and exercises. This study seeks to be the first to explore the influences of healthcare worker movement and personal protective equipment (PPE) doffing on the transport of simulant pathogen particles in a BCU. A cough device released 1 μm fluorescent polystyrene beads (PSLs) in the patient room. PSL transport was then examined under 2 scenarios: (1) PSL release only, no healthcare workers; and (2) PSL release during 5-minute simulated activity by healthcare workers. Airborne PSL concentrations were quantified every second for 30 minutes per scenario by 7 optical particle sensors located throughout the BCU. PSLs were not detected in the donning room at any time nor in the doffing room during the first test scenario where no healthcare worker was present. The main difference detected between the tested scenarios was the presence of PSLs in the doffing room when healthcare workers were removing PPE, potentially due to re-aerosolization of PSLs off the exterior PPE surface or opening of the patient room door. Future work will further explore the potential for re-aerosolization of particles off of PPE during doffing. The present study provides the groundwork for a systematic method for evaluating the BCU and doffing procedures for their respective safety, and it also pilots a systematic method for evaluating potential pathogen exposure pathways for BCU healthcare workers.

Three-dimensional particle behavior using defocusing method in micro-toroidal vortex generated by optoelectrokinetic flow

This paper demonstrates a technique to realize multiphysics simulation and experimental validation of micro-toroidal vortex and utilizing the defocusing method to obtain the three-dimensional particles trajectory using a single camera. Fluorescent polystyrene particles were suspended at a concentration of 3.7 × 108 count mL−1 solution diluted with DI water. These were carried by the toroidal vortex fluid motion and showed an optoelectrokinetic phenomenon. We used a defocusing method to trace the three-dimensional trajectory of the particles. The size of the ring pattern increased as particles moved far away from the focusing plane and close to the objective lens. By recording the ring pattern size of one particle in every continuous frame, we successfully implemented the described techniques to obtain the three-dimensional trajectory of particles in an optoelectrokinetic experiment. Simulation results in COMSOL® Multiphysics (v4.3a) were compared to the trajectory and particle velocity variation in the experiment.

Spectroscopic identification of individual fluorophores using photoluminescence excitation spectra.

The identity of a fluorophore can be ambiguous if other fluorophores or nonspecific fluorescent impurities have overlapping emission spectra. The presence of overlapping spectra makes it difficult to differentiate fluorescent species using discrete detection channels and unmixing of spectra. The unique absorption and emission signatures of fluorophores provide an opportunity for spectroscopic identification. However, absorption spectroscopy may be affected by scattering, whereas fluorescence emission spectroscopy suffers from signal loss by gratings or other dispersive optics. Photoluminescence excitation spectra, where excitation is varied and emission is detected at a fixed wavelength, allows hyperspectral imaging with a single emission filter for high signal-to-background ratio without any moving optics on the emission side. We report a high throughput method for measuring the photoluminescence excitation spectra of individual fluorophores using a tunable supercontinuum laser and prism-type total internal reflection fluorescence microscope. We used the system to measure and sort the photoluminescence excitation spectra of individual Alexa dyes, fluorescent nanodiamonds (FNDs), and fluorescent polystyrene beads. We used a Gaussian mixture model with maximum likelihood estimation to objectively separate the spectra. Finally, we spectroscopically identified different species of fluorescent nanodiamonds with overlapping spectra and characterized the heterogeneity of fluorescent nanodiamonds of varying size.