Standard Polystyrene Research Articles

Identification of Trace Polystyrene Nanoplastics Down to 50 nm by the Hyphenated Method of Filtration and Surface-Enhanced Raman Spectroscopy Based on Silver Nanowire Membranes.

Nanoplastics are emerging pollutants that pose potential threats to the environment and organisms. However, in-depth research on nanoplastics has been hindered by the absence of feasible and reliable analytical methods, particularly for trace nanoplastics. Herein, we propose a hyphenated method involving membrane filtration and surface-enhanced Raman spectroscopy (SERS) to analyze trace nanoplastics in water. In this method, a bifunctional Ag nanowire membrane was employed to enrich nanoplastics and enhance their Raman spectra in situ, which omitted sample transfer and avoided losing smaller nanoplastics. Good retention rates (86.7% for 50 nm and approximately 95.0% for 100-1000 nm) and high sensitivity (down to 10-7 g/L for 50-1000 nm and up to 105 SERS enhancement factor) of standard polystyrene (PS) nanoplastics were achieved using the proposed method. PS nanoplastics with concentrations from 10-1 to 10-7 g/L and sizes ranging from 50 to 1000 nm were successfully detected by Raman mapping. Moreover, PS micro- and nanoplastics in environmental water samples collected from the seafood market were also detected at the μg/L level. Consequently, the proposed method provides more possibilities for analyzing low-concentration nanoplastics in aquatic environments with high enrichment efficiency, minimal sample loss, and high sensitivity.

Accurate 3D morphological computational model reconstruction of suspended cells imaged through stratified media by the precise depth-varying point spread function method.

Accurate three-dimensional (3D) morphological computational models of cells are important in a number of biological studies. This study proposes a precise depth-varying point spread function (PDV-PSF) method for reconstructing 3D computational models of suspended cells from two-dimensional (2D) confocal image stacks. Our approach deblurs the 2D images in horizontal plane and corrects the deformation in vertical direction to overcome the refractive index mismatch problem caused by suspended cells imaging through stratified media. Standard fluorescent polystyrene spheres and Jurkat T-lymphocytes are selected to evaluate the validity and accuracy of this PDV-PSF method. Qualitative and quantitative results demonstrate that our approach has superior performance in 3D morphological computational models reconstruction of suspended cells.

Metal-Catalyzed, Photo-Assisted Selective Transformation of Tertiary Alkylbenzenes and Polystyrenes into Carbonyl Compounds.

Every year, thousands of tons of polystyrene are produced and discarded, filling landfills and polluting the marine environment. Although several degradation alternatives have been proposed, the need for an effective procedure for the chemical recycling of polystyrene still remains. Here, a vanadium‐catalyzed reaction, assisted by visible light, promoted the direct, selective conversion of tertiary alkylbenzenes into acetophenone and other ketone derivatives. Likewise, standard polystyrene samples as well as polystyrenes from insulation and packaging waste could be chemically recycled into acetophenone in a scalable way regardless of their molecular weight, polydispersity, or form. Preliminary mechanistic investigations revealed the participation of singlet oxygen, superoxide, and hydroxyl radical species in this homogenously catalyzed process. Acetophenone could be used as an additive to accelerate the reaction and to increase the yields in some cases.

Towards a fast and generalized microplastic quantification method in soil using terahertz spectroscopy

Extensive investigation of microplastic abundance in soil environment calls for rapid, accurate, efficient and harmonized quantification methods. Development of rapid quantification method requires made-to-measure soil samples with additions of standard polymers. Existing rapid quantification methods ignore the gap between standard polymers in laboratory and household microplastics in soil environment. Here, terahertz (0.6–1.67 thz) and NIR (950–1660 nm) spectroscopy were compared to explore a fast, accurate and potentially generalizable microplastic quantification method in soil. Soil sample was spiked with two standard polymers (polyvinyl chloride (PVC) and polystyrene (PS)) and their additive-containing household microplastics. Two standard sample sets and two household sample sets were prepared in concentrations ranging from 0.5 to 10%. Nine commonly used preprocessing methods and three machine learning algorithms were coupled to develop methods. Models were constructed by training sets from standard sample sets. When models transferred to household samples, prediction error (RMSE) of proposed terahertz method (Wdenosie_PLSR) only increased by 0.4% for PVC and 0.19% for PS, yet that of the NIR method increased by 1.49% and 1.16% respectively. The proposed terahertz method presented a detection limit around 1.12% and the NIR method showed a detection limit around 3.24%. Overall, our results suggest that compared with NIR method, the proposed terahertz method is not only more accurate but also demonstrate stronger generalizability to bridge the gaps between standard PVC/PS polymers and household PVC/PS microplastics. We also propose MMD heatmap for diagnosing spectral preprocessing methods to further improve method efficiency.

Generation of Greater Bacterial Biofilm Biomass using PCR-Plate Deep Well Microplate Devices

Bacterial biofilms are difficult to eradicate from surfaces using conventional antimicrobial interventions. High-throughput 96-well microplate methods are frequently used to cultivate bacterial biofilms for rapid antimicrobial susceptibility testing to calculate minimal biofilm eradication concentration (MBEC) values. Standard biofilm devices consist of polystyrene pegged-lids fitted to 96-well microplates and are ideal for measuring biofilm biomass and MBEC values, but these devices are limited by available peg surface area for biomass accumulation and cost. Here, we outline a protocol to use self-assembled polypropylene 96-well deep well PCR-plate pegged-lid device to grow Escherichia coli BW25113 and Pseudomonas aeruginosa PAO1 biofilms. A comparison of 24-hour biofilms formed on standard and deep well devices by each species using crystal violet biomass staining and MBEC determination assays are described. The larger surface area of deep well devices expectedly increased overall biofilm formation by both species 2-4-fold. P. aeruginosa formed significantly greater biomass/mm2 on deep well pegs as compared to the standard device. E. coli had greater biomass/mm2 on standard polystyrene devices as compared the deep well device. Biofilm eradication assays with disinfectants such as sodium hypochlorite (bleach) or benzalkonium chloride (BZK) showed that both compounds could eliminate E. coli and P. aeruginosa biofilms from both devices but at different MBEC values. BZK biofilm eradication resulted in variable E. coli MBEC values between devices, however, bleach demonstrated reproducible MBEC values for both species and devices. This study provides a high throughput deep well method for growing larger quantities of biofilms on polypropylene devices for downstream studies requiring higher amounts of static biofilm.

Generation of Greater Bacterial Biofilm Biomass using PCR-Plate Deep Well Microplate Devices.

Bacterial biofilms are difficult to eradicate from surfaces using conventional antimicrobial interventions. High-throughput 96-well microplate methods are frequently used to cultivate bacterial biofilms for rapid antimicrobial susceptibility testing to calculate minimal biofilm eradication concentration (MBEC) values. Standard biofilm devices consist of polystyrene pegged-lids fitted to 96-well microplates and are ideal for measuring biofilm biomass and MBEC values, but these devices are limited by available peg surface area for biomass accumulation and cost. Here, we outline a protocol to use self-assembled polypropylene 96-well deep well PCR-plate pegged-lid device to grow Escherichia coli BW25113 and Pseudomonas aeruginosa PAO1 biofilms. A comparison of 24-hour biofilms formed on standard and deep well devices by each species using crystal violet biomass staining and MBEC determination assays are described. The larger surface area of deep well devices expectedly increased overall biofilm formation by both species 2-4-fold. P. aeruginosa formed significantly greater biomass/mm2 on deep well pegs as compared to the standard device. E. coli had greater biomass/mm2 on standard polystyrene devices as compared the deep well device. Biofilm eradication assays with disinfectants such as sodium hypochlorite (bleach) or benzalkonium chloride (BZK) showed that both compounds could eliminate E. coli and P. aeruginosa biofilms from both devices but at different MBEC values. BZK biofilm eradication resulted in variable E. coli MBEC values between devices, however, bleach demonstrated reproducible MBEC values for both species and devices. This study provides a high throughput deep well method for growing larger quantities of biofilms on polypropylene devices for downstream studies requiring higher amounts of static biofilm.

Single-Shot Common-Path Off-Axis Dual-Wavelength Digital Holographic Microscopy Based on Two-Dimensional Grating Diffraction

We present a single-shot dual-wavelength common-path off-axis digital holographic microscopic (CO-DHM) imaging method based on two-dimensional grating diffraction. This method improves the utilization rate of the interference field under the limited photosensitive size of the camera, and further expands the original camera’s field of view (FOV). In addition, the mode of orthogonal carrier frequencies close to the diagonal direction can optimize the utilization of the camera’s spatial bandwidth. Compared with the traditional dual-wavelength CO-DHM using one-dimensional grating or prism beam splitting, this method effectively avoids the aliasing of high-frequency components of the +1-order spectrum of different wavelengths in the frequency domain. We provide quantitative phase imaging experiments for the full FOV of USAF resolution chart, onion epidermal cells and standard polystyrene beads. The results prove that the system can enlarge the interferometric FOV by nearly 74.0% without changing the imaging parameters, such as magnification and resolution, and can achieve high-precision quantitative phase imaging with only a single hologram.

Dual-wavelength extinction rainbow refractometry for in-situ characterization of colloidal droplets

Considerable interest and demand exists in multi-parameter characterization of colloidal droplets. However, an optical in-situ characterization of such droplets is a particular challenge due to its heterogeneous and multi-scale nature, motivating the investigation of a dual-wavelength extinction rainbow refractometry. An analytical model is proposed, in which dual-wavelength extinction effect of the inclusions on the amplitude of the primary rainbow peak allows measurement of inclusion concentration and particle size. The rainbow pattern itself yields the refractive index and diameter of the host droplet. Validation experiments using deionized monodisperse water droplets containing standard polystyrene nanoparticles with different concentrations (0%, 0.1%, 0.2%, 0.3%) and particle sizes (210 nm, 530 nm) were conducted. Measured refractive indices and droplet diameters agree well with the known values. Measurement errors of inclusion concentration and size were analyzed with and without a prior knowledge of the inclusion size. Measurement limits of this approach are also discussed.

Geometry Optimalization of the Ventilated Insulating Panel

Abstract An EPS ventilated panel, which may be applied as an external insulation to humid walls, is investigated. Dimensions of the air channel sections have been determined using the Ansys software. Afterwards, the drying rate of the walls externally insulated with EPS, mineral wool and EPS ventilated panel has been compared using the WUFI software. The ventilated panel increases the drying rate when compared with the standard polystyrene panel and increases the heat loss through the wall by less than 20%.

A Novel Method for 3D Nanoscale Tracking of 100 nm Polystyrene Particles in Multi-Wavelength Evanescent Fields Microscopy – Absolute Difference Height Verification –

Total internal reflection is an optical imaging technique for nanoparticle tracking and observation employing the scattered light from an evanescent field near the interface or reference surface. Generally, the nanoparticle behavior is the three-dimensional Brownian motion in an aqueous medium. The motion can be traced by an optical microscopy, but it cannot be traced by an electron microscopy technique. In the three-dimensional nanoparticle moving position, the X and Y positions are parallel to the surface, which can be traced by the general microscopy techniques. However, the height position Z of a nanoparticle perpendicular to the surface could not be traced without the longitudinal scanning method. Here, a novel method is proposed to investigate the 3D position of nanoparticles by applying multi-wavelength evanescent fields microscopy, which has a high spatial resolution in the Z-direction without longitudinal scanning. This paper focuses on the verification of measurement in the Z-direction. A piezoelectric actuator was employed to control the nanoparticle displacement in height Z. Standard polystyrene 100 nm particles were randomly adhered on a spherical tip that connected with the piezoelectric actuator. The spherical tip was essentially made from an optical adhesive (n = 1.348) with a refractive index close to the water for decreasing the unnecessary signal from the tip-self during nanoparticle observation in the water. The proposed method could obtain the multi-wavelength scattering lights from the observed nanoparticles by an 8-bit color camera with higher than 50 frames per second recording to investigate the 3D nanoscale tracking. The X and Y positions of nanoparticles were determined by the centroid of the scattering light intensities. The height Z was determined from the logarithm ratios between the detected scattering light intensities of both wavelengths. The measurement repeatability of the absolute difference in height between nanoparticles could be measured less than ±16 nm by using the proposed method. The penetration height measurability range was approximated at 250 nm from the reference surface.

Measuring particle size in ultra-low concentration suspensions by removing the number fluctuation contribution in dynamic light scattering.

In ultra-low concentration suspensions, particle number fluctuations in the scattering volume add a long delay component to the intensity autocorrelation function (ACF) in dynamic light scattering (DLS) measurements. This gives a strong artifact peak in the particle size distribution (PSD) recovered. To improve the accuracy of DLS at ultra-low concentrations, we analyzed the different decay characteristics of particle Brownian motion and particle number fluctuation in the ACF. By differentiating the ACF we were able to identify and separate the number fluctuation term and then analyze the ACF to recover the PSD. The results for simulated DLS data at 151nm and 690nm diameters with average particle numbers of 6, 12, 24 and 48 in the scattering volume at four noise levels show that, compared with the usual DLS data processing method, inversion of the ACF after the separation of the number fluctuation term effectively eliminates the strong artifact peaks, and the relative errors of peak positions and distribution errors are significantly reduced. This was further verified with experimental results from samples of standard polystyrene spheres.

In-situ Detection Method for Microplastics in Water by Polarized Light Scattering

Microplastics (MPs) have become the widespread contaminants, which raises concerns on their ecological hazards. In-situ detection of MP in water bodies is essential for clear assessment of the ecological risks of MPs. The present study proposes a method based on polarized light scattering which measures the polarization parameters of the scattered light at 120° to detect MP in water. This method takes the advantage of in-situ measurement of the individual particles and the experimental setup in principle is used. By use of the measured polarization parameters equipped by machine learning, the standard polystyrene (PS) spheres, natural water sample, and lab-cultured microalgae are explicitly discriminated, and MP with different physical and chemical properties can be differentiated. It can also characterize the weathering of different MP and identify the specific type from multiple types of MP. This study explores the capability of the proposed method to detect the physical and chemical properties, weathering state and concentration of MP in water which promises the future application in water quality sensing and monitoring.

Microfluidics on Standard Petri Dishes for Bioscientists.

Few microfluidic devices are used in biomedical labs, despite the obvious potential; reasons given include the devices are rarely made with cell-friendly materials, and liquids are inaccessibly buried behind solid confining walls. An open microfluidic approach is reviewed in which aqueous circuits with almost any imaginable 2D shape are fabricated in minutes on standard polystyrene Petri dishes by reshaping two liquids (cell-culture media plus an immiscible and bioinert fluorocarbon, FC40). Then, the aqueous phase becomes confined by fluid FC40 walls firmly pinned to the dish by interfacial forces. Such walls can be pierced at any point with pipets and liquids added or removed through them, while flows can be driven actively using external pumps or passively by exploiting local differences in Laplace pressure. As walls are robust, permeable to O2 plus CO2 , and transparent, cells are grown in incubators and monitored microscopically as usual. It is hoped that this simple, accessible, and affordable fluid-shaping technology provides bioscientists with an easy entrée into microfluidics.

Sampling, Identification and Characterization of Microplastics Release from Polypropylene Baby Feeding Bottle during Daily Use.

Microplastics (MPs) are becoming a global concern due to the potential risk to human health. Case studies of plastic products (i.e., plastic single-use cups and kettles) indicate that MP release during daily use can be extremely high. Precisely determining the MP release level is a crucial step to identify and quantify the exposure source and assess/control the corresponding risks stemming from this exposure. Though protocols for measuring MP levels in marine or freshwater has been well developed, the conditions experienced by household plastic products can vary widely. Many plastic products are exposed to frequent high temperatures (up to 100 °C) and are cooled back to room temperature during daily use. It is therefore crucial to develop a sampling protocol that mimics the actual daily-use scenario for each particular product. This study focused on widely used polypropylene-based baby feeding bottles to develop a cost-effective protocol for MP release studies of many plastic products. The protocol developed here enables: 1) prevention of the potential contamination during sampling and detection; 2) realistic implementation of daily-use scenarios and accurate collection of the MPs released from baby feeding bottles based on WHO guidelines; and 3) cost-effective chemical determination and physical topography mapping of MPs released from baby feeding bottles. Based on this protocol, the recovery percentage using standard polystyrene MP (diameter of 2 µm) was 92.4-101.2% while the detected size was around 102.2% of the designed size. The protocol detailed here provides a reliable and cost-effective method for MP sample preparation and detection, which can substantially benefit future studies of MP release from plastic products.

Life cycle assessment during packaging of market-sized seabass and meagre: necessary adaptations toward GHG neutrality.

PurposeFish is a delicate and valuable source of protein, and aquaculture is expected to provide the required amount of fish needed at reasonable prices. Packaging is a vital stage to preserve hygiene, quality and freshness of aquaculture products. The purpose of this study was to identify environmental hotspots in farmed seabass and meagre during the packaging stage and to examine scenarios for reducing environmental impacts, aiming at greenhouse gas neutrality.MethodsThe life cycle assessment method was applied for the first time at three packaging plants of farmed seabass and meagre in western Greece, in order to assess their environmental impacts, taking into account the amount of electricity, expanded polystyrene, and other plastic and packaging materials needed. Moreover, different scenarios were designed involving the energy mix/alternative sources, recycling and reuse of packaging materials, and the replacement of standard polystyrene boxes and wooden pallets, in order to suggest environmentally friendly improvements in the packaging process.Results and discussionConventional operation of seabass and meagre packaging plants requires significant amounts of energy and packaging materials. In fact, electricity, boxes and pallets were documented as the main contributors to most of the environmental impact indicators. Seabass packaging had a slightly lower overall environmental impact compared to meagre, due to its smaller market size. Impact minimization scenarios resulted in various degrees of reduction of environmental burdens in both species; however, near-zero GHG emissions were achieved when energy from photovoltaic panels and recycling/reuse of packaging materials were combined with the use of non-fossil-based boxes and recyclable pallets. Such readily applicable adjustments to the conventional operation of packaging plants would contribute to overall environmental sustainability and to better consumer acceptability of the final product.ConclusionsIn a nutshell, the life cycle assessment method proved to be a valuable tool for assessing the environmental performance of Mediterranean aquaculture packaging processes. Moreover, it served to identify critical factors directly related to the EU GHG neutrality target. Accordingly, environmentally friendly decision-making/strategic management in the farmed fish packaging sector will inevitably rely on alternative energy sources, recycling of packaging materials, and use of recyclable corrugated board boxes or similar non-fossil-based materials.

Deep-Learning-Based Halo-Free White-Light Diffraction Phase Imaging

In white-light diffraction phase imaging, when used with insufficient spatial filtering, phase image exhibits object-dependent artifacts, especially around the edges of the object, referred to the well-known halo effect. Here we present a new deep-learning-based approach for recovering halo-free white-light diffraction phase images. The neural network-based method can accurately and rapidly remove the halo artifacts not relying on any priori knowledge. First, the neural network, namely HFDNN (deep neural network for halo free), is designed. Then, the HFDNN is trained by using pairs of the measured phase images, acquired by white-light diffraction phase imaging system, and the true phase images. After the training, the HFDNN takes a measured phase image as input to rapidly correct the halo artifacts and reconstruct an accurate halo-free phase image. We validate the effectiveness and the robustness of the method by correcting the phase images on various samples, including standard polystyrene beads, living red blood cells and monascus spores and hyphaes. In contrast to the existing halo-free methods, the proposed HFDNN method does not rely on the hardware design or does not need iterative computations, providing a new avenue to all halo-free white-light phase imaging techniques.

Isolation and culture of adult murine cardiac atrial and ventricular fibroblasts and myofibroblasts.

Cardiac fibroblasts play a critical role in extracellular matrix homeostasis, wound healing, and cardiac interstitial fibrosis: the latter being a pathophysiological response to a chronic increase in afterload. Using a standard protocol to isolate cardiac fibroblasts and maintain them in their quiescent phenotype in vitro will enable a better understanding of cardiac fibroblast biology and their role in the response to profibrotic stimuli. Here, we describe an enzymatic method for isolating cardiac fibroblasts. The resulting cells are maintained on either a collagen-coated hydrogel-bound polystyrene (compliant) substrate or standard polystyrene culture dishes (non-compliant) to obtain quiescent fibroblasts and activated fibroblasts (myofibroblasts), respectively. Fibroblasts maintained on a non-compliant substrate developed a myofibroblast phenotype, in which the αSMA immunoreactivity was markedly elevated and incorporated into the stress fibers. In contrast, ventricular and atrial fibroblasts retain their quiescent phenotype for up to 3 passages when maintained on a compliant substrate. Hence, the methodology described herein provides a simple and reproducible way to isolate adult murine atrial and ventricular cardiac fibroblasts from a single animal and, by selecting a substrate with the appropriate compliance, examine the mediators of fibroblast activation or inactivation.

EPCL Electrospun Microfibrous Layers for Immune Assays: Sensitive ELISA for the Detection of Serum Antibodies Against HPV16 E7 Oncoprotein.

Human papillomavirus (HPV) type 16 is the etiologic agent of more than 50% anal/cervical cancers and about 20% oropharyngeal cancers. HPV16 E6 and E7 oncogenes favor the transformation and are essential for maintaining the transformed status. Serum anti-E6 and anti-E7 antibodies appear to have prognostic significance for HPV-associated cancers. However, most of the previous attempts to establish diagnostic tools based on serum detection of E6 and/or E7 antibodies have been unsuccessful, mainly due to the low accuracy of applied tests. This paper reports on a feasibility study to prove the possibility to easily immobilize HPV16 E7 onto electrospun substrates for application in diagnostic tools. In this study, poly(ε-caprolactone) electrospun scaffolds (called ePCL) are used to provide a microstructured substrate with a high surface-to-volume ratio, capable of binding E7 proteins when used for enzyme-linked immunosorbent assay (ELISA) tests. ePCL functionalized with E7 exhibited superior properties compared to standard polystyrene plates, increasing the detection signal from serum antibodies by 5-6 times. Analysis of the serum samples from mice immunized with HPV16 E7 DNA vaccine showed higher efficiency of this new anti-E7 ePCL-ELISA test vs control in E7-specific antibody detection. In addition, ePCL-E7-ELISA is prepared with a relatively low amount of antigen, decreasing the manufacturing costs.

Correlative SEM-Raman microscopy to reveal nanoplastics in complex environments

Nowadays “microplastics” (MPs) is an already well-known term and results of micro-sized particles found in consumer products or environments are regularly reported. However, studies of native MPs smaller than 1 μm, often referred to as nanoplastics (NPs), in analytically challenging environments are rare. In this study, a correlative approach between scanning electron microscopy and Raman microscopy is tested to meet the challenges of finding and identifying NPs in the 100 nm range in various environments, ranging from ideal (distilled water) to challenging (sea salt, human amniotic fluid). To test the viability of this approach in principle, standardized polystyrene beads (Ø 200 nm) are mixed into the various environments in different concentrations. Promising detection limits of 2 10−3 μg/L (distilled water), 20 μg/L (sea salt) and 200 μg/L (human amniotic fluid) are found. To test the approach in practices both sea salt and amniotic fluid are analysed for native NPs as well. Interestingly a nylon-NP was found in the amniotic fluid, maybe originating from the sampling device. However, the practical test reveals limitations, especially with regard to the reliable identification of unknown NPs by Raman microscopy, due to strong background signals from the environments. We conclude from this in combination with the excellent performance in distilled water that a combination of this approach with an advanced sample preparation technique would yield a powerful tool for the analysis of NPs in various environments.

Laser Transmission Spectroscopy Based on Tunable-Gain Dual-Channel Dual-Phase LIA for Biological Nanoparticles Characterization.

Size and absolute concentration of suspensions of nanoparticles are important information for the study and development of new materials and products in different industrial applications spanning from biotechnology and pharmaceutics to food preparation and conservation. Laser Transmission Spectroscopy (LTS) is the only methodology able to measure nanoparticle size and concentration by performing a single measurement. In this paper we report on a new variable gain calibration procedure for LTS-based instruments allowing to decrease of an order of magnitude the experimental indetermination of the particle size respect to the conventional LTS based on the double ratio technique. The variable gain calibration procedure makes use of a specifically designed tunable-gain, dual-channel, dual-phase Lock-In Amplifier (LIA) whose input voltage signals are those ones generated by two Si photodiodes that measure the laser beam intensities passing through the sample containing the nanoparticles and a reference optical path. The LTS variable gain calibration procedure has been validated by firstly using a suspension of NIST standard polystyrene nanoparticles even 36 hours after the calibration procedure was accomplished. The paper reports in detail the LIA implementation describing the design methodologies and the electronic circuits. As a case example of the characterization of biological nanostructures, we demonstrate that a single LTS measurement allowed to determine size density distribution of a population of extracellular vesicles extracted from orange juice (25 nm in size) with the presence of their aggregates having a size of 340 nm and a concentration smaller than 3 orders of magnitude.