Small Beads Research Articles

Immersed boundary method for dynamic simulation of polarizable colloids of arbitrary shape in explicit ion electrolytes.

We develop a computational method for modeling electrostatic interactions of arbitrarily shaped, polarizable objects on colloidal length scales, including colloids/nanoparticles, polymers, and surfactants, dispersed in explicit ion electrolytes and nonionic solvents. Our method computes the nonuniform polarization charge distribution induced in a colloidal particle by both externally applied electric fields and local electric fields arising from other charged objects in the dispersion. This leads to expressions for electrostatic energies, forces, and torques that enable efficient molecular dynamics and Brownian dynamics simulations of colloidal dispersions in electrolytes, which can be harnessed to accurately predict structural and transport properties. We describe an implementation in which colloidal particles are modeled as rigid composites of small spherical beads that tessellate the surface of the particle. The electrostatics calculations are accelerated using a spectrally accurate particle-mesh-Ewald technique implemented on a graphics processing unit and regularized such that the electrostatic calculations are well-defined even for overlapping bodies. We illustrate the effectiveness of this approach with a comprehensive set of calculations: the induced dipole moments and forces for individual, paired, and lattice configurations of spherical colloids in an electric field; the induced dipole moment and torque for anisotropic particles subjected to an electric field; the equilibrium ion distribution in the double layer surrounding charged colloids; the dynamics of charged colloids; and the behavior of ions in the double layer of a polarizable colloid under the influence of an electric field.

Effects of Glass Bead Size on Dissolution Profiles in Flow-through Dissolution Systems (USP 4).

The effects of glass bead size in the conical space of flow-through cells on the dissolution profiles were investigated in a USP apparatus 4. Dissolution tests of disintegrating and non-disintegrating tablets in flow-through dissolution systems were performed using semi-high precision glass beads with diameters ranging from 0.5mm to 1.5mm. Computational fluid dynamics (CFD) was used to evaluate the effect of shear stress from the dissolution media flow. The use of smaller glass beads in a larger cell resulted in a faster dissolution of the model formulations under certain test conditions. The effect on the dissolution was highly dependent on the size of the beads in the top layer, including those in contact with the tablets. The absence of a bead-size effect on the dissolution of an orodispersible tablet in a small cell can be explained by the floating fragments during the test. CFD analysis showed that smaller bead diameters led to greater shear stress on the tablet, which was correlated with the dissolution rate. Hence, fluid flow through the narrow gaps between the small beads generated strong local flows, causing shear stress. The size of the glass beads used in flow-through cells affects the dissolution rate of tablets by altering the shear stress on the tablets in certain cases (e.g., direct deposition of the formulation on glass beads, large cells, and very low flow rates). Thus, glass bead size must be considered for a robust dissolution test in a flow-through cell system.

Engineering a 3D network hydrogel composite membrane with Chitosan/Pluronic F127/bioactive glass for the topical administration of therapeutic agents

The primary aim of designing a topical drug delivery system is to address localized ailments by administering therapeutic agents directly to superficial areas of the body such as skin and open wounds. This study presents the engineering of a three-dimensional (3D) network hydrogel composite membrane comprising chitosan (CS), Pluronic F127 (Pl), and bioactive glass (BG) for the topical administration. In the presence of CS and Pl, glutaraldehyde forms imine bonds (Schiff base linkages) by reacting its aldehyde groups with the amino groups of the polymer chains. The hydrogel structural and chemical properties were characterized using X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR), revealed its unique composition and molecular structure. Field Emission Scanning electron microscopy (FESEM) was employed to image and investigate the morphology of the hydrogel, confirming its interconnected sheet like morphology with small beads structure. The hydrogels demonstrated excellent water retention ability as 32.93 %, further controlled degradation kinetics rate was systematically evaluated up to 14 days, and optimal swelling behavior makes it suitable for prolonged drug delivery applications. Moreover, hemocompatibility and cyto-compatibility assays yielded less than 1.1 % and above 60 %, confirming the hydrogel safety for blood contact and cell viability. Tube inversion tests confirmed its mechanical integrity, while antibacterial assays revealed its efficacy against pathogenic microorganisms. Co-culture studies demonstrated the capability of developed hydrogel to support cell growth and proliferation. In vitro drug release studies clearly reveal that the hydrogel provides a sustainable delivery system for piperacillin-tazobactam, demonstrating superior characteristics indicative of non-Fickian or anomalous diffusion. Furthermore, the membrane exhibited promising hemostatic properties, suggesting its potential for wound healing applications. Overall, this comprehensive strategy highlights the versatility of the engineered 3D network hydrogel composite membrane as a promising platform for delivering therapeutic agents locally in various biomedical applications.

Plant-based marbled salami analogs: Emulsion-loaded microgels embedded within protein-polysaccharide hydrogel matrices

The inherent molecular differences between plant and animal proteins make it challenging to accurately simulate the optical and mechanical properties of real meat products using plant-derived ingredients. Soft matter physics approaches are therefore being employed to direct the assembly of plant proteins, polysaccharides, and lipids into meat-like structures. The main focus of the current study was to use soft matter physics approaches to create plant-based analogs of marbled meat products, such as salami, chorizo, or pepperoni. These products have whitish fatty regions embedded within reddish/brown lean regions. In this study, we mimicked the fatty regions in salami using emulsion-loaded alginate beads and the lean regions using composite hydrogels assembled from potato protein and gellan gum. Initially, the textural attributes of the plant-based lean regions were optimized by varying potato protein type (low or high isoelectric point) and concentration. As expected, the mechanical strength of the lean region analogs increased with increasing protein content and depended on protein type. Introducing alginate beads into the salami analogs had little impact on their textural attributes when measured under compression conditions but decreased their stiffness and fracture stress when measured under tensile conditions. In particular, introducing either small or large beads reduced the stiffness and breaking stress of the salami analogs, which was attributed to the introduction of weak points in the composite hydrogel. Finally, we showed that the appearance and textural attributes of real salami could be mimicked in plant-based salami by optimizing its composition and structure. This research provides valuable insights into methods of better simulating the properties of marbled meat products, like sausages and cold-cut meat products, thereby creating a more sustainable food supply.

The Study of Calcium Chloride Effect on Silver Nanoparticles Capping with Roselle Extract Granule against Aggregatibacter actinomycetemcomitans

Abstract Objectives The primary aim of this research is to investigate the influence of calcium chloride on the synthesis of silver nanoparticles coated with roselle extract and enclosed within alginate and calcium chloride (SNP-Ro-CaCl2) beads, designated as SNP-Ro-CaCl2 beads. Additionally, the study aims to assess their antimicrobial activity. Materials and Methods For the preparation of SNP-Ro-CaCl2 beads, SNPs and alginate gel were mixed, followed by dropping in three different concentrations of CaCl2 solution (1%, 3%, and 5% w/v). The morphological structure of the SNP-Ro-CaCl2 beads was analyzed using a stereoscope and scanning electron microscope (SEM). Over a period of 14 days, the release of SNPs was monitored using ultraviolet-visible (UV-Vis) spectroscopy. Additionally, the activity against Aggregatibacter actinomycetemcomitans was evaluated using the disk diffusion technique. Statistical Analysis The data for this experiment were analyzed using one-way analysis of variance (ANOVA) and Scheffe's method. Results The results revealed that varying concentrations of calcium chloride had distinct crosslinking effects on alginate, resulting in different voids and porosity within the SNP-Ro-CaCl2 beads. In the SNP-Ro-1% CaCl2 beads, the inner element exhibited higher porosity, facilitating faster activation and greater efficiency in releasing SNPs. Regarding activity against A. actinomycetemcomitans after 14 days, SNP-Ro-1% CaCl2 beads showed a larger inhibition zone diameter compared to other concentrations, while no statistically significant difference in the inhibition zone diameter was observed between SNP-Ro-3% CaCl2 and SNP-Ro-5% CaCl2 beads. Additionally, it was observed that the antimicrobial effectiveness diminished after 17 days through testing of the lifetimes of the three concentrations. Conclusions This study developed a method for depositing SNP-Ro into alginate gel and crosslinking it with CaCl2 to produce small beads for the sustained release of SNP-Ro in periodontal lesions. Consequently, the SNP-Ro-CaCl2 beads have the potential to be developed as adjunctive locally delivered antimicrobial agents in periodontal therapy.

Spatio-temporal trends in microplastic presence in the sediments of the River Thames catchment (UK)

This study investigated the spatio-temporal variability of microplastics (MPs) in the sediments of the River Thames (UK) catchment over 30 months (July 2019 – Dec 2021). The average MP concentration was 61 items kg−1 d.w., with fragments <1 mm being dominant and polyethylene (PE) the most common polymer. Adjacent land use influenced MP concentrations and types, with industrial sites showing particularly high levels and a prevalence of small beads and industrial polymers. MP concentrations generally decreased after higher winter flows, likely due to sediment rearrangement or winnowing. This study describes the seasonal concentrations and characteristics of MPs present in sediment from the River Thames catchment, and attempts to identify their likely origin. Further, the study provides new insights into the mobility and fate of MPs in riverine settings under varying flow conditions, which is vital given the predicted increases in flooding under various global heating scenarios.

Turbolysis: A low-cost, small footprint alternative to commercial bead beaters for cell lysis

turboLysis is a novel mechanical cell lysis device that utilizes small beads to efficiently lyse tough cells like Mycobacterium, Saccharomyces, and Arabidopsis. We compared turboLysis to bead beating using the BeadBug 6 for several concentrations of Mycobacterium tuberculosis roughly correlated to the bacterial load commonly seen in patient samples. turboLysis performed similarly to the BeadBug at low bacterial concentrations and outperformed it at high concentrations above 2x105 CFU/ml (p < 0.005). Thus, turboLysis offers good cell lytic performance in a small form factor at a low cost.

Characterization of integrins in cellular immunity of the oriental armyworm, Mythimna separata.

Insect hemocytes eliminate foreign substances from the hemocoel through various immune reactions. Integrins, receptor proteins present on the cell membrane, are formed as a heterodimer from α and β subunits and are known to be involved in various immune reactions. To elucidate the role of integrins in the immunity of the lepidoptera Mythimna separata, genes encoding integrins were screened from the genome, resulting in the identification of eight α and four β integrin genes. The expression levels of the integrin genes did not change in response to the injection of small abiotic beads undergoing phagocytosis in M. separata larvae. However, significant inductions of some integrin gene expressions were observed in hemocytes that formed capsules around large abiotic beads during encapsulation, especially in MysIntα2. Under biotic stimulation, induction of the MysIntα2 was evident after exposures to Gram-negative bacteria (Escherichia coli) and entomopathogenic nematodes (Steinernema carpocapsae), but not to Gram-positive bacteria (Micrococcus luteus). Immunostaining analysis revealed that MysIntα2 was specifically localized to hemocytes surrounding the beads during the encapsulation reaction. Furthermore, the spreading and encapsulation abilities of hemocytes were significantly inhibited by incubation with MysIntα2 antibodies. Suppression of MysIntα2 expression in M. separata larvae by injecting double-stranded RNA also resulted in a decrease in encapsulation activity. Collectively, these results indicate that MysIntα2 plays pivotal roles in the cellular immune response of M. separata, particularly during encapsulation. This likely occurs through the regulation of hemocyte spreading activity, thereby facilitating the formation of multilayered capsules around large invaders.

Synthesis of Carboxymethyl Cellulose from Mangrove Nipah (Nypa fruticans) as Vitamin C Coating for Drug Delivery System

Vitamin C is one of the substances needed by the human body which acts as an antioxidant that effectively overcomes the effects of free radicals that damage cells in the body, but vitamin C has properties that are easily oxidized so that innovation is needed to coat (encapsulate) vitamin C in the form of capsules as a drug delivery system. One polymer that can be used for vitamin C encapsulation is cellulose. The cellulose content can be found in the skin and nipah fruit and then synthesized into carboxymethyl cellulose as a vitamin C coating. The microencapsulation method was carried out by mixing 3 g of carrageenan-CMC mixture with variations in the ratio of 1:0; 1:0.5 and 1:1 (%b/b). The encapsulated small beads were made in 200 mL of 2M KCl-CaCl solution by extrusion technique. The microencapsulant was then drained and continued with the crosslinking stage using Glutaraldehyde (GA) 1%. In this in vitro oral simulation study, the encapsulation ratio that produced the best treatment with the highest percentage of drug solubility in the intestine was the ratio (1:0.5), followed by (1:1) and the smallest (1:0) with percentage values of 15.42; 14.06; and 1.67 percent, respectively.

Prostate Artery Embolization (PAE) with Small Beads for the Treatment of Benign Prostatic Hyperplasia (BPH).

Benign Prostatic Hyperplasia (BPH) is the most frequent cause of Lower Urinary Tract Symptoms (LUTSs) in elderly populations. Minimally invasive treatments of BPH are safe and effective and are gaining popularity among both professionals and patients. Prostate Artery Embolization (PAE) has proven to be effective in Trans-Urethral Resection of the Prostate (TURP) in terms of prostate volume reduction and LUTS relief. PAE entails the selective catheterization of the prostatic artery and later embolization of distal vessels with beads of various calibers. Universal consensus regarding the ideal particle size is yet to be defined. We retrospectively evaluated 24 consecutive patients (median age: 75 years; range: 59-86 years) treated with PAE at our institution from October 2015 to November 2022. Particles of different sizes were employed; 12 patients were treated with 40-120 µm particles, 5 with 100 µm, 5 with 100-300 µm and 2 with 250 µm. Technical success, defined as selective prostate artery catheterization and controlled release of embolizing beads, was achieved in all patients. Removal vs. retention of the urinary catheter at the first post-procedural urological visit was the main clinical objective. No major peri-procedural complications were recorded, with 56% of patients successfully removing the urinary catheter.

Discrete-to-continuum models of pre-stressed cytoskeletal filament networks

We introduce a mathematical model for the mechanical behaviour of the eukaryotic cell cytoskeleton. This discrete model involves a regular array of pre-stressed protein filaments that exhibit resistance to enthalpic stretching, joined at cross-links to form a network. Assuming that the inter-cross-link distance is much shorter than the length scale of the cell, we upscale the discrete force balance to form a continuum system of governing equations and deduce the corresponding macroscopic stress tensor. We use these discrete and continuum models to analyse the imposed displacement of a bead placed in the domain, characterizing the cell rheology through the force–displacement curve. We further derive an analytical approximation to the stress and strain fields in the limit of small bead radius, predicting the net force required to generate a given deformation and elucidating the dependency on the microscale properties of the filaments. We apply these models to networks of the intermediate filament vimentin and demonstrate good agreement between predictions of the discrete, continuum and analytical approaches. In particular, our model predicts that the network stiffness increases sublinearly with the filament pre-stress and scales logarithmically with the bead size.

Studies on Encapsulation of Gas Releasing Agent in Ca-Alginate Beads and Controlled Release Pattern of the Beads

Calcium alginate beads have been used to control release gases and volatile compounds for agricultural applications, drug delivery, waste treatment, and food product enhancement. The release rate of the gas and vapor depends on the diffusion of gas and vapor through the Ca-alginate gel matrix. However, the knowledge about the effect of process variables on the diffusion rate of gas and vapor still needs to be improved. Therefore, this study aims to investigate the effect of alginate concentration, gas release agent concentration, and bead size on the concentration of gas released from Ca-alginate beads. In this study, calcium carbonate was used as the model gas release agent, encapsulated in Ca-alginate beads to release carbon dioxide when the beads reacted with an acetic acid solution. The results showed that the concentration of carbon dioxide released by the beads depended on the bead diameter. The gas release rate was increased when the diameter of the beads was increased. The total amount of gas produced by the large beads was observed to be higher than that of small beads. Compared to small beads, large beads take longer to react completely to produce carbon dioxide gas. It was also found that the amount of carbon dioxide produced by the Ca-alginate beads was inversely proportional to alginate concentration but directly proportional to calcium carbonate concentration. The results indicated that the gas diffusion rate of the Ca-alginate beads can be tailored by adjusting the process variables of the Ca-alginate bead encapsulation process.

Lab on a bead with oscillatory centrifugal microfluidics for fast and complete mixing enables fast and accurate biomedical assays

Rapid mixing and precise timing are key for accurate biomedical assay measurement, particularly when the result is determined as the rate of a reaction: for example rapid immunoassay in which the amount of captured target is kinetically determined; determination of the concentration of an enzyme or enzyme substrate; or as the final stage in any procedure that involves a capture reagent when an enzyme reaction is used as the indicator. Rapid mixing and precise timing are however difficult to achieve in point-of-care devices designed for small sample volumes and fast time to result. By using centrifugal microfluidics and transposing the reaction surface from a chamber to a single mm-scale bead we demonstrate an elegant and easily manufacturable solution. Reagents (which may be, for example, an enzyme, enzyme substrate, antibody or antigen) are immobilised on the surface of a single small bead (typically 1–2 mm in diameter) contained in a cylindrical reaction chamber subjected to periodically changing rotational accelerations which promote both mixing and uniform mass-transfer to the bead surface. The gradient of Euler force across the chamber resulting from rotational acceleration of the disc, dΩdisc/dt, drives circulation of fluid in the chamber. Oscillation of Euler force by oscillation of rotational acceleration with period, T, less than that of the hydrodynamic relaxation time of the fluid, folds the fluid streamlines. Movement of the bead in response to the fluid and the changing rotational acceleration provides a dynamically changing chamber shape, further folding and expanding the fluid. Bead rotation and translation driven by fluid flow and disc motion give uniformity of reaction over the surface. Critical parameters for mixing and reaction uniformity are the ratio of chamber radius to bead radius, rchamber/rbead, and the product Trchamber(dΩdisc/dt), of oscillation period and Euler force gradient across the fluid. We illustrate application of the concept using the reaction of horse radish peroxidase (HRP) immobilised on the bead surface with its substrate tetramethylbenzidine (TMB) in solution. Acceleration from rest to break a hydrophobic valve provided precise timing for TMB contact with the bead. Solution uniformity from reaction on the surface of the bead in volumes 20–50 uL was obtained in times of 2.5 s or less. Accurate measurement of the amount of surface-bound HRP by model fitting to the measured kinetics of colour development at 10 s intervals is demonstrated.

A correlation to calculate time constant of thermocouples

A time constant is the dynamic response time of a thermocouple measuring unsteady flow fields. The measured temperature of a thermocouple is the bead temperature, which is determined by the energy conservation of the bead. Heat transfer of the bead includes convective and radiative heat exchange with the flow, heat conduction with the wires, and surface radiation with the environment. These heat transfer modes affect both the bead temperature and its time constant. The novelty of the paper is to derive a correlation for calculating the time constant of a thermocouple based on the bead energy conservation, covering a wide range of conditions and explicitly reflecting the contribution of surface radiation and conduction. The correlation involves the parameter β related to surface radiation and the parameter cl related to conduction. The correlation for β is obtained by fitting the time constant of small beads in the flows with step change parameters using CFD simulations, while the parameter cl is obtained by fitting the time constant of thermocouples under varying flow conditions using CFD simulations. The relative errors between the calculated time constants with the correlation and those of the CFD simulations are less than 19%. The CFD simulations indicate that the time constants considering radiation and conduction are 33–49% of those considering only the effect of convection for the tested cases. The S type and K type thermocouples were used to measure the standard Hencken flames. By applying current loads and then removing them, the dynamic response curves and the time constants of the thermocouples are obtained. The maximum errors between the calculated time constants with the correlation and the experimental values are less than 10%.

Orbit constraint of a small bead on a rotating large circular hoop in a horizontal plane

Orbit constraint problems can be encountered in mechanical equipment and amusement equipment. Mechanics exercises generally consider the ideal physical model, and the practical problems also consider the influence of friction, which makes the problem more complex and and practical. The problem of the force and oscillation of objects on orbit needs to be deeply discussed. In order to simulate the orbital motion of objects more realistically and help students expand their theoretical mechanics beyond class, we study the orbit constraint of a small bead on a rotating large circular hoop in a horizontal plane about an axis passing through a point on the circumference. The coupling equations followed by the bead on the hoop are derived using Newton’s second law in a planar polar coordinate system and solved by numerical methods. We found that under the action of friction, when the initial angular velocity of the bead is greater than the critical angular velocity, the bead will rotate on the ring, and the number of rotations is related to the initial angular velocity and influenced by the friction coefficient. At different initial angular velocities, the number of oscillations of the bead on the hoop is basically the same and ultimately stops near the fixed point.

PSF-Radon transform algorithm: Measurement of the point-spread function from the Radon transform of the line-spread function.

In this article, we present a new method called point spread function (PSF)-Radon transform algorithm. This algorithm consists on recovering the instrument PSF from the Radon transform (in the line direction axis) of the line spread function (i.e., the image of a line). We present the method and tested with synthetic images, and real images from macro lens camera and microscopy. A stand-alone program along with a tutorial is available, for any interested user, in Martinez (PSF-Radon transform algorithm, standalone program). RESEARCH HIGHLIGHTS: Determining the instrument PSF is a key issue. Precise PSF determinations are mandatory if image improvement is performed numerically by deconvolution. Much less exposure time to achieve the same performance than a measurement of the PSF from a very small bead. Does not require having to adjust the PSF by an analytical function to overcome the noise uncertainties.

Chemical composition based machine learning model to predict defect formation in additive manufacturing

With a goal of exploiting additive manufacturing to improve the manufacturing of existing reactor materials, we developed a chemical composition-based machine learning model to predict the printability of any given alloy in laser powder bed fusion (L-PBF) using experimental data from peer-reviewed literature. We defined printability as the ability to avoid defects like cracking, balling, porosity, and lack of fusion, that are caused by thermal stresses (during solidification or liquation), molten pool disintegration into disconnected small beads or lack of heat input respectively. Our models predict the tendency of balling defect formation and porosity percentage for a given composition, under a given set of processing conditions. To predict the likelihood of balling defect, three models: a random forest classifier, a gradient boost regressor and a neural network were trained on a dataset containing both single and multi principal element alloys. The neural network model showed the highest accuracy of 92.3 % in predicting the balling defect formation. A random forest regressor, gradient boost regressor and neural network were trained and tested on a dataset of various alloys to predict porosity. The random forest regressor showed the best predictions with an R2 score of 0.97. The models also revealed the relative importance of the input descriptors on defect-formation tendency. Of particular significance was the identification of carbon as an important element in determining the occurrence of balling and percent porosity in alloys like steel, as well as being moderately important to the percentage porosity in other alloys as well as steel. Manganese was also identified as a key descriptor for the percentage of porosity in steel and other alloys. Manganese's low thermal conductivity and consistent presence in the dataset is the likely cause for its contribution. Carbon's role is attributable to its relatively high specific heat and high melting temperature. Our model serves as a swift, chemistry-based tool to design experiments and find modified compositions better suited for additive manufacturing.

Dynamic analysis of liquid permeability in the dripping zone of blast furnace and reaction behavior at the slag-coke interface

The dripping zone connects the cohesive zone and the hearth, it is one of the key areas of the blast furnace (BF). This study aims to explore the mechanism of the dripping process in BF. The dripping experiments under different conditions were carried out. Dynamics of liquid permeability in the dripping zone was analyzed, the reaction behavior at the slag-coke interface was investigated, and the consumption of coke in the dripping zone was clarified. The results show that: The retention ratio increases with the increase of Al2O3 content. The increase in retention ratio is related to the viscosity of slag. Once the Al2O3 content in slag increases, Si4+ coordination polymer ions in tetrahedra will be replaced by Al3+ cations, forming a tetrahedral structure of [AlO4]5– tetrahedron. The retention ratio decreases with the increase of FeO content. The dissociation of free oxygen ions (O)2– from FeO increases the concentration of free oxygen ions (O)2– in slag, this reduces the viscosity of slag. The presence of FeO can compensate for the increase in retention ratio caused by Al2O3. The quantitative relationship between retention ratio and Al2O3 content and FeO content in slag is obtained. The reduction reaction of FeO occurs at the slag-coke interface, the molten iron takes on the shape of small iron beads, which is the result of multiple small droplets gathering. The reduction of TiO2 is carried out by a series of reactions, the Ti exhibits a granular embedding state in molten iron, its color is darker than that of molten iron and its particles have distinct edges and corners. In the slag-coke area of retained sample, the reduction reaction occurs between coke and oxides in slag. The carbon will be consumed, resulting in a decrease in particle size. In the iron-coke area of retained sample, the carburization reaction occurs in large quantities due to the carbon content of molten iron in hearth is undersaturated, coke is further consumed.

Correlating structural changes in thermoresponsive hydrogels to the optical response of embedded plasmonic nanoparticles.

Stimuli-responsive microgels, composed of small beads with soft, deformable polymer networks swollen through a combination of synthetic control over the polymer and its interaction with water, form a versatile platform for development of multifunctional and biocompatible sensors. The interfacial structural variation of such materials at a nanometer length scale is essential to their function, but not yet fully comprehended. Here, we take advantage of the plasmonic response of a gold nanorod embedded in a thermoresponsive microgel (AuNR@PNIPMAm) to monitor structural changes in the hydrogel directly near the nanorod surface. By direct comparison of the plasmon response against measurements of the hydrogel structure from dynamic light scattering and nuclear magnetic resonance, we find that the microgel shell of batch-polymerized AuNR@PNIPMAm exhibits a heterogeneous volume phase transition reflected by different onset temperatures for changes in the hydrodyanmic radius (RH) and plasmon resonance, respectively. The new approach of contrasting plasmonic response (a measure of local surface hydrogel structure) with RH and relaxation times paves a new path to gain valuable insight for the design of plasmonic sensors based on stimuli-responsive hydrogels.

Effect of microplastic particles on the population growth rate and clearance rate of selected ciliates (Protista, Ciliophora).

Microplastics (MPs), due to their micro size, which overlaps with the typical food size of various aquatic organisms, can be ingested and move up the food chain, accumulating in the bodies of organisms at higher trophic levels. Few studies have focused on the uptake of MPs by ciliates, which are an important element of the microbial cycle. Three different ciliate species were used in this study: Blepharisma japonicum, Euplotes sp., and Spirostomum teres, as well as polystyrene beads with diameters of 1 and 2µm at two concentrations (106 and 107 beads × mL-1). The results of the experiments showed that MPs have a variable, species-specific effect on the population growth rate of ciliates, which is directly dependent on their concentration in the environment (P < 0.01). It was also observed that the number of MPs ingested changed over time depending on their concentration and size. On average, the highest number of ingested MPs (883.11 ± 521.47) was recorded at 60min of exposure to a low concentration of small beads in B. japonicum. The lowest number of beads was ingested after 5min of exposure to a low concentration of large beads in the same species. The rate of MP uptake by the ciliate species was significantly dependent on their concentration, exposure time, and size (P < 0.001). The highest clearance rate was observed in the fifth minute of the experiment in the environment with the lowest MP concentration.