Concentration Gradient Research Articles

Microfluidic mixing probe: generating multiple concentration-varying flow dipoles

This study advances microfluidic probe (MFP) technology through the development of a 3D-printed Microfluidic Mixing Probe (MMP), which integrates a built-in pre-mixer network of channels and features a lined array of paired injection and aspiration apertures. By combining the concepts of hydrodynamic flow confinements (HFCs) and “Christmas-tree” concentration gradient generation, the MMP can produce multiple concentration-varying flow dipoles, ranging from 0 to 100%, within an open microfluidic environment. This innovation overcomes previous limitations of MFPs, which only produced homogeneous bioreagents, by utilizing the pre-mixer to create distinct concentration of injected biochemicals. Experimental results with fluorescent dyes and the chemotherapeutic agent Cisplatin on MCF-7 cells confirmed the MMP’s ability to generate precise, discrete concentration gradients with the formed flow dipoles, consistent with numerical models. The MMP’s ability to localize drug exposure across cell cultures without cross-contamination opens new avenues for drug testing, personalized medicine, and molecular biology. It enables precise control over gradient delivery, dosage, and timing, which are key factors in enhancing drug evaluation processes.

Short- and long-range roles of UNC-6/Netrin in dorsal-ventral axon guidance in vivo in Caenorhabditis elegans.

Recent studies in vertebrates and Caenorhabditis elegans have reshaped models of how the axon guidance cue UNC-6/Netrin functions in dorsal-ventral axon guidance, which was traditionally thought to form a ventral-to-dorsal concentration gradient that was actively sensed by growing axons. In the vertebrate spinal cord, floorplate Netrin1 was shown to be largely dispensable for ventral commissural growth. Rather, short range interactions with Netrin1 on the ventricular zone radial glial stem cells was shown to guide ventral commissural axon growth. In C. elegans, analysis of dorsally-migrating growth cones during outgrowth has shown that growth cone polarity of filopodial extension is separable from the extent of growth cone protrusion. Growth cones are first polarized by UNC-6/Netrin, and subsequent regulation of protrusion by UNC-6/Netrin is based on this earlier-established polarity (the Polarity/Protrusion model). In both cases, short-range or even haptotactic mechanisms are invoked: in vertebrate spinal cord, interactions of growth cones with radial glia expressing Netrin-1; and in C. elegans, a potential close-range interaction that polarizes the growth cone. To explore potential short-range and long-range functions of UNC-6/Netrin, a potentially membrane-anchored transmembrane UNC-6 (UNC-6(TM)) was generated by genome editing. unc-6(tm) was hypomorphic for dorsal VD/DD axon pathfinding, indicating that it retained some unc-6 function. Polarity of VD growth cone filopodial protrusion was initially established in unc-6(tm), but was lost as the growth cones migrated away from the unc-6(tm) source in the ventral nerve cord. In contrast, ventral guidance of the AVM and PVM axons was equally severe in unc-6(tm) and unc-6(null). Together, these results suggest that unc-6(tm) retains short-range functions but lacks long-range functions due to reduced secreted UNC-6. Ectopic unc-6(+) expression from non-ventral sources did not dramatically perturb dorsal VD growth cone polarity or axon outgrowth, suggesting that ectopic UNC-6 cannot redirect polarity once it is established in the VD/DD neurons. This is not what would be expected of a growth cone dynamically reading a gradient of UNC-6, but is consistent with the Polarity/protrusion model of growth cone guidance away from UNC-6/Netrin.

Investigating Cell-Induced Mixing Dynamics in Microfluidic Droplets Using the Lattice Boltzmann Method.

This study investigates the impact of cell dynamics on mixing efficiency within a microfluidic droplet, emphasizing the relationship between cell motion, deformability, and resultant asymmetry in velocity and concentration fields. Simulations were conducted for droplets containing encapsulated cells at varying Peclet numbers (Pe = 100-800) and coupling constants (kt = 0.0025, 0.005, 0.0075). The mixing index was significantly enhanced by the presence of the encapsulated cell, particularly at high Peclet numbers, where cell-induced disturbances in the velocity field disrupted symmetrical flow patterns, improving mixing. An asymmetry index quantified deviations in velocity and concentration fields caused by cell motion. Results revealed a complex interplay between cell deformability and fluid-cell interactions. Lower coupling constants corresponded to weaker velocity field asymmetry but, paradoxically, higher mixing indices. This counterintuitive finding was examined by analyzing the asymmetry in the x-component of the velocity field, aligned with the primary concentration gradient. Disturbances in this direction enhanced convective transport across the diffusion interface, crucial for efficient mixing. The study also examined cell trajectory and membrane deformation during droplet generation. Cells with moderate deformability exhibited greater off-center movement, leading to increased rotational dynamics and chaotic flow patterns conducive to enhanced mixing. In contrast, cells with higher or lower deformability followed more constrained paths, resulting in less effective mixing. These findings suggest optimal mixing within microfluidic droplets occurs when cells exhibit moderate deformability, balancing fluid-cell coupling and the ability to induce flow field asymmetry. These insights could inform the design of microfluidic systems for applications requiring precise mixing control, such as biomedical diagnostics and chemical synthesis.

Enhancing Hydrogen Evolution Reaction through Coalescence-Induced Bubble Departure on Patterned Gold-Silicon Microstrip Surfaces.

Hydrogen bubble adhesion to the electrode presents a major obstacle for green hydrogen generation via the hydrogen evolution reaction (HER) as it would induce undesired overpotential and undermine the reaction efficiency by reducing reaction area, increasing transport resistance, and creating an undesired ion concentration gradient. While electrodes with aerophobic/hydrophilic surfaces have been developed to facilitate bubble detachment, they primarily rely on micro- and nanostructured catalyst surfaces to enhance buoyance-induced bubble departure. Here, we demonstrate that introducing nonreactive yet more hydrophilic surfaces can promote coalescence-induced bubble departure, thereby significantly reducing the transport overpotential and improving HER performance. Through a systematic study using patterned gold-silicon microstrip (GSM) surfaces with varied gold strip widths (50-1600 μm), we found that reducing the gold strip width results in a smaller bubble departure diameter and increased bubble departure frequencies, leading to a 400 mV reduction in transport overpotential at 400 mA/cm2 on 50 μm wide GSM surfaces. These patterned surfaces demonstrated superior HER performance compared to a plain gold surface, even with a 50% reduction in the reaction area. The optimal HER performance, characterized by the lowest total overpotential, was achieved on GSM surfaces with 200 μm wide gold strips, highlighting the intricate interplay between improved bubble dynamics and reduced reaction area.

Space Charge Improved Poly(Aryl Ether Sulfone) Composite Membrane for Osmotic Energy Conversion

Comprehensive SummaryThe ion‐selective porous membrane is the key component in osmotic energy conversion, and optimizing its permeability and selectivity is crucial for improving output performance. Here, to construct a permeability and selectivity synergistically enhanced osmotic energy generator, the surface and space charge synergistically enhanced 3D composite membrane is prepared by inserting sulfonated hydrogels into the 3D ion channels with tunable surface charge. The membrane's selectivity is improved from 0.66 to 0.94 by increasing the charge density on the membrane surface and the spatial charge density of the membrane. The experimental and simulation results showed that the synergistic enhancement of the spatial and surface charges significantly improved the electrostatic interactions between the ions and the ion channels, which led to the enhancement of selectivity, net ionic fluxes, and output performance. The space charge improved composite membrane presents an advanced power density of about 6.4 W·m–2 under a 50‐fold concentration gradient, which is nearly 2 times that of the phase inversion membrane without hydrogels. Our study provides a promising solution for constructing high‐performance osmotic energy generators.

Non-Stoichiometric Amorphous Calcium Carbonate Forms in Macromolecular Condensates via Interphase Diffusion.

Transient amorphous phases are known as functional precursors in the formation of crystalline materials, both in vivo and in vitro. A common route to regulate amorphous calcium carbonate (ACC) crystallization is via direct interactions with negatively charged macromolecules. However, a less explored phenomenon that can influence such systems is the electrostatically driven formation of Ca-macromolecule dense phases. In this study, it is shown how Ca-macromolecule condensates that form via liquid-liquid phase separation (LLPS) can be used to control the formation of metastable ACC via diffusion-based mass transport. Contrary to the solid-like ACC particles that form in the dilute phase via rapid nucleation and growth, the condensate ACC gradually forms via carbonate diffusion into the dense droplets. This yields transient phases with non-stoichiometric compositions, similar to a solid solution. It is shown that the ability to control the concentration gradients across the phase boundary can be used to finely regulate the composition and stability of these amorphous precursors, offering new routes to control mineralization through transient phases.

Study on the Coarsening Behavior of Interphase Precipitates and Random Precipitates in Steel Under the High-Temperature Environment of Fire

In the domain of fire-resistant steels, the characteristics of precipitates significantly influence material properties. This study developed a novel heat treatment protocol to concurrently achieve both interphase precipitation and random precipitation. Samples were subjected to isothermal treatments at various temperatures and durations, while techniques such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to thoroughly analyze the coarsening behavior of the two types of precipitate and reveal their thermal stability differences. The results show that the growth and coarsening rates of interphase precipitates are substantially lower than random precipitates. Coarsening kinetics analysis reveals that the radius of random precipitates follows a 1/3 power law with time at 600 °C and 650 °C, whereas the radius of interphase precipitates adheres to a 1/6 power law at 600 °C and a 1/5 power law at 650 °C. Furthermore, interphase precipitation demonstrates excellent size uniformity, which hinders the formation of a concentration gradient, thereby reducing the coarsening rate and enhancing thermal stability. After prolonged tempering treatment, interphase precipitation maintains a higher strengthening contribution than random precipitation. This study provides novel insights and theoretical foundations for the design and development of fire-resistant steels.

Transport Numbers and Electroosmosis in Cation-Exchange Membranes with Aqueous Electrolyte Solutions of HCl, LiCl, NaCl, KCl, MgCl2, CaCl2 and NH4Cl

Electroosmosis reduces the available energy from ion transport arising due to concentration gradients across ion-exchange membranes. This work builds on previous efforts to describe the electroosmosis, the permselectivity and the apparent transport number of a membrane, and we show new measurements of concentration cells with the Selemion CMVN cation-exchange membrane and single-salt solutions of HCl, LiCl, NaCl, MgCl2, CaCl2 and NH4Cl. Ionic transport numbers and electroosmotic water transport relative to the membrane are efficiently obtained from a relatively new permselectivity analysis method. We find that the membrane can be described as perfectly selective towards the migration of the cation, and that Cl− does not contribute to the net electric current. For the investigated salts, we obtained water transference coefficients, tw, of 1.1± 0.8 for HCl, 9.2 ± 0.8 for LiCl, 4.9 ± 0.2 for NaCl, 3.7 ± 0.4 for KCl, 8.5 ± 0.5 for MgCl2, 6.2 ± 0.6 for CaCl2 and 3.8 ± 0.5 for NH4Cl. However, as the test compartment concentrations of LiCl, MgCl2 and CaCl2 increased past 3.5, 1.3 and 1.4 mol kg−1, respectively, the water transference coefficients appeared to decrease. The presented methods are generally useful for characterising concentration polarisation phenomena in electrochemistry, and may aid in the design of more efficient electrochemical cells.

Fabrication of Concentration Gradient Structures for High-Performance Capacitive Pressure Sensors by Novel Acoustic Resonance Mixing

Fabrication of Concentration Gradient Structures for High-Performance Capacitive Pressure Sensors by Novel Acoustic Resonance Mixing

Growth of microbes in competitive lifestyles promotes increased ARGs in soil microbiota: insights based on genetic traits

BackgroundThe widespread selective pressure of antibiotics in the environment has led to the propagation of antibiotic resistance genes (ARGs). However, the mechanisms by which microbes balance population growth with the enrichment of ARGs remain poorly understood. To address this, we employed microcosm cultivation at different antibiotic (i.e., Oxytetracycline, OTC) stresses across the concentrations from the environmental to the clinical. Paired with shot-gun metagenomics analysis and quantification of bacterial growth, trait-based assessment of soil microbiota was applied to reveal the association between key ARG subtypes, representative bacterial taxa, and functional-gene features that drive the growth of ARGs.ResultsOur results illuminate that resistome variation is closely associated with bacterial growth. A non-monotonic change in ARG abundance and richness was observed over a concentration gradient from none to 10 mg/l. Soil microbiota exposed to intermediate OTC concentrations (i.e., 0.1 and 0.5 mg/l) showed greater increases in the total abundance of ARGs. Community compositionally, the growth of representative taxa, i.e., Pseudomonadaceae was considered to boost the increase of ARGs. It has chromosomally carried kinds of multidrug resistance genes such as mexAB-oprM and mexCD-oprJ could mediate the intrinsic resistance to OTC. Streptomycetaceae has shown a better adaptive ability than other microbes at the clinical OTC concentrations. However, it contributed less to the ARGs growth as it represents a stress-tolerant lifestyle that grows slowly and carries fewer ARGs. In terms of community genetic features, the community aggregated traits analysis further indicates the enhancement in traits of resource acquisition and growth yield is driving the increase of ARGs abundance. Moreover, optimizations in energy production and conversion, alongside a streamlining of bypass metabolic pathways, further boost the growth of ARGs in sub-inhibitory antibiotic conditions.ConclusionThe results of this study suggest that microbes with competitive lifestyles are selected under the stress of environmental sub-inhibitory concentrations of antibiotics and nutrient scarcity. They possess greater substrate utilization capacity and carry more ARGs, due to this they were faster growing and leading to a greater increase in the abundance of ARGs. This study has expanded the application of trait-based assessments in understanding the ecology of ARGs propagation. And the finding illustrated changes in soil resistome are accompanied by the lifestyle switching of the microbiome, which theoretically supports the ARGs control approach based on the principle of species competitive exclusion.4ZqjNsN9dRS1iWJDwru5hLVideo

Boron atoms migration during epitaxial growth of boron-doped single-crystal diamond

Boron-doped diamond (BDD) films are essential for the fabrication of electronic devices with P+ or P− layers. However, the boron atoms in the intrinsic diamond substrates due to the concentration gradient may affect the height of the Schottky barrier based on these BDD films. BDD films with different concentrations of boron atoms were deposited on chemical vapor deposition (CVD) diamond seeds by microwave plasma chemical vapor deposition. Laser confocal Raman spectroscopy was utilized to investigate the migration of boron atoms during the CVD deposition process. The results indicate that the diffusion depth is below 20 μm with a boron atom concentration of 1020 cm−3 at a deposition time of 10 h. The boron atom diffusion depth is below 8 μm at a fixed CH4/H2 ratio of 2% after 5 h deposition. The characteristic peak of boron atoms is not detected by Raman spectroscopy after 3 h deposition, while the infrared spectrum indicates that the boron atom concentration is more than 1018 cm−3. Consequently, the boron atom concentration and the diffusion depth in CVD seeds can be regulated by controlling the CH4/H2 ratio and the deposition time. Planar diamond-based Schottky diodes based on the prepared P+ or P− layer exhibit distinct rectification characteristics.

Dual-Sided Superhydrophobic Laser-Induced Graphene Evaporator for Efficient Desalination and Brine Treatment under High Salinity.

The immense energy footprint of desalination and brine treatment is a barrier to a green economy. Interfacial evaporation (IE) offers a sustainable approach to water purification by efficient energy conversion. However, conventional evaporators are susceptible to fluctuations in solar radiation and the salinity of handling liquid. The present research is an innovative step toward the fabrication of superhydrophobic laser-induced graphene (LIG) interfacial evaporators for desalination and brine treatment. The fabricated dual-sided superhydrophobic laser-induced graphene (DSLIG) exhibits self-cleaning ability on both sides, enhancing salt rejection capabilities through a lotus effect. This multilayered evaporator comprises a top layer of MPES LIG and a bottom layer of PVDF AR 972 LIG, resulting in superior localized heat generation ability. The engineered surface has undergone performance analysis with DI water and NaCl solutions with concentrations of 3.5-24 wt %. The dual-stacked configuration with coupled solar (one sun)-joule heating (5 V) attained evaporation rates of ∼5 kg m-2 h-1 for distilled water and ∼2.2 kg m-2 h-1 for a 24 wt % NaCl solution. The remarkable outcome resulted from substantial thermophysical property changes with LIG formation. The DSLIG's bottom concentration gradient promoted salt back diffusion and ceased salt penetration to the top surface. The work can be further extended to treat the desalination brine for sustainable desalination and zero liquid discharge.

Towards measurements of absolute membrane potential in Bacillus subtilis using fluorescence lifetime.

Membrane potential (MP) changes can provide a simple readout of bacterial functional and metabolic state or stress levels. While several optical methods exist for measuring fast changes in MP in excitable cells, there is a dearth of such methods for absolute and precise measurements of steady-state membrane potentials (MPs) in bacterial cells. Conventional electrode-based methods for the measurement of MP are not suitable for calibrating optical methods in small bacterial cells. While optical measurement based on Nernstian indicators have been successfully used, they do not provide absolute or precise quantification of MP or its changes. We present a novel, calibrated MP recording approach to address this gap. In this study, we used a fluorescence lifetime-based approach to obtain a single-cell resolved distribution of the membrane potential and its changes upon extracellular chemical perturbation in a population of bacterial cells for the first time. Our method is based on (i) a unique VoltageFluor (VF) optical transducer, whose fluorescence lifetime varies as a function of MP via photoinduced electron transfer (PeT) and (ii) a quantitative phasor-FLIM analysis for high-throughput readout. This method allows MP changes to be easily visualized, recorded and quantified. By artificially modulating potassium concentration gradients across the membrane using an ionophore, we have obtained a Bacillus subtilis-specific MP versus VF lifetime calibration and estimated the MP for unperturbed B. subtilis cells to be -65 mV (in MSgg), -127 mV (in M9) and that for chemically depolarized cells as -14 mV (in MSgg). We observed a population level MP heterogeneity of ∼6-10 mV indicating a considerable degree of diversity of physiological and metabolic states among individual cells. Our work paves the way for deeper insights into bacterial electrophysiology and bioelectricity research.

Effect of concentration gradient on spiral wave dynamics in the Belousov-Zhabotinsky reaction system.

The oscillatory Belousov-Zhabotinsky (BZ) reaction is often used for the study of rotating spiral waves that are responsible for life-threatening cardiac arrhythmia. In this work, we explore the influence of a concentration gradient on the dynamics of spiral waves in the BZ-reaction system. Using ion-exchange resin beads, we introduce a gradient of hydrogen ions in a thin layer of BZ gel hosting a spiral wave. By monitoring the drift of the spiral tips from their initial position, we show that a gradient of hydrogen-ions can manoeuvre the position of the spiral. The magnitude of the drift is found to depend on the gradient strength and relative position of the spiral from the resin beads. Our experimental study is supported with numerical simulations carried out on a modified Oregonator model that we have developed from the Field, Körös, Noyes mechanism of the BZ.

Spatial-temporal Variations and Driving Factors Analysis of Total Nitrogen Concentration in the Haihe River Basin from 2018 to 2022

The Beijing-Tianjin-Hebei （Jing-Jin-Ji） Region is home to the most acute economic, resource, and environmental conflicts in the Bohai Sea region, and the rivers entering the sea carry abundant total nitrogen （TN） input into the Bohai Bay, which is the main land-based input causing eutrophication of the bay. The Haihe River Basin in the Jing-Jin-Ji Region was divided into 112 （2018-2019） and 187 （2020-2022） control units, and the spatial and temporal variations in TN concentration in the surface water of the Haihe River Basin in the Jing-Jin-Ji Region were systematically analyzed from 2018 to 2022 by combining the Euclidean distance analysis method and the K-means clustering analysis method. The results showed that the annual average concentration of TN in the region showed a trend of decreasing （2018-2020） and then increasing （2021-2022）, in which the concentration of TN increased significantly from June 2021 to June 2022. The concentration of TN throughout the year showed a "U"-shaped distribution, with a lower concentration in the abundant water period and a higher concentration in the dry water period. Compared with that in the dry water period, the number of control units in the high-concentration interval decreased, and the number of control units in the low-concentration interval increased in the abundant water period. TN concentrations were higher in control units during the flat-water period （October to December） compared to those in the flat-water period （March to May）. Control units with concentration gradients exceeding 10 mg·L-1 and 0-1 mg·L-1 were characterized by significant spatial migration, with the center of mass of control units exceeding 10 mg·L-1 shifting to the northeast, and the center of mass of control units with 0-1 mg·L-1 shifting from the center to the south-central part. Three patterns of TN concentration changes in the control unit were identified, and one "U"-shaped pattern and one "W"-shaped pattern characterized the increase in TN concentration in the flood season. The spatial and temporal distribution of TN concentration in the watershed was characterized by the combined effects of soil nitrogen storage, rainfall, and temperature. The significant increase in TN concentration after 2021 was caused by the short-term flushing of the extreme rainfall event in the summer of that year, and by the effect of groundwater uplift after heavy rainfall.

On Diffusiophoresis of a Soft Particle with a Hydrophobic Inner Core: A Semianalytical Study.

The current study deals with a theoretical analysis of diffusiophoresis of a soft particle, consisting of a hydrophobic charged rigid core coated with an ion- and fluid-penetrable charged polymer layer suspending in an electrolyte medium in reaction to an applied concentration gradient. The inner core's hydrophobicity is assumed to be characterized by a surface-charge-dependent slip length parameter. Based on a weak particle charge consideration, the governing equations describing the flow phenomena are solved theoretically to deduce a semianalytic general diffusiophoretic mobility expression applied to an arbitrary Debye layer thickness. A closed-form analytic solution is also obtained, which applies to a thin Debye length and low permeable porous layer. The impact of the charge-dependent wettability of the rigid core on the particle's diffusiophoretic motion is analyzed. We found that the inner core's hydrophobicity profoundly influences the particle mobility at a thicker Debye layer with a constant surface charge density when the chemiphoresis and electrophoresis components assist each other. At a fixed ζ-potential, the effect of the hydrophobic core is substantial for a thinner Debye length. In addition, with a critical selection of core and polymer layer charges, mobility reversal is demonstrated by modulating the salt concentration and slip length parameters.

IDENTIFICATION OF COARSE AGGREGATES PRONE TO SURFACE DETERIORATION AND D-CRACKING IN CONCRETE PAVEMENTS

This study investigates the influence of coarse aggregates on the durability of concrete pavements exposed to freezing and thawing cycles, particularly focusing on the phenomena of surface deterioration and D-cracking. Argillaceous aggregates from Indiana pavements showed significant surface damage within one to two years of construction, despite being from approved sources and the concrete being air entrained for freeze-thaw protection. The deterioration was linked to the aggregates themselves, with no apparent damage to the surrounding cement paste. The research aimed to understand the role of osmotic effects in the aggregates' failure by conducting laboratory experiments to simulate the freezing conditions with and without salt solutions. The findings revealed that the argillaceous aggregates exhibited osmotic phenomena, leading to an additional detrimental mechanism during freezing and thawing when a salt concentration gradient exists. This study confirms the significant impact of osmotic pressure on aggregate failure and suggests a simple testing procedure to identify aggregates prone to such deterioration. The results have implications for the selection and testing of coarse aggregates used in concrete pavements, particularly in environments where deicing agents are applied. (Abstract generated by AI tool ChatGPT 4)

Increasing microplastic concentrations have nonlinear impacts on the physiology of reef-building corals.

The pollution of marine environments with plastics, particularly microplastic (MP, i.e., plastic particles <5mm), is a major threat to marine biota, including corals. While the effects of MPs are increasingly well understood, knowledge of how different concentrations of naturally occurring MP mixtures affect reef-building corals is still limited. Therefore, we aimed to elucidate the relationship of MP concentrations and their effects on reef-building corals. For this, we exposed two reef-building coral species (Stylophora pistillata and Pocillopora verrucosa) in a 12-week experiment to MPs at a gradient of concentrations (0, 0.1, 1, 10, and 100mg·L-1). Specifically, we examined effects on the coral host physiology (i.e., surface and volume growth, calcification, necrosis, and polyp activity), and the photosynthetic activity of the photosymbionts (i.e., effective and maximum quantum yield, maximum relative electron transport rate, minimum saturating irradiance, and light capture efficiency). To mimic natural conditions, we used a MP mixture consisting of six polymers in forms of fibers and fragments. Both coral species showed reduced growth rates, necrosis, lower polyp activity, and an upregulation of photosynthesis, which intensified with increasing MP concentrations. While the effects on the coral host mostly showed basic linear or nonlinear dose-response relationships, the effects on the photosymbionts revealed more complex nonlinear dose-response relationships, and photosynthesis was only upregulated after a species-specific threshold. We found that high and extreme pollution scenarios caused strong adverse effects on coral physiology, while current low to moderate concentrations had minor effects. Increasing concentrations had amplifying effects, likely due to the disproportionately higher frequency of entanglement, leading to more frequent direct contact and potential transfer of toxins or pathogens. These results suggest that corals can cope with current average pollution levels. However, they also highlight the need for measures to limit permanent increases of MP pollution to protect the health of coral reefs.

Topological structure, rheological characteristics and biological activities of exopolysaccharides produced by Saccharomyces cerevisiae ADT

Saccharomyces cerevisiae ADT is an edible fungus, with limited research on its exopolysaccharides (EPS). Three types of exopolysaccharides (EPS60, EPS80, and EPS100) were obtained through multiple purification steps using varying concentrations of ethanol in this study. The topological structure, rheological properties, and biological characteristics of EPS were investigated. High performance liquid chromatography (HPLC), Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR) analyses indicated that the three EPS are primarily made up of mannose with a small amount of glucose. Acetyl groups were also found, along with the presence of α-type pyranose and β-type pyranose. The Congo Red test and X-ray diffraction results reflected the absence of a triple helix structure and crystal properties. Atomic force microscopy (AFM) revealed the self-assembly of three exopolysaccharides into various topological structures under different concentration gradients, and a clear network structure of entangled chains was observed. EPS60, EPS80 and EPS100 displayed pseudoplasticity, weak gel behavior and thermal stability. Significantly, EPS exhibited antioxidant activity in a dose-dependent manner and showed no acute cytotoxicity to RAW264.7 and HEK293T cells. Therefore, EPS in this study is anticipated to be utilized in natural antioxidants, medications, and functional materials.

A shape-adaptive hydrogel with dual antibacterial and osteogenic properties for alveolar bone defect repair.

Alveolar bone defects are often irregular in shape and can severely affect patients' physical and psychological well-being, posing significant challenges in treatment, particularly in cases complicated by systemic diseases. This study presents a shape-adaptive hydrogel with sequential antibacterial and osteogenic functions designed to repair irregular bone defects associated with osteoporosis. Naringin, an estrogen analogue, was conjugated to the hydrogel via disulfide bonds and then uniformly mixed with nano-hydroxyapatite (nano-HAP) to create microspheres. These microspheres were uniformly dispersed within the naringin-loaded hydrogel, forming an injectable and photocurable suspension. Upon implantation, naringin is rapidly released due to diffusion along the concentration gradient and initial hydrogel degradation, providing antibacterial effects and preventing infection. As bone repair progresses, the hydrogel undergoes further degradation and the disulfide bonds break, so that naringin is continuously released, which enhances osteoblast differentiation and inhibits osteoclast differentiation. Material characterization confirmed the presence of disulfide bonds and the sustained release profile of naringin. Both in vitro and in vivo experiments demonstrated the hydrogel's excellent biocompatibility and its effectiveness in repairing regular mandibular defects as well as irregular alveolar bone defects associated with osteoporosis. This hydrogel provides a promising strategy for the development of advanced biomaterials tailored to the complex requirements of irregular bone defect repair under osteoporotic conditions.