Dynamic nano-Ag colloids cytotoxicity to and accumulation by Escherichia coli:Effects of Fe^3+,ionic strength and humic acid

Released Ag ions or/and Ag particles are believed to contribute to the cytotoxicity of Ag nanomaterials,and thus,the cytotoxicity and mechanism of Ag nanomaterials should be dynamic in water due to unfixed Ag particle:Ag+ ratios.Our recent research found that the cytotoxicity of PVP-Ag nanoparticles is attributable to Ag particles alone in 3 hr bioassays,and shifts to both Ag particles and released Ag^+ in 48 hr bioassays.Herein,as a continued study,the cytotoxicity and accumulation of 50 and 100 nm Ag colloids in Escherichia coli were determined dynamically.The cytotoxicity and mechanisms of nanoAg colloids are dynamic throughout exposure and are derived from both Ag ions and particles.Ag accumulation by E.coli is derived mainly from extracellular Ag particles during the initial 12 hr of exposure,and thereafter mainly from intracellular Ag ions.Fe^3+ accelerates the oxidative dissolution of nano-Ag colloids,which results In decreasing amounts of Ag particles and particle-related toxicity.Na^+ stabilizes nano-Ag colloids,thereby decreasing the bioavailability of Ag particles and particle-related toxicity.Humic acid(HA) binds Ag^+ to form Ag^+-HA,decreasing ion-related toxicity and binding to the E.coli surface,decreasing particle-related toxicity.HA in complex conditions showed a stronger relative contribution to toxicity and accumulation than Na^+ or Fe^3+.The results highlighted the cytotoxicity and mechanism of nano-Ag colloids are dynamic and affected by environmental factors,and therefore exposure duration and water chemistry should be seriously considered in environmental and health risk assessments.

Special Issue:Carbohydrate Hydrocolloids in Food Systems:from Structure to Human Health

Preface Carbohydrate hydrocolloids mainly refer to the carbohydrate polymers and oligomers that can form colloidal systems when dispersed in water.A great variety of these poly saccharides and oligosaccharides are used as functional food additives,such as starch,modified starch,pectin,xanthan,carrageenans,gellan gum,alginate,galactomannans(e.g.,guar gum and locust bean gum),gum Arabic or acacia gum,gum karaya,gum tragacanth,carboxymethyl cellulose,and various oligosaccharides,to name but a few.

Characterization and stability of sedimentary colloids in different ecology regions in Taihu Lake

Colloidal particles,heterogeneous mixture with various organic components and continuous molecular weight(MW)distribution,is omnipresent in lake sediments and substantially influence the retention,transportation,and fate of contaminants in lake ecosystem.We sampled and extracted sedimentary colloids from different ecology regions in Taihu Lake,Jiangsu,East China,in June 2020,and they were further separated into four different particle size ranges by tangent ultrafiltration,and the properties of colloids were studied in various methods,including zeta potential analysis,transmission electron micrograph images(TEM),Fourier transformation infrared(FTIR),and 3D fluorescence.Results show that the surface of the colloids is covered with organic macromolecular substances,such as humuslike substances and protein-like substances.There were significant differences in molecular weight and fraction content of colloids in the sediments from macrophyte-dominant(MD)area and algae-dominant(AD)area in the lake.Colloids from MD area are mainly composed of humic acid,protein,and fulvic acid;the content of fulvic acid is lower than that of humic acid and protein.The humic acid exists mainly in small molecular weight(10-100 kDa),protein exists in mainly large molecular weight colloids(0.45-1μm).Colloids from AD area are mainly composed of humic acid,and mainly distributed in the molecular weight(10 kDa-0.45μm).The presence of humic acid inhibits effectively the agglomeration of the colloids.Especially,the stability of colloids is closely related to the molecular weight,with low molecular weight from MD area show higher stability.The existence of humic acid in colloids increases the electrostatic repulsion between colloidal particles,which can effectively inhibit the agglomeration of colloids,thus enhancing the stability of colloids.Furthermore,both monovalent and divalent electrolytes enhance colloidal aggregation,and the low-molecular-weight(LMW)colloid fraction exhibits higher stability efficiency than the high-molecular-weight(HMW)colloidal.

Photostability of colloidal single photon emitter in near-infrared regime at room temperature

The photostability of a colloidal single photon emitter in near-infrared regime at room temperature is investigated.The fluorescence lifetime,blinking phenomenon,and anti-bunching effect of a single CdTeSe/ZnS quantum dot with an emission wavelength of 800 nm at room temperature are studied.The second-order correlation function at zero delay time is much smaller than 0.1,which proves that the emission from single quantum dots at 800 nm is a highly pure single-photon source.The effects of the irradiation duration on the fluorescence from single quantum dots are analyzed.The experimental results can be explained by a recombination model including a multi-nonradiative recombination center model and a multi-charged model.

An oxygenating colloidal bioink for the engineering of biomimetic tissue constructs

Ensuring a sufficient oxygen supply is pivotal for the success of bioprinting applications since it fosters tissue integration and natural regeneration.Variation in oxygen concentration among diverse tissues necessitates the precise recreation of tissue-specific oxygen levels in imprinted constructs to support the survival of targeted cells.Although oxygen-releasing biomaterials,such as oxygen-generating microparticles(OMPs),have shown promise for enhancing the oxygen supply of microenvironments in injured tissues,whether this approach is scalable for large tissues and whether tissue-specific bioinks with varying OMP concentrations remain printable remain unknown.This study addresses this critical gap by introducing an innovative class of engineered oxygenated bioinks that combine colloidal-based microgels with OMPs.We report that incorporating nanosized calcium peroxide(nCaO_(2))and manganese oxide nanosheets(nMnO_(2))into hydrophobic polymeric microparticles enables precise modulation of oxygen release while controlling hydrogen peroxide release.Moreover,the fabrication of oxygenating and cytocompatible colloidal gels is achieved using an aqueous two-phase system.This study thoroughly evaluates the fundamental characteristics of the resulting bioink,including its rheological behaviors,printability,shape fidelity,mechanical properties,and oxygen release properties.Moreover,this study demonstrates the macroscopic scalability and cytocompatibility of printed constructs produced via cell-laden oxygenating colloidal bioinks.By showcasing the effectiveness of extrusion-based bioprinting,this study underscores how it can be used to fabricate biomimetic tissues,indicating its potential for new applications.The findings presented here advance the bioprinting field by achieving scalability with both high cell viability and the possibility of mimicking specifically oxygenated tissues.This work thereby offers a promising avenue for the development of functional tissues with enhanced physiological relevance.

Cr^(Ⅵ) adsorption on four typical soil colloids: equilibrium and kinetics

It is observed that the adsorption of chromium are greater on kaolinite minerals, red soil (R) and laterite (L) colloids than that on montmorillonite, indicotic black (IB) and yellow brown (YB) soil colloids. The adsorption process of Cr Ⅵ on these media can be further described by Langmuir or Freundlich equation quite well. The adsorption reaction of Cr Ⅵ is fast, and the adsorption equilibrium can be reached within the first two hours in moderate temperature. The adsorption quantity of Cr Ⅵ to kaolinite mineral increased with the increasing pH in the range of 2.0 to 7.0, then decreased at higher pH. But it showed some consistence among the four soil colloids. The lower the pH, the stronger the adsorption. The possible mechanisms are further discussed here. Meanwhile the influence of temperature on Cr Ⅵ adsorption on different soil colloid and clay minerals are also investigated.

DEPLETION POTENTIAL OF COLLOIDS: A DIRECT SIMULATION STUDY

The depletion interaction between a big sphere and a hard wall and between two big hard spheres in a hard sphere colloidal sytem was studied by the Monte Carlo method. Direct simulation of free energy difference was performed by means of the Acceptance Ratio Method (ARM).

Effect of TiO_2 Nanoparticles on Photochromism of WO_3 Colloids

WO2 and TiO2 colMds were synthesized by the hydrolysis technique and part of the TiO2 colloid was treated by means of the hydrothermal method. The photochromic performances of the resulting materials obtained via combining the WO3 colloid with the treated TiO2 colloid and the non-treated TiO2 colloid, respectively, are very different. The TiO2 colloid without hydrothermal treatment can effectively improve the photochromic performance of the WO3colloid. The TiO2 nanoparticles were investigated in detail by XRD, TEM, surface photovohage spectra（SPS） and field-induced surface photovoltage spectrometry（FISPS）. The photochromism mechanism of WO3 colloid is discussed.

SYNTHESIS OF POLYMER-STABILIZED RUTHENIUM COLLOIDS BY LOW BOILING POINT ALCOHOL REDUCTION

Stable and well-dispersed poly(N-vinyl-2-pyrrolidone) (PVP)-stabilized ruthenium colloidal clusters wereprepaxed via the reduction of ruthenium(III) chloride by refluxing with low boiling point alcohols. Investigation of the size ofRu colloids by transmission electron microscopy (TEM) indicated that the average diametes could be controlled in the rangeof 1.2-1.6 nm with relative standard deviations of less than 0.33 by changing the molar ratio of PVP to Ru. The X-rayphotoelectron spectroscopy (XPS) characterization verified the formation of elemental ruthenium colloids.

PREPARATION OF POLYMER MICROSPHERES WITH PYRIDYL GROUP AND THEIR STABILIZED GOLD METALLIC COLLOIDS

Narrow disperse poly（ethyleneglycol dimethacrylate-co-4-vinylpyridine） （poly（EGDMA-co-4-VPy）） microspheres were prepared by distillation-precipitation copolymerization of ethyleneglycol dimethacrylate （EGDMA） and 4-vinylpyridine （4-VPy） with 2,2＇-azobisisobutyronitrile （AIBN） as initiator in neat acetonitrile. The polymer microspheres containing pyridyl group were then utilized as stabilizer for gold metallic colloids with the diameter around 7 nm, which were prepared by the in situ reduction of gold chloride trihydrate with sodium borohydride through the coordination of the pyridyl group on the gel layer and surface of the microsphere with the gold metallic nano-particles. The catalytic properties of the pyridyl- functionalized microsphere-stabilized gold metallic colloids and the behavior of the stabilized-catalyst for the recycling were investigated with reduction of 4-nitrophenol to 4-aminophenol as a model reaction.

Adsorption of Cadmium by Soil Colloids and Minerals in Presence of Rhizobia

Experiments were conducted to study the adsorption of Cd on two soil colloids (red soil and yellow- brown soil) and three variable-charge minerals (goethite, noncrystalline Fe oxide and kaolin) in the absence and presence of rhizobia. The tested strain Rhizobium fredii C6, tolerant to 0.8 mmol L-1 Cd, was selected from 30 rhizobial strains. Results showed that the isotherms for the adsorption of Cd by examined soil colloids and minerals in the presence of rhizobia could be described by Langmuir equation. Within the range of the numbers of rhizobial cells studied, the amount of Cd adsorbed by each system increased with increasing rhizobial cells. Greater increases for the adsorption of Cd were found in red soil and kaolin systems. Rhizobia influence on the adsorption of Cd by examined soil colloids and minerals was different from that on the adsorption of Cu. The presence of rhizobia increased the adsorption sanity of soil colloids and minerals for Cd, particularly for the goethite and kaolin systems. The discrepancies in the influence of rhizobia on the adsorbability and affinity of selected soil colloids and minerals for Cd suggested the different interactions of rhizobia with various soil components. It is assumed that bacterial biomass plays an important role in controlling the mobility and bioavailability of Cd in soils with kaolinite and goethite as the major colloidal components, such as in variable-charge soil.

Effect of Cr(Ⅵ) and p-Chloroaniline Interaction on Their Reaction Behaviors on Soil Colloids

INTRODUCTIONStudiesonheavymetalororganicpollutantsinsoilhaverecedelymadegreatprogressboththeoreticallyandpractically.However,pollutionisusuallydevelopedbynotasinglebutamulti-substratecomplex.Furtherunderstandingthemechanismsandprocedureofmulti-substr...

Adsorption of Acid Phosphatase on Minerals and Soil Colloids in Presence of Citrate and Phosphate

The aim of this work was to study the influence of phosphate and citrate,which are common inorganic and organic anions in soils,on the adsorption of acid phosphatase by kaolin,goethite and the colloids separated from yellow-brown soil(YBS)and latosol(LS)in central-south China.The YBS colloid has the major clay mincral composition of 1.4 nm mincral,illite and kaolinite while the LS colloid mainly contains kaolinite and oxides.The adsorption isotherm of acid phosphatase on the examined soil colloids and minerals fitted to the Langmuir model.The amount of enzyme adsorbed in the absence of ligands was in the order of YBS colloid>LS colloid>kaolin≈goethite.In the presence of phosphate or citrate,the amounts of the enzyme adsorbed followed the sequence YBS colloid>kaolin>LS colloid>goethite.The presence of ligands also decreased the binding energy between the enzyme and soil colloids or minerals.With the increase of ligand concentration from 10mmol L^-1 to 400 m mol L^-1,different behaviors for the adsorption of cnzyme were found in the colloid and mineral systems studied.A sharp decrease in enzyme adsorption was observed on goethite while gradual decreases of enzyme adsorption were recorded in the two soil colloid systems.However,no any decrease was found for the amount of enzyme adsorbed on kaolin at higher ligand concentrations.When phosphate or citrate was introduced to the system before the addition of enzyme,the ligands usually enhanced the adsorption of enzyme.The results obtained in this study suggested the important role of kaolinite mineral in the adsorption of enzyme molecules in acidic soils in the presence of various ligands.

Effect of Aqueous Colloids on Arsenic Geochemistry:Evidences from Ultrafiltration of High Arsenic Groundwater in the Hetao Basin,Inner Mongolia

Groundwater colloidal particles are believed to affect element geochemical behavior in groundwaters, which would mobilize trace element in the groundwater system.Investigation of As geochemisttry as impacted by colloids was carried out by using ultrafiltration technology in the Hetao basin,Inner Mongolia.Six groundwater sampling points have been chosen,including five with high As concentration (】100μg/L) and one with low As concentra-

INFLUENCES OF SEVERAL SOIL COLLOIDS ON THE ADSORPTION AND PROPERTIES OF UREASE ENZYME

The present experiment was designed to elucidate the effects of the sterilized colloids separated from red soil,latosol and yellow brown soil,which are the typical zonal soils in central-south China, on the adsorption,activity,kinetic parameters and thermal stability of urease enzyme which plays significant role in the transformation of soil nitrogen compounds. Results show that the amount of enzyme adsorbed on the examined soil colloids followed the order: yellow brown soil>red soil=latosol. The residual activities of enzyme in different colloid systems are in the following sequence:red soil>latosol> yellow brown soil. The thermal stability of adsorbed enzyme is higher than that of free enzyme. The enzyme immobilized on yellow brown soil colloid had the highest stability at elevated temperature from 60 to 80℃. Both of the free and immobilized urease obey Michaelis-Menten kinetics. The Km values of immobilized urease (13. 5-20. 8 mM) on different soil colloids examined were in the same order of magnitude as that of free urease (9. 3mM). The kinetic constant of immobilized enzyme suggests that urease adsorbed on yellow brown soil colloid has a greater affinity for substrate. The Ku and Vmax values also indicate a mixed type of enzyme inhibition for the examined soil colloids. These results provide basic evidences for the understanding of the properties and kinetics of soil enzymes in tropic and subtropic regions.

SYNTHESIS OF POLYMER-STABILIZED PLATINUM/RUTHENIUM BIMETALLIC COLLOIDS AND THEIR CATALYTIC PROPERTIES FOR SELECTIVE HYDROGENATION OF CROTONALDEHYDE

Polymer-stabilized platinum/ruthenium bimetallic colloids （Pt/Ru） were synthesized by polyol reduction with microwave irradiation and characterized by TEM and XPS. The colloidal nanoparticles have small and narrow size distributions. Catalytic performance of the Pt/Ru colloidal catalysts was investigated on the selective hydrogenation of crontonaldehyde （CRAL）. A suitable amount of the added metal ions and base can improve the selectivity of CRAL to crotylalcohol （CROL） remarkably. The catalytic activity and the selectivity are dependent on the compositions of bimetallic colloids. Thereinto, PVP-stabilized 9Pt/1Ru colloid with a molar ratio of metals Pt：Ru = 9：1 shows the highest catalytic selectivity 77.3% to CROL at 333 K under 4.0 MPa of hydrogen.

Surface Chemical Properties of Colloids in Main Soils of China

Surface chemical properties of soil colloids are the important factor affecting soil fertility and genesis.To provide scientific basis for soil genetic classification,promotion of soil fertility and reasonable fertilizqation,the specific surface area and electric charge of soil colloids in relation to clay minerals and organic matter are further discussed on the basis of the results obtained from the studies on surface chemical properties of soil colloids in five main soils of China.Results from the studies show that the effect of clay minerals and organic matter on the surface chemical properties of soil colloids is very complicated because the siloxane surface,hydrated oxide surface and organic matter surface do not exist separately,but they are always mixed together and influenced each other.The understanding of the relationship among clay minerals,organic matter and surface chemical properties of soil colloids depends upon further study of the relevant disciplines of soil science,especially the study on the mechanisms of organo-mineral complexes.

Chemical Mechanism of Flocculation and Deposition of Clay Colloids in Coastal Aquifers

Seawater intrusion has become one of serious environmental problems in coastal areas. During the replacement of saline water by fresh water in the aquifers, in-situ clay could be released, transport and deposit in the porous media due to the change of hydrodynamic and geochemical conditions, which resulted in the increasing of particle size, plugging of pores and reduction of the permeability. Batch experiments and sand column experiments were explored to study the relationships between the flocculation of in-situ clay and geochemical conditions, by changing ionic strength and ionic type of clay suspension. Column outflow was analyzed for suspended particles and electrical conductivity. The total percentage of colloid straining and interception distribution in porous media was calculated. The results indicate that porous media had an effect on the interception of clay colloid particles with about 10 percent clay colloids captured due to the rough surfaces and spatial structure of porous media. Ionic strength played a key role on the permeability reductions. The higher ionic strength is, the greater the amount of colloidal particles trapped. Ionic type also had a significant effect on the interception of clay colloid particles. Ripening was the main mechanism for the interception within porous media when the bulk solution was potassium chloride while blocking happened when the bulk solution was sodium chloride. The distribution of clay colloids in porous media was heterogeneous. The closer to the sand column inlet was the less interception of clay colloids was. The results can provide the scientific basis for preventing the water sensitivity during the process of salty aquifer restoration.

SURFACE-ENHANCED RAMAN SPECTRA OF p-AMINOBENZOIC ACID ADSORBED ON Ag2CO3 COLLOIDS

It was observed that the p-aminobenzoic acid(PABA)molecules adsorbed on A92CO3 colloids exhibited strong SERS effect,the enhancement factor is estimated at 10~7—10~8 The mechanism of SERS effect on PABA adsorbed on the colloids was discussed.

Depinning Dynamics of Two-Dimensional Charged Colloids on a Random Laser-Optical Substrate

用 Langevin 模拟，我们在随机的激光光的底层上调查二维的控告的胶体的 depinning 动力学。随底层的力量的增加，我们在 depinning 上面从水晶发现转变到近晶的流动。放大在平均速度和应用驱动力之间的关系的一条幂定律能被获得因为流动，和我们发现可伸缩的代表不对水晶比 1 大并且对近晶的流动比 1 大。