Aggregation State Research Articles

Mechanism of physical hardening on the fracture characteristics of polymer-modified asphalt binder

This article aims to reveal the physical hardening mechanism of polymer-modified asphalt binder (PMA) and accurately assess its impact on the low-temperature fracture properties of asphalt binders. Base asphalt binder (BA), styrene–butadiene–styrene modified asphalt binder (SBSMA), and crumb rubber modified asphalt binder (CRMA) were used as the research objects. Molecular dynamics (MD) simulation and differential scanning calorimetry (DSC) test were used to investigate the physical hardening mechanism of PMA at the microscopic level. The fracture characteristics of PMA under physical hardening were analyzed based on the single-edge notched beam (SENB) test. The results show that under prolonged cold service conditions, the asphalt molecular mobility is weakened, the non-bond energy and the free volume are reduced, and the molecules undergo aggregation state transformation, leading to the physical hardening of asphalt materials. In the process of physical hardening of asphalt molecules in the micro-Brownian motion of the main active force from the aromatic and saturate fractions. Considering the effect of physical hardening, it is recommended that the method used to test the low temperature properties of asphalt binders should ensure a constant temperature for at least 24 h. The crack tolerance (Ct) is recommended as the evaluation index of low-temperature cracking resistance of PMA in cold regions. The Ct of BA, SBSMA, and CRMA are reduced by 52.88 %, 12.04 %, and 35.24 %, respectively, after 24 h of constant low temperature. This indicating that the polymer modifiers can improve the fluidity of asphalt molecules, inhibit molecular aggregation, and reduce the effect of physical hardening on asphalt binders. Thermo-oxidative aging can aggravate the physical hardening phenomenon of asphalt binder, and the higher the degree of thermo-oxidative aging, the more severe the physical hardening of asphalt binder. The related research results provide the theoretical basis and technical support for the accurate design and development of the low-temperature performance of asphalt binders for roads in cold regions.

One Platform Comparison of Polymeric and Lipidic Nanoparticles for the Delivery of Amphotericin B.

Amphotericin B (AmB) is a membrane-acting antibiotic used for the treatment of fungal and protozoal infections. AmB exists in various molecular forms, i.e., monomeric, super-aggregated, and oligomeric forms, where oligomeric forms are highly toxic because of their relative affinity toward cholesterol present over human cell membrane. Hence, the objective of our research work was to study the aggregation state of AmB in two different nanoformulations, i.e., solid lipid nanoparticles (SLNs) and zein-based nanoparticles (PNPs), with the aim of enhancing the fraction of less toxic form of AmB, and a comparative study was performed. The zein and glyceryl monostearate can intercalate the polyenic domain of AmB and thereby hinder the hydrophobic attractions between the AmB molecules, which allows their existence in monomeric forms. The particle size of AmB-SLNs and AmB-PNPs were 378.90 ± 9.50 nm and 184.90 ± 6.00 nm, while zeta potential was -34.97 ± 0.51 mV and +28.93 ± 2.29 mV, respectively. In vitro release studies showed more controlled release of AmB from PNPs (52.48 ± 1.07%) as compared to SLNs (86.33 ± 0.93%). The predominant aggregation state of AmB in both formulations was determined by UV-visible and circular dichroism spectrophotometry, where a higher degree of monomerization of AmB was reported in AmB-SLNs as compared to AmB-PNPs. Toxicity of the nanoformulations was evaluated through hemolysis test, where the results suggested that AmB-SLNs and AmB-PNPs were less hemolytic as compared to pure AmB. The nanoformulations demonstrated the predominant monomeric form of AmB, which may offer higher selectivity index toward microbial membrane.

Reblooming of the cis-Bis(2-phenylpyridine) Platinum(II) Complex: Synthesis Updating, Aggregation-Induced Emission, Electroluminescence, and Cell Imaging.

Studies on the syntheses, photophysical properties, and applications of cis-bis(2-phenylpyridine) platinum(II) complex (Pt(ppy)2) family are of great importance, but very limited progress has been achieved to date. Herein, a one-pot method was established for the syntheses of Pt(ppy)2-type complexes Pt-ppy and Pt-tBu. These two compounds were nonemissive in dilute solutions. However, they produced intense red and deep-red phosphorescence in the aggregation and film states, with lifetimes and quantum yields up to 1.92 μs and 70%, respectively, exhibiting unique aggregation-induced emission (AIE) characteristics. According to the experimental and theoretical studies, molecular configuration transformation (MCT) in the excited state may occur because of the d-d transition from the Pt center, causing nonradiative transitions in the solution. Nevertheless, the MCT would be largely restricted by the intermolecular interactions or rigid matrix, thereby enabling efficient phosphorescence in the aggregation state and in the PMMA films. Consequently, the AIE characteristics of Pt-ppy and Pt-tBu probably result from the restriction of molecular configuration transformation (RMCT). Due to the π-π and/or weak Pt-Pt interactions and the concentration-dependent emission characteristics, they emit deep-red and NIR emissions generated by excimer and/or MMLCT emitting species. Inspired by their AIE features, electroluminescence and cell imaging applications are explored. To the best of our knowledge, this is the first comprehensive study on the synthesis optimization, photophysical properties, AIE characteristics, and applications of the Pt(ppy)2-type complexes, which may rebloom the research studies on this type of Pt(II) complex family and provide valuable insights on the development of phosphorescent AIE metal-organic complexes.

Exposure to Oxidized Multi-Walled CNTs Can Lead to Oxidative Stress in the Asian Freshwater Clam Corbicula fluminea (Müller, 1774).

The increasing attention that carbon-based nanomaterials have attracted due to their distinctive properties makes them one of the most widely used nanomaterials for industrial purposes. However, their toxicity and environmental effects must be carefully studied, particularly regarding aquatic biota. The implications of these carbon-based nanomaterials on aquatic ecosystems, due to their potential entry or accidental release during manufacturing and treatment processes, need to be studied because their impacts upon living organisms are not fully understood. In this research work, the toxicity of oxidized multi-walled carbon nanotubes (Ox-MWCNTs) was measured using the freshwater bivalve (Corbicula fluminea) after exposure to different concentrations (0, 0.1, 0.2, and 0.5 mg·L-1 Ox-MWCNTs) for 14 days. The oxidized multi-walled carbon nanotubes were analyzed (pH, Raman microscopy, high-resolution electron microscopy, and dynamic light scattering), showing their properties and behavior (size, aggregation state, and structure) in water media. The antioxidant defenses in the organism's digestive gland and gills were evaluated through measuring oxidative stress enzymes (glutathione-S-transferase, catalase, and superoxide dismutase), lipid peroxidation, and total ubiquitin. The results showed a concentration-dependent response of antioxidant enzymes (CAT and GST) in both tissues (gills and digestive glands) for all exposure periods in bivalves exposed to the different concentrations of oxidized multi-walled carbon nanotubes. Lipid peroxidation (MDA content) showed a variable response with the increase in oxidized multi-walled carbon nanotubes in the gills after 7 and 14 exposure days. Overall, after 14 days, there was an increase in total Ub compared to controls. Overall, the oxidative stress observed after the exposure of Corbicula fluminea to oxidized multi-walled carbon nanotubes indicates that the discharge of these nanomaterials into aquatic ecosystems can affect the biota as well as potentially accumulate in the trophic chain, and may even put human health at risk if they ingest contaminated animals.

Thermochromic Hydrogels with Opaque-Transparent Gradient Transition for Switchable Window and Temperature Monitor.

In recent years, the thermochromic hydrogel was acted as suitable sandwiching material to adjust light transmission. However, to accurately control the thermochromic temperature in a wide range still was a significant challenge. Here, a simple method was explored to prepare hydrogels with gradient opaque-transparent transition thermochromic temperature from 5 °C to 53 °C, which was regulated by the aggregation state of sodium dodecyl sulfate micelles by adding potassium tartrate hemihydrate and cations. Using Li+ , Na+ , and K+ as cations, the accuracy was controlled at 1 °C. Moreover, the transmittance of the hydrogel was not changed when the thermochromic temperature was adjusted. As a result, an intelligent window was fabricated by utilizing thermochromic hydrogel as a sandwiching layer into the outer glass layers, which could effectively and stably regulate the visible and infrared light. The temperature monitors/detectors were also designed, which showed excellent temperature monitoring/detecting ability. Therefore, this low-cost, high-efficient, large-scale prepared thermochromic hydrogel provided more potential for intelligent temperature devices.

A Self-Assemble Supramolecular Film with Humidity Visualization Enabled by Clusteroluminescence.

Clusteroluminescence (CL) has recently gained significant attention due to its unique through-space interactions associated with a high dependence on the aggregation of subgroups. These distinct features could easily transform the stimuli into visual fluorescence and monitor the fluctuation of the environment but have not received sufficient attention before. In this work, supramolecular films are designed based on the neutralization reaction of anhydride groups and the self-assembly of dynamic covalent disulfide bonds in NaOH aqueous solution. The self-assembly of hydrophilic carboxylate chromophores and hydrophobic disulfide-containing five-membered rings could be observed by the variation of the aggregation state of carboxylate in CL. Furthermore, the dynamic cross-linking films obtained with water-sensitive carboxylate chromophores could alter the aggregation distance stimulated by surrounding water vapor, causing the emission wavelength to change from 534 to 508nm by varying the relative humidity. This work not only provides an approach to monitor the self-assembly of clusteroluminogens but also offers new strategies for designing stimuli-responsive materials that utilize the intrinsic features of CL.

Cycloplatinated(II) metallomesogens and their binary-mediated chirality transfer and amplificated deep-red circularly polarized luminescence with ultrahigh dissymmetry factor over 0.13

Incorporating supramolecular chirality and high emission into metallomesogens has great significance in the field of flexible electronic devices because of their emergent capacities for enlarged chiroptical activities and either thermotropic or solution-processability. In this work, an enantiomeric pair of chiral Pt(II) metallomesogens (S)/(R)-Pt1 were prepared through laboratory-synthesized chiral picolinic acid ligands and phenylpyridine derivatives to study their mesophase behaviors, chiroptical properties, and chirality transfer and amplification. The solutions of (S)/(R)-Pt1 emitted green phosphorescence at 508 nm, but the amorphous form displayed orange-red phosphorescence at 616 nm. Upon gentle grinding or heating, the emission color of Pt1 was dramatically changed with a bathochromic shift of 47 and 51 nm, respectively, because of emerged intermolecular π···π and Pt⋯Pt interactions in all aggregation states. Furthermore, the chiroptical properties and LC self-assembly model were proposed by Density Functional Theory (DFT) calculations and chiroptical spectrum measurements. The enantiotopic (S)/(R)-Pt1 complexes exhibited electronic circular dichroism (CD) and circularly polarized luminescence (CPL) activities in solution with a smaller asymmetry factor (±5 × 10−4) by chiral disturbance. This pair of exclusively enantiomeric complexes exhibited smectic mesophase behavior in the range of 31.4–76.5 °C but induced unsuccessfulness of helical packing in LC states due to weak induction ability. Contrastively, binary-component mediated supramolecular helical formation and amplificated deep-red CPL switch with ultrahigh dissymmetry factor over ±0.13 in helical twist grain boundary phases (TGBA*) mesophase has been realized.

J-Aggregation Strategy toward Potentiated NIR-II Fluorescence Bioimaging of Molecular Fluorophores.

Molecular fluorophores emitting in the second near-infrared (NIR-II, 1000-1700 nm) window with strong optical harvesting and high quantum yields hold great potential for in vivo deep-tissue bioimaging and high-resolution biosensing. Recently, J-aggregates are harnessed to engineer long-wavelength NIR-II emitters and show unique superiority in tumor detection, vessel mapping, surgical navigation, and phototheranostics due to their bathochromic-shifted optical bands in the required slip-stacked arrangement aggregation state. However, despite the preliminary progress of NIR-II J-aggregates and theoretical study of structure-property relationships, further paradigms of NIR-II J-aggregates remain scarce due to the lack of study on aggregated fluorophores with slip-stacked fashion. In this effort, how to utilize the specific molecular structure to form slip-stacked packing motifs with J-type aggregated exciton coupling is emphatically elucidated. First, several molecular regulating strategies to achieve NIR-II J-aggregates containing intermolecular interactions and external conditions are positively summarized and deeply analyzed. Then, the recent reports on J-aggregates for NIR-II bioimaging and theranostics are systematically summarized to provide a clear reference and direction for promoting the development of NIR-II organic fluorophores. Eventually, the prospective efforts on ameliorating and promoting NIR-II J-aggregates to further clinical practices are outlined.

Microplastics and chemical leachates from plastic pipes are associated with increased virulence and antimicrobial resistance potential of drinking water microbial communities

There is increasing recognition of the potential impacts of microplastics (MPs) on human health. As drinking water is the most direct route of human exposure to MPs, there is an urgent need to elucidate MPs source and fate in drinking water distribution system (DWDS). Here, we showed polypropylene random plastic pipes exposed to different water quality (chlorination and heating) and environmental (freeze-thaw) conditions accelerated MPs generation and chemical leaching. MPs showed various morphology and aggregation states, and chemical leaches exhibited distinct profiles due to different physicochemical treatments. Based on the physiological toxicity of leachates, oxidative stress level was negatively correlated with disinfection by-products in the leachates. Microbial network analysis demonstrated exposure to leachates (under three treatments) undermined microbial community stability and increased the relative abundance and dominance of pathogenic bacteria. Leachate physical and chemical properties (i.e., MPs abundance, hydrodynamic diameter, zeta potential, total organic carbon, dissolved ECs) exerted significant (p < 0.05) effects on the functional genes related to virulence, antibiotic resistance and metabolic pathways. Notably, chlorination significantly increased correlations among pathogenic bacteria, virulence genes, and antibiotic resistance genes. Overall, this study advances the understanding of direct and indirect risks of these MPs released from plastic pipes in the DWDS.

COMPOSITE MATERIALS BASED ON CRYOGELS

Two methods for the transition of aqueous solutions of polyvinyl alcohol (PVA) from the liquid state of aggregation to the solid state are considered. Freezing an aqueous solution of PVA at a negative temperature and subsequent thawing at a positive temperature result in the formation of rubber-like cryogels. Another way is chemical crosslinking of kinetically individual PVA macromolecules to spatial networks having elastic properties. Sodium tetraborate was used to structure aqueous PVA solutions. The rheological properties of a two-component aqueous solution of polyvinyl alcohol were studied. The study shows that the polymer solution exhibits the properties characteristic of non-Newtonian liquids. The kinetics of gelation of the products of chemical structuring of aqueous PVA solutions with an aqueous sodium tetraborate solution was studied. It is shown that viscosity increases with time as a consequence of chemical interaction. The mechanical properties of carbon-containing composite materials obtained by various methods have been investigated. It has been determined that the most durable materials are those formed by the cryotropic method and those chemically structured after cryogenic treatments. The stress-strain and moisture-resistant properties of carbon materials enable their use as fuel briquettes with a minimum amount of a binder. They can also serve as high-energy fuels for domestic and industrial purposes. The chemical method of structuring a PVA solution can be used for dust control in coal mines.

Degradation of Mechanical Properties of Graphene Oxide Concrete under Sulfate Attack and Freeze-Thaw Cycle Environment.

In this paper, firstly, the effects of graphene oxide on the mechanical properties of concrete were investigated. Secondly, the degradation and mechanism of the mechanical properties of graphene oxide concrete (GOC) under sulfate attack and a freeze-thaw environment were investigated. In addition, the dynamic modulus of elasticity (MOEdy) and uniaxial compressive strength (UCS) of the GOC were measured under different environmental conditions. According to the test results, the incorporation of graphene oxide in appropriate admixtures could improve the mechanical properties of concrete in these two working environments. It is worth noting that this effect is most pronounced when 0.05 wt% graphene oxide is incorporated. In the sulfate attack environment, the MOEdy and UTS of the GOC0.05% specimen at 120 cycles decreased by 22.28% and 24.23%, respectively, compared with the normal concrete specimens. In the freeze-thaw environment, the MOEdy and UTS of the GOC0.05% specimen at 90 cycles decreased by 13.96% and 7.58%, respectively, compared with the normal concrete specimens. The scanning electron microscope (SEM) analysis showed that graphene oxide could adjust the aggregation state of cement hydration products and its own reaction with some cement hydration crystals to form strong covalent bonds, thereby improving and enhancing the microstructure density.

Controlling Magnesium Silicates Coprecipitation Conditions: A Tool to Tune Their Surface Acid–Base Reactivity

Magnesium silicates combining acidic and basic surface properties are known to be interesting as heterogeneous catalysts. Nevertheless, their catalytic performances are highly dependent on the synthesis method used. In this study, a series of magnesium silicates was synthesized for the first time using a coprecipitation method with a micromixer. It is first shown that changes in synthesis/precipitation pH led to magnesium silicates with different Mg/Si ratios: the higher the synthesis pH, the higher the Mg/Si ratio. Moreover, prepared silicates with a final Mg/Si ratio greater than 0.7, thus prepared at high pH, exhibit negligible specific surface area, whereas relatively high values (&gt;180 m2/g) have been obtained for lower Mg/Si ratios. A set of experimental characterization data obtained by N2 physisorption, SEM, XRD, TGA-DTA as well as Raman and 29Si NMR spectroscopies are presented and discussed. They show the existence of two distinct families with a similar Magnesium Silicate Hydrate (MSH) phase, but they reveal different aggregation states and textural properties. Finally, the surface acid–base reactivity of the co-precipitated magnesium silicates was determined using the model reaction of 2-methylbut-3-yn-2-ol (MBOH) conversion. The results obtained suggest that it is possible to prepare silicates with a wide range of surface acid–base properties, from purely basic solids to those with both acidic and basic properties, by adjusting the final Mg/Si ratio via the control of the synthesis parameters.

The pH-Dependent Interplay of Surface Energy and Aggregation State for Nanoparticulate Goethite

The pH-Dependent Interplay of Surface Energy and Aggregation State for Nanoparticulate Goethite

Polymorphism and Light-Driven Forward Movement of TPE Derivative Micro-Crystal due to ArH-pi Interactions Difference.

Aggregation-induced emission (AIE) and aggregation-caused quenching (ACQ) are two classes of opposite luminescence phenomena. It is almost impossible to show both AIE and ACQ effect simultaneously by the same molecule. However, here we report that a simple TPE derivative TAP-TPE grows into both AIE crystals and ACQ ones. It is found that equatorial, contact distance-longer and weak ArH-π interactions exist in AIE crystals while vertical, contact distance-shorter and strong ArH-π interactions appear in ACQ crystals. Theoretical calculation of electron density on the interaction atoms unveils that ACQ crystals have much larger change in electron density than AIE ones, suggesting that the intermolecular electron transfer aroused by the strong ArH-π hydrogen bonds leads to ACQ phenomenon. This result provides a new insight into the emission mechanism in aggregation state. Interestingly, due to the ArH-pi interactions difference, only one of five kinds of crystals shows rapid photochromism, and can act as multimode anti-counterfeiting materials. Very exceptionally, for the first time we find that the photochromic micrometric rod-like crystal even makes forward rolling movement as it repeatedly bends and straightens by responding to on and off of the ultraviolet light irradiation, displaying potential for photo-actuator and light-driven micro-vehicle.

Flexible Strain-Sensitive Sensors Assembled from Mussel-inspired Hydrogel with Tunable Mechanical Properties and Wide Temperature Tolerance in Multiple Application Scenarios.

Conductive hydrogels, exhibiting wide applications in electronic skins and soft wearable sensors, often require maturely regulating of the hydrogel mechanical properties to meet specific demands and work for a long-term or under extreme environment. However, in situ regulation of the mechanical properties of hydrogels is still a challenge, and regular conductive hydrogels will inevitably freeze at subzero temperature and easily dehydrate, which leads to a short service life. Herein, a novel adhesive hydrogel (PAA-Dopa-Zr4+) capable of strain sensing is proposed with antifreezing, nondrying, strong surface adhesion, and tunable mechanical properties. 3,4-Dihydroxyphenyl-l-alanine (l-Dopa)-grafted poly(acrylic acid) (PAA) and Zr4+ ion are introduced into the hydrogel, which broadly alters the mechanical properties via tuning the in situ aggregation state of polymer chains by ions based on the complexation effect. The catechol groups of l-Dopa and viscous glucose endow the hydrogel with high adhesiveness for skin and device interface (including humid and dry environments) and exhibit an outstanding temperature tolerance under extreme wide temperature spectrum (-35 to 65 °C) or long-lasting moisture retention (60 days). Furthermore, this PAA-Dopa-Zr4+ can be assembled as a flexible strain-sensitive sensor to detect human motions based on specific mechanical properties requirements. This work, enabling superior adhesive and temperature tolerance performance and broad mechanical tenability, presents a new paradigm for numerous applications to wearable sensing and personalized healthcare monitoring.

Solvent Quality and Aggregation State of Asphaltenes on Interfacial Mechanics and Jamming Behavior at the Oil/Water Interface.

The formation of highly stable water-in-oil emulsions results in complications in both upstream and downstream processing. Emulsion stability in these systems has been connected to the adsorption of surface-active asphaltenes that are assumed to form a rigidified film at the oil/water (o/w) interface. Full characterization of this behavior is needed to allow for engineered solutions for enhanced oil recovery. Interfacial properties, such as surface pressure and interfacial elasticity, are implicated in the stabilizing mechanism for these observed films. Asphaltenes are known to be interfacially active in both good solvents (aromatics) and poor solvents (high ratio of aliphatic to aromatic). However, due to inherent complexities present in asphaltene studies, the details of the mechanical properties of the interface remain poorly understood. Despite the widely accepted perception that asphaltenes form persistent rigid films at fluid-fluid interfaces, the connection between bulk solution properties and interfacial mechanics has not been resolved. Here, the effects of solvent quality on the interfacial properties of asphaltene dispersions are determined by using a well-defined asphaltene/solvent system. Interfacial rigidity is observed only under poor solvent conditions, while the good solvent system remains fluid-like. The interfacial rheology under good and poor solvent conditions is measured simultaneously with surface pressure measurements to track interfacial development. It is shown that surface pressure and dilatational modulus measurements are not indicators of whether an interface demonstrates rigid behavior under large compressions. Finally, conditions required for asphaltene-coated interfaces to exhibit the mechanical behavior associated with a rigidified interface are defined. This work provides a framework for quantifying the impact of the aggregation state of asphaltenes on the stability and mechanics at the o/w interface.

Protein phase separation disorder as a potentially pervasive pathogenic mechanism of male infertility

Male infertility is a complicated pathological state with high genetic susceptibility. Genetic defects and gene mutations may affect the structure and function of key molecules associated with fertility, and then clinically manifest as azoospermia, teratospermia, oligozoospermia, or asthenozoospermia. Most of the current research mainly focuses on the infertility phenotype and downstream pathways and clarifies the relevant mechanism by using molecular biology methods to construct knockout or overexpression models combined with omics and experimental verification, but how the mutation itself affects biomacromolecular functions remains poorly understood. As a special state of intracellular aggregation of biological macromolecules, phase separation (PS) is closely related to many important basic life activities. It has been reported to participate in the occurrence and development of various diseases, including neurodegenerative diseases, cardiovascular diseases and tumors, but only a few reports addressed the potential impact of protein PS on fertility. Given the physiological characteristics of PS, we hypothesize that abnormal PS may be a common pathological regulatory mechanism of male infertility, especially spermatogenesis and maturation disorders. PS can affect spermatogenesis and maturation by interfering with the phase transition of key molecules or molecular clusters, leading to gamete loss or dysfunction. Targeted modulation of PS may be a potentially powerful means to improve male fertility.

Development of smart window with hydroxypropyl cellulose-acrylamide hydrogel: Effect of hydroxypropyl cellulose molecular weight on light scattering property

Reduction in the use of cooling systems can help in the reduction of CO2 emissions. Sunlight, particularly near-infrared light, entering through windows causes an increase in room temperature; therefore, a heat-shielding material that can automatically control the amount of sunlight without the use of electricity is required. Hydroxypropyl cellulose (HPC), a temperature-responsive polymer with a lower critical solution temperature (LCST), changes its optical properties in response to external temperature. This study aimed to prepare hydrogels with acrylamide (AAm) and HPC (HPC/AAm gel) and investigate the effect of HPC with different molecular weights on light transmittance and the state of HPC aggregation in hydrogels. The scattering mechanisms were discussed further. The solar transmittance of HPC/AAm gels below LCST exceeded 80%. Above LCST, the solar transmittance of HPC/AAm gels with large molecular weights decreased to 25%, whereas that with small molecular weight decreased to approximately 20%. The surface of HPC/AAm gels comprising HPC with large molecular weight exhibited numerous large pores following freeze-drying because the skeleton of the AAm and BIS inhibited the shrinkage of HPC above the LCST. In contrast, HPC/AAm gels comprising HPC with small molecular weight have a small number of pores owing to the easy shrinkage of HPC; they scatter sunlight by increasing the frequency of light collisions. Thus, the light transmittance decreases when using the HPC/AAm gels with small molecular weight.

An LF-NMR homogeneous immunoassay for Vibrio parahaemolyticus based on superparamagnetic 2D nanomaterials

In this work, a sensitive low field nuclear magnetic resonance (LF-NMR) homogeneous immunoassay, also called magnetic resonance switch (MRSw) sensor, for Vibrio parahaemolyticus (VP) was developed. Superparamagnetic 2D nanomaterial was designed and used as the magnetic probe of MRSw sensor. It was GO@SPIONs&Ab, a composite nanomaterial with many superparamagnetic Fe3O4 nanoparticles (SPIONs) providing a magnetic signal and VP antibody (Ab) specifically recognizing the target VP evenly distributed on the surface of GO. The presence of VP controllably changed the aggregation state of the probe, eliminating the uncertainty of MRSw sensor type, and thus then achieving a regular variation of transverse relaxation time T2 and ensuing quantitative detection of VP. Triple signal enhancement of the MRSw sensor was obtained due to the application of the designed 2D probe, by increasing the number of SPIONs, improving the magnetic intensity and susceptibility, and forming a synergistic effect. Under optimized experimental conditions, VP could be detected with satisfied sensitivity, selectivity, precision, accuracy, and stability, even in turbid real samples. LOQ for VP was 10 CFU/mL. This detection principle is widely applicable, providing an idea for the construction of highly sensitive MRSw sensors.

Kinetics of dissolution and Transglutaminase (TGase)-catalyzed polymerization of soy proteins from the soy meal suspension

It is important to understand the kinetics of dissolution and transglutaminase(TGase)-catalyzed polymerization process of soy proteins from the soy meal either for their extraction or utilization in the food industry. Nevertheless, it is yet still unknown that how the specie concentration, degree of denaturation, subunit composition, and aggregation state evolve with kinetics time (t). This work combines ultraviolet–visible spectroscopy (UV–vis), Fourier infrared transform spectrum (FTIR), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and size exclusion chromatography (SEC) to explore the above questions by using the soy proteins from the defatted soy meal as the model system. Our main findings include: 1) under the condition of soy meal with varied mass fraction/solid content (wtsoy meal% = 5%, 10%, 15%, and 20%) in pure water and buffer with pH = 6.4 at T = 25 °C, the dual exponential equation is found to illustrate the dissolution kinetics which is contributed by two different dissolution modes, i.e., C = − B1e−k1t − B2e−k2t + B1+ B2, where B1 and B2 denote the final concentration of protein, and k1 and k2 represent the dissolution rate for each dissolution mode, respectively; 2) the analysis of the secondary structure of soy proteins shows that the proteins keep undenatured state during the dissolution process; 3) the analysis of relative content of different subunits indicates that the relative concentration of 7S and 11S is almost constant during the dissolution process; 4) SEC results unambiguously support that the dissolution species at most of time are composed of protein aggregates with different sizes; 5) a semi-empirical equation is proposed to well describe the TGase-catalyzed polymerization kinetics, i.e., dnp/dtp = 0.5wtsoy meal%0.8±0.1wtTGase%1.5±0.1, where dnp/dtp is the generation ratio of insoluble protein particle, and wtTGase% is the concentration of TGase. We believe that the knowledge from present study is beneficial for the optimization of extraction and polymerization processes in real applications.